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Discussion Starter #22
Well I have one pair of chains and I’m going in to temps bellow 35°F. I’ll report back to let you know how my Coopers do! They have the 3PMSF symbol and I’ve seen videos of guys with wider tires than mine absolutely destroy in the snow and ice with their Dusters and 4.2 Ravs. But we shall wait and see. Thanks for the detailed advice and info. Always appreciated.
Have fun and be safe, I have fond memories of living in Bay area and exploring all over in my crx as a poor college kid:=)
 

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Discussion Starter #23
In regards to your RAV, I don’t think you’ll find much use for chains. If my past experiences with KO2s are any indicator, you’re going to scoot right along in severe winter weather. A snatch strap or tow rope could come in handy pulling others out of the ditch though 🤔

I should emphasis it‘s not merely the KO2s that are going to work so well for you, but the benefit of narrower tires as well.

Winter traction is about mitigating the effects of hydroplaning right down to the micro level. In the ’60s NASA developed a formula for calculating hydroplaning of aircraft wheels: 9(tire pressure). The NHTSA has revised it slightly in recent years to accommodate the greater diversity of automobile tires, something closer to 10.35(tire pressure). As a narrower tire has a smaller air chamber than does a fatter tire of the same diameter, narrower profile tires come typically specified for a commensurately higher air pressure to carry the same vehicle weight. My Nokians for example are specified for 32-50psi, I run them at 41. What this means is my RAV doesn’t experience hydroplaning until a whopping 66 mph, whereas a RAV4.2 equipped with 235s and Toyota’s recommended 29psi has lost control at just 55 mph at a water depth of 1/10”.

But severe winter driving introduces even greater threatening forces than just liquid H2O; slush and ice. But each of these is still fundamentally a water problem, in that the tire needs to evacuate a non-compressible medium as quickly as possible.

With slush, the tires have to evacuate a greater volume of water because water expands as it freezes. It also becomes more viscous, about x8 more so below freezing than typical summer temps. A smaller contact patch for a given vehicle weight motivates slush to egress the tire’s foot print with greater force. For a 225 that's about 25% greater force than a 235 series tire.

And finally, this 25% greater lbs/sq-in is where a 225 will hook up on ice when a 235 simply won’t. When the sipes have done their job directing water into the tread void or out of the footprint altogether, all you have left is the tread face and how hard your vehicle is pressing it onto the ice. The 3PMSF symbol guarantees your rubber compound will remain pliable enough in sub-freezing temperatures to conform to micro-surface features of the ice.

All this to say that’s why chains are a waste of money for you Mastee, but might be a good idea for Mistermike ;)

Interesting thing to note: a 215 series tire would be better still for winter driving for RAV4.2s, but many of us have conceded this benefit to run a single tire year round.



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That is quiet the research on the subject, I am impressed and happy to learn. Seattle area is not bad usually but as soon as we head a bit east into the mountains or south to Portland/California I think sometimes they are mandatory, so I am not sure if we will have a choice.

Thinking about ordering a curt class III hitch to be able to use an aluminum basket or a bike rack (no towing) since I will be taking the cross bars off. I will skip the trailer wiring or scavenge it off our matrix (it has never hooked anything and probably never will before I sell it), I haven't checked but I hope the tail sockets are same
 

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That is quiet the research on the subject, I am impressed and happy to learn. Seattle area is not bad usually but as soon as we head a bit east into the mountains or south to Portland/California I think sometimes they are mandatory, so I am not sure if we will have a choice.

Thinking about ordering a curt class III hitch to be able to use an aluminum basket or a bike rack (no towing) since I will be taking the cross bars off. I will skip the trailer wiring or scavenge it off our matrix (it has never hooked anything and probably never will before I sell it), I haven't checked but I hope the tail sockets are same
Yah the chain requirements up here are a little confusing. It says chains are required as we’re making our way up to mammoth but other signs say snow tires and 4wd are ok. I saw a bunch of Subaru’s kept on going so I decided to follow and see how it went. Roads are completely snowed/iced over getting in to town with temps right now around 10°f. Tires and the Rav’s 4wd have been really impressive so far. No sliding, great grip, and breaking have been great. Will upload a vid later this weekend. So far so good🤙🏼
 

