Comments on: Stem Chart Tool

By: Greg Weiner

Greg Weiner — Sat, 09 Feb 2008 01:14:09 +0000

Awesome tool Alex! Using your tool I can see that a Nitto Periscopa will place the bars exactly where a Salsa P7 would. Since those aren”t made any longer and go for big bucks on eBay I”m glad to see the inexpensive (yet high quality) Periscopa will fit the bill. Thanks for the time and effort it took to put it together.

By: AlexWetmore

AlexWetmore — Wed, 28 Nov 2007 23:21:04 +0000

BikeCAD (google it, I don”t remember the website) is also great for messing around with this stuff. It”ll let you draw out an entire frame and can determine trail and other geometry for you. You can also offset the handlebars from the bottom bracket and it will compute the right stem to use. There is a free version that is good.

By: Jimmy

Jimmy — Wed, 28 Nov 2007 22:47:39 +0000

Thanks! A quick google after I asked the question also turned up this:
http://www.kreuzotter.de/english/elenk.htm
Also, this one, which seems to be for motorcycles, but should work anyhows:
http://www.papkegroup.com/superbikeengco/superbikesupensionkinematics1.html
This one is from some recumbent site, and includes provisions for approximate center of gravity, etc. Haven”t played with it yet to see how it actually works out for upright bikes.
http://www.recumbents.com/wisil/trail.asp

By: AlexWetmore

AlexWetmore — Wed, 28 Nov 2007 22:02:06 +0000

Jimmy — http://www.kogswell.com/trail.php is what you want.

Rex — Spacers can be important to consider if you are changing to a stem with more rise. The first graph shown shows that my stem goes up by 26mm, but I only wanted about 20mm of rise. So lowering the spacers by 6mm brings me right to the correct location.

By: Rex Kerr

Rex Kerr — Wed, 28 Nov 2007 21:55:09 +0000

I was recently in the market for a new stem to fit a bike for somebody else and created an Excel spreadsheet for the same thing. I neglected to consider spacers since I usually end up working with pre-cut steerers and almost never want to go down, so mine just calculates the difference in height/reach when given head angle and stem length/angle. I like the graphical approach though.

By: Jimmy Livengood

Jimmy Livengood — Wed, 28 Nov 2007 20:17:02 +0000

Nice! Is there one for head angle/fork geometry that exists? There are probably plenty of people like me who have an existing bike/frame and are considering a new fork. I have a couple of CAD type programs that I can draw it all in, but a little tool like your stem tool would be neat. And probably a lot of work, too.

By: James Moore

James Moore — Wed, 28 Nov 2007 18:44:01 +0000

Hi Alex, thanks for making this tool. I”m sure it will come in handy. I”ve linked to it from my brand new (like less than a week old) free bike tools site. I also linked to your great series on rack building. Thanks for taking the time to put all of this online!