Nice street performance suspension

[Derek Greenwood]

I am working to build a very nice street suspension setup on my 72 GT. I don't want to go too stiff as I am not planning to race it. I want a suspension that is nice to ride in yet handles well. It must be lowered as I really like the look of a lowered GT.

I am considering the following:

1. OGTS intermediate spring (the one that doesn't lower it very much) and then add lowering shackles to put the front end 2 inchs down. The shackle will allow the front suspension to move without binding.

2. Cut down the stock rear spring to match.

3. Put on Addco swaybars. These are softer then the OGTS ones so will allow some body sway. I found the OGTS sway bars to be pretty harsh for a street car when I had them before.

4. Lower the rear pan hard rod some and make sure the bar as level and the correct length.

5. Either use Koni Red shocks or the Rancho 9000 adjustables. I would like input on anyone who can tell me how the Konis and the Ranchos will compare. I like how easy the Ranchos can be adjusted. If Bob L. sees this which Rancho's would you use in this application or would you use the Konis?

6. I will put heim joints on the tie rod ends and then drill the hubs. Then mount the joints on the other side to correct bump steer.

7. I want to add an upper shock tower cross brace.

8. I will also put in probably soft poly bushings.

9. The wheels will either be 15 x7s or 15 x8s. If they will fit ok I will use 215 50 15s

What do you guys think? Remember I am looking for a firm OEM kind of ride.

Thanks for you input in advance.

Derek Greenwood
72 GT

[RallyBob]

1. OGTS intermediate spring (the one that doesn't lower it very much) and then add lowering shackles to put the front end 2 inchs down. The shackle will allow the front suspension to move without binding.

Just be aware you will have to cut 1/2 to 3/4 of the bump stops down or they will rest on the a-arms and effectively become your springs!

2. Cut down the stock rear spring to match.

Cut from the bottom coils BTW, so the top rests evenly.

3. Put on Addco swaybars. These are softer then the OGTS ones so will allow some body sway. I found the OGTS sway bars to be pretty harsh for a street car when I had them before.

The best thing you can do with most sway bars to make them more comfortable riding yet non-deflecting is to upgrade the poly end bushings to heim joints. Poly binds too much and hurts the ride quality.

5. Either use Koni Red shocks or the Rancho 9000 adjustables. I would like input on anyone who can tell me how the Konis and the Ranchos will compare. I like how easy the Ranchos can be adjusted. If Bob L. sees this which Rancho's would you use in this application or would you use the Konis?

Ranchos definitely have firmer damping. Depending on the final ride height the Koni reds may be too long and could bottom out. But they generally ride better than the Ranchos due to softer compression damping.

6. I will put heim joints on the tie rod ends and then drill the hubs. Then mount the joints on the other side to correct bump steer.

Make sure they're high quality chromoly, and you have a tapered bolt and tapered spacer to avoid binding....or they will break. If you need a picture I could take a few tomorrow to explain what I mean.

8. I will also put in probably soft poly bushings.

Believe it or not in some respects the hard poly rides better because it has less 'stiction' and tends to rotate on the metal sleeves better. I have always found that the hard Delrin AF material I use in racing Opels is more complinat that polyurethane in fact.

HTH, Bob

[Derek Greenwood]

Thanks Bob for your comments. I never thought about using heim joints for endlinks on the sway bars to free them up so to speak. I don't really know which bars to use. Has anyone measured them and calculated their stiffness. It would be good to know the difference between the OGTS and the Addco bars.

Yes I would like to see exactly what you mean on the tie rod ends.

I had setup my GT last time with your front fiberglass spring, OGTS swaybars and Rancho shocks. It was very stiff. It didn't bother me much but my wife wouldn't ride with me. She kept making comments about needing a sports bra. So this time I am trying to come with with a nice compromise. It's no good if she won't ride with me!

I am guessing the car will be around 2 inchs lower. Is this too low for the Konis? Which adjustable Rancho's would you recommend?

It makes perfect sense what you said about how the harder bushings won't "stick" and so therefor may ride better. I will change my plan to hard bushings.

[opelgt722002]

1. OGTS intermediate spring (the one that doesn't lower it very much) and then add lowering shackles to put the front end 2 inchs down.

The intermediate spring lowers it 1", the shackles usually lower it 1 1/2 to 1 7/8 so not sure how you will be able to keep it to just the 2" drop you want.

Make sure your wheels will clear the shackles. Some have had to use a wheel spacer .

You might want to buy the Lenk coil springs from OGTS instead of cutting yours for an improved ride.

[Derek Greenwood]

First if all I have heard that the intermediate spring doesn't lower it as much as an inch but never the less by narrowing the spring eye a bit I can move it up some and have shorter shackles. I believe I can get close to 2 - 2 1/4 inches with this combination. The key for me is I want to have shackles. If you drive your car without shackles and then add shackles you won't believe how much softer the front suspension is because of the lack of binding. I have had shackles on two different Gts and have never had a wheel clearance problem. My first car had 13 x 7 inch wheels and the second car had 15s.

