DCLee

You raise an interesting point. I don't really have enough experience with the Sport Cups to address it fully. I think that in a 90-minute enduro, there would be a potential advantage to having the more consistent tire. Plus, if it rains, the Michelins offer some decent grip. As I said, I'm sold on the tires for DE events. Well worth the price.

Rgds,

Lee in D.C.

tom_993

[quote]Originally posted by PeanutinCA:
<strong>
Would I see improvement in times fitting an LSD? I am told for the Streets it's good for maybe 2 seconds?</strong><hr></blockquote>

Dylan,

This seems a bit optimistic to me. Do you feel one wheel slip when you get on the throttle coming out of a corner? If so, get an LSD, otherwise… You should be able to feel this fairly easily. I feel it all the time in my truck, especially in the wet. I go around a slow corner at an intersection, get on the gas, and one rear wheel spins. When it happens, you know it!

Tom
’95 993

PeanutinCA

Hi Tom.

I definitley feel the wheel spin, inside wheel of course. I know the benefits of having LSD, I'm just weighing the dollars Vs time benefits Vs just using the more expensive MPSC tires (which is an expense in itself)? It was advice I was giving by someone else that improved their lap times by 2 seconds by fitting an LSD. That was at the Streets. I was wondering if a track that was not as tight and had more flow (the big track) would give you the same benefits? Thought maybe someone had done the change over half was through their season and could "share notes"?

Martin,
how does the longevity of the tires look after your one weekend on them? Did you also drive the car too and from the track? And, did you find they would pick up a lot of track rubber in big chunks? I get that a lot on the Kuhmos but, I'm expecting that is common to any tire? One other thing, I have one bent wheel up front, they can pretty much balance it but half way through the day with the rubber build up the vibration gets pretty bad. Short of getting under there and removing the chunks, is there any other tricks to stop/avoid/eliminate the rubber (marbles) build up and thus vibrations?

Thanks,
Dylan.

Martin S.

[QUOTE]Originally posted by PeanutinCA:
[QB]Hi Tom.

"I definitley feel the wheel spin, inside wheel of course. I know the benefits of having LSD."

WORD TO THE WISE: The factory LSD is going to fry, sooner or later, probably sooner. Mine went from brand new to "toast" in a short period of time. My next LSD is going to come from Guard Tranmsmission (GT). This is the brand of choice for the racer types.

"I'm just weighing the dollars Vs time benefits Vs just using the more expensive MPSC tires (which is an expense in itself)? It was advice I was giving by someone else that improved their lap times by 2 seconds by fitting an LSD."

See above...it had better be a good LSD and you had better be willing to deal with the push induced with the LSD. A stiff rear bar would, the 21mm Turbo bar is a good start. Adding a factory LSD is at least $1,200 for the LSD + the labor to install it. You can add GT clutch disks to the factory LSD, very spendy, about $800 I was quoted.

"That was at the Streets. I was wondering if a track that was not as tight and had more flow (the big track) would give you the same benefits? Thought maybe someone had done the change over half was through their season and could "share notes"?"

First of all, potential competitors are not usually willing to share their notes, but I am, well, to an extent....I don't know if my LSD works any more or not. There is a "factory" recommend way to check them out. It is a little involved so I have put it off. I can tell you that the LSD is less than optimal and the car gets around Willow Springs real well.

"Martin,how does the longevity of the tires look after your one weekend on them? Did you also drive the car too and from the track? And, did you find they would pick up a lot of track rubber in big chunks? I get that a lot on the Kuhmos but, I'm expecting that is common to any tire? One other thing, I have one bent wheel up front, they can pretty much balance it but half way through the day with the rubber build up the vibration gets pretty bad. Short of getting under there and removing the chunks, is there any other tricks to stop/avoid/eliminate the rubber (marbles) build up and thus vibrations?"

Dylan, the tires looked nearly brand new. If you are anywhere near Lake Forest CA, I can arrange a "viewing"! There is plenty of tread left. I am looking for 3+ weekends on these tires. I only go two (2) with Kumhos. By the end of the second weekend, one of the tires was shot, usually the left rear, the tire that takes the biggest beating at Big Willow.

Bottom line, dial some negative camber into your car and bolt on the Michelin Pilot Sport Cups. You'll see 2+ second improvement on the Big Track. According to my pal Cupcar, split the difference on the improvement, 1/2 to the tires 1/2 to the alignment. I added LSD to my 80SC and didn't see any 2 second improvement. But that was my experience.

PeanutinCA

Martin,
your making my head spin. And I thought zooming around in the car was going to be easy! OK, would a 95 come standard with LSD, I thought not? I've had my car on the hoist and done the wheel turn business but they both go in the same direction, not the opposite so I figured on no LSD?

So the big dollars of LSD doesn't equal long lasting, or do you just need to spend the dollars to get the longevity?

I have the neg camber all round so I am ready there. I have the RSR sway bars on PSS9's, is that enough or are you suggesting a bigger rear bar again?

[quote]..potential competitors are not usually willing to share their notes..<hr></blockquote>

I come from Australia, we drive on the wrong side of the road, what would I know how to drive!! <img src="graemlins/c.gif" border="0" alt="[ouch]" /> Not sure how much comp you will find here, don't have the fast mods yet. Just safety items, suspension and sway bars, oh and tires (Kuhmos).

[quote]If you are anywhere near Lake Forest CA, I can arrange a "viewing"!<hr></blockquote>

Not quite at the moment. I'm in Aus getting my own "mods" done. Just a minor spine adjustment!! A little <a href="http://www.spinalneurosurgery.com/CR_aritificial_disk.htm" target="_blank">Artificial Disk replacement</a> in the Cervical spine. A fun little procedure, I hear it's good for about a second!! <img src="graemlins/oops.gif" border="0" alt="[oops]" />

Cheers,
Dylan.

Greg Fishman

As Martin said get a Paul Guard LSD and for a street car make sure it is the Torsion Biasing Diff, not the GT version with the ramps.

The Torsion Bias or Torque sensing LSDs only work under acceleration and will power both rear wheels and divert power to the other if needed. These do not have plates and should last much longer than a plate type diff.

They will also produce less understeer than a ZF clutch type diff. The ZF LSD does have more set up options with switchable plates to allow more lockup under braking and/or acceleration.

The benefit of a ZF LSD is that it will help stabilize the car under breaking and allow you to trail brake more and with greater stability. But unless you have the ability to make suspension changes stay with the Torque biasing versions. Guard makes the nicest versions of these and if you see one before they are installed you would agree they look like works of art, I think they cost about $1500. Quaiffe also makes them and they are also a good piece.

JohnM

For those who have a Porsche LSD already: if the OEM plates are wearing (as they seem to do quite rapidly with track use) you can just fit a set of sintered plates, a lot cheaper than replacing the whole diff.