Belt drive slipping on Trek Soho?

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Belt drive slipping on Trek Soho?

Postby Macc_Bob » 24 Feb 2011, 11:23am

Hi, this is my first post to the forum. I've done a forum search and couldn't find anything sooo....

I've got myself a Trek Soho October 2010 for commuting. I must say I think it's an ace bike for the job and has been (mostly) problem free throughout my winter commute. However, over the last month or so I've noticed that sometimes when I'm out of the saddle to heave up some short incline there's a horrible clunk which is also felt through the drive chain and the pedals skip forwards slightly. It seems to happen irrespective of the gear chosen. I can't be certain but it seems to me that belt tension has reduced since new. Has anyone experienced or heard of a similar problem? Googling didn't show up anything.


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Re: Belt drive slipping on Trek Soho?

Postby geocycle » 24 Feb 2011, 12:41pm

Welcome to the forum. I've no experience of belt drive but are you sure it is the belt that's slipping or is it the rear hub? I assume you have tried tensioning the belt by sliding the dropouts backward.

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Re: Belt drive slipping on Trek Soho?

Postby Macc_Bob » 24 Feb 2011, 12:50pm

I haven't tried tightening the belt yet, I'm ashamed to say I'm definitely out of my comfort zone with the mechanics of this bike: belt drive; hubgear; disk brakes it's all new to me. Will try adjusting the dropouts this weekend.

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Re: Belt drive slipping on Trek Soho?

Postby gilesjuk » 24 Feb 2011, 1:21pm

Could be the pawls not engaging in the hub, on a hub gear it is a little hard to get to compared to a freehub.

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Re: Belt drive slipping on Trek Soho?

Postby AndyA » 24 Feb 2011, 2:07pm

Sounds like there is not enough tension in the belt drive. Gates have information about the correct tension here ... 728257.pdf . You also have to be careful with the belt as it's possible (and quite easy) to damage the belt, see ... 728288.pdf . It's also a good idea to clean the belt with soapy water occasionally to remove mud and debris as they will speed up wear on teeth.

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Re: Belt drive slipping on Trek Soho?

Postby Macc_Bob » 24 Feb 2011, 2:14pm

Excellent thanks for that! Good links.


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Re: Belt drive slipping on Trek Soho?

Postby Elizabethsdad » 24 Feb 2011, 8:53pm

Welcome to the Trek Soho commuting club - I too love my Soho. I sometimes get that slipping clunk such as you desribe and I am pretty sure it is coming from the hub gear. It usually occurs when I have changed down severall steps quickly slowing or stopping for a junction and then trying to get going again quickly by putting the hoof on. The only problems I have had with my Soho have been partly self inflicted trying to repair punctures on the rear wheel and then making a c**k up of putting the back wheel on. Fortunately my local bike where I bought it has been very good at putting it right and I have now got a Schwalbe Marathon Plus on the rear with a gren slime inner tube. A bit overkill I know but hopefully it means the next time the wheel has to come off it will be for a replacement tyre - unless I manage to completely crunch the internals on the hub gear first. It would be great to start seeing some other CDS equipped bikes in the UK - I'd like a second bike for leisure rides and occasional shopping trips and I like the look of both the Raleigh Alley Way and the Globe Live 3 but the only seem to be available in the US at the moment.

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Re: Belt drive slipping on Trek Soho?

Postby Macc_Bob » 23 Nov 2012, 9:33am

I know this thread is ancient but I thought I'd update with my experiences as it might prove useful. I bought a tension tester from Carbon and found that the belt had stretched slightly seemingly. After careful adjustment of the tension it's been fine since.

I have also been experiencing an irritating problem whereby after a few kms the edge of the belt just starts rubbing on the flange of the chainring. Checking the chainline and the centring of the wheel everything seemed ok but the rubbing persisted. An email to Carbon had them recommending using a small amount of dry silicone lube on the belt. This sorted it and only appears to need refreshing every few months so now the bike is running disturbingly quietly!

Having also fitted drops and the Versa VRS8 brake levers/shifter I now have my ideal commuting bike.

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Re: Belt drive slipping on Trek Soho?

