Bosch motor sprocket (2014) worn out ?

[Gringo]

As in the title, my Bosch powered Cube has only covered 1400 miles, mostly on dry roads.
I recently checked the chain and it's just worn enough to need replacing without changing the cassette.
I went for a straight like for like swap (KMC 9 spd) but even after degreasing & re-oiling with light oil, the new chain ( under light load ) dose not release from the front sprocket, it gets pulled back around and trapped under the oncoming chain.
Fortunately I found this out without motor power otherwise I could have done damage. Off the ground everything turns OK !
I don't have the tools to remove the crank arm & motor sprocket but looking the best I can, I'd say there's a distinct worn (hooked) look to the sprocket.

I've several questions
1/ is it normal for Bosch drive sprockets to need replacing this early
2/ should I take this up with Bosch, Cube or the retailer
3/ what tools would I need to remove the crank & sprocket
4/ where would I find a replacement sprocket

I will contact the shop where I brought the bike but I have little faith in there customer service, probably the worst I've personally experienced & it's no one using this forum

I still love the bike but if the Bosch motor sprocket needs changing this often then there's something wrong with the design

 

[Croxden]

Over 4,200 miles with mine and OK so far. I bet the chain is stretched if I checked but it's fine with drive sprocket and so it's stopping as it is.

 

[Martin@e-bikeshop]

I recently checked the chain and it's just worn enough to need replacing without changing the cassette.

Hi Gringo,

This is the first mistake, a drivetrain should always be replaced together. All the components wear together over time.

Expected life of the drivetrain 1500-2500+ depending on conditions.

I bet it didn't slip before? If it ain't broke.. Don't change it.

Now the new chain will for sure hook over the old worn sprocket.

Particularly the new Bosch smaller sprockets as the tolerance is tight as it only grabs on about 10 teeth where as a traditional sprocket touches approx 25 teeth.

Assuming your eBike supplier is not forthcoming enough to carry spares to support their customers, you can find all the bosch spares here.

You will also require crank puller and Performance Spider tool, again both available on my website.

Please buy a replacement cassette at the same time and do it all in one go.

Regards
Martin

 

[Gringo]

Over 4,200 miles with mine and OK so far. I bet the chain is stretched if I checked but it's fine with drive sprocket and so it's stopping as it is.

Sounds good, I'd probably be doing the same but I'm running two sets of wheels & two cassettes ( different ratios )
Now I've put the second wheels on (off road tyres) the cassette has only 300 miles on it, the part worn chain won't do the new cassette any favours.

I'm just trying to get the best out of things and using mr sheldon browns advice on chain replacement

 

[Gringo]

Cheers Martin
It's a bit of a poor show if you can only expect as little as1500 miles on a drive train.

I'll just add the bits up for 1400 miles
Spider tool.......... £30
Crank puller.........£17
Drive sprocket ....£14
KMC 9spd chain. £8
Cassette.............£15

 

[trex]

your mistake is to replace the chain too soon. Don't replace is it's stretched a bit. Next time, wait until it starts getting noisy or skip. You'll find it'll have done 4,000 miles.

 

[Gringo]

Trex your right.
As we speak, I'm now running my old chain & motor sprocket with my newer low mileage rear cassette. Even though it goes against my engineering background to run new parts with worn, I'll just have to get over it.

 

[Nealh]

m20 std crank puller £1.98 on fleabay.

 

[RobF]

I went for a straight like for like swap (KMC 9 spd) but even after degreasing & re-oiling with light oil, the new chain ( under light load ) dose not release from the front sprocket, it

Eeek, degreasing the new chain is just what you don't want to do.

New chains are waxed from the factory and should be left well alone.

I think your maintenance regime is shortening the chain's life, not lengthening it.

Forget the 'engineering background' and leave well alone, apart from a regular wipe and an occasional lube.

 

[Gringo]

Rob degreasing was a last resort, I'd tried using the new chain as purchased to no avail before resorting to degreasing, i said in my OP "even after degreasing" not degreasing before I'd even tried fitting it, I'm not a complete muppet

m20 std crank puller £1.98 on fleabay

.

