Author Topic: Temporarily resurrecting front chainring (Read 2724 times)

OnaRaleigh · « **on:** 22 March, 2019, 08:05:24 pm »

OK, I have a new chain and a new freewheel, but these have made me aware that my front chainring is worn out. The chain keeps jumping off. This is an old 10 speed, and I replaced the whole front chainset at least 20 years ago. And that wasn't a new one.

My question is, as it is going to take some time to get a new chainring, could I file down the valleys between the teeth and get a few more miles out of it? Has anybody done anything like that?

Cheers,

I need my bike back!
Peter

PS my backup (guest ) bike is a bit smaller and not so comfortable to ride (for me).

Brucey · « **Reply #1 on:** 22 March, 2019, 08:22:29 pm »

if you file the valleys the 'new teeth' won't match the pitch of any known chain. So that is a non-starter. If the teeth are hooked then they can be de-hooked using a file.

Usually the teeth are most worn at the three-o'clock and nine o-clock positions, so turning the chainring on the spider can present 'better teeth' to the chain where they are most loaded. But if they are worn down enough, the chainring is toast, simple as that.

cheers

OnaRaleigh · « **Reply #2 on:** 22 March, 2019, 08:26:09 pm »

Thanks for that quick reply. it is a five bolt chainring and I tried turning it one move, but that didn't help. I had noticed that some teeth are worn more than others.

Cheers,
Peter.

andrew_s · « **Reply #3 on:** 22 March, 2019, 08:38:01 pm »

A chainring that's over 20 years old may pre-date Shimano's easy shifting modifications and have had full-size teeth to start with.

Try turning the chainring round, inside face to outside, so the the un-worn face of the tooth is doing the pulling.

Alternatively, can you "borrow" the chainring off the guest bike?

Crumbling Nick · « **Reply #4 on:** 22 March, 2019, 11:08:45 pm »

Been there, done that...
In my case it was the middle of 3 chainrings. I have a new replacement ring, but for reasons which are not relevant to this question, have chosen to file the teeth (twice

).
If you want to try it, you need to understand which part of the teeth needs to be modified. The chain sits at the bottom of the teeth. It will stay there unless the driving faces of the teeth which push the chain aren't radial enough. Think of an idealised tooth form, which is a circular arc at the bottom (to fit the chain rollers) & the upper part of the teeth is a series of straight radii. It wouldn't work in practice, but the geometry means that the chain contacts the ring on faces which are radial. That's the shape you need to work towards at the bottom of the teeth.

In the worshop you need to have a rat-tail file with the same diameter as the chain rollers; a couple of mm oversize shouldn't be an issue. The technique is to file circumferentailly on the worn faces of the chainring. I advise clamping the ring with the crank side facing you & the tooth you're filing horizontal (3 o'clock). Then file with pressure downwards, though with some bias (I can't quantify what I've done by feel, I'm afraid) towards the centre of the ring to counteract the file's tendency to wander towards the ends of the teeth. For my chainring, 3 or 4 strokes with the file was enough. That's a 9-speed chainset with thin teeth & it wasn't very badly worn. If you choose to tackle yours, which I suspect has full-width 3/32" teeth, you'll need more strokes. Don't overdo it, or you'll end up with a ring that doesn't want to let go of the chain at the bottom, commonly known as chainsuck, & tends AUI to trash the rear mech.

Finally, to reinforce what Brucey said, never file with pressure towards the centre of the chainring.

rogerzilla · « **Reply #5 on:** 23 March, 2019, 09:36:35 am »

You can just flip the chainring over if it has no ramps or lifting hooks (which are unlikely on an old 10 speed).

OnaRaleigh · « **Reply #6 on:** 23 March, 2019, 09:43:40 am »

Thanks for those replies. I am feeling quite grumpy this morning with my bicycle out of order.
I can't swap the chainring from the guest bike as it is a different bolt diameter (BCD?)
I'll have a look at your ideas of turning the chainring inside out, but am not hopeful about it. maybe it would give me a week or so until I get a new one. I have a feeling that the teeth are not in the same plane as the structure of the chainring so might be further out from the frame.

