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I bought a rigid MTB for local and commuting duties, to replace an old BSO and complement my 130/140mm FS bike. The fit feels fine out of the box, but my hands start to hurt after about an hour. I think I should be able to use the geometry differences to work out which bits to change to sort out the fit, but thought I'd best query the wisdom of STW first.
The cranks are 175 vs. my usual 165 which I run for pedal strike avoidance, which isn't a concern on this bike. The longer ones feel fine to pedal, I've just lowered my saddle 10mm to compensate. They're probably longer than ideal for my 5'7", but I ran 170s for years.
The stack is 28mm lower, but I think I only really need to bring it up 18mm because I've just lowered the saddle by 10mm. I'm intending to make this up by replacing the 15mm rise bar with a 38mm (+23mm) one and maybe removing a spacer from under the stem. It's currently maxed out with 20mm of spacers underneath and none above.
The effective top tube is 5mm longer, it has a 50mm +6deg stem vs. my usual 40mm 0deg, and it has a 20mm layback seatpost. I'm intending to put on a straight seatpost to shorten it, which will also bring the effective saddle angle closer to the seat tube angle (75deg vs. other bike's 77deg). Could then shorten further by sliding the saddle forward on the rails.
If my hands still aren't ok, I'll swap the stem for a 40mm, which I expect will affect the steering feel (68deg head angle) - the effective stem length (from centers of the grips) is currently about 25mm. Losing the 6deg stem rise would also take away about 5mm of height, but I should have enough room to compensate with the high riser bar and spacers.
The reach is 12mm shorter, which is fine as numbers matter less when standing up, and this will be mostly a sitting down bike anyway.
Does that sound like it'll work?
Your saddle probably needs to be the same height - I run 170mm road and 175 MTB, and the saddle heights are exactly the same.
Ideally you'll need bars etc, reach to be the same - 2mm reach is a difference. I would say go with lots of neasuring
Sounds like you have already worked it out!
I would suggest changing the cranks though to keep them all the same length. The longer cranks mean lots more hip flexion, etc.
I always set up a bike in this order: crank length, seat height, seat set back, bar height then seat to bar distance.
Compensate for different width bars and the variabilities of suspension sag (or not).
I use a mixture of tape measures, steel rule, plumb lines and spirit levels to get it right. I'm a proper "micro adjuster"!
Your saddle probably needs to be the same height – I run 170mm road and 175 MTB, and the saddle heights are exactly the same.
Interesting. So with your longer cranks you're spinning larger circles 5mm deeper (bottom dead centre) and 5mm higher (top dead centre), whereas I'm spinning them to the same depth but 10mm higher. I'd think that avoiding getting too close to leg lockout at the bottom is the key thing.
I'll admit that when I went from 170mm to 165mm on my FS, the STW thread I found said to raise the saddle by 5mm to compensate - which made sense, so I did it and it was fine. Also I didn't raise my stack to level things out, and the stack is (after much experimentation) where I want it to be for standing up pedals-level riding.
I would say go with lots of neasuring
What an interesting idea 😉 I'm sat in the house at the computer with geometry charts.
I would suggest changing the cranks though to keep them all the same length. The longer cranks mean lots more hip flexion, etc.
Good point. I might well stick on my old 170s that I have on the shelf. Zero cost option to get it to just a 5mm difference.
I always set up a bike in this order: crank length, seat height, seat set back, bar height then seat to bar distance.
Compensate for different width bars and the variabilities of suspension sag (or not).
I believe I can mostly disregard sag in this case, assuming a full suspension bike sags equally at both ends (not quite the case I know), and the new bike being rigid. No pivoting hardtails involved.
I use a mixture of tape measures, steel rule, plumb lines and spirit levels to get it right. I’m a proper “micro adjuster”!
Great, practical equivalent of my trigonometric Excel sheet.
If it is you hands hurting, could it be the angles/ sweep of your bars?
