Cycling UK Forum

I was warned around 1500 miles ago that my larger chainwheel is getting worm and would need replacing when the chain is next replaced (probably in around 1500 miles). Also, I suspect cassette will be needing replacing soon because ...

Chainwheel done 10,000 miles
Cassette done 8800 miles
Chain done 3500 miles
(All standard Shimano stuff Tiagra or equivalent quality).

So question is, they are all working fine, no slipping. Given they all need replacing, is there any good reason to change them now or, given they are all wearing together and will all need replacing, any reason why I shouldn't just stick with them as they are all wearing together ?

And if there is no reason to change them despite their being worn (but together), what are the signs they are getting to the point of failure (as I'd rather change sooner than have then fail whilst out on a ride.

(I'm pretty inexperienced when it comes to bike engineering/maintenance so sorry for what is probably a daft question)

Ian

It's not a daft question. I don't know how worn it all is but unless it is very worn it'll probably go on a bit longer yet.

Reasons for doing something include

- you'll be wearing other stuff too (like derailleur pulleys)
- the transmission will lose efficiency once it is worn
- the chances of breakage increase as time goes on (although some new chains do break too...)
- if you change your chain and sprockets now, I'd expect your worn chainring to carry on a bit longer yet.

IME many people change their chainrings prematurely; unless it is terribly worn the worst that usually happens is that the worn chainring will be a bit noisy (for a while ) with a new chain.

So it could be that your choices boil down to;

- new chain and sprocket set, now, or
- that plus chainring and rear mech /rear mech parts, later.

I'd do the former but there are some that would do the latter.

cheers

yep, nowt wrong with doing that, many times in the past I've put a new chain, only to find its too late, Most folks would replace the lot, not me.......back on goes the old chain, and run it into the ground!......Thrifty.

If you carry on long enough, the chain rollers will eventually wear thin enough that they crack and fall off.

IIRC, the chain was between 7000 and 8000 miles old by that stage.

I'll have to own up here.

My hack bike needed a new transmission, I put it off to keep using it through the winter with the plan to replace everything in the spring. Well you know what's coming, spring came and went, then summer, autumn, another winter and I kept on riding it thinking I would just replace it when I had more time or something broke. After another 4 years I noticed that if it was wet the chain would start to make a horrible graunching noise especially in the granny chainring as if it was running dry with no lube. At this point I did replace everything but estimate I had gone another 20,000 miles without any noticeable problem. It was only a 7 speed triple BTW so could probably cope with more abuse than a higher speed set up.

Last time I ran the transmission to replace the whole lot together I almost became unstuck. It was a 7 speed, triple chainring mtb.

Accelerating hard onto a busy roundabout on the big ring I suddenly sprawled onto the top tube in front of approaching traffic. The chain had slipped on the big ring as chain and teeth were so worn. Disaster was averted but the experience taught me not to try to let things wear quite that far again. Normally I try to change chains frequently enough to avoid having to replace other transmission parts.

It is worth noting that the wear rate of chainrings increases exponentially as the chain wears; you can take a half-worn chainring and pretty well destroy it (inside 1000 miles or so if you are a strong rider) by running a worn chain on it.

cheers

3500 miles seems a lot?

Des49 wrote:...Accelerating hard onto a busy roundabout ... The chain had slipped on the big ring as chain and teeth were so worn. Disaster was averted but the experience taught me not to try to let things wear quite that far again. Normally I try to change chains frequently enough to avoid having to replace other transmission parts.

You are not alone .

Des49 wrote:Last time I ran the transmission to replace the whole lot together I almost became unstuck. It was a 7 speed, triple chainring mtb.

Accelerating hard onto a busy roundabout on the big ring I suddenly sprawled onto the top tube in front of approaching traffic. The chain had slipped on the big ring as chain and teeth were so worn. Disaster was averted but the experience taught me not to try to let things wear quite that far again. Normally I try to change chains frequently enough to avoid having to replace other transmission parts.

But 'obviously' one would not allow it to get to this stage,a visual check alone should give some indication as to impending doom.

Psamathe wrote:Chainwheel done 10,000 miles
Cassette done 8800 miles
Chain done 3500 miles

My outer and middle rings have done five times that distance without any visible wear. I'm sure they are worn a little, but not visibly.
My present 10sp cassette is only half that, but 8,000+ miles is about right for the smaller cogs to be worn. The rest of the cassette would be fine.
Chains should go on for 4,000miles easily. I have a 10sp one still ok at 6,000miles.

gaz wrote:You are not alone .

Glad I wasn't alone on this!

yostumpy wrote:But 'obviously' one would not allow it to get to this stage,a visual check alone should give some indication as to impending doom.

Oh it was obvious everything was very worn, but didn't matter on this commuter. I was waiting for the end of the winter to replace the whole transmission. What wasn't so obvious was the exact point at which the chain would ride up over the chainring teeth which needed the extra force that only a maximal acceleration provided. No problems up till then even hard efforts on hills.

There is probably a big difference between worn teeth / pointed teeth / and worn stumps. Somewhere around the middle one would be a good time to swap me thinks.

mercalia wrote:3500 miles seems a lot?

Called in at my LBS at 1500 miles on the chain and asked them to check it, they did and said it was fine (and "we" guess at another 1500 miles). Not checked since.

Original Shimano chain 1274 miles (though I suspect the (different) shop was "pushing" it - gone completely off that shop for various reasons)
SRAM chains 2500 miles and just getting to the point of needing replacement (changed just because I was at the shop and could not be bothered to remember to call-in again an another 500-100 miles). No idea how good/bad current chain is (and I've not been great at cleaning/lubing it over the last year).

Ian

These days I always replace chain and cassette together. (I once tried chain rotation and found that the drawbacks far outweighed the benefits.) I replace them when chain wear is somewhere between 0.7% and 1% (measured with an engineer's rule, not with a chain wear gauge.) I have found that chainrings last about three times as long as the other bits (and you don't save much money by running them longer).

When it's coming up to replacement time for all three I just run them until I get fed up with the noise and/or vibration (due to wear, that is, not due to lack of lubrication!). At that point, which comes sooner for my good bikes than for my hack, and which comes later in winter than in summer, the wear is always more than 1%, sometimes a lot more. I would guess that I am still some way off getting slipping problems.