Robert Collins - 96 993TT

Hey guys,
I hope you are doing well. Like both of you, I run RE 730's on my 993 and I love them. They felt a bit squirrely at first, like the back end wanted to fishtail left-right-left-right at any speed over about 60 mph, but that went away after about 300 miles.

By driving 911s, we all know that we will use 2-3 sets of rear tires for every set of front tires, and as usual, YMMV. I have the RE 730's on the front with about 50% tread wear left, and have just installed brand new RE 730s on the rear. With the rears only having about 100 miles on them, the rear of my car feels like a fish swimming on cocaine. At any speed over 60 mph, I have to wrestle the car back and forth because the tail of the car has this weird swaying motion that feels very unstable.

My question for you is this: Do these RE 730s have a break-in period? Or are they mis-matched due to the wear? Have either of you or anyone else experienced this? Is it due to the big Rain Gutter (channel) in the center of the tire having edges on it?

What is wierd is that my car had this same sensation the first set of RE 730s, which eventually went away. That gives me hope. But I really do NOT want to have to drive this thing another 10,000 miles to get to a set of tires that I can drive on with confidence!!!!!!!!!

Thanks in advance for your help.

Robert Collins in Nashville


P.S. - I have the standard 17" cup wheels with standard tires, 255/40 17 in the rear. I have tried 36 psi 40psi and 44psi, but it makes no difference. It feels the same regardless. <img src="confused.gif" border="0">

Robert Henriksen

I'm not Ray or EJ, but I'd suggest two things:

lower your tire pressure - 32/34 is what a lot of us (besides Phil) use on the street.

How's your alignment? When's the last time you had it checked? You haven't let Jiffy-Lube do the alignment, I hope... I realize the squirming goes away eventually, but I wager it's just a symptom of another problem.

Ray Calvo

Sorry to hear this. I really ahven't noticed th rear end problem with RE730's; only time I did was with new BFG Comp T/A in rear and half-worn Yoko A008 in front. Didn't really notice anything adverse with partially worn fronts and new rears.

You've got the same size tires I do apparently with same wheels. I run about 35 psi front & rear.

E. J. - 993 Alumni

Hey Robert,

Like ray I have not had any problems with old fronts and new rears. In fact, I just put on new rears about 1k miles ago with the 15k mile fronts and no problems at all. I really think you have an alingment issue. The current Excellence magazine has an excellent article about 993 suspension.

If you are not sure about the capabilities of your alingment shop, here is how I always find a place. Call them up and act dumb and say something like, 'I think i heard there is some special setting in the rear needing some special tools or something. DO you know what that is and can you adjust it?" If they respond right away by saying "yea sure we adjust the kinematic toe all the time", then you are fine. If they dodge the question, then find a different place. That setting is crucial and can cause the problmes you are describing.

Of course I have no idea why it would go away as the tires wear - they should not need to be broken in at all.

Good luck,

E. J.

Don Magee

I am not Ray or EJ, but I play them on TV. I used to have RE730s, and had minor stability problems on the rear for maybe 200 miles. But, it was not nearly as severe as what you describe. I eventually settled on 32 front and 35 rear.
Have you had the car aligned? You might give that a try. On mine, I had a high speed handling problem when I bought the car and when I took the car in for alignment they discovered that the rear control arm was slightly bent. Changing that solved the odd handling, obviously.

Tom T.

Hi,

Bought RE730's last year from Tire Rack in standard 17 inch sizes. I experienced the same "squirminess" at speeds above 60mph or so on the highway. Returned them to TR on the 30 day test drive warranty. Put on N-spec Pirellis and the squirminess was gone. If you have not had them for 30 days then consider returning them with the <a href="http://www.tirerack.com/tires/Warranty.jsp?make=Bridgestone&model=Potenza+RE730+Gen.+2" target="_blank">special warranty.</a>

Tom

Robert Collins - 96 993TT

Thanks, guys. I will immediately lower my tire pressures and see what happens.

Robert, I wouldn't let a "jiffy lube" touch my 993 if my life depended on it. Last time I even spoke to someone non-porsche, they said "Let me take a look at the engine in that THAAAANG"' as they walked to the front of the car. So I popped the rear and walked back and waited with a huge smirk on my face. Anyway, I will also have it aligned just for good measure. I have a pretty good shop, but I have obviously never asked the kinematic toe question, EJ. I will do that when I call MY shop and see if they know what I am talking about (even though I DON'T know what I'm talking about). <img src="graemlins/a_smil17.gif" border="0" alt="[blabla]" /> <img src="graemlins/oops.gif" border="0" alt="[oops]" />

E.J., I will also read that article on 993 suspensions in excellence. I get it at home, along with Pano and 911 & Porsche World. All great pubs. I just have to find time to read all three.

