TRZ06

While fixing the toe in the rear can help, the main issue is just an underdamped rebound stroke. There is a fine line between too little or too much rebound. Most German OEM's set up more for underdamped rebound, but over damped compression.

It isn't as much of an issue when encountering a dip, it's the large bumps which creates the event. This is also why they over damp the compression stroke. This give the car more platform and support, while taking more effort to compress the spring, but on large bumps at speed, you will get high speed compression and that energy from the spring will reverse course and with too little rebound damping, the spring is more uncontrolled than controlled and that momentum carries the shock most if not all the way to its rebound stops. It's unnerving when it happens going straight, but loaded up in a corner, it can be very dangerous.

Porsche & BMW just miss finding the sweet spot for rebound damping.

I Uber often and every time I do , I pay close attention to how cars drive and interestedly, some of the best damped passenger cars are Hondas. The newer Accords and Civics have really dialed in damping. It's kind of a fetish of mine, lol.

KelvinC

Right on. Even with my relatively aggressive front camber setting at -2.8, the two local tracks I frequent most are counter-clockwise, and I saw some pretty severe shoulder wear on my OEM Dunlops on the front passenger tire. Still able to get four track days out of them, but I can see the effect of the car pushing in certain corners where I'm fighting the understeer with more steering input...just eats into the tire. I'm happy to be moving onto a stiffer sidewall tire to mitigate some of this, but it's also fun to work on extending the life of my tire by getting better at steering through throttle and brake.

Manifold

Not sure what tires you had, but Cup 2 are terrible in cold and wet conditions. I tried my 992 Turbo S on Cup 2 on a cold and wet track, and the car was hopeless, the AWD didn't help at all. By contrast, I've found the MP4S to be good in cold and wet conditions.

lovetoturn

My car is an early 2024 delivered in September 2023 with bigger tires at 265/305 and ride height is about stock. Maybe it has revised shocks on it, I will look for a number next time I have a wheel off. The bigger rear tires with -3.0 camber and +14 min of toe on TPC offset rear toe links help to stabilize things relative to stock. Because of these things my thoughts and experiences may be a bit more positive than others. I am going to try the DCS box in the next few months ... maybe sooner rather than later after all of this. The DSC actually has slow, medium, and high speed settings for the front and rear of the dampers. You take you original shock setting and then add or subtract a percentage of that under each of these settings. If you use their setting it helps as reported, but I think and hope if one dives deeper into this, even more improvements could be had.

I have not worked with such settings before, but it seems to me if we can soften the rear compression say 10% in medium and 20% in fast; that should allow the shocks to move upward more quickly with less resistance from the car's weight. Then under rebound maybe stiffen it per say 10% in medium and 20% on fast. That way the wheel would come back under more control and be less likely to bounce again. Not sure what the actual numbers would be, but you get the idea. A friend has had a pro driver work on his setup with the DSC, and he is much happier with the car especially just driving down the road on the way home from the track. Rebound is the thing that they played with the most. Not sure exactly what they did, but I will figure it out when I get to that point.

A stock GT4 is 45/80 Nm on its springs, the first modification is 60/80 Nm, and then guys go to an 80/100 Nm track setup all on the stock GT4 shocks. The later being noted to being pretty stiff. As I said yesterday, if someone was that unhappy with their car, for about $400-500 you could try a Swift 90/120 Nm setup when you upgraded the camber plates. That way the labor costs for the work and alignment are really not a factor in the upgrade since you are doing the camber plates already. Then $1400 for the DSC and you are not out $10K. If it works and you are happy, then great and you save a bunch of money. Maybe a set of Surface Transforms rotors to take 46 pounds of unsprung weight off of the car to further address the problem. If you don't like it, then sell the parts to the next person to try it. If I had known all of this last year I would have likely gone with my OEM 100 fronts and softened the rears 10 Nm to 130 Nm to better balance the car to my liking.

If anyone can find out the spring rates of the SRS that would be great. I just looked at my 100 Nm OEM Bilstien springs and unfortunately there are no marking on them to indicate anything about their rate. If Porsche went right in the middle of the Spyder (45/80) and the 4RS (100/140) for the spring rates of the Spyder RS, it would be about 72.5/110. So maybe in reality it is around 70/100 to be a compromise between both cars. Who knows. This is pure speculation on my part, but gives us all some idea of the general rates that Porsche must have contemplated for the SRS.

Manifold

This 4RS is the last of its kind, fairly expensive, and I think it will have collectable value in 5-10+ years if kept in good condition and doesn't accumulate many tens of thousands of miles. So I'm inclined to just do alignment and aero settings with this car, no mods. If I want to mod a car extensively to optimize it for the track, I'd rather do that with a less expensive and non-collectible car, or just buy an actual race car with full cage, etc. and trailer it. To me, modding the hell out of a 4RS just doesn't feel right. I paid for Porsche engineering, and that's what I want to experience.

Taffy66

Cup 2s and as you say a major factor in cold AND wet conditions

alcc

Looks like spring rates on the SRS are same as the Spyder's. Should compare the part numbers.

Autocar: "for the Spyder RS the spring rates have plummeted from 110Nm per millimetre to 45Nm at the front axle and 140Nm to 80Nm at the back."

https://www.autocar.co.uk/car-review.../718-spyder-rs

Car: "How much softer are the springs? Quite a bit – 55% at the front and 43% at the rear over the Cayman GT4 RS"

https://www.carmagazine.co.uk/car-re...718-spyder-rs/

mrd_spy

Don't drive like that then ? that's a driver error. I never turn the wheel more if I am gettng under steer, i drive round it. on a oem geo I did not wear my tyre on the edge at all as I did not drive like that with increase steering angle ! . I waited an extra second to get on the power and fed it in slower.
later in the day I made the car push a bit as I wanted a faster lap time. But at no point did i turn my wheel more to get even more scrubing !, that's a noob error and you just over heat and bend tyre treads backwards which I see quite often at tracks with people who don't know how to drive or control weight transfer.

KelvinC

What’s wrong with you? Why are you so aggro?

I said in the same post that I am working on improving my control of throttle and brake to mitigate the wear. At no point was I blaming the car.

Additionally, I acknowledged my wear was exacerbated by my turning in too much on a particular corner or two. I enjoy tracking because learning and developing skill, speed, and smoothness is all part of the fun.

Spyder75

It was like an ice rink that morning! Then perfect in the afternoon. What a day of two half’s. I don’t think you can draw any conclusions based on the mornings running at all.

Mr. Adair

And some sanity returns..

Mr. Adair

Translation: While both are RS products Porsche designed each car for different end users. I don’t think the assumption the SRS was faster at some track because it’s softer is correct. Too many variables. Driver/conditions etc. The downforce numbers alone are in favor of the 4RS. Too many RS buyers want all of the RS fizz but want the car to ride like a Japanese sedan.

mrd_spy

not aggro, just honest :-) sorry about that :-)

Taffy66

It was very dicey indeed. Great way to cook the rear brakes with ESP and TC constantly working overtime. The two extremes between a 992TTS on MP4Ss and a 4RS On Cup 2s when a track was like an ice rink was quite an eye opener.
Are you coming to Dan's Anglesey track day on May 28th ?

Manifold

If the tires had been reversed, the 4RS would have crushed the 992 Turbo S on the cold and wet track. But on a dry track with equal tires, the 992 Turbo S is faster than the 4RS and 992 GT3, makes them feel underpowered.