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Old 11-28-2022, 10:16 AM   #1
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Are these the right tires for my Class A?

I recently turned 60,000 miles on my 2018 Thor Hurricane 29M so I thought it was time to replace the tires.


The original tires were Goodyear 245/70 R 19.5 RV - 82 psi (cold). We were happy with those tires.


The place that replaced the tires told us the Goodyear tires were no longer available and recommended we go with Michelin tires. They told us in their opinion, Michelin was the better tire. We agreed to go with the Michelin's.


The new tires are Goodyear 245/70 R 19.5 XZE - 120 psi (cold).



Driving the motorhome with the new tires it seemed it was hard to stay centered in the lane. There didn't appear to be a lot of wind, but that can sometimes be hard to judge.


We noticed the new Michelin tires were installed at 82 psi cold, the same as our old Goodyear tires. I checked the new tires and noticed that the new tires are rated for 120 psi (cold).


So these are my questions:


Are the Michelin's the right tires to put on our motorhome? I'm concerned with the much higher cold tire pressure.



Should I run the new Michelin tires at 120 psi minimum? I ran the tires at the installed pressure of 82 psi from Knoxville to New Orleans and wondering if that could have caused the tracking in the lane issue I experienced.



With the much higher minimum tire pressure on the Michelin's, along with the issue i was having trying to stay in the lane while driving, it has me wondering if the Michelin's that were installed are the right tires for my service.


Thanks for any input!
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Old 11-28-2022, 10:26 AM   #2
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Spec tires are reportedly 245/70R 19.5G https://www.rvusa.com/rv-guide/2018-...an-29m-tr34771. Michlein tires are good..........I have Michelin XZE 255 / 70R 22.5H commercial truck tire on my motorhome. 120 psi cold tire pressure might contribute to poor handling and a stifffer ride. Suggest weighing the front and rear axles and set the air pressure at a safe margion above your axle load per the tire manufacturer's inflation / load table.

You might find theis article helpful: https://tsttiretalk.com/what-is-reco...or-rv-tires-2/
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Old 11-28-2022, 10:45 AM   #3
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I've been told that Michelin's have a squishy side wall, that leads to wandering.
If you have them in now, I'd try 100# all round.
120# seems like a LOT of pressure, and 85 does not sound like enough.
Car salesmen used to drop the tire pressure to give the customer the illusion of a soft riding car.
I run 100# all round in my Sailun's and don't experience wandering.

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Old 11-28-2022, 10:58 AM   #4
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You don’t want to go by what’s in the sidewall of the tire but rather the pressure recommendation of your chassis. The sidewall merely states the max the tire can go, but the chassis specifications should state the ideal pressure for its weight class. Not sure if the manufacture sticker is still on board but it should give you the numbers you’re looking for.
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Old 11-28-2022, 11:26 AM   #5
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You don’t want to go by what’s in the sidewall of the tire but rather the pressure recommendation of your chassis. The sidewall merely states the max the tire can go, but the chassis specifications should state the ideal pressure for its weight class. Not sure if the manufacture sticker is still on board but it should give you the numbers you’re looking for.

I understand what you're saying BUT, my original Goodyear tires showed a cold tire pressure of 82 psi which matches what is on the sticker near the drivers door.


The new Michelin's are showing a cold tire pressure of 120 psi. So I'm trying to figure out if the Michelin's are designed to run more pressure than the original Goodyears were designed for.


The installers set the Michelin's at 82 psi, but I noticed that it was really difficult to stay in my lane on the interstate.


Around Knoxville I increased the pressure to around 100 psi and it seemed like it drove a little better.


Now I'm wondering if for a test i bring the pressures up to 120 psi and see how it drives.
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Old 11-28-2022, 12:13 PM   #6
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Quote:
Originally Posted by Flyer15015 View Post
.....I've been told that Michelin's have a squishy side wall, that leads to wandering....
They also have cracked side walls that lead to premature replacement.
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Old 11-28-2022, 12:18 PM   #7
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Quote:
Originally Posted by KeysVal View Post
I understand what you're saying BUT, my original Goodyear tires showed a cold tire pressure of 82 psi which matches what is on the sticker near the drivers door.


The new Michelin's are showing a cold tire pressure of 120 psi. So I'm trying to figure out if the Michelin's are designed to run more pressure than the original Goodyears were designed for.


The installers set the Michelin's at 82 psi, but I noticed that it was really difficult to stay in my lane on the interstate.


Around Knoxville I increased the pressure to around 100 psi and it seemed like it drove a little better.


Now I'm wondering if for a test i bring the pressures up to 120 psi and see how it drives.
I see what your saying. I think 120 is still high for your coach but to satisfy your curiosity, try 110 and see if that feels any better.

