Tire pressure for 205/40/17

[Sivik]

Hey guys,

Just got a new set of wheels, 17" ones. I was wondering what is the correct tire pressure for a 205/40/17 wheel for daily street driving. They came to me approx 40 psi, but I think that is too much. Thanks guys!

[Maxvla]

i'd say about 35 psi... but its really dependant on the tire itself.

and i hope you got your speedo adjusted. or you may see some flashing lights in your rearview mirror before you know it.

[Sivik]

they are Kuhmo (or however you spell it) Ecstasa or something like that... why do I need to adjust my speedo... wouldn't bigger tires slow my car down? and plus, they are just about the same diameter as my stockers due to the low profile tires...

[Accord Man]

they came at 40 for a reason..

when you maintain a higher pressure you have better protection against potholes and such..


I know comfort wise it doesnt feel too good but you're protecting your rims.

[94_AcCoRd_EX]

Originally posted by Accord Man


I know comfort wise it doesnt feel too good but you're protecting your rims.

and higher psi keeps "tire roll" to a minimum.

[Sivik]

what's tire roll?

[spoogenet]

Tire roll: when you corner at high speeds, the sidewalls will flex, aka roll. Thus if you were to freeze motion and look at the car, the tire sidewall would not be perpendicular to the pavement like it usually is when the car's parked. This adversely affects your cornering performance.

Higher PSI reduces sidewall flex or tire roll, whatever you want to call it.

b

[Maxvla]

when you change wheels your rotations of the wheel per minute usually change. you need to measure the overall circumference of the wheel/tire together and compare them to the stock wheels/tires. if it is smaller (which it probably is not) then your car will be going slower than what the speedo shows. if it is larger however (likely it is) your car will be going faster (depending on the size difference much faster) than your speedo shows. it could be off as much as 10mph. so get your tape measure out and get to work so you don't get a big ticket for speeding when you had no clue.

[Sivik]

ok, i just measured them and they are the same size... 23" diameter, and since C = 2*pi*r (or D/2) the circumference is the same. So i don't see why i need to change my speedo at all.

[Maxvla]

ok.. looks like your set then. just trying to save you from getting the donut clan on your bumper.

[spoogenet]

Not sure what your Civic comes with stock, but with the stock Accord wheels, you'd have to change the total diameter by 2" to be off 10mph at 100mph.

If you switch the 195/65/15 for 225/40/17 you change your speed by 3mph at 100mph. Not a whole lot of cause to get the wigwags blaring, except for the going 100mph part. :)

Or maybe I'm just bad at math this late at night.

b

[Maxvla]

the civics are coming with 14" wheels are they not?

3 inches in the rim is a big change... with the low profile tires you should be alright though.

[spoogenet]

Fair enough. As I said, I dunno what the Civics come with, so I can't do the calcs to see how much off they'd be....I just know for the Accord. Even going 18" on the Accord with 225/40 or 215/40 won't change the speedo or odometer much.

I guess with the dinky wheel/tire combo on the Civic then it's not too hard to go up a ways in total diameter. :)

b

[4jacks]

you guys are funny...

it all depends on the old tire size and the new tire size ...

here is a helpful link that you type in your old tire size and your new tire size and it will calculate how much your messed up :crazy: :crazy:

http://www.2k1civic.com/stuff/tire_calc.cfm

[Maxvla]

well according to 4jacks calculator the difference in 185/60/14 which is pretty close to your stock size and 205/40/17 is very negligable.

3% to slow. so at 100mph your speedo would register 103mph.

[Racing Rice]

We always ran no more the 32 psi in our 17s and 18s, they ride so much better that way. You should have to worry about sidewall role as much on a real lowprofile tire like that since there isnt much sidewall and the sidewall are pretty hard. Just watch potholes.