Ive almost got all the parts to rebuild my rear suspension and was wondering what size sway bars should go on. Rear is most important since im doing that now, front will probably be done next year.

The car has a 19mm rear bar stock and I want to buy the 26mm rear bar VBP offers. Next year or sooner Ill upgrade the front to a 32mm. Is this a good idea?

Thanks :seeya

 

Be carefull!

Front and reaer pairs work in unison. If you do one you have to do the other.

A 26mm bar on the rear is veru extreme for even high speeds on regular twisty roads, May be okay for autocross tracks where you have lot's of room
to recover when the back end tries to comr around to the front.

Best combo seems to be 30mm front. 24mm rear for high speed road driving.

But don't change the rear bar without doing the front also, Doing so will alter the handling negatively

jack

 

If you upgrade the rear without doing the front first, you will notice the rear coming around on you in corners.

Its always preferable to do the front first, or to not put a bigger bar in rear than is in front now. Any more than 26mm is too big unless yours is a dedicated race car.

 

:iagree: Used to autocross an RX7. Changed rear springs, shocks and bars first. I about lost the car going under a freeway underpass, testing it out, going to fast when the rear slid out and put me in a 180. Front first, then rear or wait to change bar until you have front one to go on.

 

yikes :eek: I never knew it could effect the car that way, I thought I should consult the forums collective wisdom before I made the purchase. Thanks you all have saved me some heart ache.

Well seeing how I was only going to do the rear, that VBP only sells those large mm bars, and I already have a bushing set for my current bar, Im just going to save my money for later and keep the current bar.

Thanks again guys :flag :seeya :steering:

 

I do not agree that front and rear bars MUST be changed
at the the same time but you DO need to understand how
they work together and make changes with this in mind.

With all else the same, increasing the rear bar increases
the tendency for over-steer (in the extreme, this is where
the rear end breaks loose first). Increasing the front
increases the tendency for under-steer. You seldom hear
of people decreasing bar dia at either end (perhaps because
of a perception that body roll must be limited at all costs)
but decreasing dia is a legitimate approach, too.

Changing dia at one end only is a form of suspension tuning.
If you have a car that understeers (plows) you can move the
characteristics toward balanced/neutral handling by increasing
the rear bar dia (or by decreasing the front bar dia) in
moderation.

However, your 19mm bar is apparently the smallest production
C4 bar and a 26 mm is the largest. As already noted above
the 26 mm (solid) rear bar was only used with the 30 mm (oops - solid)
front bar except for ZR1 (different f/r track widths, different
wheel size combos and maybe diff f/r weight balance) and
apparently for the Grand Sport (FE1, F45 & Z51 - Z16's w/ 11"
rears) offered in 1996.

Jumping from a 19 to a 26 with no other changes would probably
create a significant increase in oversteer. But in between these
extremes, there are 20, 22, 23 and 24 mm bars that were installed
during the prod'n run. There is a good chance these bars and their
bushings are still available from GM, possibly at trade price or better.
If not, the aftermarket is likely to offer some or all of the middle
dias. Don't overlook 'previously-owned' bars from the forum,
recyclers or elsewhere. As long as they haven't been bent (?)
or torched, used bars will be fine in my opinion.

The advice about making changes in pairs and increasing at the
front first is good advice, esp for people starting out in this area
BUT it is NOT set in stone. This practice can be more costly in time
and parts and it may not lead to the desired outcome. If you
take the time to determine what it is you are trying to achieve,
make incremental changes in the appropriate direction and test the
results in a safe environment, you will get the best results.

FWIW - I DECREASED my rear bar (more understeer) to deal with
a tendency toward trailing throttle over-steer at a high-speed
transition from a serpentine into a sweeping left turn. This had a
negative impact on one 180º turn which I deal with by entering
slower and applying power differently. It had a positive effect
at the serpentine mentioned above and at other areas on the track.
I COULD have achieved a similar result by increasing the front dia,
but this is a street car and I did not want to decrease compliance
because of local road conditions. (I also might have addressed
the original problem by learning how to drive differently )

This chart by Hib Halverson may be of use

http://zr1.net/ZR1_suspension.html

The racing/autocross forum is a rich source of information.
Search on 'sway' and post any questions that have not
already been answered

http://forums.corvetteforum.com/zerothread?id=129440


Test where it is safe, backing up into a guardrail (or oncoming
traffic !) at speed can spoil your entire day.




[Modified by Slalom4me, 12:54 AM 7/27/2003]

 

I use the 30/26 solid bars from chevy...same as their Z07 sizes. I don't have enough seat feel to tell anything other than that the car feels better and the ride is more firm-exactly what I wanted.

I find it hard to believe 90% of us (even 90% of us on the forum) can really detect a few mm of sway bar difference. I trust GM's R and D. :)

As far as loosing control of your car on the street...that really takes some work...kind of like the article from a friend in San Diego about some 23 year old losing control of their Porsche and launching it off an over pass...

The cost was ~$160 from Jeff Kopp for both bars. Awesome deal.

 

No Go -

I copied the parts numbers from your site, but do you know what years the two (30, 26) bars fit???

 

The 30/26 bars will fit 88 and up. The front for sure is different for 87 and earlier, but not sure on the rear bar.

I have these paired with stock soft FE1 springs and Koni shocks (set on full soft).

Seems to work.

:)

 

Thanks, I inadvertently described the 30 mm as tubular.

Judging from your sig, your car has considerably more rwhp than
my 'stock' '89. Perhaps the difference in torque characteristics explains
the difference in our opinions on this point. I don't think it is that tough
for someone to get in over their head on the street with these cars.
The unexpected is always just around the next corner and if you make
a mod that dials in a good dose of oversteer and aren't aware of it,
you stand a chance of trying to swap ends in an emergency lane-change
or having the rear come around when you power up an on ramp.

Porche - a legacy of being unforgiving at their limits and a predilection
for traveling backward when they let go. The perfect gift for a college
student <sarcasm>.



[Modified by Slalom4me, 1:19 AM 7/27/2003]

 

Gentlemen...

(uh, oh - he wants something...) ;)

Does anyone know the OEM GM stock numbers for the 30mm solid front and 26mm solid rear bars for a 1986 convertible???

I have the parts book, but it does not list the bars in a consistent manner. It mentions several RPO codes; indicates separate #'s for verts; does not list sizes at all; and does not say if solid or tubular.

Thankyouverymuch... :D

 

I'm pretty sure the bars were available on Z51 cars. The parts books I've seen don't go by that code, but rather another one...such as FE7. You may try that one.

Also I remember seeing here that the early model 30 mm was no longer available-reason why some were going with Vette Brakes 32 mm.

Poly bushing on the sway bar attachment point really help make the bar quicker reacting as well.

:)