Did I make a mistake ( Goodyear Assurance P245 / 65R17 )?

zach04trailblazer

Registered Member
Original poster
Jan 21, 2018
38
Florida
At the beginning of this week I changed out all 4 tires from Blizzaks to Goodyear Assurance P245 / 65R17. The local mom and pop shop here had a deal on them so I made a snap decision to get them. I needed tires ASAP due to the fronts having lost most of their trend and cracks on the sidewalls. Manufacturer recommended size is P245/70R16. Is this okay that they are 5% lower in aspect ratio? The front 2 tires seem to "sag" or bulge out near the bottom. My previous tires did the same and being a dumbass I never thought to lookup the exact specs from the manufacturer before buying. Should I try and exchange them? What do you guys think?
 

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Jul 6, 2014
9,129
245 70r16 and 245 65r17 are about the same diameter. You're fine.
 
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Sparky

Moderator
Dec 4, 2011
12,797
What air pressure you running in them?

P metric tires usually will have a little bit of smush at the contact area.
 

Reprise

Lifetime VIP Donor
Jul 22, 2015
2,450
Yep - the front end is heavier, and puts more weight on the tires - they'll look 'underinflated', compared to the rears. A good tire pressure gauge provides a lot of peace of mind :smile:

Tire construction also comes into play - some tires have stiffer sidewalls and won't 'bulge' as much, given the same amount of air.
The GYs you got are probably on the softer side, compared to an A/T tire, for example.

Some tire techs will say that tires handle their best when they have +5 / +6 psi above mfg spec. I tend to agree with that. (it also slightly decreases rolling resistance, if you're into that sort of thing). That will make the tires look less like they're low on the front - but if you do this, put the same amount of additional PSI in all four - not just the fronts.

Don't forget that pressure will decrease 1psi for every 10F drop in temperature, too.
Supposedly, pressure will increase by the same amount with a 10F rise, but I've never been able to confirm it.
 
Last edited:

Sparky

Moderator
Dec 4, 2011
12,797
35 is standard so it should be OK. Fine to experiment a bit. Don't run max sidewall as you'll ruin your ride plus could cause excess wear in the center of the tread from ballooning.
 

HARDTRAILZ

Moderator
Nov 18, 2011
49,658
Run a simple chalk test and check the wear pattern. You will find the proper PSI better than just guessing or throwing random air in them
 

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