Lowering for handling

[coglin]

I am thinking about lowering my '79 sc. Currently it is at Euro spec (25.5,25), I am thinking of going about an inch lower. The car has 22/28 torsion bars and stiffer shocks. The car does see track days, and I am in California (so hitting potholes is not a big concern). I would like to know whether or not the car's handling will improve, stay the same, or deteriorate from going lower.

Thank you

[stlrj]

Do a search. So much written on this subject you won't know where to begin.

[Bill Verburg]

Originally posted by coglin
I am thinking about lowering my '79 sc. Currently it is at Euro spec (25.5,25), I am thinking of going about an inch lower. The car has 22/28 torsion bars and stiffer shocks. The car does see track days, and I am in California (so hitting potholes is not a big concern). I would like to know whether or not the car's handling will improve, stay the same, or deteriorate from going lower.

Thank you

As the car is lowered the issue that becomes increasingly hard to deal w/ is bump steer. If you go lower than you are now be sure to install a good bump steer kit.

A secondary issue is street transitions, if you have an effective front spoiler it will drag.

pot holes are usually more related to low aspect ratio tires

[Tyson Schmidt]

Not to mention hitting the bump-stops.

You'll run out of travel in the front for sure without raising the spindles AND cutting down the bump-rubber.

In the rear you'll need to trim down the solid portion of the bump-rubber the same amount that you lower it below Euro height. I wouldn't trim more than 25mm, or you'll risk tire rubbing issues.

[Paulporsche]

What is the diameter of your tires?

[TRE Cup]

And the tire rubbing issues Tyson is referring to is for inside as well as outside shoulders of the tires.
The shock cup flange and the front tub where it curves downward are typical interference areas on the inside when running large wheels/tires , lots of negative, and a really low set up

[Tyson Schmidt]

Originally posted by TRE Cup
And the tire rubbing issues Tyson is referring to is for inside as well as outside shoulders of the tires.
The shock cup flange and the front tub where it curves downward are typical interference areas on the inside when running large wheels/tires , lots of negative, and a really low set up

Yes, in the front you shouldn't cut more than about 10-12mm from the bump rubber.

If you run larger diameter wheels, it's best to raise the spindles 28-30mm for 16", and add 12.5mm to that for each 1" increase in wheel diameter you plan to run. That'll allow full length bump rubber to stay in place which will help with the rubbing issues in front.

In back, you just have to cut the bump rubbers downso that you have adequate room between the rubbers and the shock at ride height. I recommend doing a check with the shock protectors removed and the car on the ground and settled. you can reach your arm up in the shock cavity and feel the free room. I'd want around 1.5".

[coglin]

I have 7/9 x 16 Fuchs wheels on the car. Front tires are 225/50, rear is 245/45. No rubbing issues so far. (any comments on going this wide in the front are welcome, I just changed from 205's).

I should also mention that this is a high mileage car with cosmetic body damage which pretty much makes it worthless - thus, I am not excessively concerned with spoiler rubbing (it does have the rubber spoiler), or having to roll the fenders - or to start chopping anything else on the car for that matter. Since I hit it, the car has just become a toy that I play with, quite liberating and fun, in fact.

So, is there a concensus that:
1. A bump steer kit (beyond the usual spacers) is necessary?
2. Spindles have to be raised?

Also, I have camber plates on the front of the car, do these not raise the shock mounts to help with bottoming out issues?

Lastly, no one responded on whether or not you would expect a gain in handling from this change, anyone with that experience here?

Many thanks

[911pcars]

Heed all the advice offered by these knowledgeable persons, but yes, it will improve handling over the factory ride height settings. Don't go too low is the common advice along with the issues created by less tire and road clearance.

Sherwood

[Tyson Schmidt]

Well, just lowering the car without taking the proper steps as mentioned earlier can actually make the car handle worse.

Done right, it will improve grip, but it's in the details of the set-up as to whether or not the car "feels" right.

