Gate Drive Belt

[Brucey]

double brake failure sounds about right. I've been up and down the stelvio a few times and if there is one part of the world you don't want brake problems that is it. I wonder what happened exactly?

cheers

[Jupestar]

I couldn’t tell exactly you but it was a big tumble, the cold must have chilled her hands or her brakes. I was probably 100m downhill and climbing, doesn’t sound like far, but it took me a while and plenty of people were in attendance when I finally arrived, and she was on her feet, so I just kept going.

I’m no doubt Quintana, in the same position. later in the day would have been first on the scene.

[zenitb]

It it helps here is how my first Gates transmission ended up.. Note the missing teeth on the sprocket wheel.. and the conditions I cycle in...

For full disclosure I buy all my own kit

[Brucey]

any idea of what may have contributed most to the failure?

cheers

[zenitb]

any idea of what may have contributed most to the failure?

cheers

there was some talk on the internet about a batch of faulty sprockets..however I have no idea whether that was the cause of this failure - although the symptoms seem to match. Back then I did commute in all weathers/all seasons through some deep mud, puddles and gravel so I wondered at the time whether a stone had got flicked up and had jammed between the belt and sprocket?

I got the belt and sprocket shown in the pic replaced under warrenty so don't have them any more for further analysis. However I do still have the SECOND belt that failed. I will dig that out and put up some photos so we can look for a pattern.

[Billy007]

Deleted.

[Jupestar]

If you could say what sprockets and belt you had whether CDN, CDX or CDX:EXP this would be very helpful.

In the OP case, Gate CDN 120t, to a 46t/22t driving a Nexus 8.

[Cyclewala]

Many car manufacturers moved from chain driven engines to belts and back to chains. Whilst belts have their benefits, chains are less likely to lead to catastrophic engine failure.

Granted bikes are not the same as cars, but could the same be principle be applicable to bicycles?

[Billy007]

If you could say what sprockets and belt you had whether CDN, CDX or CDX:EXP this would be very helpful.

In the OP case, Gate CDN 120t, to a 46t/22t driving a Nexus 8.

Thank you this helpful.

From my understanding of the Gates spec of belts and sprockets, CDN is your basic level i.e. commuting leisure riding typically in cities and urban areas, not extreme cycling. The rear sprocket and front sprocket are manufactured from plastic and the belts are robust but not of the higher spec belts which I believe have Kevlar in them, but I might be wrong.

For the higher spec CDX/ CDX:EXP range Gates make the rear sprockets in stainless steel rather than plastic and the front belt rings in 7075 aluminium and their belts as I mentioned above are tougher, containing Kevlar I believe but I might be wrong about the Kevlar. In any event they are much tougher than the CDN belts. So because the CDX / EXP components are more durable they can be used for off road, snow, ice, sand, extreme expedition riding, winter riding in cold temperatures.

I suppose you could use a CDN set up all year in all conditions but it might not last as long as a CDX:EXP sprocket and belt set up.

My belt drive bike came with a plastic rear sprocket which I changed for a stainless steel one. I still have the plastic front cog, but am trying to find a CDX:EXP one in the same size. I did get a CDX belt but at present I am still using the CDN belt until it wears out.

I think if I was going to be frequently riding through mud, gravel, sand, salt of winter I would put the CDX components and belt on. I shall be putting the CDX belt on when I go on tour and will hopefully have found an aluminium 7075 front ring by then, but I think the front ring despite being plastic will fair better as there is less wear on it simply as it is larger.

If my bike's belt and sprockets got covered in mud like in the pics I would be hosing it off. A fully enclosed guard would be nice, but I don't currently see one on the market. Not to say a partial one couldn't still be fitted to help keep the belt clean.

HTH.

[Jupestar]

Thanks, Sounds like CDN is probabaly the right level for the use, leisure and commuting, the most extreme it gets is the canal path, but i think that has been abandoned for the winter.

The front is Plastic CDN 46t.
Rear is 22t CDX, coated steel i believe.

Both gates.

[Billy007]

Deleted.

[Cyclewala]

Many car manufacturers moved from chain driven engines to belts and back to chains. Whilst belts have their benefits, chains are less likely to lead to catastrophic engine failure.

Granted bikes are not the same as cars, but could the same be principle be applicable to bicycles?

So you are saying, just because YOU do not like the concept of belts being used on bicycles then all development by companies such as Gates should cease or is fruitless as ultimately chains are better?

FYI you can get just as serious engine failure with a chain in car or similar engines if the chain tensioner fails, just as you can if a belt tensioner fails or the belt lets go. It is not really relevant to a bicycle transmission application as the use, forces and loading on belts is totally different.

I didn't express any preference or dislike of belts. I was merely pointing out that many car manufacturers have reverted back to chain cam engines after experiencing issues with belts.

I personally, like the idea of belts on bikes. But, the specific frame requirements and special parts would be off-putting.

If I was commuting again (a) and didn't have a suitable all weather bike (b), I could very easily entertain a hub-geared, disc-braked belt-driven bike.

(a) which I'm not, (b) which I already have.

[zenitb]

If you could say what sprockets and belt you had whether CDN, CDX or CDX:EXP this would be very helpful.

In the OP case, Gate CDN 120t, to a 46t/22t driving a Nexus 8.

In my case (non-OP) the second sprocket I was given is marked "CDN" and is plastic (NB 46/22t setup like the OP).

My first sprocket lost teeth, was replaced under warranty and appeared to be metal, but the style of belt was the same so I am presuming this was CDN as well although I don't have it here to check the markings.

Interesting they changed the material though - all in vain unfortunately because the plastic sprocket broke in a different way (excessive wear) .. see next post (I am uploading more photos to show damage).

[zenitb]

Looking at the bits I retained it looks like I chucked out the belt. From memory it was the same as the first one - heavily worn with missing teeth. Shame I didn't keep it but I DID keep the sprocket and chainwheel in the vague hope I might someday rebuild the system.

Here is the chainring (beltring ??) - looks fine with a nice square end to the teeth.

Relatively unworn chainring

However look at the sprocket .. worn pointed plastic teeth, in fact if you look closely you can see a faint image in the plastic where the original tooth profile was.

Worn sprocket pic 1

Looking end on you can see the plastic has been "undercut" by the belt.

Worn sprocket pic 2

It looks to me as if grit got between the belt and rear sprocket and "ground out" the teeth resulting in the pointed sharp profile you see in the pics. The practical upshot of this was that if you put strong pressure on the pedals (eg stood up to pedal) the belt would jump - just when you least needed it to of course - and you would have to sit down, gear down and pedal delicately or just get off the bike. Note this was irrespective of belt tension - I used the Gates phone app to "tune" the belt to the correct tension on installation and every time I checked it.

I didnt have the heart to go back to the (long suffering) shop again with this and face another lengthy delay for parts. I picked up a Decathlon 1/8" singlespeed chain (KMC) for £6, slapped on a sprocket and chainwheel from ebay and have had zero issues since. It was a breath of fresh air to be able to be able to stand on the pedals whenever I liked.

See what you think ? If anyone wants more photos, measurements etc I can provide.

[Jupestar]

The sprocket is different, there must have been a older style one. Is the internal part of the sprocket which grabs onto the hub also plastic? Hard to tell from the photo, looks metal inner plastic outer.

It’s unfortunate the bike shop closed down, it’s a good bike and they obviously could maintain it. If they had he could I’m sure have got it sorted, his log book (if there is such a thing) was up to date.

I asked him how he found the chain today after two years on a belt, basically a bit noisier, but he could feel it engage quicker when he changed speed.