Ride, Brakes & Suspension Upgrades

Disclaimer: The content of this document relates to the Porsche 993 (911 1995 to1998) I am not a professional automotive technician and some of the opinions expressed in this document are just that, opinions, therefore, please feel free to use this document at your own risk. Many times a lot can be learned by simply watching qualified professionals work on your 993                          

Replace Strut cartridges and or springs - IF your car bounces on the rebound while driving, the suspension sits low or seems harsh on brick or cobblestone roads. Most of our cars have replacement (upgraded) aftermarket struts already that are good-to-go as-is. 

If the aftermarket struts the previous owner put on your car are H&R or Bilstein (most common brands) and sometime in the future need replacement, they can be rebuilt at substantial savings over buying new – saving potentially $1500 or more over a new set. Come to think of it this is a very good reason to replace the original struts with one of these two brands in the first place. Many US cars have had their springs swapped out with aftermarket springs early in their life to lower the suspension to a more sporting height. Over time these aftermarket springs can sag. Replacing struts, springs, or both as a complete coil-over kit is a surprisingly easy job done with jack stands and one of these: “MacPherson Strut Spring Compressor Set” transforming the ride of the car.  Also, see Appendix “L” concerning safely lifting your car:.  

An inexpensive height-adjustable coil-over option I have had great daily driver results with for the last several years is the H&R Street Performance Coil-Over kit 29954-1 on hrsprings.com, both springs and matched struts for all four wheel ends, cost a little less than $2000 if you shop around, I got mine on e-Bay. This kit allows for setting the ride height from the USA specification down through the ROW range, -30mm on to a greatly lowered height where other suspension component geometry limits come into play.  Be aware that some struts and damper sets have limitations in how far they can lower the suspension so if this is your goal get some advice before making your purchase.

Lots of aspiring track guys buy strut kits with adjustable valving for example Bilstein PSS-10  series struts for a considerable premium over the above kit or Bilstein's other B6 or B8 Product offerings, to each his own I say. If you do replace your struts as a complete coil-over kit keep your original springs for when you sell your car.

Here is a spring height chart useful in understanding the range of heights to use and how to measure a 993 suspension height.

Here is a page with suspension spring rates and other specifications.

Here is a page with information on suspension springs & ride height, M030 suspension part numbers, and 964 ride height information.

If you wish to avoid having to bleed the brake system when replacing 

the struts many folks cut a

slot in the hose mounting flange welded to the old and replacement struts so they can simply transfer the hose fitting to the new strut without the need to open it and subsequently bleed the system.

I did this and it worked well.

You can reuse the existing rear anti-sway bar down-links with the H&R kit or really any kit if the ride height is set somewhere between USA standard and ROW lowered height (-30mm). The only additional parts you will need for the job are 16 replacement M8 all-steel lock nuts (900.380.005.09) for where the strut mounts  (hats) attach to the body at the top. Porsche specifies not reusing these prevailing torque nuts.

Getting an Alignement:

Once the new coil-overs are installed the car will need an alignment. A 993 needs to be aligned by a shop that knows how to do it and has the special rear kinematic toe adjustment tool. This special tool is not needed for the 964 or the 996 and later vehicles. Because a proper alignment can't be done without this tool and someone who knows how to use it, I let the dealer do the job. My experience has been that even with the correct tool sometimes I need to bring the car back in to have the alignment adjusted a 2nd time to get it right and resolve incidental handling issues unique to aligning a 993. One of the indications your rear Tow/Kinematic Tow is off is the car's steering seems to wander at higher speeds, this can be very disconcerting and may be erroneously attributed to worn bushings or bad struts. For this reason, don't be shy about having an alignment redone. In fact, I would recommend that an alignment always be done first to resolve handling issues before moving on to the expense of replacing components.

Replace suspension bushings - IF your 993 does not feel tight after a known good alignment the suspension bushings should be evaluated for play. Many folks have replaced the lower control arm bushings in a quest to tighten up the steering feel on their 993/964. Here is a method I came across that pictures removing the control arms with a puller. Seems easier than other methods.

Replace tie-rod ends if play is present - IF only the end boots are cracked just replace the boots.  See: "Energy Suspension Tie Rod End Dust Boots " on summitracing.com.

