Found some Ravines off of a 2000 cherokee I'd like to put on my 88. They have 225 16s on them. Will these throw my speedo way off?

 

Rim size doesn't typically change vehicle speed reading. Its the tire size.

If its the same size tire as your last one, with a larger opening for the rim, your speeding will not change.

 

Interesting I didn't know that, I run 235 15s now and these have 225 16s.

 

I'll look for it but there's a tire size calculator. You plug in info and it tells you height in inches.

Edit- this is one, not the one I was looking for, but It tells ya some good info, plus speedo changes
http://www.net-comber.com/tirecalc.html

 

If you have 31"tires and 17" rims, and you switch to 31"tires with 16" rims you still have the end size of the a 31"tire.

 

The only thing would change would be the overall rating of the tire/rim combo (+1,+2,+3...etc) at a certain point, the weight balance of the tire may begin to approach what the OEM braking systems were designed to handle under load.

 

We are discussing rim size changing the speedo's accuracy...

 

Yet again I must agree with Gee oh Dee.

 

X3, Rim size will have nothing to do with the speedo, the tire size is what changes it.

 

What is the middle Humber of ur tires and te new tires... 235/??r15 and 235/??r16...
That number is very important when it comes to tire height... It is the aspect ratio of the tire... So if you had let's say a 235/55r15 and a 225/65r16 those might be the same diameter... But if you had both 2??/55r15 or 16 then it will change the diameter of the tire... So then it might throw your speedo off... So unless you were putting same size tire from 15 to 16" wheels, it will change a bit...

I understand your issue was with going from 15 to 16" wheels, but this is important when doing so and it seemed no one else had explained it to you.

 

tires are IIRC 235(width in CM) / 35 (sidewall hieght in CM) / 15R (rim size in inches) but its been a while since i was told this...

 

First of all...Ravines are 15" wheels, so if they're 16" wheels they're not Ravines, or if they're definitely Ravines, then they're 15" wheels.

Secondly, if you want to convert tire size to inches for comparison, here's how to do it:
((Section Width x aspect ratio x 2)/2540) + rim size = diameter in inches

So, for example on a 225/75/15 tire:

((225x75x2)/2540) + 15 = 28.29 inches.

Of course these are all theoretical, so actual size will vary by manufacturer. Also, since the aspect ratio is a percentage (ie. the side wall is 75% of 225mm tire) it's possible to go up in width, with a smaller aspect ratio and maintain the same height. For instance, on my CTS-V a lot of guys go to a 275/40/18 in the rear instead of the stock 245/45/18, because they're wider for more grip, but height is the same, and thus the speedo stays the same.

Sorry for the long post, hopefully someone will find it informative.