Which size tire?

[duckhunter55]

I currently have a 92 chevy short bed regular cab truck, with the 350 and z71 package. Currenlty i have 285-75-16 mud tires on the truck. These tires are about worn and looking at some all terrains. I was wondering what yall thought about the one size bigger tires im running, and/or if i should go back to stock tires? I really dont't pull anything heavy, just a 16ft. aluminum jon boat and an occasional trailer full of wood. I really like the looks of the bigger tires and someone suggested that if i keep the bigger tire to lower my gear ration. Does anybody have any info on this and would it help anything? thanks in advance

 

[SpinnerBait_Nut]

Re: Which size tire?

I have never seen the need for oversize tires myself.
A vehicle comes from the factory set up with the size tires it has on it.
Speedometer, fuel mileage, gear ratio, etc are all calculated for the tires they put on them.
Go to smaller tires, put more miles on it.
Like I said, I have never seen the need to do it.

 

[TilliamWe]

Re: Which size tire?

If they work for you, stay with the size you have. But the effect they have on your gear ratio is just the opposite of what was suggested. They actually make you overall gearing taller. Meaning if you have a 3.42 axle ratio, then with larger diameter tires, you effective ratio might be closer to a 3.23 ratio. Remember, a lower gear ratio has a higher number.

 

[Arima90]

Re: Which size tire?

How's she feel at highway speeds. Smaller tires sure do make it easier on the vehicle when towing or hauling heavy loads. Larger diameter tires (larger than stock) allow lower RPM's at speed, however, as I'm sure your aware, larger tires require more energy to move do to greater weight and diameter. Another thing to consider is the drive ratio in your rear end. Has it been changed from stock. If so, returning to stock size tires may raise RPM's up too high for comfortable highway speeds and fuel mileage be hurt at high RPM's.

I have a 94 3/4 Chevy 6.5 Diesel. I went from stock tires (245) to a 265 and noticed greater fuel consumption (poor mileage). I'll be returning to the smaller 245 after their worn out just because primary use of the truck is to tow and haul. I'll miss that stout look but fuel economy is priority in these times.

Hope this helps.

 

[Silvertip]

Re: Which size tire?

Most people fail to realize that the speedometer needs to be recalibrated if a tire of a different size is installed. If going bigger, the speedometer slows down so you may think you are only going 50 when you are actually going faster. Consequently, because the speedometer is slow, so is the odometer so "apparent" fuel economy heads south. In fact it may indeed decrease because it takes more throttle to maintain speed than before. So before you buy new tires, figure out what it is you want to achieve. With bigger tires you won't help economy, you will put extra strain on the drive line, and you will hurt acceleration. But they may look good!

 

[tashasdaddy]

Re: Which size tire?

you notice a difference in fuel comsuption, because the speedo is not geared for that sized tire. i had an old 60 GMC 1/2 ton, with BIG tires, for heavy hauling, far heavier than the vehicle was designed. speedo read 55, actually speed as 70mph. one trip to the dump the truck had 4500lbs in the 8 foot bed.

typing at same time.

 

[Gary H NC]

Re: Which size tire?

I believe that truck came out originally with 245's on it.You are already a size bigger.
On mine i wanted a little bigger tire so i went from 245-75's to 265-70's
They are wider but not much taller than the originals.

 

[steelespike]

Re: Which size tire?

How's she feel at highway speeds. Smaller tires sure do make it easier on the vehicle when towing or hauling heavy loads. Larger diameter tires (larger than stock) allow lower RPM's at speed, however, as I'm sure your aware, larger tires require more energy to move do to greater weight and diameter. Another thing to consider is the drive ratio in your rear end. Has it been changed from stock. If so, returning to stock size tires may raise RPM's up too high for comfortable highway speeds and fuel mileage be hurt at high RPM's.

I have a 94 3/4 Chevy 6.5 Diesel. I went from stock tires (245) to a 265 and noticed greater fuel consumption (poor mileage). I'll be returning to the smaller 245 after their worn out just because primary use of the truck is to tow and haul. I'll miss that stout look but fuel economy is priority in these times.

Hope this helps.

When changing to bigger tires did you allow for the fact that the odometer
will be slower thus less mileage accumulated between fill ups.
You can get an idea how far off by checking against the mile markers on the
highway.check several as markers do tend to vary.Probably will still be less mpg but probably not as severe as you thought.

 

[wire2]

Re: Which size tire?