I had a significant reduction in hand pain after changing the angle my bars were at to having no upsweep
I went for the same spank vibocore bars on my MTB's as they feel better than the race Face and renthal bars that were previously on two bikes.
If it is you hands hurting, could it be the angles/ sweep of your bars?
Good shout. I traced a hands issue to having flat bars rather than the slight upsweep of the "good" bike.
You need four measurements (my road bike - but MTB is not so different), all from a decent tape measure
1) BB centre to top middle point of saddle - may be along seat tube depending on seat tube angle (74 cm)
2) saddle nose dropped vertically to cranks (5 cm behind BB centre)
3) distance from saddle nose to handlebar clamp (55 cm)
4) drop from saddle to bars (8 cm)
Once these are as close as possible, the length of the cranks won't be a thing. Going wider bars may matter, with wider putting more weight on your arms as you rotate forwards slightly.
If it is you hands hurting, could it be the angles/ sweep of your bars?
Took a quick look at this, and it's definitely not how it should be. To get the normal 5deg rise, I had to rotate them so far forward that the alignment markings printed on the bars were no longer visible in the stem window. Perhaps they were printed in the wrong position. Will give it a go like this, but I'll most likely do all the other stuff too.
I went for the same spank vibocore bars on my MTB’s as they feel better than the race Face and renthal bars that were previously on two bikes.
I do have a Vibrocore 35 to fit to my MTB, and was pondering them for this bike. They do 40 and 60mm rises in 35mm dia, and 50mm rise in 31.8mm, plus other combinations that would be too low/high for this bike. The minimum cut widths are however wider than I want for this bike, not sure if that's a grip diameter thing or just that I'd be chopping off some of the foam.
Didn't realise the effect the slacker seat tube angle would have on saddle to bar distance, it's more than I can make up for by sliding the saddle forward and putting on a shorter stem.
Now I'm looking in dread at the aesthetics and price of this Thomson Setback (16mm) bent seatpost which can also be used in the forwards direction:
That's a bold look!
This is the only measurement that is the same across all my bikes (with an extra 10mm for the full sus to compensate for the suspension sag).
The rest your body will adjust to as long as the bikes aren't too much different in size ie one bike is a large and the other is a medium.
There's no way I could make my cross bike or road bike fit the same as my mountain bikes, they're different for a reason.
If after riding it for a week or two (after setting up your saddle height) and it's still giving you pain. Then I'd take it along to bike shop and ask them if they could do you a basic bike fit. Could be just a change of bars with a different sweep or even the saddle angle/position. Better than spending money on new components and time using trial and error to get the same result.
Hope you resolve it and are pain free. Happy biking!
I used https://www.bikegeocalc.com/ a lot when deciding on a recent purchase. Put in the geometry and component sizes of your current or best setup bike and overlay it onto another bike. Then you can tweak the position and size of stuff on the second bike to make it match.
Helped me decide between two frame sizes that I fell between and what size stem I needed to order on the new one.
Cheers both.
So far, I've replaced the 15mm riser bar with a 38mm, the layback seatpost with an inline, and the 175 cranks with 170s as I had them spare anyway. £40 spent and it's a lot better but not perfect. The stack is now matched but it's still longer to the bars.
The saddle height is good; I did it by feel and ended up within 5mm of where it mathematically should be (5mm higher than my other bike that has 165s). I've done the angle too.
Just now I've cut the bars from 760 to 730, and shifted the saddle forward 5mm from centre of the rail (the most I can do without foregoing a saddle bag). The distances of saddle nose to stem bolt, and saddle nose edge to grip outer rear edge, are now just under 10mm longer than on my other bike.
Had a play with that geo tool, bookmarked for future. It's a bit annoying how it changes numbers you've already put in, to make the geometry connect up. I'd rather it told me "you just changed x", you need to change X or Y now otherwise your top tube won't connected to your seat tube.