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Brompton Geometry Help

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Old 05-14-18, 01:58 PM
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rishardh
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Brompton Geometry Help

I am thinking of adding a Brompton to my commute fleet. I've got my bikes setup a certain way and would like a Brompton to be closer to that. I've found information on handlebar height from the ground but could not find any meaningful measurements (in relationship to the BB for example) to see if I need to get a M or S handlebar. This is how my other bikes are setup...

BB to top of saddle = 27" or 68cm
Handlebar drop in relationship to top of saddle = 2" or 5cm. What is this measurement when the saddle is set to 27"?
Handlebar reach in relationship to center of saddle top = 24" 61cm. What is this measurement when the saddle is set to 27"?

Would appreciate if a Brompton owner can get me these measurements and let me know if it's a M or S handlebar. Unfortunately there is no Brompton dealer close to me. From what I have seen the M handlebar can be adjusted forward or backwards to some degree to customize your reach but the S handlebar is further away and fixed.

FYI, I commute to work about 28 miles a day. Mostly paved trails, some sidewalks and parking lots and a hike a bike section. I've also had gearing questions but I've got that sorted out. Thanks!
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Old 05-14-18, 05:35 PM
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Measured my Brompton S, 2015 model.

BB to top of saddle = 27" or 68cm
Handlebar drop in relationship to top of saddle = 0" essentially level to center of bar
Handlebar reach in relationship to center of saddle top = 27"

Couple confounders: Center of BB is approx 1 1/2" forward of the centerline of the seat post. You can likely move the seat forward in the clip to obtain a 24" reach to the center of the saddle top. That's likely why a lot of Bromptons in photos look like the seat is pretty far forward on the seat post. I measured to the center of the seat post, moving the measure to parallel the seat post from center of BB to top of saddle gets closer to your desired drop and reach. You can probably get a close fit.
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Old 05-14-18, 10:11 PM
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Thanks Kahuna.Really appreciate you taking the time to give me the numbers I have been looking for. I never noticed the seat post being behind the BB. Thanks for pointing that out. Based on that I guess the S handlebar will suite me best.


Another thought is get the M handlebar and swap it for a S or 25.4 MTB flat bars for better reach and probably a slight drop. No need to replace cables and if I find MTB bars I just cut it to make it narrower like the S bars. I am probably over simplyfing it, haha.

I wish I had a dealer close by.
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Old 05-15-18, 07:05 AM
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Better bet may be to get the S model but change the bars to gentle riser bars and then you can get a little extra height or forward or back changes..
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Old 05-15-18, 07:40 AM
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Originally Posted by tudorowen1 View Post
Better bet may be to get the S model but change the bars to gentle riser bars and then you can get a little extra height or forward or back changes..
Thanks, Will I need to replace the cable if I go this route or is there enough slack to go up 2"?

Choices are...
M Model swap to flat bars - Overall shorter reach and slightly lower. No need to change cables.
S Model swap to riser bars - Adjustable reach and slightly higher. May need to change cables.
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Old 05-15-18, 08:41 AM
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3 seat post options, 4 bar mast bar combo options* frame 60cm long..

* a dimensioned drawing of the 4 is online and has been posted here repeatedly..

the H with a flat bar is like the S, in height , but hinge is higher and so M
or any lower rise bar wont hit the ground, folded..
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Old 05-15-18, 09:13 AM
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Originally Posted by fietsbob View Post
3 seat post options, 4 bar mast bar combo options* frame 60cm long..

* a dimensioned drawing of the 4 is online and has been posted here repeatedly..

the H with a flat bar is like the S, in height , but hinge is higher and so M
or any lower rise bar wont hit the ground, folded..

Can you forward me a link pls. All I could find was handlebar height diagrams. Thanks!
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Old 05-15-18, 09:51 AM
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https://www.brompton.com/ ?









...

Last edited by fietsbob; 05-16-18 at 12:49 PM.
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Old 05-16-18, 02:49 AM
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Originally Posted by rishardh View Post
Can you forward me a link pls. All I could find was handlebar height diagrams. Thanks!
https://www.google.com/search?q=pict...w=1355&bih=619
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Old 05-16-18, 09:16 PM
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Rode my wife's Dahon Eco 7 to work today to see how I felt. The handlebar was about 4-5 inches higher than the saddle and I felt too upright. Halfway through the ride felt the weight of the backpack on my shoulders. On my other bikes the weight is distributed on the entire back I guess. I definitely need the handlebar to be level or lower than the saddle.

On the plus side was able to look around and enjoy the view, notice the ladies blowing flying kisses, etc, haha. Definitely more lookers than normal.

Thanks for the links f.bob and b.mother. Did not get exactly what I wanted but I have an idea what I need now. The S stock setup will be the one for me I think. With the S the handlebar will be pretty much level with the saddle but I will be stretching forward. Very similar to my MTB bike and that will be fine.
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