What other more powerful calipers fit the XS650 ?

Brembo 4-piston caliper has 38mm diameter pistons

Actually the Brembo 65 mm mounting, 4 piston calipers, have 30 mm and 34 mm pistons.

I now use a Brembo 12 mm master cylinder, which gives a 28.6 ratio. It works very well, with good modulation. I originally tried using my stock 14 mm M/C, but it was to powerful, as the ratio was only 20.98.

RG is absolutely correct on the 30/34mm dimensions and I was absolutely wrong. For purposes of using MMM's chart, it's total piston area is equivalent to four 32mm pistons.

The four finger grip is because of bigger master cylinder bore(I think even Yamaha went back and forth on brake feel ie: master cyl. diameters), if you put a 13mm bore master you will get a lighter feel.

Chris
Oakland, Ca.

ReycleBill said:

You might find it easiest to fit a master cylinder with a larger bore. Increasing the bore of the master cylinder while retaining the stock sized caliper would increase the PSI at the caliper.

Of course, doing that would most certainly require the stainless hose recommended by TwoJugs.

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Rather the opposite, I would say. A smaller master cylinder will give higher pressure and stronger brakes, but will make for a less firm lever. On my RD350A, going from the stock 5/8" piston diameter to a Brembo 13 mm improved the brakes a lot. I guess XS2 and XS 650 up to 75 have the same brake as the RD, so this applies directly to them.

There is one caveat with a much smaller m/cyl - if the floating type of calipers are in good condtion and not worn at the slider pin(s), then fine. However, I've found that old worn calipers can be bumped away from close proximity of the disc by rough roads and you use up valuable master cylinder movement trying to get that back. Not the kind of thing you want when you really need to brake sharply.
The problem doesn't really arise with opposed-piston calipers, as there are no sliding pins to wear and create slop in the assembly.

I recently got an FJ1200 (1992 model) front caliper. Should be an easy fit at least with mag wheel. Needs an adapter plate and an offset plate with the FZR600 rotor. I'll post pictures when I have something to show.

Pekka

The only way to increase braking power is to make the calipers squeeze the pads against the rotor harder.
You do this in several ways. Swapping to a caliper with more pistons is one. This works by spreading the internal pressure of the fluid over a larger area.
The pressure inside the caliper is controlled by the master cylinder. I don't know the exact pressure in the system, but lets say the stock M/C creates 200 PSI. The PSI is the same in every part of the system.
On the stock caliper it has a 38 mm piston. with an area of about 1.7 Square inches. So with 200 PSI pushing on 1.7 square inches you get the piston pushing with about 340 lbs.
Now If you added a second piston of the same size so you had 3.4 square inches of area this would increase the pad pressure to 680 lbs.
This would mean with the same pull on the lever you would get twice the pad force on the rotor, Or the same force but with half the finger pull.
On multi piston calipers you almost always increase the area.
Now at the other end, the M/C you do the opposite. Decrease the area of the piston to increase the line pressure. With the same pull on the lever with a 14 mm piston creates 20o PSI, making the piston smaller increase the pressure in the line. A 14 mm piston has an area of about 153.86 mm squared. Dropping to an 11 mm master is about 94.985 mm squared. A change of about 61%. so this will increase line pressure by 61% or 322 PSI.
This change with a stock caliper would increase the amount of force of the piston on the pads from 340 lbs. of force to 547 lbs. of force.
Just a quick look at the numbers the 11mm M/C with a single caliper has nearly the same force as using the 14mm M/C with two calipers.
So swapping things around you need to think about the balance between M/C and caliper.
Leo

Hey guys,

For dual disc brakes, has anyone used the Ducati Brembo master cylinder? It's 16mm..

http://www.ebay.com/itm/DUCATI-91-9...Parts_Accessories&hash=item19f4d2a390&vxp=mtr

I bought a $35 master cylinder on eBay and an 02 r6 caliper for $20. Had to file the caliper a little on the inside to fit the factory rotor and had to grind the backside of the caliper a little to clear the spokes. Made a bracket template and had someone mill it out of 1/2" aluminum (Brother in law did it for nothing!) Put on a stainless line and it works amazing. All for about $70. 3/8" aluminum would have worked but he had 1/2" for free so....

This is on my 76 btw.

This is the pandemonium kit and brembo on the left side of a XS front end, it looks pretty clean but you have to hack up the caliper a little:



Chris
Oakland, Ca.

klrx7 said:

I bought a $35 master cylinder on eBay and an 02 r6 caliper for $20. Had to file the caliper a little on the inside to fit the factory rotor and had to grind the backside of the caliper a little to clear the spokes. Made a bracket template and had someone mill it out of 1/2" aluminum (Brother in law did it for nothing!) Put on a stainless line and it works amazing. All for about $70. 3/8" aluminum would have worked but he had 1/2" for free so....

This is on my 76 btw.

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which side caliper did you use?

Right side. That's the side my rotor is on.

Where can I get a single caliper? I can only find sets!

Thanks

C-Los SD said:

Pandemonium Choppers kit $36 and brembo caliper (2 pin style) from a Ducati with a stock rotor work great! Just make sure you match it with the proper master cylinder. I use this kit on both my XS's with the magura master that MikesXS sells and the stopping power is like a modern
sportbike.


View attachment 288528
View attachment 288529

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Hi there, I know it has been like a decade lol however if you’re still here and you remember …that pandemonium brembo set up of yours, did you have to file off the back of the caliper to clear the spokes?
I’ve heard and read a mixed bag regarding the fitment of these.

Bountiful said:

Hi there, I know it has been like a decade lol however if you’re still here and you remember …that pandemonium brembo set up of yours, did you have to file off the back of the caliper to clear the spokes?
I’ve heard and read a mixed bag regarding the fitment of these.

Click to expand...

My setup is a 320 mm custom made ISR disc, 5 mm thick, offset 23 mm (measured from OUTSIDE of disc friction surface to mounting surface) Brembo 4 piston caliper with 65 mm C-C mounting holes. Spoked stock XS wheel. No filing required

Thanks @articXS as I am struggling to find any suitable upgrade of replacement discs without going down the route of your set up and adding spacers etc for a hefty price tag I am happy to try and have my 298mm dual disc(s) machined from 7mm to around 5mm with the faces drilled. My main concern is finding a caliper upgrade that’s not going to foul spokes without calving the back of a brembo or shimming a modern disc out within 2mm of the fork. I haven’t yet seen or read the best fit combo regardless of caliper mount.

My disc is very close to the fork sliders, yes. Maybe 2 mm clearance between floater buttons and fork slider. One thing to be aware of, is that a 320 or 330 mm disc will give more clearance between caliper and spikes than for example a 298 mm disc, due to the spoke angle.

Also, a disc made for a modern 4 piston caliper has a narrower friction "band", so will always be lighter than your oem 298 mm disc, even when thinned down to 5 mm

karhawk said:

This is the pandemonium kit and brembo on the left side of a XS front end, it looks pretty clean but you have to hack up the caliper a little:

View attachment 317503

Chris
Oakland, Ca.

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I have used early Triumph calipers also, they work very well. Off topic but nice 500!