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Washington chain laws: https://www.wsdot.com/winter/tires-chains.htm
California chain laws: https://dot.ca.gov/travel/winter-driving-tips/chain-controls

There exists some woefully dated material in either State’s language regarding snow tires or traction devices;
1) All-Season tires are extraordinarily inadequate for winter driving in the West.
2) Tires labeled M+S are only MARGINALLY better than All-Seasons, but still poorly suited for the job.
WA and CA recognize the above as adequate winter traction tires. This today is certifiably cooky-dooks, absolute non-sense and a total inability to keep up with modern technology.
3) 3PMSF rated tires should be the MINIMUM requirement for driving on snow and ice.
4) A dedicated snow tire is still leagues ahead of an All-Terrain tire labeled 3PMSF.

I used Toyo ATII AWs for awhile on my FWD Escape. If you don’t know that’s an All-Terrain tire rated M+S and 3PMSF. It met German requirements for a snow tire and I had to chain up to negotiate the worst mountain passes. Second winter I switched to dedicated winter tires. That year was the worst winter in Europe in 70 years and my chains were never unpacked! We had a phenomenal winter that year my wife and I, traveled a great deal more on much worse roads and passes because the Escape plowed through the snow and ice like a tractor.

Bottom line: You‘ll have absolutely no reason to ever put chains on your 4WD RAV with appropriately sized WINTER TIRES. Running All-Terrains with at least the 3PMSF should see you through most of the muck . . . but mileage will vary provided tire models and sizes. Using anything less during winter driving is dangerous and I would anticipate using chains frequently.
 

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Washington chain laws: https://www.wsdot.com/winter/tires-chains.htm
California chain laws: https://dot.ca.gov/travel/winter-driving-tips/chain-controls

There exists some woefully dated material in either State’s language regarding snow tires or traction devices;
1) All-Season tires are extraordinarily inadequate for winter driving in the West.
2) Tires labeled M+S are only MARGINALLY better than All-Seasons, but still poorly suited for the job.
WA and CA recognize the above as adequate winter traction tires. This today is certifiably cooky-dooks, absolute non-sense and a total inability to keep up with modern technology.
3) 3PMSF rated tires should be the MINIMUM requirement for driving on snow and ice.
4) A dedicated snow tire is still leagues ahead of an All-Terrain tire labeled 3PMSF.

I used Toyo ATII AWs for awhile on my FWD Escape. If you don’t know that’s an All-Terrain tire rated M+S and 3PMSF. It met German requirements for a snow tire and I had to chain up to negotiate the worst mountain passes. Second winter I switched to dedicated winter tires. That year was the worst winter in Europe in 70 years and my chains were never unpacked! We had a phenomenal winter that year my wife and I, traveled a great deal more on much worse roads and passes because the Escape plowed through the snow and ice like a tractor.

Bottom line: You‘ll have absolutely no reason to ever put chains on your 4WD RAV with appropriately sized WINTER TIRES. Running All-Terrains with at least the 3PMSF should see you through most of the muck . . . but mileage will vary provided tire models and sizes. Using anything less during winter driving is dangerous and I would anticipate using chains frequently.
Yes i agree with you and totally appreciate your experience and knowledge. For my situation right now my Cooper AT3 4s 3PMSF tires has definitely got me through the muck which i am actually surprised. I was just worried about my my tires being too wide like you said earlier. But if I was living in this weather on a daily basis or traveling in this for a long period of time, I would definitely invest in dedicated winter tire. All that being said, the 4wd system is legit. I was skeptical at first, but after this drive through the mountains with heavy snow and ice I am thoroughly impressed.
 

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I was just worried about my my tires being too wide like you said earlier.
I don’t mean to cause anyone to doubt their capabilities, I‘m just trying to explain the limitations of tires at their extreme winter envelope.

I just rented a 2019 RAV4 and drove it through light snow and ice with OEM All-Seasons and we survived. It was neither fun nor confidence inspiring, but we carefully made it. You’ll do fine with the AT3 4S in 235/70.
 

