Tire air pressure opinion

[ParknVibe]

An idea I have concerning the tire pressure and the tire stands, ride comfort, vehicle weight on each tire, and tire sag from the load bearing on it.First, let me say that I have the 2009 2.4L with auto trans., 17" alum. wheels with P215/45R17 RSA Goodyear tires. The required tire pressure is 32 psi for ALL tires. ((if you have an AWD model the requirement is 35 psi for the front and 32 psi for the rear tires.))Second, we all know that the front end is ususally heavier then the rear end because of the weight of the engine and trans. With my tires set at 32 psi for all four, I felt that the ride comfort is very stiff and BONE cracking especially when riding over railroad tracks. With equal tire pressure on all fours, I can clearly see that front tires sag more then the rear tires do to the different vehicle weight bearing on each tire. I then measured the height of my tires from the ground to the edge of the wheel. The rear measured more then 2.5 inches and the front tire was measured at 2.25" or less. My opinion or my idea now is to have all four tires to have nearly equal height dimension from the ground to the edge of the wheel rim. In order to do this, I must increase the front tire's pressure and lower the rear tire's pressure or start with 32 psi in the rear as a basis. Today I tried this by increasing the fronts to 37 psi and the rear tires were at 33 psi already with near cold tire temperature. With this setting, the tires side wall height did not change much, but the ride over the railroad track felt much less bone cracking. I feel now, that in order to minimize the harsh ride from road bumps (shaped like a parking lot speed bump), road cracks, and very course road surfaces, the front and rear tires should be at different tire pressures. Also, there may be fuel efficiency bonus as well. I welcome any comments and opinions of this idea.Thank you. I'm tired, I'm going to bed... good night

[star_deceiver]

I'm for the stiffer ride! Mine were always well above 40psi. At the end of their 37000km life they were worn evenly!

[dayday]

I've got the same wheel/tire combo. I've certainly noticed the fronts looking low due to weight but also think it's a bit exaggerated due to the very low profile of the tire. For me, I use 32psi at all four corners and it feels fine "to me". Experiment with psi to your liking, just keep an eye on uneven wear.

[ParknVibe]

Quote, originally posted by star_deceiver »I'm for the stiffer ride! Mine were always well above 40psi. At the end of their 37000km life they were worn evenly!When I got the car new, I never checked the tire pressure for almost two months. When I did, they were all exactly 40psi (cold before driven). This was in the summer. At the time I was concern about how they looked so inflated. I just let it go assuming the dealer adjusted the pressure before handing the car to me. I learned from this forum that the manufacturer overinflates the tires for transporting. Anyway, at that time, I felt that the ride quality or comfort was not bad for a small car. However, when I found in the service manual that for an AWD model, it required a higher tire pressure (35 psi) in the front then the rear (32 psi)... got me thinking to hard about this!

[ParknVibe]

Quote, originally posted by dayday »I've got the same wheel/tire combo. I've certainly noticed the fronts looking low due to weight but also think it's a bit exaggerated due to the very low profile of the tire. For me, I use 32psi at all four corners and it feels fine "to me". Experiment with psi to your liking, just keep an eye on uneven wear.I'm trying to fine tune the ride comfort and at the same time provide better fuel milage. After keeping all tires at 32 or 34 psi for the past three years, the ride was always like the car was about to come apart from within. It is extremely rough riding over a course pavement.When the front tires first contacts a rough crack or a sharp bump, the shaking of the car ( and steering wheel) is then multiplied by the rear wheels. I believe the extra weight on the front tires, the tire sag or side wall bulge, and the car's short wheel base combine to a bone cracking ride where I live. And not to mention the built-in stiff suspension to begin with.

[Water boy]

If you are gonna adjust the PSI to get the same rim height don't forget to adjust while you are in the pilot seat.If you do the suggested tire rotation the wear should balance out.

[ParknVibe]

Quote, originally posted by Water boy »If you are gonna adjust the PSI to get the same rim height don't forget to adjust while you are in the pilot seat.If you do the suggested tire rotation the wear should balance out.I have very low mileage on the three year old car....only 6300 miles. I just had the tires rotated for free by the dealer. It is best to adjust the tire pressure when they are cold with no one in the car. I just found that with the front tires at 37psi and the rear tires at 32-33 psi, the ride over a certain railroad crossing is now much smoother and less harsh then when the front tires were at 32 psi.I now believe that in order to get both the front and rear side walls to have equal heights, the fronts would have to be increase perhaps more then 40 psi. however, I may try to see how much pressure it will require. I would ideally have equal heights in all tire. That way, all tires would have an equally size tire footprint.

