bmwe21.net forums

Cheers guys. Been away for a while, but i think some of you might love what i brung

I have been on a extreme search of a more suitable front brake conversion for the E21 than the one most use when using the Volvo 4pots.

I have seen that many use the 323 discs, and this require slotting the calipers, and in some cases i have also seen people cut the brake pads to fit the small disc.

The volvo uses a 276mm disc so this was what i was looking for. A 276mm disc with a hat to fit the E21. The rather high hat of the E21 brake disc is really what makes problems for this build. But i got some help from Danish brake disc producer SBS Automotive. They found the perfect disc, and its easy and cheap to find

The disc is from a Mercedes Sprinter Van.

Diameter: 275,8 (Volvo is 276)
Hat is : 77mm (E21 is 75,5)
Hub centre is: 58,1 (E21 is 57,1)
Thickness is: 22mm (Volvo is 22mm)

The following things needs to be done to make the brake conversion kit.

You may or may not want to make a 0,5mm thick spacing ring for the centering of the disc as the hub on the E21 is 1mm diameter too small for the Mercedes disc.
You need to get the discs redrilled to 4x100 PCD. There is plenty of room for that as the Mercedes discs are 5x130 PCD.
The offset of the caliper is not spot on. As the 4 pots have 2 hydraulic cylinders on each side of the disc my guess is that they will compensate for that 1,5mm offset. If not, as the hat on the Mercedes disc is a bit deeper than the BMW ones, a wheel spacer of 1,5mm thickness can be put between the hub and the brake disc. This allow you to directly bolt a Volvo 4pot caliper on the BMW strut with NO modifications needed !

I am not saying i have found the holy grail, but i think that this is great news for anyone wanting to make a Volvo brake conversion to the E21.

Cheers, Ruben

Looks like this by the way

i have the volvo brake conversion with the 323i discs.

- mercedes has 5x112 PCD not 5x130
- the car brakes with 323i zimmermann discs and agressive pads extremely good, I don't thing there is a need for bigger discs.

No need to slot the calipers just machine (grind) of the top 3mm of the pad

This is exactly why i went offline from BMWE21.NET.

Theese totally idiotic comments.

If you have the slightest idea of how stuff works, especially brakes, you will know that the larger rotor diameter the better. First off the disc travels with alot more momentum on a smaller disc than a bigger disc = the large disc rotor will be more precise, you will experience fewer lockups, you will get a cooler disc when braking etc etc etc.

But noooo. Some shitty solution using those redicolous bicycle brake discs that the 323i is born with (no other 150hp+ 1100kg car in the world utilize that small a brake disc) is the stuff dreams are made off.

Then there is the comment of the Zimmerman brake discs. The Mercedes brakes are 50% of the price of those discs, and they will stop your car ALOT better.

Then of course the perfect thing. Cutting the pads.. That is really class act, screw safety just cut the pads. I tell you, any tuner in the world at any time would roll over in his grave if he heard that. That is just splendid.

I am telling you that this is the perfect setup you retards. What is wrong with you?

And NO the Mercedes sprinter does NOT run 5x112 PCD it is running 5x130mm!

I have required ALL technical data on theese discs + a complete list of what vehicles use them + the complete set of technical drawings. But f*** you i am not putting them up on this forum, i am posting them somewhere else on the internet, where people recognize progess and evolution instead of clinging on to their homemade solutions with pads that are cut to pieces..

Cheers mates, please Jeroen, this is nothing personal against you, please delete my account.

I am totally done with this site!

so you either have to machine the caliper or disk still a lot of work most people have to outsource

I agree brake disk size helps stopping power, and the calculations are based on the distance to the center of the piston. To fit the 4 pots to standard disk you machine about 3mm to oval the mounting holes, is that 3mm going to a noticeable difference to your left foo.

In a lot of stock racing classes inc several grids of caterhams machine down the pad area to refine the brake balance on the rear calipers as there is no other way to deal with the rear bais within the regs. I also have to get sets of 600 euro endless pads machined to fit the 24 endurance car i work here, an they still wok for a 20 hour stint.

When i first did this conversion about 15 years ago i just bolted the volvo 4 ports and run them as stock this created about a 2mm over hang which would just brake of, so i used to get the top of the pad material ground of to stop the squealing, but with ap 4 pots and 325mm disks i don't have that problem any more.

If you want to check disk sizes use this web site http://www.apecbraking.co.uk/catalogue

Also when you grow up you will be able to express opinion of people more eloquently and with having to use swear words

LOL Mr Ruben did find an alternative but he's far from finding the perfect solution. Redrilling to get to the right PCD would defo not be my first option, 276mm is far from the holy grail and using spacer rings to center the caliper is not an option but a must.

What size of disc you choose, to get back to the basics, depends on the use you make of the car. A stock E21 that only sees the regular roads will definitely benefit from the 4 pot Volvo conversion combined with decent pads and get you upgraded stopping power (there are alternatives as well like we've done with the Wilwood group buy). The fact that the relatively small disc from the E21 only has a limited capacity to absorb heat is clear, but most of us would never come to a point where this becomes a problem. Overheating discs usually is caused by other factors like seized calipers.

On the track, for trackdays or when doing the mountains in an enthusiastic style, that's when the rotors may become the bottleneck. If Mr Ruben would have visited this website lately he would have found that we have decent alternatives for the disc that have a larger size than the 276 mm disc he's suggesting.

In my opinion the person calling names and accusing others of a limited view is hampered by a limited view himself. If that leads to posts like the above (I edited it now) I think we're far better off without the hazy personal views of Mr Ruben. Locking this topic now and saying goodbye to Ruben.