FYI Part Numbers for Silver Arrow Brake Components

[szvook]

ADMIN EDIT: This post was copied & edited from a different thread located at this link. Adding as a sticky in this subforum for future reference.

Here are some part numbers.

334mm Brembo front caliper (Black color)​

• Part# 001-420-77-83 Left​

• Part# 001-420-78-83 Right - NLA​

​

334mm Brembo front caliper (Silver Color)​

• Part# 001-420-99-83 Left​

• Part# 002-420-00-83 Right​

​

300mm Ate rear caliper (Unpainted)​

• Part# 001-420-37-83 Left - NLA​

• Part# 001-420-38-83 right​

​

300mm Ate rear caliper (Silver color)​

• Part# 129-423-03-98 Left - NLA​

• Part# 129-423-04-98 Right​

​

Front brake rotors & pads:​

• Size: 334mm x 32mm - part# 129-421-21-12 (non-drilled/solid, late SL500/SL600) - NLA (available aftermarket)​

• Size: 334mm x 32mm - part# 129-421-23-12 (cross-drilled, Silver Arrow models) - NLA (available aftermarket)​

• Front pads - part# 005-420-04-20​

​

Rear brake rotors & pads:​

• Size: 300mm x 22mm - part# 129-423-03-12 (non-drilled/solid, late E500 Euro, late SL500/SL600)​

• Size: 300mm x 22mm - part# 129-423-05-12 (cross-drilled, Silver Arrow models)​

• Rear pads - part# 003-420-30-20 or 004-420-93-20​

​

Caliper hardware (note the quantities vary):​

• Front caliper pins - part# 001-991-51-60 (1 per caliper)​

• Front caliper spring - part# 000-421-97-91 (1 per caliper)​

• Rear caliper pins - part# 001-991-27-60 (2 per caliper)​

• Rear caliper spring - part# 000-421-64-91 (1 per caliper)​

• Rear caliper bolts - part# 003-990-22-00 (4 total required for two calipers)​

​

Rear dust shields (for early cars with small dust shields):​

• Left/driver side - part# 210-420-14-44​

• Right/passenger side - part# 210-420-15-44​

• Note: Replacing the dust shields also requires replacing the rear wheel bearings. This is a major job, special tools are needed. The alternative is to cut/trim the small dust shields so they clear the larger rotors.​

​

Late-style front lower control arms, required if car has early-style control arms:​

• Left/driver side, standard - part# 124-330-34-07 - NLA​

• Right/passenger side, standard - part# 124-330-35-07 - NLA​

• Left/driver side, Sportline - part# 124-330-36-07​

• Right/passenger side, Sportline - part# 124-330-37-07​

• Note: Aftermarket LCA's are generally not recommended, regardless of brand name. As of May-2021, the OE/Genuine Sportline LCA's are recommended if needed to replace the early-style LCA's used on 500E's that came from the factory with 300mm front brakes.​

I use Porterfield brake pads, the R4-S model and have been extremely happy with them, street and track tested. In case the part numbers are needed, see below.

• AP-847 - front 334mm pads​

• AP-603 - rear 300mm pads​

Also - there is no need to upgrade the factory brake booster or master cylinder for the SA kit, when installing on a 124.034 (400E/E420) or 124.036 (500E/E500).

 

[jnes]

This might be discussed previosly but is there front dust shield upgrade available? I have currently old style LCA:s and those have issues with rotor clearance.

Will the old style dust shield clear the rotor when new style LCA is installed?

I'm about to modify dust shields in LCA knuclke if they would clear the rotor in top side.

 

[gsxr]

The old dust shield will work fine - no problem at all, it's just slightly smaller diameter.

The larger dust shields are NLA.

If you can get >2mm air gap from the early LCA to rotor, and cut a hole in the shield, you don't have to use the late LCA's.

 

[jnes]

Are the late dust shield part numbers A129 420 18 44 & A129 420 19 44 ?

Seems that MBCC have those available. Price is high to just try if they will fit or not..

 

[gsxr]

Are the late dust shield part numbers A129 420 18 44 & A129 420 19 44 ?

Yes, those are the "large" shields used with 320mm and 334mm front brakes.

Seems that MBCC have those available. Price is high to just try if they will fit or not..

I'm only seeing the right side available per MBCC, the left side (#18) shows as NLA. Price in USA is ~$500/pair MSRP, which is crazy. You'll need to contact a dealer to confirm availability.

