Advice please !
On my Cannondale CAADX, with the stock FSA Gossamer chainset and rings if I sprint hard I quite often drop the chain to the outside - potentially could cause a crash, especially in a bunch spring. It's happened a few times now and I tried and replicated it today on the way home as a test - gradually wound up the power and at about 1,100 watts it jumped.
This has never happened on my Giant Defy, despite pushing a lot harder.
I've checked the front mech adjustment and it's good, so I suspect either damaged (bent) teeth, chainset / ring flex or frame flex.
If it's anything but frame flex I'd be tempted to swap to a 105 or Ultegra Chainset, but of course it's a waste of money if it;s the frame flexing.
Any experience or thoughts ?
I reckon it's the ring, a fair few pros used the bogo gossamer cranks as they were less flexy than the SLK carbon ones at the time, namely Cancerella.
1100 watts isn't a huge amount in a full sprint
I'd be looking at wear and damage first.
Big ring tight - chainring bolts ok?
Chainline?
Is it a press fit BB? Is everything aligned?
I'd be looking at a bent or worn chainring first.
'Dales hardly have a reputation for flexing unless its borked.
Have you checked every chain ring tooth and every chain link for damage/bend/twist and also lifted the chain while on the chainring to see how baggy a fit it is?
Thanks for the input !
In no particular order:
Bolts are tight
Chainline looks good
Chain wear minimal (quite a new chain - it did it on the old chain too)
I can lift the chain about 2 mm (maybe 3) off the chainring - hmmm, possibly a bit baggier than I'd like.
Teeth are a bit more worn than I'd like, and possibly some damaged ones too...
Looking at the chainset and rings, they do both look rather spindly.
So - either a new chainring or chainset (prefer chainset as it's got CX ratios on it now).
Any 105 bargain compact chainsets out there (and the adaptor needed to fit to the BB30 BB of course) ?
I had something similar a while back. On a testing bike with Dura Ace cranks. Rings were 53/48 so close coupled. Found when changing up from 48 to 53 that chain was jamming. Cost me a couple of wins!!!
No obvious wear to be seen. Dura Ace won't flex. Steel frame. I changed both rings and problem went.
Reckon you should try new rings - both - as a starting point.
You haven't said that the teeth/links are all straight.
I'd be looking again at the f mech if they are.
Don't see how sarawaks comment is relevant.
The teeth appear straight"ish" which isn't good.
It's either new chainrings or a new chainset - depending on cost differences (looks like rings as in addition to a chainset an adaptor is needed)
cynic-al I take sarawaks comment to indicate that he/she has experience of subtle chainring issues causing problems, so useful input to my problem
next question: where to buy a good, affordable 110bcd 5 bolt 34/50 chainring pair?
ps -links all straight. plus has done this on two chains
https://www.rosebikes.co.uk/shimano-105-fc-5750-chainring-489214
https://www.rosebikes.co.uk/shimano-105-fc-5750-chainring-489225
Would be good options.
Will definitely be the rings, from the sounds of it. Those FSA rings don't last and a new chain will have only made it worse.
The a full chainset with a wheels manufacturing BB would be the best option, but a lot more money. Make sure you get the right BB for the shell width.
Edit: BTW, those are 10sp rings, but will work fine if you're running 11sp.
Worn teeth would be my guess.
Upload a picture?
Stronglight are probably the most affordable decent quality 110mm chainrings you'll find.
I probably wouldn't bother buying new chainrings for the FSA chainset though but instead just buy a complete 105 chainset for £60 online.
Possibly add a new chain to that depending on how worn your vague "quite new" definition actually is.
Teeth are a bit more worn than I’d like, and possibly some damaged ones too…
a pic of the worn chainring would have been handy.
I probably wouldn’t bother buying new chainrings for the FSA chainset though but instead just buy a complete 105 chainset for £60 online.
Agree, chainring prices tend to be very high compared to buying a complete chainset although in this case (FSA to Shimano) would also need a new BB.
Agree - replacement chainset looks like a better idea.
£90 for an R7000 from Evans after BC discount, work gift cards and price match. 5800s are only a bit cheaper once I find the actual spec needed (the £65 ones are the wrong colour / ring sizes / length).
What about thre £59 ones
you're kind of a bit of a man of mystery when it comes to saying what you run/want
Ah, sorry I thought I'd written the spec somewhere further up the thread - obviously not.
I'm looking for a Shimano 105 - 175mm crank length, 34-50T rings, in Black.
The bike has a BB30 bottom bracket, so I'll need an adaptor of course.
Geex - Where are the £59 cranks from - I'd definitely like that.
I’m looking for an actual 105 by the way - the bike is a long term “keeper” so don’t mind the £30 extra unless there is a cheaper 105 of course
