I’ve been riding Campy for ages, but recently got a SRAM Force equipped bike (used). I’ve noticed that, if I look down at the chainrings from above, the chain/rings wobble slightly side-to-side as I pedal; it’s like the rings aren’t precisely planar, but rather bent. It’s only maybe 2-3mm of movement, which isn’t much but is enough to cause a bit of rub on the front der. in certain gear combos.
Oddly, it seems that the wobble is visible in both small and large ring, which makes me think that it’s not that the rings is bent; if anything it seems like the crank itself is slightly off-kilter. So, is this a normal feature of this group (maybe helps with shifting between big and small ring?) I don’t see similar wobble with my Campy cranks…
Are the Campy cranks you mention for comparison on a different bike, or swapped out from the same frame? Could be BB/frame flex is a confounding variable. I definitely notice more deflection in my 8-speed trainer bike (round steel tubes) compared to my newer carbon frame w/ 10-spd external bearing crankset. I’d say the rings are less likely the main source of deflection, although they probably do contribute a little.
Did you buy it off of ebay from china? If so, it’s probably a second from the factory that goes to a clearinghouse for cheap sale. I bougth one a few years ago from China and it had the exact same wobble you are describing. I got a grweat deal on it so I’m not complaining, it’s a little annoying, but it works.
Have you tried retightening the crank bolts? often times that wobble can be caused by the crank not being fully tightened to the axle (depending on which model of cranks)
I tried installing cranks on a couple different bikes to see if it was a frame issue; it’s not, I always see the wobble, and no wobble with Campy bits on same frames. Also, I’m seeing this with the bike on a repair stand just turning the cranks, not under power, so it’s not frame flex.
Cranks bolts and chainring bolts are all tight; this is the Force crankset that has the BB spindle attached to the driveside crank, so don’t see how it could be a loose bolt causing the misalignment.
I should mention that at the moment these cranks have a 54t FSA TT ring on them; I have the original Force outer ring, I’m going to install that and see if I see the same thing. As I said, though, I see wobble on the inner ring too, so I’m thinking it could be an issue with the cranks/spider themselves, i.e. spider is not perfectly perpendicular to spindle.
As I said, these were on a used bike I just picked up; bike was from a buddy of mine who got it via a normal US-based shop, not some dodgy Hong Kong back-alley deal. I think they may be first-gen Force components though, so maybe some of those early parts had some QC issues (?)
Good thought, I’ll try that. Could be a bit tough to see, as it’s just 5 arms rather than a whole ring… but I have some old rings that I know are straight, I’ll stick those on and check.
So I guess the short answer is that this wobble is not a normal “feature” of SRAM cranks!