Ducati Sporting Club UK > Model Specific - Discussion, Technical Problems and Help > 998 / 996 / 916 / 748 > Radial Master Cylinder Source?

[cl0nd0n]

Whats the major difference between radial capipers and P4?

Are these P4? Calipers

[beancounter]

Originally Posted by cl0nd0n

Whats the major difference between radial capipers and P4?

Are these P4? Calipers

No, they appear to be the 996 SPS standard calipers.

I took those off my 996 SPS and replaced them with the P4's - big improvement (in conjunction with cast iron floating discs).

BC

[antonye]

No, those are Goldline calipers which have 4 pistons, but two pads per caliper. They come in 40mm and 65 mm mounting.

40mm calipers have one pin holding the pads, in the middle:

You can also see that the two mounting points are at the "back" of the caliper.

65mm calipers use two pins, one over each piston:

You can see that the mounting points are much further apart.

P4 calipers only come in 65mm mounting but use 4 pads per caliper:


For all three type above, the bolts that hold them into the fork are fitted sideways in - ie, laterally mounted. The problem with this is that braking forces are applied over a very restricted area, the point between the mounting bolt in the fork and the bolt in the caliper itself. This can cause flexing if the load exceeds the amount of force that this area can carry.

Radial calipers are mounted radially - that is that the bolts go through the caliper and into the fork bottom in a radial arrangement. This helps to spread the load over a great area, ie, the full length of the bolt, as the force is now aligned with the bolt rather than in a shearing pattern. Thus radially mounting calipers are stronger, flex less and look more trick...

This is a radial caliper - note how the bolts don't go in sideways...

[cl0nd0n]

Thanks Antonye

So I would be best to go for some P4 calipers? Anyone got any for sale?

Then i need to find some 65mm fork bottoms! Any ideas?

Cheers

Chris

[antonye]

To be honest, the best thing you can do is get some decent pads in there first, as this can improve the feel of the brakes no end. Its all down to personal choice but I prefer Carbonne Lorraine SBK3 pads as they have excellent initial "bite" on them.

Second cheapest is to replace your lateral master cylinder with a Brembo radial, as this will increase the amount of "feel" (feedback) you get from the brakes. Again this helps your feedback of the brakes so it doesn't feel like two wooden blocks in your calipers instead of pads!

If you still find all that inadequate, then think about replacing the calipers and fork bottoms!

[Tonio600]

Good write up Antonye, thanks for that article / reminder

[antonye]

By the way, make sure that you have braided hoses as well, as the original rubber-covered hoses can degrade and bulge under pressure, which reduces the pressure being sent to the calipers so you get reduced braking effect.

Replacing the hoses is another cheap and easy job to do if its not been done already.

[multi600]

P4 callipers fitted straight onto my 1998 748BP I should check the bolt spacing on yours, I thought 748's were all the same.

Mike

[antonye]

Originally Posted by multi600

P4 callipers fitted straight onto my 1998 748BP I should check the bolt spacing on yours, I thought 748's were all the same.

Mike

No, early 916 and 748 came with 40mm mounted calipers.

It's the Ducati way - they changed sometime around 97/98, so there's a grey period when you could have had either!

[skidlids]

Usually a good throughput of 65mm later forks on Ebay for around £150 a pair
if going to P4 calipers diferent brake hoses will be required because of the banjo fitting is on the side and no longer on the top

There are alternatives for the 40mm mounts such as Brembo Billet calipers, AP racings 4 pots and 6-pots, I have a set of 4-pots going on my 996, Dallas has the 6-pots on his 998R race bike and I have a set of PFM 6-pots on my 998Hybrid. There also a few other calipers out there that fit the 40mm mount, most of which when fitted with a decent mastercylinder and good quality pads will do a fantastic job of stopping you