Note that these are not drastically larger than the smaller shields, they are ~330mm diameter. The small shields (used with 294/295mm .034/.032/etc brakes) are ~305mm. I haven't had a loose "medium" shield from 300mm brakes to measure but I assume it will be somewhere around ~310mm diameter. If your existing shields are in good shape I'd leave them alone.

Mercedes-Benz Classic Parts Search.

Browse through the Mercedes-Benz Classic Parts Search to see the availability of parts, promotional and newly manufactured parts and order them online (only in Germany).

partssearch.mercedes-benz-classic.com

 

[jnes]

How about the front caliper bolts? Is it necessary to replace for installation?
I test fitted fronts and seems that bolts are a bit too long for the front calipers.. I currently have early Brembos..

 

[gsxr]

How about the front caliper bolts? Is it necessary to replace for installation?
I test fitted fronts and seems that bolts are a bit too long for the front calipers.. I currently have early Brembos..

No need to replace the front mounting bolts. If they are longer than necessary, the extra length should not interfere with anything.

 

[Whitemamba23]

does anyone have an idea where I can get OEM or OE (or better) quality rear brake pistons? Rebuilding my rear calipers and the only thing I can’t find a part number for are the pistons.

 

[gsxr]

does anyone have an idea where I can get OEM or OE (or better) quality rear brake pistons? Rebuilding my rear calipers and the only thing I can’t find a part number for are the pistons.

The pistons rarely need replacement, but if so, I'd shell out for remanufactured calipers instead of messing with rebuilding yours...

 

[Whitemamba23]

The pistons rarely need replacement, but if so, Id shell out for remanufactured calipers instead of messing with rebuilding yours...

I figured since I’m already taking them apart to clean and paint that I should replace the seals. Pistons look fine but the surface rust(?) scared me a little. Pics attached. Are these good to re-use? Any recommendations on how to get them cleaned up properly prior to putting them back in? Special solutions or chemicals to soak them in?

 

[TerryA]

@Whitemamba23,
I rebuilt a lot of MB calipers and looking at those pistons I would only be concerned about the piston sides (the shiny parts). I would just use a fine steel wool on the surface by rotating it horizontally (perpendicular to the in/out direction. Make sure the circular groove is real clean. The rusty part makes no difference in its operation. If you want you can clean the outer ring in front of the groove. Just don’t scratch the piston surface. Don’t try to remove all of the marks on the pistons.

Note if there are any deep vertical scratches on the pistons (in/out direction) they could possibly leak.

You can shine up the caliper cylinder the same way with the steel wool. Wash everything down with brake cleaner and blow it dry with compressed air. Reassemble with the new O-Rings and a little brake fluid. Make sure the O-Ring goes in without twisting.

I would paint the calipers after you reassemble the pistons because the brake fluid takes the paint off.

After they’re back on the and working check them for leaks. More than once just to be safe.

 

[gsxr]

Those don't look bad to me - pretty sure they are serviceable. @JC220, our resident iron oxide boffin, could confirm. There are some rust-dissolving solutions which may work to eliminate what's there, followed by Terry's cleaning regimen.

 

[Whitemamba23]

@TerryA @gsxr thank you for your help. @JC220 what’re your thoughts on a solution to get these cleaned up nicely?

 

[sheward]

For reference's sake, I'm showing 335mm diameter for part no.s 129 420 21 44 and 129 420 22 44 (front dust shields)

I agree with the others, those pistons should clean up fine with some steel wool. I obtained seal kits from one of the chain auto parts stores just a few years ago for the rear calipers.

 

[chicky]

ADMIN EDIT: This post was copied & edited from a different thread located at this link. Adding as a sticky in this subforum for future reference.

Here are some part numbers.

334mm Brembo front caliper (Black color)​

• Part# 001-420-77-83 Left​

• Part# 001-420-78-83 Right - NLA​

​

334mm Brembo front caliper (Silver Color)​

• Part# 001-420-99-83 Left​

• Part# 002-420-00-83 Right​

​

300mm Ate rear caliper (Unpainted)​

• Part# 001-420-37-83 Left - NLA​

• Part# 001-420-38-83 right​

​

300mm Ate rear caliper (Silver color)​

• Part# 129-423-03-98 Left - NLA​

• Part# 129-423-04-98 Right​

​

Front brake rotors & pads:​

• Size: 334mm x 32mm - part# 129-421-21-12 (non-drilled/solid, late SL500/SL600) - NLA (available aftermarket)​

• Size: 334mm x 32mm - part# 129-421-23-12 (cross-drilled, Silver Arrow models) - NLA (available aftermarket)​

