H.H.Chinn

Congratulations! When you check your hot engine's oil, park on a level spot for greater accuracy

grwoolf

If it is truely a pinhole leak with no structural damage to the tire, there is no danger driving hard or any other way IMO. The worst thing that can happen is the patch comes off, and you loose a few psi of pressure over the next week or so. I'm talking about a pinhole leak, not a nail in the sidewall where the tire could quicly loose pressure. I get mesquite thorns in my truck tires (including sidewalls) and shops just will not patch them on the sidewalls. They leak so slow that I just make sure I check the pressure every week and they are never more than a couple psi short. I had a co-worker almost killed in one of the explorer roll-overs because of low tire pressure, and a weekly tire check on all my vehicles has been a Sat. morning ritual since then (even the one with tps).

993-C4S

Can't wait to see the pics as I have a '97 C4S in Forest Green and have yet to see another (Cashmere Interior). Post pics, post pics!!! oh yeah, get a new tire too!!! Our cars were meant to be driven hard and fast. I would never feel safe doing that on a patched sidewall. There's a reason tire shops won't do it...

jwdwight

Thanks for all the advice....it's dipstick for oil checks and a new set of rear tires.

grwoolf.....its a pin hole but not a two or three day leak more like one day and pressure is down to 15 psi or less. Doesn't go completely flat but its low. I will just get it behind me and buy a new set. The fronts are almost new so I will only replace the rears. All four are some brand/model.

Cheers!

Kein_Ersatz

+1

Sounds very British in appearance, once had a 3-series in the same color combo, it was gourgous . . .

Harold

Congrats on the purchase. You will never go wrong with a 993... I still have my C4S and will never let it go!

95C4VanIsle

I seem to recall reading in Adrian Streather's book that when replacing tires on a C4 that it is best to replace all four at the same time. Since rear tire wear occurs faster than front tire wear, many of us just purchase new tires of the same brand for the rear tires, especially on a C2. If the rears are worn the fronts may still have decent tread but the rolling circumference on the fronts may not be the same as the two new rears. The rolling circumference front to rear should be within, if my memory serves me correctly, about 3% of each other or it can affect the AWD system. For the price of a new set of four tires these days (Sumitomos in particular) I would personally replace all four.

kjr914

Replacing 2 sets of rears to 1 set front tires is a Porsche 911 standard (same on my '86 and '96). Yes the front/rear rolling circumfrence has to be close (I thought I saw 5%, but not sure on that).

As a sanity check, I did the math:
[geekOn]
What is the difference in rolling circumference after a tire is worn down ~0.25" (a extremely pessimistic guesstimate of tread depth) in its radius compared to a new tire?


Reference on tire size calcs: http://www.tirerack.com/tires/tirete...e.jsp?techid=7
My rears are 285/30R18, so tire height is: 285mm*0.30 / (25.4mm/in) = 3.37"
D=Dwheel+2*tireHeight, so D=24.74"

C= 2*pi*R = pi*D with C=circumfrence, R=radius, D=diameter

The % change in C:
deltaC% = 100 * (C1-C2) / C1 with C1 new circumference, C2 worn circumference.
deltaC% = 10 0* (pi*D1-pi*D2) / (pi*D1) with D1 new diameter, D2 worn diameter.
deltaC% = 100 * (D1-D2) / D1
deltaC% = 100 * 2*treadDepthChange/D1

deltaC% = 100*(24.74-24.24)/24.74
deltaC% = 2.0%

Not too much change really. And I've made a very pessimistic assumption on tread depth difference. Doing the math again with 1/8" tread wear gives 1.0%.
[/geekOn]

So just change the rears if the fronts are ok.

my 2c, YMMV...
kjr

95C4VanIsle

Thanks for the input on the rolling diameters. I wish I remembered all that math. It might have saved me some $ over the years.

jwdwight

Thanks guys.* The fronts are almost new....less than 1,000 miles so hopefully I am ok.* I think I am just going to replace the rears.

95C4VanIsle

Defintely prudent with such low miles on the fronts.

techsis

Go ahead and post some dirty pictures (non-detailed) of her.

rj777

Hi Jon,

Congrats on your purchase. Can't wait to see the pics. You have a unique car. As others have said, there aren't many Forest Green 993s around. Even less '98 C4S's.

Last fall, when I saw this car advertised (I think it was in Pano), I tried to interest of friend of mine (in Ft. Lauderdale) in this car. He is a fan of 993s and of Forest Green paint. He passed on it for some reason or other. It might have been a purely cosmetic reason. I believe this car has a black leather interior, right?

It really seemed like a great car for someone.

I hope you are able to get in some miles soon and can post your driving impressions.

Best regards,

rj777
RickJ

Bergamasco

I bought mine in November. I look forward to seeing some pictures of yours. Congratulations and Happy motoring. - Glenn