Gates Carbon Drive

[TT]

I have just got a Tout Terrain Metropolitan as my 365 days a year bike. I love it, hub gears, hub dynamo, integrated rack, hydraulic brakes and a Gates carbon belt drive.

But I have one question and seem incapable of getting an answer from official sources. Apparently the tension on the belt is important. if the belt is too loose all sorts of nasty things are likely to happen. And yet the documentation that comes with the bike doesn't give any indication of the tension needed on the belt. I have tried emailing Tout Terrain in English. I got a friend to translate and have tried emailing them in German. I have emailed Gates. No replies. Not brilliant for what is after all and expensive bike.

Anyone any ideas? Any suggestions gratefully received.

[jb]

I imagine as there is no real way of putting a lot of tension on other than by pulling the wheel (unless you have an eccentric bottom bracket) that they simply mean it has to be pulled tight rather than having a bit of slop like a chain does on a non dérailleur bike.
Their web site says half inch deflection in the middle with 5 - 10 lbs force. so you need a spring balance to pull it down with.

[Slidingpillar]

I just downloaded the tech manual from the Gates web site, cos it's a subject that interests me. And it just says use the figures provided by the bike manufacturer. Very helpful...

Not sure whose figures jb refers to, but the Gates 'Krikit' gauge goes up to 150 lbs so I'm dubious that 5-10lbs is not too slack.

I can confirm however that too slack that causes the belt to skip will rapidly cause it to wear out. (I've experience of similar belts for other uses).

Get the LBS to quiz the manufacturer quickly is my advice.

For what it's worth, it ought to work, Harley Davidson motor bikes have used a similar drive system for some years now. (And the new Morgan three wheeler will have one too).

[jb]

http://www.carbondrivesystems.com/support.php?lang=us
Its under Installation

150 lbs would bend the frame, that gauge may refer to the tension when pulling the belt tight, not the belt deflection in the middle which is 5-10 lbs.

[TT]

Thanks jb and slidingpillar, I think I will:

- get a spring gauge to check the 5-10lbs and 1/2 inch deflection approach immediately, and
- chase Bikefix where I bought the bike to see if they can get a response from Tout Terrain

The deflection method strikes me as pretty rough and ready given that the pressure to cause the deflection can vary by 100%

[thirdcrank]

TT

I speak as an inveterate worrier but I think you may be over-worried. You bought this bike as a fit-and-forget bike but it's becoming fit-and-fret. What was it that got you worrying? I presume this has started after you got the bike, or you would have looked for answers before buying. Is it possible that some smart alec has been winding you up a bit?

As the technology, if not necessarily the same strength of belt, is used on big motorbikes, it ought to be sound as a pound on a pedal cycle. eg No doubt a slipping belt is a bad thing, but riding a bike you would know PDQ that it was happening and you could tighten it up a bit, long before any damage occurred. If it was too tight, I imagine you would soon notice that it was hard to pedal. This is broadly the same idea with a traditional bike chain.

I can see how you are frustrated by the lack of info but that may just be evidence that the manufacturers are taking a similar line to me and have never anticipated anybody going to the lengths you are considering. If you do get an answer from somebody, it may be that they are busking anyway.

Finally, I don't claim to have any expertise on this - I was just attracted by the intriguing combination of GATES, CARBON and DRIVE and wondered what it meant.

[TT]

Hi thirdcrank

You could be right that I am overworrying - the belt isn't showing any signs of slipping - so everything is working fine and initial impressions are all good, see http://www.combingmyhair.com/?p=1075

That said, after buying the bike I learnt (forget where) that if the belt tension is inadequate it will cause excessive wear on the sprockets....

Who knows, maybe time alone will tell

[thirdcrank]

... see http://www.combingmyhair.com/?p=1075 ...

Nice pictures and an interesting read. I'd be thinking about a big front mudflap, especially for winter riding.

[TT]

Yep, I was surprised that for an all weathers bike there were no mudflaps, could be my first modification

[Edwards]

I was wondering about what type of belt it has until I clicked on the picture.
As this is a toothed belt you could do more damage than good by having the belt to tight. Basically it is the same as a car timing belt and I know that if is over tensioned the stretch will cause wear on the teeth of the sprockets.
A good rule of thumb is if you can turn the belt 90deg in the center between the sprockets using one finger and thumb it should be at a reasonable tension.
It does take quite a bit of force to get this type of belt to jump teeth.

[GatesTech]

TT,

There are several ways to measure tension. If you have the Gates Krikit gauge you will want it to measure 50-60 lbs on the gauge. There is also an app for the iPhone that can be found in the app store under Carbon Drive. With this app you can measure the sound wave the belt makes when you pluck it like a guitar string. The belt should measure 50-60 hz for your IGH hub. Please email me directly with any more questions you may have.

SP0222@gates.com

Thanks

[TT]

Thank you GatesTech, precisely the information I was looking for.

[thirdcrank]

TT

I'm glad you have had some success. This has got me fascinated. One of the good things about this forum is the shared pool of knowledge and experience. I hope that you will update this once you have obtained either the gauge or started strumming rhythms to your mobile. For dinosaurs like me, this is a glimpse of the future.

[TT]

'One of the good things about this forum is the shared pool of knowledge and experience.'

Quite agree thirdcrank.

I have an android phone, so will have to wait until I see a friend on Monday who has an iphone to test the tension - will report back

[TT]

Have now had a chance to measure the tension using the iPhone App. Really straightforward. Just ping the belt like a guitar string and the IPhone picks up the frequency. Did it three times and got almost identical readings averaging 63 Htz. So I am leaving things as they are and can now ride reassured that I am not prematurely wearing out.

Incidentally the iPhone App is free, previous tension measuring tools for measuring were £25+ for a physical tool and much more for an electronic tool