Ducati Sporting Club UK > Model Specific - Discussion, Technical Problems and Help > 998 / 996 / 916 / 748 > sprockets and in bits

[smilo006]

On a track day, bike starts to make a nasty noise. Put it on the rear stand to check, Put in neutral and checked rear wheel was free. Revved upto @6,000. Big bang, chain flies out the back accompanied by bits of one link plus (as I later found out) 2 rear sprocket teeth. On the way out the chain also knocked my rear hugger breaking the rear support.

******* thing had jumped into gear.

However now need new items. When I bought it (996R), it had a 14 tooth Renthal front, 36 back with a Renthal quick changer and Regina chain.

See no need to change teeth sizes and likely require a Renthal front and back sprocket to fit the quick changer.

Any reason to change this set up, for example different chain than Regina or is there any benefit or advantage of 520 over 525 chain?

Anyone know of a good (cheap and quick) supplier of said bits or part used going?

Fortunately the nasty noise was a loose flywheel.

[antonye]

520 is lighter than the 525 and reduces the power taken by the drivetrain, giving you more power to the back wheel - also less inertial forces if I understand it correctly?

Don't know if you'd be hitting the power limit with a 520 chain on your bike though...

I used B&C express to source a Tsubaki chain. In hindsight their top-of-the-range Omega Gold is *too* big for the 748. Stick with the Renthal and matching sprockets. If it ain't broke...

http://www.bandcexpress.com/

Renthal Front 14t = £25.40
Renthal Rear 36t = £31.65

TSUBAKI SIGMA XRG X RING GOLD (94 link) = £75.73

Free normal delivery (order over £100), total price = £132.78 to you sir!

The 520 versions are same for front, £29.56 for rear sprocket.

You may want to go for a Regina or DID chain, but these are around 120 quid each.

[smilo006]

Thanks.

Will likely need a 96 link or at least that was what was on it.

Will send the bill to Ducati.

[antonye]

Sorry - that was a 96 link ... just my bad typing

[Shazaam!]

My suggestion is to keep the 94-link 525 chain size. Perhaps even change to a 15/39 (that will give you the same gearing) with a 96-link 525. Here's why.

To give you a reference point, the 996R comes with a 15/36 gearing with a 94-link 525 chain from the factory. The peak torque output is 101Nm.

Ducati bike models have a wide range of torque output and the size of the chain and Ducati’s selection of sprockets reflect this range of outputs. All Ducati current models, except the 748 and 749, come with 15-tooth front sprockets. The 748 and 749 series (with the exception of the 749R) all have torque outputs below the 78Nm of the original 916, so they are supplied with 14-tooth front sprockets. The 748’s get 520 chains. The more powerful 749R (82Nm) is 15-tooth.

The 749’s get 525 chains, probably more for parts standardization than for strength. I remember from the product introduction that that was one of the major design objectives of the new models.

Starting with the higher torque 916-series (and 749R), and continuing with the 996, 998 and 999, the factory moved to a 15-tooth front sprocket and a 525 chain. Why? Because more torque means more chain tension and a 15-tooth front sprocket lowers the tension in the chain by seven percent. A 525 chain has a tensile strength that’s ten percent higher. So you get an overall 17 percent stronger setup.

Still-higher torque SP, SPS, R and Corsa models output over 100Nm so how do they survive with 14-tooth sprockets and light-weight 520 chains? That’s easy. Once you get over a certain torque level (for a given weight bike) the bike will wheelie before the chain tension exceeds it’s strength limits. At least for awhile ... chains on these bikes don’t usually see 15,000 miles of service.

So, what does this suggest about changing our final drive components. Four things.

First, as a general rule, it’s better to increase the rear sprocket size to avoid the higher chain tension resulting from a smaller front sprocket. Changing from a 15 to a 14-tooth front sprocket will result in a seven percent higher chain tension.

Second, the heavier the bike, the higher the chain tension needed to make it wheelie and the higher the maximum chain tension it will experience. So, a 680 pound 916-plus-rider will generate a higher chain tension than (say) a lightweight Corsa-plus-jockey or even a Suzuki GS-X. When a chain under tension elongates 10 percent, it needs replacement - frequently for a Corsa bike.

Three, combining a change to a smaller front sprocket with a change from a 525 to a 520 chain on a higher-torque model Ducati will significantly weaken the final drive load capacity. Reports of chain failures are common enough, so it may not be wise to ignore this point for the sake of saving 275 grams of chain weight.

[Nattyboy]

Smilo..you have a U2U..

Cheers
Nat

[smilo006]

Brilliant site. So much info and people willing to take the time to share it often over again with us newcomers.

Have decided thus far to go for 525 chain, 15 front and 39 rear 96 link chain. Shazaam's arguements are good enough for me.

have the offer from B&C all in for £130.

Ducati dealer here has offered a 15 front, 39 rear and std Ducati DID chain for @ same price as B&C above. Natty has offered an 996 SPS pack (15,36, DID)for £100.

Only use the bike now for track days (16-20 days per yr).
To ride it on the road here would cost @£20,000 in tax.
So is there any advantage to go for std Ducati gear standard gear or just get on with it and keep the Renthal quick changer and buy from B&C.

[TP]

Don't mean to hijack the thread but I have an interesting question - if you wanted to really lower the gearing on a 996, say 14t front and 39 rear what chain would you recommend?

Is anyone currently running this gearing?

smilo006, I would probably go the quickchanger route so you can swap around cheaper if you decide to later.


[Edited on 29-6-2004 by tp-996]

[smilo006]

Saw a bloke who said he was running a 48 rear on a 996 (gear ratio 3,2). Came off on day 1 and broke his shoulder and the bike on day 2.
Says it all really. Too much of a good thing?