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Smaller tires

Discussion in 'Chevy Trucks' started by GLS, Jan 4, 2002.

  1. GLS

    GLS Senior Member
    Messages: 248

    I have an '89 c-1500 silverado that has smaller tires on it than what it originally came with. I have noticed that the speedometer reads about 4mph slower than I think it should...I was following my dad in a different vehicle and noticed that while he was going 60, I was only going 56...

    So, do smaller tires affect the speed, and if so, is there a way to fix the speedometer? If not, i'll just remember that I can go an extra 4mph over.

  2. TurfPlus

    TurfPlus Senior Member
    Messages: 179

    You will have to chance the gear in the tail shaft. I can't remember if Chevy has the speedo gear in the trans or trasfer case and I just did a trans in our Chevy the other day. Your local dealer should be able to help you with the corect gear.
  3. Randy Scott

    Randy Scott Senior Member
    Messages: 142

    I'm not 100% sure, but wouldn't the speedo read faster than what you really are going if the tire is smaller than what it is calibrated from the factory. The tires will be spinning more revolutions yet trvaeling less distance with a smaller tire. I think your speedo would read 65 when you're actually going 60, something like that. Also, what makes you think your dad's speedo is correct?
    Last edited: Jan 5, 2002
  4. Alan

    Alan PlowSite.com Addict
    Messages: 1,393

    Randu got that right, your speedo error should be to read faster than actual speed. The error is only about 6%, I've seen new ones that were off 5% right out of the box. I'd live with it and go back to the right size tire when you buy new skins.
  5. GLS

    GLS Senior Member
    Messages: 248

    Thanks guys...

    I'll probably stick with it for now, and when I need new tires, just buy bigger ones.

  6. John DiMartino

    John DiMartino PlowSite.com Veteran
    Messages: 2,154

    Dodge's seem to read a hair fast,stock,I put 285 tires on mine,and it reads about 2 mph off,says 58 when im doing 60,it should 7% off,but its only about 3% off.Mine had 265/75r16 tires stock,so i went from 30.8-to 32.8 diameter.