Another New guy with a question.

[Idually]

First off... Thanks to this site and all if the folks that contribute to it. It is a great place!



In April I purchased my first(and maybe last) Diesel truck and I'm not going back. I love it! It is a 1993 W350 Clubcab CTD with 35000 original miles (I'm nearly positive that they are original miles, but that is different topic). The truck is clean, clean and has not been mistreated from what I can tell.



On to tires. Can some refresh my memory as to how tires are sized? What do the numbers tell me?



The tag on the door frame calls for 215's. The tires currently on the truck are 225's. Not a big difference, but the tires on the truck look really small, to me.



My question is this: How are these tires affecting the my Speedometer AND are they affecting the odometer? The truck seems to shift a bit quick



In short, I want a taller tire on the truck at some point(the current tires have some miles left on them), but for now what might be going on?



Thanks in advance!



Andrew



P. S. I will have plenty of pics very soon!

 

[sparks57]

Welcome!



About your tires, shorter tires make your speedometer read high. With those tires, it should only be a couple of miles off.





Tires are sized like this: 215/75r16



The first number is the total rubber width, the second number is the aspect ratio of the tire (height/width, the higher the number, the taller and skinnier it is) and the last number is the rim size (you, more than likely, have 16" rims).



Most guys are running 235/85r16 tires on our trucks. You can run bigger than that though. It's a really good sized tire.



I am running 265/75s right now. No clearance problems. I used to run 285/75 and only rubbed on occasion on the steering arm.

 

[swampfox]

The first number is the tread width (215) the second number 70, 75, etc is the height of the sidewall. Since you have duel rear wheels you need to use a narrower tire than the single rear wheel trucks ( for clearance purposes). The 225s shouldn't affect your speedometer/odometer too much but taller tires/wheels will. If you have a mechanical speedometer you may be able to change the speedo gear in the transmisson. For tire specs go to the Michelin website, they show the outside diameter of various sizes. I don't know but an aftermarket supplier may make 19" wheels for your truck, otherwise you can check out tires in the 215,225, by 85 size.

 

[sparks57]

Woops!



I forgot you have a dually!



Anyways, that doesn't change much... just ignore the part about me running bigger tires. I can because I have single wheels.

 

[jbolt]

FYI-



Myself as well as some others have posted that with the factory tires the indicated speed was about 5mph faster than actual. When I changed to a taller tire the error was corrected, along with my MPGs



I've always wondered if it was done on purpose to raise the MPG rating. Naw thay wouldn't do that would they



Jay

 

[Greenleaf]

Check out the thread by DKasper titled "Lifting a 2WD" It appeared about three weeks ago... ... ... ...



Scott