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Old 2018-08-18, 10:39 AM   #1
Scoox
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Tyre profile and effects on steering

I was just wondering what effect of different tyre profiles have on how a unicycle handles. My 19" uni has a Maxxis Creepy Crawler which has a fairly flat profile and it feels very stable. My KH 27.5" has a Kenda Havok Sport which has a very round profile and it is very susceptible to bumps and road camber i.e. if the road is not perfectly flat it likes going off to one side.

What's the word?
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Old 2018-08-18, 11:29 AM   #2
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Looking at different tyres, it seems that the square profile is achieved by having taller knobbles on the sides which adds weight. Maybe on a 19" tyre not such a bit deal but on a 27.5" that might be a lot of extra material, which is why I'm not finding any such tires. I'll try running a lower pressure.
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Old 2018-08-18, 03:05 PM   #3
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Discussions about camber seem to be all over the place, due to the incredible number of variables at play among different riders' experiences.

My suggestion is: learn to ride on camber on a round profile tire and/or a tire pumped up to high pressure. Decrease the contact patch. Now, go ride on a cambered surface and suffer.

Or, screw that... you can ride on camber with lower pressure and/or a more square profile and succeed.

In the former case, suffering leads to improvement, as the rider is forced to adapt their technique to the camber, whereas in the latter case, success doesn't necessarily cause any improvements in technique, because the rider was relying on a quality of the tire to keep them riding straight on a cambered surface.

If you're struggling with camber, I suggest rather than going on long rides on cambered surfaces, you rather ride short sections of extremely cambered surfaces, and you ride them both ways (so the camber is alternately to the left, then the right). This way, you will gather more clues about how to handle camber. Good luck!
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Old 2018-08-19, 02:13 AM   #4
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Quote:
Originally Posted by elpuebloUNIdo View Post
Discussions about camber seem to be all over the place, due to the incredible number of variables at play among different riders' experiences.

My suggestion is: learn to ride on camber on a round profile tire and/or a tire pumped up to high pressure. Decrease the contact patch. Now, go ride on a cambered surface and suffer.

Or, screw that... you can ride on camber with lower pressure and/or a more square profile and succeed.

In the former case, suffering leads to improvement, as the rider is forced to adapt their technique to the camber, whereas in the latter case, success doesn't necessarily cause any improvements in technique, because the rider was relying on a quality of the tire to keep them riding straight on a cambered surface.

If you're struggling with camber, I suggest rather than going on long rides on cambered surfaces, you rather ride short sections of extremely cambered surfaces, and you ride them both ways (so the camber is alternately to the left, then the right). This way, you will gather more clues about how to handle camber. Good luck!
You are probably right there, though road camber is so annoying, it's like trying to bite into a nice burger and the burger running away from you.

At 3" wide the Kenda Havok tyre might be a little too wide for urban riding, compared to the Creepy Crawler at 2.7" which is already very wide. The wider tyre is likely to amplify the problem. Just imagine, if the tyre was a big 27.5" diameter rubber ball with an axle through it, you'd essentially have a range of tyre radii from a few mm (theoretically 0 mm) to 27.5" depending on tilt. The opposite scenario would be an infinitely thin torus which would only have a single diameter—27.5"—regardless of tilt and hence road camber would have no effect at all. So I might try a thinner tyre instead.
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Old 2018-08-19, 09:47 AM   #5
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Time in the saddle, weight on the saddle and ahead of the wheel, that will help a lot. Handlebars too. Some tires are indeed more prone to camber.
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Old 2018-08-19, 11:45 AM   #6
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Time in the saddle, weight on the saddle and ahead of the wheel, that will help a lot. Handlebars too. Some tires are indeed more prone to camber.
Today I've spent 30 minutes on a bit of road that has a very pronounced camber, I found pushing harder on one of the pedals (depending on which way the camber goes) gets me going straight. Before I was trying to compensate with my thighs which was not as comfortable. I also slightly reduced tyre pressure a few psi which seems to have helped a bit.
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Old 2018-08-21, 06:11 AM   #7
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In my opinion most MTB tires cause auto steer and I find it pretty annoying. It's pretty hard to avoid if you don't know what to avoid. Avoid tires with square profiles and/or tall corner lugs as they tend to auto steer on uneven terrain. I'd look for tires with round profiles that ride well at low PSI. Decreasing tire pressure makes it more forgiving but I've tried all on the list below at high PSI and they don't auto-steer.
Kenda Havok Pro (aggressive tire but good, not great, on boulders.
Schwalbe Nobby Nic (excellent muni tire)
Specialized Purgatory Grid (good but a bit too soft)
Surly Knard (excellent XC tire for roads and gravel)
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Old 2018-08-22, 04:46 PM   #8
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Originally Posted by rrurban View Post
In my opinion most MTB tires cause auto steer and I find it pretty annoying. It's pretty hard to avoid if you don't know what to avoid. Avoid tires with square profiles and/or tall corner lugs as they tend to auto steer on uneven terrain. I'd look for tires with round profiles that ride well at low PSI. Decreasing tire pressure makes it more forgiving but I've tried all on the list below at high PSI and they don't auto-steer.
Kenda Havok Pro (aggressive tire but good, not great, on boulders.
Schwalbe Nobby Nic (excellent muni tire)
Specialized Purgatory Grid (good but a bit too soft)
Surly Knard (excellent XC tire for roads and gravel)
Thanks for the tyre recommendations. I'm not sure I agree with the claim that a round profile mitigates auto-steering. Today I had a UPD while riding over a long dip in the road, along the side of it, with the Kenda Havok. Initially the wheel started rolling down (left) into the dip which is intuitive enough, but then, due to the camber effect, the wheel began to turn the other way (right). At that point my body was travelling towards the left and the wheel was determined to go right, and I got thrown off very inelegantly I've ridden that spot several times on my 19" with the Maxxis Creepy Crawler without issues, but it could be a combination of various factors, it's really hard to tell with so little experience. I've tried lowering the pressure but by the time the tyre "flattens out" to achieve a profile that resembles the Creepy Crawler it's so soft it folds over when doing side hops and the ride feels very wobbly.
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Old 2018-08-23, 05:39 PM   #9
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Rode over same spot again today, my wheel self-steered to the right and I UPDed yet again. So I backtracked, went over it again but this time I deliberately started steering left before hitting the dodgy spot, and I cleared it. That was very interesting because it made me realise it was not me being clumsy but the fact that I was not prepared for the obstacle beforehand.

