Does my bum look big on this

Does my bum look big on this. Whilst tongue in cheek, some very serious points.

With reference to the post #Optimal Crank length by @Sir_Brian_M and #Check you saddle to improve FTP by @arthur having the right size saddle appears to be incredibly important.

I got a new Giant TCR this summer and the size medium came with cranks. What difference can 2.5mm make? (170s on my old bike). How could I have been so wrong, it screwed my knees, back and neck. 8 Physios later and stretching twice a day and I am just about there.

Also, every crank length calculator I could find suggested the maximum crank length for my very short lengths (I’m 5ft 8ish or 170cmish - with short legs and long body) was max 165mm and from 160 to 165. 165s were easyish to get hold of and I bought a cheapish RS510 for about 90 euros to try. It was an absolute revelation. So much so that when I found a set of Ultegra 165s in stock for 200 euros I snapped them up, put the RS510s on my old bike (now winter bike) and put the Ultegra on the new giant.

The 165s are awesome. I thought I may end up having to spin more, but actually my cadence is the same or slightly less. Because there is no horrendous dead spot at the top of the stroke (7.5mm shorter) it is easier to pedal in circles instead of squares. It is also easier to claw round and pedal in a full circle. I am sure it is more economic in power and gives more power as you have a more complete stroke.

But… something was still not right. The Giant saddle I had never really liked or found especially comfortable, although it was tolerable. I thought my butt would get used to it, but it didn’t.

Finally dug out an old Fizik Arione VS - my preferred saddle had always been the Arione classic. I measure it and the Giant saddle. Giant 140mm wide, Arione 130mm wide. Well, that is a whole cm, so my sit bones must have been splayed apart and my hips too and it must have adjusted my peddling motion and the circles my knee went in it.

So I tried the narrow saddle tonight on my easy 30min session Women’s Movistar Team. I could feel such a difference again. It felt more comfortable not have my sit bones and hips having to accommodate a wide saddle and my knees I did not notice which is good.

So, two revelations, too long cranks lengths and too wide saddle. Whilst I am still “chunky” or “well built” or “stock” if you were being kind, and being now 85kg (but down from 97kg a year and a half ago - but not quite to my old race weight of 70kg), I still must have had a skinny but, even though it did not look like it if you were on my wheel.

So, something also to check for knee pain. Saddle width and height. I though all these different width saddles were just marketing, but no, its not. In the old days I had a Flite saddle and never thought about it. But now with so much choice and so many designs, it is worth taking a bit of time to get the right one for you. Every butt is different, find what fits you.


I can’t remember where I found it but the method of measuring your sit bones is to put a piece of aluminium foil on a hardish but giving surface (think carpeted stairs) and sit on it. The width of the indentations that are clear to see when you stand back up is what needs to be be supported by your saddle. You may need to add a bit so that they’re not right on the edge

I’d be interested to know how this matches the saddle that you’ve found to be the best


+1 for this

I used a damp piece of paper on a hard bench - nicely marks out the pressure from your ischial tuberosities/ sit bones. From memory my distance is ~128mm so a narrow/ small saddle it is for me. I must have trialled about 15 saddles before getting the one that suits my B.