I recently bought a set of Sumitomo HTR200 tires for my HCH-II, to replace the OE Dunlops which were shot after 25000 mls (supposedly due to the Civic rear upper suspension link problem - I did get the replacement links fitted under warranty).

After reading various posts which recommended increased inflation pressure (anything up to 38 psi cold or even higher) to improve gas mileage, I inflated mine to 36 psi. When I went to the tire shop for my first free rotation/balance, I asked that they inflate to 36 psi. The tech flatly refused to do it.....he said "Believe me, if you overinflate tires on a Honda, they will wear out in no time".

Well after I left the shop I inflated them back up to 36 psi anyway, and I thought the comment a bit odd...was he talking about ANY Honda, including a Pilot, Odyssey, Accord etc etc as well as a Civic? Surely such a characteristic would be vehicle-specific, not manuafacturer-specific?

Anyway, many of you hypermilers obviously would not be seen dead in a Civic with tires inflated to less than 36 psi....Could there be any truth at all to such a comment, or is it just the usual conservative tech attitude?

Any opinions?

 

I run 50psi, and ended up just short of 45k miles when I replaced my OEM Bridgestones. All four had 3/32" tread left, if I remember right. Treadwear was even, though I haven't been able to get up underneath to tell whether or not I've got the wrong control arms.

 

If you look at the pile of worn-out tires at a tire shop, you will see that the great majority of them are worn out at the edges, but not in the middle. That happens because they were operated with less pressure than needed. Most of the rest are damaged or punctured. The few that are heavily worn around the middle are the old "bias ply" design, not radials.

Radial tires have steel belts that prevent the tread from buldging out in the the middle. Because of the steel belt, the middle cannot expand to a greater diameter due to pressure. If operated with the pressure recommended by the tire manufacturer, the tread is flat across the full width of the tire, and it wears evenly across the full width of the tire. If operated with less pressure, the weight of the car deforms the tires during turns, and that deformation causes the tires to wear more at the edges. Higher pressure minimizes the deformation during turns, and minimizes the excess wear at the edges of the tread.

This leaves the question as to what pressure is recommended by the tire manufacturer. That is easy to answer. The tire manufacture puts a recommended max pressure on the side of the tire. My Michelin tires say to inflate them to 44 lbs of pressure. Auto manufacturers print the minimum pressure in the owner manual, and on a placard in the door frame. My Camry says to inflate them to a minimum 32 lbs of pressure. The thing to note is, the number printed in the manual and on the car is the minimum pressure, not the maximum.

Anywhere between those two pressures is safe. The minimum pressure will give you a softer ride, at the expense of fuel mileage and tire wear. The maximum pressure will give you maximum fuel mileage and minimum tire wear, at the expense of a stiffer ride.

 

There was an extensive discussion on this over in the Ford Escape Hybrid area. Suffice it to say that there were two canards put out indicative of forgetting 8th grade science:

Higher pressure does not wear the center of the tire.

The steel belts prevent tire face deformation with higher pressure.

Bunk.

 

Higher air pressure tire run cooler. This is the main reason for less wear. Less friction less wear.Hal

 

I don't know the physics behind it, but I got almost 60k out of the OEM Dunlops running at high pressure (over 50psi) and have over 40k on the replacement set (Bridgestone Insigna I think) running at an equally high pressure and they still have plenty of tread left. With over 100k miles on the car, I'm still regularly getting 51-52 mpg per tank (unless my wife drives it).

 

Hi Neil!
You will get half that if you run 30 or 32 like Honda tells us! Its funny, I belong to another sight re Honda crv's and I mentioned I run the max. cold presures marked on the side of the tires! Well you would have thought I committed a crime! You should have heard the ridicule comming in my direction! Someone asked what presures members run, I told them I run 44, Well!!!
cheers,
Hal

 

Well, you know what they say - "Opinions are like Hemaroids - Every ^$$ *0!# has one" J/K

If you had to choose between over inflation and under inflation, under is MUCH worse. Under inflated tires cause blow outs by over heating the tire. (and wearing the thinner side wall).

The affect on MPG is clearly evident. I can almost use the MPG indicator as a tire pressure guage. If I see my mileage drop below 50, it is usually time to add more air to my tires.

 

I have never had the ***** to go over 44 lbs., but it sounds as if I should! I have my HCH2 in for the upper control arm issue next week. Hope I get new ones as the noise from the rear is getting to me. Hal

 

First these are technically called "balloon tires" for a reason: other than the wheel itself it is a fully flexible rubber "Balloon." The amount of tire on the road surface is proportional to the pressure inside the tire. If your car weighs 2,000 lbs and each tire supports 500 lbs, and if the pressure inside it is 50 psi then there will be 10 in2 on the road surface... its that simple.

Second the steel belts are flexible, they serve to stabilize the tread against the road surface (prevent wiggling & squirming of the tire face) but are not rigid and therefore do not support weight. So they do not force more tire onto the road than the pressure calls for.

Don't forget there is a dynamic system here with tire pressure, spring rate, & damper (shock absorber) stiffness that gets to how the car responds to the road surface, bounces, water dissipation, and so on. These get to how well the car "sticks to the road," to how well it brakes, and to how it responds in emergency maneuvering.

Don't forget that the recommended tire pressures are stated from calibrated testing. How accurate is your tire pressure gauge? If your tire pressure gauge is showing high pressure and you are getting proper wear, maybe your gauge is reading high?

In the end if the tire wear is acceptable and you want more mileage, go for it, but recognize that, like the balloon it is named after, rubber tires change shape with pressure, these pressure changes affect performance (both good & bad), and affect guarantees by the manufacturer.

This was taught in 8th grade science and it hasn't changed. The most common mechanical pressure transducer is a bourdon tube. It's a curved metal tube with an oval cross section. As pressure goes up it becomes more round and causes the tube to straighten out in a highly predictable way.

Funny, this is the principle involved in how tires operated at pressure reduce the tire footprint against the road...