6.3 Brake Caliper Features

[Styria]

I think most of us would be aware of how the 6.3 came into being. The story of how 'young' Waxenberger virtually 'cobbled together' the initial car for evaluation by Rudi Uhlenhaut (forgotten his title but he was the one to give the go ahead for production purposes) to demonstrate what could be achieved by dropping the 6.3 engine into an air suspended 300 SEL chassis.

All good reading, and part of the folklore. What you don't always hear and read about, is some of the other 'hidden' features that can be associated with 6.3's. So, please come to 'topklasse' and enrichen your knowledge of some matters seen and unseen. One of those matters relates to the front and rear brakes.

Rear calipers and disc rotors - Mercedes utilized ventilated rear calipers for the 1968 and 1969 models only. After that ? I guess for reasons of economy, they switched to solid rotors. There were other cost cutting measures as well (post 1968 and 1969), but they are not covered within the guidelines of this thread. There are two other aspects I find intriguing. Firstly, the method of securing the calipers to the rear hub. This is achieved by bolting the calipers to threaded and welded nuts that are part of the backing plate - in other words, there are no threaded castings on the hubs themselves. The result is that fairly 'flimsy' components provide the locating means on components that can be subject to extreme forces. I think it is correct to say that in 90% of cases the 'welded nut' has broken away from the backing plate.

Furthermore, what is generally not realized is that the calipers are 'shimmed' to achieve the ideal 'central' location - if they are not centralized, the brakes will obviously still work, but one piston will portrude further from its housing in the caliper than its corresponding mate on the other side.

Fronts ? Well, obviously MB switched to ventilated rotors which necessitated the use of calipers with larger 'claws' - in other words, the Company still used the existing caliper design, but spaced out the claws by utilizing the use of spacers. Mind you, everything still works well, but one could question certain aspects of those modifications. Regards Styria

 

[abl567]

I think most of us would be aware of how the 6.3 came into being. The story of how 'young' Waxenberger virtually 'cobbled together' the initial car for evaluation by Rudi Uhlenhaut (forgotten his title but he was the one to give the go ahead for production purposes) to demonstrate what could be achieved by dropping the 6.3 engine into an air suspended 300 SEL chassis.

All good reading, and part of the folklore. What you don't always hear and read about, is some of the other 'hidden' features that can be associated with 6.3's. So, please come to 'topklasse' and enrichen your knowledge of some matters seen and unseen. One of those matters relates to the front and rear brakes.

Rear calipers and disc rotors - Mercedes utilized ventilated rear calipers for the 1968 and 1969 models only. After that ? I guess for reasons of economy, they switched to solid rotors. There were other cost cutting measures as well (post 1968 and 1969), but they are not covered within the guidelines of this thread. There are two other aspects I find intriguing. Firstly, the method of securing the calipers to the rear hub. This is achieved by bolting the calipers to threaded and welded nuts that are part of the backing plate - in other words, there are no threaded castings on the hubs themselves. The result is that fairly 'flimsy' components provide the locating means on components that can be subject to extreme forces. I think it is correct to say that in 90% of cases the 'welded nut' has broken away from the backing plate.

Furthermore, what is generally not realized is that the calipers are 'shimmed' to achieve the ideal 'central' location - if they are not centralized, the brakes will obviously still work, but one piston will portrude further from its housing in the caliper than its corresponding mate on the other side.

Fronts ? Well, obviously MB switched to ventilated rotors which necessitated the use of calipers with larger 'claws' - in other words, the Company still used the existing caliper design, but spaced out the claws by utilizing the use of spacers. Mind you, everything still works well, but one could question certain aspects of those modifications. Regards Styria

It's taken me hours to come to the defence of the Six 3, so here goes

109 chassis cars use a floating rear caliper set up, the caliper can rotate around the axle tube to a small degree restricted by a lever bolted to the chassis forward of the axle via rubber bushings. The result is that under brakes the couple moment created by the reactive force of the pads against the disc is transfered to the rear chassis of the car reducing lift at the rear and the effect of dive at the front. It also allows you to gently load the rear axle for burnouts, no, rapid take offs

The calipers are bolted to the lever and the bearing housing in such a way as to allow limited axial and lateral movement of the caliper relative to the axle tube, not the disc, and locked to the assembly with a locking tab, figure number 84 in the parts manual. Part number 109 994 00 32. The bolts that hold the caliper to the lever need some play to stop the caliper binding against the disc as the axle moves through its travel. Remember the caliper is also attached to the chassis floor.

108 steel spring chassis cars are different, the calipers bolt hard to the axle tubes as the crude ride of the springs hides the dive

 

[Styria]

Hi abl567, this is all good stuff, and whilst it has taken you a number of hours to come up with not only a very good reply, but also some very sound explanations, it will probably take me twenty four hours to add further input to the thread - I have to 'go look and see' !

Just to add a little more at this stage, the rear caliper on models with the ventilated rotors are in fact spaced apart by the insertion of the special spacers previously referred to. Thus, can one consider this method a bit of "make-shift" ? Regards Styria