BFG AT/KO PSI Question after Daystar Lift

[NIKBPIK]

Please don't shoot me for asking, but just looking for I pretty specific answer that I didn't see anywhere else.

Can I run somewhere between 33-35 PSI without risking more than increased MPG? Just don't want it to become a safety issue or cause irregular wear on the tires.

I finally pulled the trigger on the Daystar 2.5/1.5 lift and swapped out my OE 265/65R17 Dunlops for 265/70R17 BFG AT/KOs (6 ply/C Rated). This worked best for me considering I wanted to keep the XREAS on my 09 Sport.

Overall I'm very happy with what I ended up with and the 4R looks great. The only thing I haven't been thrilled about is the rougher ride while running the BFGs at a higher PSI (experimenting between 36 and 38).

I've read most of the threads on the need to increase the PSI with the C rated tires to carry the same load as the stock P tires (37-38 seemed to be the consensus for day-to-day), but today I ran 34 PSI and was much happier with how it rode. In fact I could hardly tell any difference from prior to the lift and tire change.

:thanks:

 

[teampwr2]

You are right on target.

 

[03_4x4Runner]

I have been running the daystar lift and BFG all terrain 265/70/17 load range c for 5 years now. I run 36-37 psi and the tires are wearing fine after 30k miles on them so far. When I run a lower pressure I notice the 4runner does not coast down hills as good as the stock tire indicating more rolling resistance. At 36-37 psi it rolls about the same as stock down the same hill. I lost 1.5 - 2 mpg after the lift and tires though regardless.

 

[kosan]

Can you post some pictures of your setup?

 

[Sungod]

There is a lot of bad information on the internet regarding tire pressure and tires. The load range has nothing to do with tire pressure you should use. Going from B to E does not mean you have to add more air. Adding air increases carrying capacity and higher load range tires have the ability to contain more air. That does not mean that because you are running them that you have to pump them up. I would suggest keeping them at an air pressure that you are comfortable with that is not below the vehicle specs and not above the capacity of the tire. Yes more pressure will make them last longer, but not significantly. You can sacrifice a little longevity for comfort.

 

[03_4x4Runner]

You can see videos in the photobucket in this post. http://www.toyota-4runner.org/4th-gen-t4rs/83068-trac-concerns-1st-attempt-video.html I do not know how to post pictures. My wife does this stuff for me only as needed.

 

[NIKBPIK]

Thanks 4x4runner and sungod. Both make sense. I definitely noticed a difference in roll resistance between 33 PSI and when I was running 37, but just felt like the ride was much less bumpy at 33.

I drive about an hour into work every day and was running just in-between 34 and 35 PSI when I checked them before taking off this morning. I just got home and they're all sitting at 38 after mostly 55 MPH driving at about 81 degrees outside.

I will try and post some pictures of the setup today.

 

[JB.]

Can I run somewhere between 33-35 PSI without risking more than increased MPG? Just don't want it to become a safety issue or cause irregular wear on the tires.

I've read most of the threads on the need to increase the PSI with the C rated tires to carry the same load as the stock P tires (37-38 seemed to be the consensus for day-to-day), but today I ran 34 PSI and was much happier with how it rode. In fact I could hardly tell any difference from prior to the lift and tire change.

The ideal pressure would be one that continuously adjusted for conditions. The technology <a href="http://www.autoblog.com/2012/09/22/goodyear-unveils-self-inflating-tires-for-big-trucks/" target="_blank">exists</a> in truck tires. Maybe it'll make its way into consumer tires in a few years.

Tire pressure recommendations are meant to cover a wide range of operating conditions with a generous margin of safety. You can diverge quite a ways from the "proper" psi in a direction of increased statistical risk without entering in to a range that could be called unsafe. In other words, 34 psi is fine for typical driving.

On the other hand, if you frequently push, say, 160kph on the autobahn, more pressure would be advisable.

As for wear, based on my experience with that tire (V8), I'd expect a little accelerated shoulder wear at 34psi compared to a few psi higher, but driving conditions can affect that a lot so YMMV. You'll just have to watch and decide what's most important to you, but more psi, in the range we're talking about, should give a little better wear.

 

[NIKBPIK]

Moved them up to 38 for the first time yesterday and they actually feel better/less bouncy then when they were at 36. So far I've found....

34 PSI --- very close to stock feel as far as bounce, but significant roll resistance
35-36 PSI --- less roll resistance but too bouncy and degraded stability on turns
37-38 PSI --- ride is stiffer, but with less bounce, less roll resistance

By no means a technical/terminology expert as you can tell. Just my personal observations thus far. May air up to 40 PSI today and then do the chalk test to see how the tire sits as far as future potential wear.