Off road tires
In many instances normal mountain bike tires work fairly well for winter riding.
Trail riding (often following snowmobile tracks) can be done with normal tires if you let some air out so that you are running at the lowest pressure you can get by with. For normal tires, this might be pressures down to 15 pounds, plus or minus a few depending on terrain and your weight.
It is possible with wider rims to get down to 5 to 10 PSI at these low pressures, keeping the tire on the rim can be problematic. The tire wants to slip around the rim when riding, which can sheer valve stems.
Many riders use a light rubber based glue on the bead to hold it in place. All Weather Sports reports that “based on observation of when and where tires at low pressure move on the rims, it’s not because of braking. It’s not from driving forces either. But they do move. And sometimes a lot in a short ride. Rubber cement hasn’t proven itself strong or reliable enough that I’d recommend it anymore. We use 3M Fast Tack for all commercial work.” (these guys supply wheels and tires to many Iditasport racers).
Given a choice, go for the most open tread you can find, one with widely spaced lugs with sloped sides. Small closely spaced lugs or square cut lugs do not shed snow as well as open design. Those tires recommended for soft dirt work well in semi packed snow such as found on trails or snowmobile routes.
This picture shows an old Specialized with rounded lugs. Where the knobs attach to the tire they are joined by a small radiuses transition. There are no real tight spaces between the lugs.
This tire did not tend to pick up snow, and the tread did not fill in with compacted little snow balls. It is a fairly soft tire and works well on moderately packed snow such as snow mobile trails and wind packed lakes.
Note: This tire, like many others these days, has a preferred “direction of rotation” that should be observed when mounting. Those big transverse ridges as seen on the lug in the center should face rearward when they are in contact with the snow for the back wheel and the ridge should face forward when in contact on the front wheel. This tire is pictured as it would look from the top if the direction of travel was to the right and the tire was correctly mounted on the front wheel (not all tires are directional).
The second is a Richie tire has tighter lugs with square cut bottoms. This tire is in very new condition, and it has been retired from my icebike because these smaller, tighter spaced lugs tended to fill with snow when the tire was run at low pressures.
Its a great dirt tire, but snow is more exacting. Climbing a slight incline, it was easy to spin this tire out. It also threw a bigger rooster tail of snow, which indicated lots of snow was sticking to it.
Now, before you go out and trash your existing tires, let me say that these differences in tread are not show stoppers, and your existing tires may work just fine in off road conditions. Take them out and try them.
If you find yourself slipping or spinning out a lot, consider new tires, but some tires will surprise you with how well they work, such as the Continental road tires below. Several icebikers report good results with some of the Ritchey line, so don’t take my criticism of the above tire as a general condemnation of this company.
Note: Your normal rims will work ok, as long as you don’t let too much air out of the tire, say not less than 12-15 PSI.
For serious off road snow riding, extra wide rims and very low pressure tires are called for. The best of these is the SnowCat rim. This rim is VERY wide, nearly twice as wide as a normal rim, and not all bikes can accommodate it and not all tires will fit it. But when you find the right combination you will have a very wide low pressure tire that can float over slightly compacted snow, opening large areas to winter off road cycling.
These tires were more than up to the task. My confidence grew as the ride progressed. What’s more, they work well enough on the road as well. Ritchey know’s what they are doing.
On road tires
On road riding, such commuting, can be done for the most part on regular tires, although some work better than others. The real knobby dirt tires are not always the best for this. Often tires with an inverted tread pattern work better all around.
They supply less rolling resistance when on gravel, ice, or pavement, and are reasonably competent in light snow. By reducing tire pressure they supply surprising traction on ice too.
At right is my personal favorite, the Continental Town and Country, which is available in Europe in a couple of widths, but usually only imported into the US in the widest width.
This tire performs well on icy roads giving good traction in all but the slickest conditions. Why this is so, is unclear, but I have a garage wall full of knobbies that I don’t use on the road anymore because the T&C is a do-it-all sort of tire. It even does ok off road, although its profile is too round for really soft stuff. Note the rounded bottoms of the sipes (cut out parts) that improve snow shedding.
If there is any snow cover at all, or if the sand-truck typically covers your route before you do, this may be the only tire you need (note that a light covering of loose snow gives more traction than hardpacked snow or ice).
