Sort of an aviation related expense

John221us

John221us

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So, I got back from a flight to Redding to visit with my sister and her family, yesterday. I drove straight home from the airport. This morning, my left front tire was flat.

I get to the tire shop and they tell me there are two long nails that pierced the tire and one of them hooked into the inner sidewall (not repairable). Not only that, since the car is AWD (Lexus RX450H), you can't just replace one tire, or even two. You have to replace all four. That added $1,100 to the trip :mad2:

Fortunately (???) my tires were coming due anyways, but I never knew that you risked driveline damage and also the AWD not engaging correctly, by the tires not having even wear. This is a good thing to know, if you are shopping for an AWD vehicle.
 
I'm confused as to why AWD requires all four tires to be replaced.
 
Tread wear changes the diameter. Different diameter tires can be problematic for some, not all, AWD systems.

A buddy with a Subaru decided to ignore the limitation ... And ended up with a very expensive powertrain repair.


I'd be inclined to follow the mfgr recommendations, unless there is reliable, model-specific data to the contract.
 
Bob Noel said:
I'm confused as to why AWD requires all four tires to be replaced.
Click to expand...

It was news to me, but I looked it up and it is true. It makes some sense, in that they detect loss of traction by one wheel spinning at a different speed than the others. It doesn't make sense to me that the tolerance would be that low. I guess if one tire is bigger than the other three, it would appear like the other three are spinning faster? I know very little about it, though.
 
well, that's a dumb design. And I'm still skeptical that all four have to be replaced, maybe maybe maybe in pairs, but just pick a tire with the same diameter. And if tires have too much variation, how can you know that 4 new tires will be close enough to the same diameter.

Anyway, I guess I will avoid AWD on future vehicles. I'll go with 4wd or just FWD.

(and sorry for the sidejack of the thread)
 
> dumb (design)

The vehicles that do not have these "tire change" limitations typically use viscous couplings in their transfer cases. These are falling out of fashion with mfgrs due to customers increasing focus on MPG. The are alternative designs that use clutch-like technology, but this approach also has cost and mx/reliability limitations.


My buddy with the Subaru didn't know of the replace-all-4 req. neither did the tire shop at
Walmart. He subsequently prevailed in small claims court and Walmart ended up reimbursing.
 
On Audi's with the TORSEN center differential, the limitation is to have the tires within 3% of rolling diameter. TPMS is a stupid system that was mandated by the US Government in the wake of the Ford Explorer/Firestone exploding tire scandal and has nothing to do with AWD systems.

A well equipped tire shop could have shaved your new tire to match your old ones...but it's likely they just wanted to separate you from your money.

I would only buy AWD or RWD cars personally--FWD sucks. :D
 
John221us said:
So, I got back from a flight to Redding to visit with my sister and her family, yesterday. I drove straight home from the airport. This morning, my left front tire was flat.

I get to the tire shop and they tell me there are two long nails that pierced the tire and one of them hooked into the inner sidewall (not repairable). Not only that, since the car is AWD (Lexus RX450H), you can't just replace one tire, or even two. You have to replace all four. That added $1,100 to the trip :mad2:

Fortunately (???) my tires were coming due anyways, but I never knew that you risked driveline damage and also the AWD not engaging correctly, by the tires not having even wear. This is a good thing to know, if you are shopping for an AWD vehicle.
Click to expand...

You do not have to change 4 tires at a time, a couple of millimeters of diameter difference is not going to kill your spider gear pins.
 
I never thought about this before. My folks have a his and hers Subaru Outback and I was even starting to look at one for myself.

I just looked in the maintenance manual and here's what Subaru says:

>>
All four tires must be the same in terms of
manufacturer, brand (tread pattern), construction,
and size. You are advised to
replace the tires with new ones that are
identical to those fitted as standard equipment.

For safe vehicle operation, SUBARU
recommends replacing all four tires at​
the same time.
<<

and

>>
Warning:
When replacing a tire, you must
use a tire that is of the same size,
circumference, construction,
brand (tread pattern), speed symbol
and load index as the original
tires listed on the tire placard.
Using tires of other sizes, circumferences
or constructions
may result in severe mechanical
damage to the drive train of your
vehicle and may affect ride,
handling, braking, speedometer/
odometer calibration, and clearance
between the body and tires.
It also may be dangerous and
lead to loss of vehicle control.

You must install four tires that are
of the same size, circumference,
construction, manufacturer,
brand (tread pattern), degree of
wear, speed symbol and load
index. Mixing tires of different
types, sizes or degrees of wear
can result in damage to the
vehicle’s power train. Use of
different types or sizes of tires
can also dangerously reduce
controllability and braking performance
and can lead to an
accident.
<<
 
Last edited:
John221us said:
It was news to me, but I looked it up and it is true. It makes some sense, in that they detect loss of traction by one wheel spinning at a different speed than the others. It doesn't make sense to me that the tolerance would be that low. I guess if one tire is bigger than the other three, it would appear like the other three are spinning faster? I know very little about it, though.
Click to expand...
The issue is that the very small difference in tires adds up over distance. Think about it - if you have one tire that is smaller than the others, even by a small amount, over a lot of miles, the number of revolutions will differ greatly. If you try to turn one tire more revolutions than the others, something has to give. My educated guess is that it will be the rubber in all the tires, as well as the metal parts that are meshed together. Granted, I don't know the construction of an AWD drivetrain, but simple logic tells me this. In the same way, my dad always taught me that the rear wheels (on a RWD car) or the front wheels (on a FWD car) should be replaced at the same time. Non-drive wheels don't matter so much, as they aren't "tied" together through the drivetrain.

