Offset chain sprockets

[GT-UK]

I have been in touch with www.sprockets.stenor.com regarding them making sets of offset front and rear sprockets so that a 180/60-16 tyre can be used without problems. I have asked them for price quotations for 1, 20 and 50 sprocket sets. If the price is reasonable I would hope to supply forum members either myself at cost price or to set up some kind of group buy direct with Stenor. The costs indicated ( I suppose for a 1off sprocket) on their web site are:


Below are the estimated costs of special sprockets (prices include VAT but not Postage)

Manufacture of gearbox & engine sprockets £50+
Manufacture of gearbox sprockets with offsets £60+
Manufacture of small to medium sized basic flat rear sprockets £45+
Manufacture of medium sized basic flat rear sprockets £60+
Manufacture of larger sized basic flat rear sprockets £80+
Manufacture of dished and offset rear sprockets £75+
Retoothing gearbox & engine sprockets £50+
Retoothing drum sprockets and other larger sprockets £65+


If the same sprockets can be used for both 750 and 906 (and others) it would clearly be an advantage in terms of numbers. From suppliers of aftermarket sprockets I have found that the same 38-tooth rear sprocket appears to be used on both 750 and 906, but the 16-tooth gearbox sprockets appear to be slightly different. The 750 is 12mm wide and the 906 is 16mm wide. (As a new member of the forum I'm not yet sure how to include jpg images of the sprockets with a message - can someone help?).

Questions:
a) Is there any interest in a group buy of these offset sprockets at a discount? I was thinking of getting them made in batches of 10 or 20 sets at a time. If there is no interest I'll order a set just for myself and others can do the same if they want to.
b) Is a 16-tooth front and 38-tooth rear correct or is there a demand for other sizes?
c) What should be the offset? 8mm? Please only answer if you have direct experience of fitting a 180/60-16 tyre.
d) Is there a difference between the 750 and 906 front sprockets or would the same one work for both?
e) I notice from the Avon web site that on a 5-inch wide rim the Avon Cobra 180/60 tyre is 182mm wide x 630mm diameter and the Avon Venom-R 180/60 tyre is 180mm wide x 625mm diameter. Does anyone have similar dimensions for other makes of tyre? Avon says that the actual tyre width can vary by up to 2mm due to the nature of the rubber.

GT-UK

[GT-UK]

My first go at including images in a post. Hope it works. GT-UK

[GT-UK]

The top picture is for a 750, the 2nd is for a 906, the 3rd and 4th are for a 750 and 906 resp. and appear to be the same.

Sorry for the mutiple posts - I'm still learning how to do this.

GT-UK

[paso750]

b) Is a 16-tooth front and 38-tooth rear correct or is there a demand for other sizes?

correct is 15/38

c) What should be the offset? 8mm? Please only answer if you have direct experience of fitting a 180/60-16 tyre.

my guess is that at this point no one will be able to give a definitive answer. The 8mm you`re referring to were done offsetting one sprocket only which I wouldn`t recommend to copy. Offset should be as little as possible. I`d consider offsetting the rear wheel 2-3mm to keep the necessary sprocket offset as small as possible

e) I notice from the Avon web site that on a 5-inch wide rim the Avon Cobra 180/60 tyre is 182mm wide x 630mm diameter and the Avon Venom-R 180/60 tyre is 180mm wide x 625mm diameter.

According to the info I got from Avon long ago the AM42 (Venom R) was replaced by the AV72 (Cobra) (before the AM42, there was an AM22)

G.

[GT-UK]

I got the Avon info from www.avon-tyres.co.uk/motorcycle, the Cobra AV-72 dimensions from the datasheet link on www.avon-tyres.co.uk/motorcycle/cobra and the Venom-R AM-42 dimensions from the datasheet link on www.avon-tyres.co.uk/motorcycle/venom-r

Since this information is on the Avon UK website I'm assuming (a bad mistake I know) that both tyres are currently available in the UK. Also, they may not sell the same tyre range in every country.

If nobody can help with the offset info I'll buy a 180/60-16 AV-72, fit it to my bike and work out what offset is needed. That way an AM-42 should also fit ok.

GT-UK

[21783mike]

I will be watching to see how this goes as I will be interested in a set sometime in the near future.

[Duc906]

G'day GT
I have recently fitted a 180/60/16 Bridgestone tyre to the rear of my 906.
http://forums.ducatipaso.org/viewtopic. ... 91&start=0
The front sprocket is a 16mm/14 tooth and the rear is a 40 tooth.To get clearance between the tyre & chain all I had to do was
turn both sprockets around and fit a 5mm spacer between the front sprocket and retainer ring.I also modified the swingarm to get
more clearance between the circumference of the tyre and the cross bar in the swingarm.I'm not sure weather you will need to modify your swingarm to fit the Avon tyre,maybe someone else can help you with that information.Hope this helps.

Cheers Ken

[GT-UK]

H Ken,

Many thanks for that info. Is there any chance that you could accurately measure the diameter and width of the fitted Bridgestone tyre so that we can compare it to the size of the Avons?

Are the 14T and 40T sprockets standard for the 906?

GT-UK

[Duc906]

H Ken,

Many thanks for that info. Is there any chance that you could accurately measure the diameter and width of the fitted Bridgestone tyre so that we can compare it to the size of the Avons?

Are the 14T and 40T sprockets standard for the 906?

GT-UK

The 180/60/16 Bridgestone is 180mm wide and 620mm in diameter.
15/41 is the standard sprocket size for the 906.

Cheers Ken