Author Topic: Stainless Material specifics for brake discs. (Read 4016 times)

gschuld · « **on:** October 14, 2019, 09:48:03 PM »

Does anyone know what specific grade of stainless is used for disc brake rotors. Vintage or just as useful, modern stainless rotors?

Going further, anyone offhand know where I could source the plate material?

420-430 high carbon Stainless steel sound right?

Thanks,

George

754 · « **Reply #1 on:** October 14, 2019, 11:42:56 PM »

Look at the literature for EBC and others, they ofte list the alloy used.

70CB750 · « **Reply #2 on:** October 15, 2019, 03:29:23 AM »

Following. This interest me. The problem is the steel will come from a metal sheet and it will behave differently across vs along the roll direction.

turboguzzi · « **Reply #3 on:** October 15, 2019, 08:46:27 AM »

George, maybe tell us why you ask.... trying to cut your own discs? Hope not.... unless you want to start a little R&D project on disc materials...

gschuld · « **Reply #4 on:** October 15, 2019, 04:21:26 PM »

Yossef,

As you suspect, I was considering options regarding new rotors. AHRMA allows up to 12” (305mm) diameter. I also noticed RPE in Australia seems to be out of business. I was hoping they still had some cast iron rotors.

Just looking at options. The physical cutting of the rotors out of a plate material is not so much the issue, but the proper heat treatment etc involved after machining is where I get well out of my depth.

George

bear · « **Reply #5 on:** October 15, 2019, 11:01:16 PM »

Not sure about your rules George, but we machined ours from cast round stock.
Then mounted them on a later model floating carrier.
We gave up using stainless.

Cheers,
Brian

turboguzzi · « **Reply #6 on:** October 16, 2019, 01:08:36 AM »

cast iron is always a good option but honestly, with all the modern day pad compounds that have been developed for SS not easy to justify. Maybe on Bear's sidecar where you need a lot of heat sink capacity you might want specially thick iron customs discs, but not sure on a solo bike

look at all modern classes, WSBK, SSP, Moto2, they all do stoppies all day long with SS discs. Even in our classic paddock i see iron discs only on period bikes restored for demo laps, not the real racers.

I have managed to apply modern compounds to my SS discs by modifying current brake pads. Seems a much safer option to me than DIY and develop discs only to find them wrapping at the end of a straight.

bear · « **Reply #7 on:** October 16, 2019, 03:48:07 AM »

Your right TG, solo's and sidecar's are like chalk and cheese.

In our case we could not control major brake fade issues due as you mentioned to overheating.

Using the heaver cast units was the solution for our application.

Having said that most of the unlimited solo P4's seem to run them. Or at least they did last time I looked.

slikwilli420 · « **Reply #8 on:** October 16, 2019, 06:24:28 AM »

My issue is that I can only have one disc so it needs to be the best it can be. The original SS used by Honda is easily glazed and not very good, especially if I only have one. A replica of that disc in cast iron offers excellent braking and being thick like the originals, not prone to warping. A few of the other guys in my class are running more modern rotors that are thinner, but designed to be run as a pair, and they warp them regularly. A quality SS option in a thicker material closer to stock would be the best of both worlds.

gschuld · « **Reply #9 on:** October 16, 2019, 09:36:10 AM »

My ideal would be a full 12” diameter rotor with modern stainless material.

George

slikwilli420 · « **Reply #10 on:** October 16, 2019, 10:26:13 AM »

Quote from: gschuld on October 16, 2019, 09:36:10 AM

My ideal would be a full 12” diameter rotor with modern stainless material.

George

Agreed 100%

bwaller · « **Reply #11 on:** October 16, 2019, 10:36:13 AM »

I agree with TG, rarely see cast rotors on any solo's here too. Original H rotors do glaze but I address that a couple times a season with a flex hone in a lathe with a slow drill. Works a treat, and finding good pads is easy enough. http://www.brushresearch.com/brushes.php?c1=6

We've used these thin discs for years without warping them Matt. Not saying it doesn't happen, but remember brakes just slow you down.

