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030 Big Brake Rotor Upgrade To 360mm Now Doable!

15K views 38 replies 11 participants last post by  hwheeler 
#1 · (Edited by Moderator)
Ive been watching the SLKW threads and finally, the aftermarket is now starting to fill out the 340mm and 360mm high performance full floating brake rotors used on the front of the '55.

For those of us with the 6 pot caliper standard (as I have on my '06) and no 030 option, we have been limited to a 340mm brake rotor. While all model year 171's with 030 have the exact same six pot caliper as the early '55's, the 030 gets a larger 360mm rotor.

Later '55's without the 030 got a four pot calipers with a smaller rotor as well so if you've been wondering about an upgrade, you will want to read on.

So the only difference between the 030 six pot caliper and the early '55 six pot caliper is a bracket that moves the caliper out 10mm. That's all it takes to properly space for the larger 030 rotor. Of course Brembo won't offer the bracket by itself and neither does Merc. So unless I buy the complete 030 brake caliper set (ka-ching), I'm stuck.

And for those who would upgrade to the 6 pot calipers, the ones used on the 340mm rotor are more readily available both new and used since they are more common on other models besides the early '55. The caliper that fits the 360mm rotor, not so common.

One suggested machining up a set of 10mm spacers to install between the 340mm caliper bracket and the caliper to space it further out. But using spacers, the caliper bolts could potentially loosen. And if that happens it that could ruin my whole day.

So while my '55 is up in the air for a few other goodies, a buddy of mine is CNC machining me up set of brackets out of 4043 moly steel to duplicate the ones found on the 030. That will move the caliper out with no worries about spacers coming loose.

And with the 360mm Brembo rotors on Amazon for about $600 a pair (instead of the $1400 the stealership wants), this upgrade makes perfect sense. Especially considering my 340mm rotors are toast.

That said, it seems that the OE/Brembo rotors are about 2/3's as hard as the better aftermarket brands.

The Brembo is about 145 on the Brinell hardness scale. The $1000 Stoptech rotors are around 171. The $1300 RacingBrake rotors tested were 196 and 193, so about 34% harder than OE and 14% harder than Stoptech. That explains why my OE rotors were toast at 40k miles.

Harder Brinell translates into longer life, but potentially twice the expense. I'll post more once the brackets are done.
 
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#2 ·
Attached is a visual comparison of the caliper brackets showing the difference between the 340mm six pot and 360mm six pot caliper.

The 340mm caliper is standard on '05-'07 r171 SLK55 non030 and the '05-'06 c209/a209 CLK55.

The lower production 360mm caliper is standard on the '05-'11 r171 SLK55 w/030, '06-08 r171 SLK black, and the '07-'08 c209/a209 CLK63 (non Black).
 

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#3 ·
I think you will find that the bracket you seek might be too long for the 340 caliper.

Bear in mind that the calipers are properly shaped to suit a specific disc. I have not converted a 340 caliper to fit a 360 disc, but from what I know of Brembo styles, each caliper is radiused to suit.

I do not follow that a properly machined spacer will allow the caliper bolts to loosen. Well machined spacers and suitable hi tensile bolts of the correct length will extend the caliper as you wish, but I am just not sure it will look right, and it may not use the full contact area of the 360 disc. I might be wrong and it will look perfectly OK, so I am interested in what you end up doing...
 
#4 ·
From all the research I've done on this the two calipers housing castings are the same. Of course the pads are shaped slightly different due to the larger rotor radius.

It also would not surprise me if the casting for the 8pot 360x36 caliper is also the same as the 390x36 caliper.

What I couldn't get past was having spacers. I don't want to trust my brake system to that. Most of the guys doing big brake conversions stick with machining a custom bracket instead of going the spacer route.

Sure would appreciate it if anyone could offer some experience.
 
#5 ·
Sorry, but the 340 casting is different to the 360 which in turn is [totally] different to the 390!

It has to be different. The pistons are positioned such that they hit the centre of the pads for optimum performance. If the 340 were the same, it means that the centre piston will be hitting the 360 pad high and the outer pistons hitting the pads low.

