Tire time need thoughts on slight size change

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

SirRobyn0

Full Access Member
Joined
Dec 6, 2019
Posts
6,755
Reaction score
11,402
Location
In the woods in Western Washington
First Name
Rob
Truck Year
1984
Truck Model
C20
Engine Size
305
Not to beat a dead horse... but 33” 10.5 15 or 16 is a perfect fit with stock ride height, no modifications needed. No cutting/no lift
You must be registered for see images attach
You must be registered for see images attach
No beat horses here, I find this discussion very interesting. Just for anyone wondering a 33X10.5R15 converted to 16" metric would be 267/81R16 Making the 265/75R16 a about an inch shorter, but within .1" of same width, while the 285/75R16 is basically the same height but is almost 3/4" wider.
 

SirRobyn0

Full Access Member
Joined
Dec 6, 2019
Posts
6,755
Reaction score
11,402
Location
In the woods in Western Washington
First Name
Rob
Truck Year
1984
Truck Model
C20
Engine Size
305
I didn't get a chance to punch this one in before I left work. But a 31X10.5R15 converted to 16" metric is a 266/73R16 so a 265/75R16 is 1/2" taller than the 31X10.5R15 and .1 inches narrower. All of these figures are from tiresize.com/calculator
 

bucket

Super Moderator
Staff member
Super Moderator
Joined
Aug 3, 2010
Posts
30,445
Reaction score
28,348
Location
Usually not in Ohio
First Name
Andy
Truck Year
'77, '78, '79, '84, '88
Truck Model
K5 thru K30
Engine Size
350-454
I ran 285s on my /01 2500HD on 6.5" rims. Unloaded I kept pressures at 65 in the front and 35 in the rear. When hauling loads or towing my travel trailer (31') I aired up to 70. The one thing I noticed is a lot of trailer sway due to sidewall flex the one time I forgot to air up. Never did that again.

@SirRobyn0 I run Wlidpeaks on my K30. I like them as they are Triple Peak rated for snow.

You must be registered for see images attach

I run ours at 50 front and 80 rear on our '00 2500 Burb at all times and it works well for us. On my '78, I ran 50/65 due to the lower rated BFG's on the '99-up aluminum wheels and I really liked that too.
 

SirRobyn0

Full Access Member
Joined
Dec 6, 2019
Posts
6,755
Reaction score
11,402
Location
In the woods in Western Washington
First Name
Rob
Truck Year
1984
Truck Model
C20
Engine Size
305
I ran 285s on my /01 2500HD on 6.5" rims. Unloaded I kept pressures at 65 in the front and 35 in the rear. When hauling loads or towing my travel trailer (31') I aired up to 70. The one thing I noticed is a lot of trailer sway due to sidewall flex the one time I forgot to air up. Never did that again.

@SirRobyn0 I run Wlidpeaks on my K30. I like them as they are Triple Peak rated for snow.

You must be registered for see images attach

I run ours at 50 front and 80 rear on our '00 2500 Burb at all times and it works well for us. On my '78, I ran 50/65 due to the lower rated BFG's on the '99-up aluminum wheels and I really liked that too.

Tire pressure that should be another interesting conversation. So I've been running 60 front / 80 rear all times, I'd probably like to air down the rear when empty for improved ride, but I spend so much time loaded I'd be constantly airing up and down so I have been just leaving them at 80. One thing I've always wondered about, tire pressures are checked cold I think we all know that, what about loaded vs empty. At the shop I've observed, and this depends on the weight of the vehicle but if check the tire pressures on the hoist and then put the vehicle down the weight will increase the tire pressure by 2 -5 PSI. So what happens when I slap a ton of feed in the bed? Or when I'm really bad and get gravel. I'm sure the pressure goes up, but I've never checked. I've never heard a tire manufacture mention this so I assume, that as long as the tire itself is not overloaded, that it's designed to take this increase in pressure, but also wonder if anyone else ever thinks about that.
 

