[vanib]

I can see from your profile that you a 4WD. Ideally, I would replace all 4 if only 10K miles are left.

Have you checked a used tire place; they might have exactly what you need regarding size, maybe even brand. You would need to measure the circumference of one of your tires using a string and compare.

You could also buy one tire and have it shaved to match if have a tight budget.

On the other hand, I would like to know the circumference of the new tires compared to the 2 tires that you were planning to keep. I believe it is ok to have a 5% difference in circumference for the RAV4 4WD system to operate. Otherwise, it is automatically disabled.

 

[BugJr]

... snipped ... Ideally, I would replace all 4 if only 10K miles are left.

+1 with vanib. You're close to replacement mileage so I'd go ahead and replace all four. However, I'd keep the 3 used ones and put them up on Craig's List or equivalent for maybe $20 a piece ... negotiable down to $12 - $15 per tire.

That's what I usually do when I replace my tires and I`ve always been able to find a buyer. | BugJR |

 

[Dr. Dyno]

I pretty much agree with vanib.
I definitely wouldn't replace one or two with new tires since the others are close to gone. One puts undue stress on the differential on that end of the car since it's effectively going around a corner all the time. Two new would probably defeat the 4WD system since the max circumference differential it can function with is 3%. A used tire of the same size & brand would work best mechanically but with winter coming changing all four makes the most safety sense. If you lived in the Boston area last winter you get the picture in black and WHITE!

 

[rav4system]

Replace all 4 for sure...

 

[DVS]

Replace all 4 for sure...

Agreed, especially with winter coming, where deeper treads will be particularly beneficial in the snow.

.

 

[ravfourguy]

I would also replace all 4 tires. Besides, there are affordable tires out there.

 

[Dr. Dyno]

Looks like we may never know what marlenecook decided. May be another 1 and done member. Last activity = 9-30-15.

 

[Parkland]

I imagine this discussion has been around the block more than once. Based on Toyota's 2009 RAV4 4 wheel drive system, can anyone tell me where I can find Toyota's official max recommended allowable tire size difference? Not just when the system stops working but when the difference is causing unacceptable wear. Also Toyota's recommendation as to whether all 4 tires have to be within that limit or whether another replacement combination would be acceptable.

There seems to be all manor of opinions out there and tire shops are going to want to sell you tires. Nothing is mentioned in the Owners Manual, though I would think it should be.

I would like to know Toyota's opinion. You learn nothing at Toyota.ca other than contact your dealer, who is not likely going to be there when you need them.

Thanks, D

 

[Dr. Dyno]

Since the 4WD system won't engage the rear wheels with more than 3% difference front to rear there'd only be extra wear if the difference was under that.

 

[Parkland]

So I understand Dr. Do you know what that 3% is referring to? Tread depth? Doesn't sound like much. 30% would make more sense to me I am getting confused. However I did some calc for interest. I have about 42000km (26,000miles) on 4 directional winter tires which I rotate front to back once a year. Remaining tread depth is about .2345" (abt 8/32") average (well within normal operating parameters). A new tire would have about .3438" (11/32") of tread depth. By the way my tire tread is about 70% of a new tire. According to my calculations, and I am no mathematician, my old tire would rotate 5 more times a mile than a new replacement. Is that too much? Should I replace the adjacent pair or maybe even all 4? Incidentally I read that a tire can be operated safely at 6/32 (0.1875"). That would mean that an old tire would rotate 10 times a mile more than a new replacement. When does significant damage start to occur on the drive train? Then you consider the proper operation of the drive system as you mentioned. When does wheel circumference difference start adversely affecting the operation of Toyotas 4* system? Maybe not much if it is in front wheel drive most of the time. I would like to know a little more about it. I am not comfortable counting on a tire shop to fully appreciate my vehicles requirements. A Toyota Dealer may not be available. Thanks D

 

[mlockhart]

I don't like spending more money than I have to but some of the replies to this question amaze me. Used tires? Buy one new and have it shaved?? This guy was planning on keeping the RAV for another 2-3 years so he should have replaced all tires with brand new skins. Think about it-a patch of rubber compound roughly 4x6" is the only thing keeping the vehicle on the road in a variety of situations and weather and people want to skimp? How about buying used brakes? Crazy!