It sounds like a tremendous effort, sorry George.....

gschuld · « **Reply #12 on:** October 16, 2019, 12:06:02 PM »

Brent,

Nothing for you to be sorry about. Good info. I’ve heard of several methods to deglaze the factory Honda rotors during the season. It’s kind of frustrating to need to pull the front wheel and remove the rotors to manually deglaze them several times per race season.

FWIW, it’s pretty common practice to use cast iron rotors on big bore Post Classic Unlimited class cb750s down in Australia, has been for years. They run methanol burning engines from 970cc to over 1300cc

These are most likely the most powerful class of CB750 based vintage road race bikes anywhere, and fast rotors appear to be the most common there. But, to be fair, the top performer has been Dean Oughtred’s ride, a rather faithful 970 kit bike style CR750 with factory rotors AND calipers, along with a 970 kit twin leading shoe rear wheel. Go figure....

George

slikwilli420 · « **Reply #13 on:** October 16, 2019, 12:40:22 PM »

Quote from: bwaller on October 16, 2019, 10:36:13 AM

I agree with TG, rarely see cast rotors on any solo's here too. Original H rotors do glaze but I address that a couple times a season with a flex hone in a lathe with a slow drill. Works a treat, and finding good pads is easy enough. http://www.brushresearch.com/brushes.php?c1=6

We've used these thin discs for years without warping them Matt. Not saying it doesn't happen, but remember brakes just slow you down.

It sounds like a tremendous effort, sorry George.....

Im OK with the thin discs as well, but when there are 2. I can only have one disc in my class so it makes sense that it has the most stopping power that can be packed into a rules-compliant setup. If I could have twin discs, I would run a more modern rotor and not worry at all about using the crappy old Honda rotors. If the rotors are glazing that often over the season, to me it proves it was the wrong material for the task. I would love a replica of our rotors in a proper, modern SS alloy, then I wouldn't be dealing with rusty brakes all the time.

RAFster122s · « **Reply #14 on:** October 16, 2019, 12:41:43 PM »

Quote from: bwaller on October 16, 2019, 10:36:13 AM

I agree with TG, rarely see cast rotors on any solo's here too. Original H rotors do glaze but I address that a couple times a season with a flex hone in a lathe with a slow drill. Works a treat, and finding good pads is easy enough. http://www.brushresearch.com/brushes.php?c1=6

We've used these thin discs for years without warping them Matt. Not saying it doesn't happen, but remember brakes just slow you down.

It sounds like a tremendous effort, sorry George.....

Brent, can the flex hone be used without a lathe? I don’t have access to a lathe, drill sure...
Thanks! David

slikwilli420 · « **Reply #15 on:** October 16, 2019, 01:20:24 PM »

Quote from: RAF122S on October 16, 2019, 12:41:43 PM

Quote from: bwaller on October 16, 2019, 10:36:13 AM
I agree with TG, rarely see cast rotors on any solo's here too. Original H rotors do glaze but I address that a couple times a season with a flex hone in a lathe with a slow drill. Works a treat, and finding good pads is easy enough. http://www.brushresearch.com/brushes.php?c1=6

We've used these thin discs for years without warping them Matt. Not saying it doesn't happen, but remember brakes just slow you down.

It sounds like a tremendous effort, sorry George.....

Brent, can the flex hone be used without a lathe? I don’t have access to a lathe, drill sure...
Thanks! David

Good thought. I was thinking in a mill with rotary table and you could fairly uniformly go around in one pass with even pressure.

bwaller · « **Reply #16 on:** October 16, 2019, 02:11:43 PM »

Don't be fooled guys, stock rotors don't glaze so quickly. It's easily done and part of my race prep is all. It doesn't matter anyway, I don't mean to turn this into an oil tread.

