Chain stay length help please?
 

I am using BikeCAD (free version) to design the basics of a single speed trail bike that I'd like to build. I am only laying out the primary dimensions in a profile view so that I'd have a somewhat realistic starting point for discussion with a frame builder once I choose one.

How long must a steel chain stay be to accomodate a 26 inch (559) x 55mm tire while running a 42T chainring on a 68mm BB?

It's easy enough for me to position the virtual rear wheel anywhere I like, but I know that there would need to be some length for the bends to create the needed clearance as the stays come off of the bottom bracket.

Thanks for any advice or comments.

The freeware RattleCAD does this automatically.

A lot depends on what you intend to use for chain stay tubes. Most commercially made chain stays tube work well with 17" stays and 26" wheels.

OP; The finished length is only one of the variables... recommend looking at some of the specific CS's offered (see the builders suppliers section for MTB oriented CS's). The type and degree of bend(s), the type of dropout, width of the BB, etc., all come into play. Then model it as top down view to see if if might fit. Having an actually wheel with the tire mounted can also be very helpful in visualizing it. BTW; if you screen capture the pix of one of the MTB CS's and then print it out (with the aspect ration locked) full size you can check it with the real wheel. All else aside, sometimes it makes sense to put a bit more bend in them.

Hope that helps
/K

Thanks guys, that helps.