Weird SRAM RED gear "slipping" issue

[mikees]

Googled this and get loads of hits but none seem to match what I am seeing or feeling.

In any gear every 3-4 (this is random but seems to be between 3 and 4) rotation the crank there feels thru the pedals a sort of slip or drop if resistance to pedalling.

This is only for a second or less then is fine.

Its not slipping between gears and all shifting is OK.

Any ideas?

Full Red GS on a Planet X bike, prob done under 500 miles (bought of mate who decided he didn't like cycling after all)

Cheers
Mike

Edit: is the cassette is kaput, presume I can walk this on rather than a Red one?

http://www.wiggle.co.uk/sram-pg1070-10-speed-casse...

Edited by mikees on Wednesday 30th March 11:04

[battered]

Dicky freewheel mech, possibly. I had it once years ago, it started like you say, I ignored it, after a bit it started letting go at random intervals. I replaced it, prob still have the knackered part in the bits box awaiting stripdown, cleaning and reuse. Yes, it's never going to happen, but you know.

I don't think stripdown is actually an option unless you have special tools or are prepared to make things, and it's a £10 part.

[okgo]

As said, unless it jumps, or slips drastically, which will mean a worn chain or cassette or both, you would know about this as it would result in you probably smashing your knee on the bars - its got to be hub freewheel, more than likely a pawl is to blame as they are the things that glide one way which makes the clicking noise when you freewheel and they lock the other against to allow you to engage when you pedal. If one of these is broken or slipping then it would explain what you are feeling.



You can probably see what I mean from this, one way they click over the ridges, the other they are meant to lock against, if you're not getting the locking against then they're probably worn or something more sinister but similar.

Edited by okgo on Wednesday 30th March 11:22

[mikees]

Nothing is ever easy is it.

Okgo, simple DIY fix or LBS?

I was hoping to have an excuse for a new higher geared cassette.

Cheers
Mike

[Zoon]

battered said:

Dicky freewheel mech, possibly.

I'd go for this, had exactly the same on my old bike.
Symptoms very similar to what you describe.

[okgo]

mikees said:

Nothing is ever easy is it.

Okgo, simple DIY fix or LBS?

I was hoping to have an excuse for a new higher geared cassette.

Cheers
Mike

What wheels do you have?

Generally you need to buy a new freehub body, which is fairly easy to fit/remove old one depending on the hub. They cost anywhere from £30 to £lots depending on the hub. Personally I would do it myself on some wheels and others just leave it to a lbs as they can be a pain and the last thing you want is the springs from the new one that hold the pawls in place pinging off somewhere, or bearings falling out etc.

That said, there are generally lots of how to videos on youtube to walk you through it, its far from the hardest job, just potentially a bit annoying if something goes wrong.

[mikees]

Fulcrum 7 wheels. I like to try and do most stuff, but if its a pig to do - LBS it is.

[okgo]

mikees said:

Fulcrum 7 wheels. I like to try and do most stuff, but if its a pig to do - LBS it is.

Ah ok.

I have just had a quick look, £70, once you factor in the LBS, you may as well buy a new set of the same wheels for £100 here http://www.googleadservices.com/pagead/aclk?sa=L&a...

[battered]

I DIYed but it was an old Shimano 7 or 8 speed hub. Easy enough. Pull the cassette, usual chain whip and spline tool needed, then IIRC it's a 10mm Allen to unscrew the FWH retainer, pull it off, replace it, put it all back together. Half an hour if you know what you are doing.

Actually, memory flooding back. You can't actually buy the FWH mech, you have to buy a hub. Or did at the time. You therefore have considerable fun holding the hub (which is round and polished and has no spokes or rim to grip) while you unscrew the FWH retainer. ISTR I ended up wrapping it in a rag and gripping it with water pump pliers or similar. Joy.

[jamiebae]

I bet if it's a Planet X bike the Cassette isn't a SRAM Red one anyway (they like to cut corners where people don't notice to get the visible nice bits on at a lower price point) so I'd make the swap anyway of you need a bigger gear on the back.

If it is the freehub I'd just bin the wheels and grab a new set, think of it as a £75 discount on an upgrade rather than getting an LBS to mess around trying to sort it as you'll have to pay them even if they find it's broken beyond repair.

[Dixie]

Don't you also need to remove the spindle from the hub? It's been a while since I've done this but the replacement free hub was a sealed unit. There was no chance of any mistakes when fitting it.

OP. It might be worth laying the wheel on the ground (cassette side down) and giving the back of the free hub a good dowsing in GT85 of similar. It might be that the ratchets are a little over greased/jet washed to death or something. Worth a try before spending a load.

This'll fit:

http://www.chainreactioncycles.com/shimano-deore-m...

[battered]

Dixie said:

Don't you also need to remove the spindle from the hub? .

Possibly, I can't remember if the cassette will clear the cones or not. Even if it won't it's not a biggie.

[bakerstreet]

Is it a SRAM Red cassette? If it is and isn't too badly worn, then I'd consider selling that as they are very expensive. You might even get £50 for it

[mikees]

bakerstreet said:

Is it a SRAM Red cassette? If it is and isn't too badly worn, then I'd consider selling that as they are very expensive. You might even get £50 for it

Nope its a PG 1070 so only £40.

So - more fault finding !

Ive swapped a 10 speed Fulcrum 5 wheel with a Ultregra Cassette and there still seems to be the same feeling which would suggest we might be back to some strange mech issue - off to place some more.

Mike

[Catchme]

Do you think it might be chain-related. You may see the chain completing a full revolution every 3-4 turns of the crank, depending on gearing and frame size. Stiff link maybe?

[mikees]

Catchme said:

Do you think it might be chain-related. You may see the chain completing a full revolution every 3-4 turns of the crank, depending on gearing and frame size. Stiff link maybe?

That sounds like a sensible suggestion !

Just re-indexed to make sure all was well changing wise. Noticed the FSA Crank cap had spun out while on the TT that that refitted (cant see it being related).

More playing later. I'll keep this updated with the outcome

Cheers Guys
Mike

[gazza285]

Catchme said:

Do you think it might be chain-related. You may see the chain completing a full revolution every 3-4 turns of the crank, depending on gearing and frame size. Stiff link maybe?

First thing I thought of was a stiff chain link.

[ALawson]

Is the chain joined via a pin or quick link? I had something similar until the chain split where the pin had been installed incorrectly.

[Matt_N]

battered said:

Dixie said:

Don't you also need to remove the spindle from the hub? .

Possibly, I can't remember if the cassette will clear the cones or not. Even if it won't it's not a biggie.

Fulcrum 7 use sealed cartridge bearings so no cones to clear.

You'd remove the cassette, then the axle, then the freehub.

This link shows you how to dismantle a FR7 rear hub and describes similar symptom for doing so:

http://acatalepsia.org/?p=98

[TheInternet]

If it's the same as my Racing 5s, the 7s have three pawls and one spring for the freehub. Quite a simple replacement job as seen in the above link.