E30 Roll Centers

[Digitalwave]

I am running E30 M3 suspension on my non-M so I have the opportunity to add roll center spacers to the front, and of course raise the subframe in the rear. The car is a dedicated track car (HPDE), but not being built to any rule book. I am running H&R Race springs. It is easy to tell I could benefit from the spacers in the front just looking at the control arms. My questions are:

1) I am running 16" wheels. Measuring the clearance in the front, it looks like I MIGHT be able to run a 19mm roll center spacer, but it would be very tight. Should I just stick with the 13mm to give breathing room in case I change wheels down the road?

2) Is it worth raising the rear subframe 12mm when running H&R Race on a track car?

I don't remember my last alignment specs, but I remember the rear had more camber than the front. I can only get so much out of the front before the spring hats impact the strut tower, due to the stock diameter spring. I don't plan to go to coilovers yet. It seems like raising the rear subframe would help balance out the camber, as I'd rather have more in the front. I'd like at LEAST 2.5* in the front, and 1.5-2* in the rear. My concern is the conflicting information I've read about how much the 12mm risers affect the camber. I've read as little at 0.5*, and as much as 4.5*.

[e30_302]

Why not just weld in trailing arm adjusters? Then you can set the camber and toe to pretty much whatever you want.

Can't really say on the roll center spacers, I've got a 1" spacer on a regular E30 strut. It worked, barely, with a 15" wheel. Had to get the grinder out.

[Digitalwave]

I'm not opposed to adding in the trailing arm adjusters, but I should have mentioned that I think that correcting the roll center is as important or more important than the camber change for me.

[kronus]

16" wheels can have somewhat different barrels, so you won't know if it clears until you try.

raised subframe mounts are worth it IMO, the closer the camber/toe alignments are to their original positions, the less likely to slip or bind.

[Digitalwave]

I figured as much. I've tried getting measurements between the tie rod end and the barrel of the wheel since my struts are off the car, but without knowing the angles the tie rod is going to be at, it's really hard to say. I may just need to buy both the 13mm and 19mm spacers and test fit once they are back in the car.

[nando]

raising the subframe 12mm in the rear is going to be about a 1/2 degree change. no way you're getting 4.5 out of that.

[Digitalwave]

Thanks Chris. I appreciate your input. I may just start PM'ing you my questions. ;)

[Ronan]

I have my subframe raised 12mm and just got an alignment the other day. Rear camber was -1.7 and .25 degrees of toe in. I do not have any adjustability on my trailing arms. And I have had very even tread wear and I autox once a month.

Ronan

[M-technik-3]

I bought my sppl centers from Lee, years ago. He might still have some

[bataangpinoy]

Totally worth using the rear subframe risers, even in a street car.

[autox320]

RC spacing front and rear is worth the effort. Bought mine from Lee. Using 17x8 apex wheels E30M3. Spacer thickness is 26mm - offset is 16mm. Not many have the offset ones that add front trackwidth. I bought the last offset set from Lee if you want a set can also order them through Millway in Sweden they carry them.

Most I've seen run the 13mm spacers and no offset. Can also make a diy bumpsteer gauge setup and see how far off for bump under compression or droop. Any amount raising the RC in the front helps with a lowered E30 though.

If choose the offset spacers they do have an advantage IMO. You will need to dent tune your fender wells and lips. Possibly break out the grinder etc. I'm having to relocate the tie down points on the front frame rails. I ran a new set of NT01's and the inside just can barely scrub the tie down when the tire gets hot and expands. But they are worth every penny in the handling dept. I"m currently on HR race also, but looking to move to a coil over in a year or so.

I forgot to mention that if use the offset ones they fit easier since more clearance to the wheel barrel. But you'll want rack limiters and a hammer for the other areas inside the wheel well :)

[autox320]

few pics I can find on this computer from last winter working on it

note I changed to hex head bolts on the inner lower 2 which allowed clearance at full droop







changed the two inner socket screws to hex after this photo

[BlackbirdM3]

You can get spring spacers for the rear from Ireland. Add those with the subframe risers, and thick spring pads, you can get pretty close to where you need to be. On my M3, I have 13mm front spacers, and then I added spacers to the tops of the camber adjusters (because the total length of the Strut assembly is what dictates the roll center) I have GC camber/caster plates that were too low of a stack height, so I had some spacers made up that brought the stack height up to just a little more than the stock non adjustable strut mounts should be. With the Turner J stock springs, the setup is very hard to beat, no body roll, car is firm, but not harsh. Totally neutral handling.

Will

[Digitalwave]

Thanks for the info everyone.

Blackbird, I was planning on adding a couple more spacers under my camber plates as well, as I think they may be binding on the top spring perch.

What size wheels are you running with your 13mm roll center spacers?

[BlackbirdM3]

Thanks for the info everyone.

Blackbird, I was planning on adding a couple more spacers under my camber plates as well, as I think they may be binding on the top spring perch.

What size wheels are you running with your 13mm roll center spacers?

Sadly, 16s. The car is far faster everywhere with 15s. You can only add to the top of the camber plates. The strut extension is the limiting factor, In order to add the spacers on top of the camber plates, you need to remove the original mounting bolts (the 3 that go through the body that hold everything on the car) and replace them with longer ones that allow you to put a donut shaped spacer on top of the whole mess.) I can take pics of what I did if you want. I also have the same issue with the spring hats contacting the underside of the camber plates. (I'm going to buy some Vorshlag plates that use the stock hats mounted to the plates. They are expensive, but they look like the best design for stock style springs.)

Will