Yeh but, it's not a standard crank.
But now you've said that, I've looked deeper,I believe it's a ISIS crank & you can get a puller for those at around £7 As a posed to the Bosch price of £17.
Once I have the crank off I'll need a spider tool, £30 is a bit pricy maybe I'll have to get on my milling machine & make one

 

[Gringo]

Manufacturers advise replacing chains worn between 0.5% to 0.75%, this helps minimise poor shifting and accelerated sprocket wear

.

This view seams to be held by most of the cycle industry,
If people are happy running there drivetrain until it starts jumping or shifting badly, by all means go for it. I'm just trying to follow industry advice.
I believe with a conventional drivetrain & front sprocket the above advice is worth following.
I'm surprised some folks think its wrong to expect more from my Bosch sprocket.

 

[Gubbins]

It looks like I go against all advice.. Once a month I put my chain in an ultrasonic cleaner which really does strip everything out! I use the park chain measuring tool to decide when to change it and so far I am on second chain at 2800 miles on original ring and cassette with no visible signs of wear, skipping or other problems. But mine is the bosch classic with the bigger chain ring......

 

[JohnCade]

I've always changed chains when they showed wear on my road bikes, and if caught in time the rest of the drivetrain will outlast several chains. Everyone else I knew did the same. Just letting the whole thing wear out together doesn't appeal to me. Chains are a lot cheaper than the rest of the drivetrain.

This problem seems to be a feature of this motor with its small chainring. Not impressed by a lot I've read about the Bosch motors.

 

[RobF]

Once I have the crank off I'll need a spider tool, £30 is a bit pricy maybe I'll have to get on my milling machine & make one

You will also need to fire up your foundry to make some ingots of the correct alloy.

Hardly worth it when you can tap the nut off with a screwdriver in about 20 seconds.

Left hand thread on the Bosch Classic, dunno about the newer one.

You mention earlier a KMC chain for £9.

Nowt wrong with KMC - although I prefer KFC - but £9 looks too cheap to me.

For example, the Rose comes with a Shimano Dura Ace which is about £30.

Here's a £30 KMC designed for crank drive ebikes.

Slap this on - and leave it alone - and the job's a good 'un.

http://www.chainreactioncycles.com/kmc-x10e-ept-ebike-10-speed-chain/rp-prod120625?utm_source=Google&utm_medium=Shopping&utm_name=UnitedKingdom&gs=1&gclid=CPTsrOrM3sECFdLKtAodhBsADQ&gclsrc=aw.ds

 

[Gringo]

Rob the KMC chain, that's discounted to half RRP
My Cube came with a KMC chain & there's no visual difference between the old chain & my replacement.

Anywho, it's not the chain that's f^[{# d it's the motor sprocket
Your totally missing the point of my OP

 

[Martin@e-bikeshop]

Rob the KMC chain, that's discounted to half RRP

Its also a 10 speed chain, yours is probably 9 speed on the KTM.

 

[Martin@e-bikeshop]

Nowt wrong with KMC - although I prefer KFC - but £9 looks too cheap to me.

For example, the Rose comes with a Shimano Dura Ace which is about £30

KMC make Shimano's chains... Just saying

 

[Martin@e-bikeshop]

.I'm surprised some folks think its wrong to expect more from my Bosch sprocket.

Fact is it WILL last much longer if you resist from changing the chain early.
No surprise there.

 

[Gringo]

Martin I agree, if you let everything go on until it's all knackered you'll get more miles.
This is possibly what's expected in the pedelec world but I come from the world of

Manufacturers advise replacing chains worn between 0.5% to 0.75%, this helps minimise poor shifting and accelerated sprocket wear

So this way of thinking is a culture shock.
As I'm running two cassettes with different ratios, keeping on top of the chain makes sense, at least it did when my bikes had full sized front rings, now I'm not so sure.
As to expensive chains, will they bring my worn sprocket back to life or make a new sprocket last longer.

 

[Croxden]

With the Rohloff the rear sprocket can be removed, turned over then start again. Not being a derailleur makes for less wear, they just keep everything going.