i may try and upgrade but unsure if i will need to mill a adaption plate

You'll need an adaptor plate. The offset for the mounting holes is completely different for the two types of caliper. In truth though, having run both four-pot and two-pot calipers on a Moto Guzzi T3, I found that the difference in braking effect was almost negligable so I went back to the two-pot calipers for simplicity. Weight-wise, the T3 and the K100 are pretty close; additionally, the calipers are the same diameter pistons so the comparison is a valid one. The K100 caliper is coded P08 and the Guzzi caliper is coded F08 (although it's sometimes incorrectly called P08 too). The difference between the two is that there is a 4mm greater offset for the mounts on the F08 and P08 has threads in the mounts, but the bodies are identical.

Dai wrote:You'll need an adaptor plate. The offset for the mounting holes is completely different for the two types of caliper. In truth though, having run both four-pot and two-pot calipers on a Moto Guzzi T3, I found that the difference in braking effect was almost negligable so I went back to the two-pot calipers for simplicity. Weight-wise, the T3 and the K100 are pretty close; additionally, the calipers are the same diameter pistons so the comparison is a valid one. The K100 caliper is coded P08 and the Guzzi caliper is coded F08 (although it's sometimes incorrectly called P08 too). The difference between the two is that there is a 4mm greater offset for the mounts on the F08 and P08 has threads in the mounts, but the bodies are identical.

Were you just changing calipers or the whole system including the master cylinder?

On K bikes the four pot calipers AND the 20mm master have much better braking feel at the lever.

Master cylinder included, Duck. I used a Suzuki one (GSX 750? - can't remember now) that drove a pair of four-pot calipers on the original bike. Sometime last year I took a look at those calipers again with the intention of overhauling them for possible re-use on a K, but apart from having a cast 'Brembo' on them, there was no part number. I stripped them and measured the pistons and found two things:

1. the pistons are the same size as the smaller one in the BMW four-pots and
2. Brembo deprecated them years ago, so no overhaul kits.

The thought of buying eight BMW four-pot overhaul kits just to get eight piston seals made my wallet curl up and whimper in the corner. So far I haven't been able to find another caliper that runs the same size piston but I only searched on and off for a few weeks.

To get back to the OP: if you're looking for four-pots to go on the chair, these are a lot easier to fit

https://www.ebay.co.uk/itm/165259288172?hash=item267a389e6

I'm not suggesting you pay that much! They do come up cheaper - I got two sets for less than the price of one new caliper for my Guzzis. I measured a pair up for the K and discovered that the adaptor would consist of a piece of (IIRC) 30mm x 15mm ally (or steel or whatever). The calipers are designed for a disc of slightly larger diameter than the K front disc, so they need to be pivoted slightly outwards to move the pads downwards to get a full bite on the disc. All that meant was that three mounting holes were in line and the fourth one (second from the top i.e. the top caliper hole) was slightly outboard of the other three by about 5.0 mm. The catch turned out to be that (as you can see) the calipers are threaded, so to hold them to the adaptor they had to be secured from the inside by a 10mm allen button head, then the adaptor bolted to the forks.

If you want to go that route, PM me as I know I still have the POC adaptor that I made. However, bear in mind Duck's comment about needing the 20mm master cylinder.

thanks for the help again , its for the chair thing im getting involved with for a mate , he has the idea but needs me to do the work   not really my thing or time as i have other projects and work to fit in , fingers crossed he will change his mind

This setup is hands down the best front brake system I have ever felt on a BMW, bar the newer monoblock Brembo S1000XR's system. It starts with the K1100RS Marzocchi fork & triple tree, an R1150RT front wheel (a K1200RS/GT wheel can be subsituted), custom made axle & spacers, 320mm diametre discs (use either 4.5mm or 5mm thickness) from early R12RT/K13GT,R,S/R1150/early R12R,S, etc., Flat headed Torx screws of 8x27mm length to clear the inside of the fork legs, Callipers from a K1300GT, custom fabbed brackets to align it all, braided Goodridge stainless steel hoses, and a 20mm master cylinder from a K1100RS. The sticky Pirelli tyre helps, too. It's a two-fingered, controllable, rapid reduction in speed, albeit, with a bit too much dive as compared with a Telelever or Duolever front suspension.


Also, I've moved the post into the more appropriate section of Frame, Fairing & Wheels, from General Discussion.

I think we're talking about the same caliper here Darren; just that the mounts are in a different place. At least, those in your pic appear to be 'the other ones' that Guzzi use but BMW bribed paid Brembo large amounts of cash for marketing puposes

Not the same, Dai. The four piston Brembo cals I'm using are the later type, unlike from any K Brick calliper bar the very latest years of K1200LT, then R1150, early R1200 & K40 K bikes. Not the same as the closed top, four piston R1100 or K1100. Those cals use the FA407 pad while the type I show in the image use the FA363 pad (EBC number). Caution as there are both Brembo & Tokico lookalikes, but the Tokes use a slightly longer, thinner pad that'll have you scratching yer chin wondering what you need to file to git the bastages to fit!

Going back to the original posters specific question, the basic Brembo two piston & the early Brembo four piston do attach in the same bolt pattern spread of the fork legs, but the offset over the discs is wrong, not to mention the 2P use a 285mm diametre disc & 4P use 305mm. Some would argue that the 4P really can 'use' the extra volume of the K11 20mm master cylinder, with which I agree. Tho' later street-going Airheads got away with a 13mm or 16mm m/c over single or dual 4P Brembos.