froggy47

I have been "told" by VERY KNOWLEDGEABLE people and even read in a couple of books on suspension that putting too much front bar vs. rear bar will result in MORE UNDERSTEER.

Fred Puhn in How to Make Your Car Handle pg.149 says "On cars with similar f/r suspension designs the tendency is for a stiffer front bar to cause more UNDERSTEER due to increased weight transfer in the front"

Well I put a T1 bar (37mm I think) on the front of my 04 with stock (27 mm?) rear bar and I gotta tell you the front was planted like an oak tree.

I could turn that sob any way I wanted and it was "Please sir may I have another?" (Dickens reference).

Rear was loosy/goosy til I softened the shocks and tire pressure & then was manageable but still loose on entry/mid/exit.

So what the hell is up with this?

Kumho 710's aggressive autox align. Dry 55F asphalt lot.



Anyone have a reference that is specific to c4/5/6 vette and set up?

TedDBere

Ummmmmm...not driving fast enough?

davidfarmer

In general, the stiffening adds relative grip to the opposite end of the car, but it's not always cut and dry.

Since the stock setup is relatively stock, any increase in stiffness could still improve overall grip. Also, without changing springs, the bars are just one link in the chain.

I don't know anyone whose tried every combination of parts to figure out a perfect setup (although I bet Danny P has tried most of them), but my philosophy is to simply drive thatever I've got till' the wheels fall off, no matter how crappily it handles!

froggy47

Fast enough that the rear was coming around (as I posted). Front just had mega grip & it was a puzzle.

SS winner 55.1 (z06)

My time (time only runs) 55.2 (z06), with my good a6's would be at least 1.5 sec faster. I had 1/2 gone 710's on.

TedDBere

Well, if you can get the car to rotate with the big bar then stay with it. But I have a hard time believing you can't run faster with a different set up. Usually you have to heavy trailbrake to get a C5 with a big front bar on it to rotate. Kind of like a Camaro.

froggy47

Actually I do left foot trail brake (maybe too much) so that could be it.

rustyguns

38mm front and 26 mm rear ! love it!

ltborg

Normally stiffening one end of the car (through spring or bars) results in that end of the car having less grip. In your case, stiffer front bar most of the time means more understeer, like you said.

There are cases however where there is simply not enough roll stiffness at one end of the car. When you see cars picking up inside tires, that is a case where you might need more roll stiffness at the opposite end of the car. For example if you pick up a rear wheel, you need more front bar to keep the rear tire on the ground since the body is rolling too much. You could soften the rear, but in Solo II stock classes, you can only stiffen the front, and it seems to work for people.

It could also be that the the suspension is moving too far out of its designed operating range. This can mess with the tire's orientation to the road surface and can decrease the grip excessively. Reducing the roll of the car body keeps the suspension within the optimal range of the suspension and can increase the grip of the car. The optimal range mean keeping the tire in an acceptable camber situation or keeping the suspension off of the bump stops (this would increase the stiffness much more than a stiffer bar).

Hope that makes some sense.

JiminVirginia

I believe it. This is the same experience I've had with my ESP Mustang Bullitt--the stiffer front bar really planted the front end. I think these kinds of results are actually fairly common in the autocrossing community, though not necessarily on a C5 Vette. The rational is that you're doing a better job matching camber to body roll and getting more tire down on the pavement.

I'm hoping for similar results on my C6Z next season. I've installed the adjustable Pfadt bar up front. Time will tell.

ericstanley

For what it's worth. I believe the winner you're talking about has a Pfadt Pfatty front sway bar, stock 2004 z06 shocks on stock alignment with new-ish A710s. I have stock 2002 z06 shocks, stock bars, stock alignment and thoroughly destroyed A6s. I ran a 54.995 on a run that didn't count, and my best time that counted was 55.639.

froggy47

RX7 KLR

I am with Ted, to slow....

AS 52.1
ES 54.8

SS was WAY off the pace. Come on Bob, stop playing with parts and use the pedal on the right.

btw if you are testing new parts/setup using old tires you are wasting your time - as soon as you put on new tires everything you did on the old ones is useless.

Solo2GS

Having run a season with T1 (front 38.4mm & rear 27.5mm ) bars, because that was what I had and no budget to change, I think the front bar is a bit too much for Auto-x. Many others with more experience have suggested Hotchkiss (32mm) or even ADDCO 32mm or 35mm from bar in its place.

Although it was fast, I felt the front push when trying to go faster as an ASP car should go...

I will likely try a new front bar and keep the rear T1 bar as its almost the same size as the rear Hotchkiss bar

Another simular thread along this line...

All second hand info, mostly collected from the forums here.

Swaybars:
C5 Base Suspension: 23 mm-front / 19.1 mm-rear / 3.81mm/2.0mm thickness
C5 Z51 (97-99): 25.4 mm-front / 21.7 mm-rear
C5 Z51 (00-04): 28.6 mm-front / 23.6 mm-rear / 4.15mm/3mm thickness
C5 Z06: 30.0 mm-front / 23.6 mm-rear / 4.5mm/3.5mm thickness
C6 Base: ?? mm-front / 22.0 mm (7/8")-rear
C6 Z51: 31 mm-front / 25.4 mm (1")-rear
C6 Z06: 31 mm-front / 28.8 mm-rear
C5 Hotchkis: 31.75 mm-front / 25.4 mm-rear / 4mm/4mm thickness
C5/C6 Addco: 32 mm-front / 25.4 mm-rear
C5/C6 Addco: 35 mm-front / 25.4 mm-rear
C5 Pfadt (Adjustables): 32 mm-front / 26 mm-rear
C5 Pfadt (Adjustables): 35 mm-front / 28.5 mm-rear (Pfatty)
C5 T1 (GM Racing): 38.4 mm-front / 27.5 mm-rear / 6.35/6.35 thickness
C6 T1 (GM Racing): 38.4 mm-front / 27.5 mm-rear / 6mm/?? thick