MB w123's ) all have solid rotors. I've had two cars that had small issues with the calipers sticking and then the fluid "boiled" and I had excessive brake fading. That can be scary. I've found out that the first gen w126 (280se/l, 380se/l and 500se/lEDIT- and on the 300sd) calipers and rotors can be swapped directly into a w123- it's plug and play. You must swap both the calipers AND rotors. You will not get more braking power but the w126 is vented and the w123 is solid- so you will have more cooling- less chance of brake fading....

Here is the w123 rotor



and here is the w126 rotor
Better braking is needed when you have more HP....

It is also found on the Diesel W126 models.

Plus you do have a wider option of brake discs. Brand wise (Brembo), as well as cross drilled and slotted.

I discovered this when my parts guy sent me W126 discs by accident(they were brembo's.. but a name is a name)

If you don't want to go the used parts route, you can order rebuilt calipers and new rotors and use your old calipers for the core charge.

IIRC later 126's a slightly larger disc was used. IIRC, the last year W126 500 series had some a lighter caliper as well.

This upgrade is one of many on the list for me to do.

Have you guys seen the newer ATE discs? They have a "wear detector" that is basically 2 rounded squares grooved into the surface. Practically slotted. I will probably go with the ATE unless I upgrade to the vented.

another cool option is with the bigger(later gen) w126 brakes you also have the option of Zimmerman cross drilled rotors...

i would not go with cross drilled. they are prone to cracking. even high dollar cross drilled end up cracking. i know a porsche club track racer who claims to have seen many. slotted and maybe cryo hardened is the goods.

pgringo Wrote:i would not go with cross drilled. they are prone to cracking. even high dollar cross drilled end up cracking. i know a porsche club track racer who claims to have seen many. slotted and maybe cryo hardened is the goods.

Slotted are available as well iirc.

Are the 126 calipers a piston on either side as well? using the same principle as the 123, or do they use a slide?

AFAIK, they are the same as the 123, just larger. It has been over 8 months since I seen my calipers.

Aha! I see. This sounds like a great upgrade, especially since I am kind of experiencing the same kind of brake fade.

This may sound ridiculous, but several times I have read the word AFAIK on this forum and for some reason, assumed each time it was someones name!

Now I know better.

I just found a '86 126 in the junk yard, it is a 420 and it is all there. How much of the brakes should I use from it, calipers/rotors & lines and anything from the rear? Hey does it have a LSD that I could use in my CD, if I didn't have 15" and 16" rims I would get the 15" chrome rims off of it.

(08-19-2009 06:07 PM)Motorhead Wrote:  I just found a '86 126 in the junk yard, it is a 420 and it is all there. How much of the brakes should I use from it, calipers/rotors & lines and anything from the rear? Hey does it have a LSD that I could use in my CD, if I didn't have 15" and 16" rims I would get the 15" chrome rims off of it.

That's a 2nd Generation W126. They have bigger rotors. So you'll need to get the spindle/steering knuckle, rotors, backplate and calipers. Maybe the lines if they look new.

The 420 didn't come with a LSD. Plus since it is 2nd Gen w126, it will not be a direct bolt in.

Surfrodder just recently installed his, so he'll be good to get more info from.

(08-19-2009 06:47 PM)DeliveryValve Wrote:  So you'll need to get the spindle/steering knuckle, rotors, backplate and calipers. Maybe the lines if they look new.

You shouldn't need the spindles. Just the rotors, calipers and back plate.

You'll also need at least 15" wheels for them to fit.

I think the backing plates are the same at least they where on my w123 and w116

(08-19-2009 06:56 PM)ForcedInduction Wrote:  

(08-19-2009 06:47 PM)DeliveryValve Wrote:  So you'll need to get the spindle/steering knuckle, rotors, backplate and calipers. Maybe the lines if they look new.

You shouldn't need the spindles. Just the rotors, calipers and back plate.

You'll also need at least 15" wheels for them to fit.

My Bad, I meant to add that if you want to have ABS you would keep the spindles. W123 and W126 should be same.

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(08-19-2009 07:29 PM)willbhere4u Wrote:  I think the backing plates are the same at least they where on my w123 and w116

There have been reports the back plate rub with the bigger rotors.

(08-19-2009 07:29 PM)willbhere4u Wrote:  I think the backing plates are the same at least they where on my w123 and w116

For the wider genI W126 rotors they are, but Motorhead got a set of larger diameter genII brakes instead.

ah ok makes seance good to know!

Cool, I guess I will be in Pic-a-part on Sunday morning. I also seen a N/A '79 300 with a center inlet long runner intake, I have to stick to basics right now and get my pile going.

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Hey what gear ratio do you think would be in that 420, can I just R&R the pig and stuff my stock axles in it?