Struggling - Tire Decision

[Sansred]

I am new and own a 2021 JLU Willys with a 2.5" lift. I had 265/70 r17 and wanted a bigger tire to fill the space and look a little better. Very little off-road, mainly dirt roads, gravel and someday sand/beach. More pavement than anything. Discount Tire talked me into 315/70's (I wanted 295/70 but I like Falken Wildpeak and that size not available), they rubbed, so to fix that I purchased American Outlaw Spike wheels with proper offset, no more rubbing. However, ride got more rough, and I fear I am in a more aggressive size tire than what was planned. I am still in 30-day window so tires can be returned. 315's are a C load range, and all I can find in other slightly smaller tires is E. Feeling overwhelmed on what to do. My goal was to fill some of the empty wheel well space, have it look a little better, but not crush my comfort and mpg's. Open to solid suggestions.

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[yokramer]

What tire pressure are you running? Should be around 30-33ish if you are up near 40 thats going to give you a way harsher ride. Also you shouldnt have been rubbing on the 315s with a 2.5" lift even on stock wheels.

 

[Sansred]

I did have them at 33 but just dropped psi to 30-31. Some improvement. The rubbing was at full articulation on lower control arms.

 

[GATORB8]

I did have them at 33 but just dropped psi to 30-31. Some improvement. The rubbing was at full articulation on lower control arms.

I'd play with a little lower. Looks like they are 113 with a max of 35 psi. They are load rated for almost 20% more at 35 psi (2535 lb/tire) than the factory Rubicon's are at 37 psi (2189 lb/tire), and the factory 37 psi is higher than most run.

 

[Sansred]

Thanks. I am taking it to a jeep shop in my area on Thursday, they think the lift kit installer may not have loosened tension on the control arms which may be creating a little more bounce. I owned a Gladiator prior to the Wrangler, it had a different feel. Figuring it out.

 

[azwjowner]

Take the pressure to 25 and reevaluate. 25 PSI is perfectly safe for such large tires.

 

[Ratbert]

Take the pressure to 25 and reevaluate. 25 PSI is perfectly safe for such large tires.

It might be safe, but you risk wearing out the outer portions of the tire rather quickly. Running too low also negatively impacts handling, braking, and MPGs.

 

[azwjowner]

It might be safe, but you risk wearing out the outer portions of the tire rather quickly. Running too low also negatively impacts handling, braking, and MPGs.

Not really, it'll wear more evenly than overpressurized (wears out the center). Braking is improved. Handling will be less crisp, yes. You can always add more pressure back in if desired.

 

[Ratbert]

Not really, it'll wear more evenly than overpressurized (wears out the center). Braking is improved. Handling will be less crisp, yes. You can always add more pressure back in if desired.

Care to explain how braking is improved by running tire pressure that's too low? That goes against everything I've learned about tires / tire pressure.

 

[azwjowner]

Care to explain how braking is improved by running tire pressure that's too low? That goes against everything I've learned about tires / tire pressure.

Not too low. Correct for the weight. Per the tire manufacturers association, a 35x12.5r17 tire, or its metric equivalent, is rated to carry 1875 pounds at 25 PSI. That’s 7500 pounds per four tires, well in excess of a Jeep’s weight. If someone runs above 25 PSI they are doing it for other reasons. That is an important distinction. If the tire were truly too low, I would agree with you.

Improved braking is from better grip. If you pump up the tire to 40 PSI, you have a smaller contact patch with the ground (it starts riding only on the center of the tire), and although static friction in theory is agnostic to surface area, in reality the more rubber in contract with the ground, the greater the friction.

 

[Ratbert]

Not too low. Correct for the weight. Per the tire manufacturers association, a 35x12.5r17 tire, or its metric equivalent, is rated to carry 1875 pounds at 25 PSI. That’s 7500 pounds per four tires, well in excess of a Jeep’s weight. If someone runs above 25 PSI they are doing it for other reasons. That is an important distinction. If the tire were truly too low, I would agree with you.

Improved braking is from better grip. If you pump up the tire to 40 PSI, you have a smaller contact patch with the ground (it starts riding only on the center of the tire), and although static friction in theory is agnostic to surface area, in reality the more rubber in contract with the ground, the greater the friction.

If you look back at the conversation you'll see that you were talking about braking being improved when running too low:

That's what I was questioning.

 

[azwjowner]

If you look back at the conversation you'll see that you were talking about braking being improved when running too low:

That's what I was questioning.

That's a fair point. I was disagreeing with the notion that 25 PSI is too low, but I didn't explicitly say it, so I can see how you would interpret it as sanctioning running at excessively low pressures. I would strongly disagree that 25 PSI is too low for 35s, so there is no problem at that pressure, but I agree that if someone is running too low for their tire size, it's a problem.

 

[Sansred]

Thanks everyone. I am going to do the chalk test to ensure full contact and proper pressure. I appreciate iate all the education.

 

[Touchingstone]

A word of reason here: For your intended use, your original 265/70r17 seems to be a perfect fit. Why go to 295 or even 315 just for the look? The 315 is a ridiculous overkill, isn't that an MT tire? The penalty (+30lb/tire) far out-weights the benefit (no pun intended). If you want a better ride, I would go the opposite direction and consider swapping back to a set of Falken Rubitrek instead of Wildpeak and never look back.

 

[yokramer]

A word of reason here: For your intended use, your original 265/70r17 seems to be a perfect fit. Why go to 295 or even 315 just for the look? The 315 is a ridiculous overkill, isn't that an MT tire? The penalty (+30lb/tire) far out-weights the benefit (no pun intended). If you want a better ride, I would go the opposite direction and consider swapping back to a set of Falken Rubitrek instead of Wildpeak and never look back.

Tire size does not dictate A/T or M/T, the Wild Peak line has an A/T M/T and R/T.

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