Results of TC Kline spring rate experiments in Z3 Coupe

[bluptgm3]

TCKline himself has stated not to run them ‘full soft’

[ddbaker3]

Sorry to revive this thread, I really appreciate all of the research that has gone into this topic.

My coupe is my only car and I'm commuting in it 95% of the time, about 50 miles a day. I upgraded to Koni/H&R, but it's too low and I don't feel like I can enjoy it with all of the construction around me. If I just want better handling over stock and the ability to adjust ride height, does the 300/700 combo still sound reasonable or possibly too stiff for the rear for my driving habits?

[IndianaRoadster]

Sorry to revive this thread, I really appreciate all of the research that has gone into this topic.

My coupe is my only car and I'm commuting in it 95% of the time, about 50 miles a day. I upgraded to Koni/H&R, but it's too low and I don't feel like I can enjoy it with all of the construction around me. If I just want better handling over stock and the ability to adjust ride height, does the 300/700 combo still sound reasonable or possibly too stiff for the rear for my driving habits?

This is where personal preference comes in. I personally think it would be fine, though I'm bias toward handling.

[dantheman7913]

Oh and thanks for the update! Do please report back if you swap springs again. Just to confirm--what are the spring rates on the springs you installed this weekend?

I’m back with an update! 7k front springs, 16k rear springs! Swift brand, and I got some 12.9 grade bolts for the lower shock bolt from Bavarian Metal Works as a precaution. I could have sworn Swift sold a 4inch spring but apparently not, still unable to use the rear height adjusters. However the new springs ride great, at all levels of adjustable stiffness the car isn’t bouncing which is a huge improvement from the hilarity of putting it on full stiff with the 14k springs (turned into a trampoline). Ride quality is also fine, on full soft it is compliant but still planted, and i can drive it around town on half-stiff and it feels fine imo.

[kornfeld]

Sorry to revive this thread, I really appreciate all of the research that has gone into this topic.

My coupe is my only car and I'm commuting in it 95% of the time, about 50 miles a day. I upgraded to Koni/H&R, but it's too low and I don't feel like I can enjoy it with all of the construction around me. If I just want better handling over stock and the ability to adjust ride height, does the 300/700 combo still sound reasonable or possibly too stiff for the rear for my driving habits?

Given that you say this is for commuting 95% of the time; and you're dealing with construction; it sounds like your question about whether this is "too stiff" is in regard to hitting bumps in the road, and not about it being too stiff in handling characteristics during cornering. If that is correct, then know that the springs are not what make the car too stiff or not. The dampers themselves are what make the car feel jarring if they are too stiff.

It's very important to understand that the 700 pound spring in rear is absolutely NOT an overly stiff spring back there. The numbers 300 and 700 give you that illusion, which is what started this whole thread in the first place. If you buy those springs, they'll actually end up being ~264 pound springs in front and ~315 pound springs in the rear because of how our suspension works.

I'm not a suspension expert, but every single piece of information I've read about suspension tuning pointed toward the 300 pound spring up front and the 700 pound spring in rear; and my own personal experience showed that to be the best combo.

- - - Updated - - -

I’m back with an update! 7k front springs, 16k rear springs! Swift brand, and I got some 12.9 grade bolts for the lower shock bolt from Bavarian Metal Works as a precaution. I could have sworn Swift sold a 4inch spring but apparently not, still unable to use the rear height adjusters. However the new springs ride great, at all levels of adjustable stiffness the car isn’t bouncing which is a huge improvement from the hilarity of putting it on full stiff with the 14k springs (turned into a trampoline). Ride quality is also fine, on full soft it is compliant but still planted, and i can drive it around town on half-stiff and it feels fine imo.

Awesome to hear!

[ddbaker3]

Thanks for the reply Kornfeld, I guess I’m kind of glossing over all of the science behind the spring rates and how the dampers influence things. I am happy with the Koni/H&R as far as ride/comfort/stiffness goes, but I need to raise the car up for everyday driving.

It seems like the 300/700 combo would keep what I like about the current setup while letting me lift the car 3/4” or so. I appreciate all the time that everyone has spent on this topic and thankfully the rear springs are much easier to swap out. I trust you guys and I’ll report back as another data point

[MartyBtoo]

You need to ask about the installed height of the springs. It could be exactly the same, which would mean you wouldn't get any increased height.

Marty

[rasmuw]

Maybe you can find someone who wants to lower their car from stock and wants to trade for your springs.

[bluptgm3]

In OE form, the Z3 M and 1996+ M3 share the same front Spring Pads
Stock Lower
SPRING PAD UPPER 3MM 31332227902
Canadian Cars Lower Option
SPRING PAD UPR 9MM 31332227901


Not sure IF you can run any of these w/CoilOvers
I believe the Z3 uses the upper for the lower and vice versa
E36 Rear Spring Pads
SPRING PAD LOWER 33531135420
UPR SPRING PAD 5MM 33531136385
UPR SPRING PAD 7,5MM 33531136386
UPR SPRING PAD 10MM 33531136387
UPR SPRING PAD 15MM 33531094754
UPR SPRING PAD 21,5MM 33531091599

[ddbaker3]

I went ahead and ordered TCK Single Adjustable 300F/700R and I'm excited to see how it feels. I did confirm with them a while back that I could run these without really lowering the car at all if I wanted.

I had stock springs on the Koni shocks for a while and I wasn't a huge fan personally. With the Koni's being shorter, it also didn't feel right that the stock spring had to be compressed so much just to get the top mount on. And for spring pads, there was a different thread on here talking about different thicknesses and possibly stacking them to achieve a certain ride height. Maybe others have had some luck with that method, but it seems like a lot of trial and error

[rf900rkw]

Some do a bit of math before selecting the spring pads.

[kornfeld]

You need to ask about the installed height of the springs. It could be exactly the same, which would mean you wouldn't get any increased height.

Marty

+1 to this---I can't speak to the height you'll get. I have the TC Kline adjuster things, and I think I can get the car pretty elevated with them, but I can't give any hard numbers or anything like that.

- - - Updated - - -

I went ahead and ordered TCK Single Adjustable 300F/700R and I'm excited to see how it feels. I did confirm with them a while back that I could run these without really lowering the car at all if I wanted.

I had stock springs on the Koni shocks for a while and I wasn't a huge fan personally. With the Koni's being shorter, it also didn't feel right that the stock spring had to be compressed so much just to get the top mount on. And for spring pads, there was a different thread on here talking about different thicknesses and possibly stacking them to achieve a certain ride height. Maybe others have had some luck with that method, but it seems like a lot of trial and error

Be sure to report back!