Check my stem math

[sbornia]

I've read some archived posts here and on BF about how to calculate changes in rise and reach from one stem to another. How does my math look to you:

On a bike with a 73-degree HT angle, a 110mm x 84-degree stem (-6) will have 21mm of vertical rise (above horizontal) and 108mm of effective horizontal reach.

Rise = 110 * SIN(11 degrees) = 21
Reach = 110 * COS(11 degrees) = 108

If I were to swap this stem out for a 110mm x 73-degree stem (-17), all other elements remaining constant, my bars should drop 21mm vertically and the horizontal reach should blip out to 2mm to 110mm.

Rise = 110 * SIN(0 degrees) = 0
Reach = 110 * COS (0 degrees) = 110

Did I do all of this correctly? TIA for looking.

[TimD]

Have Bike CAD calculate it for you.

http://www.bikeforest.com/CAD/bikeCAD.html

Visualization included, no extra charge :)

[BdaGhisallo]

PM me your email address and I will send you a great Excel sheet that will work it all out for you - easy peasy!!

geoff

[the unjet]

Here's a much simpler stem rise calculator-

http://www.hammerheadbikes.com/docs/stemcalculator.xls

[sbornia]

Here's a much simpler stem rise calculator-

http://www.hammerheadbikes.com/docs/stemcalculator.xls

Excellent, thanks. Confirms that my math was right.

[BdaGhisallo]

Funny... that was just the spreadsheet I was going to send!

[the unjet]

I bookmarked it a long time ago, probably from another post on this board. It does come in handy.