Brake Caliper Spacers

Anyone have experience with using spacers to mount a brake caliper? 

I found that W221 S550 brake calipers are 4 piston Brembo's and the bolt spacing is the same as the stock 2 piston calipers on my GLK. I grabbed a pair from the junkyard and they do indeed bolt up, but they're about 1/4" spaced out from the knuckle compared to the stock calipers. 

I've seen plenty of bar style adapters out there, but would it be a bad idea to just use two spacers like this:

https://static.summitracing.com/global/images/prod/xlarge/wil-300-15524_xi_xl.jpg

I have no issue making up my own steel bar style one I was just curious if anyone has experience either way. 

The thinner the material between the surfaces you are bolting together the more possibility of flex and possibly long term fatigue. I'd opt for a solid bar with two holes in it.

Has anyone else done this specific mod, and if so did they find out that the front/rear braking was still appropriate?  Is that pad surface area the same and will braking effort change....?

Swapping to 6/8 piston AMG brakes is pretty common (with the bar adapters), but I haven't seen mention of anyone doing a 4 piston swap.

The rotors are 14 inch as opposed to 13 inch, the master cylinder bores are identical between the W221 and X204, so I imagine pedal effort would remain the same right?

peanutpckrupper said:

Swapping to 6/8 piston AMG brakes is pretty common (with the bar adapters), but I haven't seen mention of anyone doing a 4 piston swap.

The rotors are 14 inch as opposed to 13 inch, the master cylinder bores are identical between the W221 and X204, so I imagine pedal effort would remain the same right?

You've got two piston and you are looking at 4 piston?  Need to know the size of the pistons, but I'm fairly sure that with no other changes pedal feel will suffer.  If they are equal in size you're going to twice the area of the piston

Mr_Asa said:

peanutpckrupper said:

Swapping to 6/8 piston AMG brakes is pretty common (with the bar adapters), but I haven't seen mention of anyone doing a 4 piston swap.

The rotors are 14 inch as opposed to 13 inch, the master cylinder bores are identical between the W221 and X204, so I imagine pedal effort would remain the same right?

You've got two piston and you are looking at 4 piston?  Need to know the size of the pistons, but I'm fairly sure that with no other changes pedal feel will suffer.  If they are equal in size you're going to twice the area of the piston

Yes going from 2 to 4. Centric says the pistons for both calipers are 44mm.

I know I've read that going to bigger calipers usually requires a bigger bore master cylinder, but the bore size is the same between the two so I'm a little confused.

In reply to peanutpckrupper :

ah yes, the pedal feel question.  good on you for asking it.  seriously.

"Pedal feel", generally speaking, is how far (pedal travel) and/or how hard (pedal force) you have to push to achieve your desired deceleration.

the answer is "it depends".

larger effective radius from larger diameter rotor, with no other changes, would take less line pressure to make the same torque, so you could say less pedal force and less pedal travel.

higher friction pads, with no other changes, would take less line pressure to make the same torque, so you could say less pedal force and less pedal travel.

calipers with increased piston area, would take less line pressure to make the same torque, so you could say less pedal force. BUT, they probably require more fluid volume, so may have longer travel.

the "it depends" is because we don't know exactly how much each of those parameters is going to change.

then there's the discussion of how much you shifted work from one end of the car to the other, and whether or not that's going to have a detrimental effect on ABS activations near the limits of tire adhesion.

I'm cool with "it depends" for now.

The GLK master cylinder is shared with the C63 AMG which has MUCH bigger calipers than these 4 pistons I'd like to put on so I think it'll be alright. 

I'll have to look at the coding for the ABS module to see if there's anything in there about caliper size. But I think I'm going to carry forward on this, if it works out well this is a super budget friendly brake upgrade for this chassis. 

In reply to peanutpckrupper :

You might be interested in what AngryCorvair does for a living. 

My question would be, why do you think you need "an upgrade."

z31maniac said:

In reply to peanutpckrupper :

You might be interested in what AngryCorvair does for a living. 

My question would be, why do you think you need "an upgrade."

I don't really need to, I didn't need to swap it to a manual transmission or v8 either but I did because I wanted to. 

