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Old 03-14-2014, 05:43 PM   #1
muley
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C 20 Tire Size

Hola,

I've got a 1969 C 20 Longhorn. The tires on it now are 245/75/16. I'm curious if anyone else runs a bigger size. I've got a 4:10 rear axle and would like to get a little better mileage if I can, but I want to make sure the fronts don't rub on turns.
Thanks if anybody can add to this.
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Old 03-14-2014, 06:08 PM   #2
Sicklajoie
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Re: C 20 Tire Size

265/75/16 will definitely work.
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Old 03-14-2014, 06:28 PM   #3
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Re: C 20 Tire Size

Yep, what sicklajoie said. 265/75/16 Same thing I've run on my 72 - no interference, not even close. (the last pic is a member's and I'm almost certain that these are even taller - will try to see what size later on some pics I have on another computer - but I "think" they are 235/85/16s). Still wish I'd bought this old saddle custom camper...
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Old 03-14-2014, 06:51 PM   #4
Sicklajoie
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Re: C 20 Tire Size

I believe 235/85/16 and 265/75/16 are the same height, just that the 235s are a narrower treadwidth.
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Old 03-14-2014, 07:21 PM   #5
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Re: C 20 Tire Size

Excellent point, and, you Sir, are correct! I just cross-checked on the BFG site, they are within 0.2" of each other for diameter. So, just depends which aspect ratio you prefer, tall and skinny or a little wider and same diameter.
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Old 03-14-2014, 07:28 PM   #6
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Re: C 20 Tire Size

I went from 235s to 265s on mine. I like the slightly meatier look.
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1970 C/20 - 402/TH400/3.54s - 74K miles
2003 GMC Sierra 2500 - Wheatland Yellow
Niner Progression Thread: http://67-72chevytrucks.com/vboard/s...d.php?t=697183
Classic Trucks article: https://www.motortrend.com/features/...et-c20-driven/
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Old 03-15-2014, 11:18 AM   #7
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Re: C 20 Tire Size

Thanks for the input! I run 235/85/16 on my Suburban, and like them just fine. My plan is to go as tall as I can to try to gear it up a bit, without interference with the steering or suspension.
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Old 03-15-2014, 11:30 AM   #8
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Re: C 20 Tire Size

What you really need to do is post some pics of your truck!
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1970 C/20 - 402/TH400/3.54s - 74K miles
2003 GMC Sierra 2500 - Wheatland Yellow
Niner Progression Thread: http://67-72chevytrucks.com/vboard/s...d.php?t=697183
Classic Trucks article: https://www.motortrend.com/features/...et-c20-driven/
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Old 03-15-2014, 12:30 PM   #9
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Re: C 20 Tire Size

Name:  image.jpg
Views: 512
Size:  79.7 KB
If I figured out how to do this, I'll send more.
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Old 03-15-2014, 12:42 PM   #10
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Re: C 20 Tire Size

Name:  image.jpg
Views: 502
Size:  47.4 KBI need more room than here in the driveway.
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Old 03-15-2014, 12:43 PM   #11
Sicklajoie
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Re: C 20 Tire Size

Nice!!!
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1970 C/20 - 402/TH400/3.54s - 74K miles
2003 GMC Sierra 2500 - Wheatland Yellow
Niner Progression Thread: http://67-72chevytrucks.com/vboard/s...d.php?t=697183
Classic Trucks article: https://www.motortrend.com/features/...et-c20-driven/
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Old 03-15-2014, 12:45 PM   #12
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Re: C 20 Tire Size

Everything is the way it was sold new.
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Old 03-15-2014, 12:52 PM   #13
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Re: C 20 Tire Size

In the jockey box was the 1969 Warranty Pamphlet filled out by the original owner from a dealership 30 miles away that is still in business.

350 c.i., Sm460 4 speed, Eaton HO 52 rear with 4:10 axles.
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Old 03-15-2014, 10:03 PM   #14
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Re: C 20 Tire Size

On my '69 C20 I'm running 285/70-17 tires with H2 Hummer wheels on all 4-corners..
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Old 03-15-2014, 11:14 PM   #15
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Re: C 20 Tire Size

The hummer wheels look nice.
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Old 03-16-2014, 01:07 AM   #16
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Re: C 20 Tire Size

Quote:
Originally Posted by derotoreut View Post
On my '69 C20 I'm running 285/70-17 tires with H2 Hummer wheels on all 4-corners..
Quote:
Originally Posted by 1968C20CST View Post
The hummer wheels look nice.

