Technical Articles

Lowering the suspension

The ride height on 912E and US spec. 911s of this era was higher than their European counterparts to satisfy the US Federal requirements for bumper height.

Many owners like to lower their cars to the European specs. Doing so can make a big difference in cornering and overall feel of the suspension. Visually these cars tend to look better sitting a little lower (you just have to be more careful over speed bumps, or when turning into driveways). The procedure for lowering the suspension is pretty straightforward.

Lowering the front of your car is a piece of cake. Just back out the jack screws for the front torsion bars.

The rear, however, is a different story. The rear torsion system works on the same principle as the VW bug. Read the procedure in that book, and you will see that it is a process of relocating the splines on the inner and outer ends of the torsion bars to get the desired result. Remove the spring plates, pull the torsion bars, relocate the splines, put everything back together, and see how the car sits. If you need to adjust the height you do the procedure over with different spline locations. You can't just relocate the spring plate on the outer spline by one tooth because the car will sit too low.

Another option is to buy a set of aftermarket adjustable rear spring plates. Once you install them you can move the rear of the car up or down by turning a set screw without effecting your camber and toe settings. This is not the case with the later factory adjustable plates. The plates cost about $325.00 but they make the job easier and after their installed corner balancing is a snap.

A side-effect of lowering is bump-steer. What you'll feel is the steering wheel kicking back in turns. In normal highway driving it's hardly noticeable and only slightly annoying. In any kind of aggressive driving with lots of corners, banks and elevation changes in turns it's downright unnerving. It takes a lot more work to keep the car on track and it slows you down.

To solve this you may need to install a bump-steer kit. The kit consists of thick steel spacers that are used to lower the steering rack. This keeps the tie rods in proper alignment and reduces the bump-steer caused by lowering the car.

I would strongly suggest a corner balance and alignment, as they are critical if you are going to lower.

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I would purchase or get a hold of the book "101 Projects for Your Porsche 911".  It contains procedures (Project 55) for lowering both front and rear ends to the European specs, which was much lower than the US requirements.  The 912E has the same suspension as the 911 so the procedures are the same.  In my opinion, a lowered 912E/911 is much better looking than the look of the US models.  You just have to be a little more careful when turning into driveways.

Your money is well spent on this book as it has many articles that apply to the 912Es as well.

I had mine lowered to 1/2 " under Euro specs.  It makes a big difference in cornering and overall feel of the suspension.  I have had no difficulty with steep slopes or driveways, but I am pretty careful with speed bumps, as I have an air dam on the front.  I use 16's all the way around, with no rubbing.

I would strongly suggest a corner balance and alignment, as they are critical if you are going to lower.

Lowering the front of your car is a piece of cake. Just back out the jack screws for the front torsion bars. The procedure is in your book "101 projects for your Porsche 911". The rear, however, is a different story. Read the procedure in that book, and you will see that it is a process of relocating the splines on the inner and outer ends of the torsion bars to get the desired result. So you remove the spring plates, pull the torsion bars, relocate the splines, put everything back together, and see how the car sets. If you need to adjust the height you do the procedure over with different spline locations. You can't just relocate the spring plate on the outer spline by one tooth because the car will sit too low.

When I did this project to my (now Steve Patrick's) E I bought a set of aftermarket adjustable rear spring plates. Once you install them you can move the rear of the car up or down by turning a set screw without effecting your camber and toe settings. This is not the case with the later factory adjustable plates. The plates cost about $325.00 but they make the job easier and after their installed corner balancing is a snap.

When I lowered my E bump-steer became immediately evident. What you'll feel is the steering wheel kicking back in turns. In normal highway driving it's hardly noticeable and only slightly annoying. In any kind of aggressive driving with lots of corners, banks and elevation changes in turns it's downright unnerving. It takes a lot more work to keep the car on track and it slows you down.

Adding the spacers on the steering rack smoothed it out perfectly.

Unless I am way off base, lowering the 912E to Euro specs will NOT cause any bottoming out or tire rub. That is unless the tires/wheels have been changed to other than stock and/or the suspension needs new parts, e.g. shocks, etc.  If that was the case, every 911 sold in Europe would have had this problem from day one.  The only reason that the 912E and 911s were adjusted higher was to satisfy the US Federal requirements for bumper height.

Thanks, everyone for the benefit of your experience.  Turns out the rear torsion system works on the same principle as VW bug.

 

I plan to lower it about 1 inch and see how I like it.  With 16X6 Fuchs (205/55 R-16 Dunlop Direzza tires) on the front and 16X7's (225/50 R-16 Dunlop Direzza) on the back, I need to be sure there will be reasonable wheel well clearance.  I will plan to put the spacer in to keep the tie rods level.