285/65r18 no rub
My new KO2 285/65r18 (3 Viewers)
- Thread starter Rando Kuruza
- Start date
This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.
To show how much lighting effects a pic ...
Nose looks lower same spot and time for other side of truck.
Nose looks lower same spot and time for other side of truck.
gaijin
GOLD Star
What tire pressure are you running?
They weigh 58-60lbs each. Major increase in unsprung weight! Is your suspension stock? Can you feel the additional weight? Would like your impressions, even though I have a LX570 I am sure both suspensions are engineered to handle the same unsprung weight.
Last edited:
They are at 36psi in photo
Feels like oem springs are too soft for tires and the rebound ? is also too light. Always planned for old man emu upgrade as felt oem suspension was too soft with oem tires...new tires kinda exaggerate that feeling. Maybe power of suggestion but I think is true.
gaijin
GOLD Star
At that pressure the Load Limit is about 200 pounds per tire below the stock requirement. I'd highly recommend you increase your Cold Tire Pressure to 40psi to be safe.
HTH
So I think I see the logic in this recommendation. Load range around 3800 lbs at 80 psi. Stock around 2400 lbs at 40 psi. But if this is true it almost makes the "p" rated tires seem stronger? Or does this have to do with heat build up in the heavier tire at the lower psi. Could you enlighten us? I do know that increasing the psi in this "E" rated tire will make them ride as hard as a rock.
gaijin
GOLD Star
It's all about Load Limits.
The stock P-metric tires on our rigs - P285/60R18 - are spec'd @ 33psi Front/Rear by Toyota. This yields a Load Limit of 2,512 pounds per tire.
LT-rated tires (because they are "stronger," to your point) can do with a Load Limit 10% less than that, so 2,512/1.1=2,284 pounds per tire.
By looking up the Load Limit/Inflation charts published by the Tire and Rim Association, we find the LT285/65R18 tires in question have a Load Limit of 2,235 pounds per tire @ 40psi. This is a little less than the spec'd 2,284 pound Load Limit, but close enough.
Simply put, running the LT285/65 tires at less than 40psi would be like running the stock tires at less than 33psi - with the same potential bad results.
HTH
Why are the OEM tires on the LX570 rated at 2185 Lbs? And it weighs almost 300 lbs more then the LC?
gaijin
GOLD Star
What exactly is the P-metric tire size for the LX570? What exactly is the specified Cold Tire Inflation Pressure as stated on the door jamb?
I took that number off the MicHelin tire site for the OEM 285/50/20 tire. When I go to tire rack it show 24xx lbs?? Psi is 33. Is there a formula you use that you can share for weight of vehicle, tire lbs support, psi rating of tire for that load and what fewer Psi's do to the tire lbs holding ability. Sorry if I sound confused because I am
I took that number off the MicHelin tire site for the OEM 285/50/20 tire. When I go to tire rack it show 24xx lbs?? Psi is 33. Is there a formula you use that you can share for weight of vehicle, tire lbs support, psi rating of tire for that load and what fewer Psi's do to the tire lbs holding ability. Sorry if I sound confused because I am
Gaijin had an awesome post that I can't seem to locate. He helped me settle on 35psi. It's all about your particular vehicle laden weight, tire, and making adjustments from there. Sorry I can't find it.
gaijin
GOLD Star
I took that number off the MicHelin tire site for the OEM 285/50/20 tire. When I go to tire rack it show 24xx lbs?? Psi is 33. Is there a formula you use that you can share for weight of vehicle, tire lbs support, psi rating of tire for that load and what fewer Psi's do to the tire lbs holding ability. Sorry if I sound confused because I am
Let's take it one step at a time.
On your stock LX570, you had P285/50R20 tires, right?
On the sticker in the door jamb it specified 33psi Cold Tire Inflation Pressure Front/Rear for those tires, right?
Consulting the 2014 Yearbook published by the Tire and Rim Association (you can buy one here if you are interested: http://us-tra.org/publications.html), those tires at that pressure have a Load Limit of 2,315 pounds per tire. That is what Toyota feels comfortable with for those tires on that vehicle for all specifications like towing capacity, cargo capacity, etc.
P-metric tires and LT-metric tires have calculated Load Limits that are slightly different. If substituting an LT-metric tire for an original P-metric tire, the Load Limit can be 10% less for the LT-metric tire.
In this case, that means the 2,315 pound Load Limit of the OEM P285/50R20 tires divided by 1.1 (that's the 10% difference) yields an LT-metric Load Limit requirement of approximately 2,105 pounds to meet the OEM performance criteria.
Again, consulting the Yearbook from the Tire and Rim Association, one finds that for the LT285/65R18 tires, one needs approximately 37psi to reach the required Load Limit of 2,105 pounds for the LX570.
Why Toyota decided that a Load Limit of 2,315 pounds was good for the LX570, but 2,512 pounds was required for the LC200 is something you will have to ask Toyota.
So ... in conclusion:
If you are running LT285/65R18 tires on a LC200, you should run them at 40psi F/R.