Finally, Tom, I also bought from the Tire Rack, but made a small mistake. I was buying four S-03's for my 1991 M5 and I knew I was about to need rears for the 993, so I went ahead and bought them. Unfortunately, Tire Rack has a 90 day limitation to their policy and my tires sat in the garage for about four months. They did replace one of the tires due to the fact that it was bad, but I doubt that they would change out for me now, even with only about 100-150 miles on the tires. Even if they did, I have two RE730's on the front with alot of life left, and I DEFINITELY do NOT want to have the not matching tire issue again.

Anyway, I will report back as soon as I have these things done. As usual, I want to say that I love this board and all the great people who are always willing to help a fellow Porsche enthusiast. I always feel indebted to this board because I feel I take more than I give due to my lack of technical expertise of these subjects. But if anyone ever has any wax or detailing questions, I'm all ears <img src="graemlins/xyxwave.gif" border="0" alt="[bigbye]" />

Thanks again,
Robert

Robert Collins - 96 993TT

HA HA HA HA!!!

Hey guys, I just noticed that everyone has a title on this board based upon their historical level of activity.

EJ is a guru, Robert and Ray are Senior Members, and I'm just a User. After my last statement, how appropriate is that?? <img src="graemlins/roflmao.gif" border="0" alt="[hiha]" />

Anyway, Thanks again for all your help!!

E. J. - 993 Alumni

[quote]Originally posted by Robert Collins - 96 993 C2 cab:
<strong>EJ is a guru, Robert and Ray are Senior Members, and I'm just a User. After my last statement, how appropriate is that?? <img src="graemlins/roflmao.gif" border="0" alt="[hiha]" /> </strong><hr></blockquote>

I am not really a Guru around here, John just won't remove it from my name.

Anyway, I really think its an alingment issue. Hope it all works out. Keep in mind that you have to re-do the alingment after going to upgraded suspension, so now might be a good tme to get the PSS9 system so you only have to pay for an alingment once.

E. J.

Robert Collins - 96 993TT

EJ - If I did that, what can I expect that to cost me, and where is the best place to shop for it. If you need to e-mail me privately to avoid the non-commerciality of the board, please feel free.
Thanks

E. J. - 993 Alumni

I would call [edit]Board tech supremo Steve Weiner at Rensport systems <a href="http://www.rennsportsystems.com/~porsche/993.html" target="_blank">(link here)</a> to talk about it.[end edit] I am not sure how much it costs exactly, but probably around $3k including the adjustable sway bars. This is a great setup and lots of guys are using it for street and street/track cars.

If you have never changed your shocks, you can bet they need to be replaced anyway, so might as well pull the trigger on a sweet upgrade too.

Good luck - Steve will sort you out.

E. J.

Robert Collins - 96 993TT

GOD BLESS AMERICA!!!! Man, thanks guys! What a difference a few pounds of air makes. I measured the tires cold at 39 (I last filled them up to 44 when they were hot). I deflated them cold to 34 all the way around and it feels 1000 times better.

There is still a VERY slight left to right wiggle from the rear, but my first set of RE730's did that same thing for about 300 miles, then went away. I just couldn't understand why my first set had a little wiggle that eventually went away, but these were MUCH worse. My only explanation is that when you have front tires well broken in, they already have their wear pattern in them. New rears really don't match up with them until they can develop a wear pattern as well, therefore you get a little wiggle until it does so. This is only my stupid guess.

These only have about 200 on them, so I will hold off on the alignment for a little while. I asked my mechanic Wicky if I should go ahead with the alignment anyway. He asked, "How did your tire wear look when you took the old ones off?" I said they wore perfectly even, so he replied "Then it doesn't sound like an alignment, so don't waste your money, yet."

Anyway, moral of the story: Tire pressure can make a big difference for day-to-day or track driving, but it's even more important with brand new tires. I'll keep you guys posted if the shimmy goes away in the next 2-300 miles.

Thanks!!

Robert Henriksen

Glad to hear it's better. I'd be curious to hear if you notice any additional difference if you went another 2 pounds lower in the front.

Robert Collins - 96 993TT

I'll try it. What difference are you anticipating??

Robert Henriksen

Hey, if I told you I'd be compromising the experiement!