Warped Chainring

[crossfire]

Actually the large chainring (48 Teeth Shimano) appears warped. fitted a chainset (44,32, 22 Sunrace) but found I was spinning out so changed rings to 48, 36, 24, which worked but caught the side of the FD. Yesterday I changed the FD hoping to cure it but still catching. On looking from the front wheel with chain off there appears to be a warp where the crank arm is. The 48 tooth ring has a metal stud sticking out towards the crank arm, and I am thinking this could be the problem. Do I need it? I am presuming it is to prevent the chain getting stuck between ring and crank but as chainring is fitted with chain guard, I don`t think this possible. The ring was taken off and lies flat on my steel bench with no hint of a wobble, so I was thinking of cutting the stud off or at least grinding it down, could move it round by one bolt to check I suppose. 8 speed rear cassette, 48 tooth ring is 9 speed, but surely that would be no problem. Otherwise silent rides until I change to the big ring, moving the ring across the FD gap just changes which side gets rubbed.
Hoping for a solution as I can`t keep using middle and low chainrings only.
John

 

[Smokin Joe]

If the ring is not warped then look at the other two and check if they have the same wobble. If not the only thing I can think of is maybe you had a small bit of grit between ring and spider at the mounting point. Clean both surfaces and try again. If the other rings also run out of true it is probably a bent axle or spider arm.

Removing the anti-drop pin will make no difference.

 

[Ian H]

The chain-catcher studs come in different lengths. Yours might be too long for your crankset, and thus pushing the ring inwards. Either remove it (it unscrews), or shorten it with a hacksaw.

 

[Ajax Bay]

Does the chain-catcher stud touch the crank? If not as Joe said: irrelevant.
The first action I'd take is to remove and refit the middle and large chainrings.
The second action I'd take is to remove the chainset (that side, assume square taper), give everything a good clean, the thinnest smear of grease and slide and secure back on.
Since the ring (48t) itself is not 'warped' the next deduction (assuming both actions above fail to remediate) is that the spindle is off true, possibly because the right hand side BB shell 'edge' is not perfectly faced (ie in a vertical plane).

 

[raleighnut]

If you took the crank off the BB it is very easy for it to not go back on 'dead square' DAMHIKT

 

[crossfire]

Thanks people for all the help. The stud does touch the crank, and as the ring only bends at this point I am blaming the stud. So todays job is to remove the ring and as per advice from #Ian H , unscrew it, then reassemble and try, all other rings appear straight - but then I am waiting for a cataract op!

 

[crossfire]

Update. Stud removed and now rotating freely with no rub, needs some minor fettling with L and H screws, and possibly move FD down a tad so I can use all 8 gears in low not just lowest 5 but that is minor and is not a gearing I use often.
Thanks for the help. Now for the next problem.......
John

 

[ColinJ]

I'm glad that you finally sorted out that bad-stud!

 

[C R]

Update. Stud removed and now rotating freely with no rub, needs some minor fettling with L and H screws, and possibly move FD down a tad so I can use all 8 gears in low not just lowest 5 but that is minor and is not a gearing I use often.
Thanks for the help. Now for the next problem.......
John

It may be worth filing down the stud so that it doesn't clash with the crank arm, and refitting it, it is in there for a reason.

 

[ColinJ]

It may be worth filing down the stud so that it doesn't clash with the crank arm, and refitting it, it is in there for a reason.

Indeed... I have trapped a chain between crank and chainring before now.

I was riding with alongside someone on one forum ride and noticed that he had his chainring turned round so the stud didn't align with the crank. I pointed it out to him and he asked what the stud was for. I'm not kidding - before I could reply, he dropped his chain and got it caught...

"It is to stop THAT happening!"

 

[Ajax Bay]

OP has a chain guard which will mitigate the risk of "that happening".

 

[ColinJ]

OP has a chain guard which will mitigate the risk of "that happening".

Good point, well made!

PS It was still a good story though!

 

[C R]

OP has a chain guard which will mitigate the risk of "that happening".

Missed that in the original post.

 

[crossfire]

Went for a ride yesterday and chainring was just touching, after a very minor turn of the L screw, silence has returned. Minor fettle necessary as derailleur was "reluctant" to engage small ring. New FD (Altus FD-M313-6) requires firm push and has a definite click when changed, much better than the previous one which was rather sloppy. Might go for a slowish ride tomorrow, through tree lined roads and the woods to check, avoiding that burning yellow thing in the sky

 

[crossfire]

After today`s ride, silence has returned, and all gears available. Did a 9 mile run down leafy roads and woods down into Caversham and across to Mapledurham - plenty of shade. Film crew gone from Mapledurham House, Bentley Productions were filming for something. Temp is now 31 at the BACK of the garage, so glad I went at 10