'77 850 T3 Brake Disks

[n3303j]

After 100K miles my front rotors are looking a bit thin (especially the Right side).

Cast Iron rotors are about $160 each new.
Stainless Floating rotors are about $190 each new.

Any reason (except cost) I should choose one type over the other. Both are drop in replacements.

[pehayes]

Cast iron should work a lot better in the wet.  Of course, they will rust afterward but at least you'll be stopped.

Patrick Hayes
Fremont CA

[jhem68]

I have dual disks on the front of my 850T and converted to the EBC stainless floaters from MG Cycle a number of years ago. I needed another disk to add to the Eldo and used one of those salvaged off the T as a partial reason for the change. Primary advantage of the change to the EBC disk is what I consider to be a significant unsprung weight savings over the stock cast iron disk. Secondary advantage is the EBCs are much less inclined to rust at any exposure to moisture and I believe they are not quite as prone to warping.

I was soo pleased with the results that I repeated the change on my SP1000 three years later.



John

[Dave Swanson]

I thought my T3 discs were too thin also until I checked them with a micrometer.  They still had more than enough material to send them to TruEDisk.

[n3303j]

My disks were real close to minimum when I turned them 50K miles ago. They only got thinner.  Old machinist here. Miked them before and after turning. RF is used up.

[Turin]

I've been happy with the EBC rotors on my T.

[Stevex]

Got stainless discs with ceramic pads on my LM2 de linked front end...brilliant braking.

[jacksonracingcomau]

Another ebc floater vote
No delay in wet, no fade, lighter, no brainer, but they are thinner,, swap pads at halftime to get full mileage or replace them half worn. Pads will stick otherwise

[n3303j]

Another ebc floater vote
No delay in wet, no fade, lighter, no brainer, but they are thinner,, swap pads at halftime to get full mileage or replace them half worn. Pads will stick otherwise

"Pads will stick otherwise"
This doesn't sound good.
Please explain.

[Canuck750]

I have a pair of EBC floaters on my 1972 Eldorado, I sought out advice on what to fit from MG Cycle, this was about four years ago. I was leaning to the cast iron original type but Gord asked me if I wanted the brakes to look period correct but feel like wood or have a modern look and stop with one finger...… In comparison my 1975 Ducati 860 GT has a pair of Brembo dual bleeder calipers and cast iron Brembo discs, I out on about 100 miles today and it ain't no one finger stopper bike! It stops OK but the EBC floaters are much, much better.

[jacksonracingcomau]

"Pads will stick otherwise"
This doesn't sound good.
Please explain.

There was much discussion on here a year or three ago, search may find but I’ll try.

First, will stick should have been can stick, riding style and how hard you use brakes possibly very relevant.
In my case only noticed when I ran out of fuel 40 miles short of normal safe range, at top of mountain pass.
No problem, we’ll hit Pommy (Limey?) Overdrive and roll into town, except it wouldn’t, fuel consumption explained.
Because disc is thinner, when leading edge wears enough, there is enough room for pad to twist and (slightly ) drag on disc, only forcing piston back will get it free.
Since then I have taken to swapping pads over so leading becomes trailing and bedding them in again, last set I got the last mile out of !

Others have made shims to take up missing space or simply replaced pads early

Don’t have any worn out pads for pic but these showed wear,  have been swapped, bed in and run for a while, now look even again, at least a couple of big trips left in them,
Best of all, they never fade, makes old P8 calipers perfect I never want for more brakes.
So the only proviso is keep an eye on pad wear, as one always should anyway, getting last mile may or may not be important to you.



image uploader

[n3303j]

Job complete. I chose to go with cast iron rotors because I was happy with the performance of the original Brembo cast iron disks. (100K mile service life)

BUT.... The currently sold cast iron disks are not a proper replacement for the Brembo originals.

Brembo lists minimum acceptable wear limit for their disk is 5.8 mm. The current disks are 5.8mm thick when new.

The mounting flange on the reproduction disk is 2mm thicker than the original. That's 4mm total over two disks and the mounting bolts are too short to span this distance.

One of the pair I received had a hard spot in the swept area. As a result the disk chattered during machining the swept surface and is rather rough.