• Front pads - part# 005-420-04-20​

​

Rear brake rotors & pads:​

• Size: 300mm x 22mm - part# 129-423-03-12 (non-drilled/solid, late E500 Euro, late SL500/SL600)​

• Size: 300mm x 22mm - part# 129-423-05-12 (cross-drilled, Silver Arrow models)​

• Rear pads - part# 003-420-30-20 or 004-420-93-20​

​

Caliper hardware (note the quantities vary):​

• Front caliper pins - part# 001-991-51-60 (1 per caliper)​

• Front caliper spring - part# 000-421-97-91 (1 per caliper)​

• Rear caliper pins - part# 001-991-27-60 (2 per caliper)​

• Rear caliper spring - part# 000-421-64-91 (1 per caliper)​

• Rear caliper bolts - part# 003-990-22-00 (4 total required for two calipers)​

​

Rear dust shields (for early cars with small dust shields):​

• Left/driver side - part# 210-420-14-44​

• Right/passenger side - part# 210-420-15-44​

• Note: Replacing the dust shields also requires replacing the rear wheel bearings. This is a major job, special tools are needed. The alternative is to cut/trim the small dust shields so they clear the larger rotors.​

​

Late-style front lower control arms, required if car has early-style control arms:​

• Left/driver side, standard - part# 124-330-34-07 - NLA​

• Right/passenger side, standard - part# 124-330-35-07 - NLA​

• Left/driver side, Sportline - part# 124-330-36-07​

• Right/passenger side, Sportline - part# 124-330-37-07​

• Note: Aftermarket LCA's are generally not recommended, regardless of brand name. As of May-2021, the OE/Genuine Sportline LCA's are recommended if needed to replace the early-style LCA's used on 500E's that came from the factory with 300mm front brakes.​

I use Porterfield brake pads, the R4-S model and have been extremely happy with them, street and track tested. In case the part numbers are needed, see below.

• AP-847 - front 334mm pads​

• AP-603 - rear 300mm pads​

Also - there is no need to upgrade the factory brake booster or master cylinder for the SA kit, when installing on a 124.034 (400E/E420) or 124.036 (500E/E500).

Hello szvook

If you may add to your list above the caliper repair kit part numbers for the front and rear Silver Arrow calipers ...

Thank you in advance

 

[jnes]

Does anybody know the tightening torques when rebuilding SA calipers? Both Brembo and Ate has bolts (Allen) which are holding the brake halves together. I have tried to search this torque rating but no luck so far.

 

[jnes]

Are there some special tool to install dust caps to caliper pistons? Or just using proper socket when pressing the dust boot to its position?

Btw have you used than ATE piston alignment tool to ensure proper piston position when assembling the pistons?
FSM recommends to use that.

20° piston gauge

Adjustment and testing gauge for 20° piston adjustment in the brake caliper in combination with the ATE piston turning tool....

www.ate-info.de

What is the piston diameter in SA rear calipers?

 

[gsxr]

Are there some special tool to install dust caps to caliper pistons? Or just using proper socket when pressing the dust boot to its position?

Good question. I am not sure.

Btw have you used than ATE piston alignment tool to ensure proper piston position when assembling the pistons?
FSM recommends to use that.

I'm sure the tool is super nifty, but this can be done without the tool. Use pliers to carefully rotate as needed, and do not damage the piston where the pliers grip.

What is the piston diameter in SA rear calipers?

Pretty sure most of the 300x22 rear calipers have 42mm diameter pistons.

 

[Ertech]

Just did the swap and on a side note the 2 dowels on each hub need to be removed for the new disc to fit

 

[jnes]

I'm about to try those Porterfield pads. I'm having conversation with this place (or at least they could send across the pond those pads) LPI racing. Brakes, Safety Gear, Suspension for Street and Track - LPI Racing - LPI Racing. Shipping costs are quite massive $110 + customs + VAT So I'm wondering are there another good options such as EPC?

Has anybody ordered in this place? They are offering several kind of pads. Any suggestions which I should select? Racing, endurance or street?
I'm not going to take my car in the race track but how about the brake dust? Street pads might the proper but how those Porterfield pads compares f. ex EBC pads? Any thoughts?

Thanks!

 

[gsxr]

I've purchased from LPI Racing, they're a good outfit.

I use the "street" compound pads (R4-S). I don't know what the race compounds are like for normal street use, other than probably quite dusty/dirty and may have a shorter lifespan. The R4-S work well for street use.

