icsamerica

Has anyone followed the instructions in this PDF to lighten the steering. I have a lathe and the skills to do it just wondering how it will be.
http://www.landsharkoz.com/forms/how...eering_928.pdf

On my last track day my arms started to go numb after about 5 laps. I kinda felt like I was fighting my arms not the car and couldn't place it where i wanted. After a few laps my arms were heavy and felt dull and imprecise from all the effort so I couldnt feel or get the feedback I wanted to drive confidently and push. Not something I experienced at that level when street driving my 928. I literally felt the burn and stiffness like I get after lifting weights. By contrast I have a Audi S8 which has extremely light but precise steering and I feel like I can put that car where ever I want. I do have sticky cup 2 tires on the 928 and the camber and castor are set at the high end of the range.

SwayBar

It would be helpful if you provided more details about your car.

For my 89 GT, the steering feels heavy on the street, but at the track at speed, it feels as perfect as can be.

dr bob

Unless you feel some other reason for maintaining high caster, that and wheel offset together do a lot to increase the steering effort.

Otherwise, reducing the diameter of the spring center in the spool valve is exactly what's needed to get more steering assist. You'll want to use the 100bar pump and may also want to replace the steering pressure hose with one that doesn't include the restriction in the middle.

My '89 S4 at speed has perfect (in my opinion) steering effort at speed. It gets better as the car goes faster, and is still dead calm at speeds well over 100 MPH.

If you have front wheel offsets less than 55mm, lighter steering gets a little exciting at speed, since every change in the road tries to pull the car one way or the other. The change in resistance to your steering inputs will give you a bigger response with the lightened torsion spring, maybe to the point where the car gets a little twitchy. You'll end up doing a lot of fighting, and that might be better solved with the correct wheel offsets (60-70mm) before you tear in to the spool valve.

icsamerica

I agree the 928 steering feels great at highway speeds, very stable, re-assuring and composed... that's how a GT should be, somewhat resistant to quick changes in direction unless pushed.... but that's not wanted when pushing a car around a road course for 20 min. I need it to change direction easier and quicker.

I already installed a Porsche 944 100 Bar pump. This was shockingly easy to do and made a slight difference in steering feel and response. It was clear that once the spool valve was open the steering was quicker but not by much. Kinds of a slight rising rate effect. I also have a custom pressure hose made with out the restrictor. I used 3000 PSI line that is quite rigid. This made for slightly more steering noise during parking lot maneuvers and also created a slight judder. I'm fairly certain the OE line is soft and acts as an accumulator. The restrictor also serves this accumulation and function and also reduces ballooning of the soft-ish pressure hose by creating 2 smaller sections. So upping the pressure and removing the restrictor made very little difference. The only thing left is the spool valve mod.

My 928 is an early 1986 with sport seats that I "halfed"
I have Panamera wheels with 8x19 ET59, that's about as close as I can get to the GT offset of 60.
I have full S4 suspension front and rear.
I have GTS front brakes with EBC yellow pads (disappointed, got squishy after 2 hot laps)

I was extremely pleased with how the car performed on the track. My performance as the driver was somewhat lacking.

FredR

The bit about the restrictor in the hose is something of a common false perception with due respect. I understand some earlier models had such but not the GT/S4 onwards. The 86 MY- thought they were same as S4/GT but...?

Individual preferences when it comes to driving are what they are. With your front wheels being the spec they are you can probably run with a 235 section up front but a 245 on 19 inch rims not so sure- either way you did not happen to mention such. Personally I love the way the 928 steering feels as one knows exactly what the front end is doing- so much so that in a 911 turbo that I once drove I felt clueless as to what it was doing.

In your case I would suggest that you try messing around with the toe-in. Take the car to the alignment shop you use and assuming you have a correct "stock" alignment to start with, ask them to set the alignment to minimum spec and then to zero toe and more importantly, ask them to record how many degrees of rotation they had to apply to each step. The toe-in takes little effort to adjust and with the wheels on full lock it can be done with the car on the deck as it were. Reducing toe lessens the steering effort noticeably. For track use you can even try zero toe to see how you like it but I would not recommend such for street use as the car gets very twitchy but it will turn in effortlessly. With 9.5 inch wheels up front and in earlier days with 265 rubber fitted I set the toe at the minimum end of the permissable spec range for general use.

Messing aorund with the rack and changing the effort ratio should not be needed but if all else fails, you have the ability to do so and you know what you are doing then go for it but only after you have tried the mods I am suggesting. Of course if you have tried such already that is another matter. Not related but I would never run 19 inch wheels on a 928 I am from the school of thought that says 18 inch wheels are perfect. As for offsets well they are a safety feature for street vehiucles and non negotiable as I am concerned, for sure not an isssue for track use but that is another matter altogether.

SwayBar

Yes, it is exhausting driving a 20-minute session at Road America, and I'm always happy to finally see the checked-flag at the end of the session despite the fact that I was having the most fun in my life while out on the track. Both my C5 Z06 - light steering, and 928 GT - heavy steering, were equally exhausting.

So the question is, how is your physical conditioning? Do you workout or do cardio work?

I can tell you from experience that If anyone is not in shape, a track-session will be taxing on the body and mind.

Sound like you have a good car to drive.

For brake-pads on the track, we use Pagid Orange, they never fade, and Road America has 3 sections of braking from 150 mph:

• Turn 1 - 150 to 75 mph
• Turn 5 - 150 to 55 mph
• Canada Corner - 150 to 55 mph

Again, Pagid Orange never fades under those circumstances.

