Firstfives.org

Good morning all,

firstly, please let me apologise for being an E21 interloper, but I am seeking guidance from those who know, rather than those who think they do in my E21 racecar build.

I am attempting to build an E21 Group 2 'Eggenberger' replica for club racing down here in New Zealand. In order to adequately fill the stupendous arch extensions, and to handle race loading, I intend fitting E28 rear subframe and trailing arms whcih will give me added track, a better selection of diffs, and also 5 stud hubs. For the front I will be having custom control arms fabricated, and intend using E12 front hubs, which I understand use the same spindle as E21s (320/6).

For brakes (as this remains a bit of a budget build), I have access to M635CSI discs and calipers for the front end as my brother has gone to a full AP Racing setup on his.

My question (yes, there is a point to this rambling) is whether my interpretation of the myriad of comments on the net is correct. i.e. can I take a regular E12 front hub/bearing assembly (non M535i), and marry it up to the E21 strut, and then fit the 300mm front brakes and calipers from a 1984 Jap spec M635. I know I will need the calipers mounted via a custom bracket.

Many thanks to anyone in the know. I appreciate your help.

Daniel

I will share what I know.
In order to get big brakes on a 2002, we use tii struts and mount the E21 early hubs (and all 6-cylinder cars) since they have the same spindle size, with E12 vented calipers and E21 vented discs.
The E12 hubs has never been used as an option on a 2002 tii struts. But I can not tell you the exact reason why.
Maybe that helps???

Welcome to our little group, and what a question.

I know all three of the chassis in question fairly well and I think you're into trial and error territory. I will further complicate it though, I've heard of front subframes being swapped between Es 12 and 28, not without some work, but I think the frame rail distance is the same. And I think E21s are the same also as you can drop a E28 radiator in between them and it fits, barely as it does in an E28. Also, what is the possibility of using either E12 or E28 front struts?

Gentlemen, thank you. And yes, quite a question.

I guess, I know that the E28 rear end will work with limited modification. I firmly believe that the E12 front hubs will fit, as some of the E21 boys speak of this. The key area I have seen no confidence-inspiring comment is whether the M6 (Or frankly, any late model 635CSI discs are compatable with the E12 hubs. I wondered if it was an upgrade done to E12s.

In NZ E12s are incredibly scarce. Probably few more than 10-20 remaining on the roads. So while I can possibly source hubs from a BMW wrecker, even that is not necessarily easy in order to casually mock things up.

Thanks again for your advice so far guys. I shall persist and if it all comes together I shall let you all know.

Daniel

If this helps, I just swapped the strut assembly from an '81 e24, 633 US, to an '81 e12, 528i, US.

The only difference, upon close inspection, was the spindles/axles. Each required their own tapered roller (wheel) bearings. It's obvious, not possible to assemble incorrectly.

Hubs, castle nuts, washers, calipers, rotors, mounting, bolts, brake lines, shocks, springs, top strut mounts, camber, caster,...all the same.

We certainly would enjoy some photos of this interesting project