I don't know how these compare to EBC pads, they're likely somewhere in between the Green and Yellows. The Yellows should perform better but are expensive and quite dusty, from what I hear (I've never used them, yet). There's an old forum thread on EBC's which may have more info.

 

[szvook]

@jnes Have you tried to contact Porterfield directly and see what they might charge for shipping?

 

[jnes]

No, but thanks for the tip

 

[BRABUS124]

I had one in for, service

 

[BRABUS124]

And to add for the info about the springs on this. I changed them for the customer who wanted it lowered.
So here are the original set with color coding on them.
The car were ekstreemly nice and well kept in great kondition.
Mercedes uses difrent springs point system so it can differ from model to model depending on the equipment it were sold with. So here are the data as well to have it all covered
VIN WDBFA68F42F203121
FIN WDB1290681F203121

 

[Rado]

Aloha
What are the chances that someone with and eagle eye can help me?
I found a 00 sl500 parting out locally and asked about the brakes, he doesn’t know what silver arrows are but he has a few sl for parts and states one of them has bigger brakes.
I could only get this pics, what u think, are they black painted bigger brakes we are looking for?
I wan them on my 94 E500

Thanks

 

[sheward]

Not all "silver arrow" brakes were silver. Those should be the brakes you want. They were used on all R129 500SLs from 1999 thru 2001.

Part numbers are listed at the top of this post.

Mounting these will require some trimming of the brake splash shields as well as longer mounting bolts in the rear. I suggest reading up on the process if you have not already. Good time to replace the brake lines as well. I would purchase the set of lug bolts shown as well. They will not work with spacers however they may be 85mm which some on the board are looking to buy.

 

[gsxr]

Not all "silver arrow" brakes were silver. Those should be the brakes you want. They were used on all R129 500SLs from 1999 thru 2001.

Drew is correct, those are indeed the brakes you want. 100% bolt-on for a 1994 E500.

Mounting these will require some trimming of the brake splash shields as well as longer mounting bolts in the rear. I suggest reading up on the process if you have not already.

Fortunately, the 1994 E500 already has late LCA's up front, and also larger rear dust shields - no trimming required! You DO need the longer rear caliper mounting bolts. Make sure to get them from the donor car. New bolts are silly priced now.

Good time to replace the brake lines as well. I would purchase the set of lug bolts shown as well. They will not work with spacers however they may be 85mm which some on the board are looking to buy.

Yup, good time to install stainless braided hoses while you're in there. I like the Deerfield Precisions. Not sure what brands currently available have the correct 17mm hex fitting on the front hoses (as Deerfield does). The lug bolts may indeed be the 85mm total-length, extended-head style... these will work with "bolt on" spacers (minimum 20mm thickness), but not "pass through" spacers.

 

[Rado]

Your reply’s are much appreciated.
Today doing the coolant flush, waiting for it to cool down and brakes are next.
Braided hoses are coming. Need to see the condition of the calipers and most probably I’ll put new seals on them. Can’t order the rotors, pads and seals until I have the calipers on hand.

 

[szvook]

Yup, good time to install stainless braided hoses while you're in there. Not sure what brands currently available have the correct 17mm hex fitting on the front hoses (as Deerfield does).

Goodridge did at one point, that is what I’m using.

 

[gsxr]

Braided hoses are coming. Need to see the condition of the calipers and most probably I’ll put new seals on them. Can’t order the rotors, pads and seals until I have the calipers on hand.

99% of the time, no need to replace the caliper seals. Only the dust seals are sold by Mercedes, the internal piston seals need to be sourced from aftermarket suppliers of Brembo repair kits - AFAIK, nobody has done this and shared the part numbers needed. What I do is cycle the pistons through their range of motion using compressed air with a block of wood simulating the rotor, to prevent the pistons from popping out. Press back in, repeat. If all four pistons move smoothly and evenly, you're golden. It will be really obvious of 1 sticks while the others move normally.

 

[Rado]

I can’t find the brands of braided hoses you guys mention previously. Looks like they’re out of business.
I did found stoptech and techna fit. Any opinions on them?

 

[gsxr]

Shoot, I'm getting an error at Deerfield too. I emailed the owner... will see what he says.

Deerfield Precision

Never heard of "Techna Fit". Stoptech is a good brand name, but the hoses shown in the photo above are not correct for the 124 chassis - might just be a generic photo (which drives me crazy).