David, ideally the discs should be turned slowly (375rpm I believe) as well as the flex hone. You could even raise the front end and get someone to turn the wheel while you run the drill! It does take several minutes each face. Get a coarse hone.

Captain · « **Reply #17 on:** October 16, 2019, 02:43:30 PM »

The material is 420 Stainless and this was used in the "Works" Nissin GP and Superbike disc's of the time. In fact it is still used for performance disc's by many manufacturers to this day.

Captain

turboguzzi · « **Reply #18 on:** October 16, 2019, 04:34:50 PM »

Nice ones captain!

Never experienced glazing, i tend to think (but dont have a proof) that if it happens its because the pad compound was not aggressive enough. The brembo SC compound pads which i modify for my F05 and F08 calipers certainly seem to "eat" into the SS material....

agree that if you run a single disc it needs to be thicker in order to have similar heat sink capacity to two thinners ones.

gschuld · « **Reply #19 on:** October 17, 2019, 04:24:26 AM »

http://moto.brembo.com/en/tips/four_materials_and_just_one_disc

In the general FWIW category.

It seems the cast iron rotors really liked the now banned asbestos pads.

George

bear · « **Reply #20 on:** October 18, 2019, 04:14:05 AM »

Quote from: gschuld on October 17, 2019, 04:24:26 AM

http://moto.brembo.com/en/tips/four_materials_and_just_one_disc

In the general FWIW category.

It seems the cast iron rotors really liked the now banned asbestos pads.

George

According to to that link I'm living in the mid 80's

turboguzzi · « **Reply #21 on:** October 18, 2019, 06:08:57 AM »

brembo and ferodo still make pads for the iron discs, maybe not as efficient as the asbesto type or a race grade but they exist also without asbestos

My 81' Le-Mans has iron discs and when ill get it back on the road, theyll be replaced by SS... In a street bike that sees all rainy weather and maybe sits for weeks unused, they would go rusty in no time, was a pain in the behind every time i rode again. Rust dust everywhere and the agressive disc surface would noisily sand off a nice layer of pad material...

I guess thats what killed cast iron, not the pads, they are just hard to live with.

gschuld · « **Reply #22 on:** October 18, 2019, 07:24:08 AM »

Captain,

The 420 stainless comes up often in my searches. Some add a (+/- 10%) chrome content for the cruiser crowd. Your discs are gorgeous👍

Bear, stuck in the 80s. Could be worse I guess😁

Yossef, I’m not stuck on any particular path regarding rotors, but I do enjoy learning about the options and why people use what they use. A friend races a cr750 with cast iron rotors on factor carriers with genuine AP Lockheed calipers mounted to 77-78 f forks(Racetech internals). He is very happy with the combination. I’ll ask what brake pads he is using.

Brent, good to know the glazing maintenance isn’t too big of a deal.

George

Phil · « **Reply #23 on:** October 22, 2019, 11:43:58 PM »

I had a pair of these discs made about 10 - 12 years ago. I don't know what the steel is but was assured it was the same grade as the Moto GP teams were using in wet conditions (when carbon fibre disc couldn't be used). Interestingly, they have been zinc plated - not to stop them rusting but to improve the braking. It was explained to me that under braking, the zinc "smeared" over the surface and provided a better surface than the uncoated steel. Over time, they have oxidised hence the don't look very pretty now! I've never used them, as you can see, so cannot comment on their performance. What I can say is, back when I had them made, the very top UK classic race bikes tended to use them (always with AP Racing CP-2696 callipers) and had them made by the same chap (ex-Kenny Roberts Proton engineer) who made mine. But I guess things have improved today ...

Phil · « **Reply #24 on:** October 22, 2019, 11:49:53 PM »

Many of the top classic race bike teams in the UK have their discs made by ABE in London. They made one for me and its great.

http://www.allbikeengineering.co.uk

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Author Topic: Stainless Material specifics for brake discs. (Read 4016 times)