Running no rear sway bar on track?

[Tri-bar]

Incorrect.
The FR500S Rear Springs are 900-225-300.
Just sayin.

Just checked my build sheet, you are right.

 

[Stephen31201]

You can buy a coilover kit for the Konis from Ground Control. Everyone hates them on here, but if you run them at a reasonable height in the front with a decent spring they work well. Ran them all year lowered about 1.25" with a 550/300 setup. The 550s are a bit too much spring for them, would go with a 500 spring max, 450 would probably be better. I also went down to a 250 out back. Rears have plenty of rebound damping front is lacking.

You don't have to drop 4k to make the car work. I obviously would prefer better dampers and eventually will run them, but guys all over run Konis and this is the only place where I seem to see outright hatred. Hell the Griggs setup are just Koni DAs, and so are the Cortexs. Although they may have different valving and shorter housings, they are just yellows.

Mark has more experience with the GC's than I do but I agree. Not sure why everyone bashes them other than they expect the performance of a $3500 coilover set for $1700. I ran similar rates and the performance difference was great. Once I get to the point where I cant make up a single second on the track the high dollar ones may be the next step. I will also say that I am glad I had a year of track time on the stock suspension because it taught me how to handle and drive the car on the ragged edge to get every second out of it I could.

 

[Boone]

This was supposed to be a low buck/low maintenance recreational thing...boy, am I stupid.

OMG!!! You're ME!!!

This thread has morphed into a coilover discussion, so I'll just ask...

I have H&R Street Performance, and I believe I'm going to need more spring. The next step up in the H&R line is the RSS, and they are available in three spring rates F570 - R460; F630 - R515; and F715 - R600. I'm adding around 90 pounds to the front of my car with a BBB. Car is 80% street, 20% road course. I don't mind a stiff ride on the street, but don't want full race car.

Any suggestions on spring rates once I recover from my BBB wallet bash?

 

[Fabman]

OMG!!! You're ME!!!

welcome to the club...

 

[Fabman]

So, what I'm hearing is GC coil over kits with around 450/250 springs with the struts set full stiff....Norm seems to prefer the softer side for these struts, but this should be ball park...yes?

 

[Stephen31201]

I run stiffer spring rates on the GC,but I run front full stiff and rear almost full soft. But, thats just what works for my style of driving. You may get in my car and say it drives like a turd. lol.

 

[Mark Aubele]

I don't run the rears at full stiff, but you will be near or at full stiff up front. It's a decent setup for a little over 400, and when you want to upgrade should be pretty easy to unload. At 1" lowering there is still adequate travel with the factory bumpstops up front, in the rear its close but I would just remove the very top of the bumpstop in the rear.

 

[Fabman]

I run stiffer spring rates on the GC,but I run front full stiff and rear almost full soft. But, thats just what works for my style of driving. You may get in my car and say it drives like a turd. lol.

Sounds like we are more alike than not.
I always ran much stiffer front springs than my competition in the stock cars. My gut is telling me 500/300 but norm has me worried about having enough shock for the spring. I also always ran much lower roll centers than most. What I don't want though is any kind of push. Can't stand that. I'd rather be a shade loose and have to steer with the throttle than deal with a push. Neutral is nice with just a hint of oversteer is the ticket for me.

 

[Fabman]

I don't run the rears at full stiff, but you will be near or at full stiff up front. It's a decent setup for a little over 400, and when you want to upgrade should be pretty easy to unload. At 1" lowering there is still adequate travel with the factory bumpstops up front, in the rear its close but I would just remove the very top of the bumpstop in the rear.

Yes, stiff up front soft in the rear. My usual set up was (2150# tube cassis car) 350 or 375 or 400's up front (depending on the track) and 150 rear and a "6" valving up front with a "2" valving in the rear and a 1" hollow front sway bar-no rear bar. Shocks weren't adjustable, you just swapped the shock to another number.

 

[Mark Aubele]

Sounds like we are more alike than not.
I always ran much stiffer front springs than my competition in the stock cars. My gut is telling me 500/300 but norm has me worried about having enough shock for the spring. I also always ran much lower roll centers than most. What I don't want though is any kind of push. Can't stand that. I'd rather be a shade loose and have to steer with the throttle than deal with a push. Neutral is nice with just a hint of oversteer is the ticket for me.

500/300 with sway bars that are close to stock in front to rear balance will be crazy loose. My car with -3.5* camber up front, square 315 Hoosiers, 35/22 bars and 550/300 rates was almost undriveable on a road course it was so loose. Worked really well on very tight corners and autocross but was really hard to put power down on corner exit. Very possible this has a lot to do with the lack of rebound damping from the Konis up front though. Having them revalved or going with a different damper.

