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Discussion Starter · #1 ·
Details to come, I logged on to that tirepressure.com site and use that Replacement Tire Pressure Calculator to find out what tire pressure I should use and it states:

Front tire should be: 42 psi
Rear tire should be: 38 psi

My front tire is 255/40R20 (101 W XL)
My Rear tire is 295/35R20 (101 W XL)

Original tires where 235/55R 18 (100V) – Recommended at 32 psi

Tell me if anyone fills your tire up with that high of psi?

Here’s the detail of how I got to this dilemma.
I’ve been at 32 psi since 2019, but recently I’ve had to make some unscheduled visits to the tire store and they fill my tires between 38 and 42 psi.

In the mornings after the visits, I would let the air out to 32 psi and thought maybe it should be something different this time and that’s when I researched it a little and found that website with the surprising info.

So, what do think, fill them up to that psi or work with the 32 psi as I’ve been doing?
 

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Hmmm... I'd just play it safe and do 32 (cold)... And yeah alot of those guys at tire stores just blast them full of air...
 

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Details to come, I logged on to that tirepressure.com site and use that Replacement Tire Pressure Calculator to find out what tire pressure I should use and it states:

Front tire should be: 42 psi
Rear tire should be: 38 psi

My front tire is 255/40R20 (101 W XL)
My Rear tire is 295/35R20 (101 W XL)

Original tires where 235/55R 18 (100V) – Recommended at 32 psi

Tell me if anyone fills your tire up with that high of psi?

Here’s the detail of how I got to this dilemma.
I’ve been at 32 psi since 2019, but recently I’ve had to make some unscheduled visits to the tire store and they fill my tires between 38 and 42 psi.

In the mornings after the visits, I would let the air out to 32 psi and thought maybe it should be something different this time and that’s when I researched it a little and found that website with the surprising info.

So, what do think, fill them up to that psi or work with the 32 psi as I’ve been doing?
I find that 32 lbs. gives a nice soft ride that gives some lean on curves going normal speed. I use 34 -35 lbs. and it seems perfect for a little more firm ride and better grip on curves. Check it out.
 

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My car had over 40 front and rear when I took it for it's test drive. My first comment after leaving the dealership was, "Who went crazy with the air hose?". After I left with it, I stopped and took them down to 32, and now I run them at 33 front, 32 rear. I have the 275 Pzero Nero tires.
 

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Details to come, I logged on to that tirepressure.com site and use that Replacement Tire Pressure Calculator to find out what tire pressure I should use and it states:

Front tire should be: 42 psi
Rear tire should be: 38 psi

My front tire is 255/40R20 (101 W XL)
My Rear tire is 295/35R20 (101 W XL)

Original tires where 235/55R 18 (100V) – Recommended at 32 psi

Tell me if anyone fills your tire up with that high of psi?

Here’s the detail of how I got to this dilemma.
I’ve been at 32 psi since 2019, but recently I’ve had to make some unscheduled visits to the tire store and they fill my tires between 38 and 42 psi.

In the mornings after the visits, I would let the air out to 32 psi and thought maybe it should be something different this time and that’s when I researched it a little and found that website with the surprising info.

So, what do think, fill them up to that psi or work with the 32 psi as I’ve been doing?
For factory sanctioned tires the factory has come up with the "best" tire inflation pressure. This is what the tires should be inflated to, but taking into account load -- more or max load could require higher inflation pressures -- and in the case of one car the factory called for more pressure if the car was going to be driven at speeds over 100mph.

AFAIK the tire sizes you are using are not sanctioned by the factory. The tire pressures probably arise from what class/type of vehicle the tires were originally intended for.

For you I guess these tire pressures would be a starting point but you may have to adjust the tire pressures up (or more likely) down as you gain experience with the tires. If tire wear seems to be concentrated in the center of the tire the tire pressure is probably too high. The flip side is if the tire shows wear at the edges of the tread the tires pressure is probably too low.

One technique to determine if the tires are inflated properly is to chalk a front and rear tire and then drive the car normally and note the chalk after. What you want to see is the chalk gone from the entire tread face but no signs of any chalk gone from beyond the tread face.
 

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Your going to have to experiment. What's going to work for you with those none OE sized tires is going to be the ride, performance and longevity that you're looking for. Start with OE 32 psi and then go up or down a couple psi at a time from there based on chalk lines, performance and level of comfort that you are looking for.
 

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I'm curious though... Why those tire sizes... Your probably better off going with a more conventional tire size depending on the width of your rims...
 

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Discussion Starter · #9 ·
I'm curious though... Why those tire sizes... Your probably better off going with a more conventional tire size depending on the width of your rims...
My original rims were 18 x 7.5 Mag OEM rims
Upgraded 2 weeks after I bought my car with:
Front 20 x 9
Rear 20 x 10.5
 

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Discussion Starter · #10 ·
For factory sanctioned tires the factory has come up with the "best" tire inflation pressure. This is what the tires should be inflated to, but taking into account load -- more or max load could require higher inflation pressures -- and in the case of one car the factory called for more pressure if the car was going to be driven at speeds over 100mph.

