Cassette worn out after only one chain?

[Smurfy]

Chainrings are unpredictable. The set I'm using now is on its 5th chain and 3rd cassette having done about 6000 miles. The middle ring shows it's been well used but is nowhere near the recycling bin yet. In the past I've had the most heavily used ones need replacing at 2000 miles, other times they've done over 10000. I have no explanation for this as I treat them roughly the same.

The cassettes fitted as original on my last couple of bikes have lasted one chain and about 1000 miles. The replacement ones last 2 chains and over 2500 miles. I can't think of any plausible explanation!

Stainless steel and Zicral alloy (trade name for 7075 grade aluminium) chain rings are reported to last longer than cheaper, softer alloys.

Have you tried inspecting the inside face of the outer ring? A softer alloy will show a lot more gouging and scraping than a harder, more wear resistant alloy.

 

[Randy Butternubs]

Cheers for the responses.

I finally got around to fishing the old chain out of the bin and giving it a proper measuring. From pin centre to pin centre across 10 full links should be 254mm. I measured no more than 0.5mm stretch across several areas of the chain which equates to 0.2% wear. Measuring chains is fairly awkward but I was using a good ruler and use one to measure down to fractions of a mm frequently.

Either my measuring is way off or I've managed to wear out the cassette long before a single chain. Are SRAM cassettes, specifically the PG730, known for being made of cheese?

 

[fossyant]

3 favourite sprockets gives you the answer.

 

[fossyant]

I wear out a fixed gear sprocket and chain in a year. Consumables. Don't worry.

 

[I like Skol]

3 favourite sprockets gives you the answer.

THIS^^^

I just changed the chain on my commuter a few weeks ago and this was the first chain on the current cassette but even after 150-200 miles it was still skipping on certain gears under certain conditions. I finally gave in and fitted the spare cassette I had in stock
This is unusual because I normally get 2 chains to a cassette without any issues but I suppose this illustrates the variability of the beast (a trip along the N. Wales coast in awful weather earlier in the year could be the reason?). It was A KMC 9spd chain and had done around 1.5k as normal and I use Sram PG950 cassettes which seem to strike a reasonable balance between price and longevity.

 

[fossyant]

It's why I commute fixed. I found I only really used 3 gears.

 

[Randy Butternubs]

My replacement cassette arrived and I'm no longer so sure the cassette is worn. What I took to be worn teeth are present on the new cassette so I guess its just a weird shape to help shifting.

Is there anything else it's likely to be?

 

[Pale Rider]

My replacement cassette arrived and I'm no longer so sure the cassette is worn. What I took to be worn teeth are present on the new cassette so I guess its just a weird shape to help shifting.

Is there anything else it's likely to be?

Judging cassette wear is difficult because, as you say, most have odd shaped teeth to assist shifting.

I believe Shimano call it Hyper Glide which is why you will see some their cassettes with 'HG' in the model designation.

 

[Yellow Saddle]

My friend runs two chains, swaps them over every week. Says it saves his cassette from a lot of wear and tear

Your friend probably also thinks homeopathy is science and babies are delivered by the stork.

 

[Yellow Saddle]

3 favourite sprockets gives you the answer.

OP, here is your answer. Had you used all your sprockets equally, it would have lasted longer.

 

[Yellow Saddle]

My replacement cassette arrived and I'm no longer so sure the cassette is worn. What I took to be worn teeth are present on the new cassette so I guess its just a weird shape to help shifting.

Is there anything else it's likely to be?

The only way to confirm that the cassette is worn is to fit the new chain on the new cassette and go for a ride. If it is all good, then refit the old cassette and do the same. Discrepancies in your favourite sprockets will soon show up, especially if you push hard in them on a slight gradient. Then a worn sprocket will skate.