It has to be a no sports bra zone. :o

[opelgt722002]

Originally Posted by Derek Greenwood First if all I have heard that the intermediate spring doesn't lower it as much as an inch but never the less by narrowing the spring eye a bit I can move it up some and have shorter shackles. I believe I can get close to 2 - 2 1/4 inches with this combination. The key for me is I want to have shackles. If you drive your car without shackles and then add shackles you won't believe how much softer the front suspension is because of the lack of binding. I have had shackles on two different Gts and have never had a wheel clearance problem. My first car had 13 x 7 inch wheels and the second car had 15s. It has to be a no sports bra zone. :o

Okay, OGTS catalog states an inch. I have shackles on one of my GTs . Thought you were ordering new wheels which as I recall the ROH did not clear when Russell Hegler tried the shackles on his GT.

[RallyBob]

A Manta setup is shown, but same general concept can be used for a GT. Spacer thickness can be altered to compensate for ride height changes.

In fact I built a set for Roger Wilson's GT which used a steel tube welded to the inner tie rod with a threaded insert at the outer end, which allowed a rod end to fit into it. Wish I had a digital photo of them, but alas I did not have a digital camera back then.

HTH,
Bob

[Paul]

Bob,

To make sure I/we understand the parts of the system... The spacer goes between the rod end and the steering arm, right? So what is between the lock nut and the steering arm? Also, what goes into the taper of the steering, if anything?

Thanks for the pictures!

Paul

[RallyBob]

To make sure I/we understand the parts of the system... The spacer goes between the rod end and the steering arm, right?

Maybe, maybe not. It depends on whether or not the bumpsteer needs correcting. So spacers (if used), will potentially vary in thickness. You would have to establish the bump steer curve from careful measurements and try various thickness' of spacers to reduce it to the minimum for your suspension travel. You'll never eliminate the bump steer entirely, just reduce it.

So what is between the lock nut and the steering arm?

Probably just a flat washer. I put a spacer there only to keep the assembly tight together since there's a locking nut on there and I couldn't thread that by hand all the way. I would not use the spacer under the lock nut in situ.

Also, what goes into the taper of the steering, if anything?

I drilled the steering arm straight through out to 5/8". The bolt is a 5/8" grade 8 hardened bolt which has had the underside of the head machined to allow for greater misalignment without binding.

Bob

[Derek Greenwood]

AWESOME! Thanks Bob. I will duplicate what you did as it looks great. I would like your opinion on the OGTS rear springs. I have never been a fan of spring rates as variable as these. I would think the handling would change too much as the spring compresses. It would always start out understeering. Also do you know how much stiffer the OGTS swaybars really are?

[RallyBob]

Originally Posted by Derek Greenwood I would like your opinion on the OGTS rear springs. I have never been a fan of spring rates as variable as these. I would think the handling would change too much as the spring compresses. It would always start out understeering. Also do you know how much stiffer the OGTS swaybars really are?

I don't care for the OGTS (Lenk) rear springs for handling purposes, as you've said they are too soft and promote understeer. However, they do in fact ride quite nicely (better than stock). Perfect for a cruiser IMO. Wayne Torman has a set of these in his GT with Koni's and it rides pretty damn well for a lowered car with heavy 15" wheels.

Somewhere I have the calculated stiffness rates for pretty much all the factory and aftermarket Opel swaybars. But I have no idea where that documention is....probably hiding out with the 3rd/4th gear detents I so badly need to rebuild that Quaife 4-speed gearbox in my barn. I know I have them, I just wouldn't know where to look.

Bob

[jordan]

Are there any other common options for lowering springs on a gt? I am not a fan of cutting springs, and it does seem that the lenk progressive springs would go from being very soft to very hard once the least resisted coils go into full spring bind (also ogts does not have any in stock as lenk has not made any in a while.) Has any one found a decent riding sporty rear spring set up to lower around 1.5"?

[jeff denton]

Yes! It's really simple, I just deepened the buckets. Same effect as putting a lowering block in a leaf-spring setup. The control rod angle remains the same, so rear steer isn't affected. I did have to modify the panhard brackets to compensate, but this was easy also.
I did two inches. So much the frame got in the way on the right side at full bump. So the frame had to go. Don't get quite this carried away, OK?
Yes, my car rides awful low... Passes inspection, though.

[opeldean]

Originally Posted by Derek Greenwood I want a suspension that is nice to ride in yet handles well. Derek Greenwood 72 GT

what really made the biggest difference in my car was replacing all 4 ball joints in the front A arms. You could be rusted a bit and they have slop in them that puts bind in other susspension parts. This will help level your car and make it feel like new. Adds compliance to the suspension. This was my experience.

[Viny Charb]

Ok Bob I know this is an old thread from four years ago but I was suprised to read that you mention to CUT the rear springs to match the front end hight. I was pritty sure I had read somewhere else (I wasn't able to find the exact thread where you say this) that cutting the rear springs to lower the car hurts the already bad geomatry of the opel rear susupension and can cause the rear end to react dangerously over bumps....If I'm wrong about this then I'm sorry for waisting your time...... Thank you for your patience..

[jeff denton]

Deepen the spring buckets! It works. It's easy. Geometry isn't altered.

[RallyBob]

Actually, whether you use shorter springs or deepen the spring buckets, the geometry changes.

Lowering any amount beyond minimal (say, past 3/4") means that the panhard bar geometry changes. By this I mean no only the length of the panhard bar, but also the angle. The roll center changes too. The angle of the lower trailing arms and the torque tube change as well, changing the anti-squat. If these things are attended to then it's not as big a deal as all that. The problem stems from the fact that most people just lower the car and change nothing else, so in fact they make the handling of the car worse.