kevincnc

Hi all,
A couple of years ago Robstah posted a DIY "Budget Coilover" thread in which he cut ring grooves in a shock to support a spring seat. After doing a search I found that the thread has since been closed, and all the info except for replies have been deleted. I pm'd him to find out why but haven't received a reply; I don't think he's been active for a while.

Does anyone know why it was deleted? Safety concerns maybe?

My '89 squats quite a bit now with the extra power, especially with a passenger, and I'm not sure what to do. It only has 45k miles and the shocks seem fine. I just don't want to spend a fortune on a new suspension, and don't even know if I can beef up the rear a little without changing the front. I don't really want a harsher ride, and it handles well on curvy roads, the squat in first and shifting into second just seems excessive.

Any advice would be appreciated!

Kevin

Voith

Robstah wanted to leave and took his stuff with him if I remember correctly.

RoyaleWithCheese

He made a blog after he left rennlist where he posted the writeup on how to do the coilovers.

I can't seem to find it right now but if I do I'll post it for you.

RoyaleWithCheese

http://944tech.wordpress.com/

V2Rocket

the squat is sort of inherent to the rear suspension design - youll need a lot of spring to make it go away.

kevincnc

Thanks guys, and especially for the link Royale. So Spencer are you saying it's not worth messing with? Even if I did it, I have no idea what springs to use to be able to keep my front M030 shocks, or if that's even a good idea since I want to keep the balanced handling that I currently have. The last thing I need is to spin out and crash into a barrier or go over a cliff.

Dimi 944

You can easily add a rear coilover with a low rate spring not to compromise the ride much and retain good balance. What are the spring rates of your front springs?

kevincnc

According to this- http://members.rennlist.org/dan10101/944SpringRates.htm

it's 175. I am so ignorant about suspension, I don't even know what Wheel Rate is. I nedd lots of education on subject I guess.

Van

Spring rate is a measurement of the force it takes to compress the spring - e.g. 175 lbs to compress the spring 1" (or 175 lb/in). Most springs are linear, meaning it will take 2x the force to compress it 2".

Wheel rate is the pound force required to move the wheel... Because shocks/struts can never be placed exactly over the tire's contact patch, and also can't be perfectly vertical, there is some effective multiplier. For example, if your shock is at the halfway point on the control arm, for every inch of wheel travel, the shock only compresses 0.5". So, if you have a 175 lb/in spring on there, the wheel rate is only 87.5 lb/in.

The multiplier used to make that conversion is called the motion ratio and can be calculated mathematically by angles and distances, or through precise measurements.

I'm going on memory here, but the motion ratios are something like 0.92 front and 0.65 rear.

mikey_audiogeek

Van, wheel rate is spring rate x motion ratio squared...
In your example, the wheel rate would be 43.75 lb/in.
Cheers,
Mike

Van

Ahh, right. What Mike said.

kevincnc

Thanks guys. How then, do I determine a spring rate if I do the rears like Robstah did to keep good balance and reduce squat?

Dave W.

What size torsion bars do you have in the rear?
Adding stiffer springs in the rear will upset the balance, so ideally you'd need to increase the spring rate up front to match the rear. I'd also look at the rear bumpstops since they rot away over time. Once they're gone the rear end can squat badly. Also, if you add more power the squat gets worse.

admiralkhole

If you go the diy/bilstein route I have some 400lb hyperco springs for sale. Shoot me a pm if interested.

Oddjob

Higher spring/t-bar rates and higher shock damping would help the squat, but if you don't want a harsher ride, there is little way to reduce suspension travel. And yes, if you increase the rear by a noticeable amount, you also should stiffen the front.

The homemade bilstein HD coilover setup is not the way to go for your car. Bilstein HD's are no better a shock than the koni single adjustables, actually probably not as good as the orig M030 suspension. The HD's would be an upgrade over stock boge/sachs.

The spring rate chart you posted has a lot of errors on it. Stock 951 front springs are the same rate as a stock 944, about 120 lb/in (21N/mm). Turbo S/M030 are 160 lb/in (28N/mm). S2/968 springs are around 136 (23.8N/mm).

You might want to look for 968 M030 rear shocks with the barrel helper spring, they are not a significant increase in rear spring rate. But installing those does require reindexing the rear torsion bars. And they are getting harding to find used.