Funny you mention that. I expierience the same problem in the same direction but only on my 26" muni. It seems fine on my 20" trials, figure that one out. So i tried moving my seat to the right a little to compensate and it seems to help.
I fought the same condition on my 24x3 Yuni (Nimbus) for months. I tried reversing the frame on the wheelset, switching the tire around on the rim, aligning the fork legs (at least 3 times). Finally, I gave up and decided to live with it.
I also have a slight difference (10mm) in leg length and believe that the wider (Miyata) saddle may have been part of the problem. After I narrowed the saddle when I did the air conversion, the problem seemed to be less noticeable. What tire and saddle does your Nimbus have on it?
I had the same problem with my 26 inch MUni. So the MUni became a road cycle with a super slick tire and I’ve had no probems since. A few months after riding the slick, I tried the knobby again. I had the same problems with it again. So i’m going to stick to a slick on it.
I’ve noticed this problem on both my 24"s, my 26" DM and my coker. The “rotation error” comes and goes. It seemed to be worse at the begining of a ride, while I was warming up on straight sections. It got to where I’d notice it and try rotating the seat to compensate, but it only put more strain on my back. I tried different seats, and different cycles. Then, when I’d notice myself twisting, I’d do some figure eights, take some tight turns and then go back to riding straight. -This seemed to help.
I asked people about this strange phenomenon at several conventions. The usual answer involed one of my loose screws, or made mention of my inadequate ability to rationally observe the situation. I even posted the question here some time ago. The only plausable response I received mentioned foot position on the pedals. Be sure each foot is positioned exactly the same -that is each toe/heel is the same distance from the center of the pedal. Try wearing boots with heels and then make sure the front of heel is against the pedal on both feet. You may have learned to uni with one foot skewed, and now you need to retrain, but it’s just a guess.
It could also be a bent pedal axle or misaligned crank. If it’s just a loose screw, tighten it.
Does your Pashley have an obvious ridge running around the centre of the tyre, this can be either smooth rubber or knobbly?
Pashley’s used to always ship with a terrible tyre which made riding straight, especially on tarmac, very challenging / tiring.
For tarmac I find a smoother round profile is ideal, something like the big apple or coker design (neither of these are 26"), Halfords in the UK used to sell a suitable own brand road tyre.
For off road the Gazza works for a lot of people, and is ridable on tarmac although the tyre wears very quickly 0n road use. The Gazza obviously suffers pulling with road camber (due to its width) but much less than the tyre Pashley used to supply.
All my unicycles started pulling to the left at the same time a couple of weeks ago. They seem to be perfectly in alignment, but they all pull to the left in exactly the same way. Obviously they have been cursed by a powerful voodo cycle-mechanic.
Oddly, the day before my unicycles were cursed I strained a muscle in the right side of my back. My pedaling became choppy and my right leg seemed to tire much faster than my left. The cursed unicycles seem to affect my right leg, making it stiffen and resist the upstroke on every revolution. It’s as if I’m “limping” on the unicycle, or favoring my right leg.
I’m working on evening out my pedaling force left and right, and relaxing my right leg, which helps, and sitting up perfectly straight, which helps even more, but what I really need to do is find that voodo mechanic and get the curse lifted. D’ya think a bottle of vodka and a cigar would help?
I have had this problem on my 24x3, but I’d feel myself twisting in the seat loads to counter it. I think foot placement on the pedals was the problem tho. When I ride on carpet (the really short haired carpets, that are almost like felt) whatever uni I was riding would always pull to one side, to the extent of throwing you off nearly! Interesting ride tho! I could never line up right for rolling hops and drops etc!
As strange as this may sound, if you have another saddle with a different center width (viscount or “cheap uni”) try it on your Nimbus and see if you notice any improvement. The narrower saddle may help to “center” you on the uni. It worked for me
i sometimes experience the pulling right problem. or for me the problem exists as having to ride with my torso twisted. it hasn’t showed up lately. the last time was when i switched from a gazz tire to a fireball. i rode twisted with the fireball for a while and then i untwisted. the problem went away. then i switched back to the gazz and i twisted again. then it went away again.
jerryg’s comments about turning in figure 8s sounded good to me. i remember doing something simlilar to help me. the problem is non existent while riding twisty singletrack.