I think my problem is that I'm not experienced enough to anticipate what's going to happen next just by looking at the ground. The way I ride now I'm reacting more to what I feel than what I see, and by the time I start feeling my wheel self-steering it's often too late. I hope over time I'll develop a sense that allows me to react prospectively to visual cues rather than retrospectively to mechanical ones so I can glane at the ground and say: "If the ground looks like X, then Y is going to happen so you'd better do Z".

At the moment I find anything that resembles camber (any sideways gradient) very counter-intuitive because my wheel wants to steer up the slope but intuition tells me things roll down slopes.

It's amazing how much concentration, planning and quick decision-making riding a unicycle entails. It's a brain workout as much as it is a body workout!
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Old 2018-08-23, 09:29 PM   #10
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Quote:
Originally Posted by Scoox View Post
At the moment I find anything that resembles camber (any sideways gradient) very counter-intuitive because my wheel wants to steer up the slope but intuition tells me things roll down slopes.
I've never ridden a tire that headed anywhere but downhill on camber. I mostly ride muni, and all of my tires are big and I always run pretty low pressure.

The usual explanation for the wheel heading uphill is the "cone rolling in a circle" analogy; if the tire has a round profile the uphill side of the tire makes contact higher up its shoulder, which has a smaller diameter than the downhill side. So it's a bit like a cone shape.

I've never heard a clear explanation for the wheel heading downhill, but I expect it's what the car people call "pneumatic trail", the effect that makes your car steering wheel center itself. As you roll across the slope on a soft tire, the contact patch continuously creeps down the slope because of tire deformation. So the front of the contact patch ends up below the back. And the wheel wants to align itself with the contact patch, so the front twists downhill.

And a tire that magically balances the two effects would be immune to camber! At least at that particular pressure, on that particular rim, and slope...

---

As far as adapting to it, you get quicker at automatically compensating; I don't think consciously trying to anticipate the effect and steering the other way is worth it, except maybe as a learning excercise.
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Old 2018-09-26, 12:00 AM   #11
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The usual explanation for the wheel heading uphill is the "cone rolling in a circle" analogy; if the tire has a round profile the uphill side of the tire makes contact higher up its shoulder, which has a smaller diameter than the downhill side. So it's a bit like a cone shape.
That's correct.

Quote:
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And a tire that magically balances the two effects would be immune to camber!
I guess that'd be an infinitely thin tyre. My unicycle came with a 3 inch tyre but the rim is not so wide or this sort of tyre which means the tyre profile is very round. A wider rim flattens the tyre profile. The rounder profile augments the cone rolling in a circle effect. For my rim width, a narrower tyre would be both closer to the idealised infinitely thin tyre and also reduce the cone effect. I've just ordered a 2.5 inch Maxxis Minion DHL (narrower & squarer profile), will report my findings.
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Old 2018-09-28, 09:25 AM   #12
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I'm a uni noob (few months tops) and started with a Nimbus Oracle 24" with the Duro 3" tyre and recently just bought thr Nimbus Oracle 27.5 with the Kenda Havoc 3" tyre.

I'm finding cambers were not an issue at all on the 24 but the 27.5 is wildly susceptible to cambers, to the point that I'm struggling to fight and correct it!

I dont think it's the difference in overall wheel circumference, weight, or the increased centrifugal forces applied with that but I also seem to be twisted to the left slightly as in to correct a natural steering effect to the right which I never had with the 24.

I'm going to try another tyre, any recommendations for a 27.5x 3.0 tyre other than the Schwalbe Nobby Nic?...

Just wondering if the Havoc tyre profile is known for being unforgiving on cambers?
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Old 2018-09-28, 11:24 AM   #13
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Hi there

I think camber is one of those thing you have to put up with. In my experience, the same camber spot can feel very different from one day to another with exactly the same unicyle/tyre combo. I wouldn't give it much thought, after all is just another challenge in the world of unicyling. The wind is another challenge when riding (in my case the 36): if it is a very windy day some sections of your cycling route are going to be a nightmare no matter what: not much you can do about it apart from trying to avoid those particular sections that are facing the wind direction the wrong way
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Old 2018-10-06, 03:12 PM   #14
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Well I put on the Schwalbe Nobby Nic 27.5x3.0 this morning and what a difference over the standard Kenda Havoc.

No autosteer now whatsoever and cambers are back to their normal self, no flinging me down them as soon as the tyre so much as looks at one!

Very good tyre- ridden on sand, rocky terrain, grass and tarmac today and it's a beast... Handles anything!

If anyone from UDC is listening you should seriously consider selling the 27.5" Oracle with the Schwalbe... It's transformational.
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