Questions for the people in the know....

[Roger Poirier]

Ok guys,

I have been following tech info for about a year now. I'm going to list what I have done to the car. Please help me in determining what I did right and what might need to be corrected. This car is going to be driven on the street only, no track use. Your comments good or bad are appreciated. Remember I'm a rookie and have been using the knowledge of others on this board. Some of the tech threads are over my head. Cost has not been a concern on this project.

69 GTO Judge

Suspension

Factory frame
Global West front lower and upper control arms. D-bushings
3" lowering springs by OPG
QA1-Shocks
1 1/8 front sway bar
Factory B-Spindles from Baer

The top ball joints on the upper fronts contol arms were replaced by GW with smaller units. Less bulky (flatter). They said they were needed for the lower suspension height I was using. I really don't understand this one.

Global West rear lower and upper control arms. D-bushings except top of rear axle bushings are rubber.
3" lowering springs by OPG
QA1-Shocks
No rear sway bar

Note: 68-69 Factory GTO's sit higher in the front. I wanted to go coil overs, however, the adjustment was not enough to alter the ride height to where I now have it, which is 1" lower ride height in the front compared to the rear. That includes putting wheels of 18's in front and 20's in the rear.

Baer also supplied me with some big ass tie rod ends with their name on them.

AGR quick ratio steering box and pump.

Is my ride going to be harder then the factory ride?

I would think most of my wheel hop in the rear should go away?

Will I encounter more bump steer then a factory set up?

It's got to handle a whole lot better. Correct?

Feel free to ask me more questions if needed.

Thanks,

R.P.

[astroracer]

Hey Roger, I'll take a few stabs here...

Is my ride going to be harder then the factory ride?
Because of the bushing change it will be a bit harsher but there is also the spring rates to be considered and the series of the tires you are using. Stiff springs will make for a harsher ride as will low profile tires. You didn't list the rates or tire size so I can't say what you will have.

I would think most of my wheel hop in the rear should go away?
Can't say... Wheel hop is complicated issue and is dependant on spring rate and suspension geometry. I HOPE the GW stuff addresses this problem (you could ask them...) but you will have to tell us after you get the car on the road...

Will I encounter more bump steer then a factory set up?
Again, I can't say... Not enough info. Bumpsteer is determined by the suspension geometry in relation to the inner tierod pivots and, without knowing all of your points, it is impossible to calculate it. I hope GW did their homework on this point also but, with the changes you made there is no way of saying until you road test it or measure the points...

It's got to handle a whole lot better. Correct?
Not necessarily... Of course lowing the CG will make an improvement but the real factors here will be bumpsteer, caster trail, roll center migration and anti-dive. Spring rates will play a part as will the large sway bar in front and lack of one in the rear. There is really no way to predict how your car will handle without all of the info and driving the car will be your only recourse.

I know I haven't helped here but I had to let you know that the lack of info or real world testing will prevent making an informed prediction as to how your car will handle.
Mark

[Roger Poirier]

Astroracer,

Thanks for the info. I will check spring rates with OPG. I'm not sure they even know. I will also try to find out what type of ball joint GW put on the upper control arms.

Tire sizes are: Front 235.40.18 Rear 275.35.20

Tires: Nitto Extreme 555 all the way around.


I appreciate the comments,

R.P.

[Roger Poirier]

ASTRORACER,

Just as I thought. OPG does not know the spring rate of their low profile springs. Go figure.

The front upper ball joints are Moog part #K 6157. They are used on standard G-body designs.

What I'm getting from your response is that driving the car will give me my answers to my questions.

Thanks,

R.P.

[sinned]

Ride harshness is going to change...quite a bit primarily based on the use Del-a-Lum bushings in the rear control arms (about the worst thing one could use in that application, even worse than poly). Bump steer is going to be far worse than stock, it doesn't matter what else you do; the steering arms on the "B" spindles cannot be altered to fix their increased length and height.



All in all it should handle better albeit a little unpredictable due to the increased bump steer and the new mechanical bind the rear will have form the bushing choice.

[Roger Poirier]

Ride harshness is going to change...quite a bit primarily based on the use Del-a-Lum bushings in the rear control arms (about the worst thing one could use in that application, even worse than poly). Bump steer is going to be far worse than stock, it doesn't matter what else you do; the steering arms on the "B" spindles cannot be altered to fix their increased length and height.

All in all it should handle better albeit a little unpredictable due to the increased bump steer and the new mechanical bind the rear will have form the bushing choice.

Dennis,

Why does GW encourage it customers to with go with B-spindles. To create a better negative roll system only? When you say bump steer is going to be far worse then stock (which is a concern because of safety issues) should I have stayed with my stock spindles. What are my gains and losses with B-spindles vs stock spindles?

If I stuck with rubber bushings all the way around in the rear, what benefits would I have over a Del-a-Lum bushings? Just a better set of upper and lower rear control arms. GW was aware before my purchase this car was going to be street driven only and suggested the upper rubber bushings for the rear. What do you suggest?

Could you explain mech. bind? All I have ever felt back there is wheel hop, in a big way.

Thanks,

R.P.

[sinned]

Dennis,

Why does GW encourage it customers to with go with B-spindles. To create a better negative roll system only? When you say bump steer is going to be far worse then stock (which is a concern because of safety issues) should I have stayed with my stock spindles. What are my gains and losses with B-spindles vs. stock spindles?

