New AI with flat spots

[Beemerman]

Our '19 AI has front tires that are impossible to balance......has anyone had luck with AS (or MB) giving them some help ($)with new tires. I know the chassis sat around for over a year @ AS, then quite awhile @ dealer......am I kidding myself? TIA

[GCinSC2]

No clue but the one resource that should confirm if a tire is unbalanceable would be a Hunter Road Force balancer. Pretty widely accepted as the buck stops here. They have a locator map on their website to find one.

https://www.hunter.com/gsp9700

[Belegedhel]

I have heard different theories about flat spots on tires. Some people claim that if you have a flat spot, then your only choice is to replace the tire. I have also heard that if you just drive a few hundred miles, the flat spots will work them selves out.

I inherited a Volvo that my father had used as a daily driver up until just before he passed. It probably sat (mostly) immobile for around 3 months. I drove it the ~1200 miles from Colorado down to Houston, and it was still vibrating when I arrived. Took it in for a tire balance, and they claimed that the tires had flat spots and the only option was to replace...

I would think that the tires would be covered under either the Airstream warranty, or the tire mfg's warranty--doesn't hurt to ask.

good luck!

[CapriRacer]

First, I don't think you will have much luck with the AS or MB, because the problem wasn't caused by them - it was caused by the dealer.

Nor do I think the tire manufacturer will be helpful either - same reasoning.

Second, some flat spots will work themselves out if you drive on them because they were fairly recently generated. But in your case, they aren't new, so there is a strong likelihood they are permanent.

So first try to get the dealer to replace the tires.

If that doesn't work, you could either replace the tires - or try a trick I think might work (unproven, so far) - and that is to drive on the tires with reduced inflation pressure (say 10 psi low). Drive for 10 minutes at highway speed, then reinflate, and drive 10 minutes more at a slower speed. The lower inflation pressure is to generate some heat, and reinflating them is to allow then to cool down in the more round condition.

[GCinSC2]

CapriRacer,

Would you comment on my suggestion that a road force balancer might be helpful pinning this down?

You’re a tire guy, I’ll value your .02$

Gary

[RidingmyRV]

There are many many question on this form about 15” with flat spots. So I want to write about my experience when we purchased our ‘15, 28’ INT at the AS dealership. When picked up the AS I tend to remember them saying to keep the tire pressure at 32 psi. So with me nodding on everything to get out of there I drove it home and put in the driveway. What noticed after walking around our new second home the tires looked under inflated. I got my pressure gauge went around and everyone was at 32 psi. So I looked at one of the side walls and the rating was max 65 psi. So I inflated mine to 55 psi and so far I don’t have problems. Knock on wood. I do intend to change to 16” because I can actually travel at 70 down the interstate. I also want to change my single AC to 16000 btu from the 13,500 btu. Well I don’t know if this is the case with all the problems with the 15” tires. Well there you have it. See down the road

[SeeMore]

Flat spot permanency is a usually a function of time. The longer a tire sits in a single spot it decreases the possibility of recovery to mandatory replacement. Short durations (~ 3 months or less) are typically just rubber compression which can rebound by driving and generating sufficient heat in the tire as mentioned above. Once the rubber compresses, the flattening transfers to the inner belts which Do Not recover.

Classic car owners use a product which is placed under the tire and has a curvature that allows the weight to be transferred over a larger tire section rather than just the 'contact patch.' Some product names include "ramp flatstoppers" or "tire cradles." They are costly when constructed properly so be careful of the "cheap" brands you will find on the net.

[CapriRacer]

Originally Posted by GCinSC2

CapriRacer,

Would you comment on my suggestion that a road force balancer might be helpful pinning this down?

You’re a tire guy, I’ll value your .02$

Gary

Thanks for the compliment. How about I give you a quarter?

There are a number of ways to determine if a tire has a flatspot using a Hunter GSP9700 RoadForce balancer.

The simplest one is a large force variation. While that isn't very conclusive, it is a good indicator. How much is large? Depends on the size of the tire, but anything over 30# is very likely a flat spot. Oh, and the wheel has to be subtracted out. (If you don't know how to do that, then don't bother reading the rest of this. It requires knowledge of the more obscure functions of the machine.)

But, the surest way is to look at the waveform. There is a function in the GSP9700 (or at least there was - it's been many tears since I last put hands on one!) that allows the operator to look at the RoadForce waveform - the actual force variation around the tire. It will look something like this:



The X axis is degrees around the circumference of the tire and the Y axis is the amount of force variation in pounds.

Note the inverted peak at 340°. It is much larger than all the other peaks - both positive and negative. What you are looking for is like that except it will have a flatten peak. That is what a flatspot looks like when traced out.

Very few operators of the GSP9700 know how to get the machine to give you the waveform. The only reason I know is that I explored the functions within the machine and knew that function could be useful in diagnosing a problem. You would never use that function except when doing a deep dive.

[GCinSC2]

CapriRacer,

Well how about that! It looks like its deep dive time possibly.

Many thinks for the explanation and graph. A trainer for Chrysler years ago told me that the Road Force balancer was the "tool" for diagnosing tire balance issues.

Gary