Ducati Sporting Club UK > DesmoDue Race Series > DesmoDue - General Questions and Chat > Brakes????

[mat2hew]

Hi ya! y'all!

Just a theretical question iv'e not got my brain around yet,,

If you have a twin disk setup and you remove one, would you have to pull the lever harder or would it be more power to one disk or about the same?

My logic is...

a) if the master cyclindar works two callipers, surely it would work one twice as hard or is that half as well?

b) if you only have one disk, surely you only have half the breaking? or is that one disk twice as hard?

c) I don't know anyway...

I have removed one calliper and disk and the lever feels a little hard, lacking in feel, but i have put new pads in and I havn't ridden the bike yet and won't know until oulton park, the master cyclinder is from a 749 I think?


anyone wishes to take a guess (or if you really know the answer) I will test it at Oulton Park and let you all know! (see who knows what!)

Matt #72

[nogaromill998]

Ghost just worked all that out Matt, pm him.....

[injected]

I've already got a single disc set up on my DD bike.

With a m/cyl designed for 2 discs, you're pumping twice the volume of hyd fluid that you now need, in other words the pads move twice as far for a given lever movement than they did with two calipers. So you end up with roughly half the lever movement for a given pad movement, which means much less ability to modulate your braking unless you switch to a m/c that pumps less fluid, like a 16x18. I suggest you do that.

You do only have half the braking (limited by the amount of kinetic energy the disc can radiate as heat), but when I worked out the maths it showed that a DD bike needs to dissipate almost exactly half the KE of a 996 (slightly less weight, much slower), so I figured that the exact same disc/caliper/pad set up I have on the 996 ought to work fine on one side of the DD. And except for outbrraking myself a few times at Snetterton , it does.

[Ghost]

Ideally you want a master cyl piston area to cumalative caliper piston areas of 27:1 down to approx 23:1

Any less than this the lever is very hard and you have no feel for modulation, that lack of feel can also give a switch like tendancy to lock up the front.

Liken it to squeezing a rubber ball as against an egg, you can modulate the ball pressure easily but the egg through lack of feel just gives.

I was running a 916 I think master with one disc, yes it stopped but the lever was very hard. I have 4x34mm pistons in the caliper. I did the sums and I was at 13:1 ratio. So I now have a master with a 14mm piston this gives me a ratio of 23.6:1 and the modulation is great, trying it around an industrial estate.

Oulton will be tried in anger.

[AK]

i'd rather have a rider using 50% of 2 discs than 100% of one but thats my opinion.
never did us much harm running twin discs on bothour bikes over the 3 years

[SeeleyG50]

Hey Matt, I'd echo AK's comments.......................put it back on mate

[andys 900ss]

Ive had both and won the 2007 class b champs with a single disc setup.

But..... i have to agree with AK in that you can never have enough brakes but my RCS master cyl is turned down for low response as I tend to attack the brakes quite hard which has had me off a few times.

Andy

[Imola Duke]

I used a brembo/ducati single disc in 2008 and for this year took advantage of
the revised rule where we can use after market disc's. (i bought 2 new discs for the price of a good s/h brembo)
I must say i prefer twin disc setup as it gives that little bit in reserve....

[injected]

I've heard lots of people say the same thing, but I don't see why, when I can lock the front wheel in a straight line with a single disc, I'd want more then that 'in reserve'. And if a pad falls out, or a line fails, a 'reserve' won't help you either.

[nogaromill998]

I ran twin full floating Brembo discs last year, this year changed to a single wave disc. Saved 4 kg on the front by swapping discs, losing a caliper and going to a later front wheel....braking is far better than last year and as she steers better too I expect I'm a bit less likely to crash too ! Doesnt make me any faster tho, just a little less slow maybe !