# Changed tire size...speedometer adjustment needed?



## sirreverence (Jul 18, 2006)

I just took a set of 255-70-15 off my '88 king cab and put the stock tires and rims back on. 
I think they are 195-75-14...dang do they look small after having those bigger tires on but the book says that's what came on the truck when new. ?
My question is this: Do I need to do some sort of speedometer adjustment to compensate for smaller tires? I've noticed that it 'seeems' like I'm not actually going what the speedometer says...I though perhaps it was just a sensation from the smaller wheels and sitting closer to the ground. I do all my work on our cars, mostly Saabs and Volvo...so this is my first truck tire changeout.
Any advice or help appreciated! 
Cheers-
sirreverence


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## dmroberson (Jun 24, 2004)

If they're the stock size, you don't have to adjust the speedometer, unless you did after putting on the larger ones.

When I put larger rims on my sentra, I used this link. This one will compare your stock tire & rim size with the larger/smaller size and also give you an idea of how far off your speedometer will be. I went from 195/60/15 to 205/45/17 and the speedometer stayed about the same. the site says it reads 60mph when I'm doing 60.1mph, won't see that on the gauge though. Hope this helps

http://miata.net/garage/tirecalc.html


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## jerryp58 (Jan 6, 2005)

sirreverence said:


> I just took a set of 255-70-15 off my '88 king cab and put the stock tires and rims back on.
> I think they are 195-75-14...dang do they look small after having those bigger tires on but the book says that's what came on the truck when new. ?
> My question is this: Do I need to do some sort of speedometer adjustment to compensate for smaller tires? I've noticed that it 'seeems' like I'm not actually going what the speedometer says...I though perhaps it was just a sensation from the smaller wheels and sitting closer to the ground. I do all my work on our cars, mostly Saabs and Volvo...so this is my first truck tire changeout.
> Any advice or help appreciated!
> ...


If the speedometer was never changed then it should now be accurate with the stock size back on the truck (whereas it was reading low [~14%] before).


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## sirreverence (Jul 18, 2006)

Thanks eveyone for the help. The larger tires were on the truck when I purchased it, so I'm not sure if the speedometer was reset at that time. I'll check it out this weekend and correct if needed.
cheers!


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## Mylt1 (May 10, 2006)

if you have or have access to a gps you can check the speedo. a shop is gonna charge you anywhere from 50-125 bucks just to tell you its off.


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## himilefrontier (Jan 21, 2003)

To check it, try pacing a friend with a new or stock low mileage car and then see where your truck is as fear as speed goes in relation to his.


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