There is another technical problem, well, it might be a problem - as I have never seen anyone mismatch calipers to discs (which is why I think you will not find anyone with experience of doing so..) is that by putting a pad from a 340 onto a 360, the whole profile will change causing in fact an extra leading edge on the pad where the radius falls away. This new leading edge should be chamfered which in turn will reduce the pad surface contact area…

I looked at my 360s last night with your situation in mind. Using the clearance of the disc in the caliper, and am pretty sure the leading and trailing points of the 340 caliper will foul the 360 disc, if not, it will be pretty close! See this on a rough drawing I attachj showing the 340 overlap on the 360 disc.

The more I think about it, it will just not work I am afraid.
 

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#6 ·
Hal,

So I saw your sketch and understand the principal you are seeking to convey about the piston location.

What I don't see is the leading edge problem. Each piston would be pushing on a 360mm pad designed for the 360mm rotor they are pushing on.

Once again, all the material I found states the two caliper castings are the same. With that said I do not have the ability to compare the two directly (unless someone with an 030 lives down her is Sfla and wants to meet me at my indy's shop).

So I was thinking, you mentioned that you have the 360mm caliper. It would certainly put a nail in the conjecture if we could compare the casting numbers. Can you see any? If so I'll compare it to my 340's.
 
#7 ·
Before you think about piston location, you need to be convinced that the 340 and 360 units are different. I thought I had an old 360 caliper, but looking for it just now, think I must have thrown it away. No good giving you numbers off the one on the SLK as it is not a Brembo, but the principle is the same, whether Brembo, AP, Wilwood, Tarox etc: each caliper is made to suit a certain disc and cannot be interchanged for larger or smaller.

See from the photo of mine how the caliper radius lines follow the disc radius line perfectly. Now if you exchanged the caliper for one suited to a 340 disc, it would not be the same - it would be as my scale drawing above, and as the caliper is quite long and the clerance quite small, the end posts will hit the disc.

As to the new trailing edge you create, go back to my drawing and super impose my dotted line inside the 360 disc line and you will have a small arc either side of centre - ie the radius line of the 340 pad (as you cannot fit a 360 pad into a 340 caliper) is against the rotation of the disc and becomes a leading edge.

I am sorry, but it just cannot be done. I am not trying to be a damp squib on your plans, but I know enough about braking systems to warn you off making any costly mistakes buying in discs that once fitted, you might not be able to get your money back.

Are your 340 calipers off the car at present? Could you take them off for an hour or so? If yes, then make a cardboard template of a 360mm disc and place it inside your caliper and you will see what I mean in my drawing above.
 

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#8 ·
EPC shows different part numbers for the calipers too

A003 420 68 83 (right)
A003 420 67 83 (left)
A005 420 50 20 (pads) and replaced by A005 420 39 20

For the 030 package

And for the 'normal' 340mm package using my VIN

A003 420 88 83 (right)
A003 420 47 83 (left)
A005 420 39 20 (pads)
 
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#9 ·
@Hal,

I do have a caliper off the car and could try the template method you suggested.

@sean,

Are those epic numbers part numbers for the caliper/bracket assembly or just the caliper??

Remember that the bracket is sold as part of the caliper assembly, so if those #'s source the std. and 030 caliper/bracket assembly, they would naturally be different numbers.

On another note, I do have the casting number off of a 340mm caliper. It is 20.8885.031a. If the 030 has the same casting number we probably have our answer.

Anyone with an 030 able to look thru their wheels and see the casting number on the caliper?

My standard caliper has the casting number located on the front facing side near the bottom when viewing the left (USA driver) side.
 
#11 ·
@Hal,

I think you are confusing the CLK63 black 6 pot caliper that matches a 360x36 rotor with the SLK55 030/CLK63 6 pot caliper that matches a 360x32 rotor.

If I can first confirm that both calipers have the same casting number, I will be satisfied that moving the std. '05-'06 SLK55 caliper outward 10mm with a CNC'd bracket is a safe bet.

If the casting is the same, duplicating the 030 caliper bracket's caliper position will allow me replace my worn 340mm rotor mb rotor with the larger 360mm brembo at a substantial cost savings.

