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+--- Thread: w126 first gen on a w123 (/showthread.php?tid=175)
w126 first gen on a w123 - MTUPower - 03-01-2008
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
![[Image: N100016089BAL.JPG]](http://img.eautopartscatalog.com/live/N100016089BAL.JPG)
and here is the w126 rotor
![[Image: N100016595BAL.JPG]](http://img.eautopartscatalog.com/live/N100016595BAL.JPG)
Better braking is needed when you have more HP....
Re: w126 first gen on a w123 - ForcedInduction - 03-02-2008
It is also found on the Diesel W126 models.
Re: w126 first gen on a w123 - TheDon - 03-02-2008
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)
Re: w126 first gen on a w123 - ForcedInduction - 03-03-2008
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.
Re: w126 first gen on a w123 - winmutt - 03-03-2008
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.
Re: w126 first gen on a w123 - winmutt - 03-15-2008
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.
Re: w126 first gen on a w123 - TheDon - 03-16-2008
another cool option is with the bigger(later gen) w126 brakes you also have the option of Zimmerman cross drilled rotors...
Re: w126 first gen on a w123 - pgringo - 03-17-2008
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.
Re: w126 first gen on a w123 - winmutt - 03-17-2008
pgringo 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.
RE: w126 first gen on a w123 - JB3 - 04-22-2009
Are the 126 calipers a piston on either side as well? using the same principle as the 123, or do they use a slide?
RE: w126 first gen on a w123 - kamel - 04-23-2009
AFAIK, they are the same as the 123, just larger. It has been over 8 months since I seen my calipers.
RE: w126 first gen on a w123 - JB3 - 04-23-2009
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.
RE: w126 first gen on a w123 - Motorhead - 08-19-2009
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.
RE: w126 first gen on a w123 - DeliveryValve - 08-19-2009
(08-19-2009, 06:07 PM)Motorhead 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.
RE: w126 first gen on a w123 - ForcedInduction - 08-19-2009
(08-19-2009, 06:47 PM)DeliveryValve 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.
RE: w126 first gen on a w123 - willbhere4u - 08-19-2009
I think the backing plates are the same at least they where on my w123 and w116
RE: w126 first gen on a w123 - DeliveryValve - 08-19-2009
(08-19-2009, 06:56 PM)ForcedInduction(08-19-2009, 06:47 PM)DeliveryValve 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.
(08-19-2009, 07:29 PM)willbhere4u 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.
RE: w126 first gen on a w123 - ForcedInduction - 08-19-2009
(08-19-2009, 07:29 PM)willbhere4u I think the backing plates are the same at least they where on my w123 and w116For the wider genI W126 rotors they are, but Motorhead got a set of larger diameter genII brakes instead.
RE: w126 first gen on a w123 - willbhere4u - 08-20-2009
ah ok makes seance good to know!
RE: w126 first gen on a w123 - Motorhead - 08-20-2009
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.
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?
RE: w126 first gen on a w123 - bricktron - 09-26-2013
i know the second do not, but do the first gen W126 rotors fit in 14 inch wheels?
edit: kept reading and it sounds like the answer is yes, but with no size increase over the W123 ones, just vents.
RE: w126 first gen on a w123 - DeliveryValve - 09-27-2013
(09-26-2013, 04:54 PM)bricktron i know the second do not, but do the first gen W126 rotors fit in 14 inch wheels?
edit: kept reading and it sounds like the answer is yes, but with no size increase over the W123 ones, just vents.
Yes that is correct. They are the same diameter as the w123 rotors, but vented and thicker which requires the w126 calipers to work.
I have this setup on my car and I think front vented rotors are imperative to have.
.
RE: w126 first gen on a w123 - bricktron - 09-28-2013
OK, but don't you have to do rather a lot of braking to overheat the rotors? for racing, or even driving down a mountain, i can understand this; when does it come up for you?
RE: w126 first gen on a w123 - DeliveryValve - 09-29-2013
I guess the use of the word "imperative" seems pretty dramatic. But you can have the potential for brake fade at any time in an emergency hard braking situation. Brake fade leads to longer stopping distance.
Couple of examples for my peace of mind i get with vented brakes.. I often drive over the Grapevine on the I5 which sometimes requires avoiding crazy drivers doing the unexpected going down the mountain. I'm also in constant stop and go driving in 100 plus degree ambient temperatures.
This is pretty much normal driving I do, but I would think on the hilly streets of San Fran, you should definitely consider this upgrade. City stop and go driving as well as stopping on a down hill should help with that performance.
.
