Vtec Abs Rear Caliper Piston Diameters?

[Veefer800Canuck]

Anybody with an ABS VTEC service manual handy, can you please list all 3 REAR caliper nominal piston diameters for me?

Thinking about picking one up off Fleabay to match my front RC51 calipers, but IIRC, the VTECS had different brake piston diameters and I wanted to compare to the sizes I have now on my '99.

Many thanks in advance!

[VFR-SPORT]

I have a 2002 Service manual for the VFR800/A in PDF format but I can't seem to cut/paste the page. It say the "REAR" Caliper Cylinder I.D. for all three is 25.400 - 25.450 mm or 1.0000 - 1.0020 inches with service limit of 25.460 mm or 1.0024 inches. There are differences on the front calipers left to right.

Caliper Piston O.D is 25.318 - 25.368 mm or 0.9968 - 0.9987 inches with service limit of 25.310 mm or 0.9965 inches.

[Veefer800Canuck]

Oh, so they're all the same?

OK, I shall compare to my service manual at home for the '99, thanks.

[VFR-SPORT]

Yes, the only different one according to the manual I have the the right front middle cylinder/piston. It is for the cylinder, 22.650 - 22.700 mm or 0.8917 - 0.8937 inches and for the piston it is 22.585 - 22.618 mm or 0.8892 - 0.8905 inches.

[Veefer800Canuck]

OK thanks again.

When I said different, I meant different from the previous iteration of LBS on the VFR from 1998-2001.

I'll post up tomorrow with my findings on exactly what mine are.

[VFR-SPORT]

Just looking on Ron Ayers Microfiche and the 2 outside pistons have a different part # than the center one, which according tothe microfiche is 27x27 whereas the 2 outer ones are 22x35. Now for the 2002 VFR800A listed there there are also 2 different # but much closely matched. 25x27 for the middle one but 25x35 for the outer 2. Diameters are the same but different lengths for the 2002 but different diameters and different lengths for the 1998/9.

[Veefer800Canuck]

OK, mine are 22.5, 26.9 and 22.5

Now to do the math, as the ABS model, they are all 25mm if I'm reading things correctly.

[Veefer800Canuck]

OK, according to me :fing02: my exisiting rear caliper has 1367.5133 square millimeters of piston surface area.

22.5, 26.9 and 22.5 mm pistons

Eat slice of Pi, add scoop of ice cream, eat more Pi, I love Pi, can I have some more Pi? :cool:

The Vtec ABS rear caliper has 1471.875 square millimeters of surface area, or 7.63% larger.

25, 25, 25 mm pistons.

Staying with the same size master cylinder I have now (14mm) should then net me an increase in clamping force at the disc in the order of 7.6%

That should play well with my new wavy rear rotor, and also in light of the LBS delinking I did during the front end swap.

Going from the VFR 17mm rear master down to the CBR 14mm rear master back then helped the rear brake immensely, but it was still a little less powerful than I would have liked.

For $40, I can get a VTEC800ABS rear caliper which will perfectly match my gold RC51 front calipers and hopefully bring my rear brake up a notch in terms of braking ability, which it needed anyhow. Win, win, win?

[Veefer800Canuck]

Going, Going, GONE! :fing02:

[SEBSPEED]

Nice work, you should run a stainless brake line through the swingarm while you're back there! :fing02:

[JZH]

I suppose it's a straight swap?

Has anyone ever fit a "normal" single-piston rear caliper to a VFR? I've got a couple laying around somewhere. CBR600F4 and RC51/SP1, I think. Smaller and lighter than OEM VFR. Should be pretty simple--if you consider making a new adapter bracket "simple", that is!

Ciao,

[Veefer800Canuck]

I suppose it is too, looks like it'll fit, but I'll find out. Watch this space! :rolleyes: