Frame size advice

6 replies · 190 views

rockymountainhigh
33 posts
#1May 6, 2019, 5:18 PM
Per my other recent post about building a drop bar no suspension gravel MTB...
Frame sizes...
My Diverge is a 58cm...I also have an older Trek Mamba 29er hardtail that is 17.5 inches.
With the frame I will be picking up... 17, 17.5, 19?
My body size is a bit weird and bikes are always a hard fit honestly.
I am 6 feet tall but have the legs a person 6'2 and the upper body of someone that is 5'10.
Long on the legs short on the reach.
Most of my bikes always end up with the seat jacked up so high it looks stupid.
Assuming the drop bars will effectively make the long mtb top tube longer should I stay with a 17 or 17.5 frame?
Getting one of the Chinese frames so I will effectively have one shot to get it right. I am working with my local mechanic/fitter who does all the work for me but I figured I would ask here.
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owly
328 posts
#2May 6, 2019, 5:56 PMedited
I would focus on stack and reach when looking at frames (and seat tube angle). Personally I'd be looking at those china frames; hunting for options which have the tallest front end, with the shortest reach. I know many mtb frames these days have the long-reach trend, so it might be tricky finding a best frame to suit.

Apart from chasing a taller front end, you can get an idea of where the drop bar will be positioned by using one of those online stack and reach bike calculators. Basically you can play around with stem lengths/angles (with spacers amount) and see the numbers. There's at least a couple of these sites which show two frames overlapping side-on which is helpful e.g. mtb frame + drop bar frame (your Diverge).

You probably know drop bars can vary wildly in their reach and drop, which is something to consider in the mtb frame's overall reach.
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nellborg
142 posts
#3May 6, 2019, 8:46 PM
I second what owly said - stack and reach for the frame, and reach and drop for the bars. As long as the seat tube angle is ok for you, that's the best place to start. Frame "size" isn't a relevant number by itself.
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rockymountainhigh
33 posts
#4May 6, 2019, 9:20 PMedited
Looking at some stuff now.
Luckily the DIY Carbon place has a "this frame is based on this bike" so I can sort of close with measurements.
The MTB frames do have crazy long head tubes/reach these days.
I am most likely going to have to stick with a 17/17.5 inch frame and deal with a jacked up seat. I can probably get my reach worked out via some spacers and a positive angle stem. I don't mind having an aggressive setup I just don't want to feel like I am riding TT aero bars.
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rockymountainhigh
33 posts
#5May 6, 2019, 9:21 PM
Does anyone know what the frame geometry comparison tool online is called?
The ones I have been trying just allow you to input existing brand name bikes.
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rockymountainhigh
33 posts
#6May 6, 2019, 10:20 PM
The overlay geometry page is called 99 Spokes FYI.
htttps:// 99spokes.com
It assumes you know the stack and reach...In my case I did not so I had to do some estimating using other calculators but I was able to come up with some good info and I think I am off to the races.
Thanks for the help everyone!
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nellborg
142 posts
#7May 7, 2019, 5:38 AM
The stem comparison tool is this one - in case you don't already have it:
yojimg.net/bike/web_tools/stem.php
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