PDA

View Full Version : Replacing tires on all-wheel drive vehicle



Don Morris
11-25-2013, 9:05 PM
We bought a 2012 MDX last year. LOML has always liked their styling and our son has one and it has been "bullet proof" for years. We've put a lot of miles on it this year and for the first time LOML hasn't had a bad back and forth going from DC to Chicago. At any rate, took it in for an oil change to our trusted mechanics who consistently get the highest rating in Washintonian Magazine. We have 14,000 miles on the tires and one of them took a nail in it at an angle which means driving on it is not a good idea. The question is: replacing tires on all-wheel drive vehicles. I've heard two different versions: you need to replace all four, or you need to replace just the partner of the one being replaced. At $300.00 a tire, the answer could be financially significant.

Duane Meadows
11-25-2013, 9:16 PM
Some of the older 4 wheel drives locked all for wheels together when in 4WD. Then it was pretty much necessary to change all four at the same time. Even taking a corner on drive pavement would make on or two skid!

With modern AWD should not be an issue change only 2 on the same axle. Probably can get buy with one, but I'd do the pair.

Wade Lippman
11-25-2013, 9:23 PM
Sadly it is all 4. If they are not all the same diameter the car thinks they are slipping and tries to correct for it. 14,000 milesis probably too much wear to call even. It is possible to grind the new tire down to match the old ones, but I haven't tried that.
You might consider using cheaper tires.

Ken Fitzgerald
11-25-2013, 9:29 PM
If you are going to replace them, personally I'd replace all 4 of them.

Talk with the dealer and get 2nd opinion.

Our winters here in Idaho can be somewhat "interesting" from a snow and ice perspective. I don't want any chance that differences in traction or diameter will play a part in the vehicle's operation in bad weather driving conditions.

Bob Coleman
11-25-2013, 9:34 PM
You may have a road hazard warranty on the tires which will allow you to get the new tires pro-rated. At least I think thats how it works. I would definitely check.

Also - sorry, you need four tires unless you're willing to take a risk on shaving down the new one.

Take a look at tirerack.com (no affiliation, just a happy customer) for the replacements, should be able to get a better deal than a dealership.

Phil Thien
11-25-2013, 10:38 PM
Get one new tire, have it shaved.

Edit: Here, read this: http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=18

Alan Lightstone
11-25-2013, 11:37 PM
I'm confused. Lamborghinis come with 19" tires in front, and 20" tires in back, and their AWD doesn't seem to have handling issues at 210mph. 1" tire size difference is quite a bit more than the fractional tire size difference you're talking about.

Phil Thien
11-25-2013, 11:43 PM
I'm confused. Lamborghinis come with 19" tires in front, and 20" tires in back, and their AWD doesn't seem to have handling issues at 210mph. 1" tire size difference is quite a bit more than the fractional tire size difference you're talking about.

But the gearing accommodates the difference in tire circumference.

Stephen Cherry
11-26-2013, 12:34 AM
If it were me, I would just get one tar from tire rack, and not think about it any more. What happens if you get a flat and need to put on the spare? Will that tire be perfectly matched with the others? How about if one tire is a little low on air while another is a little high, thereby changing the effective radius- does that introduce a dangerous condition? How about going around a turn, where each of the tires has a different path, and number or rovolutions through the the turn- does the car spin out? Just my guess, but I'm thinking that the cars 4wd system can and does take care of differences in tire characteristics and paths because if it did not, it would be jumping around in every turn. I had a 90's toyota fj80 landcruiser that was full time 4wd, and it had differentials to take care of all of this, and the accura would be advanced from that car by a couple of generations.

Jim Matthews
11-26-2013, 7:04 AM
This is an opportunity for you to make a gesture to SWMBO - "Honey, your safety and peace of mind are priceless to me."

One icy patch, one idiot out of control, one deer across the road that a good set of tires avoids is worth the price of admission.
The MDX sits up pretty high and is built for comfort first, mobility second.

I would go further, and get decent snow tires on steel rims.
I think this will be a rough Winter, near the Atlantic ocean.

Jerome Stanek
11-26-2013, 7:51 AM
I worked for a tire company for a while and all tires are just a little different in size. Just get a new one and be done with it.

Greg R Bradley
11-26-2013, 10:51 AM
You can't just make generalizations based upon it being 4 wheel drive. There are many systems, even different variations that Acura has used on the MDX. You need to talk to someone that knows that system and its requirements.

However, a couple questions based upon the partially similar system in my 4wd Honda:

How much wear is there on the tires? There was minimal wear on the Michelin LTX M/S tires on mine at 14k miles. The first set lasted 53k and I have about 15k more on the second set. If your MDX has similar tires with a UTQG of 440 or so, I'm expecting a loss of 1/8" in diameter. If so, that makes it more likely that replacing one is a good option, particularly if the slightly different sizes are initially put on the rear.

