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Old 08-12-2007, 07:36 PM   #1
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overinflation and suspension

Most of the users on this site report that they run overinflated tires, or at least pump their tires up to the sidewall-listed max pressures. I myself am currently doing so, and have had absolutely no problems. I can take turns a bit faster, and my FE has definitely improved.

How though, is this kind practice on your suspension? While trying to convert my dad, he brought up a very valid argument. He said that having the tires too solid could transfer more vibration to the car's suspension, thus wearing out the suspension prematurely. In his case, since he carries very heavy loads (think close to max capacity in his Envoy XL), this problem could be exacerbated.

On a side note, he just purchased a Lexus RX400h for my mom, and it came from the dealer with 45 psi in the tires, EXACTLY what is listed on the sidewall as maximum allowable pressure. I mentioned this to him and he was a bit surprised.

He is letting the RX400h stay as his, but is also not budging on his own Envoy XL. I just want him to save as much fuel as he can, but I am not going to force him into it, and would rather present the issue to him with verifiable data and experience.

Is there anyone on the site that has experience with automobile suspension, and can definitively say whether or not my dad's concern is a valid one?

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Old 08-12-2007, 08:13 PM   #2
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No experience on the suspension, but how often does he check the tires? Maybe the gs members should go around pumping up our friends tires without them knowing to help the unbelievers get better FE.

I can't imagine that the difference of tire pressure is really affecting the suspension much. But then again I don't haul anything in an Envoy.

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Old 08-12-2007, 08:13 PM   #3
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My opinion is that the answer for this is a very touchy one. I'll say that all manufacturers design the suspension to maybe last only twice as long as the bumper2bumper warranty. And that the higher pressures in a vehicle not driven on nice roads will exhibit blatent signs of wear at-that-time.

But. Very Slightly worn suspension does not show driveability symptoms/noises besides lower fuel mileage, and where I am from, the repair shop will align my wore-out vehicle for years and years if-they-think I'm not going to pay them for parts replacement. The alignment is never satisfactory, and the fuel mileage never is what it was, which they find excuses for blah blah blah.

None of this is "definitively" speaking, but I "think" there would be more of a concern for sedans/coupes/hatchbacks over your familys SUV type vehicle.
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Old 08-12-2007, 08:31 PM   #4
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GeekGuyAndy: He checks them at least once a month. We use one of those cheap pencil-type ones though, and I don't trust it very much. We have a nice compressor at our house, and I think it would make sense to just break down and get a nice air chuck WITH a gauge on it. That is how they all are in Japan anyways...

nortonpro: My dad lives and works in Michigan. He covers most of the Detroit, Lansing, Jackson and surrounding areas. He hauls heavy door frames, and as you know, the roads in Michigan are absolute CRAP. So, he does see very unfavorable driving conditions. This is one reason why I am not pushing him too hard. He has also worked on his own cars for many years, something that I can not claim to have done (yet). Oh, and his car is used 100% for work, as in, he doesn't drive it at all for personal use. If he is in it, he is using it to bring home the bacon. Speaking of which, this morning we had some really tasty bacon (the literal, not figurative type mind you!)

If the roads were in good shape around here, it wouldn't be nearly as worrisome to him. It is just that after driving on Michigan roads your whole life, you realize that they aren't exactly built to keep your car in good shape. Maybe it is just a ploy to get people to buy new cars more often...
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Old 08-12-2007, 08:38 PM   #5
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I don't think the suspension will wear prematurely in any significant way, since it'll still get and take all the big bounces, which are what cause most wear. If you can feel an increase in bumpiness w/ pressure, your struts aren't absorbing it. Something I've wondered about is whether bushing wear rates increase significantly, since more smaller stuff getting through, however I don't think these would either, to the point of concern anyway. The most significant increase in risk imo is of a blow out/tire damage from deep pot holes/jagged edges.
Originally Posted by FormulaTwo
I think if i could get that type of FE i would have no problem driving a dildo shaped car.
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Old 08-12-2007, 08:51 PM   #6
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as long as your suspention isn't warn out already I wouldn't worry about it, and if he is hauling heavy cargo then I would recomend that he fallows his owners manuals recomendation, and over inflate his tires.
what is going to cause problems are stiff suspention parts, or woren out supsention parts, as they are going to alow the rest of the vehicle to be affected by the shock of travling down the road.
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Old 08-13-2007, 04:52 AM   #7
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I bought a brand new 1995 Honda Civic VX in November 1995 and inflated every set of the 3 sets of tires (original and two sets of replacement Nokian NRT2) to the maximum sidewall pressure or greater. In the 12 years and 225,000 miles I owned that car, I never replaced a strut, spring or any other suspension or steering component; never had a bent wheel; never blew out a tire; never had uneven tire wear...in fact the tires wore more evenly than any other car I ever owned with normally inflated tires.

The car certainly had a stiff ride and bounced around on more bumpy roads, but it never bothered me. The benefit of substantial fuel savings outweighed the stiff ride.

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Old 08-13-2007, 05:32 AM   #8
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I suspect that higher inflation may make bushings wear a little faster. So I need to figure out if I can change them myself...

On the Lexus, I bet that the 45 psi was something that the factory does, and that the dealer was supposed to lower the tires to the recommended pressure on the doorjambs.
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Old 08-14-2007, 11:32 AM   #9
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Great info everyone.

I kind of figured that the dealer (wanting to boost mileage) pumped up the tires themselves. People are complaining about not getting the mileage that they were promised with hybrids, and this is just one easy way to increase peoples' FE, without them noticing anything different.
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Old 08-14-2007, 11:43 AM   #10
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Fact is most later model cars with lower profile 14,15,16 and 17 inche tires have very little sidewall deflection. Pumping the tires up really doesn't hurt the ride quality over all much at all. Think about. A lot of sidewall deflection on such a low profile tire would be death to rims. Now a taller sidewall or as some liked to call them ballon tires. They do have deflection properties.


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