THSCC Forums

So I'm working on project SO2, the 86 BMW 325es. It's got some fairly low sport springs on it that just aren't going to do for rallycross. Also it has bilstein shocks which seem to be in good shape.

The car is too low and it makes a bit of a crash over hard bumps. I cannot find bumpstops on the front shocks under the dust cover ... perhaps the Bilsteins have an internal bumpstop?

Anyways, I'm trying to figure out what makes for a good rally suspension setup. Since I have almost no money invested in this car (but a ton of sweat equity!!!), I'd say my total budget is like $100 for now

If I don't find any other options, I plan to just put in a set of stock springs and factory bumpstops. But I was thinking that it would actually be really nice to have a stiff spring that lets the car sit at stock ride height. That way there would be stock suspension travel but the wheel would actually move less because of the higher rate. However, I can't find a spring like that for these cars.

If it was possible to stretch the sport springs out by a few inches I think that would be ideal. Anyone know if this can be done? Maybe I should call up a spring shop and ask

Anyone have other suggestions to accomplish stock ride height and travel, but higher spring rate? Or can someone point to other resources to understand rally suspension design?

Mike <-- too many thoughts rolling around in my head, not enough time or money to do anything about it

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Mike Whitney
whit32@gmail.com, 919-454-5445
V10, V8, V8t, I6, I6, V6, F4t, I4, I4, I4, I4, I2, 1, 1

I don't think stretching the spring will change the rate much anyhow. The only thing it would do is make the effective diameter a little smaller and drive the rate up proportionally. Wire diameter and number of free coils are what matter most.

It doubles your budget but you can get *new* Afco springs for about $45 each in a choice of diameters, free lengths and rates. I run these on the back of the old Celica.

Another option is to do an ebay search for Afco springs and get them used (typically about 1.2 price).

Scott

Here ya go, there are two of these up right now:

http://cgi.ebay.com/ebaymotors/ws/eBayI ... gory=33582

$20 gets you 950 lb rate up front. It shouldn't be too soft.

Scott

Are any of the springs from a heavier bmw interchangeable?

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In need of car.

i was just gonna say.. i'm gonna be picking up the stock 535is springs from the guy i got my 88 535is from probably this weekend.. i'll throw those your way if they'll fit in exchange for a few fun runs

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'88 bmw 535is
'98 honda civic ex

Why don't you use spring rubbers and crazy glue to achieve the proper balance between stiffness, ride height and ghetto-ass cheapness?

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Has no responsibility whatsoever.

Actually, Scott - the spring rate of the "sport springs" on the car right now would be great. I just need to lengthen the springs by 2 inches. I wasn't expecting the stretching to change the rate at all.

I'll look into Afco.

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Mike Whitney
whit32@gmail.com, 919-454-5445
V10, V8, V8t, I6, I6, V6, F4t, I4, I4, I4, I4, I2, 1, 1

Matt - please do let me know about those springs. If you have an easy way to compare them to stock E30 springs for the diameter, let me know how they compare.

I would really need to know free height, spring rate, and my car's fron axle weight to figure out how close I would end up to stock ride height though.

Hmmmm....

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Mike Whitney
whit32@gmail.com, 919-454-5445
V10, V8, V8t, I6, I6, V6, F4t, I4, I4, I4, I4, I2, 1, 1

I have a solution for you with 3 simple steps.

1. Jack up car
2. Stuff gaps between springs with paper towels.
3. Take car off jack

Taa daa - new higher ride height and greater effective spring rate.

It should fit within your budget since it's only a few bucks for 4 rolls of Bounty (one per corner). It also has the added benefit that if it isn't stiff enough, you just wet the towels down and let harden.

Shawn

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OK so I'm back in. Now which tire should I buy??

mike.. i could just bring them to you after i pick them up and you can try them if you want..

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'88 bmw 535is
'98 honda civic ex

http://www.bsrproducts.com/productframe.html

Link doesn't go directly to page so click on "springs and accessories" . . .

scroll down to bottom of second page.

Dick

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Dick Rasmussen

FS 50 2018 Mustang GT

So you need 2 inches. How about cutting a spacer out of a 2X4. that would give you 1.75 inches of height. And the sudden ride hight changes when the blocks split would be entertaining to watch.

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George Bright Member # 141
One of the youngest of the old farts.
Yes I voted against you joining the club.

Rallycross suspension for $100?

Hmmm.

Go to the scrapyard, buy a big sheet of aluminum for about $35, bolt to bottom of engine bay. Suspension problem solved.



Anders

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Lina Racing: As Seen On Radio

If the bilsteins are inverted, then I'm pretty sure the bumpstops should be on the inside.

I used KYB AGXes with the Version 5 (1998?) STi springs on my car the first two rallyxes, and they were great. The springs were 1/4" lower in the front & 1" lower in the rear, and the rates were about 20-30% higher than stock.

If the bilsteins are definitely working well, I'd just put some stock springs on it. (And add bumpstops if they really are missing)

The Tein HG suspension I have now has springs that are stock design, and only 20% stiffer in front & 15% stiffer in the rear. It's the damping that controls the suspension movement - and it's REALLY well-controlled.

You may try to locate a set of used e30 325ix springs like in Kristin's car. I'm guessing she would prefer it not be from her car but you get the idea. Bret Luter (sp?) may have a line on some. I think they sit about 1/2 - 1 inch higher than the stock 325 springs are a hair stiffer (10-15%?). With less weight than the 325ix, it should give you even more clearance before something bottoms out without affecting the handling much.

The one gotcha may be that the strut assemblies up from are slightly different IIRC. I believe the springs are still interchangeable but you would have to research that a bit.

Jim