Pictures of your C10 tires

[MikeB]

My "new to me" 82 SWB C10 has 6.5" Rally wheels (from a van?) and 255-70x15 tires that are nearly shot. The glove box sticker shows the truck originally came with FR78x15 tires, which are equivalent to 205-75x15. That sounds really small, but I know my 250 six would like their shorter height with the lame 2.73 axle, and my speedometer would be more accurate.

I'd appreciate pictures of trucks with 205-75, 215-75. and even 225-75 tires, if anyone has 'em. Also, what the heck, 235-70x15.

[brakenit]

Pretty sure my '84 was still sporting the stock size 205/75/15's when I got it.

[D13]

Mine are P235 75R15's, I can't imagine anything smaller withstanding the weight of my 6.2 diesel, or a BBC. That's on standard truck ralley's.

[Keith Seymore]

Base tires are really pretty small, because any money you can save per tire is multiplied by at least 4 (some trucks did not get a spare) or 5.

Here's mine with P235/75R15s on a 15x8 rally.

K

[MikeB]

Thanks, guys. Keep 'em coming. Yeah, the 205s look awfully small in those big wheel wells!

I've had a few trucks over the years that ran 235-75x15, which has always been a popular size to run on pickups with 15" wheels. In fact, I initially thought I'd buy 235s, but then realized my axle is a 2.73, and wheel width is only 6.5".

Keith, what the heck was GM thinking when they made 2.73 the "standard" ratio for a 6-cylinder, manual trans pickup? The 3.50 1st gear makes it easy to get the truck rolling, but the gaps between gears is just nuts. Then again, my current 255-70 tires are 2" taller than a 205-75, which makes the 2.73 seem like 2.54.

[old Rusty C10]

my truck has 225 75 R 15 tires on it pics while it was still a project

[walkerb]

235 75 15

[geezer#99]

225 70 front and 235 75 rear. Originals where 205 75's.

[Keith Seymore]

Originally Posted by MikeB

Keith, what the heck was GM thinking when they made 2.73 the "standard" ratio for a 6-cylinder, manual trans pickup? The 3.50 1st gear makes it easy to get the truck rolling, but the gaps between gears is just nuts. Then again, my current 255-70 tires are 2" taller than a 205-75, which makes the 2.73 seem like 2.54.

Fuel economy!

I always start at 3.42 and then move from there when choosing an axle ratio. 3.42 and 3.73 pretty much cover all my needs.

K

[MikeB]

Originally Posted by Keith Seymore

Fuel economy!

I always start at 3.42 and then move from there when choosing an axle ratio. 3.42 and 3.73 pretty much cover all my needs.

K

I didn't know CAFE standards applied to light trucks.

Yeah, my little 250 six would probably like 3.73, but not on the highway! I'm thinking shorter tires for the time being, and maybe 3.23-3.42 gears if I keep the six. I've done R+P swaps on two 10-bolts and one 12-bolt, so I'm armed and dangerous!

Back in the late 80s I had an 81 C-10 with 305, TH350C, and 2.56 axle (!). If the T/C locked up at speeds less than 40-45 mph, the entire truck would shudder. Drove it around in 2nd gear a lot, until I installed an under-dash switch to control the lock-up. And I only engaged the switch when driving at highway speeds.