A couple of questions. I've got a Trek 800. What is the BB size of this thing? I have a frame maker that will build a recumbent trike with a 26 inch rear wheel. I want to transfer most of my components from my mountain bike to the new trike fo save cash.
How do I figure out the BB size?
My rear wheel is only 130mm spacing (6/7 sprocket cassette). The new framr will be 135mm(8/9 sprocket cassette) I will have to get a new rear wheel. Will my current crank set work with a 135mm? Particularly chain size?
You need a new bike
To find out the BB size, remove the crankarms and measure the width of the BB spindle. A dial caliper is the best tool for this.
You do not neccessarily need a new wheel. You can use spacers to widen the width of the wheel. If you use a quick release, you will also need a longer axle.
Whether the crankset will work depends on the chainline of the new frame. This is dependant on the BB spindle length on the drive side and the position of the chainrings relative to the end of the spindle. This is something you need to discuss with your framebuilder.