Hello, just though id share all the information I have on doing this swap as I seem to have found all the issues and have found methods to overcome all of them so we can have awesome brembo stopping power for around Ł500~ish instead of having to pay Ł3000 for an upgrade kit.
The stock brakes on the R170 are okay I guess, they stop it pretty good from medium speed but leave a bit to be desired. I have had issues with them getting very hot and loosing braking force.
They also look awful and don’t fill up the wheels and give the stock SLK a pretty pathetic look I’m my opinion.
After the swap obviously the car has much more effective braking and brake cooling, I think the car feels more balanced with slightly more front brake bias because the car naturally isn’t that quick to turn in so the increased front braking compared to the rear helps to tuck it into a corner.
Parts you will need to buy. I can only document the parts used for my car but because of different rims etc you might need different sized parts so before buying make sure you measure things I’ll later mention before buying.
1: W220 4pot brembo brake front callipers. Mine came from a W220 S430 or S500. Make sure you know what car they came from because there are callipers for 330mm disks and 345 mm disks.
The part number is 20704704 for the W220 330mm Calipers. Make sure you know what model car they came from and ensure you know they are for 330mm disks. If you get them from an S430/500 the bleed nipples will end up on top making the bleeding process easier later.
2. Brake disks. Get your callipers first, once you know what model they came from, for me it was an S430/500, google disks for that exact model and buy a set. For my S430/500 callipers I used these: https://rover.ebay.com/rover/0/0/0?m...2F323794431477
The thickness new should be 32mm
3. brake pads: Brand does not matter, I used EBC redstuff. After obtaining the exact model your callipers and disks come from enter the details into your favourite car parts site and get some pads. For my S430 callipers they were 119x71x17mm EBC redstuff.
4. Brake fluid. I got 2 litres of Dot4 fluid. Only used 1/5th of a litre to bleed the new callipers so 2 litres was probably too much but better be safe than sorry.
5. New Caliper mounting bolts. You will need some extended bolts. They must be M12x1.5 x50-70mm so we can cut them to exact length later. THEY MUST BE 10.9 high tensile steel. Do not just buy any old bolt they HAVE to be 10.9 steel or you run the risk of them braking.
6.4x spacers. In order to mount the w220 callipers centrally to the rotor we must use some stainless steel spacers. I needed a 6mm spacer for each bolt in between the wheel hub and Caliper.. They must be stainless steel, outside diameter 25mm, internal diameter M12 clearance and 6mm thick but before buying them you should do a test fit and measure the gap to ensure you get the correct spacing ill go over his later. DO NOT USE WASHERS, you must use the correct sized stainless spacers. Washers are not flat and will the bolt will come loose over time.
7 Wheel spacers. The larger 4 pot Caliper did not clean the inner face of my rims. I have the AMG 5 spoke 17” rims so I can only comment on the fitment for these rims. I used a set of 15mm spacers on the front and 10mm on the rear. This is the most you can get away with without getting bad rubbing issues. (The car feel a much more stable with these track width increases too. With these spacers, slight rub on extreme bumps at speed) The problem with the wheel spacer for me was they did not fit. I got the correct size spacers but ended up having to use a family members lathe to take a tiny bit of material off because they wouldn’t seat properly out of the box. The spacer would not clear the factory wheel bearing dust covers so using a family members lathe I made new dust covers that integrate with the wheel spacers, pics included lower down. This step really depends on what rims you have. Once you have your Caliper centred and mounted you can test the wheel and see how much clearance you have to gain for the wheel to fit on and there fore how thick of a wheel spacer you must buy. You must get longer wheel bolts for the spacers. The length of the thread for the new bolts will be the original length + the thickness of the wheel spacer. Make sure you get the correct type of nut for your rim aswell. Dome vs 45 chamfer.
Id suggest you buy the callipers, bolts, disks first then do a test fit before getting both the spacers required.
Mount the new 330mm disk on the wheel hub then mount The new callipers with the long bolts, don’t tighten the bolts just screw them in a bit so you can slide the Caliper back and fourth to centre the Caliper over the disk so you can measure the size needed for the spacer. I used a set digital callipers to make sure the gap in between the pistons and disk is the same either side of the disk (Ensure all 4 pistons are fully retracted). With the Caliper in position and centred measure the gap in between the wheel hub and Caliper. This is the size spacer you will need. For me it was 6mm for my W220 S430/500 set up. Now the Caliper has a set position you can now see how much clearance you need to gain between the wheels and callipers so you can measure and buy your wheel spacers as described earlier.
Use the digital callipers to measure the distance the bolt will have to travel through. (Hub+Spacer+Caliper) for me it was (18+6+16)mm ish I can’t remember exactly but I had to cut my bolts to 41mm for my setup. I used an angle grinder to cut them and a bench grinder to remove the burr. Make sure the thread still works.
From now on it’s a straight brake swap + installation of wheel spacers, all the parts should fit together if you’ve done your measuring and test fitting correctly. You will need to bend the brake shield back slightly at its highest point 6 o’clock ish on the shield or it will rub and made baaaaad noises.
For the Caliper bolt torque I used the W220 spec which was something like 115nm, just find the torque spec from whatever model you got the callipers form and use loctite on the threads.
Front tyres wheels, if your running 205/225 front tyres you might have problems with grip. I run 235 Michelin pilot sports on the front and they struggle to deal with these brakes so if your thinking about this and make sure you have at least 225 front tyres with a good brand of tyre.
I think I included everything here but if you have anymore questions ask away. I’m also not responsible if you have a brake failure and crash I’m just sharing my experience on how I did this.