Using Floating rotors with Brembo F08 calipers (Eldorado, 850T, T3, others)

[jas67]

I've purchased and installed a pair of these:
http://www.mgcycle.com/index.php?main_page=advanced_search_result&search_in_descripti on=1&keyword=MGEBC300



with F08 calipers on my '74 Eldorado.     This also applies to T, T3, and any other Guzzis using the F08 caliper.

Then, I come across this warning:

From: http://www.thisoldtractor.com/moto_guzzi_loopframe_disc_brake_floating_rotors.html

CAUTION: Do not put floaters on a bike with early calipers like FO8s, unless you are qualified to make serious modifications to the calipers. The pistons on FO8s cannot extend far enough out of the body of the caliper to come in contact with a 5 mm rotor and then safely retract once you have even a little wear on your brake pads. After very little use, they will extend, contact your rotor, not retract and lock your brakes.

Can someone please educate me on why this is a problem, and what I should do to prevent this serious sounding problem from happening.

[EldoMike]

I can't help but hope someone can!

[Markcarovilli]

Sounds like floating rotors are thinner and the F08s extend out too much with only a little pad wear and then get hung because they can’t retract. 

Mark

[Zoom Zoom]

Something I'm thinking: Charlie and Greg, (along with Mike Tiberio), really know their stuff when it comes to loop frames, so it sure does merit consideration.

What is the thickness of the cast iron rotors, then the new rotors? Is the off set the same. New ones thinner? Slightly different off set?

These are the only two things that I can think of that might allow the puck to extend too far out of the caliper to not retract properly. Perhaps, and I say PERHAPS, this has been addressed with the replacement rotors, IDK.

John Henry

[EldoMike]

Isn't this something the Boys at MGCycle should be aware of...or made aware of?

[Antietam Classic Cycle]

The original rotors are ~ 6.5 mm thick when new with a wear limit of 5.8 mm.

Jay: how thick are your EBC rotors? I've installed a few of those rotors sourced from MG Cycle and don't remember them being only 5 mm thick, more like close to original thickness. Perhaps the rotors that Mike and Charley are referring to "listed as being for a Laverda SFC 1000" are actually thinner than the ones being sold by MG Cycle?

With rotors only 5 mm thick, I can see pistons not retracting as being an issue once the pads have worn past about half. But, Charley's assumption that: "After very little use, they will extend, contact your rotor, not retract and lock your brakes" seems a bit much. He makes it sound like the pistons will contact the rotor and lock the brakes, which is not possible since the piston is completely covered/separated from the rotors by the metal backing plate of the brake pad.

[jas67]

The original rotors are ~ 6.5 mm thick when new with a wear limit of 5.8 mm.

Jay: how thick are your EBC rotors? I've installed a few of those rotors sourced from MG Cycle and don't remember them being only 5 mm thick, more like close to original thickness. Perhaps the rotors that Mike and Charley are referring to " listed as being for a Laverda SFC 1000" are actually thinner than the ones being sold by MG Cycle?

With rotors only 5 mm thick, I can see pistons not retracting as being an issue once the pads have worn past about half. But, Charley's assumption that: "After very little use, they will extend, contact your rotor, not retract and lock your brakes" seems a bit much. He makes it sound like the pistons will contact the rotor and lock the brakes, which is not possible since the piston is completely covered/separated from the rotors by the metal backing plate of the brake pad.

I'll measure the rotor thickness tonight when I'm back home.

[canuck750]

I have a pair of the MG Cycle sourced rotors and new F08 Brembo calipers (all from MG Cycle) on my 72 Eldorado, been riding it like this for four years and the brakes are great. I never heard anything from Rick or Gordon at MG Cycle about non-compatibility with the F08 calipers and they are usually very up to date and have first hand experience with what they sell. I was originally going to go with the stock type Brembo rotors but the guys at MG told me that when they swapped to the EBC rotors from the stock ones the brake performance was much improved.

I will measure up the various rotor thicknesses I have on bikes with the F08 caliper, my Le Mans, 750S, and Laverda SF1 each have different style of rotors and use F08 calipers, this is an interesting topic.

[Don G]

Not only a problem on a Disc brake loop then,  wasn't the T series quite similar in construction? So anything with an F08 would be suspect then?  DonG

[F-22]

Then a solution would be to make simple spacers on a lathe. The original caliper pistons are hollow with the hole directed to the pads, so it would be easy to make an  aluminium spacer that stays between the pad and extends into the piston (perhaps with a slight interference fit, but even if not it could not fall out on its own when installed).