At about $25 each, they are not cheap, but I have never had one wear out despite over 4 years of year round use. This is not to say that this is the only tire that will do. There are other inverted tread tires, and even knobbies that perform very well on the road.
If much of your winter riding will be on frozen lakes or ice glazed roads you can have serious problems of traction. In addition, falls on these surfaces can be less than enjoyable, unlike trail riding where you often will fall onto a layer of snow. A good studded bicycle tire may be the answer.
There are at least two commercial brands of studded bike tires available. In addition, there are plans available for manufacturing your own, which can be cheaper and allows you to adjust the studs for your conditions.
Typically you do not need or want to run your studded tires all winter. For normal road use they are noisy and have increased rolling resistance. You can swap tires on and off as needed, but this is a time consuming task.
Far easier is to have a spare set of wheels which can be quickly mounted on those days you need the extra traction. A set of wheels can cost about 200 dollars, more or less depending on the free-hub/wheel that you have.
Your rear wheel should be an exact match for your normal wheel or shifting problems will be the likely result. If you have the same rims on both sets of wheels, you will not have to adjust brakes every time you change wheels.
To avoid these complications, having a separate bike reserved for truly icy conditions can be cost justified with only a minor amount of self delusion and convenient rationalization.
Commercial studded bike tires
Probably the best (and most costly) available are the Nokian brand. These are available at several of the suppliers listed on our commercial pages. They are made in Finland, and some versions bear the name Nokia instead of Nokian (“NO Kee Ahn”).
These tires come in a variety of styles, and usually the number of studs is indicated by the stock number. Hence the “W296 Extreme” top of the line (pictured at right) has 296 studs. This tire is designed for serious off road use and is good in snow as well as on ice. Its cornering abilities are highly praised. The studs are very hard tungsten carbide, however, and these give good wear. Some users report 4 or 5 seasons of constant use.
These are fairly spendy tires ranging from about $100 to $130 (U.S. Dollars).
As of 2001, Nokian has come out with a new tire that is lighter than the 296, and has a new stud design that also reduces weight.
The Hakkapeliitta WXC 300 (No, I can’t pronounce it either). The rubber lugs are an abbreviated version of those found on the W296, saveing a little rubber and a lot of weight.
The tire has 300 studs that have an aluminum retainer and a tungsten carbide center “gripper” (for an quick view of how studs are constructed take a look at the photo below).
This tire may surpass the W296 in the future as the high end tire in the Nokian line.
Previously, all Nokian retainers have been steel. The new stud grippers are also covered with aluminium (aluminum probably makes manufacturing easier) which is expected to wear off in the first 50 miles of so of road riding, exposing the tungsten carbide gripper. If these grippers are anything like past Nokian studs, that’s when the wear stops.
The aluminum retainers reduce weight some, but most of the tire weight reduction comes from the lighter casing. The lighter weight, 695 grams vs. 895 for the W296 will be welcome as studded tires tend to be rather heavy.
The tire is designed to handle 43 PSI, which means on road use can take advantage of lower rolling resistance of a firm tire, while off road performance can be enhanced by reducing pressure.
An independent review by Dave McElwaine, who supplied the two photos above is available here.
Nokian has other grades of studded tires. The W288 Mount and Ground, pictured at right is a good mixed-use tire, suitable for roads and trails. It has a 8 fewer studs than the extreme, and a less aggressive tread pattern. This tire comes in two versions, 288 studs, and 144 studs (my advice: more is better).
Nokian has discontinued the 288 stud version of this tire (you may still find some in stores). They have substituted a 160 stud version. Their web site does not make it clear whether the 144 stud version will still be available. The 160 version has the lugs spaced slightly farther apart leaving a more open design.
Probably somewhat less capable in deep snow, this tire still delivers plenty of traction in rutted ice/snow where pre-existing tracks have been iced over and refrozen.
It can be found for as low as $75 if you shop around.
I have personally ridden this tire in heavy wet snow and light powder and felt it handled very well. It sheds snow quite well, you never see the “white tire” syndrome. On ice, its like being on rails!
Finally, Nokian makes a slightly narrower tire; the Hakkapeliitta W106. It comes in sizes as narrow as 37mm and is available for 622 as well as 559 size wheels (700Cx37 and 26×1,9 for those not yet into ETRTO sizing).
