I’m a mountain biker. I have a road bike on my indoor trainer - my training bike. I would like to make this training bike fit exactly like my mountain bike. So I’m gonna try to change to flat bars from drop bars.
Just to double check: your trainer bike is a road bike, correct? In that case, I don’t think it will work as the assumed body positions are very, very different. Just to give you an idea: here is a comparison of the geometry of a 3T Strada (an aggressive aero road bike, in white) to a BMC Twostroke (an XC hardtail, in black):
Importantly, both bikes are in the same size (L, which is my size). You see that there is no way to attain the seating position of the hardtail on the road bike. For example, if you want to build a gravel bike with flat bars, manufacturers will often suggest you upsize your frame.
Yes, my indoor bike is a road bike.
That’s a good picture, and if I was riding on the road, clearly I couldn’t mimick a MTB fit as things like wheelbase and head tube angle can’t be adjusted.
But, it doesn’t actually show the contact points. Which I think is all that should matter on a stationary bike, right?
Basically, I think all that matters is the measurements of the “triangle” made up of pedals, seat, and bars. I’m just not sure how to replicate this triangle and install flat bars on my road bike.
Let me know if I’m missing something!
No, it doesn’t, but you can make inferences: the stack height of the MTB is dramatically higher and is farther forward. So you’d need a ton of spacers and a very, very long stem that points upwards.
Seeing how big that difference is, I don’t think it is feasible. Personally, I’d just look for a cheap used mountain bike somewhere.
or just ride the road bike on the trainer in a comfortable setup/position… Maybe for the pro’s it’s part of the marginal gains that can make a difference on the podium on race day, but for the regular cyclists, it better to just train a bit more instead of worry about stuff like this.
To be honest, I kinda like having multiple positions on a drop bar indoors. When your position/posture is so static, it’s nice to be able to change hand positions. Outside on the MTB it’s not that applicable because it’s way more dynamic, but I prefer my road bike indoors over the MTB.
What is your personal reason to train indoors with the exact position as your MTB? power/position, comfort, …?
As @OreoCookie has mentioned, it could be tough to get the bike fit the same as your MTB.
Are you dedicating this bike to the trainer? That means that you wouldn’t need brakes, or really even a shifter if you’re in ERG mode.
I’d measure the tip of your saddle in relation to your BB on your MTB and see if you can get the offset the same on your road bike. If you can, then measure from the tip of the saddle on your MTB to your handlebars and see if you can get a stem that is long enough on your road bike to match that measurement.
Depending on the sizes/geometries of the two bikes, it could take a really, really long stem to achieve this. You also have to consider stack height. Road bikes are usually lower than MTBs which may or may not be an issue for you.
Mainly comfort I guess. I’m training to race my mtb, so I figured it makes sense to have the same setup/fit. I had my mtb on the trainer, but got tired of taking it on and off, so I bought a cheap road bike for a trainer bike. Its immediately so different I hate it - my back hurts and I could barely finish a workout cause my triceps hurt. I can’t stand the narrow bars if I hold on to the tops, and the drops feel horrible. I just want the same, upright, comfortable MTB marathon position. I care nothing about aero position comfort or conditioning my core to stay in the drops.
Thank you! So, I guess it looks like this:
The only other thing I could think of would be crank arm length, and I’m not too worried about that.
The easiest would be to get a beat-down mountain bike. You don’t need a functioning fork, brakes and the like. You might want working gears (1x11 should be enough) if you prefer resistance mode to erg mode. Otherwise, you don’t even need working shifters.
The only bits where I’d invest money is a good seat, suitable handlebars, the right pedals and perhaps a pedal-based power meter.
Price-wise, it wouldn’t be that much more expensive than trying to reproduce your MTB’s fit on your road bike.
Pretty much all modern threadless stems have the same ID and will fit on any fork’s steerer tube, although some MTB stems now have a 35mm handlebar clamp to fit 35mm bars, while the others are still using 31.8 (same as road bars). As long as you’re using 31.8mm bars, you shouldn’t have any issues with your handlebars.
For a long time, pretty much all bikes (road & MTB) were using the same 31.8 stems/bars and were all interchangeable. Since a lot of MTBs are moving towards 35mm (
) you just need to make sure that what you’re getting is 31.8. You won’t likely find a 35mm stem that’s long enough for what you’re trying to do. Again, I’d take all the measurements first to make sure that you’d even be able to find a stem long enough to make this work before doing anything else.
To measure the saddle position in relation to your BB, place your rear tire perpendicular to a wall and measure from the wall to the center of the BB. Then measure from the wall to the tip of your saddle. The difference is your saddle setback. You can also do this with your bike on a trainer.
Fair points, but I’ll say two things (as someone who’s primary discipline is XCO and marathon)
You almost certainly have the bike setup wrong if your back hurts and your tri’s are getting fatigued. Other than fitting the bike properly, it could take some time to acclimate to a new position, which could be a benefit for point 2 below.
You should absolutely worry about your core strength for anything bike related. Nothing to do with “aero” or not, it just makes you a more functional rider.
Riding inside on a stationary trainer will never feel like riding outside, especially on a mountain bike. The upright nature puts a lot of pressure on the sit bones and can lead to lots of discomfort even if you never feel that outside. Simply copying the geometry of your mtb may not be enough to be comfortable on long inside rides.
Just my opinion on things, hopefully it’s helpful.
MTB is also my primary discipline, but for some reason I hate riding it on the trainer, road bike feels way more comfortable.
But if you did want to copy the fit, you could start with this calculator Bike Geometry Calculator - MAD SCIENTIST MTB
Input the two geometries, input the MTB cockpit dimensions, then figure out what kind of stem/angle/spacers you’d need on the road bike to put the stem/handlebar in the same position, and what you’d need to do to the saddle to get similar fore/aft position.
You can get 140mm stems for 31.8 and/or use this bar: REMLAW Bar – Curve Cycling
The bike industry had to plan in some more obsolescence so they revamped their mountain bikes around “progressive” geometry which is fine for winch and plummet riding but those steep seat angles put you too out of balance for sustained pedaling without blowing out your hands and triceps.
