Another Nerdy bike fit question

ddraver

Hi Guys

Say on my road bike (170mm cranks), my BB - saddle height is 700mm

What should my saddle hight on my fixie (165mm cranks) be and on my MTB (175mm cranks)

Any comments about buying some different cranks may well get a sarky response!

964cup

Broadly, 5mm higher on the fixie, and 5mm lower on the MTB. But it will depend on pedal stack too. If you're using flat pedals or SPDs on the fixie, for instance, these will have a lower stack (and so effectively a longer distance from saddle to pedal) than Look/SPD-SL road pedals. It will also depend on geometry, so best to treat each bike independently for fit.

ddraver

much obliged sir. It was more so that I could make a start on that process really...

kajjal

Just make sure you measure vertical height as most seat posts also move the saddle backwards as you raise them and just measuring the seatpost is inaccurate as it is not vertical. Not much of a problem for small adjustments but more noticeable with larger adjustments. The main thing is it feels right.

ddraver

So now - this is the bike I have had fitted



The article on fitting Road and MTB bikes on BR suggests that one should rotate the body position around the bottom bracket. The red circle is centred around the BB and the blue and green lines are reach and stack respectively.

Am I right in thinking that my XC MTB position should lie somewhere on the red circle?

Thanks all, I'm learning!

kajjal

From my experience my saddle position on my xc mountain bike is a little lower than my road bike but the tilt, fore / aft position is very similar. The reach is a bit less and the drop similar as I have my road bike setup fairly upright. Since you more around a mountain bike a lot more and riding styles vary more you can get away with being less accurate.

crikey

Most saddle heights are measured from the centre of the bottom bracket, deliberately to take crank length out of the equation.

It won't really make any difference.

5mm is tiny and can easily be made up by a slight tilt in foot position. The idea that you have to be millimetre perfect is a bit silly, otherwise we would be adjusting seat height according to whether we were wearing tights or not, or adjusting seat height when you buy new shoes...

markhewitt1978

Crank length does make a difference. I went from 170mm to 165mm and my pedalling feels much more fluid.

foggymike

...and I do change saddle height of I buy new shoes (and I'm not alone). Some people are more sensitive to these things than others.

ddraver

Thanks for the replies guys. Am I right with the red circle idea though?

Becasue


and



suggests the MTB is probably too big, although it doesnt account for fork sag which will drop it closer to the circle (yellow circles are used to guage the size of the photo by matching it with the wheel

ben@31

Get a RockShox Reverb dropper post, for the MTB. Then you can adjust the saddle height to what ever you want while riding. I think the seat post has 100mm or 120mm of travel depending on the model?

My nerdy questions... Is it a Grand Canyon CF SLX 9.9 in the photo? Interesting Mucoff mat and place for the Garmin computer mount (haven't seen them before).

ddraver

It is...

Having the Garmin mount there keeps it out of the way in a crash (however if your straddling the bike it can get dislodged more easily though so it's not ideal). The top/down tube join is nt so good for that.

Saddle hight is not really the question I am asking any more - perhaps I should have started a new thread -