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Flat spotting question #5189927 08/17/19 09:27 PM
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RyanY Offline OP
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I currently have Cooper CS5 Ultra (P225/55R16) on my Cadillac and they often have flat spotting issues after sitting for a few hours. Otherwise I really like them and am considering the CS5s for my Odyssey. However, I was wondering if low profile tires (below 60 profile) show flat spots more often than higher profiles? If so I will exclude them from my list of possibilities, as I would like to have relatively smooth performance from the start, if this is possible.


2007 Cadillac CTS 3.6L >127k miles (Castrol Magnatec 5W-30 + ACDelco PF2129G)

2012 Honda Odyssey EX-L >103k miles (Pennzoil Platinum 0W-20 + Fram XG7317)
Re: Flat spotting question [Re: RyanY] #5189938 08/17/19 09:51 PM
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clinebarger Offline
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It's been my experience that the softer the compound....The easier they flat spot. But I have never experienced this phenomenon with a few hours of sitting? Usually takes a week or longer.


2001 Chevy Camaro L92/4L80E
2006 Chevy 2500HD LBZ/Allison 1000
2010 Toyota Corolla 2ZR-FE/U341E
2000 Toyota Avalon 1MZ-FE/A541E
Re: Flat spotting question [Re: RyanY] #5189947 08/17/19 10:09 PM
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oldhp Offline
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Never heard of flat spotting after a few hours. Maybe hot temp, hot tires sitting on cooler concrete??? What is the air pressure at?


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Re: Flat spotting question [Re: oldhp] #5189951 08/17/19 10:16 PM
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RyanY Offline OP
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Originally Posted by oldhp
Never heard of flat spotting after a few hours. Maybe hot temp, hot tires sitting on cooler concrete??? What is the air pressure at?

I have tried 33, 35, 37, and 40 and all pretty much the same result. The worst flat spotting occurs in the morning but has also occurred after 4 hrs. I presume it results from hot tires cooling off, as suggested. However this is the first set of tires with this issue on my cars, and I dont drive or park any differently than before.


2007 Cadillac CTS 3.6L >127k miles (Castrol Magnatec 5W-30 + ACDelco PF2129G)

2012 Honda Odyssey EX-L >103k miles (Pennzoil Platinum 0W-20 + Fram XG7317)
Re: Flat spotting question [Re: RyanY] #5189955 08/17/19 10:21 PM
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CapriRacer Offline
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The problem is the nylon cap ply(s). The soft rubber or the profile have nothing to do with flat spotting.

Ya' see, nylon has a relatively low glass transition temperature. The glass transition temperature is the temperature where a material under goes a phase change. We are all familiar with materials changing from liquid to solid or to a gas - water is a good example - but some materials will make more subtle changes - and nylon is one of them.

Unfortunately, that size is going to have cap plies, because the lowest speed rating is an H (excluding winter tires) - and H rated tires have cap plies. You need S or T rated tires to have a chance of avoiding cap plies (note: even some S and T rated tires have cap plies)

So let's see if we can help the situation:

First try a few more psi - like 3 to 5. It just might be that the tire is marginal for size and a bit more pressure will make the tires run cooler and may be stay below the glass transition temperature. (Note: I was writing my reply when you made your post about tire pressures.)

Second try driving more gently. Hard cornering or high speed driving heats up tires, so allowing a longer cool down time (like after exiting the freeway) or taking turns more slowly, might also keep the tires out of the temperature range.

Certainly a different tire size might have more options. A 215/60R16 would work and according to Tire Rack has many S and T rated tires. Just be aware that you will likely be giving up handling crispness going to the lower speed rating.

You could also go with a slightly larger size: 225/60R16, but that has the disadvantage of being over 3% larger and some tire shops won't go there.

Last edited by CapriRacer; 08/17/19 10:28 PM.

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Re: Flat spotting question [Re: CapriRacer] #5190086 08/18/19 06:55 AM
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RyanY Offline OP
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Thanks for this suggestion. I will explore additional info on the nylon end cap alternatives and try to find a suitable model for the Odyssey.


2007 Cadillac CTS 3.6L >127k miles (Castrol Magnatec 5W-30 + ACDelco PF2129G)

2012 Honda Odyssey EX-L >103k miles (Pennzoil Platinum 0W-20 + Fram XG7317)
Re: Flat spotting question [Re: RyanY] #5190182 08/18/19 08:49 AM
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wag123 Offline
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Just go with CS5 Grand Tourings for the Odyssey. I have them on my Sienna and IMO they are just as good as the Michelins I had on it previously, for a third less money. They are 60 series T-rated tires, they ride smooth and quiet, they do not flat spot, and they are manufactured in the USA. After one year and a couple of long road trips, I have had no issues with them.

