Front cog
 

To change or not to change, that is the question.
If yes, to what and from where do I buy,

Paul of London Heathrow

Yep - well worth doing - try this lot;

http://www.bandcexpress.co.uk/cgi-bi...l?cat=SPR-ROAD

Tim

I believe that Amsterdam have lots of spare cogs from thieir windmills.:lol:

14 tooth?

Will this make the speedo inaccurate?

no speedo runs off of the front wheel...............

I would go up on the rear sprocket rather than down on the front....... less stress on the chain with a more powerful bike than a 748 that has 14 as std...........and you could have a bling sprocket carrier.......

But if you go up on the rear you will shorten the wheelbase , i run a 14 tooth on my 998bp althought the S is up a few brake hp

You could spend the money and put a Renthal carrier on the rear change the chain & sprockets at the same time that way you can keep the wheelbase std or go longer

I have and would allways go for a longer chain to keep the eccentric at the bottom and even 5 o clock as you look at it sprocket side!

besides if you fitting new sprockets you really out to fit a new chain anyway!

why will there be more stress on the cog ?

let me make you think a little... before I answer this one

the diameter of the cog is smaller ?
It is subjected to the same power ?
The chain will transmit more or less power ?

Rather than power think pressure, clearly for a given chain size a smaller number of teeth mean a smaller diameter, means a larger pressure on each tooth! IMHO:o

See Tales of the Front Sprocket here:

http://ducatisportingclub.com/xmb/vi...=9386#pid78060

OK then, i'll ask you some more questions to make you think about this one ...

1.pressure ? I think you should think more of compressive stresses in the sprocket material.

2. The sprocket is still transmitting the same power, but at a slightly different RPM (as you have altered the gearing)...so what about thermal stresses ? think of this... sprockets are transmitting power through friction..friction causes heat.... and the original sprocket was of larger diameter, ie larger surface area, and can therefore dissipate this heat more efficiently. So now you go down one tooth and the diameter is smaller, ie the surface area is also smaller, so the sprocket theoretically is hotter, then the larger one.

Now think of this.... some of that heat is dissipated through windage...ie as the sprocket rotates, air is passed over its surface, and cools it. However some of that heat travels along the drive shaft, and is dissipated through radiation, convection, so surely the smaller sprocket therefore transmits more heat along the shaft...have I got you scratching your head yet.

Next time you come back off a ride, touch the rear and front sprockets, and tell me what you find ?

We have to think of thermal stresses as well as mechanical ones !

From your quote, you are saying that there is agreater stress on the 'tooth' but surely the teeth are of the same form shape and size as the larger sprocket...arent they ?

Of course they are, but we may not have the same number of teeth in contact with the chain as we would with a different size sproket.....
:devil:

I suspect you will do as you please..............!:P

think of all the extra gear changes.....what about stress on your toe?

Just fitted a new front sprocket on my S4R yesterday, gone from a 15 to a 14 tooth. A lot easier to ride in trafic, and pulls better in top gear from lower speeds aswell. worth it even if you loose a few mph top end !!

p.s. noticed a bit more chain noise since fitting it, more like a whine, chains adjusted perfectly though. Anyone else encountered this ??

Are you sure about the noise .... are you looking for a noise / problem and just became more aware of the noise ?

At the end of the day 748's and 749's have 14t front sprockets as standard with the same size chains as 9** style bikes. OK the 9** puts out more power than the 748 / 749 .... but I would have thought it should be ok. Plenty of people have swapped the 15t for 14t and there are no horror stories. If it was a dangerous modification with problems I would guess that it would be all over the DSC forum.

[Edited on 6-5-2006 by Carbon749]

I think it would be interesting to try to correlate 14-tooth sprockets and undersized (weaker) 520 chains with the chain failures (and case damage horror stories) that are so often reported here in the DSC forum. Chain tension is higher when you use a smaller front sprocket.

[Edited on 5-6-2006 by Shazaam!]

Good point, most of the chain snapping stories seem to blame the DID chain and don't mention the sprocket sizes.

Still have this persistant thought in my mind that 14t fronts are standard fit on 748 / 749. The power output from some of the newer 749 is comparable to the power from older 916's. Ducati must be happy with the power output matched with the 14t sprocket.

Test rode a few 996s before buying mine and far preferred those with a 14 front. I discussed the front/back issue with Rich & Dean @ Louigi Moto and they told me they had never seen any problems with running a front 14. Good enuf for me. :burn:

Just stuck a new 14 on mine :cool: I have a new Afam rear sprocket (£59) that bolts straight on with no need for Carrier but no time to fit it yet.

also fitted new front wheel brgs and new rear pads tonight !

Age

So you won't be on the SV for tomorrow's SWB rideout then?

Nope

The Duke will be out for a good thrashing !!!! :cool::cool:

Why you wana come ?

Age