I don't know why they recommend them, maybe they don't have a clue about suspension design or maybe they just don't care. Yes, stock spindles are far better (although still not ideal) than "B" spindles in terms of bump steer. The only thing the "B" spindles have over stock spindles is the negative camber gain in bump.

If I stuck with rubber bushings all the way around in the rear, what benefits would I have over Del-a-Lum bushings? Just a better set of upper and lower rear control arms. GW was aware before my purchase this car was going to be street driven only and suggested the upper rubber bushings for the rear. What do you suggest?

Rubber in the rear is better than GW bushings. Check this thread for some details link to lateral-g

Could you explain mech. bind? All I have ever felt back there is wheel hop, in a big way...

Mechanical bind is when the arms physically bind during movement, not like "sticking" while rotating but like trying to bend your knee backwards...eventually it WILL go, after it gets past the "bind".

An excerpt from a pretty great resource
For the rear I have done all the research that can be done, my current configuration is about as good as stock mounting locations are going to get you. I will at some point in the near future have a fully functional 3-link/PHB arrangement but in the meantime this works OK. Replacing the rear axle bushings with the Wolfe spherical bearing eliminates one source of bind. I also replaced the lower links with 19" swedged tubing and 3/4" rod ends. For upper links I am running Edlebrock pieces, they utilize a spherical bearing floating in a polyurethane receiver to limit the amount of NVH transferred to the chassis. Many will say "what about just replacing the bushings with polyurethane or polygraphite", don't do it. The laws of physics are pretty clear on this, the upper link must rotate and articulate simultaneously for the rear end to move up/down. If you run poly bushings and eliminate what little deflection was there before you remove one of the two necessary actions for proper suspension travel. Lost yet?? OK, the axle moves up and down and the upper arm SHOULD just move up and down also. Instead, it must rotate within it's mount because of the converging angle it is mounted at. This works because the upper links are made of very thin channel steel and used rubber mounts. These rubber mounts and channel links articulate quite well, they shouldn't but they do. Running bearings instead helps but you still run into kinematics issues.

[MrQuick]

Roger, if its a street vehicle you would be fine with poly's all the way around. Your will car probably never see the articulation necassary to have the bind be a problem. Also make sure they are properly lubed during assembly.

Dels' are very harsh on the street, added to the low profiles you are running.

You should fine tune your rear suspension points to fix your wheel hop problem...on the last A body I built I used the Hotchkis anti-hop bars and they worked nicely. That car was a equipt with a 350 hp big block and 295/60 on 15" rims. Also ran poly's all the way around and B body spindles.
Just a hard driven street car that saw some drag strip duty.Would not recommend hard road racing. Should be fine for a street cruiser.
Im willing to bet you will spin the tires before you hop.

[Steve Chryssos]

Roger,
In an effort to improve ride quality, do some research regarding rear tires with more sidewall. A quick search at tirerack.com yielded 4 or 5 tires measuring 275/40-20 and 295/40-20 (very tall).

A 275/40 will raise the back of the car approximately 1" as compared to a 275/35 (28.5" overall vs 26.5" overall). If you attempt to compensate for the added ride height by further lowering the car, suspension geometry will be affected. So you would have to accept a higher car, but the taller tires will also fill the wheelwells better.

Something to think about.

[Jagarang]

I didn't do the B spindle swap for the same reasons stated. Keep stock spindle with GW upper and lowers on the front and rears. 1970 Chevelle.

[Roger Poirier]

Check this thread for some details link to lateral-g

Darn it Dennis. This other thread you are referring to is what got me started on this thread. LOL. Well, I hope members read these tech articles. Lots to learn. It is my belief that 90-95% of all these pro touring cars on this forum are street driven only. With you tech guys being the exception to the rule.

Live and learn. The first thing I will do is drive the car this spring as is, get a few miles on it and determine the do's and don'ts of what works. Then adjust/change from there.

Thanks guys,

R.P.

[Roger Poirier]

Roger,
In an effort to improve ride quality, do some research regarding rear tires with more sidewall. A quick search at tirerack.com yielded 4 or 5 tires measuring 275/40-20 and 295/40-20 (very tall).

A 275/40 will raise the back of the car approximately 1" as compared to a 275/35 (28.5" overall vs 26.5" overall). If you attempt to compensate for the added ride height by further lowering the car, suspension geometry will be affected. So you would have to accept a higher car, but the taller tires will also fill the wheelwells better.

Something to think about.

Steve,

I tried multiple of tires and rim sizes. Finding 19 rims with a fatter profile tire was the idea. However, I had very poor rim selection. Thus I had to go with the 20's and 35's in the rear. The car look silly with 275/40 or 275/45 on the rear with 20's. It made the car look Pro-Street.

Just as in marriage. A lot of give and take to make it work.

Thanks for the tip,

R.P.

[Roger Poirier]

I didn't do the B spindle swap for the same reasons stated. Keep stock spindle with GW upper and lowers on the front and rears. 1970 Chevelle.

Now you tell me. LOL. What did you use for rear bushings?

R.P.

P.S. You and I are in a dead heat for last in getting our cars done before winter is over. Oh well. I have waited this long. LOL.