Oh, and equally important, you NEED a high performance DOT 4 brake fluid such as ATE, or Motul etc. Stock fluid will not cut it on the track.

That's easily fixable since it sounds like you have the bug.

If you're not already, read-up on the principles of how to approach/attack a track, and then attempt to slowly apply those principles next time at the track - you will get it.

GUMBALL

May I make a few observations:
- how tightly are you gripping the steering wheel ? my perception is that you are applying too much "hand force" which will kill your hands and arms very quickly. Are you "hanging" your hands on the wheel ?

It is not necessary to SQUEEZE the wheel. Watch in-car videos from F1 or IndyCar drivers and see their hand placement, they look like they are sitting in a parking lot rather than doing 200 mph.

Your thumbs are the strongest part of your hands, use your thumbs on the spokes to turn the wheel, not the grip of your fingers.

- when I instructed at driving events, I found that I had to constantly remind my students to "RELAX YOUR HANDS"

Also, may I suggest "driving gloves" - I always used them when I did track events, gave me better grip with less stress. An (expensive) alternative would be a suede competition steering wheel.

- speaking of lifting weights, are you doing hand/wrist exercises ? are you doing enough ??

When I drove in endurance races, my co-drivers and I would do 2 hour shifts in the car, and never reached the point of exhaustion.

Just my opinions.

GregBBRD

Depending on which specification you are using, your caster "high end" is either 4.0 or 4.5.
There's only one function for caster and that is to allow the steering to return to center by itself.

Reduce your caster to the bottom of the specification, to start with. (You may be able to go lower than that.)

This reduced caster will also reduce the scrubbing on the inner edge of the tire and allow you to add negative camber.

UKKid35

Weird, they work brilliantly on track for me with standard S4 calipers, and EBC yellow all round

However I have fitted a 33 bar brake bias valve, and now the rear wheels get just as hot as the fronts

So hot that the dust caps almost start melting

UKKid35

Apologies for the slight digression from your issue, but one effect I have discovered is that you can 'run out of assistance'

It doesn't appear to be a rack specific issue, because it has happened with 2 difference cars (928 and Cerb) and 3 different steering racks

It also can happen with belt slip, but that is not what I'm referring to here

You can just hear me remarking on it in this video here at the 9:30 mark

icsamerica

Thanks for all the suggestions...

Yes, I need to work on my cardio. That's for sure... years of construction has conditioned me for more strength than fitness. That said... I also DE a Jaguar at the same track... The Jag has very light steering despite having a DB7 Sport rack and Steering wasn't even an after thought. Concentration on controlling the weight transfer was. Even so I was 4 seconds faster in the 928 despite it having 150 less HP on a much colder track, (30 degrees)

I also have have yellow stuff pads in the Jag, Not impressed there either, I thought red stuff was better for for the Jag.
I think the yellow stuff may not be getting hot enough, Limerock Park has 2 brake zones for the 928 and 1 is a tap. They just seem soft and kind of all or nothing, on-off.

The thoughts on alignment were interesting, I do my own with String at a higher level than most so I'm key'd in the the effects of alignment settings and usually dial in the feel I want. I think the delta I'm after is beyond what an alignment tweak can accomplish. Last track day I ran out of time and had it laser alighted by a quality shop to my specs, They sent me a screen shot of the machine, I will locate and post it up,

Regarding the issues with 19 wheels... I run an over sized aspect ratio on the tires which makes for a bigger sidewall and larger overall diameter. This lowers the effective CG and maintains as much ground clearance as possible and still provides me with ample side wall for compliance, ends up being the same as an 18. The 235 wide Michelin Cup2's are like rolling gummy bears and way beyond what the car was designed for. They are soft, quiet and very grippy when warm and I think the rack is just out matched. I may have the wheels widened a 1/2 inch so I can run a 255's up front which will just exaggerate the problem.

Not sure how the rack can run out of assistance, perhaps overheating the fluid? Didn't even think about a cooler but the 928 will have one for the next track day for sure.

Probably a good idea for me to remove the pressure limiting valve on the rear circuit since I have only GTS brakes up front and am more forward bias'd as a result. Thanks for the idea. I will see how much dive I have and consider it. That said for Limerock I dont need more brakes I need precise brakes.

I have a spare rack and I think I will give it a go. Porsche did it to the 928 in the later years and I can't find a later rack so my options are limited to DIY. I'm also eager to get inside the rack to machine up a pair of delrin insert bushings to limit the rack's non lateral movements inside the tube for more precision. I already have solid mounts.

dr bob

Do the group here a favor and document the process if you can spare the picture-taking time. I've done the mod to other cars, but it usually involved swapping the whole pinion assembly from another car in the subject's family. I usually moved towards more feel/less assist though. No hands-on with the 928 racks yet. Any help is appreciated.

GregBBRD

Do not remove the rear pressure valve, unless you are switching to a more modern ABS system
Change it for a more aggressive valve to get the rear brakes more involved

Different people drive....differently. What works for one (yellow pads) may not work, for you. Find what works and do that.

FredR

The 928 seems to like the 33 bar rear bias valve that I use the idea being to augment the trail braking capability that the 928 is so good at [and the 911 isn't]. Never read of anyone trying that and not liking it.

There is a reason why F1 drivers train hard and are supremely fit!

UKKid35

The S4 does have a cooling loop, earlier cars didn't, not sure when they were introduced