Best E30 Rally Suspension Setup

[2002maniac]

You could try running E36M3 springs for a little more ride height and stiffness, but the best setup would be longer 2.5" springs with adjusters from Ground Control.

[Bimmerman325i]

^^ that. The coilover springs and perches kit ($399) is used by lots of subaru guys to pick the rates they want but have much longer than stock shocks.

A TON of subaru guys rallycross on Tokico D-spec shocks. I have no idea if they are made in E30 fitment, I kinda doubt it.

But Sam, best bet is to call the local rally prep experts (they ran and prepped travis pastrana's car for years).

[iamsam]

Hmmm, methinks we have a terminology mix up:

Bump stop = device to limit upward travel of the wheel

So the bump stop could see many thousands of pounds in a jump landing situation where the car sees a few Gs in an upwards direction. So tiny shock stops, warranty or not, are no good.

Also, that subframe needs bracing badly. I better brush up on my welding.

Ah yes, I must have misuderstood you.

So to answer your question more accurately, in the rear, what stops full compression is literally the spring itself compressing fully, which is sandwiched between the trailing arm and unibody. This is is as strong as it gets, however I am not sure if the spring fully compresses or the shock hits the internal bump stop first. With thicker spring pads and a taller E36 spring, I am pretty sure the spring will fully compress before the shock bottoms out.

These pics may explain a little:





In the front, you have a strut setup like this:



And the internal bump stop stops full compression. However, it would be super easy to weld up something to the control arm to stop the travel under extreme circumstances.

However, I am thinking the BEST thing to do is to use E36 325is springs, they are taller AND stiffer, so they have more travel, and can absorb alot more impact energy than stock E30 springs. With a lightweight car, oversize tires, and E36 325is springs and Billy HDs, I doubt you will bottom out too bad.

[Bimmerman325i]

Sam, you DON'T want stiff springs. Not at all.

You want max travel and SOFT springs, otherwise you'll have no traction. You want taller linear springs with a low rate, i.e. the GC coilover conversion kit.

Also, in the rear, shock bumpstop compresses before spring travel is minimized....for most springs.

[SlapDash]

Thanks for the inputs, guys. Sounds like reinforcement and plating are the rules of the day! Slapdash, went to the site... hope you can get it all put together and I look forward to seeing how it does for you. I'll try to contact the guys at cagethis, but this goes for anyone out there... if you have caged an E30 and have had it pass RA scrutineering, I would pay for a good set of pictures and dimensions of your cage. Let me know!

And keep those comments coming... I'm in full sponge mode.

I'm making my RA logbook attempt on the 16th. I'll let you know how it goes.

Also, I know he's backed up a little, but in the past, Bill Doyle has made and sold E30 rally cages that you could weld in. Not sure on prices or if even he can do it now, but I've seen it done.

[monkeytaco]

Sam, you DON'T want stiff springs. Not at all.

You want max travel and SOFT springs, otherwise you'll have no traction. You want taller linear springs with a low rate, i.e. the GC coilover conversion kit.

Also, in the rear, shock bumpstop compresses before spring travel is minimized....for most springs.

See Sam, this is what I said in the beginning. Soft springs and loads of travel, I've never purpose built a rally car, but I have done some serious rally driving...

I'm all about helping on this build. And then driving the car at CORE. :)

[MasterOfPuppets]

Sam, you DON'T want stiff springs. Not at all.

You want max travel and SOFT springs, otherwise you'll have no traction. You want taller linear springs with a low rate, i.e. the GC coilover conversion kit.

Careful saying max travel when talking to a jeep owner :mrgreen:... there's obviously got to be a happy medium between high and low spring rates, and I'm sure it depends on your anticipation of the terrain to be rallied. Since I'll be doing almost exclusively gravel, I'd be interested to know what you experienced E30 guys have run for those events.

I'm making my RA logbook attempt on the 16th. I'll let you know how it goes.

Can't wait. And some more pics of the whole setup would be great (I scoured your website and it seems like you've been building more car than web lately - as it should be).

I'm all about helping on this build. And then driving the car at CORE. :)

People lining up to drive my unfinished (hell, unstarted) car, should I be flattered? I keep telling Sam to set up an R3V day at CORE... it may take some peer pressure to get him going.