[Kincaid]

Interesting and timely topic. Thanks for doing the research!Driver sensitivity to the road surface really seems to vary, or perhaps the roads are rougher there. I've had the car for just two years now (same specs as you) and always had the tires set at 32 psi. I would never have called the ride harsh or bone jarring. (In fact I recently got to drive my Civic w/the Eibach Pro-Kit springs and Tokico Illumina shocks and realized that road a lot stiffer than the Vibe).I am not very concerned about uneven wear (on those crappy RS/A's) and just wanted to maximize mpg.I have had several tankfuls now since starting to employ coasting as a hypermiling technique, and the mpg had improved about 1 mpg over the tankful.So, on Wednesday after I changed my oil and and had a fill up, I increased the pressure to 43 psi in the fronts and (after reading your theory here) I increased the rears to 40 psi.I expected higher pressure to equal harsher ride, but kind of like you it seems just fine. Maybe increased pressure = increased sidewall hight = softer ride. Counterintuitive to me but I ran over a familiar pot hole on the way to work and it seemed less harsh.Can't wait to check my next mpg numbers.

[ParknVibe]

Quote, originally posted by Kincaid »Interesting and timely topic. Thanks for doing the research!Driver sensitivity to the road surface really seems to vary, or perhaps the roads are rougher there. Almost every local street, county roads, and state highways in New Jersey are very, VERY bad. All due to winter's freezing and thawing as well as hot summer heat that will buckle the pavement into "speed bumps" Quote, originally posted by Kincaid »I've had the car for just two years now (same specs as you) and always had the tires set at 32 psi. I would never have called the ride harsh or bone jarring. (In fact I recently got to drive my Civic w/the Eibach Pro-Kit springs and Tokico Illumina shocks and realized that road a lot stiffer than the Vibe).I am not very concerned about uneven wear (on those crappy RS/A's) and just wanted to maximize mpg.I have had several tankfuls now since starting to employ coasting as a hypermiling technique, and the mpg had improved about 1 mpg over the tankful.So, on Wednesday after I changed my oil and and had a fill up, I increased the pressure to 43 psi in the fronts and (after reading your theory here) I increased the rears to 40 psi.I wouldn't go higher then 38 psi (cold) Quote, originally posted by Kincaid »I expected higher pressure to equal harsher ride, but kind of like you it seems just fine. Maybe increased pressure = increased sidewall hight = softer ride. Counterintuitive to me but I ran over a familiar pot hole on the way to work and it seemed less harsh.With the low profile tires (with narrow sidewall height) (in my opinion) .... AND with low tire air pressure in them.... the side walls will flex more and as a result, hit the wheel rim hard when the tire hits a sharp pothole during a fast run over it. This could result in damage to the aluminum wheel. or a flat tire. With more pressure in the tire, the tire should "bounce" over... rather then "crush" into the pot hole. With a high profile tire there is always more "air space" between the road and the rim. Quote, originally posted by Kincaid »Can't wait to check my next mpg numbers.Please let me know. My was never good because I do mostly short trips.

[ParknVibe]

I'll just reply to myself and say that I feel that my 2009 2.4L auto Vibe rides better with the tire pressures at 35 psi front and 32 psi in the rear.

[Old Tele man]

...door sticker says 32 psi for the Goodyear RS-A's, but I've always been using 40 psi for better milage.

[ParknVibe]

I ran my new Vibe at 40 psi for a few months without being aware it was that high. However the tires looked fully inflated. I may try to drive them at that pressure again soon. With today's temperature of 104 degrees, the tire pressure could be close to it.

[Kincaid]

I recently posted a personal best 27.9 mpg.

[Kincaid]

and now running speeds of 60-85 mph thru the mountains of Montana and Utah I got 32.2 mpg.

[cptnsolo77]

I run 37PSI. I seem to get slightly better mileage & the car doesnt feel as mushy as it does at 32 PSI. No uneven wear problems.

[zorenB]

The amount of pressure in your tire should not exceed the tire's capacity. If the pressure exceeded the "supposed to be pressure" expect your tire will burst after awhile. Tires are essential parts of a car. Innovations for tires are widespread and just recently, a self-inflating tire is introduce to the public. According to a Monday press release, Goodyear is creating a new tire that will not only monitor its own pressure, however will re-inflate the tires as needed for maximum safety and performance.The business has not mentioned a time frame when the technology will be available to consumers.The business has dubbed the new system Air Maintenance Technology, or AMT. Article source: Goodyear develops a tire that inflates itself.

[star_deceiver]

Well, some people are too lazy to take the two minutes and check all 4 tires. IMO - One more thing to jack up the price and get people just a little more ignorant on how their car works so more can be charged in fixing it!

[vibenvy]

Quote, originally posted by star_deceiver »Well, some people are too lazy to take the two minutes and check all 4 tires. IMO - One more thing to jack up the price and get people just a little more ignorant on how their car works so more can be charged in fixing it!x2And I thought tire pressure monitor sensors were bad !