Correction for Bump/Roll Steer, Lowered Manta by Two Inches

[Paul]

Bob or anyone else...

I bought springs that gave a 2" drop in the front of a Manta, now the tie rod angles upward from the rack to the wheel. Is there any way to get the tie rod level after the car has been lowered? Or is there any need?

Thanks

[16Vmanta]

There's a similar discussion going on at the Opeltuners forum, www.opeltuners.com.

[Sparky73]

What kind of tires are those and how much? I really like them! How do they ride?

[soybean]

A little off topic and will probally get moved to tire seection Jon, but check out tirerack.com. I have Sumitomo HTR 205s on mine. Great price, and man do they hold the road. Jarrell

[jeff denton]

Paul, I think you have discovered how messing with ride height affects the geometry of the front end. I know the lowering spring is the quick easy cheap way to lower your car, but now you've got to make it handle again.
I have books, and there are fancy computer programs that show you how to "map out" your entire suspension geometry so that you can take it through its movements and see what the effects are and how to adjust it.
In most forms of racing this is absolutely critically crucial, on a street car it is not, but of course you need it to be safe!
Have you ever noticed how more common vehicles are lowered? They use a spindle that has the axle stub located higher between the ball joints. See how that method did not affect the geometry of the upper and lower A-arms and tie rods?
There probably are no such spindles for Opels so it has to be done differently...
On race cars we use little spacers between the tie rod end and the steering arm, but they won't take up two inches.... And they don't address the fact that the control arms are now two inches off.
Another way to properly lower a car is by channelling the front suspension system (crossmember and all) higher up in the frame. I did one inch of this when building Speedway GT, is it possible in a Manta?
Sorry I haven't really helped you, hopefully someone here can.

[Paul]

Jon,
The tires are Bridgestone RE 950s. They are an EXCELLENT tire, for the money or not. Sorry They are 14's and don't come in 13 inch sizes. I'm running BMW/BBS alloy 6-1/2 x 14 wheels from a mid 80's 325.

Jeff,
Yea, I knew going in that the geometry would change. That's also why I decided to limit the reduction of hide height to just two inches. For the GT, RallyBob had described a couple of very doable ways to correct bump steer. I was hoping that a simlarly doable solution was available for the Manta.
But, it appears the solutions are a bit more complicated.

Also, I must add, the handling did not deteriorate from stock, in fact, I've seen a significant improvement. On smooth roads there's no adverse affects at all. But on poor 2 lane back roads, the asymetric undulations, camber pitch, etc (left side vs right, etc) causes a bit of wander from the increased bump steer. Nothing very drastic or dangerious, though.

FWIW, I'm running custom valved Bilstein shocks, poly bushings... Alignment settings -1.8* camber, 5.25* Caster, and 1/32" toe in. The car turns in nicely, has a great deal of grip w/ an expanded limit, but still understeers a bit more than I prefer. I'm used to a maxxed out Stock class Neon R/T with the addition of a 22mm rear bar vs the 16 mm rear bar from an ACR. With just a twist of the rebound adjustment knob, you can make it corner with the tail out on a dry road! And remember its a FWD!

Thanks

[hardtime72]

If you want to see whether the effects of your change are within toleances then you can check out the downloadable program in my thread yesterday in suspensions. If this isn't what you need then I can only suggest a custom designed extention for the pinion for the cars new height and geometry. well if it's possible. the thing I noticed on your car different than most is that the tie-rod end goes in from the bottom placing the center of rotation lower than the centerline of the spindle so if this is possible then the extention should be possible as well.
This could be dangerous work if you don't check the proper strength and dimentions required. I used to work for DANA Corp. making tie rods and draglinks. There shouldn't be to much pressure placed on the pinion. the critical point is the taper hole in the pinion itself.
On second thought you may want to raise the rack end or position the rack itself higher if room makes it possible.

[kwilford]

Moderators Note: Moved to the "Performance Suspension and Braking Upgrades" Forum where it seems to fit better

[jeff denton]

We could break new ground here by putting our heads together and coming up with something just about everybody in the custom Opel department will want. How about this:
What readily available junkyard "spindle/balljoints/steering arm/disc brake/hub assembly" would go into Opel A arms and provide a lowered effect as well as improved braking, parts availability, maybe even five lugs (to match an improvement in the rear with five lugs/same pattern wheels)?
Anybody got their thinking caps handy? Could this work?
Just a thought.