[MasterOfPuppets]

Just had what could be a great idea:

1.) Run the E36 springs, which are taller and have a higher rate than stocker E30s

2.) Run stock size or smaller/less effective anti-roll bars

This would result in a stock-ish or perhaps slightly softer rate for a one-sided jounce (rock, pothole, etc), but an increase in rate for both-sides jounce (jump, landing, crest, etc). The effective anti-roll would likely end up about the same or a bit less. This setup seems to me like it would make sense... any comments?

[iamsam]

Just had what could be a great idea:

1.) Run the E36 springs, which are taller and have a higher rate than stocker E30s

2.) Run stock size or smaller/less effective anti-roll bars

This would result in a stock-ish or perhaps slightly softer rate for a one-sided jounce (rock, pothole, etc), but an increase in rate for both-sides jounce (jump, landing, crest, etc). The effective anti-roll would likely end up about the same or a bit less. This setup seems to me like it would make sense... any comments?

It seems people above have been mentioning soft springs, and david and I (Bimmerman325i) had a long g-chat debate about it last night. My take was that soft is good (my car on H&R Races SUCKED), but stock E36 325is springs are still soft, just stiffer than stock E30 325is springs.

I mean, how soft is "soft"? if we compare these springs to springs 90% of R3Vers run on their cars, then E36 325is springs are ridiculously soft.

imo, "too soft" is when you bottom out the suspension completely when say, you drop an E30 from a height of 2" off the ground. That number of course just taken from the top of my head. i.e, the more suspension travel, the more "soft" you can get away with. But as Mike mentioned, there has to be an ideal medium window of spring rate and travel length.

The question then arises, what springs fit in that window?

Actually, the conversation with David and I went like this:

David: e36 springs are NOT what you want

me: why

David: stiffer is bad you want SOFT tall and soft and linear

me: right, i was figuring stock E36 springs are still pretty dang soft

David: stiffer. and not linear

me: arent stock springs linear? i thought they were

David: ohhhh no NO car in any remotely affordable category has linear springs most aftermarket springs aren't even linear

me: hmmm so ultimately GC coils would be best, obviously, because you can get them in any size and shape you want, and no strut housing shortening needed....

David: preston bought purpose built rally coilovers for his car full GCs are not what you want just the spring/perch conversion

me: right of course

David: you don't want Konis, they aren't made for rallying

me: and some decent shocks

David: yup tokico, Tein, ASTs

[2002maniac]

E36 springs are soft. Go any softer and you'll be bottoming out constantly.

[iamsam]

E36 springs are soft. Go any softer and you'll be bottoming out constantly.

E36 325is springs are stiffer than E30 325is springs.

Info from Ross (monkeytaco)

Stock E30 325is front/rear: 118/265
Stock E36 325is front/rear: 135/280

Ross, correct me if I am wrong, it was ridiculously hard deciphering our g-chat.

(Why am I no longer getting email notifications on this thread??)

[MasterOfPuppets]

Stock E30 325is front/rear: 118/265
Stock E36 325is front/rear: 135/280

Fixed...

And it sounds like the way to go. A bit more travel, a bit more rate, and some heavy duty shocks, and I should have a fairly low chance of oilpan to ground smashage.

[Eric]

I have nothing constructive to say about building a rally car.

I'm just posting here to say that I want to drive it too!

[iamsam]

Beginning Rally Car Dismemberment...

yaargh talk about a PITA... I am not looking forward to removing the rear swaybar, it looks like I'll have to drop the diff AND the exhaust AND the gas tank filler hose thingy. Unless I can somehow pull it out the wheel well past the diff...

[Bimmerman325i]

Just a thought, but unless e36 springs are muuuuch taller, you wont notice any benefit. The change in rates is on the order of 10% front 5% rear (eyeballed percents), which isnt all that different in terms of keeping oil pan off ground stiffness needs. Youll notice a tiny difference, but im not sure it is any better than running oem springs. Remember, raising car means gaining positive rear camber, which is bad.

The small difference in rates likely wont do much of anything, the height would.