Agreed. Those look awesome.
Is that 2wd? What did you do to get yours level? That is the stance I am looking for.
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Old 03-16-2014, 07:34 AM   #17
Sicklajoie
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Re: C 20 Tire Size

I think he put 73-87 springs in the front to level it out.
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1970 C/20 - 402/TH400/3.54s - 74K miles
2003 GMC Sierra 2500 - Wheatland Yellow
Niner Progression Thread: http://67-72chevytrucks.com/vboard/s...d.php?t=697183
Classic Trucks article: https://www.motortrend.com/features/...et-c20-driven/
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Old 03-16-2014, 11:47 AM   #18
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Re: C 20 Tire Size

I thought that might be the case. I really need to do that to my 71.
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Old 03-16-2014, 10:34 PM   #19
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Re: C 20 Tire Size

Quote:
Originally Posted by BlacklandCamper View Post
Agreed. Those look awesome.
Is that 2wd? What did you do to get yours level? That is the stance I am looking for.
It is a 2WD C20. When I did front disc conversion I changed out the front springs. I installed some HD springs (P/N 2772074) bought from NAPA. Tires do not rub at all. They are 285/70-17 tires with H2 Hummer wheels. The ride is a bit stiff, but hey it's a 3/4 ton truck. I never did anything with the rear springs (yet). Here's a comparison of the springs:

The stock HD C20 springs are as follows:

http://www.napaonline.com/Catalog/Ca...752_0162319756

Part No.: 2771752
No. of Coils: 7.92
Free Height: 12.94"
Spring ID: 3.68"
Spring Load Height: 10"
Design Load: 2950
Spring Rate: 1016
Wire Diameter: 0.812"

The springs I put on from C10, C20, C30 from 1973-83. They are as follows:

http://www.napaonline.com/Catalog/Ca...074_0162301536

Part No.: 2772074
No. of Coils: 8
Free Height: 13.61"
Spring ID: 3.676"
Spring Load Height: 10"
Design Load: 3841
Spring Rate: 1060
Wire Diameter: 0.83"

You could also use C30 mid '80's 1-ton springs, but I thought they would be too stiff. Those are:

http://www.napaonline.com/Catalog/Ca...085_0162304063

Part No.: 2773085
No. of Coils: 7.93
Free Height: 13.34"
Spring ID: 3.65"
Spring Load Height: 11"
Design Load: 3289
Spring Rate: 1318
Wire Diameter: 0.906"
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1970 SWB Fleet K10 4X4, 5.3L LM7, 4L60E, Dakota Digital RTX, Vintage Air, Ididit tilt
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"Kick out your motor and drive while you're still alive - kick it out!" - Heart 1977
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Old 03-16-2014, 11:45 PM   #20
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Re: C 20 Tire Size

I was thinking along the same lines, but I wouldn't mind a little stiff. The stock spring replacements I list at work are...

Free: 12.94
Installed: 10
Load: 2950
Rate: 1016
Moog part # 6104

The springs I thought of are off of a 1988 R30, there are three versions, standard, with R42 suspension, and R42 HD suspension.
I was going to use the R42 HD option.

Free: 13.59
Installed: 11
Load: 3788
Rate: 1464
Moog part # 6560S

The R42 springs are,

Free: 13.19
Installed: 11
Load: 3289
Rate: 1501
Moog part # 6560

I am looking forward to both seeing how my truck looks leveled out, and driving it. My stock springs are REALLY worn out. The PO already put wedge spacers in them, and they still sag.

/hijack
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Grunt: 1971 C20 Custom Camper. Runs/Drives/Kinda stops. 350Ci, TH350. 4.10:1 D60. Eight Lug LWB is more better. Hell no its not fast!

Donkey: 93 Nissan D21, the farm truck. My 1/2 ton SWB. The Indomitable Datsun.
1st BN 3rd MAR. '00-'04

Last edited by BlacklandCamper; 03-16-2014 at 11:55 PM.
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Old 03-17-2014, 09:07 AM   #21
derotoreut
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Re: C 20 Tire Size

Keep us posted. I can't wait to hear how it works out for you. Like to see pictures for sure!
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My 71 SWB build:http://67-72chevytrucks.com/vboard/s...d.php?t=651394

1970 SWB Fleet K10 4X4, 5.3L LM7, 4L60E, Dakota Digital RTX, Vintage Air, Ididit tilt
1971 SWB Fleet C10 - Original SWB Arizona truck, new custom restoration project

"Kick out your motor and drive while you're still alive - kick it out!" - Heart 1977
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Old 03-18-2014, 01:53 PM   #22
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Re: C 20 Tire Size

I had 285 75 16 on 16x8 rims and they rubbed the front bottom of the front fender. I have a 3" fabtech lift coil. I swapped them out to 265 75 16. with the bigger tires my ball joints and idler arm hated me. Under 35000 miles and they were toast.
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