OK so opening up the discussion as much as anything. But interested to hear some feedback. I got a really good deal on a set of 12 inch wheels for my XR and got a chance to ride them a bit. The 12s setup consists of a 2.15 front and 2.5 rear and on TT93s and geared to match the gearing setup I had on the 16 in setup with BT45s. Couple of initial impressions, bike actually seems more stable at lean but twitchier when changing directions from being mostly upright. I can get pretty much right to the edge of the tires and profile looks good and feels pretty stable on the edge of the tire. Bike seems to punish you a lot more with movement if your inputs are not really smooth compared to the other setup but less "moments" if you push it a little. Drum brake seems alot better on the small wheels, acceleration seems a bit snappier. Here is the gripe. Track is a .6 mile track and my lap times were in the 56 sec range on the 16s and after several hours of track time over a couple days I could only seem to run in the 58s on the 12s. Ground clearance is an issue but riding road race style and trying to get off the bike it could be minimized so only barely scraping pegs in a couple corners. Is there anything inherently difference about riding the 12s that I should be taking into consideration. To be honest I expected the bike the be a little faster from reducing the rotational inertia and figured the TT93s would be better than the BT45s in terms of grip.
What was your gearing on 12" vs 16"? I think playing around with the gears will help. I ride a Suzuki RM65 with 12" tires. On my track, we have a long straight and I geared my bike, so that it starts to top out at the end of the straight.
^^ Identical or at least as close as gearingcommander.com is accurate. I picked the sprocket size to match tire size reduction. Gearing was VERY similar as shifts were in approx same locations on track.
Additionally another question that would be related I suppose. How can you best setup bike geometry (assuming front and rear ride height adjustability) to match the difference between the setups. Normally when its just a different tire you can pick a point on the bike, measure, and adjust but with such a major difference between the two setups that won't really work?
im just too large for 12" wheels on stock height 100. With 14s my boots/legs limit lean angle... I might try lowering the forks in the triples a couple mms and maybe go with a slightly longer shock in the rear. Even so most Orgs rules dont allow 12"s as part of a stock based class unless its for groms only. 2 seconds seems like alot of time... are you able to swap back & forth pretty easy?
Yeah easy enough I suppose. I though about doing just that, swapping the 16s back on and riding them back to back. I have two different length chains though that kinda makes it sucky to swap back and forth but its still doable. I definitely would like to raise the bike up some if I could but the rear linkage doesn't really let you fit a longer shock without interference easily. I also was looking at ways to raise the pegs and then maybe a tall seat to re-open the rider triangle. 2s is a lot of time but I am not quite convinced it is the limit but rather things are not setup well to use the smaller wheels (or I am not riding it right).
You say you have different chains, so which set up gives you the longer wheelbase? It might be a factor of the wheelbase difference that is making you slower on the 12s.
