I have jack stands and a fast pump, low profile jack .

 

if there is a nail and it is still in the tire, the pressure will hold for sure... it will be a very slow leak.

If the leak is a major one, your tire would have been flat in half a day or even less, given the weight of the car is pressing on the tire.

Also, the leak probably have happened for a while already before you noticed it, you probably been driving with it for a while

 

Thanks Will.....maybe I'll make the long journey and come see you this evening or Saturday morning.

Actually, when I went to take the car out for a drive last sunday, my dash warning red light was on indicating the tire was down 8 psi. Checked with a guage and yes, it was down to 32 psi. Pumped it back up to 40, took it for a drive and the pressure held steady. Tuesday after work, checked again with a guage and it was back down to 32. So...its a slow leak and TPMS seems to be working perfectly.

 

Ok. Had a look at the tire. Not a nail. Not a screw.
More like a piece of shrapnel.
Im worried about the location.

Professional advice neede here. (Zookie? )

Can this be plugged? Its kindof on the tread side of the transition radius to the sidewall.

On the outside, the piece of metal looks about 1/4" long.
Plug? Or new tire?

 

Too close to the edge to plug

 

That will require a new tire. Or possibly two new tires

 

Agreed. The CT plug kit likely won't fix a gash that wide.

 

Today, I discovered a nail in the RR tire in close to that location ... where tread meets sidewall. Decided two new rear tires needed. I think the same for OP's puncture.

 

Do you think I need to replace both?
I've got about 6 K on these (6000 km)

I'll replace this one now and then put the car away for the winter.

What mileage can I expect to get on these tires, generally speaking.
I don't drive too agressive or track.

 

Mine is at a little more than 50% of new thread depth so I'm changing both. I drive hard, fast and aggressive [quick lane changes, hard into corners, etc] so I won't chance unpredictable handling with changing only one tire in the rear.

I'd say 15k of use and you'd be doing ok. If you are about to put the car in storage, then I'd put the spare on it and buy two new tires when you take it out of storage.

 

Definitely needs a new tire. Cant patch a slice. been there.
I would think you'd easily get 15-k on a set of rears. Double that up front.

 

I had a blowout on the left rear last year on the QEW from debris. All 4 tires were fairly new, 5000km or so at the most. I just replaced the one, and I never noticed the difference. If it's the front, I'd replace the one but put them on the rear so the fronts are matched.

 

X 5 ... new tires. Pair. Keep the other used good one as a spare.
You'll never need it, if you have one.
FF 2018, why do I still have that stupid spare tire, its in the way, its dusty, why did I ever keep it.

 

For the folks who do roadside repairs with a plug kit, which portable jack do you recommend? AFAIK I don't have a jack in my Cayman frunk.

 

I have a factory (996) jack, and a piece of 2x6 for soft ground. I'm not sure what the Cayman jack points are like but I'd look for a hand crank scissor jack as they are compact, fit under a low car and less likely to fail as compared to hydraulic jacks.
I'd also recommend carrying a breaker bar with the appropriate sized socket for the lugs. Nothing worse than snapping a factory lug wrench on the Friday of a long weekend...