Century, plus 10, and camber question

I’m currently planning my next Century ride for sometime in the next couple of weeks, and will be doing an extra 10 miles to “double my age”. I have a question for the combined wisdom of the forums, having to do with road camber. This time I’ll be doing the entire ride in O.C., starting and ending at the Water tower house in Sunset beach.

About 80 miles of it (40 in, 40 out) will be ridden on the well known Santa Ana River trail, and there is considerable camber in both directions. My question is, since I’ll be riding 40 miles in both directions, would it be a good idea to shim my wheel to counteract the camber? It only takes a few minutes to do this, and then I could just switch to the opposite side for the trip back.

I thought this might be a great idea so I wouldn’t be fighting the lean caused by the camber of the road, which is pretty consistent for the whole was on the SART. The wheel is currently dished and trued and rides perfectly on level ground.

The other thing I would like do do, is to invite anyone who might be interested in riding some of the distance with me. I haven;t decided in the date yet, but it will most likely be on a Sunday, possibly the 1/23 or 1/30/11. Feel free to PM me if you might want to ride along!

I will again be riding for Charity, this time for the fight against Leukemia, and will be dedicating the ride to my brother Gary, who is fighting the disease.

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I don’t think it’ll help much. The problem with camber is the tire contact with the road surface forcing your tire to the side; shimming your frame won’t change that at all.

But by shimming the frame, the wheel would be titled more in one direction. My theory being, that if your wheel was titled in one direction, either by dishing or shimming, that when riding on level ground, it would be like riding in a cambered surface and you would be fighting a pull to one direction.

So if that’s true, I would think that by intentionally producing a cambered effect that would make you lean to the right, on level ground, that it would counteract the pull you would get riding on a left leaning cambered surface.


Why not do a test run with your shim in place and see how it goes. Possibly a 3 to 5 mile test would give you a feel for it?

Good point! I was just talking with a tech from Twins Bile shop; they know my unicycles now better than I do, haha! I explained what I wanted to do, and if he thought it might help and he thinks it could very well counteract a cambered road issue. But he also suggested that I experiment with it and see if it works well enough to warrant doing it. I’ll be trying this theory out in the next few days, and will report my findings on this thread. :slight_smile:

PS: I know this is very exaggerated, but wouldn’t a wheel that’s been shimmed and tilted to such an extreme degree cause a definite pull to one side? And if you then rode it on an equally opposite cambered road, it would counteract that camber?

What would your bike mechanic say re: bearing strain if this is done? Not that it wouldn’t last a 100 miles.

Haha, like I said, that pic was an exaggeration. For me, I can feel a pull if my wheel is dished only slightly off center, so I know it wouldn’t take much to feel a pull; maybe something more like this, which still might be more than I need:

As for pressure on the bearing(s), fighting steep-ish road camber also puts a strain on one side of the uni, including the bearing, as you fight the pull of the camber by trying to stay upright and level.


No, by shimming the frame, the frame will be tilted more in one direction. The wheel contact with the ground will be the same, because your center of gravity has to be more or less the same to keep the uni upright.

Is there any way to counteract road camber, other than just fighting it for 80 miles? Would reducing psi a bit allow the tire to spread out a bit more and make the contact more ground, essentially “molding” the contact surface of the tire more in the direction of your leaning, helping to lessen the pull?

I don’t have alot of uni experience, but I do have 2 unicycles - 1 with a 4 1/4" tire, and 1 with a 2.6" tire. The wider tire always pulls very hard uphill when riding across a sloping surface. When I got the narrower tire, I expected it to do the same, but it didn’t. In fact, it hardly pulls at all.
Therefore I think having more surface area on the ground might actually be MORE of a hinderance. I would try putting more pressure in the tire - then not only would you be reducing the surface area contacting the road, but correcting for it would be easier as well (not to mention reducing the rolling friction for the long ride)

I think the problem comes from the angle the tire contacts the pavement. Since gravity is always straight down, the comparison between a shimmed wheel on level ground is not the same as a straight wheel on a cambered road. However, I still suspect shimming the wheel would help, because it could help the tire to contact the road at a more perpendicular angle. (you would need one slightly longer leg though - or perhaps an insole in one shoe :slight_smile: )

Yeah, pick another route.

