I have a Bianchi Record 848-12v - 1984. I am using this bike with some upgrades for triathlons this year. The original freewheel is a 6 speed - 14-21. This was working fine as I live in a very flat area. However, I am racing Muskoka 70.3 in a Sept. I recently upgraded to a 7 speed 13-28 with a 37 tooth high gear - very cheap on ebay.
Anyway, I had the LBS install it on the wheel, however, when I have been out on rides anytime I put it into the 13 the chain will randomly jump/skip (not sure exactly how to describe it) It appears that the more pressure I put on the pedals the more it will skip.
I tried moving the derailleur limitiing screws but I could not notice a change - possibly because of my lack of bicycle knowledge.
If anyone has any ideas that I could test out on my own I would greatly appreciate it.
Depends on how worn the old freewheel and chain are vs the new freewheel… They tend to wear together so if you change one (FW in this case) it may not mesh properly with the old chain. Answer is typically a new chain; however, that’s for folks usually replacing old gear w/ brand-new gear. If you’re buying used, there’s also the possibility that the ‘new’ FW is actually in worse shape than the previous so a brand new chain may not mesh cleanly either. (not bagging on eBay as I buy older stuff there too, but that’s just the nature of the beast dealing w/ vintage parts.)
Thanks for the reply. The new freewheel from ebay is new never mounted. I measured the chain and it doesnt seem to be too stretched out, not sure how worn out it is. But if it was worn out wouldnt it be skipping in all the gears not just the 13?
Make sure the limit screw lets you get all the way over to the center of the 13 cog. With the shift lever all the way forward, spin the cranks and look from behind at how the chain leaves the rear derailleur and meshes with the FW; if there is a problem, it should be visible.
Just to confirm, you are running friction (non-indexed) shifting? Parts in 1984 were not tolleranced for the even spacing needed to make indexed shifting work.
Thanks for the reply. The new freewheel from ebay is new never mounted. I measured the chain and it doesnt seem to be too stretched out, not sure how worn out it is. But if it was worn out wouldnt it be skipping in all the gears not just the 13?
Yeah, perhaps it’s something else. I’d probably expect a worn-out chain to skip in other gears too then, but on the other hand that might not necessarily be the case since the chain angle is less acute in the other gears than in the smallest/outermost cog and the chain should also be engaged across a larger surface in the other cogs. Just a thought…
Throw the bike on a rack,shift to the smallest cog, turn the “H” screw cw till the derailleur starts to move inward, maybe even till the chain jumps to the 6th cog, then back ccw till it falls and quiets on the smallest cog. If you mucked with the “L” screw, you might want to check inner travel and make sure it can’t fall of inside. You still might want to try a new chain (once you are satisfied that the der alignment is good), as the small cog has the least “wrap” and is most susceptible to suffering slip with a stretched chain.