BKING33

Full Access Member
Joined
Aug 24, 2020
Posts
278
Reaction score
795
Location
York Springs, PA
First Name
Brian
Truck Year
1987, 1989
Truck Model
K30, Suburban
Engine Size
6.2, 6.2 turbo
I keep all my tires at 45psi for daily driving. I add 10-15 psi in rear tires when loaded. I don't tow anything heavy with it, so i never air them up to max 80 psi.
I use my truck for heavy stuff.
 

SirRobyn0

Full Access Member
Joined
Dec 6, 2019
Posts
6,755
Reaction score
11,402
Location
In the woods in Western Washington
First Name
Rob
Truck Year
1984
Truck Model
C20
Engine Size
305
I was actually just looking at my door sticker and it say 50 front 80 rear, so I may try running the front at 50 with the new tires and see how I like it.
 

SirRobyn0

Full Access Member
Joined
Dec 6, 2019
Posts
6,755
Reaction score
11,402
Location
In the woods in Western Washington
First Name
Rob
Truck Year
1984
Truck Model
C20
Engine Size
305
Ok here it is. I think I've make my decision. I'm not comfortable going to 285/75R16 for 2 reasons. One is it'll increase my ride height, two is rim width. I know @bucket has said that it would work just fine, but I've had tires wear in the center on my Dodge Dakota for this exact reason. And if that were to start to happen I'd be stuck with it and reduced traction because I'm not going to air down, drive to where I'm picking up feed which is about 100 miles and then air up. I have no doubt that I would have a very good chance of them working out just fine, I just don't want to take the chance.

Last night and this morning I just about had myself convinced that I'd like to put 245/75R16's on the front and 265/75R16's on the back. My reasoning is that my Dakota has 215/75R15s on the front and 235/75R15's on the back and I like the look. Then I thought about why I did that. I did it because the 235's would hit when turning. And I've had problems with the front plowing when trying to turn on softer ground. So that did that in.

So unless someone says something earth shattering to me between now and tonight I'll be ordering a set of 4 265/75R16's, that'll be a little more than an inch wider than factory and about the same height. That way I can get some benefits of the wider tire, without having to go taller, and still be a comfortable width for me.

Thanks for all the input guys. I'll be sure to post pics once they are installed.
 

bucket

Super Moderator
Staff member
Super Moderator
Joined
Aug 3, 2010
Posts
30,445
Reaction score
28,348
Location
Usually not in Ohio
First Name
Andy
Truck Year
'77, '78, '79, '84, '88
Truck Model
K5 thru K30
Engine Size
350-454
Eh, I wouldn't let your findings with a lighter weight Dakota sway you. I've ran 3 sets of 285's on 6.5" rims on Suburbans and they wear evenly across. And I know oodles of other people have done the same with the GMT800 trucks.

But really, the 265 tire should serve your purposes well and that's a fine choice too.
 

SirRobyn0

Full Access Member
Joined
Dec 6, 2019
Posts
6,755
Reaction score
11,402
Location
In the woods in Western Washington
First Name
Rob
Truck Year
1984
Truck Model
C20
Engine Size
305
Eh, I wouldn't let your findings with a lighter weight Dakota sway you. I've ran 3 sets of 285's on 6.5" rims on Suburbans and they wear evenly across. And I know oodles of other people have done the same with the GMT800 trucks.

But really, the 265 tire should serve your purposes well and that's a fine choice too.

I have no doubt that you are right. It's a personal hang up lol. I figure the 265's will be over an inch wider than my current tires, and well if I like them maybe I'll move up to the 285's next time. Also not being able to get E-rated Grabber AT's in 285. I've had a lot of different rigs, with grabbers on it from SUV's to the Dakota for a lot of years, so I'm pretty well sold on them as being the right tire for me.
 
