2007 x5 very harsh ride

[bcredliner]

I would not drop air pressure lower than the minimum inflation specs. That said, you could try measuring air pressure when the tires are hot to see if lower inflation is still within proper range when tires have heated up from normal driving.

[andrewwynn]

Originally Posted by bcredliner

I would not drop air pressure lower than the minimum inflation specs. That said, you could try measuring air pressure when the tires are hot to see if lower inflation is still within proper range when tires have heated up from normal driving.

Unless you are really pushing it you could probably easily use ± 8 psi with no significant problems besides tire wear and mpg.

I would use more psi in the back than the front to counter the heavier axle.


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[bcredliner]

Originally Posted by andrewwynn

Unless you are really pushing it you could probably easily use ± 8 psi with no significant problems besides tire wear and mpg.

I would use more psi in the back than the front to counter the heavier axle.


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Yes, MPG will decrease, wear will increase. Tire temp will also increase and handling will be compromised. When considering handling I think of the compromised capability to handle emergency situations and wet or slippery roads. X5 weighs over 5,000 pounds and has a high center of gravity. I expect that OP is looking for a longterm solution. Regardless, IMO, decreasing tire pressure should not be part of it.

I wouldn't change size of wheels either. I suggest doing some tire research and checking the validity of what you find with a couple of big volume tire sellers where there is lots of history as to what is the tire that provides the most comfortable ride. Here is one source for input: https://www.tiredeets.com/best-tires-for-bmw-x5/

I think the longterm solution will be a combination of tires that are well documented as a soft riding, comfort tire and changing shocks/struts.

[byaru1]

Originally Posted by bcredliner

Yes, MPG will decrease, wear will increase. Tire temp will also increase and handling will be compromised.

I don't notice any compromise in handling at 29psi.

When considering handling I think of the compromised capability to handle emergency situations and wet or slippery roads. X5 weighs over 5,000 pounds and has a high center of gravity. I expect that OP is looking for a longterm solution. Regardless, IMO, decreasing tire pressure should not be part of it.

Why not? It's not a significant decrease and it works. It's 3 years for me at 29psi on the same set of Kumhos.

I wouldn't change size of wheels either.

You are now being too careful and walking in eggshells Analysis paralysis..

Of course the tyre sizes can be played with within reasonable safety considerations.

I think the longterm solution will be a combination of tires that are well documented as a soft riding, comfort tire and changing shocks/struts.

For me, less tyre pressures have worked, and I can say long term.

[bcredliner]

Originally Posted by byaru1

I don't notice any compromise in handling at 29psi.


Why not? It's not a significant decrease and it works. It's 3 years for me at 29psi on the same set of Kumhos.




You are now being too careful and walking in eggshells Analysis paralysis..

Of course the tyre sizes can be played with within reasonable safety considerations.



For me, less tyre pressures have worked, and I can say long term.

One case is anecdotal. Glad you achieved what you wanted but your results cannot be assumed to be universal.

Nevertheless, if tires are under inflated the contact patch becomes smaller negatively impacting handling, traction on wet or slippery roads and braking distance. I see no reason to accept any increased risk when it comes to being as safe as possible when driving especially when there are other options to address the problem that don't increase the risk.

[crystalworks]

Originally Posted by bcredliner

if tires are under inflated the contact patch becomes smaller negatively impacting, traction on wet or slippery roads and braking distance.

While I agree that I'd personally prefer finding a solution other than lowering tire inflation, I always thought contact patch got bigger, not smaller with under inflation. As Andrew's math illustrates. Though sidewall might roll slightly more in HARD cornering I don't think 29psi is going to cause any major problems. I prefer getting max mpg so run slightly over inflated.

[bcredliner]

Originally Posted by crystalworks

While I agree that I'd personally prefer finding a solution other than lowering tire inflation, I always thought contact patch got bigger, not smaller with under inflation. As Andrew's math illustrates. Though sidewall might roll slightly more in HARD cornering I don't think 29psi is going to cause any major problems. I prefer getting max mpg so run slightly over inflated.

Generally, contact patch gets larger as inflation increases. But there is a point of diminishing returns. The converse is true that under inflation typically reduces the contact patch. Usually, within reason, the risks associated with over inflation are less so seeking better mileage by adding a few pounds of air can help MPG and is reasonable. I've tried some over inflation for long trips to see if I can increase mileage. Increases were not significant in my case.

In this case we are discussing contact patch in an emergency situation of braking or cornering. When turning the tires rollover to some extent. The more abrupt the turning the greater the load increase so in an emergency situation of cornering the contact patch reduces accordingly. If under inflated the contact patch will move toward the loaded side of the tire reducing the load on the unloaded side and the contact patch. The construction of the tires vary, so how much inflation it takes to reduce or increase contact patch also varies as does the point the tire breaks loose and how much it reduces stopping distance. Depending on the amount of under or over inflation determines whether adhesion is lost in an emergency situation or just regular driving.

The effectiveness of a given tire is subject to several other important variables. When discussing inflation it is important to differentiate between cold tire inflation and the normal operating temperature. Under inflation generates more heat so the change from cold tire to normal temp is greater. Outside temp is also a factor in how much the inflation changes. Most tire manufactures list 35 pounds as maximum inflation and they warn about the risk of under inflation right on the tire. Generally, too much under inflation is more than 10% of the max or 3.5 pounds.

Comparisons here should be apples to apples. As an example comparing what works for an E46, a 6 to an 8 cylinder X5, or one with sport suspension and one without don't necessarily apply. There is no one size fits all. It should be an apples to apples comparisons.

All I'm saying is there are tradeoffs, including safety, that should be carefully considered when making a decision to be outside of the manufacturers stated inflation parameters.