You can increase tire width, drop to a slightly lower aspect ratio and the effect on mileage, speedo, gear ratio will be negligible. Here's a calculator to experiment with, remember to try to end up with the same tire O.D.
Not all tire width/aspect ratio combinations on the calc are available from dealers.

http://www.miata.net/garage/tirecalc.html

 

[GreenF350]

Re: Which size tire?

It really depends on the vehicle. Every vehicle I have put larger tires on has gained gas mileage (although some lost considerable power) the big thing is to remember the recalibrate the speedo/odometer. Regardless, for what you said you use your truck for, I doubt you would notice much of a difference, in power, or gas mileage for that little of a difference in size. (I didn't on my 95 K1500) It's not like my F350 I have now that I went from 35's to 37's. (Which BTW kept the same mileage around town and gained about 2 mpg on the highway). The 285's should be fine.
-Aaron

 

[Senderofan]

Re: Which size tire?

I went from the stock 245-16's to 265's on my '02 2500 HD. I don't believe I lost much at all in fuel mileage....but according to some online calculators...just changing the one size up changed the speedo by 3%. I compensated for this with my tuner...it has the capability to change the speedo according to tire size or change in gear ratio. I do know that guys with trucks like mine notice a decrease in fuel mileage when they get to the 285 or 315 sized tires.

Wayne

 

[Gary H NC]

Re: Which size tire?

I have the tuner that can set the speedo for tire size too.My stock 245-75's were 31.5 in diameter-height and the 265-70's were 31.7..It was too small of a difference to worry about.Pretty much the same height just a fatter tread pattern.They look better and ride better than the stock tires.It may just be i went from Firestones to Michelin.

 

[Senderofan]

Re: Which size tire?

I think my Michi's measured about an inch higher than the 245's. I think my 265's are still a 75 sidewall. It sure is nice to have the option of adjusting the speedo with the tuners!! Among other things.

Wayne

 

[KM2]

Re: Which size tire?

I don't think you can go any bigger without the tires rubbing. But I think you mean getting 285 tires again instead of stock. Everyone is right about the gearing and speedometer being effected by the tire size, but you are only going up a little bit. Those points are more valid when you are talking about lifting the truck up and putting 35inch and bigger tires.


Go big they do look better!

 

[Wide Open]

Re: Which size tire?

I believe that truck came out originally with 245's on it.You are already a size bigger.
On mine i wanted a little bigger tire so i went from 245-75's to 265-70's
They are wider but not much taller than the originals.

I thought the Z71's came with 265/75's. What does the tire label in the door jamb say? There is a pretty big difference between 245's and 285's but not as big a jump when considering 265's.

 

[duckhunter55]

Re: Which size tire?

Yea my truck came with 265-75-16 on it. I bought mud tires and had them put on about a month or so after i got the truck. And at that time i didn't have a boat or nothing to pull so i don't know if the bigger tires are making a difference or not. I probably get about 12-13 mpg in the city. just to fit these tires i had to cut a little off of the plastic thing below the bumper, but i think thats because of my wheels sticking out further than stock. thanks for all the info guys, i think i will go with 285's again.

 

[I Did It!!]

Re: Which size tire?

The main thing you have to remember is to keep the tire diameter the same or as close as possible!! If you have 75 series tires now, you can probably go to the larger width tires, but in a 70 series...etc. Conversly, a 265 x 70 series will be smaller(less tall) than a 265x75 tire....in other words, a 285x70 tire should be close to the same size as a 265x75...

 

[UncleWillie]

Re: Which size tire?

Easy To calculate.
http://www.miata.net/garage/tirecalc.html

R/m = Revolutions Per Mile

285/75-16 = 614 R/m Larger
285/70-16 = 636 R/m ^
265/75-16 = 637 R/m ^
275/70-16 = 647 R/m ^
265/70-16 = 659 R/m ^
285/65-16 = 659 R/m ^
245/75-16 = 662 R/m Smaller

 

[1979 Quartermasters]

Re: Which size tire?

I have a 95 GMC Seirra 4X4 extended cab and I went from 265/75 to 285/75 and notice a little loss in power, but not enough to regret doing it. I also put a 2 inch lift (torsion bar keys and a 2 inch block in the rear) and the truck went from a "socer mom" truck to a smart looking 4X4. I put Goodyear Wranglers and am very pleased with the ride and they stick very well in the snow and ice.



Ken

Just noticed this was an pretty old thread, although interesting reading.

 

[paultjohnson]

Re: Which size tire?

4 yr old thread guys...