Bike size help - have stack and reach

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2014-04-01 7:58 PM


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Subject: Bike size help - have stack and reach
My stack is 510 and reach is 405. Deciding on a trek speed concept size. Tested on a small it was comfortable. My numbers are in between sizes. Go for the smaller frame if it's comfortable?


2014-04-01 10:15 PM
in reply to: wannatri?

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Subject: RE: Bike size help - have stack and reach
It seems to be current thinking to generally assume the larger frame may be slightly more aero.
2014-04-02 5:43 AM
in reply to: wannatri?

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Subject: RE: Bike size help - have stack and reach
You're very close to the Medium Speed Concept… Stack 517, reach 408.

One very important question though, is that stack adjusted for a specific set of aero bars, or is that true frame measurement? Many times, bike fitters will take the aero bars into account when fitting you… You can easily deduct about 10mm and add 30-40mm to the stack with different aero bars (which will have an impact on the reach as well btw…. they're not independent from each other).

Another brand that would probably work out really well for you would be Boardman. The AirTT9.x (9.0,9.2,9.4,9.8) in small has a stack of 500 with a reach of 404. Those extra 10mm of stack needed could be adjusted with either a spacer under the stem or raisers under the aero bar pads.
2014-04-02 9:00 AM
in reply to: audiojan


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Subject: RE: Bike size help - have stack and reach
Originally posted by audiojan

You're very close to the Medium Speed Concept… Stack 517, reach 408.

One very important question though, is that stack adjusted for a specific set of aero bars, or is that true frame measurement? Many times, bike fitters will take the aero bars into account when fitting you… You can easily deduct about 10mm and add 30-40mm to the stack with different aero bars (which will have an impact on the reach as well btw…. they're not independent from each other).

Another brand that would probably work out really well for you would be Boardman. The AirTT9.x (9.0,9.2,9.4,9.8) in small has a stack of 500 with a reach of 404. Those extra 10mm of stack needed could be adjusted with either a spacer under the stem or raisers under the aero bar pads.


That stack was was adjusted on a fit bike using the fist method. I don't know what the bars were or the stack.

Most importantly I want to know if I could adjust a size small Trek frame to fit. I have a line on a new old stock 2012 7.8 at a killer deal.

Here is what else I have:

Saddle height: 69.5
Saddle height over bars: 3cm
Saddle to handlebar reach 38.5cm
seat angle -3.5
saddle fore aft(cobb V-flow plus)
Stem Length - 100
stem angle 0
2014-04-02 4:40 PM
in reply to: wannatri?

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Subject: RE: Bike size help - have stack and reach
It's not only stack/reach that differs between the Small and the Medium SC… front/center dimension is significantly shorter on the Small (575mm) versus the Medium (598mm). I would fear that you would have to either ride in a slacker position than you would like or have a lot of forward weight, causing imbalance and instability.

Can you fit on a small? I guess the answer is yes, but it is quite a bit of a compromise. So…. you need to ask yourself what is more important, a good fit and thereby speed/comfort or saving a bit of money and risking that you are not going to gain the speed you hoped for.
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