It sort of makes sense the rear tires might be more prone to develop flat spots than the front on fwd cars. The reason is the weight of the car is considerably less in the rear, no engine back there. That allows the rear end to bounce around a little more than the front can. That can lead to a “washboard” effect on the surface of the tires. There may or may not be a suspension problem with the car. Usually if there is, the car owner would have already noticed it, going over bumps etc would be considerably less pleasant than when the car was newer.
Rotating the tires more frequently should definitely help. If the tire literature doesn’t say, try maybe 15K miles as the interval, switching the front to the rear & visa versa. Keep them on the same side, best not to change the direction of rotation.
If there is a problem besides lack of rotation that caused this, it would most likely be the car’s suspension, the tires weren’t properly balanced or the weights fell off, the new tires were out of round, there’s some problem with the car that is causing an out of round situation, or bad wheel bearings.
I had flat spot disease on my Corolla on a rear tire a while back, just one of the rears, the suspension performance seemed ok when I did the bounce test, and no different than the other side, the wheel bearing seemed ok, no play, and there were no obvious wheel weights missing. My solution, I moved it to the front and that seemed to fix it.
Front drive cars can have this problem even without bad rear shocks especially if you don’t usually carry passengers or luggage. The problem is that most of the weight of a front drive car is on the front wheels but the rear springs and shocks have to be stiff enough to handle a fully loaded car with 5 people and luggage in it. It cups the rear tires and once cupping starts, it makes itself worse by adding to the bounce of the rear tires.
Some front wheel drive cars are more susceptible to wear patterns in the rear such as cupping/scalloping than others. Light weight and insufficient tire pressure are factors. Once a wear pattern develops in only gets worse. This is one of the reasons the tires need to be rotated.
I have found on some vehicles that seem to never have a cupping problem that odd brands of tires with a more aggressive tread pattern will cup in the rear if not rotated.
Cupping/scalloping can often be seen on off road/mud tires, the large voids/space between tread lugs sets off a rhythm that causes cupping when used primarily for highway use.
I have purchased used cars with neglected tires and put the noisy cupped tires in the front and waited for the tread to wear even. This isn’t an option for customers, they are very intolerant to noise.
“Free tire rotation” is an offer to get customers in the door. If your in for an oil change there is no need to promote free work. Nobody likes to work for free and a shop can’t rotate your tires without your consent.
I have had a couple of customers in for an oil change/tire rotation with a Costco tire rotation reminder sticker on the windshield due in about 500 miles. I had to wonder why they were paying for a tire rotation when they could get it done for free at Costco. I think they later went to Costco to have the tire rotation reversed because they really didn’t know what was going on.
First, the guy at the shop is using the term “flat spots” to try to describe a phenomenon that is more accurately described as “irregular wear” - and the most common cause of irregular wear is misalignment. Not rotating the tires gives even slight amounts of misalignment a chance to develop small, undetectable amounts of irregular wear into large and quite annoying amounts of irregular wear.
Second, the tire manufacturer’s warranty will state that the tires have to be regularly rotated - which is why the shop isn’t volunteering to replace the tires.
At this point the damage is done. You are stuck with the tires.
(BTW, I would have thought that after 30 years, the idea of rotating tires would have come up by now, but since it hasn’t, this may be a good time to learn the lesson.)
Since the OP is probably not aware of it, I will point out that Capri Racer is our resident tire expert. I am very glad that Capri Racer supported my earlier statement regarding the importance of tire rotation if one wants to get full life from a set of tires.
For whatever it’s worth we paid for an alignment when we had the 4 new tires put on the car.
Two different guys at the shop used the terms “flat spots” and “squared” multiple times when I spoke with them about the tires. I appreciated all the other suggestions and possible causes to the tire damage. Again, the shop is adamant that it’s strictly a tire rotation issue.
