Lioninstreet

So my Merc has the six pot 340mm x 32mm rotor brake setup on the fronts and a set of rotors is in my near future.


I'm wanting to run something past everyone. Besides the cost issue, why can't I just have a caliper bracket machined that would allow the caliper to move out enough to replace the 340mm rotor with the 360mm x 32mm rotor on the later '63 and 030 r171 slk55?

The part numbers on each of the six pot calipers are different between the rotor applications. But from everything I've found so far, the difference is the caliper bracket, not the actual caliper.


The last thing I have to confirm is the casting number between the two calipers. On the smaller rotor's caliper it is 20.8885.031a (driver side). Does anyone who has the 360mm rotor setup able to see the casting number down at the front bottom of the caliper?


I've also compared the part number for the brake pads. Here's where it get's a bit confusing. From what I found comparing part numbers, both the 340 & 360 rotor uses the same pad... you'd think the height of the 340 pad would be a bit smaller since the swept area of the rotor is smaller.


Any help on this would be appreciated.

floridawriter

Just curious why you want to upgrade. The brakes you have are the same as on my car yet your's is lighter. They are awesome brakes. Increasing the rotor size increases unsprung weight which will affect handling and performance.

Lioninstreet

The upgrade would bring the brakes up to the 030 spec.


That is the primary reason I'm looking at it. I don't auto cross so the minor change in weight for the larger rotor isn't a deal breaker for me. I just want to slow down faster when some idiot changes lanes in front of me.


Brembo actually has a 380x32 rotor they use with their Gran Turismo 6 pot caliper kit that really looks sweet, but is cost prohibitive.

Since my 340x32 rotors are end of life, it seems like a relatively easy upgrade presuming the calipers are the same. 360x32 rotor prices seem to be coming down as well.


While seeking to evaluate the caliper, the swept area of the pad is something I'm also trying to work out. The larger rotor wont do squat if the pad isn't also larger that what's currently in the caliper.

cm60k

Your stock brakes are brilliant, if you want to upgrade it, go with CLK63, 360x32, it's great brakes, comparing to the weight/mass of all suspension and carving brake performance, of your nice SLK55,,

i don't think it's worth it, if you go with bigger than that..!!

ZAYED,,

Tex5

If you really want bigger than 360*32, upgrade to CLk 63 BS 360*36 (caliper need to be changed) or bigger (390*36 from C63 BS) but you will need 19" rims

Lioninstreet

@Tex5


You hit the nail on the head. I have three piece 19's on the car already.


@cm60k,


The 380x32's are probably overkill since my car is lighter. One thing for sure they are way too expensive ... $4500. That's half the cost of the Kleemann SC.


I posted here to explore this upgrade on my standard '55 because most owners on the "other" SKL forum/web site aren't as hard core mod oriented as you guys are here.


I'm just lucky that my SLK was an early one ('06) and already has the bigger six pot caliper.

whtnkls911

The only reason to upgrade the size of the rotor would be for reducing heat/fade. Unless you track the car you will not see improvement in street driving. The improvement would be for the bigger rotor not to fade as heat builds, not to shorten your stopping distance.

tw2

Exactly as above. There will be absolutely no braking improvement from changing rotors alone. It would only increase the thermal reservoir to lower fade which i hope no one encounters on the highway. Just buy the correct horrendously expensive ones and enjoy your awesome car.

Lioninstreet

I find this somewhat odd.


If there was absolutely no benefit to a street driver to use a larger brake setup (ie. larger rotor and pad), what possible reason would Merc have to offer the upgrade the SLK55 030/black as an option?


They must have been something on the minds of the engineers. Even on the CLK55 to CLK63 model year upgrade the brakes were larger due to the added HP.


I'm probably up in the low 400 hp area with my mods (Kleemann headers, primary cat delete, x-pipe, green filter) up from 355, so wouldn't the same theory the Merc engineers had apply to my home brewed mods?


I'm really wanting to go with the larger rotor, that is if the upgrade is doable and a larger pad is also available, even if it means going aftermarket.


If anyone would care to share the casting numbers of their calipers who's running a '63 non black?


(by the way the floating 340x32 rotors are down under $500 now for the pair from Tarox for those who have the CLK '55's).

tw2

Because you are talking about rotors only. Bigger pads need bigger calipers. Bigger calipers need larger rotors. Not the other way around. There is the expectation that some owners will race. Also no one will buy an expensive performance car with tiny rotors. The other reason is that most people expect an improvement in stats ie rotor size thickness, pot count etc from one generation to the next, regardless of whether it is required or not.

Upgrading calipers and rotors is worthwhile. Rotors only will not lead to any improvement in my irrelevant opinion. It will increase unsprung weight as already mentioned.

