Ride height lowering - front

decoupe

decoupe

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I want to lower the front height by about 20mm or 3/4" to compensate for the effects of removing approximately 90kg (200lbs).

My options are:
1.) to cut the springs (ST lowering springs) by 1/2 to 1 radius - cost $10 for cutting disc
2.) lower the perch by cutting and rewelding - cost $25 for disc and welding
3.) installing the coil over kit from Ireland Engineering - cost $400 for kit plus shipping and installation (currency reversal starting to effect purchasing from US!!!)

Cutting the springs (1) would be the easiest route but will have some effect on the ride and spring travel. Is this significant?

Lowering the perch (2) involves more work (the same amount as (3) the coilover kit) but will not alter the suspension other than height. No change to ride as it currently exists.

The coil over kit (3) is the most flexible in terms of adjustable height and choices of spring rates to accommodate the weight reduction. Tunable.

Whatever I do I'll post the results.
 
If your happy with the ride and comfort as it is, then number 2, I did this once on another car and it turned out great.
(just make sure that dropping the perch 20mm won't cause any clearance issues with the tyre)

Coil overs are great and offer lots of adjustment, bonus of being able to go the spring shop and change spring rates easily, but as you say, costs more.

Cutting springs is a bit hit and miss, and doing this makes the spring rate harder.
(having said that, I did cut 1/2 a coil of my fronts just the other day as I also wanted to drop the front just a touch)

Another option is to measure the existing spring length when compressed in the car( tricky to do, but not impossible )
Then take the spring to a suspension/spring shop that has a spring rate machine, they will compress the spring back down to this hight and find out what rate it is, from here they may be able to supply you with something off the shelf that will be approx the same rate or a touch stiffer, but the 20mm lower that your after.

Good luck!

This is what I did when I did the suspension in my car, I ended up running an aftermarket lowering spring for an Australian Holden commodore car
 
Thanks Steve, I wasn't aware of the "spring rate option" from a suspension shop. Have to see if there is someone in Calgary that does this.

Four options now.
 
I've had good luck with method #1. I think i ended up with about a 3/4" drop (on a stock weight car) after cutting one coil on each side in the front. The ride is just slightly firmer and i've had no problems with the cut springs falling off the upper perch . . . although i'm not sure what would happen if you cut more than one coil.

Top tip: if you don't want to disassemble the strut (who does) and you are doing a full coil it can be cut in place with a small die grinder. The strut assembly keeps everything in place during the operation. The cut coil just drops away after it is severed (ie. there is little or no spring tension in it).
 
Top tip: if you don't want to disassemble the strut (who does) and you are doing a full coil it can be cut in place with a small die grinder. The strut assembly keeps everything in place during the operation. The cut coil just drops away after it is severed (ie. there is little or no spring tension in it).
Click to expand...

To be honest I do a lot of unusual things when I'm working on a car, but never would cut a spring under tension still mounted in place.
This could end up in some problems if you have bad luck. In addition it doesn't work out at a E9 front spring, because you'll still need a squared end and you're producing a tangential one, if you just cut it and don't modify the end of the spring afterwards.

Of course it's not very nice for a spring if you heat the end to shape a squared end back again, but I did this a couple of times now and never had any problems with a soft or weak or broken spring for a couple of tenthousend miles . (always shock cooled them in an oil bath)

Actually I did this procedure to my coupe at the rears. Just removed half of a coil and now it suits me right.

For the front I went with lowering springs for the E12 series, which you'll get here in Germany between 120 - 200 Euros for all four. The rears won't be of any use, but I didn't find a supplier, who only sells seperately the front springs.

Driving together with bilstein shocks is pretty fine with this custom solution.

Height of the car is fine for my taste .....

IMG_4057_zps2359e3d2.jpg



cheers

Ingo
 
Thanks to all for the advice and experiences.

Having removed the weight (trying to get the car to 50/50 weight bias front to rear and the car under 3,000lbs), the front springs are carrying about 15% less weight so cutting a coil is off the list for me. Probably will go the lowering the perch height for now.

Incidentally, I was told that Suspension Techniques (ST) produced these spring sets for La Jolla Ind. as their in house brand lowering spring set. They no longer manufacture them for the e9 but do make the 28/23mm sway bar kit.

Doug
 
Cut the top or the bottom?

aalto said:
I've had good luck with method #1. I think i ended up with about a 3/4" drop (on a stock weight car) after cutting one coil on each side in the front.
Click to expand...
I'm curious.. did you remove the coil from the top of the spring or the bottom?

Also, if I remember correctly the springs sit on molded rubber blocks. Any fitting issues after the coil is cut?
 
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Stan, that is a nice garage though carpet probably isn't all that practical. From what I was told, the ST springs were a little firmer than the new LJI springs.

Take about 200lbs off the front wheels and your height will look like mine.
 
One nice thing about coil overs is that you can corner weight the car afterwards. Maybe another way to get the setup wrong, but it sure sounds nice.
 
decoupe said:
Stan, that is a nice garage though carpet probably isn't all that practical. From what I was told, the ST springs were a little firmer than the new LJI springs.

Take about 200lbs off the front wheels and your height will look like mine.
Click to expand...


Hahaha, not a carpet, a nice new paved driveway at the BMW Dealership in NH.
 
I had no luck with cutting front springs-they popped off the spring perch. In the rear cut springs work well for me.

In the front I use ground control coil overs, sitting on the stock perch so no welding required.
 
I wouldn't cut a front spring either, you have to cut a whole coil. The rears can be cut 1/2 coil but it will ride harsher, no way around it. My NK had cut coils and it rode like a conestoga wagon, it now has stock springs, what an improvement.
 
Barry et al,

Ultimately, looks like this will be a budget driven decision.

I need to direct the $$$$into a rebuild of a b35 head that needs lots of parts, all of which come through the US, and the exchange rate and shipping are starting to matter. I can cut and weld for next to nothing so dropping the perch will do for the short term and eventually do it again with coil overs.

In any case everything has to go back into the engine compartment before I can measure how much to cut (measure measure measure cut).

IMG_3362_zpsf88b9cd2.jpg
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Thanks
 
Re the Perch Kit Code: e9frtcoil from Ireland Engineering has anyone used it & can clarify for me....

- After the collar is welded on the strut, and the threaded sleeve is placed on top - what keeps it secured in place?
- Unless I select different spring lengths, how do I adjust the coilover length / ride height? I imagine after building, I would adjust the collar to +/-5mm up to slightly grip / compress the spring and set the pre-load. Surely I could continue to adjust further and yes that would in turn adjust the ride height. But, I cannot see how you can adjust the height without also compressing the spring & adjusting the pre-load...
 
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