ATE v Bendix Brake Calipers

[oscar]

Upon close inspection of these calipers there's bugger all difference between them but there's also no use in swapping parts between them either.  Well the O ring inside the bores might be about the only thing that was the same.  I believe there's no difference in operation though.  These two different calipers were the setup on the front of my track car the last time I raced and there was no hint that one was better than the other.

Left ATE, right Bendix.



What is obvious at first glance is the difference with pad retaining clips and springs.   IMO, if there was a choice to be made it comes down to servicing.  Bleeding is the same but when it comes to pad changes the ATE pins and springs are easier and faster to install and remove.  Looking below, one main difference is that the Bendix retaining pins need cotter pins to keep them in place whereas ATE have those split egg shaped bushes that hold the retaining pins frimly in place.  The other main difference is the springs, one convincing one on the ATE and two wire types on the Bendix.  3 bits v 6 bits.  So in this regard I'd prefer the ATEs and is the sole reason I'm putting two ATEs up front again.



I should also mention the ATE calipers have got the trademark "ATE" cast into them as does the Bendix. Probalby the easiest way to tell which is which.  The "60" refers to the bore and piston diameter and every caliper has an "L" or "R" for left and right.



Now for servicing, the pistons were forced out using a bike pump connected to a brake hose.  I couldn't attach the pump directly, in the end I came up with a way that I could hold the pump hose and the brake hose to form an air tight..ish connection.  The next thing I did was to put something (a screwdriver in this case) between the two pistons to limit how far they could pop out.  You can imagine that if one pops out, there will be no air pressure behind the other piston and you'll have to reinsert the first piston by a small amount.  By having this screw driver restriction you'll also stop a piston falling to the floor and damaging it's sliding surface.
When the pistons have almost popped out they're stiff but can be wiggled  out.



The pistons -  very much the same size wise, but you'll notice the the top lip of the ATE has a groove for the dust seal where as the Bendix on the right has it's groove opened up.



The shape of the top of the pistons has a lot to do with the shape of the heatshields as well.  I don't have good pics of the heatshields but looking at this next photo, the ATE's heatshield has an inner cup that's forced into the top of the piston.  Looking very closely at the ATE you'll see the head is recessed at about 2 o'clock and 6 o'clock.  The heatshield here connects its outer ring with the inner cup portion and is the same thickness as the recession thereby not adding any height to the piston nor affecting piston travel during braking.  It's this 2-6 o'clock postion that is related to piston alignment during rebuilding and the 20degree offset of the piston and heatshield (see second pic below).  If aligned properly, this recessed part of the piston and thicker part of the heatshield will be perpendicular and facing the direction of the forward turning brake disc.
The Bendix's heatshield is simply more like a donut and sits around the top lip of the piston, clamping the rubber seal down in the process.  The advantage here is that no piston alignment is needed.  The heatshield only needs to have it's inner tag aligned.  the tag is on both heatshields and holds a loose pad from moving forward,




Here's the relevant reseal kits and part numbers

ATE's, front seals at top of the photo
front -  000 586 74 42
rear  -  001 586 73 43


Bendix, front seals are at the top of the photo
front - 001 586 11 42
rear  - 001 586 01 42


I gave all parts a methylated spirits bath.  Firstly the calipers and gave them a high pressure hose wash afterwards.  Then the pstons and calipers separately.  I used autosol to clean the pistons up and although theres some pitting around the lip there the pistons sliding surfaces were without faults.


I also used some autosol on the bores but it's a real pain to get out again.  I had to use solvents to help then more metho baths. This pic shows some build up rings of crud that was hard to get rid of.  Fingernails ended up working the best.


The grease I used during reassembly.  Two days after I put the front calipers together I found that PBR stuff at a repco shop that everyone else has been recommending.  With this grease I covered all the rubber parts, bores, and sliding surfaces of the pistons.


Alignment of the pistons - at this stage I was getting greasy as and couldn't put parts down to pick up the camera.  Basically I attached the dust seal then loosely sat the heatshield on the piston and aligned one of the 2-6 o'clock recesses of the piston with the heatshield cutout.  I then sat the piston just into the top of the bore so I could rotate the piston slightly to get the right alignment before pushing the piston all the way in.  Once in, the piston is impossible to turn without using a plier type tool that ATE recommends.


Apart from using fingers I used this hammer and flat bar to help seat the piston in a fully inserted position.  Just tapped away is all in different spots but I suppose you should use something softer like wood.


