A REAR BRAKE ANSWER???
 

Just reading in motorcycle news that Aprilia say that using DOT5 fluid in their rear brakes sorts the going soft problem.

Does it work on a Ducati?

Has anyone tried it?

Cheers Mike

I already use DOT5 and it still goes soft...

I think it's a general design fault in the way that the rear caliper is mounted in relation to the master cylinder and the run of the hose.

The SS has one really demon sharp rear brake and has never required bleeding, yet it uses the same system components. The difference is that the master cylinder is mounted vertically and not horizontally, and the caliper is mounted above the line of the m/c as it sits above the rear axle and not below.

I know the monsters use this configuration too, and also the 999/749 have gone back to mounting the rear caliper above the rear axle, but retain the horizontal master cylinder - do these suffer the same? If not, I'd be tempted to deduce it's just the location of the caliper.

I run DOT 6 and it isnt that bad. they stock it in the demon tweeks catalogue

never use the back brake...

...but then only go out on dry roads.

Or get your bike MOT'ed I presume?

Its approaching MOT time!!!!!

The only time it will ever get used:o

Mine got MOT'd at the weekend. Not so easy to sneak under the radar now with the new computer methodology.

My major worry was the back brake as it really is useless, but it did stop the rollers eventually with a good stamp and when the numbers were fed in to the computer it said PASS ! ! ! ! Mightily relieved!

Luckily don't have the MOT worry here on the Isle of Man :cool:

Has anyone used a mityvac? I did a search and there appears confusion over the instructions/units efficiency:puzzled:

Fit a 4 pston caliper to make it work at all.

1. Take the caliper off.
2. Take the pads out.
3. Squeeze brake pedal.
4. Spay caliper with brake cleaner.
5. Take one piece of Brick Banding and wrap round exposed brass pistons.
6. Clean all the gunk off brass piston.
7. Apply pink brake grease.
8. Squeeze pistons back in with finger pressure.
9. Put new pads in.
10. Put calipers back on bike.

Do this every few thousand miles, brakes will work.

I use a mityvac for brake and clutch,works well.

Me too. Once a rear brake has gone really soggy you'd be there forever bleeding it conventionally.

As for keeping it firm (oooh errr missus etc) I've said it before and I'll say it again: wedge a socket/conveniently shaped piece of wood/whatever between the brake pedal and the frame boss above it and leave it overnight. In fact do that every night.

It does work, really! :)


I'm sure antonye's right about the 748 brake v. the SS brake: the rear on my 750SS was fine. OK. the disc's 10% bigger but there's a lot more than 10% performance difference!




[Edited on 20-7-2005 by moto748]

don't get DOT5 and DOT5.1 mixed up. They are different animals and the seals in Brembo's don't like the DOT5.
The SS, M, ST's use a different caliper to the SBK's. The pads are certainly different. Smaller in the SBK.
I think the pistons are smaller, also hence the decrease in performance.

Thanks for your replies, I am now confused about which brake fluid to use and whether its worth changing from DOT4 at all.

Will 5,1 make a differrence to the brake going soft?

Are the others who are using DOT 5 aware that it messes the caliper seals up?

Interesting on my s4r the caliper is undeslung like my 748s i had, so guess i have the same caliper as the 748. The s4r works better than the 748 but not much more. This may be due to the master cylinder being at 45 degrees.

I also found my 748 and s4r brakes from new worked once u bed them in slowly and use them regularly. The disc on the s4r looks to be bigger to hhhhmmm:o

Doesn't the S4R use exactly the same rear end as the (old) superbikes, as in a single-sided swingarm?

Not sure if its all the same as the swingarm is tubular, the disc certainly seems bigger:D:D

Do NOT use Dot 5 - you need to use DOT 5.1. Big difference and if you mix them you will probably just pool moisture in your caliper which will lead it to rusitin on the inside where you cannot see.

My suggestion is , to take teflon tape and wrap the bleeder (plumbers tape). The bleeders are known to allow air in, but not enough space to spring a bad leak. Not saying that is your issue 100%, but have cured quite a few Duc's this way.

:o

I have taken a look at the rear master cylinder when the pedal is pressed. You can see that the master cylinder moves by a heck of a lot.

It appears that the bracket that holds the master cylinder is not up to the job. I intend to make a new one from decent ally plate and add a method of fixing a small heat shield for the exhaust pipes.

I think that with the master cylinder being held firmly and correctly with no flex when the brake pedal is pressed and a heat shield could do the trick.

And yes, my brake works ok but I reckon it could be better.
:bouncy:

DC:burn:

The other problem is that the whole master cylinder assembly is bolted directly to the engine cases. It's not just the heat from the exhausts you've got to worry about.
I've tried "insulating" the assembly from the cases with little/no success.

I'd not thought of the bleed nipple letting air in. A very valid point and worth a try :cool:

Quite a fascinating topic!

It would be quite a coup if some DSC member could design an improved rear brake.
So many ideas have been mooted: the fluid overheating, not enough fluid in the system, relocating the master cylinder, Aprillia calipers, leaking bleed nipples etc etc.

I guess many of them are partial causes. I certainly think Go Falfer could be on to something about the nipples. They always seem to weep a few bubbles in the tube when I connect the mityvac to them.
But then, I can't be sure it's not leaking into the tube past the outside of the nipple from the atmosphere.
At least, that's what I assumed before.

Brembo had some issues with the bleed nipples when we were working on some bikes that were out of spec. The location/placement of the master does not help the sitaution either with all the heat transfer.