MSPAviator said:
On Audi's with the TORSEN center differential, the limitation is to have the tires within 3% of rolling diameter. TPMS is a stupid system that was mandated by the US Government in the wake of the Ford Explorer/Firestone exploding tire scandal and has nothing to do with AWD systems.
Click to expand...
I didn't know this. Interesting. Thanks.
MSPAviator said:
I would only buy AWD or RWD cars personally--FWD sucks. :D
Click to expand...
Hmmm... Never driven in snow, have you? ;)
 
I had a friend with an EVO who had a nail in a tire on a pretty new set of tires. TireRack ended up "shaving" the single new tire he bought down to the tread that was on the other 3. Worked like a charm!
 
hopmedic said:
If you try to turn one tire more revolutions than the others, something has to give. My educated guess is that it will be the rubber in all the tires, as well as the metal parts that are meshed together.
Click to expand...

There is no wear increase to the rubber,that's what differentials are for. The meshing gears are meant to mesh.

A 195 65 R15 tire will have a 78" circumference or 812 revolutions per mile. A 205 65 R15, a full size larger, will have an 80" circumference or 792 revolutions, 20 more per mile on a full size difference. If this would damage differentials UPS would be changing them a couple time a year since they get a greater use out of their differentials from setting up to make as many turns as possible to the right.
 
Sac Arrow said:
Wow. Now I know I don't want an AWD vehicle.
Click to expand...


That's true regardless unless you live somewhere that requires the traction, but if this tire issue is the one that does it for you, it's the wrong reason. The reason to avoid AWD is added expense for no benefit.
 
Henning said:
You do not have to change 4 tires at a time, a couple of millimeters of diameter difference is not going to kill your spider gear pins.
Click to expand...

But it will heat a viscous coupler.

An old jeep with open axle and center diffs will be just fine. A modern AWD system with viscous or progessive couplings will wear out if you run old/new tires
 
PBristolJr said:
I had a friend with an EVO who had a nail in a tire on a pretty new set of tires. TireRack ended up "shaving" the single new tire he bought down to the tread that was on the other 3. Worked like a charm!
Click to expand...

I realize that may be the only way to do it, but I would cringe "shaving" rubber off a $200.00 tire for any reason. :yikes::mad2:
Another great reason to live in the south, we don't need no stinkin AWD. :D You can't jack em up like 4X4's! :D
 
N747JB said:
I realize that may be the only way to do it, but I would cringe "shaving" rubber off a $200.00 tire for any reason. :yikes::mad2:
Click to expand...

There was a time when I'd agree with that, but I haven't worn out a tire in a couple of decades, they all come apart long before the tread is even close to gone.
 
This thread is reminding me that I need to order the stronger servo from the Corvette to put in the Yukon. Sloppy shifting sucks.

TPMS is a pain in the ass if you want to run summer and winter tires and put the winter tires on cheap black painted steelies.
 
N747JB said:
I realize that may be the only way to do it, but I would cringe "shaving" rubber off a $200.00 tire for any reason. :yikes::mad2:
Another great reason to live in the south, we don't need no stinkin AWD. :D You can't jack em up like 4X4's! :D
Click to expand...

They didn't give me the option to shave it. Besides, the tires had 33,000 on them, so I wouldn't have done that. I guess if I was faced with tires that only had 5,000 on them, I would consider that.
 
John221us said:
They didn't give me the option to shave it. Besides, the tires had 33,000 on them, so I wouldn't have done that. I guess if I was faced with tires that only had 5,000 on them, I would consider that.
Click to expand...

Yeah, you were probably getting close to buying tires anyway, but it sucks to have to buy them before you want to buy them. :(
 
I've plugged sidewalls without a problem. Shops won't do it, but it works. Carry a 5 dollar plug kit and a ten dollar pump and you are all set.
 
mmm, yup... Had a nail on a sidewall while on a trip and had to spring for a new tire... I pointed out that one of the other tires had a plug in the sidewall (by me) at least 15K miles ago and it was still fine... He just shrugged and said he was paid by the hour not by the tire and he would get fired... Tough to argue with a guy who just wants to keep his job - especially when you are hundreds of miles from home...
 
John221us said:
So, I got back from a flight to Redding to visit with my sister and her family, yesterday. I drove straight home from the airport. This morning, my left front tire was flat.

I get to the tire shop and they tell me there are two long nails that pierced the tire and one of them hooked into the inner sidewall (not repairable). Not only that, since the car is AWD (Lexus RX450H), you can't just replace one tire, or even two. You have to replace all four. That added $1,100 to the trip :mad2:

Fortunately (???) my tires were coming due anyways, but I never knew that you risked driveline damage and also the AWD not engaging correctly, by the tires not having even wear. This is a good thing to know, if you are shopping for an AWD vehicle.
Click to expand...

I have a Lexus rx450 in the shop right now that ignored this and put two new tires with 2 old ones both are same size different brands with almost 3/4" difference in diameter..... The transaxle is being replaced as I type this. 4.5 aviation monetary units, ouch!
 
N747JB said:
Yeah, you were probably getting close to buying tires anyway, but it sucks to have to buy them before you want to buy them. :(
Click to expand...

Because they knew they were coming due and had 80% of the known upcoming cost saved already, right? ;) ;) ;)

Just pointing out there are ways to avoid so-called "surprises". Most of us (me included) often don't do it right. :)
 
Don Jones said:
I have a Lexus rx450 in the shop right now that ignored this and put two new tires with 2 old ones both are same size different brands with almost 3/4" difference in diameter..... The transaxle is being replaced as I type this. 4.5 aviation monetary units, ouch!
Click to expand...

Good to know :yikes: I had a RX400H before this car (2008) and a squirel or some type of rodent ate through a tranny line while I was backpacking. Long story short, I didn't realize it and the tranny siezed up on the way home. It was close to 9 AMUs, so I just rolled into another lease on the RX450H.
 
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