Re: Flat spotting question [Re: RyanY] #5190258 08/18/19 10:20 AM
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IndyIan Offline
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How long do they stay flat spotted? I had a set of high performance summer tires on the Focus that would thump for about 1-1.5 miles on the hwy, but that was 2 min of my 36 minute commute so I didn't mind, plus it let me know that they were warmed up for the corners!


07 Focus ZXW, 5spd manual, 245km M1 5W30
18 Outback 2.5 CVT 35km 0W20
Re: Flat spotting question [Re: IndyIan] #5190397 08/18/19 01:40 PM
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Quattro Pete Offline
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Originally Posted by IndyIan
How long do they stay flat spotted? I had a set of high performance summer tires on the Focus that would thump for about 1-1.5 miles on the hwy,

The Contis on my 530i wobble for about the first 3 miles or so. That's about half of my commute.


2002 530i   2015 Q5 3.0T   2018 Charger SRT
Re: Flat spotting question [Re: IndyIan] #5190635 08/18/19 07:13 PM
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RyanY Offline OP
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Originally Posted by IndyIan
How long do they stay flat spotted? I had a set of high performance summer tires on the Focus that would thump for about 1-1.5 miles on the hwy, but that was 2 min of my 36 minute commute so I didn't mind, plus it let me know that they were warmed up for the corners!

My Cad's CS5s thump for a mile or two which is most of my commute. Not a huge deal but enough to make me look for different tires for the Ody.


2007 Cadillac CTS 3.6L >127k miles (Castrol Magnatec 5W-30 + ACDelco PF2129G)

2012 Honda Odyssey EX-L >103k miles (Pennzoil Platinum 0W-20 + Fram XG7317)
Re: Flat spotting question [Re: RyanY] #5193528 08/22/19 03:28 AM
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bonjo Offline
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can you describe how this affects the handling? steering wheel vibration, pulling or something else?

Normally I associate flat spotting with localised rubber wear when you lock up and the tyre slides and it is permanent.

Am I right in thinking your problem may be tyre deformation? I would be interested to see the solution.

My car was in storage for 1.5 year (on concrete floor) and I experienced wheel vibration after that. Had them balanced few times and eventually changed the tyres. Problem is still there but a lot less pronounced. What is strange is that it happend within a range of speed (75~85) and sometimes when accerlerating or decelerating but not both
??? which make me think maybe the drive trains (4x4)

Re: Flat spotting question [Re: bonjo] #5193561 08/22/19 06:06 AM
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CapriRacer Offline
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Originally Posted by bonjo
Can you describe how this affects the handling? Steering wheel vibration, pulling or something else?

Normally I associate flat spotting with localised rubber wear when you lock up and the tyre slides and it is permanent.

Am I right in thinking your problem may be tyre deformation? I would be interested to see the solution.

My car was in storage for 1.5 year (on concrete floor) and I experienced wheel vibration after that. Had them balanced few times and eventually changed the tyres. Problem is still there but a lot less pronounced. What is strange is that it happened within a range of speed (75~85) and sometimes when accerlerating or decelerating but not both
??? which make me think maybe the drive trains (4x4)


You are correct that the term "flatspot" is frequently used to describe the tire wear you get when you lock up a brake. Technically, that is called "Spot Wear". (See the Tire Industry Association's manual: Passenger and Light Truck Tire Conditions Manual)

But the term also applies to a physical deformation where the part of the tire that was in contact with the ground while the vehicle was parked doesn't completely return to the "round" condition when put back in service. This can be a temporary or permanent condition.

The symptoms are a vibration, that generally goes away after a couple of miles. If it doesn't, the flatspot could be permanent, or the vibration could be coming from something else.

Please note: Wheel end vibrations tend exhibit themselves in 50 to 70 mph range (80 to 115 kph). That's because a wheel end vibration tends to excite the resonant frequency of the suspension. (See Wikipedia: Resonance) and that generally occurs in the 50 to 70 mph range.

Cause: Most common is the fabric reinforcement's glass transition temperature - nylon being the typical culprit. Please note that polyester and rayon also flat spot, but to a much, much lower degree.

