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Waldo
01-28-2008, 07:28 PM
FSA labels their 110bcm chainrings 50/34, 52/36, etc. Why? Does this mean that a 50-tooth ring labelled 50/34 is incompatible with a 36?

Dave
01-28-2008, 07:58 PM
The big ring is ramped and pinned to shift best in the listed combinations.
Although there is some difference in the ramps, I doubt that switching from a 34 to a 36 would cause serious problems, just not as perfect as the matched set.

Grant McLean
01-28-2008, 08:42 PM
Campagnolo and Shimano also label their rings this way too...
...for the reason Dave pointed out...

"compatible" isn't an on-off switch, there is a range of what works ideally,
and what you can still get away with. It's about tolerances.


-g

fixednwinter
01-28-2008, 08:56 PM
I'd agree with Dave and Grant - it's more a range of tolerance and not an on/off thing.

I started with a 50/34 on my FSA SLK MegaExo, and found the 34 was too light an inner gear. Switched to a 36 without finding a 50 marked "50/36".

Shifting is good, but isn't quite as precise as when it was matched with the 34. I find this noticeable on trying to shift from the 36 to the 50 while under load.

stevep
01-29-2008, 06:52 AM
ps
i find they all work aok.
i use freakin suntour rings on a da10 bike and they shift fine...
they even "get machined" on the back w/ ramps after awhile.
dont worry about it.

anything now works multiple times better than the best stuff 30 years ago.

eg.
cheapest trashy shimano atb stuff works , say, 50 times better than nuovo record in 1975.
its like the richter scale in earthquakes.

hmmm, the new ultegra stuff ranks as a 175.
means it works 175* times better than nuovo from the past.

* but it looks 175 times worse... esp the crank.