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Unread 02-05-2010, 12:51 PM
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Fair! Fair! is offline
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Join Date: Jul 2004
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Default Re: Vorshlag $2010 GRM Challenge car - BMW E30 V8

Project Update for Feb 5, 2010: We had a group of 4 of us working on the GRM $2010 E30 last night, including new team member Derek! He stopped by the shop yesterday to sell us some engine parts needed for the V8 swap, fell in love with the little E30, and now he's on board. This project seems to be a magnet for local car guys!

The main item on the night's agenda was to finish our E36 front suspension/brake/5-lug swap. We spent the entire evening mocking up, measuring and installing control arms and spindles to try to fix the "altered wheelbase" issue that accompanied our E36 front suspension swap onto the E30 chassis. We were told to try early E36 spindles with late LCAs, so we tried that - and a hullva lot more permutations.

We didn't find the magic combination that allows an E36 spindle + strut to be used on the E30 chassis - because we feel that there is no magic bullet. The "Easy 5-lug and E36 strut swap!" theory is a myth. Check out these pics and I'll explain further.

In the pictures above you an see the E36 spindle, brakes, and E36 coilover strut (not our final strut solution for the $2010 budget - just an interim AST coilover we had laying around until we found a cheaper solution!) installed onto the E30 - and the massive alteration in wheelbase. This tiny stock 205/60/15 tire and stock 15x7 E36 "bottlecap" wheel tire is rubbing like crazy at the back of the wheel arch and inner sheetmetal when turned, at this lowered ride height. Of course we had the maximum offset on the rear LCA bushings... we ran out of room there long ago.

This tire rub issue is because the front wheel has been moved rearward by over an inch, and is interfering with the fender opening and even the inner sheetmetal and unibody. It will have changed the caster in a bad way as well. Well, damn that...

Here you can see the various "non-M" Lower Control Arms (LCA) available on the E30, E36 and E46 chassis. We've tested the E30 M3 and E36 M3 LCAs and they all look very similar, but will round up examples of these M versions (all on cars in the parking lot including Matt's '95 M3, my '97 M3 and an E30 M3 we can borrow). All of the E30 and E36 LCAs we measured were IDENTICAL. To the mm. The "A" distance was the same on all of the E30 and E36 arms we tested, with only the E46 arm having a different "B" number (1" longer). The hypotenuse (and any fore-aft offset of the spindle mount) was also the exact same between all E30 and E36 LCAs we tested too - so the differing part numbers between early and late E36 LCAs seemed to be only cosmetic in nature.

We still installed and test fit wheels with all of these LCAs, "just in case" and there was no difference in the wheelbase issue, of course. The E46 LCA was indeed longer, but this only caused a huge amount of negative camber, and didn't affect the caster/wheelbase issue at all.

What's the solution? How can you use E36 suspension parts in an E30 and keep the wheel centered in the wheel opening? Well I'm fairly certain there's not going to be a solution that uses factory spindles and control arms. That parts-bin solution seems to be a total myth.

If you look closely at where the LCA mounts to the spindle on an E36 and E30, there lies the problem. On the E30, where the spindle and strut tube are one piece (a retarded and very limiting design) there's no room to get to the top of the LCA ball joint mounting nut... so this mounting hole its moved rearward on the spindle by about an inch compared to the E36. On the E36, the strut un-bolts from the spindle, so since yoiu can gain access to it they have moved the lower mounting hole on the spindle to almost right under the strut axis itself, and when this spindle is used on an E30 its going to pull the wheel backwards about an inch. Bad.

Notice the offset from the strut axis to the spindle mount on the E30. On an E36 this is very different

We're going to try to make or modify one of the many stock steel Lower Control Arms to allow the E36 spindle and brakes fit. Why? Well we REALLY need the 5-lug pattern from the E36 bits, to be able to use the cheap GM 5-lug pattern circle track wheels we scored (new 15x10's for $50 each don't exist for 4-lug BMW pattern), which will give us a grip advantage with some used 275/35/15 Hoosiers. Also, the cheap-to-free used E36 spindles and brakes are a big upgrade over the E30 bits (11.5" diameter E36 brake rotor vs 10.5" from the E30). Lastly, there are TONS of low cost, used E36 struts out there, but decent/used/cheap E30 strut inserts are few and far between.

We'll include these pictures and more detail on our final solution later, in a full blown tech article. There's got to be an affordable way to run E36 suspension on an E30, and by damn, we're going to find it.

Stay tuned...

Last edited by Fair!; 03-05-2010 at 10:57 AM.
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