Do you know which 4wd system is on that vehicle? There are several versions of Honda/Acura 4wd and more than one could be available on a single vehicle in one model year as options. I do know the latest SH-AWD system is a very sophisticated variable torque split system that continuously varies torque to each tire. For example, it adds torque to the outside rear tire during cornering to reduce understeer. It is likely to be able to accomodate slightly different tire diameters as it is constantly monitoring and adjusting parameters.

Is this mechanic a Honda/Acura specialist? If not, you need to find someone that is and ask them these questions. There is no way that any one person can be competent on a variety of late model cars.

Ken Fitzgerald
11-26-2013, 11:01 AM
I'm confused. Lamborghinis come with 19" tires in front, and 20" tires in back, and their AWD doesn't seem to have handling issues at 210mph. 1" tire size difference is quite a bit more than the fractional tire size difference you're talking about.

Alan.... The Lamborghinis are designed for that 1" difference. Diameter makes a difference and has to be taken into consideration. Want to bet what would happen with the Lamborghini if you placed the 20" tire on the front and the 19" tire on the back?

Whether or not the difference between a new tire and a used tire on this vehicle would make difference? I don't know. I only know what I would be comfortable doing. First I would talk to a dealer's trained mechanic and get his opinion before making a decision.

Grant Wilkinson
11-26-2013, 11:19 AM
I had the same issue with my 2009 MDX. The dealer recommended installing 2 new tires - replacing the bad one and putting a new matching one on the other side. I've had no issues in the year of driving since then.

Art Mann
11-26-2013, 11:24 AM
Before you spend money on a whole new set of tires, you should talk to someone who is actually familiar with the design of the drivetrain. I don't know about Acuras, but none of the recent Dodge or Chrysler all-wheel-drive systems would be adversely affected by installing a single new tire with three older ones. I know because I worked on the design of their electronic drivetrain control system for a while. I can't imagine that Acura would have a less sophisticated system than Chrysler.

Wade Lippman
11-26-2013, 1:30 PM
Before you spend money on a whole new set of tires, you should talk to someone who is actually familiar with the design of the drivetrain. I don't know about Acuras, but none of the recent Dodge or Chrysler all-wheel-drive systems would be adversely affected by installing a single new tire with three older ones. I know because I worked on the design of their electronic drivetrain control system for a while. I can't imagine that Acura would have a less sophisticated system than Chrysler.
It probably ha a more sophisticated system that requires the tires to be the same. I know my toyota and subaru do.
Op... whats it say in the manual?!

Art Mann
11-26-2013, 5:42 PM
Are you saying the size listed on the sidewall has to be the same or the tires have to be exactly the same diameter? Read Stephen Cherry' post above. He has some valid points.

I think that when people hear the term "all wheel drive", they imagine that the drivetrain works like a simple truck four wheel drive, in which the front and rear drive shafts are linked together by a gear transfer case. That is absolutely not the case. All four tires can be rotating at different speeds without damage on the AWD systems of which I am aware.

There is no reason for the original poster not to consult a mechanic at the Acura dealership. That is my recommendation. Mechanics at after market oil change places, such as the OP consulted, can't be that well informed on all vehicles drivetrains.

Just as a post script, I used to have a 4WD Dodge Dakota. It had a gear differential but provided a full time 4WD mode of operation for highway speeds which I used fairly often. It came with a full size spare and I did a 5 tire rotation every 5000 miles, as described in the owner's manual. I never had any tire or transmission problems mixing tires of different wear conditions. When I sold it, it had over 100,000 miles on it.

Wade Lippman
11-26-2013, 6:50 PM
Are you saying the size listed on the sidewall has to be the same or the tires have to be exactly the same diameter? Read Stephen Cherry' post above. He has some valid points.


I am not saying one darned thing. I am just passing on Acura's advice.

It is best to replace all four tires at
the same time. If that is not possible
or necessary, replace the two front
tires or two rear tires as a pair.
Replacing just one tire can seriously
affect your vehicle's handling

Art Mann
11-26-2013, 7:08 PM
If you will read my posts, you will see that the only knowledge I claimed was about Chrysler products. I advised the OP to check with the Acura mechanic.

Ken Fitzgerald
11-26-2013, 7:38 PM
Folks,

Let's keep it civil.

Please.

Art Mann
11-26-2013, 11:57 PM
Wade just sent me a private message that would not be regarded by anyone as civil. I hope my reply was more civil than his. I will repeat it here.

