Which tires are succeptible to flat-spotting?

[Quattro Pete]

I just put on a new set of Dunlop SP Maxx (235/45/17 94Y), running around 35 PSI all around. When warmed up, they're great, but after the car sits for 8 hours or overnight, the first 5 miles of travel result in vibrations felt on the steering wheel at speeds of around 50-55 mph. After that, it's back to smooth again.

I'm guessing this is a result of flat-spotting and the tires need some 'exercise' to become round again. I've read about this, but this is the first set of tires that I have owned that in fact noticeably exhibits this behavior.

Have you had any tires that were succeptible to flat-spotting? Does the issue affect mainly lower profile tires? FYI, I've had some other tires in size 225/45/17 before that didn't suffer from this (Bridgestone S03, ContiSportContact2).

 

[CapriRacer]

Flatspotting is mainly a function of the amount of nylon used in the tire.

It's a "good news / bad news" sort of thing.

The good news is that nylon is a wonderful material - it shrinks when heated - so it really helps with the integrity of the tire especially for speed capability.

The bad news is that once heated, it tends to take the shape it is in when cooled, and needs to be reheated to "unlearn" that shape.

I would suggest a bit more inflation pressure, and a gradual slowing down before you park the vehicle.

 

[Quattro Pete]

Thanks. Yeah, I was thinking of trying a higher PSI... gonna bump it up to 40.

 

[wantin150]

Quattro:

I'm running some 225-45-17 Eagle F1's around 40 PSI and have not had a problem with flat spots. I'm interested in the fact that your tires do it overnight. What size rims do you have? The 235-45-17 is a plus size for me but my rim width is only 7 in. The minimum recommend rim width for that size is 7.5 in. If you're running a 7 in, would that somehow contribute to the problem?

 

[Quattro Pete]

wantin150,

My rims are 17x8. 235/45/17 94Y is the OEM size for my car.

 

[wantin150]

Thanks Quattro. I had actually considered the same tire as a replacement when the F1's wearout. I may reconsider now.

 

[Quattro Pete]

Honestly, I have never heard anyone complain about flatspotting of the Maxx before. That is why I'm wondering if just my set is somehow defective.

I received a response from Dunlop to take them to an authorized Dunlop dealer for inspection. The thing is - by the time I get there the tires will be warmed up already and not flatspotted so there will be nothing to inspect.

The F1 is a great tire. It came in first in the recent C&D tire shootout.

 

[Finklejag]

I know the Continental Conti-Extrems are prone to flat spotting. This is from many people on all the forums that I visit. I guess it's still a great tire from what I have read though.

 

[Quattro Pete]

AFAIK, there was a mfg defect with the CEC - they were just simply out of round, which means the vibration didn't go away, even after the warm up.

 

[Hermann]

Puchased some Bridgestone Turanza LS-V;s 215/50-17, and have had several episodes of Flat spotting, on cold mornings when the car has sat for close to 24hours. But on a 2 hour interstate drive today at speeds of 75 to 80 MPH they were very smooth and vibration free. Got up to 85 a time or two and still very smooth. The other plus is the vastly improved braking. Braking this hard on the stock Michelin's would have activated the ABS. The trade-off would be more pleasing if I did more long distance driving at speed.

 

[alreadygone]

Quatro,

Please look at tires and let us know if they don't contain nylon as Capri Racer suggested. If you mainly do short trip stop and go you may want to insist dealer "trade" for non nylon construction. But if your driving includes a lot of long distance driving, you'd be better off learning to live with it for the first few miles. As nylon is STILL the most durable, toughest, material used in tire construction ever.

Bob

 

[Quattro Pete]

Yes, Capri was correct - they do contain 2 plys of nylon. I mostly do short trip stop and go type driving, about 12 miles one way. These tires were bought from TireRack and specifically requested by me. At this point, I really can't swap them out for something else. I guess I should have done my research better. However, in all the reviews I've read, I haven't found a single one that mentioned these tires' succeptibility to flatspotting.

 

[CapriRacer]

Quote:

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...However, in all the reviews I've read, I haven't found a single one that mentioned these tires' succeptibility to flatspotting.

......

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I think you will find that any tire with an H speed rating or higher will have a single nylon ply, and V rated and higher will have 2!

Unfortunately, flatspotting is a fact of life when it comes to nylon.

 

[Quattro Pete]

Both the CSC2 (Y-rated) and S03 (W-rated) that I had before contained nylon (the CSC2 for sure) and yet there was no noticeable flatspotting.

 

[y_p_w]

There are almost no speed-rated tires today that don't have a nylon cap, which tend to reduce temperatures and keeps tires together when there's a puncture. Remember the Firestone Wilderness tire problem. There was almost universal consensus that they would never have had that rate of blowouts if there was a nylon cap on the tire.