This tire is usually available for under $50.
This is a great commuting tire. It has two rows of studs and a good low-rolling resistance tread pattern. This is just the ticket for those unexpected patches of black ice on roads and trails. It will handle modest snow depth quite well.
In addition, Nokian makes a wide range of specialty winter tires in a variety of sizes. See their web site at the link above.
Nashbar Studded Tires
Nashbar has had studded tires for the last few years. In years past these have had problems with studs falling out, and accelerated stud wear.
Beginning in 2003, Nashbar has worked with Kenda to produce a better grade of winter tires under the Nashbar Label. These tires are available in two sizes (as of this writing), 26×1.95 and 700cx35.
The tires have nice large lugs, and an open tread pattern which should shed snow fairly well while providing good traction. The studs are of a more flat-topped design than used by Nokian tires.
The 26 inch MTB tires (50-550) have 4 rows of studs, two inner rows of 70 each and one outer row on each side of 14, for a total of 168. They are rated at 40 to 65 PSI, but even at 40 PSI they may be too hard for soft snow riding (little or no sidewall flex at that pressure), and you may want to run these tires at around 20-30 PSI, depending on your rims.
There is an unstudded center ridge, which is useful for dry road riding. Simply inflating to maximum pressure should (depending on total weight) keep most of your studs out of contact with the road except when cornering. Lowering the pressure a bit will bring the two main rows of studs in solid contact at all times.
Stud seating depth is good, leaving significant stud above the rubber. Compare that to the largely ineffective IRC tires below.
In addition to MTB tire, the Nashbar line includes a tire for cross-bikes. This tire bears three size notations (700cx35c, 28×1-5/8, 36×622). This tire is designed as a commuting tire for urban areas. This tire is rated for 50-85 PSI, and has 90 studs.
This design is slightly more open than the Nokian 106, and slightly deeper lugged. The studs appear to be the same type and seated identically to the 26 inch tire.
Reports form Nashbar indicate that both models are selling fast. The price (under $30 US as of this writing) is very reasonable, and the quality appears to be quite acceptable. Kenda has a good reputation for bicycle tires. Nashbar representatives said they did not design this tire for the Iditasport, but for practical winter cycling on icy snowy streets and trails.
The IRC Blizzard tire has been around for some time It is less expensive than the Nokian, and less effective. Shown at right is the reason for this.
The IRC studs are too few, and set too low. There are only 56 studs. There is hardly any road contact. I found very little benefit to this tire over the T&C tire mentioned above. These aren’t bad snow tires, they have a fairly open pattern and somewhat radiused lugs, but as ice tires they just don’t cut it.
Note that all stud holes are not filled. This is the way it comes. It is sort of skip-studded, in every other hole.
I tried to have a commercial tire shop add studs, they had none short enough. It could be that Nokian replacement studs could be used to improve this tire. Simon at All Weather Sports reports having re-studded an IRC Blizzard with Nokian studs. “Wore holes in my hands; I’ll never volunteer for the chore again. But it was simple and it works.” At retail prices for the studs, it would be a questionable project.
This should have been the case all along. Note there are still no studs on the edges. These are needed for turning.
This tire goes for around $55.
A late arrival on the marked is the Innova tire, which is quite inexpensive, about CDN $32 in Canada. There are some concerns about the durability of this tire, but for that price you could almost afford a new pair each year.
It is an oriental import, and the actual manufacturer is not known, and the supplier (MEC) is not saying.
Its a fairly narrow tire designed to compete with the Nokian W106 (above). The exact number of studs is unkown.
Home Made Studded Tires
You can manufacture a studded bike tire for far less than you can buy one. This usually involves installing screws through the casing, from the inside. This usually necessitates a tire liner (perhaps just a extra dead tube) to prevent damage from screws that back out, or abrasion from screw heads.
Home made studs are usually heavy, and prone to flats. However, most serious bike riders have the necessary spare knobbies laying around and with a few cheap materials you can have a lot of fun out on the lake.
Brian Buehner had a page where he gives detailed instruction for some SERIOUS off road tires. These are designed to prevent sheet metal screws (studs) from backing out.
The following method is recommended by the Edmonton Bicycle Commuters Society.