Last edited:

SirRobyn0

Full Access Member
Joined
Dec 6, 2019
Posts
6,755
Reaction score
11,402
Location
In the woods in Western Washington
First Name
Rob
Truck Year
1984
Truck Model
C20
Engine Size
305
Well I ordered the tires on the 26th and they came into the shop this morning at about 9AM. I wasn't expecting them until next week. This is my last day at the shop this week, so I thought great I'll get them on the truck this afternoon. NOOOO, that was not to be. **** hit the fan right after that and I spent pretty much the rest of the day putting out fires. No time for me, but that's the way it goes I guess. If I get into the city in the next 4 days I'll install them sooner otherwise it'll probably be Monday or Tuesday. All I had the time to do what to roll one out up against the truck. They going to look great, and I know I'll love having the General's on it. Should have taken a pic while I had it out at the truck at least, but I'll be sure to snap a few after the install.
 

SirRobyn0

Full Access Member
Joined
Dec 6, 2019
Posts
6,755
Reaction score
11,402
Location
In the woods in Western Washington
First Name
Rob
Truck Year
1984
Truck Model
C20
Engine Size
305
finally today was the day, but only because I made the time for it to happen. First some pictures there will be multiple posts for all of them. Did ya hear that @Rusty Nail, so many pictures I have to do multiple posts, does this thread still suck.... NO!

Anyhow after the pictures then I'll talk about the tires and what I think so far.

First pic. the old Toyo open country A/T, I never liked them, but they had tread so I wanted to use them. Now they have cracks in the tread so they need to be replaced. Time to get my favorite tires on the truck the General Grabber A/T
You must be registered for see images attach



I've just installed the first new tire on the wheel.
You must be registered for see images attach



New tire on the truck. Looking better already!
You must be registered for see images attach




New tire on the front, old one on the rear just for contrast, I should have put the hub cap back on for the pic but you get the idea.
You must be registered for see images attach



Plenty of fender spacing even in a turn.
You must be registered for see images attach
 

SirRobyn0

Full Access Member
Joined
Dec 6, 2019
Posts
6,755
Reaction score
11,402
Location
In the woods in Western Washington
First Name
Rob
Truck Year
1984
Truck Model
C20
Engine Size
305
Looking good with 4 new tires. Unfortunately it turned overcast and rather dark out today, so it's hard to see the tread in the pictures, but you can really see them in person and makes the truck look much more rugged and work ready.


You must be registered for see images attach
You must be registered for see images attach


Gonna be a little bit before I can do a post with what I think of the change, but it'll happen before I go to bed tonight.
 
Last edited:

SirRobyn0

Full Access Member
Joined
Dec 6, 2019
Posts
6,755
Reaction score
11,402
Location
In the woods in Western Washington
First Name
Rob
Truck Year
1984
Truck Model
C20
Engine Size
305
Now what I think. I think the tires look great. I went from 235/85R16 to 265/75R16 both are 10 ply E rated tires, and the new tires are slightly shorter, less than a 1/4" shorter than the old tires, but are just a hair more than an inch wider. There is plenty of clearance on the front for turning. The new tires have a higher weight rating than the old, but both are E-rated. Traction wise the difference so far has been substantial, which having had grabbers in the past on other truck I expected. I haven't had them around the fields in the farm yet, but the freeway on ramp I take every afternoon I'd struggle to keep traction while accelerating with the Toyo's in the rain, today I floored it, in the rain with no issues. No noticeable changes in power from the larger foot print either. The only concern I have right now is that the truck seemed more floaty in the rear at high speed, but I was only on the highway for the last mile of the highway, so that's just not really a good test anyway. Tomorrow I'll have a much better highway run in the evening so I'll know then if this is an actual issue. I've never had this effect on other rigs that I've had grabbers on before so right now I'm thinking it might have just been in my head, and of course tires do have a short breakin period when they are new so it could have been that. so I will report back on that tomorrow night.

Assuming the highway drive tomorrow goes well I can only see positives in this change both going to a better allterrian tire, and a wider one.
 
Last edited:

idahovette

Full Access Member
Joined
Aug 7, 2016
Posts
7,270
Reaction score
15,874
Location
Weiser Idaho
First Name
Perry
Truck Year
1975-1979
Truck Model
K20-K10
Engine Size
350
@SirRobyn0 I thought you were going to 265/75R16, or am I confused as always???!!!
 

Forum statistics

Threads
44,167
Posts
950,747
Members
36,282
Latest member
Doug Hampton
Top