[jas67]

Not only a problem on a Disc brake loop then,  wasn't the T series quite similar in construction? So anything with an F08 would be suspect then?  DonG

I updated the title of the thread to reflect that this applies to other models as well.

[Antietam Classic Cycle]

Then a solution would be to make simple spacers on a lathe. The original caliper pistons are hollow with the hole directed to the pads, so it would be easy to make an  aluminium spacer that stays between the pad and extends into the piston (perhaps with a slight interference fit, but even if not it could not fall out on its own when installed).

  Good idea.

[Lannis]

Then a solution would be to make simple spacers on a lathe. The original caliper pistons are hollow with the hole directed to the pads, so it would be easy to make an  aluminium spacer that stays between the pad and extends into the piston (perhaps with a slight interference fit, but even if not it could not fall out on its own when installed).

This is probably what the warning meant when it said:

".... unless you are qualified to make serious modifications to the calipers."

Anything involving a lathe is a serious modification in my book!

Lannis

[canuck750]

I called MG Cycle and had a good long discussion, the topic has been around for as long as EBC rotors have been offered.

A note from MG Cycle, Brembe makes an identical thickness stainless steel rotor for the F08 caliper and the replacement full floater rotor for the LeMans 1000 with F08 calipers is also the same thickness as the EBC rotor. on top of that ENC recommends their full floater rotor as direct replacement to the stick cast rotor.


Lets just say that I won't be changing out my F08 / EBC setup.

[Antietam Classic Cycle]

This is probably what the warning meant when it said:

".... unless you are qualified to make serious modifications to the calipers."

Anything involving a lathe is a serious modification in my book!

Lannis

What F-22 is suggesting is to make an alloy piece, looking sort of like a "top hat" that would insert into the F08 pistons. The "brim" of the "top hat" would be of a thickness to make up the difference between the thickness of the stock rotor and aftermarket ones. No machining of the caliper or it's pistons.

Even easier would be to just make two sheet metal shims (one behind each pad) of the necessary thickness (difference between rotor thicknesses), shaped the same as the pads and retained by the caliper's pins.

[EldoMike]

This has been a great discussion...I love this forum

[jas67]

I measured the EBC's, 5.15mm.   The old, and, surely worn cast iron rotor also measures to 5.15mm.
I can't find a minimum thickness printed on either one.  Anyone have that info?

I called MG Cycle and had a good long discussion, the topic has been around for as long as EBC rotors have been offered.

A note from MG Cycle, Brembe makes an identical thickness stainless steel rotor for the F08 caliper and the replacement full floater rotor for the LeMans 1000 with F08 calipers is also the same thickness as the EBC rotor. on top of that ENC recommends their full floater rotor as direct replacement to the stick cast rotor.


Lets just say that I won't be changing out my F08 / EBC setup.

Thanks for clearing it up.  I'll ride in confidence.

[Antietam Classic Cycle]

I measured the EBC's, 5.15mm.   The old, and, surely worn cast iron rotor also measures to 5.15mm.
I can't find a minimum thickness printed on either one.  Anyone have that info?

Thanks for clearing it up.  I'll ride in confidence.

The minimum thickness spec. for the original rotors is 5.8 mm. If one was worried about the difference (6.5 mm vs 5.15 mm), a pair of metal shims .026" thick, matching the shape of the brake pads, could be fitted. This would effectively position the pistons the same as they would be with the original 6.5 mm thick disc. 

[guzziownr]

I run a single disk on my Eldo with an F09 caliper. While commuting daily in NYC I took a set of pads down so thin that one pad looked like it had a coat of paint rather than pad material, yet I live on...

I make it a point to inspect the pads more frequently now-a-days.

[kirby1923]

Don't "floating rotors" tend to "float", changing the positions/distance in the caliper grove?

Might that cause problems with piston movement distances as opposed to fixed discs, and 08 calipers designed for fixed discs?
Wouldn't think it would lock things up but might cause problems some combinations.

Maybe I'm missing something here but it doesn't seem un reasonable that could cause problems w/some calipers/disc set ups that were designed for fixed discs.

[Tusayan]

Non-floating disks can more readily be set up so they arent centered in the caliper, floating disks dont have a tremendous amount of lateral play but do tend to become centered between opposing pistons if the caliper is in good, serviceable condition.