This is what you need to make your very own studded tire:
- One tire. You need a tire with knobs big enough to support the stud. the stud as explained further down, has to be on the
- 50 (approx.) Robertson head #8 by 1/2″ sheet metal screws (the square head, you’ll thank me for this tip) for mountain bike tires (26inch) or #8 by 3/8 inch for hybrid tires (700c)
- Liner for each tire. This can be made by cutting the beads off an old tire, cutting out the valve and slitting along the inside of an inner tube or just buying a Mr. Tuffy tire liner.
- Baby powder.
- One sharp awl. (or a 1/8″ drill bit)
- Count the knobs and evenly spread out the 25 screws for each side.
- Punch holes, from the outside of the tire, into the designated knobs. You can drill the hole, however, drilling tends to tear the fabric and thus weakens the tire. Caution you don’t need a million screws in there! Too many screws just slows you down.
- Use Robertson bit in the drill to drive the screws in the tire from the inside.
- Put liner inside tire and make sure it covers the screw heads
- Put a generous dusting of baby powder between the liner and the tube.
- Mount tire on the rim (ouch! watch out for the points!)
- Inflate to maximum pressure. Put the wheel on the bike (mind the points). Spin the wheel to make sure that the studs don’t catch on anything.
You only need to stud the front tire to keep upright; however, if you stud the back tire as well, it’s even better. One caveat is that these tires are only suitable for winter conditions.
The difference between one studded front and no studded tires in phenomenal. When the bike is travelling straight the studs shouldn’t be hitting the road too hard; otherwise, they will just wear out too soon. Don’t worry, when the tire slips just a bit the studs will bite in. You rarely notice the slight side to side movement.
You don’t need to stud the middle knobs since you only need the added traction when you are turning. The studs should touch the road enough to allow sufficient braking. The studs in the middle knobs wear out very fast and soon become useless anyway.
Stainless steel screws will last much longer, but also cost about 3 times as much. You can change screws as they wear out, your tire can survive several sets of studs.
Are All Studs Created Equal?
As arranged on the Icebike mailing list, I volunteered to perform hardness tests on a few studs from winter bicycling tires. Several others agreed to send samples of studs and shortly I received studs from 3 different studded tires: Nokian, IRC, and Nashbar, to measure their hardness.
At last I have the stud hardness test results! The following is my report.
A little background first
In a hardness test, a small indenter (in this case made of diamond) is pressed into the surface of a metal sample with a known force. The result is a small impression, and the size of the impression is an indication of hardness. The smaller the impression, the harder the material.
The term “Hardness” is really a measure of the ability of a sample to resist indentation, and in itself it is meaningless, and only becomes useful when compared to the hardness of something else. There is a definite relation between hardness and strength and wear resistance. Harder materials are stronger and more wear resistant.
To measure the hardness, the sample must be properly prepared. Standard metallographic technique is to embed the sample in a plastic “mount” which allows the technician to hold the sample in proper alignment for preparation. In this case, the studs were laid on their side in the mount. The face of the mount was ground down, and in the process the studs themselves were partially ground away.
In this case, we ground the mount until about half the studs were ground away, revealing a cross-section through the stud centerline. This surface is then polished to a mirror smooth finish, since the hardness impressions are microscopic and surface imperfections could affect the result, thus the need for a flat smooth surface.
Here is an image of the prepared mount with the ground and polished studs showing their cross sections.
It can be seen that the studs have a “T” shape cross section. There is a head at one end (like a nail head), a body, and a tapered end, which is the “business” end of the stud that makes contact with the ground.
Now the results
It is immediately obvious that the Nokian and IRC studs are made from two pieces: the stud body which is steel, and an insert brazed into the center of the stud. It is the brazed insert that is in contact with the ground, and the body is simply a holder. The Nashbar stud is a single piece of steel.
The Nokian insert had a hardness of 1700 KN (Knoop hardness scale). The IRC insert had a hardness of 1400 KN. The Nashbar had a hardness of 350 KN (corresponding to about 57 HRC for those who care about such things).
The Nashbar stud is by visual examination and hardness testing, simply hardened steel. It was harder on the surface than in the center, which implies a low alloy and/or low carbon steel (ie: less expensive steel), as something this small should harden throughout its thickness when heat treated – there should be no hardness gradient.