The biggest factor is tire cross-section. For some tires, adding more air makes them better, for others, letting air out makes them better. You’d have to check what works for yours.

Generally, the more rounded the tire cross-section, the better it performs on camber. The Surly Endomorph is the worst tire in the world on camber, because it’s basically square. (The Larry is much better).

I don’t think there are any truly good 36" tires.

You might be able to cheat by slightly twisting your seat.

The route is really great since it’s a bike path. very smooth and beautiful scenery along the way. I have gone as far inland as I will this next time, and there will be some considerable climbing as well, but I look forward to that challenge!

As for camber, it’s not as bad as an actual street road, where the camber is very noticeable nearer the curb sides since the road is purposely rounded for water run-off. This bike path has some of that, but I guess I can try riding more towards the center, but since there are TONS of seriously fast road bikers on the SART, that would not be the best place to be! Time to get a rear view mirror! :o

Brent got it right… shimming so that the wheel is perpendicular to the surface/camber should help. You didn’t show the road surface in your sketch. Definitely try it. Over shim if there is enough room in the frame. I know you’ll post the results for us.

I wonder is someone were to ride only on the right side of a camber and the tire wore heavily on the left side if this effect would get worse?

I have tried this and it does help for cambered roads.

I have ridden a roadie with skinny high pressure tires for years, and on a lot of seriously cambered roads. It seems to me that, as mentioned earlier by Tholub, the rounder the tire the better. With a rounder tire and higher pressure I would expect good results. I have no experience (yet) on 36er long rides, but it seems like this would hold true.

I expect the camber of the road sets the direction slightly down the slope. I don’t think tilting the wheel alone compensates for that. But if you tilt the wheel enough so that the curve of the wheel tends to set the direction slightly up the camber (like in a banked turn) maybe that would compensate. The tilting I’m describing would be the top of the wheel towards the top of the camber.

This is all interesting Terry, great experiment.

Tempting, but I don’t think that’s the point, at least in this thought experiment. And it sounds like a really nice route. Terry seems like the perfect guy to do some research on this question, and put in a generous amount of miles in various configurations! :slight_smile:

3-5 miles would not be enough. Partly I say this based on my first Tahoe circuit experience, where the camber really killed me. What I needed was more experience riding on camber (I mostly train on bike paths). Practice riding on camber.

Nope, wrong way. If riding on the right side of a cambered road, the unicycle wants to go to the right. You have to twist left to go straight. So for shim testing, tilt the wheel toward the center of the camber like you were probably already thinking. And don’t do it small, put a good angle on there so you can tell if there’s a difference. Try it going both ways.

Then try twisting the seat. This is what I used for my second Tahoe ride (the one I finished). I’ve also used it for track racing, again twisting the seat to the left because so much of the track is a curve, especially on 200-meter indoor tracks. Try the twisted seat separately from the shimming, and together.

Then play with tire pressure. I think I agree with all the tire advice above. Unfortunately most of it doesn’t apply to the “better” 36" tires. Those are the TA (which has other names) or the Nimbus Nightrider. I don’t know anything about Coker’s “Coker” tire, the one that uses the word Coker as its tread pattern. I don’t recall reading about anyone who’s used one. The Coker Button tire, which is the lightest of those available, also gets very sensitive to camber once it wears down. I think this is because wear on the center buttons makes the tire more square, which may make it worse than the other 36" tires on camber.

My first Tahoe ride was on a worn Coker Button. Second time was on the TA. The TA and the Nightrider are both squarish, which leaves the question of which is better for riding them on camber. Please try it with both high and low pressure. We would like to know!

That’s my experience.

The bike path I ride on follows the American River, so it is usually cambered toward the river. If you ride both ways, you get both directions of tilt. But it’s a pretty flat trail overall. The roads around Lake Tahoe have real camber. Why not come up in June and do a Century ride with us? Or just the 72 around the lake, which is still plenty. :slight_smile:

From what Nathan and Beau tell me, the best way to get good at riding on camber is to ride on camber. If you do a bunch of miles on regular roads with regular camber, it should help prepare you for the less-cambered route of your 110-mile ride.

exactly what I was thinking, and it’s less work, couldn’t hurt to try.

No mechanical device will affect the direction in which gravity pulls.