Bike Fit for mtbvfr


New Member
Jul 12, 2022
Hi Folks,

Hope this the best Sub-forum for this.

I have some questions for the Bike Fit gurus.

The bike in the photo has a 130mm/5° Rise stem. The frame is a 19" 1990 Diamond Back Ascent. I have marked the dimensions of the bike's actual Top Tube length as well as the length from the centre of the rails to the centre of where the steerer tube would be if it extended that far.

I have uneven leg lengths and to help counter that the Right crank (180) is 5mm longer than the Left. My Right Femur is 5mm longer than the Left and the Lower Right Leg is 3mm longer than the Left.

I'm always having to push my butt backwards and the only thing I can think of as to the cause of that is that my knees/legs want to be further forward to be better positioned over the cranks.

However, moving the saddle forward means my back is more curved and constricts my breathing.

This current configuration is more comfortable than previous iterations where I tried shorter and taller stems with which I found I was having to push my butt backwards more often.

The current bar has a 35° back sweep which doesn't make for a good position for the bar-ends when standing out of the saddle. However, Ergotec has a 23° bar which shouldn't be too much different to a 25° bar which I found to be ok when standing out of the saddle.

This current bar has a 31.5mm mounting diameter and 0mm rise which affords a pretty comfortable aero position when placing my hands on the bar next to the stem.

I would prefer the stem to be no more than 120mm long.

Vital Statistics
Inseam: 84.5cm
Thigh: 41.0cm
Arm Length: 61.0cm
Torso Length: 60.5cm
Foot Length: 26.1cm
Height: 5" 10" = 177.8cm or thereabouts.

So, what Effective Top Tube length do you think would be more suitable for me?

Apart from having a custom frame made, were any frames made in the 90s with longer Top Tubes than what I am commonly seeing?

Do you see any changes I could make to the current configuration to make things more comfortable?

I wouldn't want a bike with a taller Seat Tube and I would prefer a lower Bottom Bracket too.

Thanks!, MTB.