Cheburator

The GT-R is going for 4-wheel alignment and ride height adjustment tomorrow. I have been given some settings, which supposedly are Porsche Motorsport's own for the Nurburgring. I will leave it to you guys to spot the odd one out. Any racers care to comment? The car runs on 18 x 10 ET47 with 265/35/18 and 18 x 8 ET55 with 235/40/18

Ride Height = 90mm (Front & Rear)
Camber, Front= -2deg,10'; Rear= -2deg,05'
Caster= +5 deg
Toe in = +5' front overall, +12' Rear (each side)
Tyre pressures= +1.9bar on 17/18 inch wheels

Thanks,

Alex

FlyingDog

I know nothing about the allignment, but tire pressure is quite low.

Jim bailey - 928 International

Ride height measured where ?? 90 mm is not much !

Richard S

Ride height 90mm? My front was 120mm (measured from correct spot) when I got it a couple months ago. Scraped EVERY driveway, speed bump, etc. Front tire was inside the fender lip. Turns out, the previous owner removed the adjuster nut, no way to raise the height. I now have Koni's (with adjuster nuts) and at 170mm height at all four corners and it looks like a monster truck compared to the low-rider it was before. Front tire is now a couple inches below fender lip.

So, at 90 mm, how do you turn the front wheels without them rubbing the inside of the fender?

Rich

drnick

alex that will be awesomely low! will you be able to get on the ferry? i think the castor and front toe specs sound good, ive had up to 1 degree of camber on the front and its ok on the street/dosent wear the tyre. you had just better hope there isnt any rain, what kind of tyre are you running?

slate blue

Hi Alex way too low, that is 100 mm or 4 inches too low at the front and almost the same amount lower at the rear. I think 150 mm at the front and 140 or 150 at the rear, to many things on street roads to take out your sump.

I do wish you the very best at the ring, I only wish I could be there.

drnick

i dunno greg, my 86 sits at 160mm at the front and clears about everything and im sure its possible to go lower than this just not sure by how much.

Jim bailey - 928 International

The stiffer your springs the lower you might be able to go since they will compress less under cornering loads but I have already ground off half the head of the lower front suspension arm bolt of the old very brown 1980.

Cheburator

Thanks for the comments guys!

I also doubt the 90mm ride height setting and it felt like the odd one out! Knowing the Ring - it is quite a bumpy track, I cannot believe that Porsche would have specified 90mm - it does not allow you to climb certain kerbs, not to mention that the car would certainly bottom out and scrape the sump/ X-pipe in a few places...

I think that I will go with 150mm all round, given the 800lbs front Eibach springs and 525 rears, which I got with the LEDAs.

I am running Bridgestone Potenza SO-2 N2 265/35/18 (Treadwear 140, Traction AA, Temp A) at the rear and Falken FK452 (Treadwear 240, Traction AA, Temp A) 235/40/18at the front.

Alex

Jim bailey - 928 International

Tire pressures may be a bit low as well for street tires ...

FlyingDog

I'd say the 90mm measurement is correct.
https://rennlist.com/forums/928-forum/273637-front-end-alignment-question.html
They're just measuring according to the manual instead of the method most people use.

SwayBar

Lowering a car too far will put the suspension geometry out of whack, and the car will not handle as well as it could if it were operating in it's engineered 'sweet spot'. With stock suspension hardware, the factory stock settings will be best.

There were Z06/T1 racers who were 'slamming' their cars 1 1/2 to 2 inches in order to lower the center of gravity, and to improve the looks. However, their lap times suffered. After taking the car to a knowledgeable race shop, they raised it back up to 1/2 an inch from stock, and lap times plummeted immediately by 2-3 seconds a lap, a HUGE amount. A brand new Z06 included a a VCR tape telling would-be trackers to only lower the car 1/2 an inch on all four corners for best performance.

If the 928 in question is 4 inches lower than recommended without any other changes, I suspect the car will not handle as well as one set up with stock specs. Bump-steer for one will be horrific.

Of course, lowering a car is good as long as one also makes the necessary hardware changes to the suspension so that it can operate in it's sweet-spot again. Lowering a car too far is no free lunch.

drnick

i think the racers, mark k et al do have there fronts set around the 110mm mark??

C.F.

I think MK's car is that low as well & he drives it to & from the race tracks , a friend of mine runs his car at 125mm front & rear on the street here in the UK with no problems & it does handle better than the stock ride height

John

drnick

alex, any feedback or have you already taken out your sump/understeered off the road??!