Cycling and bicycle discussion forums. 
   Click here to join our community Log in to access your Control Panel  


Go Back   > >

Bicycle Mechanics Broken bottom bracket? Tacoed wheel? If you're having problems with your bicycle, or just need help fixing a flat, drop in here for the latest on bicycle mechanics & bicycle maintenance.

User Tag List

Reply
 
Thread Tools Search this Thread
Old 02-21-05, 11:21 AM   #1
BillyBob
Senior Member
Thread Starter
 
Join Date: Jul 2004
Bikes:
Posts: 462
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Help Needed With Stem Math

After much research into the night, I want to run my calculations past some people with math and mechanical skills which I lack.

I am attempting to raise my handlebars. I have been trying to calculate the effect of increasing the angle on the rise and reach of the handle bars.

Current stem is -6 degrees and a length of 110mm. I calculate a rise of -11.5 mm and a reach of 109.4 mm.

If I were to acquire a +17 degree stem at a length of 110mm. I calculate the rise would be 32.2 and the reach would be 105.2 mm.

Changing from the -6 degree stem to a 17 degree stem of the same length, I figure that my handle bars would be 43.7 mm higher and 4.2 mm closer.

Am I correct?
BillyBob is offline   Reply With Quote
Old 02-21-05, 11:24 AM   #2
moxfyre
cyclist/gearhead/cycli...
 
moxfyre's Avatar
 
Join Date: Oct 2004
Location: DC / Maryland suburbs
Bikes: Homebuilt tourer/commuter, modified-beyond-recognition 1990 Trek 1100, reasonably stock 2002-ish Gary Fisher Hoo Koo E Koo
Posts: 4,166
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Yep, I ran the numbers through my calc. Looks like you've got your trig right.
moxfyre is offline   Reply With Quote
Old 02-21-05, 11:30 AM   #3
531Aussie
Aluminium Crusader :-)
 
Join Date: Apr 2004
Location: Melbourne, Australia
Bikes:
Posts: 9,991
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
I don't know the maths, but when I'm comparing bikes, I measure reach from the middle of the handle bars to either the tip of the seat or a spot on the seat post. It's obviously not like using a theodolite. but I get a good idea.

When comparing bar height form bike to bike, I get a rough straight line from the top of the bars to the middle of the fork steerer, then measure this point to the bottom of the steerer. This way you don't have to subtract head-tube length, head-set stack height, spacers and stem height.

Last edited by 531Aussie; 02-21-05 at 12:24 PM.
531Aussie is offline   Reply With Quote
Old 02-21-05, 11:35 AM   #4
moxfyre
cyclist/gearhead/cycli...
 
moxfyre's Avatar
 
Join Date: Oct 2004
Location: DC / Maryland suburbs
Bikes: Homebuilt tourer/commuter, modified-beyond-recognition 1990 Trek 1100, reasonably stock 2002-ish Gary Fisher Hoo Koo E Koo
Posts: 4,166
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by 531Aussie
I don't know the maths, but when I'm comparing bikes, I measure reach from the middle of the handle bars to either the tip of the seat or a spot on the seat post. It's obviously not like using a theodolite. but I get a good idea.

When comparing bar height form bike to bike, I get a rough straight line form the top of the bars to the middle of the fork steerer, then measure this point from the bottom of the steerer. This way you don't have to subtract head-tube length, head-set stack height, spacers and stem height.
I think he's considering swapping out his current stem, so he just wants to know how much of a difference it'll make by putting in a new stem.
moxfyre is offline   Reply With Quote
Old 02-21-05, 11:49 AM   #5
BillyBob
Senior Member
Thread Starter
 
Join Date: Jul 2004
Bikes:
Posts: 462
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by moxfyre
Yep, I ran the numbers through my calc. Looks like you've got your trig right.
Thanks. I had to put myself through a Trig refresher course last night!
BillyBob is offline   Reply With Quote
Old 02-21-05, 11:52 AM   #6
BillyBob
Senior Member
Thread Starter
 
Join Date: Jul 2004
Bikes:
Posts: 462
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Thanks 531Aussie. This information will come in quite handy for my another project that I am looking at.
BillyBob is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off



All times are GMT -6. The time now is 08:32 PM.