C 20 Tire Size

[muley]

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.

[Sicklajoie]

265/75/16 will definitely work.

[jocko]

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...

[Sicklajoie]

I believe 235/85/16 and 265/75/16 are the same height, just that the 235s are a narrower treadwidth.

[jocko]

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.

[Sicklajoie]

I went from 235s to 265s on mine. I like the slightly meatier look.

[muley]

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.

[Sicklajoie]

What you really need to do is post some pics of your truck!

[muley]

If I figured out how to do this, I'll send more.

[muley]

I need more room than here in the driveway.

[Sicklajoie]

Nice!!!

[muley]

Everything is the way it was sold new.

[muley]

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.

[derotoreut]

On my '69 C20 I'm running 285/70-17 tires with H2 Hummer wheels on all 4-corners..

[1968C20CST]

The hummer wheels look nice.

[BlacklandCamper]

Originally Posted by derotoreut

On my '69 C20 I'm running 285/70-17 tires with H2 Hummer wheels on all 4-corners..

Originally Posted by 1968C20CST

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.

[Sicklajoie]

I think he put 73-87 springs in the front to level it out.

[BlacklandCamper]

I thought that might be the case. I really need to do that to my 71.

[derotoreut]

Originally Posted by BlacklandCamper

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"

[BlacklandCamper]

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

[derotoreut]

Keep us posted. I can't wait to hear how it works out for you. Like to see pictures for sure!

[72MARIO]

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.