As far as upgrading to the harder racing brake rotor, I've got to get past little issue of the caliper casting being the same between models first. The casting number for my std. 340mm caliper is below from the bottom front face of the caliper.
 

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#12 ·
My one mistake - yes the CLK63 uses a 32mm disc. It is the only 030 model that does. Now, all 360mm discs are 36mm. So when you do decide to waste your money, ensure you order CLK discs.

Listen, I will now drop out of this thread. It is soon going to get silly. You asked the question is using 340mm calipers on a 360mm disc doable. I have answered no and that calipers are NOT interchangeable, but you are determined to say it is, so let me wish you the best of luck on your procedure from here. If you want any sensible help though, please ask.
 
#13 ·
@Hal,

Don't misunderstand my desire to press forward and explore this further as a rejection of your thoughts and opinion. Your concern, especially regarding the inside radius of the caliper vs the outside radius of the rotor is duly noted.

My thinking is that the 030's brake pad fitment, rotor, and piston contact using the std six pot caliper is the real concern. They are what is doing the work. The pads radius has to be properly positioned over the rotor and have 100% rotor contact. The piston positions against the back of the pad has to be correct. With the caliper, it is more of a rotor clearance and a piston location concern. And of course the new caliper bracket has to put the caliper in the correct location.

Should I luck out and the caliper between the two models use the same casting, then the radius situation you raised becomes a non issue. Then I can work thru the pad and piston location questions. But those are also likely to be non issues too.

I overlooked seeking to match up the caliper casting numbers at the beginning of this upgrade project. So thank you for bringing up your concerns.
 
#14 ·
Onc step closer to an answer:

Brake pads are the same on the std '05-'07 6 pot and 030 six pot caliper per thie earlier post by etyu using the EPIC and vin's for the separate cars:

http://www.slkworld.com/185442-post69.html

Still hoping to find someone with an 030 caliper who can easily see the left and right casting number thru the wheel...

If those are the same, I might just go ahead and make up a set of the C-shape brake caliper brackets, get a set of the 360mm rotors, and give it a shot.
 
#15 ·
Now here is a real curve to the large rotor upgrade controversy.

Those who have been on this forum for a while surely remember DansSlk. Based in GB, he was a regular contributor for at least 5 years and was pretty much the resident MB dealer tech. Sadly he left the forum several years ago.

In this thread from 2007 he stated that he upgraded to the larger rotor on his 2005 '55 by simply bolting the 360x32 rotor on. No caliper change at all!

http://www.slkworld.com/ask-dansslk/3362-slk55-black-series-brakes-vs-std-slk55.html


Problem is, looking at the installed standard 6 pot caliper, just don't see there is enough room for the larger rotor to fit inside the caliper without the clearance created by the C-shaped 030 caliper bracket.
 
#18 ·
The 360mm rotor mod has taken an interesting twist in direction since finding DansSLK's post stating the larger rotor would bolt on.

While my '55 remains in the air due to shipping damage to the re-chroming of my Asanti wheel centers (thank God for insurance), it did give me the opportunity to measure the clearance between the rotor and caliper.

Turns out there is .250" (6.35mm) of clearance between the rotor and caliper.

And if need be, moving the caliper outward is a doable solution as the same .250" in clearance exists at the bottom of the caliper. An increase in caliper radius does not cause an interference problem due to differing rotor radii. I am still seeking to compare the caliper casting numbers to an 030 just to be on the safe side.

Where an issue becomes apparent however, that is unless my 7th grade geometry is wrong, is that for the 360mm rotor to be a direct replacement and clear the caliper there needs to be more than .394" (10mm) in existing caliper clearance between it and the existing 340mm rotor. There is .250".

This poses a problem for a direct bolt in solution as stated in the thread by DansSLK. Perhaps an email out to Dan is in order.

Thanks for the tip and contact information yuri.
 

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#20 ·
Doing a brake upgrade is not about the looks, but about stopping. My 340's are past turning and I can feel a bit shake in the steering wheel when I hit the brakes hard. So buying disks are actually right around the corner for me.