RE: w126 first gen on a w123 - bricktron - 09-30-2013
fair enough. is it well known at what rotors temperature the brakes suffer fade? i have a handheld infrared thermometer and i would like to sample their temperature right after heavy braking to get a sense of the risk here. as far as i know, i have never experienced brake fade in any car, but i could be wrong.
i can't deny that the vented rotor is better, just trying to prioritize other things given my limited bandwidth.
on a somewhat positive note, i squealed the tires for the first time this morning!
RE: w126 first gen on a w123 - lgreeley83 - 09-30-2013
Don't know temp but yeah for squealing tires.
Back burner for you I think. Qatar is flat Isn't it? I'd say wait for a need to upgrade. If your calipers go out replace with the upgrade. If you find them cheap in a junk yard get them.
RE: w126 first gen on a w123 - DeliveryValve - 10-01-2013
(09-30-2013, 02:33 PM)bricktron fair enough. is it well known at what rotors temperature the brakes suffer fade? i have a handheld infrared thermometer and i would like to sample their temperature right after heavy braking to get a sense of the risk here. as far as i know, i have never experienced brake fade in any car, but i could be wrong.
i can't deny that the vented rotor is better, just trying to prioritize other things given my limited bandwidth.
on a somewhat positive note, i squealed the tires for the first time this morning!
My understanding is regular stock brake pads are made to fade around 300°-350°C. Performance pads are made to fade about 400°-700°C.
Btw- I have a core set of 1st gen calipers I can let go cheap cheap cheap. You can rebuild them or trade them in for rebuilds. PM me if interested.
RE: w126 first gen on a w123 - swampmonkey - 10-03-2013
have second generation myself 1991 w126, works great.
looks front tires without problem doing 60mph and with 225/45r17 wheels
Great feeling to have that stopping power
and a tad extra pressure and the rear locks up too, with stock rebuilt calipers and new discs.
RE: w126 first gen on a w123 - willbhere4u - 10-04-2013
I had w116 300sd front and rear calipers/rotors on my 240d turbo project same dimensions but vented. It worked great I got all of it for free off a parts car it was all brand new with less than 100 miles. next time i'll go with the 2nd gen w126 brakes.
RE: w126 first gen on a w123 - sassparilla_kid - 10-04-2013
What about wagons? I hear they have larger rear calipers?
RE: w126 first gen on a w123 - swampmonkey - 10-05-2013
i think the w115 is supposed to have 38mm calipers at back, while the w123 has 42mm, other than that, i dont know about any other difference, even the late w126, and early w123 are supposed to be the same. at the back.
RE: w126 first gen on a w123 - bricktron - 10-06-2013
thanks. i'm afraid i really want the 2nd gen brakes - but still haven't found a wheel that would let me keep the color hubcaps. so i am stuck on this one.
RE: w126 first gen on a w123 - swampmonkey - 10-06-2013
(10-06-2013, 12:09 AM)bricktron thanks. i'm afraid i really want the 2nd gen brakes - but still haven't found a wheel that would let me keep the color hubcaps. so i am stuck on this one.
yep, 15" steelies is rare, and 15" hubcaps even more so.
looking for hubcaps for a complete sleeper look, mudflaps, hubcaps and not noticable lowered. 14" isnt an option with the front brakes changed.
go for first gen w126, they arent bad, and if you are not supposed to go racing on track, they will probably be more than enough
RE: w126 first gen on a w123 - DeliveryValve - 10-07-2013
(10-04-2013, 07:52 PM)sassparilla_kid What about wagons? I hear they have larger rear calipers?
Yes they have larger pistons, larger than the w116 and w126.
RE: w126 first gen on a w123 - swampmonkey - 10-08-2013
(10-07-2013, 08:33 PM)DeliveryValve(10-04-2013, 07:52 PM)sassparilla_kid What about wagons? I hear they have larger rear calipers?
Yes they have larger pistons, larger than the w116 and w126.
that was new to me!
good to know, how large? diameter etc?
(10-07-2013, 08:33 PM)DeliveryValve(10-04-2013, 07:52 PM)sassparilla_kid What about wagons? I hear they have larger rear calipers?
Yes they have larger pistons, larger than the w116 and w126.
that was new to me!
good to know, how large? diameter etc?
RE: w126 first gen on a w123 - DeliveryValve - 10-08-2013
(10-08-2013, 07:46 AM)swampmonkey(10-07-2013, 08:33 PM)DeliveryValve(10-04-2013, 07:52 PM)sassparilla_kid What about wagons? I hear they have larger rear calipers?
Yes they have larger pistons, larger than the w116 and w126.
that was new to me!
good to know, how large? diameter etc?
Taking a quick measurement. Approximately 38mm vs 36mm.
.