Thanks for the hints about filing, I'll try this other idea first, and then give it a go.

Maybe it's time for a new bike?
It used to be every time I got out on this bike I would say to myself It's great I don't need a new one.

Peter M.

Brucey · « **Reply #7 on:** 23 March, 2019, 10:02:05 am »

chains and sprockets are consumable items, like tyres more or less. If you let a chain wear too much, it quickly destroys the chainrings too. Chains and sprockets are cheap and readily available, chainrings somewhat less so, especially if they are old; manufacturers change chainring bolt patterns, seemingly on a whim, from time to time.

If you are in it for the long haul, it isn't a bad idea to get a new chainset which uses a commonly available chainring fitment. This way you ought to be able to get chainrings for years to come. Changing the chain and sprockets before they are badly worn greatly reduces the wear on the chainrings; even soft aluminium chainrings will last ~15000 miles and steel or harder aluminium chainrings can last about 40000 miles.

cheers

OnaRaleigh · « **Reply #8 on:** 23 March, 2019, 02:25:05 pm »

Thanks all for your suggestions. I have turned the chainring around as suggested and it doesn't jump anymore or throw the chain. It wasn't as I thought with the teeth on a parallel plane. It's just that they were thinner than the main part of the chainring. Sorted. I'll still order the new chainring as I don't see this as a long term solution.

Next time perhaps I'll do as Brucey says and replace the whole lot.

Cheers all, I'm out for a ride.

aidan.f · « **Reply #9 on:** 25 March, 2019, 10:38:19 pm »

Checkout Spa cycles for replacements.

zigzag · « **Reply #10 on:** 26 March, 2019, 08:06:01 am »

on chainrings only one part of the tooth takes the load, so if it is flipped over this will essentially double it's service life. i've done this on my ss hack bike (simple chainring with no ramps, five chains worth of wear) and it felt like new.

OnaRaleigh · « **Reply #11 on:** 26 March, 2019, 08:36:42 am »

Thanks again for your replies. Spa cycles didn't have my size,
but as Zigzag says I turned it around and it is like new. That takes the pressure off.
I am currently waiting for a reply from hilarystone.com about a 52t 144BCD chainring.

cheers,

rogerzilla · « **Reply #12 on:** 28 March, 2019, 09:24:58 pm »

They're common as muck in 1/8", 144mm being the most common track BCD, but presumably you want 3/32"?

DuncanM · « **Reply #13 on:** 29 March, 2019, 08:58:40 am »

There are loads on eBay because it's an old Campag standard. There's a bit of NOS Campag tax though.

Brucey · « **Reply #14 on:** 29 March, 2019, 11:49:00 am »

in the grand scheme of things there have probably been x1000 or more 3/32" rings in 144BCD made vs 1/8" rings in the same size. Brands that made chainrings of this type included

campagnolo (NR, SR, GS)

S.R. (e.g. Royal, some 'apex' models NB the commonest Apex models used 118mm BCD or something)

Gipiemme

miche

Zeus

Sun Tour

Sugino

Tevano

Stronglight

and there will have been others too.

As duncan suggests, there are lots of these chainrings on e-bay, often poorly described, so no mention of '144mm BCD' . However if you know what you are looking at, you can usually tell a 144mm BCD from others simply by looking at a photo of it and comparing with another. The closest common BCD size is 135mm, and even those look quite different from 144mm rings.

https://www.ebay.co.uk/itm/Vintage-French-Stronglight-Vitus-992-979-chainring-52-teeth-144-BCD/392263668781?hash=item5b54bc942d:g:JEkAAOSwInJcm-Gt

cheers

mzjo · « **Reply #15 on:** 30 March, 2019, 05:38:05 pm »

I should have one of those and I don't use rings of that number of teeth any longer. I will check and you can have it for free, if you want it. Not sure if it will be a 52 or a 54 and it will probably claim Poulidor in its ancestry (as does everything vélo in Limousin).

mzjo · « **Reply #16 on:** 30 March, 2019, 08:00:54 pm »

Garage checked. I have a 52 and a 53t in 144bcd. They are not in bad condition, the 53 marginally better than the 52 (you have to look hard to see where the teeth have worn). Both Campag but don't ask me what model. If you want one PM me and I'll post it. Photos available on request.