After they switched the tires they second time I was going to have my wife pick the car up in the afternoon. The manager and I spoke on the phone about this and thought it would be best we continued the discussion in person so he could physically show me the tire damage. He said they are open to 8PM…. so I went after work with my wife to meet him… however, he had left for the day and the guy at the counter didn’t know much about the specifics of my conversation with the manager. The manager had also offered to work with us on getting 2 new tires. We have bought about 20 tires from them over the past 8 years on our cars, and cars for my two oldest kids. I was disappointed that the manger wasn’t there when we arrived and that he didn’t pass along any info or a tire quote to the guy at the counter. That was 2 days ago and he hasn’t tried to call me ever after we expressed our frustration about the manger not being there to the guy at the counter. I am going to call him again, or stop by…. but wanted to do a little research on my own first. Again, I appreciate all the feedback. I am also going to try to look at the tires closer tonight and see if I can see the flat spots myself…
@rdwarr - can you see or feel any irregularity in the tread? If you can, Google ‘tire wear patterns’ and look at the various photos and illustrations, let us know which best describes your problem. It sounds like ‘cupping’. ‘Flat spots’ are usually one per tire, caused by locking up the brakes and wearing a flat spot on the tread, or by a car sitting for a long period of time (but that usually goes away after a bit of driving, and is uncommon these days).
If there are no visible irregularities, then I’m thinking it’s some kind of internal tire damage or out of balance problem, maybe combined with worn shocks/struts.
I’m really surprised that you’ve stated you’ve dealt with car maintenance for 30 years, but aren’t aware tires need to be rotated. Frankly, this is all your fault, and you’re lucky they’re willing to work with you at all.
I have had a couple of customers in for an oil change/tire rotation with a Costco tire rotation reminder sticker on the windshield due in about 500 miles. I had to wonder why they were paying for a tire rotation when they could get it done for free at Costco.
Maybe they just should have gone to Costco for the free tire rotation and paid them for the oil change.
Oh wait…Costco doesn’t do an oil change. It just makes sense to get the tires rotated as part of an oil service. Why make an extra trip when the tires can be rotated right now with the oil change? Free is only a good thing when it makes sense.
Recently we had a car in for a 60K service, in addition to the service we found that the car needed a battery, rear brakes, and a tire repair for a nail puncture. Customer declined the tire repair because the tire store offers free flat repairs. The car is in the shop for $600+ worth of work already, and you’re going to pick it up, find the time to drive to the tire store and wait while they fix your tire in a hopefully timely fashion? Might save you $20 but at what cost?
They should have disposed of that Costco tire rotation label. Their tires measured something like 5/32" in the front and 8/32" in the rear, they were doing something wrong. If they were rotating their tires every 5,000 mile the tread should have a difference of no more than 1/32".
Yup. A woman brings her car in, she’s making a trip to the Oregon coast this weekend and wants to get the oil changed before she goes. I tell her “Your car needs a new battery.”
She says “Oh, I know. Sometimes I have to jump start it in the morning to get to work.”
“OK, would you like us to replace that for you today?”
It is too easy and simplistic to attribute rear wheel tire scalloping or flat spotting to misalignment and difficult to disprove. We have seen scalloping/flat spotting in too many cars that we bought new to make it dificult to believe that they all had rear wheel misalignment from the factory. Something else is going on and I wonder if the lack of substantial vehicle weight on the rear tires of a front driver as suggested by others might have something to do with the irregular wear described.
It’s hard to say exactly how something like tire flat spots would start. It’s sort of like washboard roads, the washboards are clearly there, made worse w/every vehicle that bumps over them, but how they actually start from a smooth dirt road, who knows? It’s the butterfly effect. Any slight disturbance could get the pattern started. A car parked for several weeks with one of the rear tires low on air pressure, a slight asymmetry of one rear wheel’s alignment compared to the other, or just a tire that wasn’t manufactured perfectly round in the first place.
Just an FYI on irregular wear, “flat spots”, cupping, and how they are generated.
Research shows a connection between higher order harmonic vibrations and the sensitivity particular tires have to irregular wear. The problem would be trying to minimize these affects. You can’t eliminate them as tires are flexible by their very nature (and as George pointed out, roads aren’t perfectly flat, nor are tires perfectly round).
That leaves the sensitivity of the tire itself - which is a whole avenue of research itself. Suffice it to say, tire manufacturers are working to reduce the sensitivity of their tires to prevent consumer dissatisfaction.
circuitsmith said: “… Seems to me the properties that lead to lower rolling resistance (internal friction?) would also lead to more vibrations…”
Sorry, but, No! Rolling resistance is more or less about the internal friction (hysteresis) generated when a tire rolls. This is mostly controlled by the rubber used in the tread.
Vibrations are mostly about uneven distribution of material around the circumference of the tire.
But if you were referring to the transmission of irregular road surfaces through the tire to the suspension, I’m afraid there is almost no contribution the tread rubber has towards damping this out. The input is just too large for the tread rubber to have much effect.