Lioninstreet

@ tw2, I think we both see this the same way. But no, I am not talking about rotors only.

If you look at the op, down at the bottom of the post I stated the part number (Merc) for the pads appear the same between the 340x32 and the 360x32 rotors. But it was not always like this. Late in 2006 the two part number were merged into one.


This is why I am looking at the aftermarket for a larger pad that would fit the 6 pot caliper. Good chance there might be something out there.


But before going too deep into the pads, I wanted to make sure the caliper casting is the same between each model. If I cant take advantage of the larger swept area of the 360 rotor to support a larger pad, it isn't worth doing the mod.

So I do get it that just having a larger rotor wont do much for me unless I can find a larger set of pads too. If the caliper casting is the same for both rotors, then I'll start looking for a larger set of pads.


Once all this research is sorted out, the plan would be to swap everything in at once.

tw2

I am very far from an expert. If the pads are indeed larger with the same caliper... The way I see it is that you have the same clamping force (same caliper) over a larger pad which is less force per area. Is that better, the same or worse than more force per area on a smaller pad? No idea. At best I can't imagine it being a significant increase.

I don't know how good the stock pads are but aftermarket pads for your stock setup would probably provide better stopping power without having to change anything. I know on previous cars I have owned that aftermarket pads are hugely better than stock if chosen carefully. I would only bother changing the rotors if you are moving to larger calipers. Otherwise it is just increased unsprung weight and fade resistance which you don't need. I don't believe you will get any benefit from larger pads alone.

Lioninstreet

I checked the master cylinder and it is the same between the 340x32 and 360x32 rotor, at least on the SLK. I didn't check comparing the CLK55 to the CLK63 nBS.



Your probably correct that a 20mm larger rotor with the same caliper and larger pad would not be a significant increase. But the clamping force is also calculated per area of the pad to rotor not simply caliper piston to pad.


Unless your talking an extremely undersized caliper, if pad to rotor area increases, generally braking power increases. I don't expect a dramatic improvement like going with the '63 BS or the Brembo GT, but I'm not spending $4k+ either.


As mentioned my current rotors are toast (worst case $1300 from racing brake) a set of brackets (+/- $500) and good pads ($150-$200). So for under $2k I have what would probably be a better setup than the 030 SLK Merc/'63 nBS due to the aftermarket pads.


If I leave well enough alone my alternative is $600 for the Tarox 340x32 rotors and another $200 for good pads.


So my thinking is: spend the extra $1100 (worst case) for a bit more braking swept area. No?

tw2

More swept area but still with the same clamping force. I would get the racing brake rotors and better pads. This will definitely increase braking performance.

floridawriter

I have RacingBrake rotors and pads at all four corners. The brakes are definitely a big increase over stock and the the reduction in unsprung weight gave me faster acceleration and even better steering and handling. I'd definitely recommend them.

Lioninstreet

Surprised no one has the casting number for the front calipers on the clk63 nBS.


But I do appreciate the thread activity and replies, especially considering I have a r171 '55, not a w208-w209.


I too have heard great results from those using RacingBrake. Tarox's products are far more common in GB and Europe so we don't get to hear much about them over here.


I don't have the Brinell specs on Tarox, but I read that the $1300 RacingBrake rotors tested between 193 & 196 on the Brinell hardness scale. Brembo's (now about $600 a pair on Amazon) are about 145. Stoptech also has floating rotors for $1000 that are around 171 hardness.


That makes RacingBrake rotors about 34% harder than OE, 14% harder than Stoptech, and explains why my OE rotors are nearly toast at 40k miles.

But I have to be honest. Even though the clamping force would be the same (especially if it's true that the same caliper is on both the 030 and early non-030 like mine), I'm still toying with the idea of swapping in the larger pad & rotor as an upgrade.


Because if it's doable, for at most an extra $1k I can get whatever improvement the 030 setup would give me. Plus I'd have a better than OE/Brembo rotor and pad.

whtnkls911

Lioninstreet,

At $1K the upgrades you are considering are roughly the cost of replacing with a good set of rotors and you might even see a difference in feel if you upgrade to more aggressive street pads. I will warn you though, do not get pads that are to aggressive, such as true track pads. True track pads squeal and chatter like crazy and make noises that you will not be happy with. As well they do not work when cold, literally until up to temp they do not work. So on a cold morning or in the rain your brakes will be ineffective. I have a ton of experience with true track pads on my 911 which is a track car. It is licensed for the street an I can drive to to the track but I change pads before and after an event for these reasons. The last consideration fro true track pads is that they eat rotors, your service life will be considerably less. Good luck and post your results if go this direction I would like to hear the outcome.

Lioninstreet

@whtnkls911


Thanks for the advice on the track pads, that would be far to aggressive for my use for sure.