 

[DVS]

So I understand Dr. Do you know what that 3% is referring to?

My understanding is that it's a 3% difference in the outer circumference of the rubber.

.

 

[Parkland]

No argument from me. As bike rider I appreciate the importance of good rubber. But I would like enough legit info to make an informed tire replacement decision. I find it strange there isn't more guidance from Toyota on-line or in the manual?

 

[Parkland]

DVS, that would make sense. I will have to check it out. Thanks D

 

[Dr. Dyno]

The 3% is in circumference which = 3% in diameter = 3% in radius. But how does the 4WD ECU measure that? I must be a 3% difference in front vs. rear wheel speed. What's interesting is that above the 3% the ECU won't engage the rear drive, but the relative slip must quite a bit more under conditions where 4WD is needed, and it does engage.

Anyway using your tread depth numbers Parkland, and assuming the four tires are matched in brand and size, lets figure the percent new vs. worn vs. bald tires gives. Figuring a radius of 14" a change of 3/32" (11/32-8/32) would be .09375/14 or .67%, new to safe minimum is 5/32 (11/32-6/32) = 1.12%, and new to bald is 11/32 = 2.46%.

Conclusion: Even with new tires on one axle and bald ones on the other, a totally unrealistic condition, 4WD would still engage. A normal difference of a few 32nds as tires wear would be less than .5% difference and totally inconsequential. In fact just low pressure in one tire could possible change the percent more.

The above figures and the fact that the system operates in FWD most of the time is likely why Toyota doesn't mention it. It's a non-issue.

 

[Parkland]

Well Dr. you have me thinking now. I was thinking in terms of percent of tread depth difference. Not a percentage of the entire wheel radius distance. Funny how you get stuck on a train of thought. Assuming you are right I agree that replacing a bald tire with new would not appear to ever be an issue in terms of ECU engagement. I still wonder whats going on with the transfer case slippage side to side or front to back while the ECU is engaged or in front drive mode. I will have to give it some more thought. Thanks for your input.. I'm a little slow. D

 

[BugJr]

Call around to your local used tire dealers ... there are usually lots of them including new tire dealers who have replacement used tires for masny reasons.

See if they have an exact match for brand and size for a good used tire with sufficient tread remaining. Buy it, mount it drive it and be happy.

 

[Dr. Dyno]

I don't like spending more money than I have to but some of the replies to this question amaze me. Used tires? Buy one new and have it shaved?? This guy was planning on keeping the RAV for another 2-3 years so he should have replaced all tires with brand new skins. Think about it-a patch of rubber compound roughly 4x6" is the only thing keeping the vehicle on the road in a variety of situations and weather and people want to skimp? How about buying used brakes? Crazy!

Agreed and hopefully that's what the OP (Marlene) did. But that was from 2015 so the 2-3 years is about up and we never did hear what she did.

Some of the reason for the current discussion probably comes from common thought for most other brand full time AWD cars such as Subaru that use a viscous coupling which will wear continuously with different circumference tires and therefore require changing all four tires when one gets ruined. (I know. I had a Forester.)
Parkland is wondering why Toyota doesn't even mention similar guidance. Answer: Toyota's 4WD system is superior in that there is no continuous wear on anything under the same circumstances. So, no problem, no mention.

 

[ravverdriver]

Any AWD or 4WD system needs to be mated with tires at similar tread depths or it can mess with the differentials and cause damage. By your description all four is the recommended. Granted, the RAV tends to pull more from the front two tires, combining them with near exhausted tread life tires on thr rear would not be good. No dealer should recommend this unless you're in an absolute pinch. That's why its important to note that trucks and SUV's are not just more expensive in gas but also maintenance costs.