Well, spring rates and understeer, who knew?

zaxrex · Post by **zaxrex** » Sat Jul 16, 2005 1:21 pm

I recently replaced my rear springs with more liveable springs from my pre-accident Tein Flex 1st gen setup. The 2nd gen setup is a very harsh 10/8 kg/mm. I only had enough time to do the rears, so I replaced the 8 kg/mm springs with 5 kg/mm ones and left the fronts as they were.

I had changed what used to be neutral to slight understeer to a more stock level of understeer under power. If I let off or tap on the middle pedal, it tracks back on line with the front wheel direction or mild oversteer. I have heard about rear role rates and all of that, but this was a real eye opener to actually feel the difference and see the effects of unbalanced spring rates/weight distribution.

Post by **Sabre** » Mon Jul 18, 2005 12:59 pm

zaxrex wrote:I have heard about rear role rates and all of that, but this was a real eye opener to actually feel the difference and see the effects of unbalanced spring rates/weight distribution.

I think it's time I get another ride....

Tarmac02 · Post by **Tarmac02** » Mon Jul 18, 2005 3:51 pm

See... I don't even know why most manufacturers set up there spring sets and coilovers the way they do(Well I do and the answer is comfort). Cars see more of a traction benefit from the rear springs being stiffer than the fronts. I'm not saying that a car can't handle great with 10k/8k but the benefits of increased negative camber aren't seen as much because the front won't squat to take advantage of that contact patch.

John Mueller at Road Race Engineering is a suspension Guru. I've known a few other that run this also. The best handling track car's I've been in all ran something like a 6k/9k, 8k/10k. I'll try to find a writeup on it in the AWJ or SCE archives.

If you look at the Evo Orgy issue from SCC last year you'll see the spring rates on the best handling cars there all have stiffer rear spring rates.

The even wider imbalance of spring rates your vehicle is now showing is just a larger example of this.

I'm picking up a set of Hipermax II coilovers and if I have the extra cash at the time may get some custom springs, probably 6/7kf-8/9kr

Tarmac02 · Post by **Tarmac02** » Mon Jul 18, 2005 9:24 pm

Blak94GSX wrote:Basically the spring bias front to rear controls the balance of the car. The more spring rate, the less grip. If you want the car to understeer more, put more spring up front... Is as simple as that...

As to why most vendors have their springs backwards, I don't know...

-Springs control balance front to rear
-Sway bars control balance with lots of steering input (low speeds)
-Shocks control ride quality and should be matched to the springs
-Tires control grip and steering response

Oversimplified yes, but these are the fundamentals.

This is quoted from Scott Gray> If the name sounds familiar it's because he ran his GSX in the past 2 of SCC's USCC. Good guy and very knowledgeable. I can elaborate more but this is pretty cut and dry. On a side note Scott's 05 Evo made 348awhp on a DynoJet recently using simple DSM tricks. Turbo Back Exhaust, 255 Walboro FP, Denso 720cc Injectors, Dejon MBC, HKS 272 cams, and SAFCII. Not too bad for around 3k of mods.

gsx-lex · Post by **gsx-lex** » Mon Jul 25, 2005 4:45 pm

you'd be surprised what those 272's can do to a 4g63.

Tarmac02 · Post by **Tarmac02** » Tue Jul 26, 2005 1:23 am

yeah ... Deiter's car made 383 tq with a stock 03 turbo and 280 cams

zaxrex · Post by **zaxrex** » Tue Jul 26, 2005 2:34 pm

Yeah, but did it idle with those cams?

I put the softer springs on the front. Now I can drive around with passengers w/o having them sign a medical waiver for kidney damage. Now I need to put some sway bars in 'cause I'm not used to this body role.

drwrx · Post by **drwrx** » Tue Jul 26, 2005 3:05 pm

The real issue with the 272 cams is getting it to pass a sniffer test with them in. Damn near impossible, even with a super lean tune and alcohol.

Post by **Sabre** » Tue Jul 26, 2005 3:17 pm

drwrx wrote:The real issue with the 272 cams is getting it to pass a sniffer test with them in. Damn near impossible, even with a super lean tune and alcohol.

And in CA, that's just going to be that much harder!

Tarmac02 · Post by **Tarmac02** » Tue Jul 26, 2005 9:30 pm

sabre wrote:
drwrx wrote:The real issue with the 272 cams is getting it to pass a sniffer test with them in. Damn near impossible, even with a super lean tune and alcohol.
And in CA, that's just going to be that much harder!

seen it done with 264/272 combo... with some afc and boost adjustments...

haven't seen it with 272s yet

gsx-lex · Post by **gsx-lex** » Fri Jul 29, 2005 1:17 am

drwrx wrote:The real issue with the 272 cams is getting it to pass a sniffer test with them in. Damn near impossible, even with a super lean tune and alcohol.

Maryland only does the OBDII scan test, if they ran the sniffer on my car, i'd be in a lot of trouble

DCAWD.com

Well, spring rates and understeer, who knew?

Well, spring rates and understeer, who knew?

Re: Well, spring rates and understeer, who knew?