need4spd

Just so everyone knows, we can thank our flat spotting tires to FIRESTONE and FORD! The fed changed how tires are tested after the Firestone/Ford issue with the Explorer, and now the tire makers need to use Nylon outer wrap over the other main belts to make the tire comply with the low air pressure / high speed testing.

The problem is that the nylon belts have a memory effect in cool and cold temperatures (in past years makers used other materials, but if you look at the side wall of all new H speed rated and higher tires, you will see Nylon as one of the belts). Every tire that I have looked at has changed over to Nylon.

The nylon constricts at high temperature (such as in an under inflated tire at Highway speeds), and keeps the belt package nice and tight so the tire does not tear itself apart.

The downside to this better hot performance of the tires is that Nylon has a memory effect in cool/cold temps (below approx 60F depending on surface conditions), and it is not until it reheats (like driving for 10 miles or so) that the memory effect is released, and the tire stops thumping (as in the day of the Flinstones) as it goes back to round again.

Even the mighty Michelin tire has gone to Nylon belts, and hence the flat spotting on those tires on the 05 Navi cars (the MXM4's were never a problem before, due to alternate belt materials - Polyamide, a derivative of Nylon that were used up through mid-04).

So, in today’s world of protecting people from themselves and overpopulation of lawyers in the states, we take a step backwards and get tires that flat spot like the old Bias Ply tires used to do. Yes Virgina, Bias Ply tires flat spoted, and when the world went Radial, the flat spots were gone (until now).

Thanks Ford and Firestone (err, Bridgestone) for making the world a better (and bumpier) place!

So complain all you want, and get new tires, but don’t count on getting rid of cold flat spotting of tires, this has now become the most heard of complaint in new tires and new cars, and as more switch over to nylon belts, the more you will hear of it (and it will be a “Normal Characteristic” that no one will notice in the near future).

However, this does not explain the 1500rpm harmonic resonance issue (unless the tires get so out of round due to all the flat spotting of the belts that it causes permanent deformation of the tire and a harmonic is established???? Only wishful thinking ).

midas69

Well I'm going to have to disagree with atleast some of this. I worked for Goodyear about 15 years ago and they were using nylon overlays in their performance tires then. And of course, that's when I started. I have no idea how many years they were using them before that.

The purpose of the nylon was not for safety but for performance. At higher sustained speeds a tire will heat up. This heat will cause the tire to distort, thus causing changes in the way the treadface interacts with the pavement.

Nylon, unlike most other belt material, does not expand when it gets hot. Thus, the nylong ply, always used as the outtermost ply, prevents the tire from distorting as the tire heats up. This means better overall performance because the design characteristics of the tire remain true at all operating temperatures.

In the 4 years I worked there, we might have had 1 or 2 complaints of flat-spotting. But those truly were flat-spots caused by very hard stops that locked the wheels. Goodyear performance tires tended to have very soft rubber compounds and you could lose a lot of tread in a panic stop. But there were no flat-spotting complaints caused by nylon overlays.

Firestone just makes crap tires. They always have. The Explorer fiasco wasn't their first, do some research on the Firestone 721. I'm not a big Michelin fan either, but for completely different reasons.

neuronbob

An interesting and timely topic, need4spd. What's your source so we can all learn more about this? I look forward to reading other answers from folks in the tire industry.

Thanks.

need4spd

Bob – I see you moved this to the tire section, I was not sure where to post it, but based on all the discussions on the main forum of flat spotting, I put it there, no problem for the move. As for where I heard this, it is based on talking to reps from several tire manufactures (Dunlop, Bridgestone, Cooper), a few service departments (BMW, Audi, and MB), and also to a few local tire dealers and non-local dealers including the Tire Rack about the issue. – So yes I have been busy.

Also, I have been studying various tire constructions for years, while I am not in the business, nor a tire engineer, I have a pretty good understanding of tires, to the point were most of my friends discuss tire purchases with me before they buy. By no means does this mean I am an expert, or have industry experience, and the contrary, my knowledge can be completely off base, sometimes a little knowledge is dangerous.

Anyway, the overwhelming conclusion from all my discussions, is that over the last 2 years, tire flat spotting has become a problem on all tires with a speed rating of V (some say H) or higher, and our tires are included in this.

They say that in the fall, they know there will be an barrage of complaints of flat spotting that they have to say is “normal” and is across many tire brands as they have switched to nylon as the overlay of the other belts in the belt package. They have said that this is the number one complaint come the fall on cars with high performance tires (not standard all season radials such as on a Honda civic or other car with lower speed rated tires).

They have also said that this is more common on low profile high performance tires (high profile and high performance would be an oxymoron) as there is less rubber in the sidewall to cushion the effect, and they have stiffer sidewalls.

