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07-24-2012, 07:32 PM
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#1 |
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Registered User
Join Date: Jul 2012
Location: Anderson,SC
Posts: 953
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Factory tire size
I recently acquired a 1970 C10 and the speedo is off by about 30%. I think this is in part to the tires being too large.
The truck is a factory 307 w/3 on the tree. What would the factory tire size and rear end have been? Posted via Mobile Device |
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07-25-2012, 12:16 AM
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#2 |
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Registered User
Join Date: Nov 2011
Location: Sheffield, ALA
Posts: 2,471
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Re: Factory tire size
G-78-15 is the factory size.I think that comes out to 215-75-15. I'm probably wrong but its close.I forget what ratio but I think mine had 3:73.
I'm running 255-70-15 on mine now and it is running 3 mph faster than speedometer. |
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07-25-2012, 12:52 AM
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#3 |
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Registered User
Join Date: Aug 2010
Location: Edwards, CA
Posts: 7,503
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Re: Factory tire size
Welcome to the board!
The G78-15B tires and 3.73 rear ratio were standard for your truck. That translates to about a 28" dia. tire. Here is a tire chart link as well. http://www.tirerack.com/tires/tirete...sionchart.html
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Thanks, Tim * VIN/Model Decoders * Power Team Charts (engine/transmission/gear ratio) * Post Your Pickup SPID ** Blazer SPID ** Suburban/Panel SPID * RTFM ... Read The Factory Manuals... download 'em here Highlanders ** Do you have a 1972 Plaid Pickup? ** Plaid Blazer ** Plaid Suburban |
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07-25-2012, 01:11 AM
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#4 |
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Senior Member
 
Join Date: Feb 2001
Location: New Madison, Ohio
Posts: 21,373
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Re: Factory tire size
Hey clemsonteg ...
 to the forums and  from Ohio.By the way we luv pics 
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A husband can be right...or...A husband can be happy.  67-72 Chevy and GMC Trucks...The Classic Truck for the Classic Folk.  1970 CST Two tone green, 402BB, 400 Automatic, Tach, Buckets, AC, AM-FM, Tilt, GM CB, GM 8 Tract, LWB, etc   JOHN 17:3...The better side of "LIFE" Remember: Everyday is a good day...Some are just gooder! |
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07-25-2012, 10:57 PM
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#5 |
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Registered User
Join Date: Jul 2012
Location: Anderson,SC
Posts: 953
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Re: Factory tire size
Thanks for the info! Currently the tires are 31x10.50x15 so that would make the speedo off by 5 mph at 40 mph. When my speedo says 40 I'm actually going about 55. Guess I need to check that rear end ratio. Sounds like its been changed over the years
Here's a pic. It's a solid 30 foot truck. Some rust and needs some work, but it runs and drives which is what I wanted to start with  Posted via Mobile Device |
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