While doing some HHR spring cleaning, I notice the sidewall of my Firestone GTA has a noticible bubble protruding from the side. It was noa always like this, and I'm wondering if this spring's massive pothole craters in NJ may be the cause. I now get a rumble in the wheel at 40 MPH when decelerating, and the tire pressure on that one tire is hard to control.

So could this be pothole induced?

 

for sure

weakened the sidewall from a big hit, and air popped it out

be glad it did that, the tire saved you from rim damage and did its job

 

Probably a good bet that it was pothole induced. Might want to make sure there is no rim damage.

 

I had a little over 42,000 miles on my rear tires leaking air each week so I had a tire stress the tread was about to come off Ford has this problum some years back, so I replaced the 2 rear tires they looked like new no tread wear, glad I had the test done as the tread could come off at anytime.

 

Short answer YES. Do not drive on it go to a Firestone dealer and look into road hazard protection. Get that tire off the road and have the rims inspected!

 

Trade term is "rim pinch". Typically induced by the tire hitting a pothole which allowed the sidewall to compress between the edge of the pothole and the wheel rim creating a cut in the inner sidewall of tire. If the tire is removed and inspected inside at the point of the bubble you will observe that the tire sidewall has a cut. The cut allows air to form a bubble in the outer sidewall which will eventually leak.
Good suggestion is to get the tire replaced ASAP.

 

Actually what you have is an "impact bruise". The sidewall ply's have actually been broken from that impact. The bubble is caused from no reinforcement in that area. The tire does definitely need to be replaced and nine times out of ten the rim will be bent but just the barrel which in must cases can be straightened out but ONLY if its a steel wheel. If it is the cast aluminum wheel, the structural integrity of the wheel is compromised and should also be replaced.