I wasn't sure where to post this but it seemed to be more of a frame builder question than a mechnic question so I thought I'd try it here first.

I've got a 1990 Trek 700 frameset with the chrome-moly main tubes and the hi-ten fork. The 730 of that year came with a chrome-moly fork. I can get a chrome-moly fork that is a nearly exact replacement for the original but I'm wondering just how much of a difference in weight, comfort and strength it would make to replace the hi-ten with chro-mo. The reason I ask is that the original fork received some cosmetic damage last summer and I'm looking at repainting it (too much damage for a decent touch up, but LBS says fork is structurally fine). I can upgrade to chro-mo for about $60 but I'm wondering if it is worth it.

Thanks

Hi-ten has a lower yield strength than chromoly, so for the hi-ten fork blades to resist permanent bending in a collision for example, the wall thickness for blades of similar outside dimensions would have to be thicker (and therefore heavier) for a hi-ten fork than for a chromoly fork. Also, because the hi-ten blades have thicker walls, the fork won't have the flexibility and resilience of a chromoly fork.

IMHO, for $60 it would be a worthwhile upgrade.

The variation in tube thickness tends to be that the tube needs to be twice as thick in order to be the same strength, but that does not mean the whole thing will weigh twice as much, due to the weight of other common components and whether design wise strength is the governing design factor, and depending on how much of the upgrade fork is upgraded to chromo at a lower weight.