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Hey all just found some time to upload this quick video of the Rav doing a little off-roading with the Cooper AT3 4s tires. The video always makes the hills look flatter than what they really are irl for some reason. There were quite a few ruts and steep inclines with snow and loose sand/dirt. Although I should have aired down the tires to go up these hills, we were only making a quick stop through the Alabama Hills and the dirt roads were manageable with normal air pressure. Tire pressure in this video is at 38psi.

 

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The video always makes the hills look flatter than what they really are irl for some reason.
I agree.... each time I look at my videos, I think the same thing.

Why do you run so high tire pressure? They will wear unevently. The recommanded pressure for a RAV4.2 is 29 psi... this seems a bit low, but 30-32 psi should be perfect.
 

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The recommanded pressure for a RAV4.2 is 29 psi.
I caution owners of RAV4.2s to run Toyota's recommended air pressure. It's expected of you when running OEM tires, but Toyota has no legal expectation or blanket knowledge of all aftermarket tires, especially in plus sizes.
It is however required by law that the tire manufacturer print these specifications on the sidewall. So in no fewer than four places on your RAV does it say specifically for your tire and GVWR what tire pressure you should use.
Also remember, the penalty of too much pressure is uneven wear. The penalty of too little pressure is not only excessive wear, but sudden loss of control due to spontaneous delamination.
I use a Viair portable compressor in order to air down for off-roading (I use 20 psi) and air back up to regular pressures when finished. This does require me to reset the TPMS each time.
38 psi does sound handily on the firm side for a 235/70 of this vehicle's weight. If it's a standard load tire, meaning a P235, I wouldn't be surprised if the specified pressure was <29 psi for a sub 3,000 lbs SUV.
 

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To clarify, I’m not saying Toyota doesn’t know how much air should be in their tires to carry them down the road. Following the placard information is good advice.

I am trying to heed caution to those running all-terrains in XL or even LT loads, especially in alternate sizes. Toyota spec’d these with Goodyear all-seasons @ 29 psi, a more serious off-road tire will almost certainly differ. A passenger car tire might be rated at 1,000 lbs @ 35 psi whereas a BFG KO2 could be 1,150 @ 32 psi. I encourage others to share as an example, and we might even be able to build a spread sheet.

To optimize performance and continue to meet Toyota’s design load limit, know the weight of your vehicle, divide by four, find the nearest weight labeled on your tire and extrapolate the required psi.

 

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I observed that most manufacturers tend to put the tire pressure higher and higher (up to 40 PSI) since about 10-15 years. Even a small compact car that the recommanded tire pressure was 28 PSI 15 years ago is now at 33-35 PSI. I'm pretty sure that this is mainly due to get the better MPG possible.

I personnally keep my RAV4 tires at 30 PSI. When I was going off-road, I sometimes aired down to about 20 PSI. Two years ago, I was checking my tire pressure and was very surprised that one of my K02 was at only 4 PSI, and that it was not very apparent when the vehicle was sitting normally on the pavement! I did'nt know for how many days I was driving like this. So now I'm not afraid to air down as low as 10 PSI when a do a more ''technical'' off-road trip with my friends. Much better grip over the obstacles... the difference is impressive.
 

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I observed that most manufacturers tend to put the tire pressure higher and higher (up to 40 PSI) since about 10-15 years. Even a small compact car that the recommanded tire pressure was 28 PSI 15 years ago is now at 33-35 PSI.
This is because automobiles are getting bloated and fat. As a nuematic tire, higher pressures are required to carry the additional weight of the vehicle. The additional air doesn't require a corresponding weight penalty. Better fuel economy is achieved by thinner sidewalls and better construction materials.
This is also why our door sticker is becoming increasingly more irrelevant.
 

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Thanks guys I actually had no idea about the recommended psi being 29. My tires are indeed p235. I do check my pressure at last once a week and I’ll air them down today for sure. This has been my issue actually, no knowing exactly what pressure I should be running on my specific tires. I do know that my sidewalls are not nearly as durable as the KO2 so I’ve been cautious airing down anything below 25.
 
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