Flatspotting? Try Saying No to Nylon and Yes to Polyamide

Have you ever noticed a minor vibration that appears to go away in about five minutes of driving, only to appear the next morning? What you're experiencing is a phenomenon called flatspotting. The tire develops a "square" side because of the weight of the vehicle resting on the tire. Tires are more apt to flatspot during colder weather, therefore drivers in the Snowbelt will begin to notice this in the fall. Higher speed rated tires are more likely to flatspot because they use a cap of nylon or polyamide that's between the steel belts and tire tread to reinforce the tire so it can survive the high-speed test.

As the tire warms up it becomes "round" again, causing the vibration to go away. It's particularly annoying for drivers that have short commutes because their tires never get a chance to lose the vibration.

Flatspotting can occur on any vehicle but it's often masked so it's unnoticeable. Every once in awhile it can show up in new versions of an existing model. For example, when Acura launched the 2004 Acura TL, most TLs were equipped with the Bridgestone Turanza EL42 (not to be confused with the Turanza Serenity and its replacement the Turanza Serenity Plus) and many drivers experienced flatspotting on their vehicle. 

How do you go about solving this issue? Many drivers experience much less or no flatspotting by switching to a tire that uses a polyamide cap instead of a nylon cap because nylon tends to have a memory effect.

If you're looking for tires that are more resistant to flatspotting, try to pick an option with a polyamide cap instead of nylon. Many manufacturers, such as Michelin have begun to use polyamide more.


Saturday, November 10, 2012 by Anthony

Thanks for the post. I have had flatspotting through 3 different sets of tires over the years and would love to find a sure way to identify tires more prone to this problem.

I am buying new tires now, and I see that some tires have Nylon and some (like most Michelins) have Polyamide listed on the sidewall. However after seeing this post and reading more, I am confused, it seems that Nylon is a type of Polyamide. So Polyamide is the term for several different synthetic fabrics, one of which is Nylon.

Does anyone know if this is correct, or knows more about this? Now I am not sure if getting a tire that specifies Polyamide is truly something other than Nylon. What do you think?
Tuesday, November 13, 2012 by cy

Yes, in very basic terms polyamides are polymers held together by amide links.

Nylon 66 ((polyhexamethylenediamine adipamide) is the specific nylon polyamide traditionally used in circumferential cap plies.

So when a tire manufacturer lists Polyamide as a reinforcement materiel, they're using a polymer other than standard Nylon 66.

So what's the secret polyamide recipe that Tire Company X uses? Understandingly the tire companies don't release these proprietary details just like a Formula One team doesn't explain how their cars got faster.

Ultimately the proof is in the pudding and we've seen a pattern of improved resistance to flatspotting in tires using what tire manufacturer refers to as polyamide. Obviously some vehicles are more sensitive to flatspotting so keep this in mind when you make your tire choice.
Tuesday, January 22, 2013 by root_cause Bob

I've got Michelin Primacy's on '99 and '03 Accords. Always garage-kept, the Primacy's have 'flat-spotting' but ONLY sometimes, and they always warm up within a few miles. I'm still gathering data, but it appears the tires need be parked for at least 3 days at 50deg. F storage, after being driven at ambient over 60 deg. F. I'll try and follow up with more conclusive data.
Wednesday, January 23, 2013 by cy

Thanks for your input.


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