trackdaycareracer

Thanks Van, you're dead on; I'm not an experienced racer. However, I like to get things right the first time, so instead of spending $1.500 on a Quaife ATB now and $3.000 on a GT LSD for GT2/Gt3/968/etc. later, I'd go straight for the GT unit.

Before I order from GT though, I'd like to know if the RSR unit is a better choice: anybody got an idea?

Van

What's the RSR unit? A stock Porsche one?

trackdaycareracer

The G50-style differential, if I may call it that, is used in a variety of Porsche transmissions including the ones for the 968, GT2++, and also for Cup cars and RSRs. I don't know if the 997 RSR or Cup cars have diffs that are interchangeable with the ones mentioned, but I'm pretty sure a 996 Cup or 996 RSR diff will fit a 968 transmission. Apparently, the RSR diff is the top of the line Porsche OEM diff, and if I could find a used one (with partly worn discs) it could be a good match for my stock engine output. I guess the RSR unit has more discs and more possibilities for adjustment than the Cup-diffs. Anyway, I'm not an expert on the topic of differentials, so any advice or bits of information is appreciated.

thingo

I've used a shimmed stock lsd and a 80/80. both plate units, the 80/80 is my preference, both are quiet and fully streetable, and a lot better than the 951 lsd,have heard a few good things about the OS Giken, it has a lot of plates which means it should last longer, and it is very good value.

trackdaycareracer

Anybody use an oil cooler for the diff on a 924/944/968?

Van

Turbo S come stock with a transaxle cooler (and LSD).

trackdaycareracer

UPS brought gifts today, a shiny new Guard Transmissions GT3 Club with 80/80 ramps. I skipped the GT1 and GT2 diffs after much soul-searching, as I figure the stock 968-tranny will die before the GT3 Club does.

Van, thingo: thanks for helping out with the diff selection

smlporsche

+ 1000 on the Gaurds LSD.

It is without a doubt THE BEST LSD in the world. As proof you can ask what the Flying Lizzards do to their GT cars...They tear out the Porsche Competition LSD and replace it with a Gaurds unit...'nuff said.

I would however strongly dissagree with the 80/80 setup. After talking with Paul (Gaurd) at length he reccomended and I bought an 50/80 unit and could not be happier. I get great traction comming out of the corner but without the push (Understeer) you'd get with an 80% lock up on acceleration.

The good thing about his units is that you can change the lock up relatively easily so if one doesn't work for you they can be adjusted to your driving style.

trackdaycareracer

I don't have enough knowledge about differentials to argue for or against 50/80 or 80/80, however my 968 is always oversteering so I actually want a little understeering to balance the car better. With the current suspension, the front is set to maximum stiffness while the rear dampers and sway bar are half soft to get some sort of grip in the rear. This is supposedly a common problem in 968s, whereas 944s are more prone to understeering in some situations as far as I know.

I'm currently running 235 MPSCs front and 265 rears, but am probably gonna go for 265s or 275s up front with 295s or 305s in the rear (the latter will have to be something else than MSPCs), in which case the front will have even better grip than today = more oversteering.

Good to know that the GT diffs are top-of-the-line, makes me feel even better about my new piece of engineering marvel

Nader Fotouhi

Do you have a race class in mind? An LSD is a safe mod, but you better decide what kind of racing you want to do and learn the rules before doing anything else to the car.

GL

Van

Try the BFG R1s. You may be very happy with those.

IMHO, 275/305 is too much tire unless you're pushing 500+ HP. Stick with 245/275 or 245/285.

trackdaycareracer

I have a set goal for best lap time on a certain track, which helps me focus on which mods to go for I'd like to keep the details to myself for a while, as I'm not rushing the development of the car and driver. Hope no offense is taken

trackdaycareracer

The reason I'm looking at wider fronts is that the 235 MPSCs cannot cope with the brake set-up: It feels like they are melting and disappearing under the car when I get to the end of the straight.

I really like the sound of 500+ HP... some day, some day...

Hoosier R6 or A6 are supposed to be the fastest semi-slick tires, so when the spare set of MSPCs are history I was thinking about going with them. However, I'll look at Tirerack's web pages for some BFG R1s. I'm also considering Pirelli Corsa R, they may be slightly slower than the MSPCs but will be better in the wet (helps me from doing 180s).

Van

I find the Hoosiers are just a wee bit "grippier" than the R1s - but the Hoosiers sweet spot is small and tapers off quickly. R1s with a number of heat cycles have more grip than Hoosiers with the same # of heat cycles - and the R1s remain more constant throughout their life.

Both have a bit more grip than the MPSC. The MPSC are great in the damp!

Oddjob

Unfortunately, MPSCs are discontinued..

The other fast R-comp tire is the Kumho V710. Similar to the Hoosiers.