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P-38 Frame

This is my first post here. I have questions about the P-38 frame. I understand that the length of the boom tube is 9" on the L frame and 10" on the XL frame. Is there a structural difference between the frames other than this? For example, is the diameter or length of the frame tubing different in some other way? Can a longer boom be purchased to use on a L frame for a longer Ex-seam rather than going to a XL frame? What is the longest boom length available for purchase? Thanks for your help.

Hi webwest -

First go to the Lightningbikes.com site, and then scan the "how to buy" and then the "fitting" area. You can find some information that might help. Briefly, the four different frame sizes differ in a variety of ways above and beyond the length of the front tube that the crankset boom slides into. The standard length crankset boom is 7.5 inches long, while the extended length boom is 10.5 inches long. Tim Brummer suggests picking a smaller frame with a longer boom if you are slender, long-legged, and not very powerful. The bike will be a little lighter than the larger size, but will have a longer unsupported crankset. There is a tension between two goals: getting the lightest bike possible, and getting the stiffest bike that will best resist crankset deflection when cranking very hard. My advice: get on the phone with Brummer and discuss your individual case. He has been building and selling the bikes for close to 35 years, and if anybody can give you expert advice regarding fit it is him.

Safe riding,
Joel

These three prevent most accidents: seeing, being seen, & (usually) common sense.

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