All the tire makers have told me the switch to higher levels of nylon is specifically to pass the new FMVSS (?) Federal guidelines that were established as a result of the firestone tire incident on the explorer (low pressure tire heating), and that they have had to switch from their old formulations to this high Nylon content to meet the new regulations. I have seen the switch in Yokohama AVS Sport tires and now the Michelin Pilot series, just ask a tire rack rep what tire in our size does not use nylon overlays, and the answer will be slim to none and our tire is a very popular size, with almost every maker offering a tire in the 235/45-17 size.

I can only tell you that we are not alone in complaining about this problem, and that it is happening with many cars, especially those with summer tires, the difference with us, is that we have very high speed rated all-season tires, and the other brands use high speed ratings only on their “summer performance tires” and use H rated for the all seasons.

The other thing that may effect the TL with regard to it’s sensitivity to flat spotting is that the suspension may be a bit unforgiving to this effect in its spring and shock valving, or bushing compression rates, further exaggerating the effect (plus not all TL drivers are hard core enthusiasts, sorry but true, where the summer tire packages are only ordered by those hard core drives in other brands with higher governed speeds also, that approach our stock top speed ).

Midas 69 – Thanks for your input, and yes we do agree on your first 3 paragraphs (we are saying the same thing here in different words) but maybe what differs is that your experience with Goodyear (while very valuable, and more so than my hindsight knowledge), was 15 years ago (MY 1990?) and tires at that time were in the 60 series range for high performance on most cars, not the shorter profile 45 series. Also, the speed ratings did not include the W and Y speed ranges while it did have the V and Z ratings, the W and Y have pushed the upper envelope (such as those used on the TL) to sustained high speed driving. Also the common speed rating for the masses was H, and only a few had the V or Z rated tires, where now W is common for every day use. This change in profile and larger wheel diameters (if I can remember, I think 15” and some 16” diameters were hot back then, I had a 96 Maxima SE with Goodyear RSA’s on them in a high performance 215/60-15 size, lots of cushion back then), and speed ratings has cause the dynamics to change and put more focus on the tires than ever before. That is why I think today’s tires with nylon are different than those 15 years ago (I am not trying to be argumentative here).

I do remember the Firestone 500’s that were replace with the 721’s (which I think had a problem later also) and all their other issues. And after the crappy build quality of the EL42, (and the problems my parents had with the 500’s on their 76 cougar, and the Wilderness on their Explorer), I will never accept delivery of a vehicle with Firestone/Bridgestone tires again (so much for their fancy ads).

I too am not a fan of Michelin, and would prefer other brands over them for various reasons also.

Either that or I am feeding into a line that the tire industry is telling everyone and I am promulgating the untruth????

Thanks so much for your comments.



Sorry to all for the long response!

midas69

Don't apologize, I personally appreciate the discussion. I am proud to say that since I've gotten out of the tire business, I've been very happy to ignore almost every aspect of it.

But I did want to address one point. Yes, back then, there were no Y and W rated tires. But Z rated tires at that time were considered to have no limit on the top speed. The U.S. government said that if you sold a car, the tires had to be capable of 90 minutes of driving at top speed. If I remember correctly the '89 Vette had a top speed of 170. It's stock tire was a Goodyear Z rated Gatorback.

And while you are right, there weren't a lot of 45 series tires back then, they weren't unheard of. In fact, that '89 Vette came stock with 275/40/17 tires. As far as I know, it was the first car to have tire pressure monitors.

The truth is, at the time, Goodyear was one of the few manufacturers that was capable of providing such a tire. There were a few others, but none of the mass producers such as Michelin, Firestone or Goodrich. And they weren't cheap. Those Vette tires were over $400 a pop back then.

So they weren't common back then. But believe me, with the kind of driver that the Vette attracts, if those things had flat-spotting problems, they would have been bothering us all day long.

SouthernBoy

I have to weigh in an say that the "Just so everyone knows, we can thank our flat spotting tires to FIRESTONE and FORD" thing is hardly a fault of Ford Motor Company.

However, your comment, "So, in today’s world of protecting people from themselves and overpopulation of lawyers" plus the intrusion of the government may very well be the root cause of a lot of the problems. And I agree that Firestone has produced less than admirable tires in the past.

Hey.. maybe the TL will start experiencing unintentional rollover.. then the ambulance-chasing lawyers will come to our aid and make us all rich.

need4spd

Glad you noticed.

But the government would not have intruded had it not been for the overpopulation of lawyers and people not checking their air pressure on a regular basis

need4spd

I agree, that those are similar in sidewall height as the overall diameter of the 275 is 25.7" and the 235 on the TL is 25.4", both with a 17" diameter wheel (making the sidewall roughly equal). I concede this point then.

