Dodge Challenger Forum banner

1 - 14 of 14 Posts

·
Registered
Joined
·
50 Posts
Discussion Starter #1 (Edited)
For those of you who switched from 245 to 275 tires – have you keep the same tire pressure as before?
Will the new tire size require a higher PSI?
 

·
Registered
Joined
·
4,292 Posts
Run the same based on my experience. 32 cold is a little low anyway, I'd shoot for 35.
 

·
Registered
Joined
·
524 Posts
At the same pressure as the 245, the 275 carries more weight, therefore, to keep the tread flat, a lower pressure is required. Otherwise you will wear out the center of the tread prematurely.
I run 28 PSI in the 275s on the rear.
 

·
Registered
Joined
·
50 Posts
Discussion Starter #4
Hmm.. this is interesting.
The sticker on the Hellcat, which comes with 275's stock, also recommends 32 PSI all around. I wonder why I have to go different on mine..
 

·
Registered
Joined
·
14,291 Posts
Hmm.. this is interesting.
The sticker on the Hellcat, which comes with 275's stock, also recommends 32 PSI all around. I wonder why I have to go different on mine..
The 32 psi recommended pressure is to carry the car's maximum GVWR which on Hellcat is 5,450 lbs. That's a lot of weight so you need more pressure to carry the load. If you mostly run around by yourself or with one passenger then less than 32 psi is acceptable, I've run as low as 28 psi trying to get a smoother ride so feel free to experiment. I'm running about 35 lbs in my 275s now and like the way they feel and the ride is still good although wear may be affected.


Sent from my SM-N920T using Tapatalk
 

·
Registered
2013 Challenger SXT
Joined
·
1,221 Posts
18 psi cold here on a 4200 lbs car, gives the biggest foot print, Had like 38psi (all cold psi) in the tire (9" rim) that contact patch was smaller than the 245 tire I had on! Lowering it to 28" gave me almost an extra inch in contact width and now I was starting to actually get wider than the 245 tire I replaced, lower it again to 24psi got a little more, went down to 20 psi and got full width of the 275 tire, I just put in 18psi over the weekend for track duty and stuck the launch with everything the car had to a tune of 1.78 60ft.

So each car will be different dependent on the weight and rim width, once you get your tire, one thing you can do is work on the air pressure in a driveway with a spray bottle of water or even a garden hose. run the tire thru some water and look at the contact patch and lower the tire pressure til your happy. once you achieve your contact patch you like, that's the psi. Just remember your tire pressure will go up once heated about 2-3 psi or so.
 

·
Registered
Joined
·
116 Posts
Just looked up GVWR,
Hellcat 4300
R/T 4100

So the hellcat has about 50 lbs more weight on each tire but its offset by having a bigger footprint/contact patch than a 245.

Sounds about right to run the same or near same PSI. Wider tire will also bulge out more in the center if over-inflated.

Jeep and other 4x4 types would do the chalk test. Big off road tires are usually load range D/9 ply vice load range C/6 ply of most factory pu tires.

If you put max rated PSI in a load D 33" tire and its on a 4000 lbs jeep not an 8000 lb PU, you will be bounced off the road.

Get a fat piece of chalk and run a line across the tire thread. drive in a straight line as much as possible for a bit and get out and see if its worn off evenly or more in the middle or sides. It will give you an indication if the tire is over or under inflated.
 

·
Registered
Joined
·
14,291 Posts
Just looked up GVWR,
Hellcat 4300
R/T 4100
Those are more like curb weights, but on the light side.

GVWR (maximum weight of car, occupants and cargo)

4,950 lbs SXT
5,300 lbs 5.7L/6.4L
5,350 lbs GT
5,450 lbs Hellcat





Sent from my SM-N920T using Tapatalk
 

·
Super Moderator
Joined
·
13,870 Posts
18 psi cold here on a 4200 lbs car, gives the biggest foot print, Had like 38psi (all cold psi) in the tire (9" rim) that contact patch was smaller than the 245 tire I had on! Lowering it to 28" gave me almost an extra inch in contact width and now I was starting to actually get wider than the 245 tire I replaced, lower it again to 24psi got a little more, went down to 20 psi and got full width of the 275 tire, I just put in 18psi over the weekend for track duty and stuck the launch with everything the car had to a tune of 1.78 60ft.
Drivers should be cautioned that although 18-20 psi may be okay for the track, for maximum traction, it is way too low for the street. Underinflated tires, run with pressure that is below the specified setting, will wear faster on the shoulder due to the additional load being placed on the shoulders of the tires. Also, underinflated tires, by only 6 psi, can build up internal heat that increase rolling resistance and can cause a reduction in fuel economy of up to 5%. As tires lose air pressure, you will experience a significant loss of steering precision and cornering stability.
 

