MTB Cassette Recommendation

[Trevelyan]

I'm in the market for a new cassette for my mountain bike. I'm still using the one the bike came with but the smallest two gears are now badly worn causing the chain to slip. There are no markings on the current cassette but the paperwork which came with the bike seems to indicate it's a SRAM 9 speed - probably a PG950. The thing is that I reckon the bike has only done about 900 miles - I'd have thought a cassette should last longer than this?

Anyway I'm in the market for a new cassette and don't mind spending a bit more to upgrade if it improves performance or lasts a bit longer. A new PG950 would cost me about £20, but I'm happy to spend up to about £40 tops if it gives me value for money.

The only obvious SRAM upgrade would seem to be a PG980 but I don't mind going to Shimano if necessary. The only obvious Shimano option would appear to be an XT M770 for about £44. So has anyone got any recommendations?

[robpearson]

I'm a big fan of the SRAM cassette, have them on road and MTB. I have to say that does sound as if it's worn far too fast. I have just replaced the chain on my road bike at 2000 miles and the casette looks immaculate, not sure about the distance on my MTB, but have done chain and cassette aswell as its been 3years and many trips through mud and sand - need a new middle ring very soon too but couldnt find what I wanted in stock at the weekend. Honestly though, I don't know if I could tell the difference in the different models of cassette in terms of smoothness of shifts, I suspect a better cleaning regime would make a greater difference

[Trevelyan]

I must admit I did like the way the SRAM cassette shifted when newer - it was very slick for a cheap cassette. I'm just concerned at the speed it's worn. I do ride mainly on sand/grit (the Greensand ridge area around Woburn and Ampthill for those who know) which could explain some of the accelerated wear.

I'm tempted to go for the upgraded SRAM offering and see how I get on. One other question - I'm assuming that if I replace the cassette it makes sense to put a new chain on? (currently I'm using a KMC X9 and would probably choose the same again). On the other hand I guess the front chainset is ok to reuse if it's showing no signs of excessive wear?

[P-Jay]

I've always found Shimano to be the best cassetts, XT are great and I've used them for years, but the SLX version (might be called a HG50 sometimes from memory) runs just as well, weighs a couple of grams more, but is much cheaper.

[frontbum]

Trevelyan said:

One other question - I'm assuming that if I replace the cassette it makes sense to put a new chain on? (currently I'm using a KMC X9 and would probably choose the same again). On the other hand I guess the front chainset is ok to reuse if it's showing no signs of excessive wear?

Yes, exactly - otherwise it skips and I think can wear out the cassette quickly.

I usually do chain & cassette at the same time, then two chains over the life time of the cassette and replace the chainrings every 2-3 cassettes.

BTW if you have a Hope hub, make sure your new cassette has a solid carrier, or it'll eat the freehub body.

[Parrot of Doom]

Don't bother with anything alloy, just get a steel cassette, it'll last a lot longer and you won't notice the difference in weight.

Oh and you'll need a new chain as well.

[walm]

It certainly sounds as if your cassette is worn but I would change the chain first and check that it still skips.
It might just be a chain problem.
900 miles seems a little quick to wear is down, for sure.

[BOR]

I replaced a PG 990 with another PG 990 last night. It lasted several thousand kilometres, so 900 miles seems unusual. Clearly it's going to depend on your style, how abrasive your local conditions are, how you clean/lube your chain etc.

I've ordered another PG 990.

[custardkid]

you sure its not a setup/shift issue?

generally more expensive cassettes just mean lighter... not longer lasting (perhap inverse)

i've replaced middle rings & chains but never a cassette on a mountain bike.. must be lucky

Custard

[Trevelyan]

I'm pretty sure. When you look at the cassette the two smallest gears are definitely worn. I guess it's just a combination of the environment and my inexperience. I'm fairly sure that I'm much better at using gears now than I was when I bought the bike. I also did a fair bit of road riding in the winter months which made heavy use of these gears.

I went for a SRAM PG980 in the end, but ordered a SRAM PC991 chain to match rather than sticking with the KMC offering. Strangely enough it appears as though a pair of Panaracer Fire XC tyres and a few workshop tools seem to have fallen into my online shopping basket at the same time. I'm not sure how that happened...

[robpearson]

Don't you just hate it when you accidentally click on basket instead of wish list...

[cjs]

frontbum said:

BTW if you have a Hope hub, make sure your new cassette has a solid carrier, or it'll eat the freehub body.

I did notice this when I swapped the cassette on my Hope Hub, so it is a common problem? Hub is only a year old and has big 'nicks' in the key groves made by the cassette. Old cassette was a Sram, new is an XT, hope my Hope does not sustain more damage.

[custardkid]

cjs said:

I did notice this when I swapped the cassette on my Hope Hub, so it is a common problem? Hub is only a year old and has big 'nicks' in the key groves made by the cassette. Old cassette was a Sram, new is an XT, hope my Hope does not sustain more damage.

ti or ally freehub bodies are softer than steel this will always happen unless you spread the load off individual rings onto a carrier.

cheap cassettes are steel rings pinned together with plastc spacers, meaning all your peddle torque is transfered through a c3mm surface area onto the free hub body to turn the wheel
more expensive cassettes have an aluminium carrier in the centre with rings attached to that (its lighter) the carrier has a larger surface area.

like this:



custard

[hughjayteens]

Sram PG-990s on both of my bikes. Have had XTR in the past but the 990s are cracking value, lightweight and seem to last forever.

Have just acquired a 980 on a spare set of wheels but no idea how much use it's had.

[Beyond Rational]

Trevelyan said:

I'm pretty sure. When you look at the cassette the two smallest gears are definitely worn.

On some cassettes, the two inner rings are sometimes more 'shark fin' in pitch than the other rings from new. I'm just wondering if, as others have said, the chain is worn and is slipping in these gears due to a lack of tension?

[Trevelyan]

It's funny you should say that. My order from CRC got delayed and so won't be with me until next week now. As I wanted to get a few miles in this weekend I ended up stripping down the drivetrain and giving it a good clean up on Friday evening. It now seems to be working fine again! I'm slightly puzzled by the whole thing. The last full strip down and clean was only a few weeks ago (the Royal Wedding BH weekend) and the chain was well lubricated then and had shown no sign of problems since.

Anyhoo, all is now good so I guess I'll just keep running with the current cassette and chain and keep the new ones as spares I guess. I wondered whether the problem was caused by a build up of sandy greasy crud around the dérailleur and gears due to mainly riding on sand and gravel so I'm experimenting with dry lube for a while to see if that helps. Otherwise I'm unsure what the cause was!