How to choose new chainset for KTM MTB?

[halfer]

I've been on my new Action Macina 29 for around 10 months, and it's purring along nicely mostly coping well with the daily use it gets. As usual I could do with fixing problems before they occur, rather than leaving them be: the chain, now having done 2K miles, is really tatty and stretched, and the rear cassette is evidently worn.

In the past I've just gone to an LBS and asked for replacements and fitting, but recently I thought that might be a good way to get fleeced: they charge me for mid-range components and fit cheap ones, pocketing the difference. I wouldn't know the difference to look at them, so this time around I'm going to do it myself.

My bike uses a 10-speed Shimano cassette, connected to the Bosch Active Line central crank drive (which would guess uses a standard pinion). I've (approximately) counted the teeth on the cassette, and believe it has 12 on the small one and 40 on the large one. I've seen a couple of mentions of 11-36, so I would guess that would be the right one.

So, I could go for a Dyna-Sys SLX 10 Speed or a Dyna-Sys Deore XT 10 Speed (and on Wiggle at least, that's it for my options, I think). The only 10-speed chain is the HG-X MTB (see links). Would they all work with the small cog on the Bosch unit? I've limited my search to Shimano, as I imagine switching brands would require a new derailleur etc.

What is the difference between a £23 and a £35 cassette? I asked this of a chap at Evans Cycles once, and of course he recommended the expensive one (better materials, etc). Does that mean it will really last longer, in practice? I care about quality and longevity, but not weight so much (for obvious reasons).

I think my factory cassette has worn quickly because I've not monitored chain stretch and let it all go to pot. On a crank drive, should I try to fit 2-3 chains per cassette change? 2K miles (even with non-ideal maintenance) seems rather quick to me. (It was ex-demo though, so maybe it came with a fair bit of wear).

I tend to use Wiggle as they have a good returns policy, but if anyone has recommendations of other sources, would love to hear suggestions.

 

[RobF]

Are you sure the cassette is worn?

Shimano use odd shaped teeth to aid shifting, so a cassette that is OK can look worn to the untrained eye.

Assessing chain wear is another complicated topic.

You say the bike is 'purring along nicely' which suggests there's nothing wrong with the drivetrain.

The cassettes you have chosen would fit, and Shimano kit is decent quality.

I can't see the point of paying £23 for a chain.

You do not have to stick to Shimano, a KMC chain is a bit cheaper and will do the job just as well.

Bewildering range of model numbers, but here's one:

http://www.chainreactioncycles.com/kmc-x10-93-10-speed-chain/rp-prod120676

 

[EddiePJ]

I use the chain that Rob has linked to, and I'm more than happy with it. I also carry a one as a spare as well.

The snap link did break in half after approx 60 miles, but the replacement one that I fitted has been fine.

 

[halfer]

Are you sure the cassette is worn?

Shimano use odd shaped teeth to aid shifting, so a cassette that is OK can look worn to the untrained eye.

Thanks Rob. An LBS showed me the amount of chain stretch using their tool - I forget what it was in millimetres, but it was convincing enough to know it needs doing. Moreover, the chain has come apart three times, and I've twice fixed it with quick links! The LBS pointed out how battered and thin the cassette teeth were in comparison to a new one too, which they held up for comparison.

You say the bike is 'purring along nicely' which suggests there's nothing wrong with the drivetrain.

Sorry - everything except the drivetrain. It was a statement of being happy with the bike generally - which, to be fair, isn't that new any more.

Thanks for the KMC recommendation, I will take a look at that. I take it that will be OK with a Shimano brand cassette? Aha, Chain Reaction do Shimano cassette + KMC chain bundles, so they must be OK. Great!

 

[Deleted member 4366]

Those chain measuring tools always show that your chain is worn. I wouldn't take any notice of that. Run your chain until it starts jumping or making strange grinding noises. 2100 hard winter miles on my cheap chain and plenty of miles in it yet. My cheap freewheel is also holding up pretty well.

 

[kinega]

I've got the same bike, done about 2500 miles. Now on my 3rd chain, have had 2 snap. Last time also changed front sprocket as suffered with chain suck.
To be fair i didn't clean the chain/gears as often as I should have but this bike does seem to have an appetite for chains.

 

[halfer]

Run your chain until it starts jumping

Thanks - yep, I got a bit of that too! I was wondering though whether I should swap a chain prior to significant stretch, in order to preserve the life of the cassette? This might end up cheaper in the long run, especially if one went for a more expensive cassette model.

To be fair i didn't clean the chain/gears as often as I should have but this bike does seem to have an appetite for chains.

Well, it's reassuring that it's happening to someone else! When I've fitted the next cassette/chain I'll see if I can make it last a bit longer. I might swap the dérailleur pinion too.

Where did you get your front sprocket from - Bosch?

 

[JohnCade]

Those chain measuring tools always show that your chain is worn. I wouldn't take any notice of that. Run your chain until it starts jumping or making strange grinding noises. 2100 hard winter miles on my cheap chain and plenty of miles in it yet. My cheap freewheel is also holding up pretty well.

Mine doesn't. It shows it's got about half its life left.

 

[kinega]

Thanks - yep, I got a bit of that too! I was wondering though whether I should swap a chain prior to significant stretch, in order to preserve the life of the cassette? This might end up cheaper in the long run, especially if one went for a more expensive cassette model.