AFAIK the tire sizes you are using are not sanctioned by the factory. The tire pressures probably arise from what class/type of vehicle the tires were originally intended for.

For you I guess these tire pressures would be a starting point but you may have to adjust the tire pressures up (or more likely) down as you gain experience with the tires. If tire wear seems to be concentrated in the center of the tire the tire pressure is probably too high. The flip side is if the tire shows wear at the edges of the tread the tires pressure is probably too low.

One technique to determine if the tires are inflated properly is to chalk a front and rear tire and then drive the car normally and note the chalk after. What you want to see is the chalk gone from the entire tread face but no signs of any chalk gone from beyond the tread face.
I didn't know about the chalk.
I had to look up an example to see what you meant and saw someone marking the tread that should be in contact with the ground.
It said to go about 100 yards and check where the chalk was removed.
If chalk is removed in the center: deflate a little
If chalk is removed on the edges: inflate a little
If it removes evenly then the pressure is good.

I assume this will also help with knowing if your alignment is off.
 

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My original rims were 18 x 7.5 Mag OEM rims
Upgraded 2 weeks after I bought my car with:
Front 20 x 9
Rear 20 x 10.5
Then you could go with some 275's up front and bigger in the rear for a real nice look...
 

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Discussion Starter · #12 ·
Then you could go with some 275's up front and bigger in the rear for a real nice look...
I considered 275/40R 20, but to match the same tire diameter (28.7) for the rear I would need a 315/35R 20 and those won't fit without some type of cutting somewhere.

My next set will be:
Front: 265/40R 20
Rear: 305/35R 20

Changing the tire diameter from 28 inches to 28.4 inches, which fills in the gaps I have from my fender to the tires.
 

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I considered 275/40R 20, but to match the same tire diameter (28.7) for the rear I would need a 315/35R 20 and those won't fit without some type of cutting somewhere.

My next set will be:
Front: 265/40R 20
Rear: 305/35R 20

Changing the tire diameter from 28 inches to 28.4 inches, which fills in the gaps I have from my fender to the tires.
I think they might... See if others will chime in on that...
 

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I watch my tire pressure all the time. Maybe a little obsessed with that. I try to keep it at 32 cold (when parked), and it also depends a LOT of the time of year where I live. When the weather cools off, the tire pressure doesn't get much above the 32 psi. But in the summer, those tires can get to almost 40 psi if I am not careful.
Just last week I had to make a long trip, and it was very cool in the early morning. I put in an extra 2 psi due to the cooler temps. They are now at about 32/33 cold and 35/36 after driving for a while.
 

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Details to come, I logged on to that tirepressure.com site and use that Replacement Tire Pressure Calculator to find out what tire pressure I should use and it states:

Front tire should be: 42 psi
Rear tire should be: 38 psi

My front tire is 255/40R20 (101 W XL)
My Rear tire is 295/35R20 (101 W XL)

Original tires where 235/55R 18 (100V) – Recommended at 32 psi

Tell me if anyone fills your tire up with that high of psi?

Here’s the detail of how I got to this dilemma.
I’ve been at 32 psi since 2019, but recently I’ve had to make some unscheduled visits to the tire store and they fill my tires between 38 and 42 psi.

In the mornings after the visits, I would let the air out to 32 psi and thought maybe it should be something different this time and that’s when I researched it a little and found that website with the surprising info.

So, what do think, fill them up to that psi or work with the 32 psi as I’ve been doing?

Every Challenger - regardless of model, wheel size, or tire size - calls for 32psi at all four corners. At least that's the only number I've ever seen in a door jamb.

Pretty sure the Dodge engineers have a good handle on what the suspension is expecting and this site verifies that: Dodge Challenger - Tire Pressure.
 

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Hmmm... I'd just play it safe and do 32 (cold)... And yeah alot of those guys at tire stores just blast them full of air...
Ditto!

The pressure clearly stated on your drivers door pillar is 32 psi., the recommended tire pressure works well with the TPMS (Tire Pressure Monitoring System), which can be a nightmare if it becomes a problem, been there!

At 32 psi cold they will normally heat up to 34 psi, maybe on a really hot day to 35 ~ 36 psi., I was running 30 psi for better traction but on colder days that pressure would drop and cause the TPMS to go nuts.

Run the pressure the car label recommends and you'll be just fine.
 
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Every Challenger - regardless of model, wheel size, or tire size - calls for 32psi at all four corners. At least that's the only number I've ever seen in a door jamb.

Pretty sure the Dodge engineers have a good handle on what the suspension is expecting and this site verifies that: Dodge Challenger - Tire Pressure.
Believe that chart on the door jamb is for factory sanctioned (aka original equipment) tire/wheel sets.

If one stays with any of factory wheel/tire combinations then yeah, 32psi and done.

But fit non sanctioned tires or wheels/tires -- anything not listed at the web site you provided -- and while 32psi might be still a good pressure it might not be.

'course, 32psi would be as good a starting point as some other pressure.
 
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