I made no attempt to identify the composition of the IRC or Nokian inserts (that would have been a bit expensive), but my best guess is they are “carbide”, a very hard, wear resistant material commonly used for high wear applications like metal working tools, saw blade edges, and so on.
A word of caution: Don’t try to attach a “value” to the relative hardness of the studs. The Nokian is not “5 times better than the Nashbar” nor will it “last 5 times longer”. All that can be said is that the Nokian and IRC are “substantially harder and will be much more wear resistant” than the Nashbar.
As a metallurgist, and knowing the environment these tires run in, I would be very surprised to see significant wear on a Nokian or IRC stud, whereas on road surfaces, I would expect wear on the Nashbar. Running on dirt or ice the Nashbar may hold up much longer.
On a personal note, I am impressed with the degree of technology exhibited by the Nokian and IRC tires. There is considerably more cost involved in preparing the stud to receive the insert, and then going through the brazing process, compared to the Nashbar stud which is simply machined and then heat treated. I can understand why the Nokian tire is so expensive!
Background reading: Microhardness Testing
By Bill Dobson
In addition to studded tires for supplying winter traction there are also bike tire chains and bike tire wires.
These usually attach to the tires, while avoiding the bike rims so as not to interfere with the brakes. The chains cross the tread providing traction in deep snow and ice. The wire variety usually holds chunks of metal with teeth positioned over the tread.
These of course provide a bumpy and noisy ride on pavement, compared to studded tires, which themselves are noisy enough.
However, some claim that bike chains provide better traction than studs in thick snow and that brown compacted but un-consolidated squirming mass that forms when cars drive over new snow but it is too warm for it to freeze to the ground. (Also known as brown sugar, chocolate mousse, car snot, etc.)
When on really snowy roads, you may not notice the bumpy ride caused by the devices.
Tire chains for bikes are far more lightly constructed than those for cars. They also have the attendant problem that the tire rims must not be obstructed because that would interfere with the brake pads. This later restriction does not apply to coaster brake bikes or bikes with disk brakes.
Therefore, the chain system is rather tenuously secured on the outer half inch of tire tread.
These can come off in sudden turns where there is good traction, so they must be installed tightly.
The normal way to achieve the degree of tightness that is required is to deflate the tire somewhat, install the chains, then re-inflate the tire so that the chains are held securely. This of course means that if you intend to do this on the road you have to have a pump.
The model shown here, Quik Klaw Cleats by KoolStop uses a long threaded barrel on one end of the “ladder like” set of wires and cleats and a threaded bolt on the other end.
There is one junction on each side of the tire. These are usually just installed “finger tight” (no tools used) and the the tire inflation is raised to lock them in place. This can be done with out removing the wheel, but you have to carry a pump.
The cleats shown in the model above protrude about a quarter of an inch above the tread. Bikes with brake bridges or tight fitting chainstays may have clearance problems. Not all models have cleats this large, some are simply another metal cord running across the tread.
Cleats tend to be spaced every 6 inches or so, and this produces a very bumpy ride on hard ice or bare roads. So much so that you will want to take them off as soon as possible. Cleat wear can be very rapid if ridden on dry roads.
When you do remove them, they are customarily rolled up and placed in your panniers. The set show make a 6 inch diameter roll, rolling them tighter makes for nasty tangles.
Other than the rough ride there have been other problems reported with these devices. My local bike store owner reported that they sold only two sets last winter (different brands), and had trouble with both of them. One caused a nasty accident when it came loose and seized the front wheel. This is apparently not that rare.
There are several brands and bike shops tend to push what they have (probably because they have had them for years and years and would like to get rid of them). Monitor Traction Devices seem toe be the most widely known. The Quik Klaw Chains at right are also sold by KoolStop.
I also found an interesting hint of another system at that is comprised of hooks, which fit between the rim and tire, wrapping around the tire. When traction is required, a chain is stretched from one hook to the other – across the tire.
Home made chains
It is also possible to make your own tire chains for bike use. Not limited to winter ice and snow, these are also suitable for mud and off road work. While probably inappropriate for public trails over delicate ecosystems, they should work well on semi-frozen snow trails if your bike has the clearance to accommodate them.
What’s best, studded tires or chains
Chains are said to be better on unplowed roads and trails where there may be 6 inches of uncompressed snow below your wheels, some of it trampled and uneven.
