More tire questions

The 31x10.50R15 are Light Truck Tires. The P265/75R15 are Passenger Car Tires used on a light truck. The Light Truck (LT) Tires have a thicker carcass and require higher pressures for a given load to reduce flexing and prevent heat build-up. The maximum load carrying capacity and maximum inflation pressure of Light Truck Tires is determined by the load range (C, D, E, etc.). P metric tires for a given size all have the same maximum load (but not necessarily the same maximum pressure - extra load tires have higher maximum inflation pressures, but the same maximum load).

A standard load P265/75R15 tire has a maximum inflation pressure of 35 psi. The maximum load at this pressure is 2365 lb. when used in light truck applications (this will not match the maximum load of 2601 lb listed on the side wall - P series tires are derated when used on light trucks). The overall diameter of this size tire should be approximately

31.7"

A 31x10.50R15, Load Range C Tire is rated to carry 2250 lb when inflated to 50 psi. The overall diameter of this tire is 30.7".

So if you substitute the LT tires for the P series tires, your speedometer should read higher than the actual speed (62 indicated at an actual 60). The LT tires also require much higher inflation pressures. This combined with the stiffer carcass will result in a much stiffer ride. You should also expect the gas mileage to suffer slightly because of the heavier tires.

Ed

All this info is making my head spin.

I'm still no closer to finding something to put on my truck to replace the factory Firestone Wilderness AT II tires.

I'm looking for something that's quieter than those factory tires. I cannot find P265s anywhere that don't have those huge "mudgrip' treads.

I can't really find any info that tells me how easy it would be to readjust the speedometer if I opt for P225s, which is what is listed on the door plate of the truck and in every place where I'm asked to give my truck model and provided a list of recommendations.

And I don't want to spend a fortune ;-) and would love to buy at Wal-Mart or Sam's Club where lifetime balance and rotation applies, as well as a good road hazard warranty.

+++++++++++++++++++++++++ H.B. Elkins -- Beattyville, KY hbelkins(at)mis.net "There's no doubt he's the best race driver in the world."

--Dale Jarrett, on the late Dale Earnhardt

Go Big Blue (Kentucky Wildcats)! Go #15 (Michael Waltrip, NAPA Chevy)!

To reply, just remove the restrictorplates...

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Holy jeebers, would you please just make up your mind!

Speedo calibration is probably electronic, which would most likely mean a trip to the shop and a little trial and error unless they have some presets built into the speedo circuits to account for different tire sizes that are installed in the factory. Come to think of it, that makes sense because the don't want to have to manually calibrate all of those vehicles as they roll off the line.

Why not call the dealer and ask a technician? Or why not ask the question in a new thread---there's a Toyota Tech that reads this newsgroup pretty frequently.

I'll send you an email with the name of my friend and you can call him if you want.

If you have access to a GPS unit, you can check your speedo. You need a straight section of highway. Drive at constant speed, say 60mph, and see what the GPS says. Or you can use the GPS as a speedo and see what your speedo says. I did this for various speeds and made a little chart. After a couple of days of driving I didn't need the chart. You really should have a buddy along to run the GPS so you can pay attention to the road.

Bearman

Yokohama Geolandar HT tires are very nice all-weather, quiet, and not so pricey....

According to the 2000 edition of the Tire Guide, your truck should have had P225/75R15 tires unless it had the Value Edition Package, in which case it would have had the P265/75R15 Tires.

The difference in tire diameter is not minor:

A P225/75R15 Tire will have a diameter of approximately 28.29 inches. A P265/75R15 Tire will have a diameter of approximately 30.65 inches.

Assuming the speedometer was correct when reading 60mph with the P265/75R15 tires, then you will actually be going only 55 at an indicated 60 if you change to the P225/75R15 Tires. Your dealer should be able to tell you how difficult it is to recalibrate the speedometer. If all else fails see

. If you are looking for quieter tires in a given size, go to and search on the tire size. See Rack lists 13 tires for the P265/75R15 size. Several of these havehighway tread. Of the 122, I personally would choose the Dunlop RadialRover A/T or the Yokohama Geolandar H/T-S G051. Since the P225/75R15 Tires were available on your vehicle, it is probably OK to change to this size. However, this size tire has a significantly lower maximum load rating (1874 lb for the 225s vs 2469 for the 265s). Persoanlly I would not make the switch to the smaller tires.

Ed

I have an 03 extcab Taco. It came with P225 tires. I had them taken off within 24hrs of getting the truck and put on the TRD wheels with BFG AT's, LT265's. I recently discovered the exact amount my speedo is off...I got a GPS for Christmas and was able to compare. When speedo says 110kph, my GPS says 112.5-113kph. I am figuring that after going 100kms, I've actually gone

112.5kms.

Its not much of a difference to me to want to adjust the speedo. Some vehicles are off by that much anyway.

Yes, it came with the P265 Wilderness AT II tires, and it came with all the power stuff so I figure it's the Value Edition Package (I can't find my sticker).

Sounds like they're similar in size, then to a 31x10.50R15. I've found a Michelin X Radial that looks like it would have a quiet ride.

+++++++++++++++++++++++++ H.B. Elkins -- Beattyville, KY hbelkins(at)mis.net "There's no doubt he's the best race driver in the world."

--Dale Jarrett, on the late Dale Earnhardt

Go Big Blue (Kentucky Wildcats)! Go #15 (Michael Waltrip, NAPA Chevy)!

To reply, just remove the restrictorplates...

++++++++++++++++++++++++++