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-   -   Stock OEM PSI vs Aftermarket PSI (http://www.jeepgarage.org/f109/stock-oem-psi-vs-aftermarket-psi-36527.html)

JJeep12 01-31-2012 09:17 PM

Stock OEM PSI vs Aftermarket PSI
 
Didn't see a question like this and hopefully I looked good enough.

I put 265/50/20 on my WK2 and OEM tires were 265/60/18. I might have read somewhere that the PSI recommended is the PSI on the inside of the door.
Should I be running the PSI recommended from the OEM Tires or my new Tires?
Does anyone know in which direction the speedometer goes with the bigger rims? Meaning, driving on OEM's at 40 mph vs aftermarket at 40 mph. Am I going 43 mph or 37 mph? (speeds are just examples)

nek121328 01-31-2012 09:40 PM

Re: Stock OEM PSI vs Aftermarket PSI
 
Slower............................................ ................................................. as the wheels turn slower............................................ .........................................., but is the outside diameter larger vs the 18" tires?

Kland 01-31-2012 10:47 PM

Re: Stock OEM PSI vs Aftermarket PSI
 
JJeep12 any pictures of the 265/50/20 tires?

cbowen 01-31-2012 11:52 PM

Re: Stock OEM PSI vs Aftermarket PSI
 
I always run my tires 5-10 psi under what the max pressure is. It should say on the side of the tire somewhere. I do this because I usually notice cupping on the outside of my tires when running at recommended pressure.

The rims have nothing to do with the speedometer being off. It is based on the diameter of the tire. Your speedometer should be almost the same because your tires have nearly the same diameter. Your stock tire 265/60/18 has a diameter of 30.51 inches and your new tire size 265/50/20 has a diameter of 30.43. That is a difference of 0.27% which is not enough to effect your speedometer. If your speedometer says you are doing 60 mph you are actually doing 60.1 mph which means your speedometer is going to be 0.264% too fast which is obviously not enough difference to notice. Yes your new wheels are bigger but your new tires are actually smaller by a small fraction. So in your case your speedometer is going to be faster.

JJeep12 02-01-2012 05:35 AM

Re: Stock OEM PSI vs Aftermarket PSI
 
1 Attachment(s)
Quote:

Originally Posted by Kland (Post 564780)
JJeep12 any pictures of the 265/50/20 tires?

OEM's 18x8.0
2Crave#4 20x9.5

Cbowen - Thanks for the info. Now I know how fast I'm going when I'm speeding down the 10.


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