I bought my EX8 back in April 2010, I’ve never managed to get the transmission up to scratch. Its a full XT drivetrain with SLX shifters and all in v good condition (all stock kit).

Basically, I’m quite a big lad (6’4″ and 18 Stone)and whenever I try to put some power through the drive train it just slips. I think I have a pretty good pedalling technique, mostly circular pedalling but sometimes you just need to crank a bit more power through, say on a climb or over an obstical but whenever I do this the drivetrain just slips.

I’ve had it re-tuned, new cable outers (now running a full length outer for winter rides) and a new chain. No change! still slipping when you crank the power on!

Not a natural engineer or mechanic but is it possible that the freehub is faulty? if notwhat would be the most likely problem?

Thanks in advance…

is there a loud ‘crack’ when it slips?

It it’s a Shimano freehub then chances are it’s that.

well its pretty loud when it does go but I just put that down to it being the gears slipping. but in general, its a big crunch sound.

Is that a known issue with shimano free hubs and should that be replaced under warranty seeing as its only 10 months old?

it’s what they do when they’re worn.

I’m not sure if an 18 stone bloke using them it for 10 months will count as wear and tear or be a warranty issue, tbh.

Talk to the shop you bought it from? Replacemtns are about £30ish depending on type of hub it is.

Changing it isn’t difficult to do yourself but you’ll need to have a fridge handy for the ball bearings to roll under.

Sounds a v odd one…new chain on used cassette won’t be helping, I too would have suspected cable problems.

Once saw a 7s cassette where the chain slipped on the bottom cog, tried another cassette and all good, could be a duff cassette.

No use guessing on here tho, go to a decent shop.

Just checked the spec online and its a SRAM PG950 9 speed cassette. not sure what difference that makes.

Unfortunately I haven’t been able to get that many miles on the bike so it must be made out of cheese if its a wear and tear issue, as I said, its been doing it since its first outing. I alsways clean an re-lube the cassette and mechs etc after each ride.

I’ll take it back again and make sure they look at it properly. Last time they just re-tuned it but you don’t know if its been cured until you get on the trail and put you foot down.

Thanks guys

That does not sound like a problem that can be solved by tuning or changing shifter cables. Something is worn – either the cassette, chain, chainrings which will be a meshing-under-load problem; or the freehub is slipping under load. From what you describe, my money is on the latter.

Check the simplest things first.

Tight chain link? Often overlooked.

Take off the cassette and make sure it still pinned/riveted together (seen a number of SRAM ones now that fall apart)

Worn cassette, try a new one.

Ghost shifting? Could be a badly routed cable.

Then freehub.

Just been familiarising myself with hubs, freehubs and cassettes so i know how it all fits together.

I had the cable replaced and a re-tune whilst at Afan back in November, still no change. cleaned an re-greased the chain, checked for stiff links etc – all smooth… no change, brand new KMC chain, no stiff links, fully greased and smooth… no change. I honestly don’t think i’ve done enough miles yet to wear dthe cassette out that said what sigbns of wear should i look for on it?

Unfortunately I don’t have the kit to remove the cassette etc so will leave this to the shop.

I’ve been checking the spec and its an m525 hub, does anyone know if these are any good and would it be worth swapping?

m525 are ok – certainly not worth replacing the hub and getting the wheel rebuilt for a freehub problem – freehubs seem to be about £23 each.

thats the kind of think i like to hear.

does sound like the freehub….

my XT756 one gave up and gave the same sounding issue that you have..

Powerful rider, 10 months before changing the chain, slipping under load.

I bet it’s worse in certain gears – the ones you typically use. I have changed my mind: It’s the cassette. If you’re lucky, the chainrings are OK still.

Have a careful look at the shape of the valleys between the teeth on both rings and cassette. They should should be near perfect ‘U’s. The wear is caused by not changing your chain earlier. I’ve done it myself 🙁

Will check tonight but they all looked pretty uniform when I cleaned it last weekend. I did replace the original chain after 6 weeks and it was still slipping.

Anywhoo i’ve booked it in to get the cassette and freehub checked over but can’t drop it off for a week or so. WIll let you all know what the problem is/was.