[jacksonracingcomau]

I’ve been using these discs with 08 calipers for a few sets of pads
No problem whatsoever with pucks, best brakes it’s ever had, tried every brand pads with cast iron discs
But pads now wear at angle not flat, now I swap em round at half time, get the extra mile ,
First set I didn’t, pads started to stick, twisted in caliper, really worn at angle, leading edge nearly gone.

Recommend to anyone who wants brakes, never ever fade

[mtiberio]

I love Charlie Cole, but he is a bit of a fanatic. I never ran these rotors with F08's, but I did run the original Brembo Goldline floating rotors back in the day, no issues. I do replace my pads early on all my bikes (unless I snooze). I do this because I don't like the pistons to stick out too far and corrode. Pads are cheap.

I have had more issues with the buttons on floating rotors hitting F09 calipers, and the buttons on floating rotors smacking the fork sliders. If you look at the sliders from the various 35mm forks, you will notice there is an area scooped out (flattened) to make room for the rotors. On some models this area extends down toward the axle more than others (lemans vs touring models). On the models that do not extend down I once had to dremel some slider off so it didn't hit the floating buttons.

As usual, YMMV. If you are going to blaze a trail, be prepared...

just dawned on me my comment about F09's and floaters might be wrong or misleading. If there was an issue, it was with F09's and the old brembo rotors (floating or composite)... Since  it was over 25 years ago it might have been not the floating buttons, but the composite (iron/aluminum) fixed early convert rotors where the tiny bolt fouled the F09 rubber dust seal. Since I really cant remember, I don't want anyone with F09's freaking out. If you use one with floaters or composite rotors, you might just want to check...

[kirby1923]

CX,
Centered my fixed discs in the caliper w/shims (P08 and they don't change).

The floaters I have can and do get off set sometimes by a tiny bit,(1/16" .00246mm), and I usually re center and clean the buttons so I get even ware of the pads.

[jacksonracingcomau]

Irony
Since posting in this thread, brakes started dragging today
Swapping half time not enough to save till end of pad life
Pads worn cock eyed and twisting in caliper enough to drag
Not dangerously on bitumen but enough to make it very hard to push
Guess this is what led to warning post, misdiagnosed as puck sticking
Possibly why 4 pots were first used too, to get even wear on pad with differential pistons
Am about 1mm off wear line so cbf swapping sides again but will maybe do it twice next set
Unlike with cast rotors brakes are as good at end of life as at beginning— til they stick
Hope that solves it for others, if they stick, look at pads not pistons, don’t think spacer could help.
Pistons nowhere near fully out, as Charlie said, miles to go before that

[guzziownr]

I don't want anyone with F09's freaking out. If you use one with floaters or composite rotors, you might just want to check...

I was just in that area last week trying to get a cheap Chinese Cycle computer to work (it didn't).  While I was fiddling with the magnet I discovered just how little clearance there is between the button and the F09.

Fortunately, a miss is as good as a mile!

[Tusayan]

CX,
Centered my fixed discs in the caliper w/shims (P08 and they don't change).

The floaters I have can and do get off set sometimes by a tiny bit,(1/16" .00246mm), and I usually re center and clean the buttons so I get even ware of the pads.

The idea with floaters is that they float, mostly radially to accommodate thermal expansion, but also sideways.  That means all else being in good condition that the disks can self center between that pads, unlike with fixed mount disks. Floating disks are better than fixed disks when it comes to centering between opposing pistons, because they tend to do it automatically.

Re pad wear: neither of the brake pads can exert pressure on the disk (or wear) until they are both in contact with the disk, because until then there is no hydraulic pressure built up in the caliper.  Regardless of fixed or floating disks or whether the disk is centered between the pistons, the pads will wear the same. On each pad you will typically see a little more wear on the OD than the ID, and considerably more on the trailing versus leading edge.  The former results from the difference in speed of the disk at OD versus ID, the latter from the trailing edge of the pad running hotter.  This helps explain why more modern calipers may have four pistons, two bigger than the other two, and not so much radial depth.

[kirby1923]

Actually the pads can and do wear differently sometimes and the floaters can and do cease to float due to road crud or unknown/undetermined reasons.

[Tusayan]

Actually the pads can and do wear differently sometimes and the floaters can and do cease to float due to road crud etc.

If one pad is wearing more than the other, it is likely due to one piston being sticky relative to the other.

The condition of the buttons is irrelevant to pad wear.