Dumb or ok?
I love threads that start this way. My issue- I have two bikes… a tri bike with a power tap and a mtn bike (no power). I typically switch to riding my MTB full-time in the winter and would like to get in 1-2 interval workouts during the week on the trainer (yes, I like riding on the trainer). I’d like to do these with power but don’t want to invest in a PM for my MTB for only 1-2 workouts a week. So of my two options which is better-
Do said workouts with my tri bike on the trainer (my concern here is that the geometry is way different than my MTB. I haven’t measured my difference in hip angle, etc but I’m comfortable on both bikes although I feel very different muscles working when powering one vs the other.)
As an experiment I put a MTB cassette on my power tap wheel and put the whole thing on my MTB. Obviously it looks weird but it works, feels solid, etc. Is this safe or am I at risk of causing any damage to the wheel / hub itself?
I assume your mountain bike is a 29er, otherwise I can’t imagine the road wheel would fit… But, road hubs are usually 130mm and mountain bike hubs are 135mm, so while the road hub will fit in there, there will be too much wiggle room and you may be bending your mountain frame dropouts when you tighten the QR.
I just leave the tri bike on the trainer all winter and leave the mountain bike for riding in the woods where it belongs.
Road wheel will typically fit a 26" mtb but the brake tracks wont line up. Bigger rim smaller tire, frame with lots of mud clearance.
The rear triangle size is an issue like you say. Steel is of its flexy, AL may have issues an will carbon, but he already did it so if nothing went wrong it should be find. Its only moving each side in 2.5mm.
Dumb or ok?
I love threads that start this way. My issue- I have two bikes… a tri bike with a power tap and a mtn bike (no power). I typically switch to riding my MTB full-time in the winter and would like to get in 1-2 interval workouts during the week on the trainer (yes, I like riding on the trainer). I’d like to do these with power but don’t want to invest in a PM for my MTB for only 1-2 workouts a week. So of my two options which is better-
Do said workouts with my tri bike on the trainer (my concern here is that the geometry is way different than my MTB. I haven’t measured my difference in hip angle, etc but I’m comfortable on both bikes although I feel very different muscles working when powering one vs the other.)
As an experiment I put a MTB cassette on my power tap wheel and put the whole thing on my MTB. Obviously it looks weird but it works, feels solid, etc. Is this safe or am I at risk of causing any damage to the wheel / hub itself?
tks in advance.
Why don’t you get a smooth mountain bike tire and get a broken wheel from the bike shop. Then just swap them before you get on the trainer. You could probably get that set up for less than 30 bucks.
On average. But it could well be 4mm one side and 1mm the other. As you say, unlikely to be an issue with steel, but for the others, with the added stresses of clamping onto the rear triangle then personally I’d not want to do that for anything other than a one off test, certainly not a winters worth of training. Although in fairness it ought to be a lot better than a 135mm hub in a road frame as an MTB should be built for more loading. With spacers then it should be fine.
thought I explained this in my original post. My geometry feels (though I haven’t measured) drastically different between both bikes. If I’m busting my butt on the trainer for the purposes of getting faster on my MTB, I’d like to replicate the MTB geometry as much as possible. Now if a FIST guru can comment that hip angle / etc should be the same regardless of what bike you’re on, I’d love to hear details. I don’t think this is the case though.
I get it, considering this site I figured you would want to be in your tri specific position. If you can ride outside some I’ve never found a big or even any different between what bike I ride for intervals on the trainer.
That would work, they don’t have to be locked down just put one on each side of the axle then put the wheel in the frame. I’d get both the 2.5 and 1.5. Just in case the 2.5 does not leave any excess room past the axle.
No need to use spacers. All frames can handle 2-3mm of bending either way. There’s a lot more stress&flexing going on in an all-out standing start or sprint.
Don’t worry about it. MTB wheel in road frame or vice-versa, no problems. Seriously.
I agree, there should be no problems at all since you don’t need to worry about the brake track lining up. The outer diameter of the tire is pretty close since the extra MTB tire volume offsets the smaller rim (unless it’s a 29er, of course).
As for the difference in axle spacing, anyone can put a bike in the stand w/ the rear wheel removed and try squeezing the dropouts together with your hand… EASILY ~5mm+ worth of flex, no big deal. With the hub clamped in for bracing, the amount of additional flex under pedaling load is negligible (the bigger issue is still the mating of the skewer ends with the trainer’s mounting cups… THAT’s where 99% of the problems come in, regardless of the wheel). I’m always amazed that folks act like we’re working with glass eggshells and yet we stomp and yank the shit out of it in a sprint or standing on a steep climb.