Single finger front braking on R65?

[Mucci]

I have an ‘83 R65. The braking has always been terrible on it. It’s a single disc Brembo. I installed Spiegler SS line, semi-sintered pads and lightly surfaced the rotor but all that did was increase the density of the wood block that’s hidden somewhere in the caliper. Hard braking is still a 2-3 finger aggressive pull.

The forks and wheel have provisions for a RH caliper. I also found out it’s got a 15mm MC on it for some reason. On top of all this the rotor recently warped (probably because I surfaced it).

So my question is, is it with the money to go OEM dual disc if I need to buy two rotors, a caliper, pads and new lines? Would this yield single finger braking like on a modern bike?

Or should I just take that money and put it into a more modern single caliper and floating rotor upgrade? Are there any bolt on options? I have a lathe if I need it.

[Bob_Roller]

The brakes on the R65 leave a lot to be desired !!!
First, the 15 mm master cylinder is wrong for a single disc set up .
Should be 12 mm diameter for a single disc, that's what the bikes came with from the factory .
I don't know how much of an improvement a second disc would be, all my R65's have twin disc .
I've got EBC semi floating steel rotors on my '81 R65 . Luftmeister braided stainless lines ( installed them in 10/91) Luftmeister has long since gone out of business .
Currently have EBC graphite pads .
I saw no noticeable improvement in braking with the EBC pads in dry conditions, but very much improved wet braking .
The new lines improved braking, but not by much, I couldn't lock the front wheel with the 21 year old OEM rubber lines , no problem after the new line installation .
Speigler has a upgrade on OEM rotors, they will install semi floating stainless steel rotor on the old hub .

https://spieglerusa.com/brakes/brake-rotors/bmw-conversion-old-models.html

I've got a set on my red '82 LS along with Speigler stainless lines and EBC FA18 graphite pads .
Improved braking on the R65 would make me more comfortable riding it, after I got the oilhead in '02, the R65 bakes felt unsafe .
Nothing has turned the bike into a single finger stopping, still need a handful of fingers !!!
My '87 Guzzi has great brakes for a 33 year old bike, vastly better the the R65's .

[Mucci]

Thanks for the feedback Bob. If the dual disc setup with all those new and upgraded parts still feel “unsafe” compared to a modern bike then I think I have my answer.

Think I’ll spend that money on a modern caliper and machine a bracket for it. I wonder if Spiegler could retrofit a larger diameter floating rotor to the stock rotor hub.

[nhmaf]

The 13mm DIA m/c - if you can find one - prvovides much more feedback and travel/linear response with a single caliper.  The 15mm really needs to be with a dual disc setup.  My 1982 R65LS has a 15mm and dual Brembos - it doesn't move far and feels like it is wooden, but brakes decently, for a 1982 motorcycle.

IF you are using the factory stainless rotors, you must use the organic pads with them and not sintered metal pads - those do groove the rotor and cause warping.  I am running the factory stainless rotors and the EBC organics (I think the product code is FA18 ?) and the work pretty well, but the braking still isn't as good as it is on my 1998 KAwasaki, much less a 2020 motorcycle.

[mrclubike]

Like everyone has already said
The 15mm MC is your biggest problem
What ever you do
Look at the making  sure you improve your leverage
I run a 38mm Brembo F08 single caliper and a 12mm MC and find the braking very adequate  even compared to my 2004 R1150R (NON ABS)
I just wish the lever was a little closer to the grip on the R65

[Barry]

The 78 - 80 single disk bikes with Ate calipers had  a 13 mm master cylinder and from 81 with a Brembo caliper they had a 12mm which would be my choice if you could find one. A 12mm would give you a 56% improvement in leverage over a 15mm.

[Matt Chapter]

I did the spiegler rotor upgrade on my '86, single rotor.  I think the braking is good enough (and improved over stock), but I also suspect my spiegler rotor is slightly warped.  I also did stainless brake lines, don't think they made a big difference but would definitely recommend to eliminate the lines as a problem source.

I agree with others that a new master cylinder is probably more cost effective than a pair of new rotors and calipers and so on.

[Mucci]

After doing some price research I saw I can get a R/K1100 4-pot caliper on ebay for around $35 shipped...so I don't know why I wouldn't just do that. Apparently they bolt up with some light machining.
https://advrider.com/f/threads/four-pot-brembo-conversion-for-r100gs-and-r100-monolever-why-not-4-pot-brembo-s.625343/page-2

So my question is, with the 4-pot caliper would my 15mm master be best, or do I still want to go down to a 12/13mm?

Also, FYI Spiegler no longer does the rotor replacement. I just got this from them:

"Dave,
We actually can no longer get the discs we used for these. This part/service has been discontinued unfortunately."

It looks like I can get the replacement rotor that Braking makes and just replace it myself. They're $99 shipped on ebay. (PN: BW01FI)

[Mucci]

More research to the rescue!

I found this master cylinder ratio calculator:
http://www.vintagebrake.com/mastercylinder.htm

My current ratio = 11.5:1 (block of wood)
(2x36mm piston & 15mm m/c)

Stock R65 (single) =
18:1 w/ 12mm M/C
15.4:1 w/ 13mm M/C ("harder feel")

The 4-pot R1100 caliper has 2x32mm pistons and 2x34mm.
 
Piston area = 3,422mm^2 / 176.7mm^2 (15mm m/c) = 19.3:1

I looked up the R/K1100 m/c and it's 20mm with dual discs. So stock R/K1100 has a 21.8:1 ratio.

I'm a little confused about what the optimal ratio is. In the link above the author says that for opposing piston calipers a ratio of 23:1-27:1 is ideal. If that's the case how does the stock R1100 brake not feel like a block of wood?

He touches a bit on the ratio of disc diameter : wheel size having an effect but doesn't really elaborate in a way that's calculable.

According to the ratios above swapping to the R1100 caliper and keeping my 15mm m/c would yield a ratio very close to, but a bit softer than the stock R65.

[Barry]

You need to count the area of pistons on both sides of the caliper.  I get a stock 12mm / 36mm ratio to be  1:18

It looks to me that you did count both sides on the 4 pot so the ratio is  not that different.

[Mucci]

You need to count the area of pistons on both sides of the caliper.  I get a stock 12mm / 36mm ratio to be  1:18

It looks to me that you did count both sides on the 4 pot so the ratio is  not that different.

Edit: Oops. I had to just go out and look at my caliper. I was thinking it was a single piston. I'll edit the above calculations.

[Luca]

I have a 12mm M/C on my dual disc LS and it brakes quite well.  The lever is a little mushy, but I'm still on rubber hoses and the upper hose is ancient; I suspect SS lines will fix that.

As it stands if I grab a fistful of brakes I can make the front tire start chirping

[Kelvin]

You might also consider changing the brake lever. I did this once and was surprised at the difference in feel and leverage that I got from the new lever compared to the 30 year old one.