Give it a shot, but I think you will want a bit less spring. The ride is pretty brutal with 300s out back too, much better with 250s. Think it is more about front to back spring balance in regards to ride. On my original 350/300 setup the car was brutal, ride actually improved with a switch to a stiffer front spring.

If you do go with a 300, go with an 8" spring. Can only go down a bit over an inch with a 9" spring.

 

[Fabman]

500/300 with sway bars that are close to stock in front to rear balance will be crazy loose. My car with -3.5* camber up front, square 315 Hoosiers, 35/22 bars and 550/300 rates was almost undriveable on a road course it was so loose. Worked really well on very tight corners and autocross but was really hard to put power down on corner exit. Very possible this has a lot to do with the lack of rebound damping from the Konis though. Having them revalved or going with a different damper.

Give it a shot, but I think you will want a bit less spring. The ride is pretty brutal with 300s out back too, much better with 250s. Think it is more about front to back spring balance in regards to ride. On my original 350/300 setup the car was brutal, ride actually improved with a switch to a stiffer front spring.

If you do go with a 300, go with an 8" spring. Can only go down a bit over an inch with a 9" spring.

so, 500/250 then? I have the FRPP 35/22 bars and Hankook Ventus Z214's.
I always ran at least a 250# spring split before so that makes sense.

 

[Mark Aubele]

so, 500/250 then? I have the FRPP 35/22 bars and Hankook Ventus Z214's.
I always ran at least a 250# spring split before so that makes sense.

I honestly think that would be a better starting point. Although 500 is really pushing it for yellows, I ran 550s and the world didn't come to an end. Will be having them revalved this winter though. Been so nice I've been driving the car so much or I would've had them done already!

 

[Fabman]

I honestly think that would be a better starting point. Although 500 is really pushing it for yellows, I ran 550s and the world didn't come to an end. Will be having them revalved this winter though. Been so nice I've been driving the car so much or I would've had them done already!

so, 450/250 or 500/250?

 

[Fabman]

Looks like GC has a 475# spring...hmmmm.

 

[kcbrown]

kcbrown was able to get some shock plots off his own set, and I was looking in the 1 ips to 2 ips region. I don't think the comparisons would change much at 3 ips.

Max spring rate to maintain 65% critical damping in the front is around 415 lb/in for the Konis I have. I don't know how much smaller a percentage of critical you can go before the damping is compromised. 500 lb/in puts you at 60% critical when the rebound is maxed out, which might be considered sufficient.

What's unclear to me is how exactly to factor in the sway bar. If you assume the sway bar rate adds to the spring rate, then for the stock 34.6mm front bar, at 436 lb/in, you'd be looking at a total of 936 lb/in rate up front if you're already at 500 lb/in, which would put you at only 43% critical. That might not be enough.


I've set my rebound on the basis of the spring rate alone, and have my percentage of critical damping a little high, at around 75%. If I add the sway bar rate to my spring rate, my damper setting puts me at only 38% critical up front. Since Sam Strano's advice (which is based on a lot of real-world testing) has you setting the rebound to about the same settings that you'd set it to on the basis of spring rate alone, I suspect that the sway bars may not factor into the equation quite as much as one would otherwise think. It's probably a compromise.

I suppose the only way to really know for sure is to actually try it. If it doesn't work out, Koni can, I believe, revalve the dampers. I've no idea what that would cost.

 

[Norm Peterson]

Roll damping involves vehicle track as well as wheel rate and gets more complicated than just adding wheel rates.

I *think* the bottom line tends to be that you can use a smaller % of critical damping in roll. There are some equations in Dixon's "Shock Absorber Handbook" dealing with this, that I haven't put any real time into trying to understand.


Norm

 

[Fabman]

Roll damping involves vehicle track as well as wheel rate and gets more complicated than just adding wheel rates.

I *think* the bottom line tends to be that you can use a smaller % of critical damping in roll. There are some equations in Dixon's "Shock Absorber Handbook" dealing with this, that I haven't put any real time into trying to understand.


Norm

Crap....maybe I should just save up for the Vorshlag setup. Cortex claims you can get a 315 on all 4 corners with theirs....any thoughts on this?

 

[Mark Aubele]

315s all around. Konis with GC coilover kit. Running a bit more spacer up front that necessary. 18x10.5s 7.75" BS 3/4" spacer up front.

 

[Norm Peterson]

Crap....maybe I should just save up for the Vorshlag setup.

I wouldn't say 'crap'. It means that you can end up with a higher % of critical damping in pure roll than in pure ride for the same lb-sec/in dyno numbers. Sounds like a good thing to me.


Norm

 

[Fabman]

I wouldn't say 'crap'. It means that you can end up with a higher % of critical damping in pure roll than in pure ride for the same lb-sec/in dyno numbers. Sounds like a good thing to me.


Norm

Just sounds like I would be pushing the limits going in with no place to go....