My previous comments were an attempt to answer the question of whether the drivetrain would be damaged by mixing new tires with those that have 12,000 mile on them. My answer was no and I have quite a bit of experience to back that up. However, safety is also an issue that is worth addressing. Here is the problem as I see it. What if the OP only had 100 miles on his tires when the mishap occurred? Nobody in their right mind would recommend he buy a new set. How about 500? 2500? 12,000? The answer to the safety issue would be more clear cut if his tires were worn out but at 20%, I am not willing to make the call. I think it would be pretty hard for anyone who is not a mechanic or tire expert to offer a definitive answer. I suggested he contact his mechanic and I still think that is the best course of action. I just hate to see someone spend an additional $900 unless he receives some benefit from it.

Ken Fitzgerald
11-27-2013, 12:10 AM
Folks,

I will remind you that caustic, uncivil, unfriendly comments and, yes, PMs violate the Terms Of Service to which every member agrees to abide when they register.


And for the record, if you receive a PM that doesn't meet the accepted standards here at SMC, in the lower left corner of the PM when you open it, is a triangle and you can report a PM that is uncivil or threatening.

Charles Wiggins
11-27-2013, 8:26 AM
We bought a 2012 MDX last year. LOML has always liked their styling and our son has one and it has been "bullet proof" for years. We've put a lot of miles on it this year and for the first time LOML hasn't had a bad back and forth going from DC to Chicago. At any rate, took it in for an oil change to our trusted mechanics who consistently get the highest rating in Washintonian Magazine. We have 14,000 miles on the tires and one of them took a nail in it at an angle which means driving on it is not a good idea. The question is: replacing tires on all-wheel drive vehicles. I've heard two different versions: you need to replace all four, or you need to replace just the partner of the one being replaced. At $300.00 a tire, the answer could be financially significant.

I'm a cheapskate. If possible, I'd have the nail removed and put a tube inside it and keep on going. I had a smart old coot do that for me once when I picked up a piece of metal that made an oblong hole that wouldn't take a plug, and he was worried a patch wouldn't hold because it was at the curve into the sidewall. He put the patch in to keep the edges of the hole from rubbing or pinching a hole in the tube, then put the tube inside. Drove it that way until it was time to replace the tire due to wear. Never knew the difference.

Phil Thien
11-27-2013, 9:58 AM
I'm surprised the debate is still going on. Tirerack will shave tires. Just provide a measurement of the tire you're replacing, wait a couple of days, install new shaved tire.

Many local shops work with suppliers that will shave tires, too.

Edit to add: You probably have to ask at the local dealer about shaving tires. Most of them would rather sell you four tires, but if you indicate you are an educated consumer by asking about shaved tires, they may start singing another tune.

Rick Christopherson
11-27-2013, 11:06 AM
The first thing I would do is take the bad tire to a tire shop, instead of a mechanic. The nail going in at an angle shouldn't prevent it from being patched. Moreover, the risk is that the tire will leak, not that you will have a blowout. So you'll know right away whether the tire is no good or not. They won't patch a leak in the sidewall, but if it's in the tread it is usually fair game.

As for worrying about the different tire diameters, they already are different. Simply having different air pressure in each tire is going to change them just as much as the tread wear will.

To put this into perspective, let's throw some numbers at it. Let's say you have one new 19" tire and one with 1/8" tread wear, which results in a diameter difference of 0.25". At 60 mph, the spider gears in the differential will be rotating at 0.23 rev/sec, or 1 revolution every 4 seconds. Keep in mind that the whole differential carrier is rotating at 18 revolutions per second.

It is not going to hurt the differential or transfer case because the differential in speed is so trivial. It is also not going to mess the computer up thinking there is wheel spin, because the computer is expecting a constant differential in wheel speeds because cars rarely travel in a dead straight line.

William Payer
11-29-2013, 5:42 PM
I'm a cheapskate. If possible, I'd have the nail removed and put a tube inside it and keep on going. I had a smart old coot do that for me once when I picked up a piece of metal that made an oblong hole that wouldn't take a plug, and he was worried a patch wouldn't hold because it was at the curve into the sidewall. He put the patch in to keep the edges of the hole from rubbing or pinching a hole in the tube, then put the tube inside. Drove it that way until it was time to replace the tire due to wear. Never knew the difference.

Charles, I like the way you think.That tubed tire will give you the maximum life out of the entire tires set and then , when worn, you can replace them all.

We recently bought a 2014 Subaru Outback (AWD) Subaru states when replacing tires they must all be within 1/4" circumference. Failure to do so will result in abnormal wear and tear to the Subaru AWD system. So, check with the individual manufacturer's recommendations. A new tire and shaving it ( or buying a new set of 4) will be less expensive that repairs to the AWD system.

Don Morris
11-29-2013, 10:53 PM
I went with Acura's "Best" recommendation: From page 545 of the 2012 MDX owners manual "It is best to replace all four of the tires at once"... I replaced all four. I guess I'm a safety freak.