Others claim that the newest version of studded tires do better in these situations and are lighter and less problematic.
I don’t have an opinion, as my bikes have clearances that are too tight to accommodate these devices, but here are some postings from Rec.Bicycles.Misc newsgroup courtesy the Danenet Bicycle Commuting Pages that deal with this subject.
Back when I owned no vehicle (insert favorite poor student story here) I commuted year-round by bike. This included the winters from 1987 to 1993. Most of these winters were in the Northern city of Edmonton where we have two seasons: Winter and July ;^)
After a couple of winters on my usual knobbies, I felt there had to be a better solution to traction on ice and snow since I now faced a 24 km round trip to school and back. I contemplated the (at that time) new IRC Blizzard, but it looked like the studs were useless, and at $85/tire (boy, have they ever come down in price) I couldn’t justify the expense.
The store offered me another solution: tire chains. I purchased one for the front tire and decided to try it for awhile before deciding whether one was required for the rear wheel.
Unfortunately, I have no recollection of who the manufacturer was. I can only describe it. It was made out of a very durable metal, roughly the thickness of a wire coat hanger. This wire was bent so that it consisted of about 1″ to 1 1/2″ long links and about the same width. Where each link joined, the loose ends of the wire were allowed to point outward by about 3/8″ at both sides to dig into the snow.
I say the metal was tough, because these protrusions didn’t bend over even after 2 (long) winters of usage (est. 4000 km).
My experience with the tire chain up front was very positive. These babies stuck to the hardpacked snow like you wouldn’t believe! The main drawback was that bare pavement, etc. was to be avoided because traction wasn’t great (and it would probably prematurely wear down/bend the spikes). Also, there was greater rolling resistance.
One distinct advantage to having the chain on the front tire for me was the ability to use the front brake. My rear brake was one of those under the chainstay mounted U-Brakes which were popular in the early 80’s. The front tire flung all sorts of gunk into the brake cable housing where it was routed under the bottom bracket. I rarely ever had a working rear brake!
I only ever recall one wipeout while using the front tire-chain. The rear wheel swung out on me with no warning and I was unable to stop its momentum as it quickly swung about in front of the front wheel. The front tire held its ground and the handlebars were wrenched out of my hands. Eventually something had to give, and I went flying!
Overall, I was quite pleased with the tire chain and never got around to purchasing a rear tire chain. Unfortunately after the second winter, the chain rusted up very badly during the off-season (summer! :^) ). I was never able to find another chain, but I also didn’t look too hard since we had a few milder winters, I lived closer, I had a new bike so rear brake freezing was no longer a factor.
Rims and wheels
The wheels depicted on this page are specialty items, usually used for off road riding, on single track, partially frozen trails, or snowmobile tracks. Most commuters never encounter the need of these rims unless substantial portions of your route are on un-maintained trails.
However, for the recreational icebiker the wide rims described here open up significant new opportunities for exploration and fun in areas you have never ventured, perhaps not even in summer.
Why special rims?
Part of the problem is pounds per square inch (kg per square cm). Riding on semi-frozen snowmobile trails or single track, or crusted-over lakes, you will break through the softer portions, your front wheel will sink, and you may do an Endo. The surface simply can not support the amount of weight you and your bike apply.
At 40 PSI, 200 pounds of bike and rider will we carried on 5 square inches on the bottom of your bike tires. This will be split roughly evenly between the two tires. The trouble is, the snow can not bear 100 pounds on just 2.5 sq. inches. So you sink. You keep on sinking until the amount of tire in contact with the snow spreads the same amount of weight to more and more square inches of snow. Once you have enough inches of tire on (under) the snow, you stop sinking.
More square inches on the ground helps
The other part of the problem is the shape of the tire. In cross section, the mostly rounded shape of the typical bike tire causes it to slip sideways rather than just straight down. Down would be bad enough. Sideways requires steering input at the very least, may cause falls, and is ultimately unmanageable. Snow tends to “squirt” out towards the edges of the tire, rather then being packed down as the tire rolls over it.
