Very confused about riding position(s) - mtb vs road

[foz]

If setup on both bikes is different, then of course they will feel different. Get the road bike position sorted first, then you can adapt those measurements to the MTB, which is easy especially if it's a retro MTB and not a modern one (retro MTBs are a lot closer to road bikes than modern ones). You could get a professional fitting, but this will cost quite a bit and isn't really needed. I would start by using the "traditional" methods for determining saddle height, setback, and then bar position. This will give you a starting point, from where you can make small adjustments to feel the effects and find the position most comfortable for you.
And you do not need any particular length of crank. By all means try different ones, but don't think that for your height you must use a 165mm crank or whatever. Use what feels best.

 

[Ugo51]

Oh, I've been playing with the "traditional" methods since I got the bike, about 14 months ago. I need some fine tuning or something that might be obvious to an expert, but not me.

The 165mm cranks are certainly not a must. But so far I've only ever ridden 170mm so I have no way to know what "feels best". Maybe 165mm will feel wonderful. Maybe not. I have really short femurs, so I expect it to feel good, but only time will tell.
I actually tried the 165mm for a few hundreds meters, when I tried to fit them on the current bottom bracket, and they did feel good. I just couldn't keep them on as the BB axle legth was wrong.
Will get it sorted when I'm back next week!

 

[2manyoranges]

165 will make your feel as though you need to up your cadence and change down a gear to get the same speed, Which you will. I was told I would before making the switch. And they were right.

 

[Ugo51]

I am counting on it!

165 will make your feel as though you need to up your cadence and change down a gear to get the same speed, Which you will. I was told I would before making the switch. And they were right.

I am counting on it!

 

[eightyeight]

And don't forget you'll need to adjust your saddle height for shorter cranks.

 

[2manyoranges]

Bloody hell…I got the commuter out of the shed this morning and arrrrgh puncture….late…so swapped lights onto the nearest bike - Ragley mmmmBop hardcore enduro bikes with 35mm front rim, 160mm of front travel….and 165 cranks…by God that was hard push in…spin on the cranks with a higher cadence, keep the big rubber rolling….in the end, the same time getting in but A Very Hard Push and much spinning….

 

[Ugo51]

And don't forget you'll need to adjust your saddle height for shorter cranks.

I will, thanks

 

[Ugo51]

Bloody hell…I got the commuter out of the shed this morning and arrrrgh puncture….late…so swapped lights onto the nearest bike - Ragley mmmmBop hardcore enduro bikes with 35mm front rim, 160mm of front travel….and 165 cranks…by God that was hard push in…spin on the cranks with a higher cadence, keep the big rubber rolling….in the end, the same time getting in but A Very Hard Push and much spinning….

What crank length do you run on your other bike(s)?

 

[2manyoranges]

Both my son and I are around 170cms (he’s a wee bit taller) and 31 inch inside leg, and we run 170mm cranks on the 27.5 and 29er enduro bikes with high BBs and good ground clearance. We run 165mm on DH bikes and enduro bikes with low ground clearance (mmmBop in particular, which is a real knuckle-dragger). Road have 170mm.

When Grom was tiny, I actually had Zee cranks milled-down specially for his DH bikes - 142 for his first 24inch wheeled Commencal Supreme.

Interestingly, a number of really good analyses of the impact of crank length on the power output of people of different heights. Turns out it’s really important for taller people to have the right length cranks since they have to turn so much more mass - there’s a real sweet spot for taller people which is very important to hit…..and it’s less critical for shorter people since they can rotate their legs that much faster. Counter-intuitive, but the analysis of output is clear.

 

[Ugo51]

Interesting that you run different lengths on different bikes. Makes sense.
I heard some prefer to have the same length on all their bikes but I guess it's down to personal preference.
I'm really curious about trying the 165mm and see how they feel!