Are my teeth getting old?

slogfester · Post by **slogfester** » 18 Nov 2015 03:15

Apologies upfront to the likes of Mr Weaver, who need to look away from the following photos. Hard to believe I know, but I did clean these bits up before photoing them

Do I need new chain rings? I'm not sure how many km they have done. Possibly 15 000 +. Its a compact DA 7800.

Thanks, and greetings from DownUnder

Philip Whiteman · Post by **Philip Whiteman** » 18 Nov 2015 09:28

By looking at the bottom picture, the answer is a definite 'yes'. Sharks fin teeth indicate a replacement.

AlanW · Post by **AlanW** » 18 Nov 2015 11:58

You cleaned them first!!! May l suggest a quick visit to Specsavers?

slogfester · Post by **slogfester** » 19 Nov 2015 03:19

The shape of the teeth looked fine until I cleaned them

dweben · Post by **dweben** » 19 Nov 2015 23:27

Is it slipping? If no then nah

Run to failure!

Philip Whiteman · Post by **Philip Whiteman** » 20 Nov 2015 08:28

dweben wrote:Is it slipping? If no then nah

Run to failure!

But it will wear the chain more quickly.

George · Post by **George** » 20 Nov 2015 09:38

What I find curious about this is that, in the picture where you can see the whole chainring, the teeth at roughly 2 o'clock to 3 o'clock look quite worn, while the teeth around 6 o'clock don't look very worn at all.

I tend to run the chain rings on my winter bike until I can 'feel' the wear (chain gets a little loose on the ring and you can feel it as you pedal, particularly at a high-ish cadence). At that point, I bit them and fit the slightly worn rings off one of my good bikes, then buy new ones for that bike.

George · Post by **George** » 20 Nov 2015 09:48

Also, Barry, you are clearly not riding up enough hills (or you are riding up them Museeuw-style), since your little ring looks unused.

AlanW · Post by **AlanW** » 20 Nov 2015 10:14

George wrote:What I find curious about this is that, in the picture where you can see the whole chainring, the teeth at roughly 2 o'clock to 3 o'clock look quite worn, while the teeth around 6 o'clock don't look very worn at all.

I think that it is down to the design to aid and assist in changing gear George.

George · Post by **George** » 20 Nov 2015 10:28

AlanW wrote:
George wrote:What I find curious about this is that, in the picture where you can see the whole chainring, the teeth at roughly 2 o'clock to 3 o'clock look quite worn, while the teeth around 6 o'clock don't look very worn at all.
I think that it is down to the design to aid and assist in changing gear George.

So the 2 o'clock teeth aren't badly worn? That's how they start out?

AlanW · Post by **AlanW** » 20 Nov 2015 10:57

George wrote: So the 2 o'clock teeth aren't badly worn? That's how they start out?

Its hard to say to be honest from the photo, but if you look at a new one you'll see that nearly every tooth will have a slightly different profile.

Gone of the days when every tooth was machined the same and you could tell straight away when they were worn coz they were clearly hooked over.

I had the same problem a few months ago, I had fitted a new chain and cassette but the gear changing still wasn't as sweet as I expected it to be. I honestly couldn't tell if the front chain ring was worn or not, despite knowing that it had done thousands of miles. So cutting a long story short, I bought a new chain ring (@ £80.....!!!) and it cured the "problem".

George · Post by **George** » 20 Nov 2015 11:17

Interesting. I don't use Shimano, so I'm not familiar with their tooth profiles. Campag and Stronglight do shape their teeth to assist shifting (e.g. flutes and some shorter teeth), but none of mine have that 'shark-tooth' shape.

petemarshall · Post by **petemarshall** » 20 Nov 2015 13:16

None of my recent Shimano rings have sharks fin profiles.
The teeth of Shimano outer rings are slightly off set from one another but not hooked like a sharks find, that is a sign of wear.
I would be very unhappy if a ring started to sharks fin at 15,000 usually a sign of inadequate maintenance although why they have only gone in one place is a little strange. Maybe to long a chain?
I think ultegra outer rings are forged alu rather than pressed, so they should wear better although I can't see much difference on the 105 over the ulegras I have (the ulegras do look better though ).
Replace the outers with stainless steel ones and they will last forever at a weight and small shifting penalty. Not for racing but good on touring bikes. I have an ancient Shimano 600 triple crankset on my tourer that has TA stainless rings throughout, still shiney and no sharks teeth after god knows how many kms in the last 20 years. Weighs a ton though

Post by **CakeStop** » 20 Nov 2015 18:17

I nearly fell for that recently when deciding my middle ring needed changing and I noticed some odd looking teeth on the big ring. Luckily I spotted odd teeth on a photo of a brand new chainset. It is indeed meant to give the chain an easy route off the ring in question.

AlanW wrote:
George wrote:What I find curious about this is that, in the picture where you can see the whole chainring, the teeth at roughly 2 o'clock to 3 o'clock look quite worn, while the teeth around 6 o'clock don't look very worn at all.
I think that it is down to the design to aid and assist in changing gear George.

slogfester · Post by **slogfester** » 06 Dec 2015 04:46

Umm... confusing. Canvassed mates here DownUnder (by taking the rings down the local café!) and opinion was roughly 50:50! So then I took them to a couple of LBS and whadya know? One said change, the other said fine.
Seems to be a bit of a maintenance dark hole exasperated by the pre-cut unequal teeth.

And yes George, big ring only on anything less than 10%