Challenger rear tyres PSI

[Mark_B]

Hi All,

Is anyone running maximum PSI on their car types?  BF Goodrich can go to 35psi but the handbook says the 70 Challenger tyres should be 32psi.

I'm wanting the tyres taller at the back.  Will there be any issues?

Thanks for any help you can give.

[70vert]

I'm not sure over-inflating will make a noticeable difference, and if you do drive it there would be a negative impact on drivability including stopping. If it's just for show then no harm.

BTW: I keep mine slightly under inflated at 26-28 psi, they are lower profile on 17" rims.

[Mark_B]

The rear tyres are 32psi at the moment.  So inflating them to 35psi won't make them slightly taller?

[BIGSHCLUNK]

I've run 35PSI on my BFG's for years..........

[70vert]

they might measure taller I just don't think you could tell visibly with a 3psi increase.
Also, I am not saying it would be a big issue either just not optimal tread contact per the manufacturer's guidance.

[Mr Lee]

I'm not sure over-inflating will make a noticeable difference, and if you do drive it there would be a negative impact on drivability including stopping. If it's just for show then no harm.

BTW: I keep mine slightly under inflated at 26-28 psi, they are lower profile on 17" rims.

Why do you under-inflate them?   The lower the profile, the harder (higher psi) your tire should be.   
Watch out for potholes. 


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[Mr Lee]

BTW: I keep mine slightly under inflated at 26-28 psi, they are lower profile on 17" rims.

Why do you under-inflate them?   For a smoother ride?  That's risky. The lower the profile, the harder (higher psi) your tire should be.   
I would recommend you be extra careful around potholes.

As an example
Skinny road bicycle tires that are as wide as your thumb are supposed to be @ 100psi
Mountain bike tires that are 2.5" wide with a tall sidewall are around 30 psi
Then i have another mountain bike that has 3.8" wide tires and I run about 7 psi on those

I would think that it would be similar for car tires.  Our e bodies came with 5.5" wide rims but most of us are running 7-8" or wider.  It takes less psi to make a large volume tire hard than a low volume one so what should they be filled with?  I'd ask the tire manufacturer.

My VW GTI has low profile tires and the recommended psi is 37!  And the car weighs nothing.


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[Mark_B]

Thanks for your comments.  I think I'll pump them up to 35psi and see if they look taller.  If they don't I'll return them to 32psi.

[MoparLeo]

Tire pressure will be determined by volume. If you filled up a 10 speed tire with water and measured the amount, it would be very small compared to a mountain bike tire.
The lower the volume, the higher the pressure (compressed volume) is required to support the same amount of weight. The larger the tire, the lower the air pressure required to support the load. Since your rear tires are much larger than the originals, the lower the air pressure required to support the load.
The E-body platform is nose heavy. Not a lot of rear axle weight %. A 255/60 size tire only needs about 26PSI in the rear. Too much air and the tire bounces over bumps in the road instead of rolling over them.
Remember that the axle is in the centerline of the tires diameter. !/2 above and 1/2 below. So if you were to increase the diameter by 1" the maximum height change would be 1/2". But this isn't possible since when the tire is in contact with the ground,, the contact area is flat not round.
Anyway if you want more height in the tire, change to a bigger tire. If you want more rake, you may also need to increase the arc of the rear leaf springs.