A flatter tire cross section helps
Finally, when on really bumpy hardpack, or other uneven surfaces, high pressure tires can tend to follow ridges, (diverting you from your intended course), and bounce, breaking contact with the ground, reducing your traction, and allowing sideways momentum to be built up while the tire is in reduced contact with the ground. Softer tires tend to roll over small ridges and bumps, absorbing the bumps by deforming, while as the same time maintaining contact with the ground.
Lower tire pressure helps
Each of the above aids to off-road winter cycling has its own place. On rutted ice, lower pressure and a flat cross section are better. Glare ice calls for higher pressure. All three at once would be ideal for many off road situations in winter.
The only way to get all three at the same time is to run wide tires with a flat cross section at low pressure.
The problem is this is virtually impossible with a narrow rim, because if you lower the pressure enough to get a flat cross section you run the risk of snake bite (pinch flats) as the rim will bottom out inside the tire.
Additionally, much of the tires potential width it “consumed” by having the tire form a circle (in cross section). If the tire only had to form half of a circle, it would be a much wider circle. If you have ever spread a bike tire flat (pulling the beads away from each other) you were probably amazed how wide it was.
The Wide Rim Solution
These are exactly the conditions that Snow Cat rims were designed to meet. Designed by Simon Rakower of All Weather Sports in Fairbanks Alaska, the Snow Cat rim is 44mm wide, compared to 22mm or 32mm for normal mountain bike rims.
There are several other companies making wide rims for downhill races. Unlike Snow Cats, these were not designed with winter cycling in mind, and may be heavier. They are, however designed to take a beating and have similar width.
This extra width of wide rims provides for a flatter cross section to any tire mounted. This widens the contact patch, puts more square inches on the ground, meaning you can reduce pressure and still carry the same weight.
Further, with wide rims, the rim edges sits directly above the side wall, or, in some cases, outboard of the tire altogether. This reduces the risk that the your rim will bottom out inside the tire. Instead it will be riding above the sidewall of the tire. Hitting a bump with wide rims is far less likely to cause a pinch flat.
This means you can reduce air pressure even further. Reduced air pressure brings more tire in contact with the snow, as the contact patch is elongated (front to back).
Wide rim spreads tire, flattening it’s profile and positioning rims directly above side wall. Snake bite (pinch flat) is less likely.
With regular rim, tire bulges out from both sides of rim. Hard bumps will drive rim down “inside” tire when run at low pressure. This can cause snake bite.
With more inches in contact with the snow, you are able to spread that same 100 pounds per tire over a greater area. At 10 PSI, the contact patch would be almost 10 square inches per tire. This is well within the load bearing capabilities of some snow surfaces, such as snowmobile trails, and slightly packed areas. With lower pressure, down to 5 PSI you might come close to 20 square inches per tire. Although you can reduce air pressure to as little as 5 PSI with ride rims, most riders maintain closer to 12 PSI as their minimum.
A Brief History of the Snow Cat Rim
I designed the Snow Cat for snow riding but there had been hints of interest in them for downhill racing from the beginning, so I didn’t go ultra-light on the cross section.
That turned out to be a good idea. For a few years DH sales exceeded winter sales. I started doing serious promotion at major DH events about five years ago and spent the next few years watching over my shoulder for the big companies to pick up on the idea and crush me. It took a surprisingly long time.
The bike industry is cash starved and very conservative. DH rim widths crept upward for a few years with Sun, Mavic and a few others watching each other and giving out BS reasons why really wide was a mistake.
Yet, people from the big rim companies would tell me they were glad I was making such wide rims because it took pressure off them to do it. I got lucky when Sun’s first really wide rim (Fat Albert) flopped. It was fun being on the right side of the rumor machine.
My product worked, the big company’s knockoff didn’t, consumer accounts about why it was bad were wild and widespread.
Nokian tire designer Jorma Tikka got interested in DH and came up with the idea of a tire sized to really fit on the Snow Cat.
Nokian took a bigger chance than I’ve seen any other large company do in the bike industry. They made a three inch tire (the Gazzalodi) when there was only one rim and NO BIKES to fit it.
They introduced it at the ’98 Winter X-treme Games. Within a few weeks there were plenty of bikes to fit it. I was swamped with calls from small DH frame builders wanting to know dimensions. The standard changed overnight.
So the little kitty led the DH world onto big rims and big tires. Eventually they got it right and there are now wide rims more suitable for DH than the Snow Cat.
