raising spindle height on struts

[dbanazek]

I was just searching for our name through some of the old posts making sure we were keeping our customers happy when I came upon this thread. Alot of people seem to be interested in this sort of thing so I thought I would add my 2 cents.

There is a program out there called susprogdesigner. I think it was about $150. You have to put all of the chassis measurements in to get any results out but it is pretty cool once you have it setup. It gives you numerical and graphic output.

If you lower a 911 too far the roll center does go below ground and it also starts moving from side to side a lot. I am not sure what this side to side movement does for handing but it can't be good. With the chassis setup at stock ride height the roll centers do not move side to side much and the bump steer looks good.

I used this program to design our new bump steer kit. As you lower the car to about 1.5" below euro where the arms become horizontal you need about 3/4" of correction in your bump steer kit. Actually bump steer is pretty good at just below euro height to horizontal with about a 3/4" bump steer correction. Things get really nasty when you lower the car and raise your spindles without a bump steer correction. You need to start out by adding a bump steer spacer to get the steering arm back where it was (ie 3/4" for an RSR strut) and then add more spacer for lowering the car.

These are all rough numbers. Once I get the parts back from the anodizer I will post some info showing the various toe changes as the suspension moves through droop and bump at various ride heights with and without a proper bump correction. I will probably offer a custom designed bump kit with accompanying computer printout in case you raised your spindles 1 3/4" and put in a 935 front suspension with raised inner pickup points or something like. (oddly I already have this one worked out because thats what I did on my racecar) You need a big super duty bump steer kit.

Raising spindles is not that hard. You somehow remove the 3/4" round weld mark on the back of the spindle (I use a mill because its faster and neater). In my experience though you also need to chuck the whole thing up in a lathe and take down the diameter a touch just above the spindle. It is slightly tapered there which prevents you from pushing the spindle up. I like to fill in the factory weld spot and then run a bead all along the top spindle to strut joint. I have done this on a few factory units that just came loose as well. You can go about 1 1/8" on a 16" wheel with a stock A-Arm. You may need to remove a little material from the bottom of the arms depending on your wheels at this height. Believe it or not you only need about 1/8" clearance from A-arm to wheel. I thought you might need more with wheel flex and all but 1/8" seems to work just fine.

After you move your spindle you will need to do a bump steer kit and or bend the tie rod arms on your spindles. You heat them up to dull red and bend them into an S shape to get the ends back to where they were before you raised the spindle. This eliminates the need for huge bump steer spacers. This is especially useful if you have gone more than the 3/4" RSR height.

I like the LEDA struts because you can get an adjustable remote reservoir strut and LEDA will put the spindle height werever you want it. They are a little less than the JRZs too. That's how I got 1 3/4" raised spindles on my race car. The trick was getting them to fit inside my SCCA mandated 10x16" front wheel. Thats were a pair of modified 935 front control arms came in. Now I am sitting at about 3" below stock ride height with nice upwardly sloping A-Arms.

So you can get the front of the car really low without altering the suspension travel, bump steer and camber change characteristics that Porsche designed into this car by raisng the spindles and using a bump steer kit but then you run into trouble at the rear.

You can lower the rear of the car more than the front without without screwing up the toe and camber curve too bad, and the roll center is already pretty height in the back so lowering it is good. Where you will run into trouble is with shock travel. I bet there are a lot of 911s running around out there on the bump stops. I haven't really looked into this, but if you wanted to lower your car 2-3" and still have everything work right and you already raised the spindles on the front you would have to find a shorter shock for the back. I imagine Bilstein could shorten a Porsche shock or modify a shock that was shorter already to get this to work. Of course when you are building a GT class race car you can put in a coilover shock of the length you choose at a chassis pickup point you choose.

So the bottom line. Don't lower your car more than 1-1.5" without raing the spindles. If you raise the spindles you can lower the car the extra amount you raised the spindles. somehow correct your bump steer. Make sure you have enough travel in the rear shocks. If you have less than 2" you will be rideing the bump stops from time to time.

[84toy]

I'm right in the middle of a suspension overhaul with polybronze bushings etc, and to me raising the spindles on the struts seems to be the proper way to lower a car. Since I have a lathe and a mill with welders to boot, I may raise my spindles because it would be pretty easy to do and a great time to do it. Here is the problem....When I bought the car it was already lowered so I have nor reference. Can someone tell me how high to raise the spindle on the strut to get back the original angles if I set the ride height to 25" in the front??

[ChrisBennet]

I don't think you need to raise the spindles to run 25" in the front. I run less than that without even using rack spacers.
-Chris

[84toy]

I had a lot of bump steer at 25.5 but no spacers. The front bushings were junk and probably were the main culprit though. The tie rods were not even close to being level at that setting, again maybe the bushings. Moving the spindles couldn't be more than a couple hours of work with the tools I have and I don't mind doing it if I know how much to move them. It's bound to be better than not doing them and if I want to go a little lower, I am closer to having a livable setup. Great topic by the way....

