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Anyone know size of downtube on mid-80's Trek 1100(3 posts)

Anyone know size of downtube on mid-80's Trek 1100cdlynx
Apr 9, 2003 9:20 AM
I'm updating my 'winter-ride' to Shimano RSX STI. I don't know the downtube size clamp to replace the front der. Thanks, david
you mean the seat tube...C-40
Apr 9, 2003 10:59 AM
Probably 1-1/8" or 28.6mm. But why don't you measure it?

An adjustable wrench makes a great caliper for measurements that don't require a lot of accuracy. Just adjust it to fit the tube and measure the opening with a ruler.

Another method is to measure the circumferance with a piece of tape or paper and divide by 3.14. A 1-1/8" tube will have a circumference of about 3-1/2" and a 1-1/4" (31.8mm)tube will be 3.92 inches.
re: Anyone know size of seat tube on mid-80's Trek 1100cdlynx
Apr 9, 2003 12:13 PM
DOH! meant seat tube.