Sumitomo HTR P01's mini review and more
12-09-2014, 08:23 PM
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Sumitomo HTR P01's mini review and more Car: '94 Z28 Convertible, 83k miles, stock suspension.
I got a new set of tires in June, Sumitomo HTR P01's, H rated. 245/50/16 size. An alignment was done at the time. I drive the car only on the weekends and have 30 psi air pressure in them.
So far I like the way the tires handle and drive. Nice and quiet, perfect on the highway. Good stable tight cornering.
My only beef, while not major right now, is that they have a lumpiness that is developing to them at 50-52mph. The whole car moves up and down enough to shake the passenger seat back if no on is riding in it. It only happens at that speed. The tires were balanced and new at the time of the install and they rode great.
I read up on flat spotting, and it seems that at 30 psi, these tires flat spot during the week when the car is in the garage. They shake a little at all speeds for the first few miles then stop. For the rest of the weekend, the car will shake in the 50-52 mph range.
Do you guys stick to the 30 psi? Or are the sidewalls softer on the Sumitomo's where I could go to 35ish and maybe prevent some of this flat spotting (if this is what it is)?
I got a new set of tires in June, Sumitomo HTR P01's, H rated. 245/50/16 size. An alignment was done at the time. I drive the car only on the weekends and have 30 psi air pressure in them.
So far I like the way the tires handle and drive. Nice and quiet, perfect on the highway. Good stable tight cornering.
My only beef, while not major right now, is that they have a lumpiness that is developing to them at 50-52mph. The whole car moves up and down enough to shake the passenger seat back if no on is riding in it. It only happens at that speed. The tires were balanced and new at the time of the install and they rode great.
I read up on flat spotting, and it seems that at 30 psi, these tires flat spot during the week when the car is in the garage. They shake a little at all speeds for the first few miles then stop. For the rest of the weekend, the car will shake in the 50-52 mph range.
Do you guys stick to the 30 psi? Or are the sidewalls softer on the Sumitomo's where I could go to 35ish and maybe prevent some of this flat spotting (if this is what it is)?
12-10-2014, 01:06 PM
#2
On the street I tend to run about 3-4psi over the manufacturer's rating, I've had good experiences with treadwear and street handling at that level. When I Autox I adjust to keep them just a hair above factory (that's where I'm running my best times, dragging would be different) sometimes I take air out because they are hot and sometimes I put it in, just depends. Keep in mind this is my experience and at this point I'm running aftermarket wheels.
Higher PSI on the street will impact ride quality, but on OEM suspension you may not notice.
Higher PSI on the street will impact ride quality, but on OEM suspension you may not notice.
12-10-2014, 01:54 PM
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It's not uncommon for a tire that has set it one spot for a week to have a little flat spot. These flat spots will work themselves out after driving for them a few miles and the tire getting up to temps. If you continue to have a vibration around 55 MPH this is usually a balancing issue. I would recommend having the balance re-checked if you have not done so already.
12-11-2014, 08:13 AM
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I have aired them up to 34 psi as they are sitting in the garage. This weekend I will drive the car again.
I don't drag or autoX the car, it is a "lets go to the car show, then get ice cream with the kids afterward" car.
Upon first driving down my street after sitting for a week it bounces like crazy, then settles out after a few miles. However, the 50-52 mph range bounce never goes away. I'll see if the air pressure helps them a little, if not I'll get them rebalanced and go from there.
I don't drag or autoX the car, it is a "lets go to the car show, then get ice cream with the kids afterward" car.
Upon first driving down my street after sitting for a week it bounces like crazy, then settles out after a few miles. However, the 50-52 mph range bounce never goes away. I'll see if the air pressure helps them a little, if not I'll get them rebalanced and go from there.