 

[szvook]

Tire Rack used to carry the Goodridge G-Stop stainless braided hoses. But it looks like they are out of stock now. Part number 34011 - Click me

 

[gsxr]

I can’t find the brands of braided hoses you guys mention previously. Looks like they’re out of business.

@Rado - Deerfield is still in business, but they are having technical problems with their website. I was able to contact the owner (J.B.), he said he can set up a manual order for anyone who wants to buy a set of hoses.

Contact J.B. directly via email at: support@deerfieldprecision.com

 

[Rado]

@Rado - Deerfield is still in business, but they are having technical problems with their website. I was able to contact the owner (J.B.), he said he can set up a manual order for anyone who wants to buy a set of hoses.

Contact J.B. directly via email at: support@deerfieldprecision.com

That’s cool, thanks. I have the email in drafts ready to go. I should have the brakes today.
Are the hoses the same for regular brakes on e500 and silver arrows? Asking in case the brakes I’m waiting are not the right ones, just want to put the order asap.
Thanks

 

[gsxr]

Are the hoses the same for regular brakes on e500 and silver arrows? Asking in case the brakes I’m waiting are not the right ones, just want to put the order asap.
Thanks

Yup, same hoses for 124 chassis, regardless of the calipers.

 

[Rado]

Yup, same hoses for 124 chassis, regardless of the calipers.

Still don’t have an answer for the hoses but the calipers are here.

 

[Rado]

Hey, just got the invoice from Deerfield Precision
If someone’s still interested in the pricing, here’s the invoice.

 

[gsxr]

Thanks for the update! Nice to see tariffs haven't hit these yet... same pricing as probably 10 years ago.

 

[VT Blue]

Late to the party but the Porterfield R4-Ss that @gsxr mentioned are available at Pelican Parts.

FWIW, I am on my second set of MB rotors that more closely resemble waffle irons after not too many miles, and I now need to replace them with something aftermarket...I'm not going through this again.

Any suggestions?

And I'll give the Porterfield pads a shot -- my current ones produce dust that closely equals that of a coal-fired steam engine...

Thanks.

 

[gsxr]

VT, what brand rotors have you been using? Also, what size front brakes - 300, 320, or "Silver Arrow" 334mm?

Porterfield R4-S are medium dust, but tend to have very good feel / modulation. What pads have you been using?

 

[szvook]

Late to the party but the Porterfield R4-Ss that @gxsr mentioned are available at Pelican Parts.

Just get the pads directly from Porterfield and here’s why. The front pads need 4 sensors holes to be drilled near the backing plate (rear pads are ok), otherwise two holes might be towards the center of the pad. You just need to tell Porterfield to have 4 sensors holes to be drilled near the backing plate. Full info is here Brake pad’s sensors hole

Porterfield mentioned that the pads holes are spec’d out from the manufacturer to be 2 pieces close to the backing plate and 2 pieces towards the middle. Their only thought was the engineers wanted to alert you when you were halfway through and then again when it needed replaced.

With the holes in the middle, the sensor will not reach it, as it’s on a short wire. So that is the main reason to have all holes near the backing plates for E500E’s brake pads.

 

[VT Blue]

Just get the pads directly from Porterfield and here’s why. The front pads need 4 sensors holes to be drilled near the backing plate (rear pads are ok), otherwise two holes might be towards the center of the pad. You just need to tell Porterfield to have 4 sensors holes to be drilled near the backing plate. Full info is here Brake pad’s sensors hole

Porterfield mentioned that the pads holes are spec’d out from the manufacturer to be 2 pieces close to the backing plate and 2 pieces towards the middle. Their only thought was the engineers wanted to alert you when you were halfway through and then again when it needed replaced.

With the holes in the middle, the sensor will not reach it, as it’s on a short wire. So that is the main reason to have all holes near the backing plates for E500E’s brake pads.

@szvook thanks sooooo very much. You just saved me hours of cursing and aggravation.

Much, much appreciated.

Bob

 

[szvook]

@VT Blue Btw, here’s the bedding procedure from Porterfield for their pads, in case you need it.

 

[VT Blue]

VT, what brand rotors have you been using? Also, what size front brakes - 300, 320, or "Silver Arrow" 334mm?

Porterfield R4-S are medium dust, but tend to have very good feel / modulation. What pads have you been using?

Hi, Dave!

I've been using standard MB rotors and pads.

Per Pierre's team, we were using unidirectional rotors (1294212012), which I believe are the 300s.

Either way, the last two sets of rotors (including what I have on right now), were horribly warped after a little bit of time, and it's not as if I was hooning -- not in the least. Pedal feel/vibration upon braking was well outside of acceptable.

