Our 2007 997 4S has been exhibiting some rumbling sounds from the back end recently. (We purchased the car several months ago after a favorable PPI.) I'm thinking the rumbling is tire related since the PS2s are just about ready for replacement. Guess it could be a balancing issue also.

Then I thought...what if the previous owner filled the tires with Nitrogen? I've been using air. Does anyone know what the effect would be? I don't know the physics of which is heavier etc. etc.

May be unrelated but some time ago when I topped of with air I noticed a white (almost like corrosion) substance on the valve stem threads that made the plastic caps difficult to remove - had to use vice grips. I've since used scotch brite to remove the residue. Just wondering if any of these observations may be related to the rear tires rumbling. Any advice on what my next move should be would be greatly appreciated.

Thanks

 

There would be no harm to mix nitrogen with air. White stuff could have been some type of goo to make the caps stay on, also nothing I would worry about. Better question is why you had to top off your tires in the first place?

 

Is it possible the tires have flat spots from sitting in the same position too long? How many miles are on the car?

J

 

White stuff could be tire sealant - if there was a leak and it was "fixed" with sealant, there could be a slow leak and a balance issue. I would go to a good tire store and have them look inside.

 

I agree, but as the OP said, it is almost time for replacement. I would just get them replaced. New tires make a big difference on the way the car feels on the road.

 

[quote=xXxGhotimanxXx;2812275]Is it possible the tires have flat spots from sitting in the same position too long? How many miles are on the car?

Car currently has 57xxx miles. Just about ready for the 60k service. I was hoping to put off any tire replacement untill then but it seems that may not be possible - fronts are still good so I'll be staying with PS2's.

Making arrangements now for a visit to my local tire service center - whom I trust with P-cars.

P.S. didn't think of tire sealant as a possible white 'corrosion' issue on the stem threads.

thanks for the responses....

 

It is with 90% probability sealant that got squeezed out - I had same exact thing on old honda when I used such thing on a road and yes it completely kills balancing. just get new tires and it will be over. I would get new valve stems too - it is very minor expense, get nice stainless steel stems if you have black rubber ones now.

 

Again, thanks for all the reads / replies........I have an appointment at an independant P-car shop for next week (mid week) I'll report findings hopefully by end of next week.

 

UPDATE: Rumbling noise was 100% tire related. Ended up going with Yoko Aven Sport as PS2's were not available.

thanks again for all the comments......

 

I have had Advan Sports on a previous car, they were great tires.