If you are running LT285/65R18 tires on a LX570 (based on SWUtah's data), you should run them at 37psi F/R.
The only easy formula one could apply to all this is that the GAWR (Gross Axle Weight Rating) - found on the sticker on your door jamb - should not be more than 94% of the combined tire Load Limit for that axle.
So, in the case of my LC200:
We can see that the Rear Axle has a higher GAWR of 4,300 pounds. My LT285/70R17E tires have a Load Limit of 2,286 pounds @ 39.3psi. Since there are two tires per axle, 2 x 2286 = 4,572 pounds. 4,300 divided by 4,572 = 94% - right at the spec. The front axle is obviously more within the spec because when we divide 3,595 by 4,572 = 79% - well within the spec. You can do this calculation yourself and see whether it works for your LX570.
Clear as mud, right?
HTH
You have a gift
Let's take it one step at a time.
On your stock LX570, you had P285/50R20 tires, right?
On the sticker in the door jamb it specified 33psi Cold Tire Inflation Pressure Front/Rear for those tires, right?
Consulting the 2014 Yearbook published by the Tire and Rim Association (you can buy one here if you are interested: http://us-tra.org/publications.html), those tires at that pressure have a Load Limit of 2,315 pounds per tire. That is what Toyota feels comfortable with for those tires on that vehicle for all specifications like towing capacity, cargo capacity, etc.
P-metric tires and LT-metric tires have calculated Load Limits that are slightly different. If substituting an LT-metric tire for an original P-metric tire, the Load Limit can be 10% less for the LT-metric tire.
In this case, that means the 2,315 pound Load Limit of the OEM P285/50R20 tires divided by 1.1 (that's the 10% difference) yields an LT-metric Load Limit requirement of approximately 2,105 pounds to meet the OEM performance criteria.
Again, consulting the Yearbook from the Tire and Rim Association, one finds that for the LT285/65R18 tires, one needs approximately 37psi to reach the required Load Limit of 2,105 pounds for the LX570.
Why Toyota decided that a Load Limit of 2,315 pounds was good for the LX570, but 2,512 pounds was required for the LC200 is something you will have to ask Toyota.
So ... in conclusion:
If you are running LT285/65R18 tires on a LC200, you should run them at 40psi F/R.
If you are running LT285/65R18 tires on a LX570 (based on SWUtah's data), you should run them at 37psi F/R.
The only easy formula one could apply to all this is that the GAWR (Gross Axle Weight Rating) - found on the sticker on your door jamb - should not be more than 94% of the combined tire Load Limit for that axle.
So, in the case of my LC200:
We can see that the Rear Axle has a higher GAWR of 4,300 pounds. My LT285/70R17E tires have a Load Limit of 2,286 pounds @ 39.3psi. Since there are two tires per axle, 2 x 2286 = 4,572 pounds. 4,300 divided by 4,572 = 94% - right at the spec. The front axle is obviously more within the spec because when we divide 3,595 by 4,572 = 79% - well within the spec. You can do this calculation yourself and see whether it works for your LX570.
Clear as mud, right?
HTH
Great info. Thanks. Since you know this stuff what do you think the highest tire weight you can handle on a stock LX 570 and LC, without over stressing the suspension and creating a possible dangerous condition? The reason I ask is I see stock tires weighing around 40-41 Lbs. And people installing "E" rated tires weighing 60-65 lbs that's an additional 24 lbs of unsprung weight. Your thought on what that would do to the AHC on the LX 570?
gaijin
GOLD Star
All I know for sure is that Toyota specifically recommend the LT285/70R17E 121/118R BFG AT T/A KO tires on the 17x8x50 TRD wheels for use on the LC200. It states this clearly in the Technical Spec sheet that applies to the TRD wheels.
That specified tire weighs 59 lbs according to TireRack: http://www.tirerack.com/tires/tires...AKORWLV2&vehicleSearch=false&fromCompare1=yes That's 17 lbs heavier than my LC200 stock tire which weighs 42 lbs.
Thus I can only conclude that that specific 59 lb tire would not cause any problems on the Land Cruiser.
I have seen no equivalent recommendations from Toyota for the LX570.
I have no idea what effect that BFG tire/TRD wheel combo would have on the AHC system on the LX570.
Obviously, even absent any specific data or recommendations from Toyota, we can safely assume that the laws of physics apply. Any larger/heavier than stock tire will result in:
- Slower acceleration
- Worse gas mileage
- Increased braking distance
- Less responsive suspension
- Increased wear on suspension components
All due simply to the fact that there would be more unsprung weight.
When it is that a tire/wheel combo becomes too large, or too heavy, depends on what one is willing to accept in trade-offs.
HTH
Thanks good info. It's that wear on the AHC that I think I would be concerned with
- Thread starter
- #39
always good info!
MScruiser
obsessive-compulsive oppositional-defiant wise-ass
Gaijin,
You are gifted. You should be in the circus, right next to the ape-man, and the weight guessers.
You are gifted. You should be in the circus, right next to the ape-man, and the weight guessers.
