Squirming Michelins

[harrysusa]

I replaced my 8 year old Michelin XRV with new tires of the same size, 235/80 22.5, earlier this year. I am running the same air pressure, based on the actual wight of the coach. Nothing changed except the tires.

My old tires drove just fine, no skipping around, affected very little by wind. The new tires act like I am being blown around by sidewinds, trucks & cars passing by, and I have to continuously drive the coach in a straight line.

At Indianapolis I asked the Michelin rep in the booth what is going on? He said "squirming" and it should go away in about 7000 miles!

I have never heard of this. Is this common with all new tires? Or are these Michelins defective?

Do I really have to continue driving an unsafe coach for 7000 miles?

Harry Salit

[vtbigdog]

Are you running a tag axle? What do you have for a coach?

What are your corner weights and how much air are you running in the tires?

[Beemerdude]

If you haven't changed any of the load characteristics, between the old tires and the new tires: such as more weight either side, front or back, any corner, tire pressures, etc, then the following applies. and even if you have changed some of the load characteristics you still have to consider the following.

New tires of any kind do not have the same characteristics as seasoned tires. Tires have to be seasoned, or in the case of race cars,they need to be warmed up and seasoned; that is why when you watch formula, sprint/Indy racing they weave back and forth on the track on the warm up lap before the green flag and why drag racers do burn outs.

New tire do not have the same grip because the compounds in the tires have not been energized if you will. The molecules in the tires have to bounce around hitting each other to generate the compounds into the desired results. This in the case of the Michelins as the Rep told you may take 7,000 miles. If you were to use the same tires on a PickUp truck and drive more aggressive it may only take 4 or 5,000 miles.

You may also notice a slight decline in fuel economy with new tires as they are not seasoned and they do not have the final desired compound reactions to the roads.

Also just a note; you and others may notice that when driving on newly paved roads, even with seasoned tires, that the grip and mileage is not as good as when traveling on seasoned roads.

For OPTIMUM grip and mileage, travel on seasoned tires, on seasoned roads. If you can find these conditions along with a perfectly level highway you will get the best economy: if you drive accordingly! But then again we do not live in a perfect world, so what you see and feel is what you get, until everything gets adjusted to your driving style!

ALL tires should be replaced when the warranty period ends. Because as per the Federal Law of the "Magnus Moss Warranty Act of 1975": (http://www.mlmlaw.co...es/undermag.htm OR http://en.wikipedia....ss_Warranty_Act): If a warrantied item fails and damages a non warrantied item/part, the manufacture has to pay for the damage to said parts: like fenders, air bags, wiring, etc. However, the warrantied item, in this case the tire, has to be presented for inspection to the manufacture's place of business. That means; pick up all of the tire pieces and take them along with what is left of the tire carcass to the manufacture's place of business/ factory dealer ( not just someone that sells the brand) even if you have to put the tire on top of your vehicle to get it there. The Mfg does not have to reimburse you for damages if you do not comply/do/follow this procedure!!

For more on the Magnus Moss act of 1975 just Google it! You are in their Ball Park and have to play by their rules: Not I don't like the rules!!!

The tires are most likely not unsafe, but If you slow down or don't drive as you would usually, because you "feel" they are unsafe, it will take longer for the tires to season.

Be safe, drive safe and look out for those that aren't driving safely or on the road with safe equipment!

AND most of all look out for people on motorcycles: especially those that wear black, which makes them very hard to see: because they blend in with the highway! Like tires; some riders have to be seasoned a few times, by hitting the pavement, that they blend in with; or a vehicle; before they wise up and wear High Visibility Clothing, that makes them easier to be seen !

For my credentials that may lend crediance to the creditably for what I have said; visit my profile. However the following has to be said:

Legal Disclaimer: What I have said is not to be taken as Legal Advice! Do your homework and decide for yourself and remember: "He said" does not work or count in any court of law!!

Safe Travels!

[harrysusa]

Hi Richard,

The coach is a 1997 Discovery, 37' total weight 22,150 lbs, in 2011 RVSEF, no tag.

LF 3800, RF 3900, RR 7300. LF 7150

Air pressure front: 95 psi, rear 85 psi, I also have a TPM.

I tow a 2006 Scion xB, weights about 2600 lbs.

The coach was loaded for this years travels similar to 2011.

I have recent schocks, track bars (last year) & bell crank.

Harry

[harrysusa]

Hey Beemerdude,

Thank you for the detailed reply.

No significant changes in coach weight from last year.

I did notice a drop of about 1/2 mpg this year. I was attributing it to head winds but looks like the tires were the culprit. So it does not pay to get new tires unless absolutely neccesary.

Are you saying if I warm up my tires like race cars do I wont have to wait for 7000 miles????

Anyway I do have 5000 miles on them now & happily the squirming has diminshed, but not completely yet.

There is always something!!!

Harry

[hermanmullins]

Harry, just consider it your alertness alarm.

Herman

[tireman9]

While I don't quite agree with everything previously posted there are a couple reasons for the loss in mpg and the "squirm" feel. I also do not feel the tires are "defective" as you are experiencing results that are seen in all tires.

Even if you were to take two sets of new tires that had the same heat history but one had most of the tread cut off, the tires with the shallow tread will deliver better fuel economy because the movement of the thick tread consumes more energy (rolling resistance) than the tire with less tread rubber.

Second it is well documented that the shallower the tread the crisper the handling. What you are really feeling is the result of tread element rubber bending and moving as you drive down the road.

Tire wear rate is not linear and the wear rate when new is faster than after a tire has worn some of the tread off.

For street use the only "seasoning" I would think is of concern, probably occurs in the first hundred miles or so. This is when the tread release chemicals used in tire manufacturing wears off. This is a very thin coating so I don't think you need to wait 7,000 miles. I believe the Michelin rep was trying to give you an estimate of when the feeling will get close enough to the old, worn tires that the difference will be almost unnoticeable.

[hermanmullins]

Tireman, Thanks for that answer. After purchasing 8 new tires . I thought it was just me feeling safer and was driving a bit faster.

I understand the problem that Harryusa was having and your answer sound reasonable.

Herman

[rcgoss]

Maybe Occam's (or Ockham's) Razor should be applied here. (Employ the simplest solution.) As an old tire guy myself (at the dealer side of the business) I'm sure the the tire guy is right on, but if you want to stop the "squirm" now, my experience says "PUT MORE AIR PRESSURE IN THE TIRES", but do not exceed the max. pressure allowed by the tire manufacturer. What you sense as "squirm" should stop. With the new tires the tread is still all there and quite pliable, it's not yet seasoned (gets harder as it seasons). The new tires should ride just fine at the higher pressure. After a 2,000 miles or so sufficient seasoning should have occurred to reduce pressures a bit without the "squirm" returning.

I put a set of new Michelins on our American Eagle last year and didn't experience any such problem, but then I tend to carry a bit more air pressure than absolutely necessary (still within the pressure limits set by the tire manufacturer). The ride has been fantastic compared to the Brand-X tires that they replaced and they are running great after about 15,000 miles.