But the monster rolled right past me and I didn’t get crushed. DH rims are very heavy, so the Snow Cat is the lightest of the big rims. Disc brakes are the standard for DH so very few of the wide rims have brake surfaces.
The market isn’t big enough for even one winter rim. I could only get it in production by doing silly, egotistical things with larger lumps of money than I should have. God bless the oil economy.
Rim manufacturers are smarter than I am and don’t seem to want to waste capital on a product with such limited appeal. So they try to do double duty with a DH rim. We’ll see where it all goes but I’m not afraid of competition. I took last winter off; went away and did no marketing and had no product. It would be amazing if no one tried to move into the (small) void.
One more thing I like about Snow Cats: I can drill them in any crazy way anyone wants even, (gasp), dishless rears. I mean really dishless, with identical spoke angles and tensions on both sides.
This is how Charlie Beristain just got his (you can see the offset spoke holes in the side-by-side pictures above). Ritchey may have “invented” OCR but I’d been making 0-dish Snow Cats for years before he did. Standard width rims can correct for dish by a few mm. Only a big flat rim lets you shift the (w)hole pattern the 10 mm needed to completely compensate for eight or nine gears.
Simon Rakower, All Weather Sports
Some riders report less control on glare ice surfaces when riding with real low pressure. This is not a problem caused by wide rims, just one you are not likely to run into until you have wide rims.
When you lower tire pressure, you also lower the amount of pressure on the studs. This is offset by bringing more studs into contact with the ice. However, at some point (around 5 or 7 pounds from all reports) you get so little weight on the studs that they do not dig into the ice at all. They simply skate on top of the ice, providing less traction than rubber tires.
On bare ice, it has been found that studded tires should be run at near their sidewall pressure, but you want to still show some sidewall flex while riding to reduce tire-bounce. Tire bounce can happen by hitting even small bumps with tires inflated quite hard. Normally not a problem in summer, but in winter when the wheel loses contact with the ground it may come down with a slight sideways momentum and slip out from under you.
Additionally, there can be problems getting wide rims to fit on your bike. The front is seldom a problem, but the rear can be too narrow where the chain stays join the bottom bracket, or near the bridge on the seat stays.
In addition, it is hard to build a wheel with a wide rim and not end up with an excessive amount of “dish” in the rear wheel while trying to fit the gear cluster and the wheel inside the chainstays.
Many Snow Cat rims are drilled for off center spoke holes for the back wheel. This allows construction of a wheel with less “dish” than would otherwise be necessary, and provides the needed clearance and centering of the rear wheel.
Note that since these rims are usually used with quite low preasure, the plastic liner is all that is needed to keep the tube from protruding through the holes shown in this shot of the Snow Cal “SL” model These holes save over 600 grams per set of wheels.
There are also problems with getting brakes to work correctly. The rim is so wide that modification of the brake arm mounting and or the brake pads may be necessary. Some brake arms can actually give greater clearance when mounted backwards, as carefull study of the picture below shows. Those brake arms are designed to have that curved portion of the lever faceing the tire. By reversing each lever, more clearance is provided.
For this reason Disk Brakes and wide rims are often found on the same icebike.
Finally, wide rims and studded tired can add as much as 4 pounds to your bike over the weight of your regular rims and tires, especially if you end up using down-hill rims. Much of this weight is attributed to the studded tires. If riding of packed snow, you may not need them.
Wide rims provide all three of the desirable attributes needed for winter snow travel. They still do not provide adequate “flotation” to allow you to ride on top of powder snow or even heavy wet snow. However, snow that has thawed and refrozen, or been rained on is often firm enough to ride with wide rims and the proper tires. Winter snowmobile trails often prove quite navigable with wide rims.
Additionally, in loose snow, wide rims provide a greater measure of control, as the tires tend to wallow less with a flatter profile, and the reduced pressure keeps more tire in contact with the ground, (and more studs in contact with the ice). Handling is greatly improved, as is your speed over the ground. Some snow terrain is simply impossible without wide rims.
If you spend much time off road in winter you will likely sooner or later find your self on wide rims. They are virtually required equipment in some off-road races such as the Alaskan Iditasport, and add greatly to the capabilities of your bike on winter trails.
Photo Credits: Charlie Beristain, John Andersen, and Simon Rakower.