I also have a 53t in a humongous great bcd. I don't know what Campag it might be but the adjacent holes are at about 89.5mm (144mm is 84.7mm adjacent holes). Any ideas; anyone? I think this is the one claiming Poulidor ancestry and the donor (a past club president) had family connections to St Léonard so it might just be true.

OnaRaleigh · « **Reply #17 on:** 30 March, 2019, 09:36:48 pm »

Thanks MZJO, I have just paid good money for one from hilarystone. If something goes wrong with that order, I would like to come back to you on that. Unless of course you are in South Dorset and I can just run over and pick it up.

Thanks for the offer.

Regards,
Peter M.

Brucey · « **Reply #18 on:** 30 March, 2019, 10:11:48 pm »

Quote from: mzjo on 30 March, 2019, 08:00:54 pm

I also have a 53t in a humongous great bcd. I don't know what Campag it might be but the adjacent holes are at about 89.5mm (144mm is 84.7mm adjacent holes). Any ideas; anyone? I think this is the one claiming Poulidor ancestry and the donor (a past club president) had family connections to St Léonard so it might just be true.

if it is 88.8mm spacing five-bolt then it is almost certainly a pre 1967 campagnolo record chainring with 151mm BCD. IIRC the shoulder diameter is the same as the later (Nuovo record) 144mm BCD chainrings. Some early Dura-Ace track chainsets used this arrangement too.

TA adaptor chainrings used a 152mm BCD but these were (I think) all six-bolt rings.

53T 151BCD campagnolo record chainring

53T 144BCD campagnolo Nuovo record chainring

cheers

mzjo · « **Reply #19 on:** 31 March, 2019, 01:18:04 pm »

Quote from: OnaRaleigh on 30 March, 2019, 09:36:48 pm

Thanks MZJO, I have just paid good money for one from hilarystone. If something goes wrong with that order, I would like to come back to you on that. Unless of course you are in South Dorset and I can just run over and pick it up.

Thanks for the offer.

Regards,
Peter M.

No problem, they've been sitting in the pile of bits for over 20 years so they won't be going away any time soon. South Dorset is a bit of a swim from me (although the UK mps seem determined to change that!) but the post works very well.

Quote from: Brucey on 30 March, 2019, 10:11:48 pm

Quote from: mzjo on 30 March, 2019, 08:00:54 pm
I also have a 53t in a humongous great bcd. I don't know what Campag it might be but the adjacent holes are at about 89.5mm (144mm is 84.7mm adjacent holes). Any ideas; anyone? I think this is the one claiming Poulidor ancestry and the donor (a past club president) had family connections to St Léonard so it might just be true.

if it is 88.8mm spacing five-bolt then it is almost certainly a pre 1967 campagnolo record chainring with 151mm BCD. IIRC the shoulder diameter is the same as the later (Nuovo record) 144mm BCD chainrings. Some early Dura-Ace track chainsets used this arrangement too.

TA adaptor chainrings used a 152mm BCD but these were (I think) all six-bolt rings.

53T 151BCD campagnolo record chainring

53T 144BCD campagnolo Nuovo record chainring

cheers

Campag and the pre-67 bit matches the chronology. I don't have a crank to fit it to, needless to say.

I used to have a TA adaptor ring crankset but that was on a bike that got stolen in 1978! Pity, I was very fond of it.