The glass transition temperature is where a solid material (as opposed to a gas, liquid or plasma) undergoes a change but doesn't change it's fundament state (gas, liquid, solid, plasma). In the case of nylon, it's glass transition temperature is at the upper range of a tire's operating temperature.

That's why nylon is no longer used for the ply material, but - unfortunately - it has a property that is very advantageous for use in a cap ply (the fabric overlay of the belts). It shrinks when heated. This shrinkage reduces the growth of the tire due to centrifugal forces and therefore allows a higher speed capability (It also reduces the risk of a belt separation.) So you will see nylon cap plies used in H and higher speed rated tires.

Solution? First, ALL tires will flatspot. It's not just a question of the glass transition temperature as there are other things that affect the speed and severity of the flatspot So, it's a question of how quickly it gets bad. Aggravating factors are high heat, long idle time, low inflation pressure, high loads, etc.. Also, the higher the temperature of the tire when it was idled can trigger a severe flatspot.

Second, not all tires with nylon cap plies have this problem or more precisely stated, they have less of a tendency to develop this problem. The tire manufacturer can reduce the tendency by the choice of nylon type, and the way the nylon gets processed in the manufacturing operation.

What can a consumer do? Allow the tires to cool before putting the car away. Immediately parking a car after driving on the freeway is a good way to generate a flatspot.

Avoid parking on cold surfaces when the weather is warm. An air conditioned garage is not a good place to avoid flatspots.

Avoid H and higher speed rated tires. The problem here is that even some S and T rated tires have nylon cap plies. Plus, the higher the speed rating, the less likely a tire is to fail. In my estimation, unless you have a severe problem with flatspots, you should use the speed rating specified by the vehicle manufacturer on the vehicle tire placard. (many tire shops won't put on tires of a lower speed rating for safety reasons.)


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Re: Flat spotting question [Re: wag123] #5205452 09/05/19 02:43 PM
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RyanY Offline OP
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Originally Posted by wag123
Just go with CS5 Grand Tourings for the Odyssey. I have them on my Sienna and IMO they are just as good as the Michelins I had on it previously, for a third less money. They are 60 series T-rated tires, they ride smooth and quiet, they do not flat spot, and they are manufactured in the USA. After one year and a couple of long road trips, I have had no issues with them.

I just saw that I never responded to this. I will definitely consider the Grand Tourings. They were on my radar but I have no experience with them. Do you know how they compare to General Altimax RT43? I just got a verbal rec fo the Generals from a fellow Ody owner.


2007 Cadillac CTS 3.6L >127k miles (Castrol Magnatec 5W-30 + ACDelco PF2129G)

2012 Honda Odyssey EX-L >103k miles (Pennzoil Platinum 0W-20 + Fram XG7317)
Re: Flat spotting question [Re: RyanY] #5205938 09/06/19 06:32 AM
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wag123 Offline
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Originally Posted by RyanY
Originally Posted by wag123
Just go with CS5 Grand Tourings for the Odyssey. I have them on my Sienna and IMO they are just as good as the Michelins I had on it previously, for a third less money. They are 60 series T-rated tires, they ride smooth and quiet, they do not flat spot, and they are manufactured in the USA. After one year and a couple of long road trips, I have had no issues with them.

I just saw that I never responded to this. I will definitely consider the Grand Tourings. They were on my radar but I have no experience with them. Do you know how they compare to General Altimax RT43? I just got a verbal rec fo the Generals from a fellow Ody owner.
When I purchased the Coopers I did not consider the Generals because I have an aversion to them based upon many bad experiences with them in the past, so I can't answer your question. What I can tell you is that I have had many good experiences with Cooper tires going back over 45 years, including the Grand Tourings that I currently have on my Sienna.

Re: Flat spotting question [Re: Quattro Pete] #5205982 09/06/19 07:38 AM
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Originally Posted by Quattro Pete
Originally Posted by IndyIan
How long do they stay flat spotted? I had a set of high performance summer tires on the Focus that would thump for about 1-1.5 miles on the hwy,

The Contis on my 530i wobble for about the first 3 miles or so. That's about half of my commute.



Same for me, except it only seems to happen on the Mustang and not the VW. I have the same tire (DSW 06) on both, and after a night of sitting I get some wobble from the Mustang but the VW is fine. I've just assumed the weight difference is the cause.


2015 Mustang GT
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