Cycling UK Forum

Has anyone ever had one of these fail ?

Sort of.

My town bike is a Trek Soho de Luxe with belt drive via a shimano 8 speed hub. It was bought in 2010 and has been a great bike for low maintenance.

This winter the belt kept slipping off despite my best efforts to adjust the alignment and so on. Finally I was climbing one of York's many 'hills' when the thing suddenly went again and although I replaced the belt, there was no 'grip' from the freewheel whatever gear I tried.

Took it to Evans late January and after they looked at it they found the freewheel had gradually collapsed. Apparently it is aluminium alloy and not really strong enough; replacements are stainless steel at an eye-watering 94 squid plus a long wait since they have to be shipped from the far-east.

Anyway, I got it back fairly recently and it's all good again and I guess steel chain drive could have done just the same.

when you say 'freewheel' you mean 'sprocket', right?

The interface between the sprocket and the hub is narrow and is intended for a setup where the sprocket is made of hard steel. There is little scope for reducing the strength of this interface; even using a narrower 3/32" steel chain drive sprocket often causes troubles.

It ought to be possible to construct a belt drive sprocket that uses a steel part that interfaces with the hub driver and sandwich that between aluminum pieces that engage with the belt. At least one forum member has made their own belt drive sprockets by laminating laser-cut stainless steel parts.

cheers

No, I was thinking more 'freewheeel' than 'sprocket'.

Not sure how it was bust but the belt was still engaging with the sprocket which was freewheeling on the hub. In other words the pawls had ceased to engage. Anyway, as I said the new component is indeed steel and alleged to be much tougher than its predecessor.

(Wish I'd got the broken bit off them now!)

probably the remains of the sprocket were rotating freely on the driver as I described. In fact it would have to be that, else a new sprocket alone would not have fixed it. Nothing to do with any pawls.

This is a typical IGH sprocket


The afline hubs use the same fitting; the three small bumps are responsible for transmitting the drive. If the sprocket is made in aluminium then they will soon wear away. The fitting was designed with hard steel (and no preload) in mind.

cheers

That makes sense. It's a very expensive part considering how simple it seems to be. I guess because they don't make them in big numbers.

IME IGHs work best with 1/8" chain; a new SA sprocket costs £3 retail, and a good chain (eg KMC B1) costs £5. A chainguard stops your trousers from getting oily, and the drive is both efficient and direct, as opposed to inefficient and spongy-feeling.

Not a big fan of belt drives, really. Interesting that one place you don't see them is on folding bikes, where they might be quite good.

cheers

What advantages do belt drives have, how much does a belt cost, how long does it last?

Cyril Haearn wrote:What advantages do belt drives have, how much does a belt cost, how long does it last?

advantages

- slightly lighter than a typical chain drive
- quieter than a derailleur chain drive (maybe not an IGH chain drive)
- cleaner than a chain drive
- no need for regular cleaning or oiling
- may not extend as much as a chain in service (which does not translate to less frequent adjustments necessarily)

costs; lots to buy but...
... might last longer than a typical chain

Disadvantages vs a chain are

- much more expensive to buy (esp in bike-specific form with a centre ridge)
- sensitive to tension (belts may slip if there is not enough tension)
- sensitive to alignment (bushingless chains run a little out of line with little complaint whereas belt drives can be troublesome to set up)
- belt drives need more preload (which can wear BB and hub bearings more quickly than normal)
- the frame needs a split in it to be able to fit a belt
- roadside repair of belts is problematic (kits exist for 'get you home repair' on belt drive motorcycles, not sure about bicycles)
- belt drives are variously at bit stretchy and can make the transmission feel spongy (esp on bikes with big wheels)
- belt drives are quite a bit less efficient (can be tens of percent lost)
- belts don't allow so many choices of gearing vs chains (eg only a limited selection of belt lengths and sprockets/crankset rings available)
- belt drive cranksets need more clearance to the chainstay because the belt is wider than a chain
- to get variable gearing with a belt means you need to use a BB gear and/or an IGH
- belt drive conversions for bicycles are often poorly engineered (eg the aluminium sprocket.... )
- belt drive components are not widely available unlike chains
- foreign object damage possible with belts; eg a stone might get trapped betwixt belt and sprocket which will result in damage to the belt
- belts are not tolerant of various things such as chafing, creasing, ( and contamination with oil and /or water in some cases) etc and may fail prematurely if care is not exercised accordingly.

Thus I might consider a belt drive on a folding bike simply because of the cleanliness of it. But otherwise, I'm not much tempted.

cheers

Diolch yn fawr iawn
Seems like a no-brainer

Cyril Haearn wrote:Diolch yn fawr iawn
Seems like a no-brainer

I don't think it is a complete accident that belt drives are not very popular, even in applications where they ought to be most advantageous. For some the advantage of cleanliness appears compelling, but that is rare.

cheers

Brucey wrote:... Interesting that one place you don't see them is on folding bikes, where they might be quite good.

Decathlon don't seem to offer it in the UK but the top model of the Tilt folder range (the 940 on their French site, possibly other countries but I haven't looked) has a Gates belt drive running a Nexus 7.

€499,99
Ajouter au panier/add to your basket!

Brucey wrote:

Cyril Haearn wrote:What advantages do belt drives have, how much does a belt cost, how long does it last?

advantages

- slightly lighter than a typical chain drive
- quieter than a derailleur chain drive (maybe not an IGH chain drive)
- cleaner than a chain drive
- no need for regular cleaning or oiling
- may not extend as much as a chain in service (which does not translate to less frequent adjustments necessarily)

costs; lots to buy but...
... might last longer than a typical chain

Disadvantages vs a chain are

- much more expensive to buy (esp in bike-specific form with a centre ridge)
- sensitive to tension (belts may slip if there is not enough tension)
- sensitive to alignment (bushingless chains run a little out of line with little complaint whereas belt drives can be troublesome to set up)
- belt drives need more preload (which can wear BB and hub bearings more quickly than normal)
- the frame needs a split in it to be able to fit a belt
- roadside repair of belts is problematic (kits exist for 'get you home repair' on belt drive motorcycles, not sure about bicycles)
- belt drives are variously at bit stretchy and can make the transmission feel spongy (esp on bikes with big wheels)
- belt drives are quite a bit less efficient (can be tens of percent lost)
- belts don't allow so many choices of gearing vs chains (eg only a limited selection of belt lengths and sprockets/crankset rings available)
- belt drive cranksets need more clearance to the chainstay because the belt is wider than a chain
- to get variable gearing with a belt means you need to use a BB gear and/or an IGH
- belt drive conversions for bicycles are often poorly engineered (eg the aluminium sprocket.... )
- belt drive components are not widely available unlike chains
- foreign object damage possible with belts; eg a stone might get trapped betwixt belt and sprocket which will result in damage to the belt
- belts are not tolerant of various things such as chafing, creasing, ( and contamination with oil and /or water in some cases) etc and may fail prematurely if care is not exercised accordingly.

Thus I might consider a belt drive on a folding bike simply because of the cleanliness of it. But otherwise, I'm not much tempted.

cheers

Belts for cycles are a lot harder to get hold of in the UK, especially quickly. Chains aren't.

BarryP wrote:Has anyone ever had one of these fail ?

I've done 16,000 km so far with nothing to report, a chain would usually last me 2000 km in a similar setup.