BTW - another term that may include nylon is "polyamide". Wool and silk are natural polyamides, but with tires it's likely nylon or possibly Kevlar.

 

[CapriRacer]

Quote:

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....There are almost no speed-rated tires today that don't have a nylon cap, which tend to reduce temperatures and keeps tires together when there's a puncture......

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I hope you mean H and higher speed rated tires. S and T rated rarely have cap plies.

Quote:

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.... Remember the Firestone Wilderness tire problem......

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Exactly my point - they were S speed rated.

Quote:

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....There was almost universal consensus that they would never have had that rate of blowouts if there was a nylon cap on the tire.....

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This takes quite a few different forms:

1) Every tire ought to have a nylon cap ply

2) Every tire ought to be at least H speed rated.

While from a tire's perspective, these are pretty much equivalent statements, they are quite different from a legal perspective.

Imagine telling everyone that they have to buy a more expensive H rated tire, just because Big Brother says it's safer - which is why this hasn't been mandated!

Quote:

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....BTW - another term that may include nylon is "polyamide". Wool and silk are natural polyamides, but with tires it's likely nylon or possibly Kevlar.

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Nylon makes a wonderful reinforcing fiber for tires, but Kevlar does not.

Kevlar tends to shatter like glass when compressed. That means the tire has to be handled carefully and more importantly, the tire can not be allowed to run underinflated!!!

 

[y_p_w]

Quote:

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Quote:

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....There are almost no speed-rated tires today that don't have a nylon cap, which tend to reduce temperatures and keeps tires together when there's a puncture......

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I hope you mean H and higher speed rated tires. S and T rated rarely have cap plies.

Quote:

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.... Remember the Firestone Wilderness tire problem......

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Exactly my point - they were S speed rated.

Quote:

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....There was almost universal consensus that they would never have had that rate of blowouts if there was a nylon cap on the tire.....

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This takes quite a few different forms:

1) Every tire ought to have a nylon cap ply

2) Every tire ought to be at least H speed rated.

While from a tire's perspective, these are pretty much equivalent statements, they are quite different from a legal perspective.

Imagine telling everyone that they have to buy a more expensive H rated tire, just because Big Brother says it's safer - which is why this hasn't been mandated!

Quote:

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....BTW - another term that may include nylon is "polyamide". Wool and silk are natural polyamides, but with tires it's likely nylon or possibly Kevlar.

---

Nylon makes a wonderful reinforcing fiber for tires, but Kevlar does not.

Kevlar tends to shatter like glass when compressed. That means the tire has to be handled carefully and more importantly, the tire can not be allowed to run underinflated!!!

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I may have been wrong about which speed-ratings generally correspond to a nylon cap. My dad has the B/F Goodrich Traction T/A T which is T speed-rated, but has a nylon cap. I haven't bought any tire in the last 14 years that hasn't at least carried an H speed-rating, and usually have gotten V/Z/W speed-rated tires.

I think a nylon cap is such a valuable safety feature that I wonder who in their right mind would look at one as a detriment because of a possibility of flat-spotting.

I also thought I read some of the Wilderness tire models didn't carry any speed rating. I know there's the occasional non speed-rated tire still out there.

I also thought that Kelly Tires used to include a Kevlar ply in most of their offerings.

 

[Quattro Pete]

Quote:

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I think a nylon cap is such a valuable safety feature that I wonder who in their right mind would look at one as a detriment because of a possibility of flat-spotting.

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From this discussion it appears that most tires contain nylon, and in that case it must be something else that is responsible for flatspotting, because I've owned a lot of different H and higher rated tires in the past, and none of them exhibited this, apart from this Dunlop. Even Dunlop Customer Service was surprised to hear about this. Maybe there is something wrong with my set in particular?

 

[CapriRacer]

Quote:

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....From this discussion it appears that most tires contain nylon, and in that case it must be something else that is responsible for flatspotting, because I've owned a lot of different H and higher rated tires in the past, and none of them exhibited this, apart from this Dunlop. Even Dunlop Customer Service was surprised to hear about this. Maybe there is something wrong with my set in particular?

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Like I posted earlier it is rare for an S and T rated tire to have cap plies. However, nylon may not be documented on the sidewall, but be in the form of strips - not enough to be considered a "ply".

ALL tires will flatspott if left unexercized long enough. However, tires with nylon are more prone to flatspotting and, obviously, the more nylon, the greater the tendency.

But I suspect that the latest version of nylon application - spiral wrapping - may be somewhat responsible for the apparent differences, especially if the spiral is pre-tensioned. It's also possible that the amount of rubber in the tread may also be a factor - heavier tires being less prone.

The downside to all this is that tires that are less prone to flatspotting, probably have less performance improvement due to the nylon - the old trade-off thing.

 

[alreadygone]

Remember kevlar belts,,,JUNK!!

Bob