Boxerworks.com

Major Softie wrote:

melville wrote:Well, my 12/74 (1975 model year) /6 has drilled disc and 38mm. Caliper unmarked when I got it as to size, even less marked now.

Is your unmarked caliper markedly less marked now?

It's remarkable how markedly less marked it is now:



If I were twelve inches tall I could use it as a shaving mirror.

Major Softie wrote:

melville wrote:Well, my 12/74 (1975 model year) /6 has drilled disc and 38mm. Caliper unmarked when I got it as to size, even less marked now.

Is your unmarked caliper markedly less marked now?

And would that make it completely unremarkable?

"1975 R90 Brake Caliper Size"

All early 2-pot BMW issued Brembo calipers are the very same F08 casting.
Only the bore and the piston will vary – and then by only @ 2mm.
A 2mm difference in piston will not result in any significant increased stopping capability ...

If better stopping is what you are after, consider:

1) A change of mc to get a more realistic mc / piston area ratio
( BMW was way conservative in their stock choices )
***This will be the "biggest bang for your buck" ***

2) Next will be quality brake pads.

3) And then, a change of rotor material to what works best as opposed to what does not rust ...
and that will be a ductile-iron – NOT Stainless.

Max Headroom wrote:And would that make it completely unremarkable?

melville wrote:It's remarkable how markedly less marked it is now:

Why, mark my words, I would pay many marks for such beautiful work. I doubt the Bismark had markedly better technology. There's a casting on my friend Mark's Numark turntable somewhat similar, but the markings on it do not represent the market's tastes, and thus are not nearly as marketable.

vanzen@rockerboxer.com wrote:All early 2-pot BMW issued Brembo calipers are the very same F08 casting.
Only the bore and the piston will vary – and then by only @ 2mm.
A 2mm difference in piston will not result in any significant increased stopping capability ...

I am confused by the referance to 2-pot Brembo - I have a swinging ATE. Maybe I am just confused again. You don't think I will get the 8% improvement?

vanzen@rockerboxer.com wrote: If better stopping is what you are after, consider:

1) A change of mc to get a more realistic mc / piston area ratio
( BMW was way conservative in their stock choices )
***This will be the "biggest bang for your buck" ***

2) Next will be quality brake pads.

3) And then, a change of rotor material to what works best as opposed to what does not rust ...
and that will be a ductile-iron – NOT Stainless.

MC was changed to 13mm handlebar mounted. Pads are new. At one point I let Matt talk me into some superduper pads that didn't work worth a shit, so I went back to the first new ones. I have not changed the disk, but the PO said the one I have (drilled Stainless) is not original. Where does one buy a ductile-iron disk.

If you change to ductile Iron rotors, be sure to also change to organic pads. Metallic pads will make short work of iron disks.

Major Softie wrote:

Max Headroom wrote:And would that make it completely unremarkable?

melville wrote:It's remarkable how markedly less marked it is now:

Why, mark my words, I would pay many marks for such beautiful work. I doubt the Bismark had markedly better technology. There's a casting on my friend Mark's Numark turntable somewhat similar, but the markings on it do not represent the market's tastes, and thus are not nearly as marketable.

MS, that remark marks you out as a marked man . . . .

a 40mm caliper piston may have more surface area than the 38mm and therefore more force for a given fluid line pressure, but similar to a smaller master cylinder bore (like using a single disk MC on a dual disk bike), creates longer brake lever travel with a softer feel, as more fluid is required to move any distance.

I run single disk MC on both the '75 R90S w/ 38mm calipers and my '77 R100RS with 40mm calipers. Can't say I notice enough of a difference. Not sure about what brand pads in in the RS, but I think the R90S is using EBC.