But still the makers say it is due to the nylon belts, so not sure what Goodyear knew 15 years ago that the rest do not? Either that, or the engineers that knew are all gone and we have a pack of new ones to figure it out?

Thanks for the reply!

svtmike

I still don't buy the concept that the level of flatspotting found in the EL42 is "normal". My equivalent vintage Michelins don't exhibit any perceptible flatspotting even after sitting for an extended period (1 - 2 weeks).

Mike

A-TLvic882

How about dealer mechanic?
read https://acurazine.com/forums/ramblings-12/smilies-102314/ Post #7

neuronbob

I think most of us can agree that the EL42s were not well designed. n4s is just pointing out a common design issue--it may be more noticeable in the EL42s than in other tires. Heck, the Dunlop SP Sport 5000 tires I had on my 2G TL flatspotted mildly on cold mornings, and I simply got used to it--the super grip even during the winter was well worth the trouble at the time. My current Falkens mildly flatspot as well....

need4spd

Bob, you are absolutely correct, I am pointing out that all do it to some degree. I now have Yokohama AVS Sports, and they also flatspot. I had them on my last car (prior to the TL) in the same size, and they did not flat spot. What is the difference?

They changed the outer belt wrap to NYLON. This is how my research began, to find out why now the tire has a flat spot problem, when a tire made a few years prior to it did not, and wanted to share my experiance and understanding.


A-TLvic882 -

You are right, mechanics can not figure it out either, and typically use inferior gauges, or ones that are broken and have not been calibrated since it left the factroy (such as the ones on the end of the air hose that are dropped a million or so times, and are considered to be accurate, which I have found to be off by as much as 7PSI in my own experiance).

johnstl

Good info guys!!

JMan

Just so you know, I test drove the '05 TL with Navi, just to see if the Michelins flatspotted as well, AND they do. Like driving on a square tire until they warmed up. Just my

need4spd

Thanks for the confirmation on the Michelins, yep, they also changed their formulation on us.

You will be hard pressed to find a high performance (read high speed rating, over H) tire that does not flatspot.

You can not have your 150+ MPH top speed and have non-flatspoting tires.

Ken7

I can't believe this flatspotting and the resulting vibration, can be good for the suspension components. Even if it lasts for only 10 miles, that's 10 miles per day, every day during cold weather. Can't be good.

ARX-01b

iTrader: (1)

I highly doubt that any suspension damage can result from cold flat spotted tires at normal driving speeds. If one keep it under 50 for the first mile or two it's almost unnoticable. Then as the tire warms up increase your speed.

need4spd

I do not disagree, well a little, but it is not for 1 or 2 miles and hardly noticable. For me it would happen every day from October to April (while temps are below 50), and in my case, I work right next to the highway, so for the first 10 miles or so it went thump, thump, thump, ................... and driving at 50 or less on the highway is dangerous now a days, so it is more like 60 plus or get run over.

Simoncski

Folks, I'm In The Tire Business And I Hate To Tall You, But All Of Them Will Flat Spot When Cold---- I've Tried All Of The Major Brands In The Past And Anything Lower Than 45 Series Will Flat Spot When Cold ( Goodyears And Dunlops Seem The Worst--- Same Company)....some Of The Pirelli And Bridgestone Tires Will Eventually Get Better And Vibration Will Go Away For Good After 8,000-12,000 Miles....

need4spd

Simoncski,

Thanks for the confirmation.

In your experiance, is it all speed ratings, or just those over H and 45 series and lower?

markjrenna

My TL is parked in my driveway overnight. For the past week here in Jersey it has been getting into the single digits at night and when I go to work it isn't much higher. I know I'm in the minority here, but I don't notice any flat spotting. Is it not cold enough? How cold does it have to get? Single digits is pretty cold to me.

BTW, I have an '04 TL that I picked up late July.

need4spd

You may be parking on a warm surface (maybe a hot spring underneath? J/K.

One of the main things is that you need to be driving above 40 in a very short distance from where you are parked (I was on the parkway in less than 1/4 from work, and that is where I felt it).

For me, anytime the temp was below 55F, I would feel it.

I did not feel it after being in the garage all night (where it is warmer), just when I left work (I think we parked on top of a rock).

I will say that conditions would have to be just right.

svtmike

I've driven my car twice this December, with 2 weeks between each drive. I won't claim that my tires "don't" flatspot, but I am claiming that even after sitting 2 weeks in the same position in cold weather the Michelins on my car did not perceptibly flatspot at all.

The BS's would have been frustrating cubes.

Mike

Simoncski

Mostly V and Z rated tires with a stiffer sidewall and stronger bead

need4spd

And now the W and Y rated tires too.