But I am not 100% convinced yet this will work, only about 85%. It will take the 030 caliper casting numbers and maybe a call to Brembo to bring me over 90%. Then I'll drop the coin on having the brackets CNC'd and buy the rotors. I priced the brackets and it look like they will be $350 - $375 each to have a pair of them made including the engineering drawings. Make 5 sets and they would drop to about $250 each, possibly even less.

But unless I can physically compare the two calipers before making brackets, I don't want to make more than two until I'm driving on them no worries.

On another note, have a look at this caliper being used by Brembo on a 380x32 SLK brake conversion, albeit overpriced for what it is. It's casting sure looks similar to the AMG casting.

Brembo Gran Turismo Big Brake Kit - Kings Performance - Let the Kings of the street build it for you. Call us today : 321-235-2699

380x32 brakes really sounds nice, and Brembo has a pn# for that disk at about $375 ea. now. So I'm still researching and did send an email out to DansSLK asking he clarify what he did to get the 360mm disk installed...
 
#22 · (Edited)
Since my original post, I have confirmed from several sources that the 6 pot front brake caliper on the r171 '05-'07 '55 non-030 and all the r171 030's are the same caliper casting.

This is amazing news considering the concern that our 6 pot caliper was not useable for a larger brake rotor upgrade.




The only difference between the r171 6 pot calipers is the mounting bracket. So an upgrade from the 340mm rotor to the 360mm rotor is easily doable without concern. And non-030 caliper will also fit the 030 brake pad.

My CNC guy told me that it will cost $400 for the drafting/programming and $240 per piece to make a handful of brackets.

Depending on interest, a group buy would likely lower the per piece price.

This is amazing news considering the price of the 360mm rotor is coming down from the outrageous stealership cost.

In addition, after discussions with RacingBrake, we can also consider an upgrade that is even more interesting and radical.

Their upgrade would consist of their 380mm X 32mm GT-R Nismo rotor, a custom made hat, their 165mm X 65mm brake pads, a new set a brackets to fit it all together, and longer brake hoses. Cost has so far been estimated at under $1900.

This upgrade would be similar to an existing kit they offer using the larger 6 pot caliper standard on the E63 and C63 class. It upgrades from 360mm to a 390mm rotor (like std C63 to BS), or older E63 to newer E63 while retaining the use of original calipers.

And again a group buy would also lower the per piece price.

Problem is now I have to decide which direction to go in since my 340mm rotors are not far from being trash...
 
#26 ·
Since my original post, I have confirmed from several sources that the 6 pot front brake caliper on the r171 '05-'07 '55 non-030 and all the r171 030's are the same caliper casting.

This is amazing news considering the concern that our 6 pot caliper was not useable for a larger brake rotor upgrade.

.....


The only difference between the r171 6 pot calipers is the mounting bracket. So an upgrade from the 340mm rotor to the 360mm rotor is easily doable without concern. And non-030 caliper will also fit the 030 brake pad.

...
This is true.

One may be able to fit the 030 360mm brake disc on a non-performance package 6-pot front brake caliper but the stopping power will be the same unless one also changes the mounting bracket (of the brake calipers) to the same specification as that of the performance package or 030. The mounting bracket is about 10mm further out and thus gives more leverage or better performance when braking.
 
#24 ·
I have yet to contact Brembo and find out if they are really selling their 360mm x 32mm rotors on Amazon or if it is just a fishing expedition.

In either case RacingBrake will build the 380mm x 32mm rotor upgrade for our existing 6 pot caliper. But they state it might not fit an 18" wheel.
 
#27 ·
Reviving an old thread I started a while back.

During this time I was able to confirm the three pot high performance AMG/Brembo front caliper that fits the installed 32mm wide rotors are actually the same casting ('05-'07 non-030 and the '05-'11 030). The part number difference is due to the fitment of only the caliper bracket that differentiates the part between the 340mm standard rotor and a 360mm 030 rotor fitment.

Since the larger 030 rotor is now aftermarket available at a (more reasonable?) cost than from the stealership, I'm taking the plunge and having the 030 caliper bracket CNC'd for me. This to upgrade my non-030 6 pot brakes on my '06.

A friend is letting me use his left and right 030 bracket as a template to make direct copies. Let's see how it goes.
 
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