older tires require MORE tire pressure

[jorton]

Comment is from mareakin's post.
Older tires on my car make the highway feel "bumpy". Can a bad allignment cause the car to ride like that? I had decreased tp which didn't noticably improve the ride, so I'm going to try mareakin's theory today.

This morning I observed the LF tire has what looks like "crazing" on the outside shoulder. Fine squigly cracks about the thickness of spider webs. The other 3 tires don't have it.

Do you think increasing tp will improve the ride?

 

[Corvette Owner]

Look for cracks between the tread, if they are there, I would consider replacing the tires. Tires are only good for 6-10 years, especially if parked outside (in the sun).

 

[CapriRacer]

Originally Posted By: jorton
......

This morning I observed the LF tire has what looks like "crazing" on the outside shoulder. Fine squigly cracks about the thickness of spider webs. The other 3 tires don't have it.

........


If the "spider webs" are on the surface of the tread - the part that touches the road surface, not the part in the grooves - then IMMEDIATELY - I mean today if possible (today is Sunday), but Monday first thing for sure - go to a tire shop and get the tires replaced. Cracks on the tread surface are nature's way of telling you the tire's rubber has lost its elasticity - and a structural failure is in the near future.

Originally Posted By: jorton
......

Do you think increasing tp will improve the ride?


Nope, ride quality is the inverse of inflation pressure. Lower pressure = better ride.

 

[jorton]

Experiment was successful. "Bumpy" ride is smooth again. TP was increased 2psi back, 3psi front to 31 back, 32 front. Car is a 2005 Ford Focus. I need to make 5000 miles more on these tires.

 

[Quattro Pete]

Glad you got it worked out, although I personally find it hard to believe that a 2-3 PSI difference can actually be noticed through butt dyno.

 

[jorton]

Well then I don't know why the ride wasn't bumpy on the weekly trip to town this time. Anxiously awaiting this weekend so I can test it again.