Two drives, two tire failures. Possible causes?

[Hi_Fi_Guy]

Some background. Acquired 1971 911T Targa in 2018. Car has 6x15 Fuchs. New tires and tubes installed in 2018. Many years and thousands of miles with zero tire or wheel issues.

Car sat at shop for 7 months during engine and transaxle rebuild. Engine builder logged about 250 miles with no issues.

I received the car back and went for a drive the following day. Passenger side rear tire went flat at speed. Couldn’t find a puncture point but tire was pretty shredded afterward so hard to tell.

Decided to have all 5 Fuchs repaired, checked for roundness, etc. and restored. Then had 5 new tires and tubes installed. Took the car out for a shakedown drive and this time the driver side rear tire goes flat at speed. I had checked tire pressures less than 20 minutes before and all were correct.

My regular Porsche mechanic and the tire guy are searching for answers. What could cause this? Wheel issue? Suspension issue? Coincidence? Or just bad luck?

[creaturecat]

running tubes? seriously?
that could be the problem .....

[LJ851]

Why tubes?

Are you using tube type tires with your inner tubes? Using tubeless tires with tubes can cause failure. Tube type tires are smooth inside and tubeless tires are not.

[Sboxin]

IMHO of course - - just bad luck . . . or you are driving in construction areas . . . Phoenix has a lot of worker trucks carrying all kind of crap including roofing nails and screws ( I got one in a Porsche tire a few years ago also) . . . A friend with a new Macan got 2 flats in a short period of time and she was really pissed - then a rock in the windshield - - I think just bad luck and the road environment we drive in Phoenix (or the West in general).

You should see my son's 911 race car after a race weekend - lots of rock/gravel damage.

Regards,
Roy T

Edit: just saw the tube discussion . . . the tire guys should know better . . .

[Noah930]

Inner tubes? Or valve stems? (Really? You're running inner tubes?)

If inner tubes, then that's your problem.

If valve stems, then likely just bad luck.

Those are my WAGs.

[porsche930dude]

I would say a strong possibility the tubes failed. If the valve stem isnt really at the right spot in relation to the rim it puts alot of stress on the tube. Bending at speed could be the last straw and release all the air at once. Being in a hot dry climate doesnt help. Punctures generally leak down slow unless its something huge.

[Hi_Fi_Guy]

My understanding is these early Fuchs are designed for tubes and can only be run with tubules tires if machined for special valve stems. Even then some people report the tire bead unseating due to the different inner rim design.

Am I missing something? Is there some magical way to run tubules tires on these old rims I have not discovered here or on the Early S Registry?

[smadsen]

I thought tube type wheels/tires generally disappeared in the late '50's.

Back in the day many older tube type wheels would be fitted with tubeLESS tires (as tube type tires disappeared from inventory), but still be fitted with tubes because of the tube type rim profile. It was thought the tubes helped the tubeLESS tires seat on a tube-type rim.

Also could be an old wives tale. Regardless, I think all Fuchs wheels are for tubeLESS tires. You should only use a tube on a Fuch wheel if you were mounting a tube type tire, which I think would be impossible to fine now-a-days.

[Arne2]

OP is correct, Fuchs wheels where fitted with tubes from the factory until the Flat-six version was developed. Deep-six and all previous were designed for tubes.

There are problems finding proper fitting valve stems for the tube-type wheels, unless the stem holes have been machined.

To the OP - what tires are you using? I can't recall if the current CN36 or XWX tires are tube-friendly or not. Most all other tires are definitely not.

[Hi_Fi_Guy]

Originally Posted by Arne2

To the OP - what tires are you using? I can't recall if the current CN36 or XWX tires are tube-friendly or not. Most all other tires are definitely not.

The car is on new Pirelli CN36 tires.

I have not tried the Michelin XWX tires but I recall in some applications Michelin specifying they were to be used with tubes.

[creaturecat]

tubes you say? learn something new every day .....
is there a hole in the tire?
just a hole in the tube?
just the valve stem?
same "damage" on both tires/tubes/valve stems ?

[LJ851]

The vintage tyres website says the new CN36 is a tubeless tire and the pictures of the inside match that description.


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