A simple tool to do this at home; See “Tie Rod and Pitman Arm Puller” on Harborfreight.com. Similarly, the boots can be replaced on the stabilizer bar downlinks if they are dried out and cracked.

JP Classic Parts Group is a manufacturer of exact replacement suspension parts such as suspension arms and bushings for the 993. They even offer rubber strut hats as the ones on our cars are now 25 or more years old and if original should be examined as part of a strut replacement.

Their products can be purchased at many import automotive distributors and offer significant savings over sourcing the same parts through the Porsche dealer network.

Upgrading the brake hoses - One of the easiest and most rewarding upgrades is to replace the now 26+-year-old original rubber flex brake hoses to the wheel ends with braided hoses. It profoundly improved the feel of the brakes on my car. 

Get brake hoses that comply with the technical aspects of the Department of Transportation  FMVSS106 standard. These hoses typically, among other features, have crimped-on end fittings. Here is a comprehensive discussion of  Stainless Steel Braided Brake lines. 

This is not to say replacing your 26+-year-old brake hoses with fresh standard DOT rubber ones will not result in a similarly improved brake feel. It's just I have not personally done this.

If you decide to replace your brake hoses some folks like the idea of adding a stainless steel guard spring sheath to the brake hoses. I have not had the need for this and have never experienced debris impact or suspension component scuffing damage to a brake hose.

However, some may desire this possibly for greatly lowered suspension applications where the potential for hose damage may be increased. The sheathing can be purchased at Walmart or any online or retail store that offers automotive supplies.

The secret to making hose replacement easy is to buy 18mm, 17mm, 14mm, and 11mm hydraulic fitting flare nut wrenches needed in a premium brand such as Snap-On. It is interesting but in the Craftsman brand, it seems there are two lines of wrenches. The bright smooth chrome ones seem to be of very high quality and the matt-finished ones are problematic. Inexpensive wrenches have heads that flex and distort the fittings when one tries to remove them turning a simple job into a nightmare of damaged fittings to complete. Also having a power bleeder on hand makes bleeding the new lines a very easy one-person job.

Rear Kinematic Tow Adjustment - There is lots of talk about the need for a rear kinematic adjustment unique to the 993 during an alignment.

It turns out that one of the reasons that this and the other settings need to be looked at during a routine alignment has to do with the adjustments slipping out of position primarily if you track your vehicle. With this in mind, I would take a cell phone picture up-close of the rear suspension setting positions at the time of a known good alignment and periodically check the settings through visual inspection. The settings for the rear suspension are labeled A, B & C in the above illustration from the shop manual. It may also be a good idea to take a Sharpie pen and mark a vertical line down each of the coilovers on your car. In this way, if a spring purchase or a sway bar mount slips you can see it.

The Porsche factory tool
supplied to dealers

I read all sorts of discussions of the need for the factory tool for setting the rear kinematic toe control on the 993 during an alignment. The Dealer factory tool is a very neat piece of unobtainium.

There is a simpler aftermarket tool made by Autometrics that is similar to Porsche Motorsports tool for setting the Kinematic Toe that unlike the Dealer factory tool requires replacing the four caliper mounting hex head cap screws with:
M12 x 1.5 x 40 (#900.067.170.02) socket head cap screws to use it. It then simply slips over the heads of the fasteners to use. 

FD Motorsports makes a similar tool that they show in their instructions fits over the hex head capscrews' original to our cars, not requiring swapping out the caliper mounting screws. There seems to be an application conflict as recently a purchaser of the tool could not get it to fit over the head of the fasteners on their car. 

In reality, the factory & aftermarket tools are nothing more than proprietary tilt gauges similar to the gauge you see on a sailboat that lets you know how much the boat is heeling over while underway.  For this reason, I see no reason why a generic precision digital tilt gauge, purchased on eBay for $25, could not be used for the same purpose. One would simply need to calibrate the gauge to the factory gauge by placing it against the appropriate rear arms that influence the kinematic toe after a known good setting with the factory tool and then record the values. I am sure there is a little more complexity and subtlety to developing this idea into a working how-to. At this point, I’ll leave it to others' volition to sort this out.

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