The offset is correct and the swept surfaces are parallel to each other and to the mounting flange. So the disks are usable, not great but serviceable.

As an aside the 6 lightening holes in the dish are crudely machined and all the edges are left SHARP enough to cut. The originals were all radiused.

[moto]

Job complete. I chose to go with cast iron rotors because I was happy with the performance of the original Brembo cast iron disks. (100K mile service life)

BUT.... The currently sold cast iron disks are not a proper replacement for the Brembo originals.

Brembo lists minimum acceptable wear limit for their disk is 5.8 mm. The current disks are 5.8mm thick when new.

The mounting flange on the reproduction disk is 2mm thicker than the original. That's 4mm total over two disks and the mounting bolts are too short to span this distance.

One of the pair I received had a hard spot in the swept area. As a result the disk chattered during machining the swept surface and is rather rough.

The offset is correct and the swept surfaces are parallel to each other and to the mounting flange. So the disks are usable, not great but serviceable.

As an aside the 6 lightening holes in the dish are crudely machined and all the edges are left SHARP enough to cut. The originals were all radiused.

That's disappointing but not too surprising. The Brembos have their minimum thickness specification engraved on the edge of the disk (as I recall). Do the new ones also have a value there? It will determine how many times brake shops will be willing to machine them later on.

Thanks for the detailed report.

Moto

[n3303j]

No minimum thickness figure marked on the reproduction disks. Where they are a similar material to the original product I'm figuring that they get thrown away once the surface becomes worn enough that a remachining would be required. They are already at minimum Brembo specs for cast iron.

[n3303j]

Probably last pass on this post by me. Installed the cast iron copies. Bought the longer bolts to fit them. Rode them 50 miles and hated the pulsing over the hard spots. Not extreme but noticeable. I don't want new brakes to be anything but smooth.

Bought the EBC floaters. They are beautifully made. The longer bolts I bought for the iron copy disks just fit the EBC product. I had to clean up the LH slider just a bit to clear the floating buttons on the LH disk. That was all of 10 minutes with a 4 inch disk sander. I also adjusted the shims on the caliper to put the disk in the center of the caliper opening.

I can see where a worn brake pad and an off center caliper would bind up. When the brake is applied the pad and steel backing are driven forward against a machined face in the caliper. If the caliper was off center the space between the caliper stop face and the disk face could be wider than the steel backing plate on the pad. This would allow the worn pad to move forward enough to get in between the caliper body and the disk. It isn't the puck coming out unevenly, its the pad remains fitting between the disk and the caliper body.

Shims between the puck and the pad won't remedy this. Remachining the face of the split caliper to close the width of the disk slot to match the narrower stainless disks will make all work properly. Guess that project is on the list before the pads wear too much.

[jacksonracingcomau]

Bought the EBC floaters. They are beautifully made. The longer bolts I bought for the iron copy disks just fit the EBC product. I had to clean up the LH slider just a bit to clear the floating buttons on the LH disk. That was all of 10 minutes with a 4 inch disk sander. I also adjusted the shims on the caliper to put the disk in the center of the caliper opening.

You’ll be happy with brakes
BUT discs should be same distance from each fork leg assuming wheel is central and std disc mounts, something is not right if your left disc hit leg.All I’ve seen clear with ease.
Chech wheel for central, you may have to reshim calipers.

[Stevex]

I've got these SS fitted my LM2.
With the ceramic pads they're the dogs.

[n3303j]

You’ll be happy with brakes
BUT discs should be same distance from each fork leg assuming wheel is central and std disc mounts, something is not right if your left disc hit leg.All I’ve seen clear with ease.
Chech wheel for central, you may have to reshim calipers.

Slider castings are not completely symmetrical. Disks are really close to central in relationship to caliper mount machined surface.

It all works now.

[ATKautz]

Good Day,
I put the EBC floaters on my 1984 SP. They are great! I got them from MG Cycle.
I put new pads in all the way around. This is important and recommended from what I understand..
I needed longer bolts 120mm. Got them and nuts from McMaster Carr.
I did not need to grind my fork tubes. MG says in some cases that my be needed. Clearance is close though, a few mm. See image.