Replacing the rotor disc & upgrading to 4 piston.

[Mucci]

I’m in the midst of upgrading the braking on my ‘83 R65 and thought I would share my experiences as I go.

First up is replacing the warped rotor. As anyone who’s called the dealer likely found out the OEM replacements only exist in the country in single digits and they’re something to the tune of $300+.  Speigler used to offer a service where they replace just the disc on your existing OEM rotor hub. According to them they no longer can get the discs and have discontinued this service.

You can however get the disc from Braking. I got one on eBay for $99 shipped. Here’s how to install it:

PN: BW01FI

Here’s what you get.



Laid over stock rotor.



Use a punch to mark the center of the rivets.



Cover the hub hole to avoid shavings getting in there. I used a rubber stopper.

Use a drill bit about the same size as the rivet to take most of the meat off. Stop before you get into the rotor to avoid going too far and eating into the hub. (Left)

Use a grinder to take off the rest. (Right)



Use a punch to knock out the rivet (right).



Pull the rotor off and clean the rotor hub of all shaving and debris.



Clean the new rotor with brake clean.

The kit comes with two length bolts. Use the longer ones. Install the hardware in this order: Bolt, countersink spacer, wavy washer, rotor, washer, nut.

FYI the bolt and nut are pretty low grade and I had one pair bind on me that I then had to chase with a tap and die. I would have swapped them out for stainless if I had them in stock. Snug them up by hand with a ratchet to avoid them cross threading.

The Braking directions say to use OEM torque specs but of course our bikes don’t list this. I went with 10 ftlbs because that’s what my KTM rotor calls for.

Here it is all buttoned up:



Next I’ll be tackling making a 4-piston Brembo caliper from the R/K1100 work on the bike.

I got some EBC organic pads (FA246) for $20 shipped and the caliper for $30 shipped, both on eBay. Just waiting for the parts to come in.

[mrclubike]

I wish I would have known about this when I replaced mine 

[mrclubike]

Motobins is out of stock on both

[georgesgiralt]

Hummmm...
The BMW Classic Shop list them as available today at a whooping 306 € a pièce ...
So if you want to go the OEM route, you can... 

[Bob_Roller]

Is the replacement rotor stainless steel ?

[Mucci]

Is the replacement rotor stainless steel ?

Yes, Stainless.

[Mucci]

I made some very interesting discoveries this weekend in my quest for upgrading the stock caliper.

Others have used the 4-piston Brembo caliper on bigger airheads saying that the mounting holes are identical; caveat being that the caliper bosses need a little machining to work.

So I thought I'd pick one up and see if the same is true for the R65. In summary, I was able to make it work without machining the mounts, and for only $50 (caliper and new pads).

Here's the process:
https://advrider.com/f/threads/the-50-4-piston-brembo-brake-upgrade.1444863/

[Bob_Roller]

Great write-up !!!
This is the one area of the R65 that really needs improvement .
Something I'm going to look into once the temps here go down in October .
Be looking forward to your experience with this modification .

[Mucci]

Great write-up !!!
This is the one area of the R65 that really needs improvement .
Something I'm going to look into once the temps here go down in October .
Be looking forward to your experience with this modification .

I've only had 2 hours on it so far but it's so much better. The 15mm master is spot on in my opinion.

It's not modern sport bike level of single finger stopping power but I'd finally put the bike in the "good brakes" category. I could always add a 2nd to the other side but that gets more complicated. Plus it's damn good as is.

[Matt Chapter]

This is great info on the rotor replacement.  I'd already had the spiegler mod, and was wondering what to do next time the rotor wore out.  I can probably have it machined next time I do the brakes, but this looks like a very simple replacement.

[Mucci]

This is great info on the rotor replacement.  I'd already had the spiegler mod, and was wondering what to do next time the rotor wore out.  I can probably have it machined next time I do the brakes, but this looks like a very simple replacement.

I wouldn’t waste your money machining it. I tried that and even though it was still at the min. thickness limit it warped within a day.

[georgesgiralt]

In my youth, I studied mechanical engineering.
Rectifying a thin piece of steel is a difficult job. You have to take a very thin pass on one side, preventing the piece to heat (plenty of lubrication), let it cool then turn it on the other side and do the same on the other side. Repeat the whole sequence until you reach either the proper dimension or have removed the problem. And it is not warranted to work well ....
I wonder if, given the price of workmanship these days, anyone take the burden to do it properly. Hence, the part ends warped or worse.... This is why nobody sharpen the blades on wood working planing machine but replace them. The cost for new blades is less than an our shop labor....

[Mucci]

I can tell you BMW does no such thing. I brought it into them and they said they told me “you don’t resurface motorcycle rotors. You replace them.”

You know, for $350 ea. and that’s not including labor 

[Matt Chapter]

I wouldn’t waste your money machining it. I tried that and even though it was still at the min. thickness limit it warped within a day.

The stock rotor or the spiegler replacement?

At $100 for a new rotor, I agree it's probably easier to just replace it.

In a few thousand miles I'm going to do the brakes on my '17 Tacoma, I've already decided I'm not going to mess with the rotor, and I'll just replace it when I do the pads a second time.

[Mucci]

You can machine disc on a car/truck. They’re vented and way beefier. Shops do it all the time.