Rear brake reduction

Bitza · Today, 03:49 PM

OK has anyone out there any experience/expertise to share, re going for a 220mm dia rear disc instead of the std 245mm as fitted to what was a 94 M900. My thinking is that 245 is probably larger than necessary, but would 220 be too pathetic?
Just did a comparison on the scales, 425gms saving of unsprung rotating mass does sound good to me.

Dukedesmo · Today, 04:19 PM

916 and variants (748/996/998) all use 220mm rear discs (with the same caliper as a Monster) and, whilst they are not renowned for their rear braking ability they are sufficient - IMHO the biggest problem being one of heat soak from the exhaust/engine cooking the fluid, making the pedal go soft.

Correctly setup and bled though the brake is more than capable of locking up the rear so, how much more does it need? and that on a heavier bike, albeit with a more forward weight bias than a Monster.

Bitza · Today, 04:33 PM

Who wants a bike renowned for its rear braking anyway?!
Thanks for that maybe not such a bad idea, especially since I've sawn off the pinion foot pegs.

Mr Gazza · Today, 04:47 PM

Didn't realise that the 916 series only had 220 discs, but that kind of proves that it would be enough braking power when working properly.
I was formally taught not to use the rear brake in an emergency stop situation, since it will be in the air if you're doing it right anyway, the still rotating rear wheel will act as a stabilising gyro to help you come back down in a straight line.

So I reckon it would be good enough for general and trail braking when you really don't want to temp a lock up.

I think that wavy discs are a bit lighter than normal round ones sometimes, but not always.
Preferably you would buy one that stated the weight to make sure.
For what it's worth I think Yamaha discs are compatible with Ducati for more scope.
Obviously Ti disc bolts will help with a few grams.

Not sure if there is enough room to make an alloy disc carrier worth the trouble?
I'm assuming you're already using an alloy sprocket?

Ultimately you will make more difference with a lighter wheel.
There were two versions of the Brembo three spoke wheel.
The early one had thicker spokes at the periphery. Later ones are thin at the periphery and thick at the base and are a bit lighter.

I think the much later Marchensi 5 spokes are lighter still, but not sure about interchangeability?

Mr Gazza · Today, 04:50 PM

.. Also there's a bit of a weight penalty to the floating rear brake set up, for hardly tangible efficiency gain. Fixed caliper is a lighter set up.
Especially if you're custom making the bracket anyway.

Dukedesmo · Today, 04:55 PM

Fairly sure you can get, at least for some bikes, aluminium/alloy discs.

Pretty useless I would think as they would wear too quickly but I'm sure I recall a friend fitting one to a Suzuki TLS1000 in the distant past as a weight saving exercise but retaining road legal status by having a brake...?

Otherwise Carbon/Ceramic discs exist (though not sure if anyone makes rear discs in CC) at a price.

Today, 03:49 PM	#1
Bitza Silver Member Join Date: Jul 2006 Location: Poole Bike: M900ie Posts: 518	Rear brake reduction OK has anyone out there any experience/expertise to share, re going for a 220mm dia rear disc instead of the std 245mm as fitted to what was a 94 M900. My thinking is that 245 is probably larger than necessary, but would 220 be too pathetic? Just did a comparison on the scales, 425gms saving of unsprung rotating mass does sound good to me. __________________ Bitza Last edited by Bitza; Today at 03:54 PM..

Today, 04:19 PM	#2
Dukedesmo Registered User Join Date: Sep 2010 Location: Leics Bike: M900 Posts: 2,907	916 and variants (748/996/998) all use 220mm rear discs (with the same caliper as a Monster) and, whilst they are not renowned for their rear braking ability they are sufficient - IMHO the biggest problem being one of heat soak from the exhaust/engine cooking the fluid, making the pedal go soft. Correctly setup and bled though the brake is more than capable of locking up the rear so, how much more does it need? and that on a heavier bike, albeit with a more forward weight bias than a Monster. __________________ M900, 916, LeMans II.

Today, 04:33 PM	#3
Bitza Silver Member Join Date: Jul 2006 Location: Poole Bike: M900ie Posts: 518	Who wants a bike renowned for its rear braking anyway?! Thanks for that maybe not such a bad idea, especially since I've sawn off the pinion foot pegs. __________________ Bitza

Today, 04:47 PM	#4
Mr Gazza Lord of the Rings Join Date: May 2013 Location: Norwich Bike: M900sie Posts: 5,990	Didn't realise that the 916 series only had 220 discs, but that kind of proves that it would be enough braking power when working properly. I was formally taught not to use the rear brake in an emergency stop situation, since it will be in the air if you're doing it right anyway, the still rotating rear wheel will act as a stabilising gyro to help you come back down in a straight line. So I reckon it would be good enough for general and trail braking when you really don't want to temp a lock up. I think that wavy discs are a bit lighter than normal round ones sometimes, but not always. Preferably you would buy one that stated the weight to make sure. For what it's worth I think Yamaha discs are compatible with Ducati for more scope. Obviously Ti disc bolts will help with a few grams. Not sure if there is enough room to make an alloy disc carrier worth the trouble? I'm assuming you're already using an alloy sprocket? Ultimately you will make more difference with a lighter wheel. There were two versions of the Brembo three spoke wheel. The early one had thicker spokes at the periphery. Later ones are thin at the periphery and thick at the base and are a bit lighter. I think the much later Marchensi 5 spokes are lighter still, but not sure about interchangeability? __________________

Today, 04:50 PM	#5
Mr Gazza Lord of the Rings Join Date: May 2013 Location: Norwich Bike: M900sie Posts: 5,990	.. Also there's a bit of a weight penalty to the floating rear brake set up, for hardly tangible efficiency gain. Fixed caliper is a lighter set up. Especially if you're custom making the bracket anyway. __________________

Today, 04:55 PM	#6
Dukedesmo Registered User Join Date: Sep 2010 Location: Leics Bike: M900 Posts: 2,907	Fairly sure you can get, at least for some bikes, aluminium/alloy discs. Pretty useless I would think as they would wear too quickly but I'm sure I recall a friend fitting one to a Suzuki TLS1000 in the distant past as a weight saving exercise but retaining road legal status by having a brake...? Otherwise Carbon/Ceramic discs exist (though not sure if anyone makes rear discs in CC) at a price. __________________ M900, 916, LeMans II.