Chain wear - effect on drivetrain

Something of a newbie question here - please be gentle! For the last nine months or so I've been riding to work (about 9 miles per day) most weekdays. I'd just got to the stage where I've realised the benefits of actual maintenance beyond the odd clean and re-lube every so often, and ordered a new chain (and chain breaker / wear indicator) yesterday.

Today when riding in I had a couple of big chain slips - enough to throw me off balance. It came as something of a surprise, so I didn't notice whether the chain slipped at the front or the rear. Obviously I'm going to go to my other bike until I can replace the chain, but I was concerned about the possibility of damage to the sprokets (which were new nine months ago) or chainwheels.

As far as the sprockets go, I'm inclined to follow the "0.75% 'stretch' means a new chain, 1% means a new cassette" rule of thumb. For the chainwheels, is there much cause for concern? Presumably the wear per tooth on the chainwheels would be less than on the sprockets because of the greater number of teeth. Am I likely to have incurred acute damage during the 'slips' though?


I'd just change the chain, the sprockets should be OK after 9 months.

Done over the weekend. Feels better, especially when starting at lights (100 kg of Tony can put a fair amount of force into the drivetrain.) The wear indicator showed 0.75%, which was rather less than I had feared.

something to be very aware of is the affect that over enthuastic chain cleaning has on accelerated drivetrain wear

a good tip (contrary to much "common knowledge") that also comes from chain makers KMC and Shimano is to *never clean your chain using any degreasers or solvents*

chains should be wiped clean or brushed clean and then chain lubricant applied, and chain wiped to remove excessive lubricant

in extreme examples (mountain biking?) a mild solution of soapy water should be applied.


KMC manufacture in excess of 2 MILLION chains per day, and I would take their experience with a measure of confidence


the reasoning is that once the internal lubricant (applied during factory manufacturing of the chain) is flushed using degreasers or solvents, it can never be fully replaced and this leads to accelerated wear to both the chain, and then the drivetrain

an interesting experiment to expand on this reasoning is to take a brand new chain, and put it through a parts washer (or use a degreaser / chain cleaning machine) and be surprised at how "sloppy" the chain then becomes, especially laterally....


personally? as a professional bike workshop manager I don't put my chain anywhere near solvents or degreasers, it is wiped clean and lubed, and wiped again, and this works just fine (same is true of rear derailleur cage and pulley wheels) - I do put my cassette and chainring through the parts washer as these have no moving parts..

I've cleaned my chain using the detergent in a bottle method (ie, very enthusiastically), and immediately afterwards experienced bad chain slip.

I've never done it again!

  • By Stily1 at 5:15am 14 June 2012

I can say that in motorcycling circles, you always replace the sprockets when you replace the chain, and vice versa. Putting a new chain on worn sprockets, or a new sprocket under a worn chain, will accellerate the wear/death of the new part. I don't know how that applies to all the smaller sprockets and parts on a push bike, which seems would be very expensive to replace all at once.

I've been cycling my Brompton about 14 miles a day 5 days a week for about the same amount of time (9-10 months) and I've just started having bad chain slip and turns out my front sprocket is toast.....teeth worn to points. Surprising, but I've used the thing up, I guess. The rear sprockets etc. look okay, so I think I'll replace the front sprocket and chain (depending on what my shop suggests, once I can get their attention). 

On a side not, dissapointed to find that you have to replace the crank with the front sprocket on the Brompton. Seems a waste. 

@hampsteadbandit - I'm intrigued by your claims. Can you point us to some evidence that supports them? For instance, Shimano state here that you should use an "appropriate chaincleaner" - . Are you saying that commercial degreasers are not appropriate, or that Shimano have said something different to you? Similarly, Sheldon Browne's carefully considered article is here: . @countertony - I was surprised how quickly the chain and sprockets wear when you start seriously using a bike. I covered similar mileage to you, when it was 11 months old, took my brand new bike in for a service to the place I had bought it, and was told it would be cheaper to scrap it because it was so "old" and worn! It hadn't occurred to me that one year of heavy, daily use (4000 miles) was enough to need a new chain and sprockets. Anyway, I know now, and I learnt to check the chain wear regularly, and how to replace the chain and sprockets (no, I didn't scrap the bike). No-one had ever mentioned that these parts are consumables, but I guess most of their new bikes don't see serious use.

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