But they all came together and now back on the car.

Still to come, reseal the Bendix front caliper and compare a rear ATE v Bendix.  I'm guessing apart from size the two will mirror the fronts in likenesses and differences.

[TJ 450]

Awesome post, Oscar.

Those Bendix calipers appear the same as the ones I have off Nathan's W126 500SEL. I will be installing them on my 6.9 on the premise "newer is better". My 6.9 currently has ATE front calipers. The Bendixes will be re-sealed beforehand.
It does appear that they are basically the same, just different manufacturers.

Tim

[oscar]

Thanks man.  You'll notice too  that I didn't get round to painting them either. I wanted to.  I used paint stripper on the bendix one but it didn't work to well on the ATEs.  I also bought ColdGal spray and acetone but ditched the idea after getting greasy fingerprints all over them whilst reassembling them. 

I was surprised at the state of the rear calipers.  Inside they were real cruddy with a lot of difficult to remove deposits.  No pics up yet though, I'll wait till I find the bendix rears.  One interesting bit is that the ATE rears do have that recess in the piston head like the fronts to accomodate a heatshield that doesn't come with the kits.  So I don't know whether you can get those shields for the rears still.

[craigb]

that's great having the L & R cast in and something to keep in mind. I know this sounds really stupid but I have helped someone on ozbenz with this - the bleed nipple needs to be at the top of the caliper or you will never get them bled because it will retain a pocket of air, but of course if you swap sides accidentally with calipers you may not notice and then start pulling your hair out because you can't get them to bleed. I made the mistake...... once! I am sensitised to it now but that simple casting L or R will save any confusion.

[Gerard]

Just did this job on my 450.  I used this post for reference, thank you very much.  

I have the Bendix calipers and did one set of seals no problem and refitted it to the car.  I did notice some "dents" on the surface of the pistons but thought no more about it.  I thought it was damage from a previous owner or hammer marks...etc.  I paid no attention to piston alignment.

But when I dismantled the second caliper, I had a good look before popping the pistons, and those "dents" werent dents at all, its a machined cut and they were aligned the same way as the 20degree indents on the ATE caliper.
So I changed the seals etc and cleaned them down and replaced with the indents at 20degrees, 1 line pointing to the hub centre, thus creating a birdsmouth into the rotor direction.
I then pulled the other caliper off again, and realigned the pistons in that too.

I looked at the pics here, but I cant see any cuts on the surface of the Bendix pistons.  But part of the piston is out of focus so its hard to tell.    I didn't measure the indent, but I guess its about 0.1mm deep, and is about 120 degrees, similar to the ATE indents but much shallower.  Its to stop squeal I gather.  I wonder does it prevent uneven force across the pad too, giving better pad wear?
So if that indent is in the pistons, I'd say it would be better to align it like the ATE.
Best regards
Gerard

EDIT:
I notice in the 10th pic, you can just make out the indent on the Bendix piston

[WGB]

Great photos Ocar and thankyou for the effort associated with posting them.

The cutouts  on the pistons are there to put uneven pressure on the pads to prevent squeal and so their alignment is critical but in mine it was well covered in the literature that was enclosed with  the kit as well as the 116 workshop manual.

I had the PBR grease but after the first piston I just used brake fluid and the pistons seemed to go back in quite well and that way I was happier that no foreign material of any kind Entered the system. I even used brake fluid as the lubricant for some very light 1300 grade wet and dry to clean the pistons and bores.

There's been a lot of discussion about initial poor  pedal feel from S-class and Koan which has been
suggested is caused by poor initial lubrication of the piston seals causing them to back off after the application of the brakes when new. I was a little unhappy with my pedal feel initially but after a couple of weeks driving the pedal hardened up nicely.

To push the pistons back into the bore I used a pair of old almost bald pads and started them with a screw driver between the pads to start them and then individually used vice grips with the back of the calliper and the pad as the two pressure points. They go in reasonably easily so long as you square the piston up into it's respective bore ( I was careful not to mix them up as I believe they are originally matched in some way ) and  be careful with the first bit of the push.

The rears ( mine again Were ATE ) are similar but much smaller and the space to get both pistons out is much more limited ( thinner non-ventilated disc) but there is sufficient space to get them both out together but you will have to put them back individually - hence using an old pad and vice grips to force them back in.

Also be careful at the rear as that's where I turned the flats off One of my brake pipes. Three seems be generally more corrosion at the rears as well.

Bill