[apexit53]

Photos up!

[atx_traveler]

looks pretty nice. can't wait to hear your impressions on how they work.

[DaveC113]

Looks like a great value. You going CAMC @apexit53?

[apexit53]

Originally Posted by DaveC113

Looks like a great value. You going CAMC @apexit53?

If anything I’ll go Stu.

One thing I noticed. Cause these have steel body’s. They feel quite heavy

[ZeroC]

Get them in yet I'm looking to go coil overs

The distance between my koni yellow stut perch and tires makes me super sketched out

[apexit53]

Originally Posted by ZeroC

Get them in yet I'm looking to go coil overs

The distance between my koni yellow stut perch and tires makes me super sketched out

I have not. Probably going to sell them soon. Wanted to get them on a shock dyno but not sure ill get there.

[apexit53]

So Very cool. Koni reached out to me via instagram late last week. Asked me how i liked them and looking for some feed back. Told them i have not got them on the car and as its winter soon probably wouldn't. They gave me an engineers name and info to ask them questions. The main one I had, spring rates...

front 300
rear 1000...

I asked why such a wide range. I guess the internals are similar to a koni sport. So you could potentially go with different rates.

I am sending my shocks to ASM here in Wisconsin. He has a shock dyno and we are going to see if there is a more functional or better spring pack we can get to work on these for autocross.

[Msquared]

Originally Posted by apexit53

So Very cool. Koni reached out to me via instagram late last week. Asked me how i liked them and looking for some feed back. Told them i have not got them on the car and as its winter soon probably wouldn't. They gave me an engineers name and info to ask them questions. The main one I had, spring rates...

front 300
rear 1000...

I asked why such a wide range. I guess the internals are similar to a koni sport. So you could potentially go with different rates.

I am sending my shocks to ASM here in Wisconsin. He has a shock dyno and we are going to see if there is a more functional or better spring pack we can get to work on these for autocross.

You probably know this already, but:

• The ZL1 1LE rates are 450 front and 1100 rear, which is a ratio of .409.
• The SS 1LE is 178 and 539, for a ratio of .330.
• The regular SS is 137 and 577, for a ratio of .237.

So as the spring rates go up, the stock front spring rates get relatively stiffer compared to the rear rates. I'm not totally sure why. Of course the sway bars comprise a bigger proportion of the total roll stiffness with the softer springs, and the SS 1LE has the stiffest stock sway bars of them all. It's also probably safe to assume that with all the extra power the ZLE has, Chevy wanted to ensure it had good rear traction and safe understeer coming out of corners.

With a front/rear spring rate ratio of .300, the Koni springs you have slot in between the SS and the SS 1LE in terms of relative front stiffness. I'm not totally sure what I'd want to change there, if anything. Also keeping in mind you probably still have the BMR front bar on a shelf, so you can tune in more understeer if you want, maybe 300/1000 isn't too wild. It would also be reasonable to experiment with a 400lb front spring rate, though.

[FactoryMatt]

Keep in mind those ratios are skewed due to the OE split spring setup. Really need to look at total wheel rate to compare.

I think these cars are sensitive to ultimate total rear rate and there's probably some derivative ratio of spring rate to corner weight where the rear gets leveraged really quickly due to the lack of weight back there. I.e. the wheel rate bias needs to match the f/r weight bias to a reasonable degree.

[Msquared]

Originally Posted by FactoryMatt

Keep in mind those ratios are skewed due to the OE split spring setup. Really need to look at total wheel rate to compare.

It doesn't change the comparison between the three stock springs sets and the Koni set, but comparing wheel rates does make it simpler to see what the springs are really doing, and it's just better form. So we're just multiplying the rear spring rate by 0.56^2 (motion ratio X lever arm), which is 0.3136. The front spring motion ratio is 1:1 or very close. Therefore we get the following F/R wheel rate ratios:

• ZL1 1LE: 1.3
• SS 1LE: 1.05
• SS: 0.76
• Koni GTS: 0.96

The Koni springs are still fairly close to the SS 1LE's, so maybe not a crazy starting point. 330lb front springs with the 1000lb rears would give exactly the same wheel rate ratio as the stock SS 1LE. You'd need 408lb springs to emulate the ZLE's wheel rate ratio, but again I'm not sure that's the right target.

One thing that I just thought about, though, is that if Mike enters STU, I presume he'd be using a "square" wheel and tire size, (11" wheels). With higher front grip from the wider front wheel and tire, that probably means you want a little higher F/R wheel rate ratio than the SS 1LE comes with. So maybe a 350lb or 375lb front spring would be the best starting point, which puts it in between the SS 1LE and the ZL1 1LE.

I think these cars are sensitive to ultimate total rear rate and there's probably some derivative ratio of spring rate to corner weight where the rear gets leveraged really quickly due to the lack of weight back there. I.e. the wheel rate bias needs to match the f/r weight bias to a reasonable degree.

Maybe. It depends what you're trying to achieve. This stuff is all complicated by various other things, including sway bar rates, roll center and CG heights, roll center migration, and so on. That said, the SS 1LE (Mike's car) has a weight distribution of 54/46, for a F/R ratio of 1.17. So it slots in between the SS 1LE's and ZLE's wheel rate ratios. The 350lb front spring I mentioned above gets you a ratio of 1.11, and a 375lb spring gets you 1.19, which brackets the weight distribution nicely.

[apexit53]

Originally Posted by Msquared

You probably know this already, but:

• The ZL1 1LE rates are 450 front and 1100 rear, which is a ratio of .409.
• The SS 1LE is 178 and 539, for a ratio of .330.
• The regular SS is 137 and 577, for a ratio of .237.

So as the spring rates go up, the stock front spring rates get relatively stiffer compared to the rear rates. I'm not totally sure why. Of course the sway bars comprise a bigger proportion of the total roll stiffness with the softer springs, and the SS 1LE has the stiffest stock sway bars of them all. It's also probably safe to assume that with all the extra power the ZLE has, Chevy wanted to ensure it had good rear traction and safe understeer coming out of corners.

With a front/rear spring rate ratio of .300, the Koni springs you have slot in between the SS and the SS 1LE in terms of relative front stiffness. I'm not totally sure what I'd want to change there, if anything. Also keeping in mind you probably still have the BMR front bar on a shelf, so you can tune in more understeer if you want, maybe 300/1000 isn't too wild. It would also be reasonable to experiment with a 400lb front spring rate, though.

Good point! I did not know that about the stock rates!