Another potential way around making a one piece spacer is two spacers, and a one piece joiner bar that goes across the other side.  Volvo did this on my car's Brembos (minus the spacers). 

Found this website called SendCutSend that let me put my measurements in and they'll laser cut the bar adapters I need. It was $30 for two different sets of adapters, a little bit more than the raw aluminum would have cost me but I don't have to do any of the fabrication myself so I'll take it. 

In reply to peanutpckrupper :

$30 is their minimum price, so I do my 2D projects with them in one batch.

When switching from 2-piston sliding calipers to 4-piston fixed calipers of the same piston diameter, all else equal, the pedal force and travel should not change significantly. The main difference here is the <10% leverage increase from the larger diameter rotors, and some additional heat capacity from the heavier rotors.

While they may share the same mounting bolt spacing, they may not just be mislocated axially, but radially as well.

Driven5 said:

While they may share the same mounting bolt spacing, they may not just be mislocated axially, but radially as well.

You are correct.

Generally, if there's a "base" and an "upgrade" brake package for the same car, the knuckle is shared and the caliper is designed to accommodate the larger rotor.  i think (based on the OP's second post) that he got the 4-piston calipers and the larger-diameter rotors, so should be OK radially.

In reply to AngryCorvair (Forum Supporter) :

S-Class vs GLK. Adapters shouldn't be needed if they're using the same uprights.

Driven5 said:

In reply to AngryCorvair (Forum Supporter) :

S-Class vs GLK. Adapters shouldn't be needed if they ran the same uprights.

LOL I can't reed so good.

AngryCorvair (Forum Supporter) said:

Driven5 said:

In reply to AngryCorvair (Forum Supporter) :

S-Class vs GLK. Adapters shouldn't be needed if they ran the same uprights.

LOL I can't reed so good.

also, upon further thought, you're adding the thickness of pistons etc to the outboard side of the rotor, plus you're shifting the caliper outboard by the thickness of your adapters, and i wonder if you're going to have interference between calipers and wheel spokes.

Don't flame for the used rotor I picked this from the junkyard car for test fitting. It all looks fine to my eye, the need for a spacer seems to come from the difference in the caliper mounting ear thickness. 

Stock brakes here

AngryCorvair (Forum Supporter) said:

AngryCorvair (Forum Supporter) said:

Driven5 said:

In reply to AngryCorvair (Forum Supporter) :

S-Class vs GLK. Adapters shouldn't be needed if they ran the same uprights.

LOL I can't reed so good.

also, upon further thought, you're adding the thickness of pistons etc to the outboard side of the rotor, plus you're shifting the caliper outboard by the thickness of your adapters, and i wonder if you're going to have interference between calipers and wheel spokes.

There's just the tiniest bit of scraping on a bit of the mounting bracket that I have no issues with shaving away. 

In reply to peanutpckrupper :

disclaimer: looking at this from my phone. rotor diameter looks the same to me.

AngryCorvair (Forum Supporter) said:

In reply to peanutpckrupper :

disclaimer: looking at this from my phone. rotor diameter looks the same to me.

Yeah it's hard to tell from the pictures, I think having a 17 inch wheel makes the gap a lot less noticeable. 

Pretty happy with the results. The braking distance probably hasn't changed much, but it feels much more responsive. For ~$200 I'd do it again. 

In reply to peanutpckrupper :

if you're on the same tires, and you could (and still can) activate ABS on all four wheels, then your stopping distance most certainly did not change.

In reply to AngryCorvair (Forum Supporter) :

Maybe the first time, what about the third or fifth time?

Disclaimer:  The best thing for brakes IMO is less vehicle weight.  I have a car with super pooper awesome 330mm Brembos and I can make them useless in a mile of country road driving, no matter which pads I've tried.  The car also weighs 4000lb...  the last time I had a car with brakes this overworked, they were 9" solid disks and I had to really be an a-hole with the brakes to do it.  The purple rotors and clouds of brake pad smoke from the wheelwells were neat, though.

Pete. (l33t FS) said:

In reply to AngryCorvair (Forum Supporter) :

Maybe the first time, what about the third or fifth time?

it depends