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#1 |
Registered User
Join Date: Jul 2014
Location: Mora MN
Posts: 172
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Tire recommendations???
Buying tires this week for the 68 C20. I have a 327, turbo 350, and 4.10 gears. Tire shop says I should get 265/75/R16's that are 31.7 tall. I'm looking at P265/70R16's that are 30.6 tall. Plans are to lower the truck with coil springs too. I will drive on the highway a bit so I do want something driveable. Is the advertised tire diameter the tire off the truck or on it compressed with the weight of the truck? Any thoughts on this since I'm no tire expert??? Thanks!!!
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#2 |
Registered User
Join Date: Aug 2009
Location: Bowser
Posts: 13,619
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Re: Tire recommendations???
The advertised tire diameter is always off the truck.
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#3 |
Registered User
Join Date: Jul 2014
Location: Mora MN
Posts: 172
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Re: Tire recommendations???
So it will compress a bit? My concern is that if I put too tall of tires on I won't be able to lower it much and if I put too short of tires on it the truck will be winding rpm's too high down the highway. Just wondering what other people are running on there trucks with similar motor, trans, gears for tire sizes. Thanks!!!
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#4 |
Senior Member
![]() Join Date: Jul 2012
Location: Knoxville, TN
Posts: 499
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Re: Tire recommendations???
How low are you wanting to go?
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1971 Chevy C10 Cheyenne (sold for Mazda) 1963 Chevy Corvair Pro-Touring Project 2012 Mazda 3 i Sport sedan http://www.dracoautodesigns.com/ |
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#5 |
Registered User
Join Date: Aug 2006
Location: Redmond, WA
Posts: 6,332
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Re: Tire recommendations???
That's a little taller than mine, which work fine on my 3/4 ton. Solution is simple. Don't lower it. But if you must I'd do the suspension part before the tire part so that you know it'll fit.
Funny how about half of the people install lift kits and about half lower their trucks. I figure on average, stock ride height must be correct :-)
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1970 GMC Sierra Grande Custom Camper - Built, not Bought 1969 Pontiac 2+2 427/390 4-speed Coupe 1969 Pontiac 2+2 427/390 4-speed Convertible |
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#6 | |
Registered User
Join Date: Aug 2009
Location: Bowser
Posts: 13,619
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Re: Tire recommendations???
Quote:
Depending on the type of tire or who makes it will determine the installed height. A p-metric (passenger car) tire will have a shorter installed height than an LT (light truck) designated tire in the same size. Due to tire construction. Side wall stiffness is greater in the Lt tire. So it squishes less. Usually a tallish tire won't be a problem up in the wheelwell. Interference is a problem on the lower fender front and rear of the tire. |
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#7 |
Vintage 4x4s
Join Date: Sep 2010
Location: Prior Lake, MN
Posts: 4,305
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Re: Tire recommendations???
You'll want LT series if your towing or hauling heavy. Those gears are pretty low for a non OD trannsimission. At least you have the rev happiest motor! Welcome from MN!
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67 GMC K1500 Custom- 305V6 SM420, PTO, Ram Assist, yellow (the outcast) (project period correct upgrades) 67 GMC C2500 351V6 TH400, AC, PS, PB (can't decide what to do with. Update, decided to keep and will restore ![]() 86 CHV K30 502 th400, apple red NEW 71 CHV K20 350 SM465, ochre (saved work truck) 71 CHV K20 292 SM465, white, tach, PTO, (future project) 72 CHV K20 350 350th, medium blue (project stocker) 01 CHV K2500hd crew, indigo blue ^3 dont run and the others don't see winter either '86 K30 Cummins "Fireside" thread: http://67-72chevytrucks.com/vboard/s...d.php?t=649649 '71 K20 "get driveable" thread: http://67-72chevytrucks.com/vboard/s...d.php?t=590642 '72 K20 Build Thread: http://67-72chevytrucks.com/vboard/s...=493477&page=6 |
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#8 | |
Registered User
Join Date: May 2006
Location: Jonesboro, AR
Posts: 916
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Re: Tire recommendations???
Quote:
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#9 |
Registered User
Join Date: Jul 2014
Location: Mora MN
Posts: 172
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Re: Tire recommendations???
I'm hoping to lower 2" in the front and 4" in the rear. I'm thinking I will do the tires first and then do some measuring. If I can't do the 2/4, I'll have to go less but I need to have it drive able. Thanks!!!
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#10 |
Registered User
Join Date: Aug 2009
Location: Bowser
Posts: 13,619
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Re: Tire recommendations???
Here's a neat link. Just to see what wheels and lowering does for you. This is one of many on the web.
http://tbcwheels.ridestyler.com/?mode=webbot |
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#11 |
Registered User
Join Date: Aug 2010
Location: Edwards, CA
Posts: 7,503
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Re: Tire recommendations???
There is only about a 100rpm difference (2824 &2926 @65) between those two tire diameters.
A tire manufacturers diameter (from their specs table) is the tire mounted on the recommended size wheel, inflated but unloaded. While you can use the "formula" to size up a tire the actual measurements are the numbers to use. With 4.10 gears you are not going to be loafing down the highway. It was set up to carry a load. If it helps any most 68s had 4.57 gears with the 4.10s optional. http://www.summitracing.com/expertad...tio-calculator
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