[84toy]

Sitting here thinking about it.....Wouldn't raising the spindles give you a little more tire to fender clearance?

[dbanazek]

I am not sure where 25" fender height comes out to but I would start at the stock euro height of having the wheel center 4.25" above the torsion bar rear center. That is ideal. You can go an inch below that and be OK but if you are moving the spindle I would raise it the same amount you want to lower the car below euro height.

[84toy]

Thanks Dave, can someone post the actual fender lip measurements for USA and Euro and the USA wheel center to torsion bar center for USA? This would give me enough info to check this out. Thanks

[Wil Ferch]

Paul S:
I've been challanged on this point...but by 84, the USA ride heights were pretty much identical ( if not actually identical) to Euro. Dave at Dart Auto gave the proper wheel centerline-to-torsion bar centerline of 4.25" for the "proper" Euro setting...which is the same as the metric 108 mm in the factory manual. Although a cruder method of measuring... most people take this 108 mm value and equate that to *approximately* 25.5" front fender lip height to ground...using a standard Porsche wheel rolling diameter of just short of 25"....which is a fairly consistent diameter since the 356 days ( example: 205/55-16 and 225/50-16 are about 24.88" diameter).
I hope these numbers help...
---Wil Ferch

[84toy]

Thanks Wil, These dimensions bring more head scratching for me because my front fender lip was about 25.5 and my tie rods were not close to being level before I took it apart and it had annoying bump steer. I would guess that it would have taken at least a 5/8 washer under the rack to make them level. As I stated before, the bushings might have acounted for 1/4 " of that since they were pretty sad looking. I have stock wheels and tires on the car. (for now) My goal is to have the tie rods level and a fender height of about 25" and I doubt if it will make it without rewelding the spindles. I wouldn't mind the car a little lower than 25" since it is not a daily vehicle.

[Tspringer]

For what its worth as a followup to this.... I had the spindle on my new bilsteins raised by Smart Racing Products when I purchased the struts. My car is a '69 911S and I run 15" wheels. They raised the spindle too much. The lower a-arm binds against the wheel. Now the struts will have to come off, be shipped back to CA, re-modified and shipped back.....

Make sure whomever does it knows what they are doing.


Terry

[Chuck Moreland]

Terry, how much did they raise it?

Mine are raised 19mm. Straight away, I had rubbing in the wheel.

I added wheel spacers to the front and gained some clearance. I also got busy with a grinder on the edges of the A arm and the ball joint retaining ring.

I've now got plenty of clearance with my 15s.

[Wil Ferch]

Chuck:
Factory RSR raising for 15" wheel applications didn't go beyond 18mm ( usu 15-18 mm)....implying ball joint interference otherwise. 19mm should have been OK if you were using 16".
---Wil

[Tspringer]

I honestly dont know exactly how much they raised it. However, it was binding BAD. We discussed going the spacer route and grinding but I would have had to remove 1/8 inch or more of material and even then it may have rubbed. So, the only viable solution was fixing the core problem. Struts are on their way to SRP now.


Terry

[doozer]

Has anyone come to a consesnus on a sugested hight to raise spindles.

[randywebb]

Depends on how low the car is.

[ted]

Originally posted by doozer
Has anyone come to a consesnus on a sugested hight to raise spindles.

How low you want the car and what diameter rim. Raising the strut can cause interferance with the lower ball joint, the larger diameter rim the more you can raise the spindal.
Some add 1.5 degree negative camber to the spindal at this time so in race applications you can get closer to -3 degrees camber with the regular adjustments.

All I could add is for the super low cars the adjustable rear control arm boxes will allow you to (bump) adjust and control the toe through the rear suspension travel.

Long thread and lots of good stuff.

[Zeke]

Originally posted by randywebb
Depends on how low the car is.

Depends more on what the wheel diameter is. Recently, I looked into raised spindles. I want to keep my 15 x 7 fuchs, so, in SAE terms, about 3/4 of an inch is the max. To me, that wasn't worth the trouble. If I would go to 16's, there's another 1/2" for a total of 1 1/4. At that point, it begins to make some sense to me. For guys that will use 17's, well, I think wou can bring the tub as close to the ground as you would ever want to, given the other considerations discussed in this thread many months back like roll center.

Maybe next go-round. I'll take the 3/4", but I have other priorities, like getting the car back on the road. BTW, I talked to Chris at Tangerine Racing just 2 weeks ago and he still does the struts for less than $300. He is good, let me tell you. But, if you can get the spindles loose yourself, any good certified welder can reweld them.

[doozer]

The reason I am asking is I am in the process of adapting an air ride " rolling bag over shock " type strut to the 911 lower strut body with spindle. - Yes, too much free time...

I will be able to run the car quite low and I have very open forged 18" x 11" wheels on the front.

I have bump-steer spacers installed already and I was concerned about the geometry running much lower than spec. Freeing the spindle ring and re-welding it is not a problem, I was just wondering if there was a maximum to stay away from.



Thankss Todd