The pads made my front wheels darker than any car I've ever owned, even after mostly highway driving.

I did go ahead and order the Porterfield R4-Ss as nothing can be worse than what I had. I have not ordered rotors yet as I don't know who I should consider, and am hoping for experienced folks such as yourself to suggest something that's reliably good.

Thanks, Dave!

Bob

 

[VT Blue]

@VT Blue Btw, here’s the bedding procedure from Porterfield for their pads, in case you need it.

View attachment 213565

Many thanks @szvook !

 

[szvook]

@VT Blue I’ve been running front and rear rotors from Zimmermann for my SA brakes with excellent results. Porterfield also sells Zimmermann front and rear rotors for the SA kit.

 

[gsxr]

I've been using standard MB rotors and pads.

Hmmm. That is interesting. Usually, the dealer rotors are top-quality units. Was there any COO that you recall on the last set or two of rotors?

Per Pierre's team, we were using unidirectional rotors (1294212012), which I believe are the 300s.

Yes, those are the 300x28 standard fronts.

Either way, the last two sets of rotors (including what I have on right now), were horribly warped after a little bit of time, and it's not as if I was hooning -- not in the least. Pedal feel/vibration upon braking was well outside of acceptable.

There's a slight chance this was caused by material transfer between pad & rotor, not necessarily that the rotor itself was warped - but it would require measuring runout with a dial gauge to verify.

The pads made my front wheels darker than any car I've ever owned, even after mostly highway driving.

MB OE pads are known for being very dusty / dirty, which explains what you were seeing.

I did go ahead and order the Porterfield R4-Ss as nothing can be worse than what I had. I have not ordered rotors yet as I don't know who I should consider, and am hoping for experienced folks such as yourself to suggest something that's reliably good.

The only other brand besides Genuine Mercedes that I'd recommend is Zimmerman Coat-Z. Personally, after I had a bad experience with Brembo years ago, I avoid Brembo rotors like the plague.

https://www.fcpeuro.com/products/brake-disc-zimmermann-400-1419-20

 

[gsxr]

From Zimm's website FAQ's (link):

Warped brake disc:​

​

If vibrations occur under thermal load, the cause is often a "warped brake disc". If the measurement of the brake disc thickness also delivers differing values, the following diagnosis will be regarded as confirmed: Brake disc bent, brake disc "wobbles”, brake disc non-circular, brake disc warped, etc.​

​

But the actual cause of the above stated phenomenon is a different one:​

​

State-of-the-art brake pads are designed for adhesive friction. During a correct run-in braking of the brake disc/pad system a very thin, homogeneous layer of brake pad material is formed through a diffusion processes, on the friction surfaces of the brake disc. Thus there are two friction surfaces (brake disc and pad) which in the marginal zone more or less consist of the same material (particles); a shifting may occur in both directions (diffusion). Thus, the chemical bonds between casting and pad materials can break apart or develop new. This process takes place continuously since there is a smooth transition threshold between the friction surfaces of the brake disc and brake pad.​

​

Failure to observe the brake-in process as well as a non-observance of the run-in phase will cause the formation of uncontrollable and uneven deposits of friction material on the braking surfaces which will result in a partial thermal over stressing of the braking surface. The irregular deposits, which protrude from the surface of the disc will be warmer than the surrounding cast iron. During each contact (once per revolution) of the brake pad with the leading edge of a deposit will increase the temperature at this point. At a temperature between 650° C and 700° C, the cast iron under such a deposit will transition to cementite, and deposits of very hard iron carbide (Fe3C) will form in the crystal lattice of the cast iron. Under very high mechanical and thus thermal loading of the brake, this process is facilitated even more - causing an escalation effect. With an increasing temperature, the cementite will build up and simultaneously penetrate deeper into the brake disc material. Ultimately this process will lead to the above described symptoms, such as rubbing, beating or pulsation of the brake. This can only be remedied through an exchange of the brake discs and brake pads.​

​

It should be noted that the actual cause is not due to a faulty disc. The process described above set into motion through assembly errors, failure to observe the run-in regulations, etc. which damage the originally flawless brake disc.​

​

Additional note:
If you attempt to remove deposits which are not or only barely visible without optical aids through abrasive measures (such as emery cloths, sandpaper, etc.), the condition of the brake disc will worsen even more, since the abrasive particles (mainly alumina) penetrate into the edge layers of the brake disc’s friction surface. For the same reason, these deposits should not removed by sand blasting.​