Tire Pressure on aftermarket Rims and tires.

[jaffaz32]

I've always wondered this.

What tire pressures do i put in aftermarket tires? I've gone up a size all round and the new tires are completely different widths.

Do i still go by what's stamped in my door or does it change?

 

[docjohn]

tire pressures depend on the weight of the vehicle and aspect ratio.In general what you have done is gone to a plus one size increase,which should not change the optimal pressure settings.Use what acura recomends,but know that for those of us who take an interrest in performance and who track the car ,handling can be micro adjusted using tire pressures.Plus if you are going to track or do some extended canyon carving then the optimal hot pressure is what you are trying to dial in,thus your starting cold pressure will be lower.what tire model and size do you have?

 

[nsxtasy]

What tire pressures do i put in aftermarket tires? I've gone up a size all round and the new tires are completely different widths.

Do i still go by what's stamped in my door or does it change?

For street tires, go by the recommendation of the car manufacturer, which you should find in the door jamb as well as the owner's manual. (In the NSX, this is 33F/40R.) This is a guideline; if you find you need to adjust upward or downward for comfort, handling, etc, feel free to do so (generally in 2 psi increments). Pressure should be measured cold, i.e. with the car having sat for at least several hours, out of the sun, in about the same temperature as the ambient temperature when you will be driving.

As docjohn notes, most track tires have manufacturer recommendations for an optimal pressure when measured hot, i.e. measured at the end of a track session.

 

[jaffaz32]

For street tires, go by the recommendation of the car manufacturer, which you should find in the door jamb as well as the owner's manual. (In the NSX, this is 33F/40R.) This is a guideline; if you find you need to adjust upward or downward for comfort, handling, etc, feel free to do so (generally in 2 psi increments). Pressure should be measured cold, i.e. with the car having sat for at least several hours, out of the sun, in about the same temperature as the ambient temperature when you will be driving.

As docjohn notes, most track tires have manufacturer recommendations for an optimal pressure when measured hot, i.e. measured at the end of a track session.

Do i go by the recommendation in the door even if the wheels are 1" bigger all round and both the front and rears are much wider than factory.

How does pressure work?

I think i know, i assume it works like.

Regardless of the size of the tire ie a 185/40/15 or a 305/35/18 (made them figures up) with say 40 psi the tires will be just as firm? for example the the first tire will not be harder than the second tire not almost flat because it's a much bigger area to fill. 40psi is not the amount of air but the actual pressure both the tires will be at 40psi (pressure) although the second tire will have allot more air inside it.

Is my understanding correct?

Also how do the door recommendations hold up for track? I guess they are the best all round for comfort and handling on the street. but what if i wanted a more handling focused setup while not being to uncomfortable. would i stick to the same as the door suggests or would the settings be different if so what would you suggest?

They currently have normal air but going to the tire shop to get the air drained and re-filled with nitrogen. so the pressure does not change as much from cold to hot.

 

[nsxtasy]

Do i go by the recommendation in the door even if the wheels are 1" bigger all round and both the front and rears are much wider than factory.

Yes, the recommended pressures are a good place to start even for tires that are not stock sized. (Didn't you read my previous reply, when you asked the exact same question?)

Regardless of the size of the tire ie a 185/40/15 or a 305/35/18 (made them figures up) with say 40 psi the tires will be just as firm? for example the the first tire will not be harder than the second tire not almost flat because it's a much bigger area to fill. 40psi is not the amount of air but the actual pressure both the tires will be at 40psi (pressure) although the second tire will have allot more air inside it.

Pressure matters; the amount of air inside the tire does not.

how do the door recommendations hold up for track? I guess they are the best all round for comfort and handling on the street. but what if i wanted a more handling focused setup while not being to uncomfortable. would i stick to the same as the door suggests or would the settings be different if so what would you suggest?

The pressure recommendations for the NSX (33F/40R, measured cold) are fairly aggressive, and focused somewhat more towards handling than comfort. If you're taking street tires on the track, I would use them as a good starting point. When I was using the stock tires, I was using those stock pressures and they worked fine. And again, those are guidelines; it's easy enough to add or remove air to try other pressures to see what you like the best. Also, as previously noted, most manufacturers of track tires specify an optimal pressure, usually measured hot, for maximum performance.

They currently have normal air but going to the tire shop to get the air drained and re-filled with nitrogen. so the pressure does not change as much from cold to hot.

That won't make any difference to pressure changes between cold and hot. If you remember your high school physics class, PV=nRT, so the pressure changes with temperature the same regardless of whether your tires are filled with air, or nitrogen, or helium, or any other gas.

There's no significant benefit to using nitrogen in tires, assuming you check your tire pressures every once in a while. Read this:

Facts and Myths About Nitrogen Inflated Tires

 

[jaffaz32]

Yes, the recommended pressures are a good place to start even for tires that are not stock sized. (Didn't you read my previous reply, when you asked the exact same question?)


Pressure matters; the amount of air inside the tire does not.


The pressure recommendations for the NSX (33F/40R, measured cold) are fairly aggressive, and focused somewhat more towards handling than comfort. If you're taking street tires on the track, I would use them as a good starting point. When I was using the stock tires, I was using those stock pressures and they worked fine. And again, those are guidelines; it's easy enough to add or remove air to try other pressures to see what you like the best. Also, as previously noted, most manufacturers of track tires specify an optimal pressure, usually measured hot, for maximum performance.


That won't make any difference to pressure changes between cold and hot. If you remember your high school physics class, PV=nRT, so the pressure changes with temperature the same regardless of whether your tires are filled with air, or nitrogen, or helium, or any other gas.

There's no significant benefit to using nitrogen in tires, assuming you check your tire pressures every once in a while. Read this:

Facts and Myths About Nitrogen Inflated Tires

Brilliant thanks, just wanted to make sure i understood everything correctly.

I think the guy installing my tires over inflated and put the same in front and back. I might invest in a digital tire pressure gauge (any recommendations?)

I will check my pressures and adjust accordingly to above, i have a funny feeling he put 40 in all round.

 

[nsxtasy]

I think the guy installing my tires over inflated and put the same in front and back. I might invest in a digital tire pressure gauge (any recommendations?)

I will check my pressures and adjust accordingly to above, i have a funny feeling he put 40 in all round.

It's easy to lower pressure, since you don't need an air pump, just a tire pressure gauge and you can let the air out and measure it, finishing when it reaches your desired pressure.

As for gauges, I've used a lot of different kinds - the old pencil kind, the electronic digital kind, and the dial type. All work well and you don't need to spend a lot of money for one that's accurate. My favorite is this $12 dial gauge, which you can also get for $18 with a connector hose. In fact, I like it so much, we had a bunch made up with the NSX Club of America logo as a giveaway at NSXPO one year. I'm sure you can find similar (and, hopefully, similarly inexpensive) dial gauges in your local auto parts store.