Effective spring rates

[z3papa]

On 17" wheels with 40 aspect tires, it's fine for me. On 18" wheels with 35 aspect tires, it can be rough.

[fmcfad01]

On 17" wheels with 40 aspect tires, it's fine for me. On 18" wheels with 35 aspect tires, it can be rough.

is that 600 or 700?

I'm running TC Kline SAs...so I don't have the ultimate of adjustment.

[spidertri]

My car came with 425f/525r on koni sa with stock swaybars. I use my car as a daily. Its on 17x8.5/17x9 style 32s, which look sweet but are heavy. Lighter wheels would improve the ride too.

Rear was way too soft, the shocks were bottoming out and felt terrible. I bumped the rear springs to 600 and it made the ride better, you could definitely feel the suspension "catch" the car over big dips in the highway. Some really crappy roads, expansion joints, etc would still cause a shock to bottom out.

I bumped the rear again to 700lb and I have not yet felt the rear suspension bottom out. Part of my commute is at sub 25mph speeds on very patched asphalt, the 700s definitely communicate the imperfections. At those speeds the whole car moves with the bump. At highway speeds, its not bad at all, the suspension soaks up any rough stuff.

Somewhere between 600 and 700 is probably the sweet spot in my opinion.

[dcrothers]

With my MCS i am running 450f/600r.
I was having a lot of trouble finding a comfortable DD setting until i raised the car up.
In lower stance i wasn't getting enough travel of the shock i guess.
I'm no suspension guru, but for MCS at least, i think they would benefit with a shorter shaft to allow the car to sit a bit lower and still maintain travel.
At the first rebuild i will discuss this with them to determine if it's beneficial or not.

[z3papa]

is that 600 or 700?

I'm running tc kline sas...so i don't have the ultimate of adjustment.

500f/700r

[f50nut]

My car came with 425f/525r on koni sa with stock swaybars. I use my car as a daily. Its on 17x8.5/17x9 style 32s, which look sweet but are heavy. Lighter wheels would improve the ride too.

Rear was way too soft, the shocks were bottoming out and felt terrible. I bumped the rear springs to 600 and it made the ride better, you could definitely feel the suspension "catch" the car over big dips in the highway. Some really crappy roads, expansion joints, etc would still cause a shock to bottom out.

I bumped the rear again to 700lb and I have not yet felt the rear suspension bottom out. Part of my commute is at sub 25mph speeds on very patched asphalt, the 700s definitely communicate the imperfections. At those speeds the whole car moves with the bump. At highway speeds, its not bad at all, the suspension soaks up any rough stuff.

Somewhere between 600 and 700 is probably the sweet spot in my opinion.

This leads me to believe that Ground Control really nailed it with their recommended spring rates for daily driving; 440f/660r, versus TC Kline's recommendation of 400f/500r.

[z3papa]

My car came with 425f/525r on koni sa with stock swaybars. I use my car as a daily. Its on 17x8.5/17x9 style 32s, which look sweet but are heavy. Lighter wheels would improve the ride too.

Rear was way too soft, the shocks were bottoming out and felt terrible. I bumped the rear springs to 600 and it made the ride better, you could definitely feel the suspension "catch" the car over big dips in the highway. Some really crappy roads, expansion joints, etc would still cause a shock to bottom out.

I bumped the rear again to 700lb and I have not yet felt the rear suspension bottom out. Part of my commute is at sub 25mph speeds on very patched asphalt, the 700s definitely communicate the imperfections. At those speeds the whole car moves with the bump. At highway speeds, its not bad at all, the suspension soaks up any rough stuff.

Somewhere between 600 and 700 is probably the sweet spot in my opinion.

One of the problems I heard is that the TCK and GC rear shocks really benefit from to be shortened so that they have greater shock travel when compressed under load. Aside from fairly hard RSM which make more noise as weather is cooler, my AST suspension really rarely ever feels like it hits the bump stops or bottoms out even when pulling an autocross trailer full of wheels and equipment.

[fmcfad01]

This leads me to believe that Ground Control really nailed it with their recommended spring rates for daily driving; 440f/660r, versus TC Kline's recommendation of 400f/500r.

Would it be crazy to use the GC rear short springs and adjusters with the TC Kline rear shocks? Getting into 660# rears seems like a happy medium between 600 and 700.

[f50nut]

Would it be crazy to use the GC rear short springs and adjusters with the TC Kline rear shocks? Getting into 660# rears seems like a happy medium between 600 and 700.

Don't see why not. You could also look into Swift springs. They offer a ton of rates and sizes.

[cfmistry]

This leads me to believe that Ground Control really nailed it with their recommended spring rates for daily driving; 440f/660r, versus TC Kline's recommendation of 400f/500r.

Strange, GC recommended 375f/475r for me. Also for daily driving. I ended up going 400f/500r by I think I need to step the rear up to 600+

[f50nut]

Strange, GC recommended 375f/475r for me. Also for daily driving. I ended up going 400f/500r by I think I need to step the rear up to 600+

I should have been more specific. I told them the car is street driven, goes on long trips but should hold up to spirited driving on twisty roads. That is usually how I set up a daily driver

[BenFenner]

I have my rear strut mounts mounted the way most people said to do it, with the bolts facing down. From the factory the mount was inside the car and the bolts were facing up. Seemed like a good idea at the time as it made it very easy to install and remove the shocks without having to struggle inside the car. Now as I am adjusting my rear ride height I again notice that at full droop there is no pre load on the springs.

Sorry for replying 6 months later, but I would hate to see you install those rear shock mounts inside the car. Look into these raised units instead?
http://www.ground-control-store.com/...ion.php/II=851

[dcrothers]

Sorry for replying 6 months later, but I would hate to see you install those rear shock mounts inside the car. Look into these raised units instead?
http://www.ground-control-store.com/...ion.php/II=851

Do these units let the rear sit lower by moving the shaft more into the interior ?
They look like they help me get my car a bit lower again without loosing comfort.

[BenFenner]

If you're talking about ride height, that is always controlled by the spring, and spring perches. No, these will not change ride height in any normal circumstance.

1) These allow folks with incorrectly long shocks to regain some shock travel.
2) Also they could help with especially low ride heights where the shock is bottoming out. (That is assuming you've removed your bump stops already.)
3) They also allow folks with short springs to maintain some preload when at full droop. (This is the issue jbrannon7 was having, which is why I suggested it.)

[95maxrider]

Hi everyone, sorry to bump an old thread but it seemed to be the most relevant to my question, so I figured I would give it a try.

I rallycross my 98 M3/4/5, and I need some advice about what to do with my spring rates when I remove both sway bars. The car is on JVAB offroad Bilstein-based shocks, and has/had stock sway bars. Front springs are 12" 250 lb, rears are 7" 350 lb (although I'm probably going to try and squeeze some 8" springs in there). I recently removed my FSB in an effort to get rid of understeer when on course (it helped), and I think I would like to also remove the rear to help me put down power and get better wheel articulation. I believe that I will need to raise my spring rates to compensate for the lack of sway bars, but I'm not an engineer and can't calculate how much I should change. If I had to guess, I would start with 300f/400r, but it's just a guess. Can anyone comment on how I should go about this? I can't exactly buy a bunch of different springs and try them all out, because that would be too expensive on my tight budget.

Thanks in advance!