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I decided to stick with the 6/4 brake swap on my C55 and dug into it a little bit. The threads seem to be a mess with half-thought answers.
Yes, the calipers and rotors fit. Yes, the wheels fit.
When I started to do my swap the other day I found that the rear brake hose was uncomfortably short. Yes, it will fit. However, at full suspension droop (like car on a lift for maintenance) the hoses are stretched TIGHT. They were so tight that I pulled everything back off and stuffed the stock rear brakes back on it and didn't mess with the fronts. I need to find a longer hose to make me feel comfortable with this swap. The 221 rear hose is 2 inches longer than stock but that's kind of excessive.
The worst part is that I bought the StopTech braided hoses for the C55 and they're almost an inch shorter than stock.
I need to contact StopTech and see what hoses they've got available. I bought these through Rock Auto so maybe I can get a refund despite the fact that they have had brake fluid in them.
If you knew me I'd consider that an insulting remark.
I've done a fair number of brake swaps and even a few complete brake system installations on race cars.
Yes, the calipers were on correctly. Hoses below the bleeders. No rocket science there.
It makes no difference that the part number for the hoses on a 171 & 203 are the same. They are different chassis and have different brake hard line mounting points.
Successful auto engineers save money by using the same parts across different models. In this case, the hard line has to be unique to the 171 so it makes sense to terminate it at a point that would accommodate an existing hose.
Last edited by feets; Jul 28, 2018 at 07:14 PM.
Reason: Stinkin autocorrect
Okay, let's try this again.
The brake hose is roughly 12" long.
Each chassis has a different hard line.
Each chassis has a different caliper mount.
Design the caliper mount for the desired result.
Run the brake hose up from the caliper.
Can the hard line end at a convenience place to use the same hose? If so, use it and save money.
Mix and match components from different cars and the measurements may not add up.
The 4 piston caliper moves the brake hose down in relation to the mount. The SLK hard line was designed with this in mind. It runs lower on the car than the hard line on the 203.
Move the brake hose down on the 203 and it won't reach the hard line.
Okay, it does reach but is TIGHT at full suspension extension. That stresses the hose and leads to failure.
Have you ever experienced hydraulic brake failure at 160 mph? That's how people die.
I'm not trying to be arrogant.
To me, the things I pointed out are pretty basic.
Maybe it's my background in manufacturing as well as being a machinist that makes me think differently than others when it comes to these kind of things.
This thread was meant to be informative, not a plea for help. The others who have done this swap need to check their brake hoses at full suspension droop.
I decided to stick with the 6/4 brake swap on my C55 and dug into it a little bit. The threads seem to be a mess with half-thought answers.
Yes, the calipers and rotors fit. Yes, the wheels fit.
When I started to do my swap the other day I found that the rear brake hose was uncomfortably short. Yes, it will fit. However, at full suspension droop (like car on a lift for maintenance) the hoses are stretched TIGHT. They were so tight that I pulled everything back off and stuffed the stock rear brakes back on it and didn't mess with the fronts. I need to find a longer hose to make me feel comfortable with this swap. The 221 rear hose is 2 inches longer than stock but that's kind of excessive.
The worst part is that I bought the StopTech braided hoses for the C55 and they're almost an inch shorter than stock.
I need to contact StopTech and see what hoses they've got available. I bought these through Rock Auto so maybe I can get a refund despite the fact that they have had brake fluid in them.
The W203/W209/W171 all use the same rear brake hose regardless of 2 or 4 piston, yes its been superseded and I understand how the parts logistic works with mfg's.
I've done two of these conversions and the only thing that needs to be done is either buy the correct dust shields for the front and rear or correctly trim them which I had templates that I got from the correct shields.
I even used new oem brake lines when I did my swap wit no issues of when the car is at full droop use oem rubber A1714280035
I grabbed a pair of StopTech stainless braided brake lines for an SL550. They're about 1" longer than stock.
After work today I threw the car on a lift and knocked out the rear brake swap. Those screaming-deal Raybestos rotors, StopTech hoses, and SLK55 calipers are on the car.
I ran into a little hitch when I dropped the car and tried to leave. The left side brake backing plate was rubbing the rotor along the perimeter. It makes an incredible amount of noise even at a walking speed.
There was no issue when I did the right side first so I didn't expect it on the left.
I grabbed a long pry bar, poked it straight in through an opening in the wheel, and pushed the backing plate away from the rotor in four different places.
That solved the problem and the new brakes work fine even with the stock C55 pieces up front.
One of these days I'll do the fronts, too. The seller had just done front pads and rotors before I bought the car and they only have 17,000 miles on them. No good reason to ditch them at the moment.
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