[Superman]

I am planning to take my car to the alignment place soon. I have lowered it myself. It is pretty low. The front tires (stock 205 x 55/16) rub against the inner portion of the wheel well, but I don't care about that.....I'll just avoid lock turns.

When I put new shocks on the car, I remember cutting off one of the rubber bump stop thingies. I think there were two or three, and I cut one off. I think that was in the rear.

I am unfamiliar with the bump stop modifications mentioned for the front. How do I do this?

[Tyson Schmidt]

Originally posted by Superman
I am planning to take my car to the alignment place soon. I have lowered it myself. It is pretty low. The front tires (stock 205 x 55/16) rub against the inner portion of the wheel well, but I don't care about that.....I'll just avoid lock turns.

When I put new shocks on the car, I remember cutting off one of the rubber bump stop thingies. I think there were two or three, and I cut one off. I think that was in the rear.

I am unfamiliar with the bump stop modifications mentioned for the front. How do I do this?

Jim, I think you have Bilstein front strut housings, no?

If so, you remove the top nut in the upper strut mount, and drop it out. Then drive out the roll pin at the bottom that anchors the insert into the housing. Now you can remove the insert. The bump rubber has 3 identical segments.

In the rear, you really should cut away the top solid portion, not the bottom segmented portion. This retains the progressive nature of the bump stop.

[Superman]

Thanks, Tyson. Pardon my confusion. I remember a three-sectioned bit of black rubber. I remember cutting one of those sections off. I thought it was in the back, and now I'm hoping it was in the front. I don't want to mess with that front again. If I do, I assume I will need a new roll pin?

The rear would be easier, but I don't remember two kinds of bump stops.

[Tyson Schmidt]

Originally posted by Superman
Thanks, Tyson. Pardon my confusion. I remember a three-sectioned bit of black rubber. I remember cutting one of those sections off. I thought it was in the back, and now I'm hoping it was in the front. I don't want to mess with that front again. If I do, I assume I will need a new roll pin?

The rear would be easier, but I don't remember two kinds of bump stops.

The rear is all one piece, but it's solid at the top, and the lower section is accordian-like. Just cut off the needed amount from the solid portion. A lubricated hacksaw works best.

[Superman]

Whew (maybe)! It looks like the three-sectioned thingie is on the front Bilstein insert. If the rears don't have this, then I'm in good shape. It means I have already trimmed the fronts.

But if the rear shocks also have the three-sectioned thingie, then I probably trimmed the rears but not the fronts.

And I still don't know what is meant by the top, solid portion. Perhaps I'll remove a rear shock and have a look.

[Tyson Schmidt]

Jim, it's definitely the front that is in 3 even sections. They are about 3/4" long each, and about 1.25" diameter, IIRC.

The rear is quite large by comparison, and the bottom half is in 3 even sections about 10mm thick each, and the top half is one big solid section about 1.75" long. I have one in my hand right now, and it's just over 2" in diameter.

[Superman]

Thanks, Tyson. This helps a lot. We'll see. If I have to deal with the front again, so be it.

Two things, in case you check back in:

1) I think I'd find and use new roll pins.
2) I'm not doing anything special about the bump steer thing except I did install the rack spacers. If this means my handling will be crappy, warn me please. I frankly don't care that much about steering wheel movement. I'm more concerned about the impact on "caster."

[Tyson Schmidt]

Rack spacers are fine.

It's when you raise the spindles that the tie-rods and the lower control arms really get out of parallel.

Yes, new roll pins are wise. Be careful to get the notch in the insert lined up perfectly with the roll pin hole before driving it in. I've seen people really botch this, and it really messes things up.

[Superman]

We miss you Tyson, and we trust you're designing some truly EVIL go-fast parts. Thank you for the ongoing wisdom.

[Tyson Schmidt]

thanks Jim. I'l have to get up there for a visit soon.