Well, it's reassuring that it's happening to someone else! When I've fitted the next cassette/chain I'll see if I can make it last a bit longer. I might swap the dérailleur pinion too.

Where did you get your front sprocket from - Bosch?

Got a Connex one from eBay, supplier was in Germany.

 

[halfer]

Got a Connex one from eBay, supplier was in Germany.

Ah, thanks kinega. Ordered a cassette/chain bundle from CRC yesterday evening, might get one of those too. I think my current sprocket is OK, but for £13, I think it's worth trying to preserve the chain (and, indirectly, the cassette also).

Hmm, I think I might need assistance though: you need a "Spider Tool and Isis crank puller". Might get someone to fit it for me

 

[Martin@e-bikeshop]

You do not have to stick to Shimano, a KMC chain is a bit cheaper and will do the job just as well.

KMC make chains for Shimano

 

[kinega]

Ah, thanks kinega. Ordered a cassette/chain bundle from CRC yesterday evening, might get one of those too. I think my current sprocket is OK, but for £13, I think it's worth trying to preserve the chain (and, indirectly, the cassette also).

Hmm, I think I might need assistance though: you need a "Spider Tool and Isis crank puller". Might get someone to fit it for me

Got crank puller off eBay, about £5
You can just tap retainer off with hammer &'screwdriver, it's not mega tight. Remember it's a LH thread!

 

[halfer]

Ah, might give it a go then. Come to think of it, I think I have a crank puller (is it the same as the widget to remove a bottom bracket? it looks the same).

Looks like the cog is available in 17 and 18 teeth varieties too.

 

[RobF]

I have one of those £25 Aldi toolkits which has a standard crank puller.

To my surprise, it fits the ISIS cranks on the Bosch motor.

Seems a good chance your crank puller will fit.

As has been said, the lock ring can be tapped around, it's a left hand thread and often plastic, so not tight.

The front ring on a bike would normally last a long time, but it seems to me the 'half size' rings on the Bosch system wear out faster.

 

[Gringo]

I was in the same boat a while ago, a new chain would not run on the original front (motor) sprocket due to chain suck ( after about 1200 miles )
Once I'd gone to the trouble of getting the tools to get the front sprocket off, I found by turning it around and putting it back on, it runs like a new sprocket.
Personally in the future I will run two chains per front sprocket ( reverceing the sprocket for the second chain )
My rear cassette is a different story as I run two prs of wheels & cassettes

 

[kinega]

I was in the same boat a while ago, a new chain would not run on the original front (motor) sprocket due to chain suck ( after about 1200 miles )
Once I'd gone to the trouble of getting the tools to get the front sprocket off, I found by turning it around and putting it back on, it runs like a new sprocket.
Personally in the future I will run two chains per front sprocket ( reverceing the sprocket for the second chain )
My rear cassette is a different story as I run two prs of wheels & cassettes

I turned mine around while waiting for new part & it worked beautifully. To my eye I couldn't see any wear but still changed to new one.

 

[halfer]

I have now taken delivery of a cassette and chain bundle - so far so good. However, I am coming rather unstuck trying to take the old cassette off - can someone advise whether I am doing something daft? I have been following these WikiHow instructions.

See the image (it can be clicked on, if you are logged in, for a larger view). The chain whip I have is not as good as the one from the instructions - there is no spring to prevent the chain from slipping. As you can see I have used a bit of string instead, wound anti-clockwise in the cassette, and then finally around the handle of the whip. This doesn't take any strain.

I have extended the cassette removal tool, on the left, out one notch (the lugs around the logo pop out to allow this extra bit of leverage).

I am applying a great deal of force on the two levers, both downwards as indicated by the red arrows. This has the effect of keeping the cassette stationary and trying to undo the nut anti-clockwise. I usually do this vertically while standing, so the wheel is upright and resting on my shins, with the cassette pointing away, so that I can push down with all my weight. I wear gloves so that the lever grips (particularly the whip) do not hurt my palms excessively.

I have successfully done this before on my previous bike, but in this case either the cassette is too tight, or I am going the wrong way, perhaps? I can pay a shop to release it, but it seems pointless for me to own the tools if I can't use them. Any tips?



You might be able to just see the whip has started to bend (at the point where the whip chain is rivetted to the tool body), which goes some way to demonstrate how much force I am applying to them (keeping it parallel to the wheel helps avoid this though). Both tools are brand "FWE", which I think I got from Evans Cycles.

 

[Deleted member 4366]

Put the chain whip on one of the middle cogs. It will grip better there and you get more leverage without stressing that rivet.

 

[halfer]

Put the chain whip on one of the middle cogs. It will grip better there and you get more leverage without stressing that rivet.

Thanks d8veh. I've tried that, but will give it another go this evening. At least you've confirmed that I haven't spent half an hour tightening it up.

My grasp of theoretical mechanics is minimal to say the least, but I had thought the outer cog would give the greatest leverage, as it allows the tool to be further away from the point of rotation (the cassette centre)?

 

[halfer]

OK, now I've put so much pressure on the chain whip, the chain snapped at the tool body. I've reassembled the link, and it seems to be able to withstand at least non-trivial tension again, but it shows what I am up against.

Frustratingly, the whip tool apparently doesn't want to stay parallel with the wheel - the chain pulls the chain-side of the tool away from the wheel. The greater the pressure it is under, the harder it is to keep it parallel. I've tried to hold it with an adjustable pipe-wrench, but that becomes rather unwieldy.

I wonder if I need a better whip?