There has been much discussion about the deterioration of ride when going with low profile tires, and even more on the "correct" tire pressure to run. I don't know if these comments will add or detract from the confusion...

I swapped from stock 16" rims to 18" Lorinsers with Conti CH95 (235/50 front, 255/45 rear). Overall, I liked the ride (a little stiffer, but not much), but there was an annoying "shudder" when hitting the correct pothole or speedbump.

I was running 35psi, which is over the recommended pressure (which is 27psi), but then I started thinking that since the new tires were rated at 51psi, then comparing them to the 16" suggestions for pressure might be incorrect. I inflated the tires up to 41psi (I figure since the recomended pressure is 10psi below the tire rating pressure, then maybe this would be more accurate when going to different tires - that 10psi below max is more accurate than 27psi for any size...)

The ride might be just a little stiffer, but barely noticeable. However, the "shudder" and other undesirable wanderings have been totally eliminated. Overall, I would have to say that the "quality" of the ride is better at 41 than 36 (and I can only assume it is due to the fact that 36psi is just too low for these tires to "work" properly).

I don't know if I'm on to something here, but I certainly am running 41psi in these from now on...

Actually, the reverse is usually true.

Lower tire pressures result in a softer ride due to the tire being more compliant to bumps and such. Higher pressures yield a stiffer tire and a harsher ride.

But since you are using low-profile series tires, you don't have much room for tire compliance since there is less travel available from tread to rim...that is why a higher tire pressure works for you. With a low tire pressure, you probably have the tire literally hitting the inside of the wheel hub on hard bumps!

Gas mileage improves somewhat due to less heat and friction with higher tire pressures. And doing the 5 or so psi in your case was a cheap ride comfort formula for you!

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2009 ML350 (106K) - Family vehicle
2001 CLK430 Cabriolet (80K) - Wife's car
2005 BMW 645CI (138K) - My daily driver
2016 Mustang (32K) - Daughter's car

Yes, I understand that the reverse is usually true... (FWIW, motorcycles that I have built have finished on the podium at Daytona Race of Champions 3 times, so I have a clue as to vehicle dynamics).

That is why I made the post - it goes against logic, but from the driver's seat the higher pressure is truly "better" in almost every aspect.

-David

Very interesting post. I'll have to try it. I've been running 36F/38R in my new 16" wheels with 215/55 tires (stock was 15", 195/65). I too have noticed ride problems going over potholes esp. at speed -- not so much a "shudder" as a scraping sound....

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Steve
'93 400E