On the upgrade, I'm on hold until the casting numbers on the '63 nb or 030 SLK caliper can be verified as the same as the pre-facelift SLK 6pot on my ride.


I'll be comfortable paying for the one off brackets to move the caliper for fitment on the 360x32 rotor once I'm more certain the calipers are actually the same.


But I'll surely post my progress.

cm60k

Which cast #s you need, for Rotors ID spec..?, or for Brembo's production line..??

ZAYED,,

RacingBrake

Your knowledge in rotor hardness and comparing the rotor strength in brinell hardness scale is truly commendable.

In our decades' brake business we see price comparison, or number of track days a rotor can last "ALL the time" but hardly any discussion on rotor material which is in fact more objective in rotor quality assessment due to it's independent from other components (pads, fluid) or how a driver uses his brake.

Rotor hardness is one of the prime characteristics to determine the quality level of a casting, because for cast iron (which a rotor is made of, not steel) hardness means strength in general. RB has been advocating this casting knowledge to consumers through our website and other forums that are serious in tracking/racing.

For your interest, here is a thread in GTR forum where we presented why a rotor is so important and how a rotor quality is judged.

Racing Brake Technology - A Discussion about the truth of components

How a stronger/stiffer rotor means to brake torque

Procedure in hardness test

Brake product knowledge on RB website:
http://www.racingbrake.com/v/main/product_knowledge.asp

Warren-RB

cm60k

^^^Great choice, don't MISS IT^^^

ZAYED,,

Lioninstreet

Warren, thanks for the kudos. It's a no brainer that RB rotors and pads are top of the line. Most everyone using them will fight you if you try to tell them different.

I was wondering if after reading this thread you had any input on the upgrade I'm considering?

My presumption at this point is that Merc/AMG used the same six pot caliper casting on the pre-facelift SLK55, all SLK55 030's, CLK55, & CLK63 nBS. Based on the application's rotor diameter, they just had Brembo fashion a different caliper bracket to position the rotor properly, then simply fitted the appropriate brake pad.

Getting the casting number off the CLK'63 nBS or SLK55 030 caliper (with the 360x32 rotor) to compare it to the caliper I have using the 340x32 rotor would pretty much nail this down unless you or a colleague already happens to know.

My OE/Brembo 340x32 rotors are service limit so I need to replace soon anyhow. So I want to retrofit in your 360x32 rotor and pads, then cnc my own bracket so it all fits together. Of course, all this is predicated on the availability of a larger brake pad to take advantage of the larger rotor.

So I've attached a sketch of my current pad with dimensions (162mm x 53mm) measured at the centers. Could you outline a rough comparison of OE to your 360x32 street & spirited pads, tell me a bit about the differences between the two RB pads in a street application, and give me the pad dimensions (length and width) of each?


I also found on your web site that unlike Merc, RB has two different ET500 pads for each rotor diameter (PD847-35 for the 340mm and PD1116-35 for the 360mm). Is that difference due to compatibility issues in caliper fitment or simply pad dimension?

I understand that an upgrade like I'm considering will be nothing like going to the larger 8 pot caliper, but for the relatively low cost, I figure I'll still get my money's worth should the calipers be the same.


Your comments and help bring more clarity to all this would sure be appreciated.



ZAYED

The '63 nBS casting number should be located at the bottom front of the caliper. It is visible by looking at the front of the caliper thru the wheels. The left and right side have different numbers.

You can also see where it is on the picture. Left (driver) side is shown.

On my '06 SLK55 n030 with the 340x32 rotor, the six pot caliper numbers are right front 20.8885.06.1a, left front 20.8885.03.1a

cm60k

Why you need this cast #..?!?, it's Brembo's production line code#,

if you need to put 360mm, you can put washer between bracket & caliper(where the allen-key holds the caliper to the bracket),

and you need to grinding about 2-4mm inside the caliper, to clear 2mm in each sides, 30mm VS 32mm thick...

ZAYED,,

Lioninstreet

ZAYED,


You are thinking similar to me.


But I would be concerned about putting in a 10mm washer instead of the bracket. This could be a fail point. If those allen bolts come loose because of the washer being there it could ruin my whole day.


On grinding the caliper, the existing rotor is not 30mm, but is 32mm. So this probably wouldn't be required.

cm60k

No need to afraid about allen-key,

i think your allen bolts around 55-60mm length, you have to use 70-75mm, depend of the washer/+ distance,,

you need to use the same set-up of CLK63, isn't..?, if so,

your exist calipers internals are little smaller than CLK63 calipers, means 32mm in your caliper measurement will be differ than CLK63 calipers, during to the Rotor dia. & bracket thickness..!

ZAYED,,