Yet another tire question...

[Mrlunchbox]

Hi all, I currently have the stock 255 by whatever tires on my 03 ST. If I go with the same width but a 235 what can I expect in terms of the ride? Would there be a difference in ride height? How would it affect MPG and the spedo if at all? Thanks!

 

[Tom Schindler]

If I go with the same width but a 235 what can I expect in terms of the ride?

A 235 tire is not as wide as a 255 tire is.





Tom

 

[George T]

Yea, the first numbers of a tire size are the width. So you would be getting skinnier tires...I dont see why you would want to do that though.

 

[Mrlunchbox]

Wait... I have been wrong my entire life? I feel like and idiot... So how is a tire measured then? I thought the 255 was height and the 70 was width? Do I have it backwards?

 

[Mark Daskievige]

You got it right , 50 -60 - 70 is width ...the bigger number is height . if you go with a 235 you would be losing height and tire be smaller , also smaller tire would take more resulotions to turn so be losing speed .IE going slower then your speedometer says you are . My 94 dodge <bought used>originally had 14 inch rims and someone had swapped for 15 inch rims and larger tires . I was going 5-10 miles faster at higher speeds then speedometer was saying didnt even know it till i got a few warning tickets for speeding and talking to the cops .You'd probably want to get speed recalibrated after changing tires . As for the ride it might seem a little firmer/harder of a ride . think of Low riders ... they always feel the bumps harder once they go to lower profile tires , but dont think it would be as bad as that .

 

[Dan Long]

No, the bigger number is width. The smaller number is the aspect ratio,so a 255/70-16 would be 255mm of tread width x 70%, equals a sidewall height of 178.5mm on the top and bottom of the 16" rim.

 

[George T]

I dont think that is quite right. 50, 60, 70, etc is the aspect ratio. The higher the number, the taller the tire will be, which is true.



Go down to "Section Width" and "Sidewall Aspect Ratio" and that should help you understand a little bit more.

 

[Tom Schindler]

The first number is the width. A 255 tire is 255 mm wide at the sidewall. The 50-60-70 etc. is the ASPECT RATIO, NOT the width. The last number is the rim diameter.



For example...



235/70-16 tire is...



235 mm wide (235/25.4=9.25" wide) with a sidewall of 70% of the 235 mm. (235*.70=164.5 mm 164.5/25.4=6.47" sidewall)



255/70-16 tire is...



255 mm wide (255/25.4=10.03" wide) with a sidewall of 70% of the 255 mm.

(255*.70=178.5 mm 178.5/25.4=7.02" sidewall)



What EXACTLY are you wanting. Same width of tire, larger rim diameter?





Tom

 

[Steve McKellop]

FWIW, my '01 4x2 XLT came with 255/70R16 tires and my '02 4x4 came with 235/70R16's. I would have figured it to be the other way around ........ go figure. So the ST did come with both of those sizes. I will be putting the 255's on my 4x4 though.

 

[Mrlunchbox]

The reason I started the whole thread was because one of my coworkers is willing to sell to me a nice set of tires that are almost brand new. I "think" they are 235/85/16 . Because I thought I was measuring the tire right I was under the impression that would lower my ride height. But now that I learned different these tires should be bigger right? So if I were to go with that tire lets says what would that do to my ride height and spedo?

 

[Todd Z]

Back in the day tires were called as a 40,50,60, 70....



The way people are explaining it to you is correct....



the first number is with in MM the second is the percentage the tire is high as wide and the third is the rim height...



The P in front or LT is passenger or Light truck.... Stronger and stiffer sidewall..



Todd Z

 

[Mrlunchbox]

So If I currently have a 255/70/16 and I go to a 235/85/16 The new tire would be narrower but taller? Is that correct?

 

[Tom Schindler]

The new tire would be narrower but taller? Is that correct?

Yes...



255/70-16 tires are about 30.056" tall and 10.03 wide (255/25.4=10.04) (10.04*.7=7.028") (7.028*2+16=30.056")



235/85-16 tires are about 31.72" tall and 9.25" wide. (235/25.4=9.25") (9.25*.85=7.86") (7.86*2+16=31.72")





Tom

 

[Mrlunchbox]

Excellent! Thank you for the clarification! I still can't believe I have been doing it wrong for so many years. :wacko:

 

[Kevin Lang]

I know I learned something here today.

 

[Brian Barham]

Metric is a bitch. That's why I like 33/12.5/16 33" tall 12.5" wide 16" wheels ...... easy as pie.