Postby [XAP]Bob » 23 Nov 2012, 12:22pm

8 thought belts didn't need lubrication :)
A shortcut has to be a challenge, otherwise it would just be the way. No situation is so dire that panic cannot make it worse.
There are two kinds of people in this world: those can extrapolate from incomplete data.

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Re: Belt drive slipping on Trek Soho?

Postby Malaconotus » 24 Nov 2012, 1:16am

When the belt on a Trek Soho is too slack, it can skip under load. When out of the saddle this produces something more akin to a rifle crack than a clunk. DAMHIKT, but my belt is now correctly tensioned.

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Re: Belt drive slipping on Trek Soho?

Postby Littgull » 24 Nov 2012, 6:46am

I'm another proud 'member' of the Trek Soho belt drive (hub geared) owners club. I bought my bike in May 2010 from Leisure Lakes, Bury (ordered in - not a stocked bike). I have clocked up over 8000 miles in that time almost entirely on my regular 22 mile daily round trip commute from Littleborough to Bury and back. In all those miles I have had no problems at all with the bike (it has run superbly) until the last few weeks where the belt has jumped occasionally and there has been a 'cracking' noise particularly when I pull away from a stop start position, I took my bike to our LBS in Littleborough (The Ride stuff) where the very helpful owner diagnosed sheared off 'teeth' on the rear wheel sprocket - very sheered off too on many of the teeth. He also pointed out that the sprocket was not the pukka trek sprocket but an inferior quality one - supplied on the bike from new. Anyway, the upshot is that a new sprocket was ordered direct from Trek and fitted. The proper trek Sprocket from Trek comes in black rather than the clear translucent colour rear sprocket that was supplied with the bike. Result - problem cured - no belt slipping, no cracking noise and back to a silent reliable Soho

I remain amazed that belt drive bikes (particularly with hub gears) have not become more widely popular.

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Re: Belt drive slipping on Trek Soho?

Postby LollyKat » 24 Nov 2012, 10:31am

Littgull wrote:I remain amazed that belt drive bikes (particularly with hub gears) have not become more widely popular.

I expect they will in time but a lot of us canny folk prefer to wait and let the early adopters sort out initial 'teething' problems. :)

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Re: Belt drive slipping on Trek Soho?

Postby BeeKeeper » 24 Nov 2012, 11:16am

The problem with a traditional belt drive is it is one piece and unlike a chain cannot be split. This means, with conventional bike design, the frame has to be split somewhere, (either in the chain or seat stays) to allow the belt to be fitted. This creates a point of weakness. Jointed belts do exist but I think they would need to be very wide to be able to cope with the forces and again, the joint would be a point of weakness. ... elting-38/


Note the Surly tensioners in the shot above - the little "horns" sticking out are bottle openers. That's what I call good design!

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Re: Belt drive slipping on Trek Soho?

Postby mig » 24 Nov 2012, 11:47am

what can a belt do better than single fixed/freewheel with a chain?

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Re: Belt drive slipping on Trek Soho?

Postby Brucey » 24 Nov 2012, 12:00pm

Although I am not necessarily a passionate advocate of belt drive (I think they have their place, but I worry about damage/field repairs on MTBs, and the belt preload knocking out the hub /BB bearings, amongst other things), I'm not sure the weakening effect of a seatstay break is such a big deal.

The loads in the seatstays are generally not that high and are mainly compressive; I am sure that there are many other (stronger) solutions to this joint than one (feeble looking) chainring bolt loaded in shear. There are lots of frames out there with replaceable dropouts etc (for different wheel fittings) already that use designs that could be adapted for this purpose.

However, simply because it adds cost, I don't think that many 'standard' frames will have such a fitting on them, unless it becomes popular, in which case we have a chicken/egg problem. So until then, this effectively 'nicheifies' belt drive to a) those who can be bothered to convert an extant frame (who are probably enthusiasts and therefore might well make anything work) and b) frames and bikes that are designed for belt drive from the word 'go'.

It'll be interesting to see how things pan out.

BTW in theory a belt drive offers a backlash-free fixed gear drive; I'd quite like to try that, since my experience is that this is only ever a temporary state of affairs with a chian.