·
Registered
2013 Challenger SXT
Joined
·
1,221 Posts
Drivers should be cautioned that although 18-20 psi may be okay for the track, for maximum traction, it is way too low for the street. Underinflated tires, run with pressure that is below the specified setting, will wear faster on the shoulder due to the additional load being placed on the shoulders of the tires. Also, underinflated tires, by only 6 psi, can build up internal heat that increase rolling resistance and can cause a reduction in fuel economy of up to 5%. As tires lose air pressure, you will experience a significant loss of steering precision and cornering stability.
One who has spent to much time reading than experiencing^. all hog wash for the most part.

So your saying over inflate your tires for more mpg, the suggested sidewall psi is max setting, it does not say normal air pressure setting for your car, this is where you should run it psi. It is a MAX, so anything from 0 psi to max is what your looking for.

So if you set it at max, yes you will get great gas mileage but also will wear out the center of the tire duh!

Max psi is not a normal setting, you must find YOUR psi for YOUR car and combination, once that is found that is the PROPER air pressure. And if you inflate it more than that for gas mileage than you will wear the middle of the tire out. GET IT?

At 20 psi on my tires I get full width of the tire with excellent wear pattern, center is not cupping, using temp gun, surface temp is even across tire. This is the psi for my car.

If I air up my tire to 28 psi it looses almost 1" of contact on the edge, who in there right mind thinks that's ok.

Besides a rear tire like what I got is not ment for cornering, if your carving corners then you need to buy the right tire for that and put in the proper pressure for your car.

The sidewall says max psi that does not mean normal psi for any car.

Just because I have 100 psi max pressure tires on my truck does not mean I run that at max psi specially unloaded, running 38 psi is just fine. So Mr Expert you going to tell me I'm loosing mpg, that I'm creating a lot of heat and so forth and I'm just ruining my tires? If I load it down I will bring up the tire pressure- notice I'm changing the loading rate on the tire, so I need to adjust.

Same as a car tire, if I was to load my car with family and luggage I would have to inflate my tires and not run at 20psi, I'm changing the load on them. So I may bring them up to 28 psi and yet maintain the same contact patch.
 

·
Super Moderator
Joined
·
13,870 Posts
One who has spent to much time reading than experiencing^. all hog wash for the most part.
So your saying over inflate your tires for more mpg, the suggested sidewall psi is max setting, it does not say normal air pressure setting for your car, this is where you should run it psi. It is a MAX, so anything from 0 psi to max is what your looking for. So if you set it at max, yes you will get great gas mileage but also will wear out the center of the tire duh!
Where did I say to use the maximum air pressure setting? All I said is that under inflating a tire will cause wear and handling problems. If 20 psi works for you on the street, that's great. I just won't use a pressure that low in my car.
 

·
Registered
Joined
·
9,456 Posts
Where did I say to use the maximum air pressure setting? All I said is that under inflating a tire will cause wear and handling problems. If 20 psi works for you on the street, that's great. I just won't use a pressure that low in my car.


Nobody in their right mind would drive around at 20 psi on the street. Well, maybe I shouldn’t say nobody:)
 

·
Registered
2013 Challenger SXT
Joined
·
1,221 Posts
Where did I say to use the maximum air pressure setting? All I said is that under inflating a tire will cause wear and handling problems. If 20 psi works for you on the street, that's great. I just won't use a pressure that low in my car.
"Underinflated tires, run with pressure that is below the specified setting, will wear faster on the shoulder due to the additional load being placed on the shoulders of the tires. Also, underinflated tires, by only 6 psi, can build up internal heat that increase rolling resistance and can cause a reduction in fuel economy of up to 5%".

"run with pressure that is below the specified setting"

How in the hell do you know what the specified setting is? As long as your running stock wheels and tires and stock weight with the factory "specified setting" on the door you're fine. They have done the leg work, but you change any of those things, even brand of tire, there is no longer a specified setting. You have to figure out what your new tire pressure is.

So knowing the tire was changed, how in the heck do you know what specified setting is? Only thing left is to assume you was leaning towards the pressure on the sidewall which a large % of people assume that's what they must run their tire at.

Once you change anything from the factory it's on you, the owner, to figure out new pressures and come up with a new number. Many of you run to much pressure and wear the middle of the tires out. That's a given.

I did my homework, even tread wear, even tire temp across tread, light weight rear end car with rims just a little to narrow for a 275 tire. Who the hell are you to say it's not the proper psi for my combination? I drive around just fine. Would it do for a canyon carver, no. It would roll the sides, it would be the wrong tire for what was trying to be accomplished. So knowing that putting 28 psi in the tire combination causing the tire to have about 1" less tread contacting the ground, you ALL would be ok with that, just because you want to feel better about the psi number.

I'm going off what the combination is telling me, my 245 tires I had gave best traction at 28psi- largest foot print all across the tire, I got 100% of my tread to put down. I'm sure none of you would give me crap about that.

This is a fine example where you cannot rely on anyone's number, or what you feel is right. You have to find your own and that's the whole point.
 
1 - 14 of 14 Posts
Top