Also keep in mind that new tires will always be more responsive on the road. So you are used to driving in the old tires which were worn. So after installing the new tires, the coach is moving around more. The difficulty to keeping it centered may indeed just be the responsiveness of new tires. You could also just put the pressure at the coaches recommended pressure and see if you get use l to it.

In the end you have to be comfortable with it, so try different variable and see what works best.
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Old 11-28-2022, 12:35 PM   #8
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Quote:
Originally Posted by KeysVal View Post
I understand what you're saying BUT, my original Goodyear tires showed a cold tire pressure of 82 psi which matches what is on the sticker near the drivers door.


The new Michelin's are showing a cold tire pressure of 120 psi. So I'm trying to figure out if the Michelin's are designed to run more pressure than the original Goodyears were designed for.


The installers set the Michelin's at 82 psi, but I noticed that it was really difficult to stay in my lane on the interstate.


Around Knoxville I increased the pressure to around 100 psi and it seemed like it drove a little better.


Now I'm wondering if for a test i bring the pressures up to 120 psi and see how it drives.
Your original tires were load range G, while the same size Michelin tires are load range H. The tire pressure to carry the same weight of your motorhome will vary between different brands and load ranges for the tires.

The link below is to the Michelin inflation tables for your new tires.

https://www.michelinrvtires.com/refe...tion-tables/#/

You need to at least have your axle weights to determine the proper inflation.

The charts tell you that 120# in all of your tires would support a total weight of 28,000#, that is 10,000# more than your motorhome weighs, so definitely not the right choice.

Getting actual weights and applying them to the chart, will determine the correct tire pressure, based on the weights for your motorhome, not testing or experimenting. The tire engineers already have done that for you.

The Michelin inflation table linked explains how they suggest to weigh your motorhome and apply your actual weight to their tables.

There are countless threads on this, each with 100's of responses. You can spend days reading those opinions, or use Michelins recommendations for their product and save yourself a lot of time and confusion.
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Old 11-28-2022, 12:36 PM   #9
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Sidewall Cold PSI is the PSI for the MAX Load Rating of the tire

Goodyear 245/70 R 19.5 RV
4540#@110psi

Michelin 245/70 R 19.5 XZE
4940#@120psi


Goodyear @82psi.....3700#
Michelin @82psi.......3600#

Air those Michelins up to 90psi COLD and try them
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Old 11-28-2022, 04:57 PM   #10
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Sound advice from Old Bisquit.



As others have explained, the 120 psi max load pressure isn't relevant; you only need to know and use the psi necessary for your actual weight (load). That's a minimum of roughly 85 psi for the Micheline XZE 245/70R19.5, so 90 psi gives you a bit of extra leeway.
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Old 11-29-2022, 10:54 AM   #11
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From topicstarter, I understand that he has 82psi on sidewall of old tires, then an exeption to the rule of G load, he had an E-load with an exeptional 82psi instead of the standard 80 PSI.

So first I want to read from topicstarter what it is.
In post #5 he also comfirms it.
If so, the Michelin needs mayby even 10 to 15 psi higher for the same weight on tire.

You can also determine it from start, with use of GAWR's or better real weights.
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Old 11-29-2022, 03:37 PM   #12
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Made you a list for the new Michelins.
Found specifications in pdf from Michelin for RV tires
Gave also a F-load tire in that size AT 95 psi, so mayby also D-load existed once.

245/70R 19.5
Maxload single 4940 lbs AT 120 psi.
Maxload Dual 4675 lbs AT 120 psi.
Max speed of these semi truck-tires is mostly 75mph, but for RV sometimes 87mph.
For that speed the maxload is given.
Made the list for that max speed and give 90% of the loadcapacity calculated for the pressure.

Once determined that if 90% used of the loadcapacity calculated for 99mph that then max reserve with still acceptable comfort and gripp.
Mayby for a trucktire sooner discomfort.
But this means that even higher pressure can be used with still comfort.
And your goal is riding quality, and that is better at higher pressure, but comfort is also important, and that will get bad at the full 120 psi.

The list include the reserves and for weight on axle, so dont add reserves or devide by 2 or 4 yourselfes. I did the rocketscience for you.

If you want it per tire or axle/end, or other reserve, write it, and I make list for that.

Now only determine the axleloads acurate in your use. Succes with that , the most tricky part in it all, and your responsibility.

Axle Single/ cold psi/ Axle Duall/ max 75mph??
3217 lbs/ 40 psi / 6090 lbs
3582 lbs/ 45 psi / 6781 lbs
3946 lbs/ 50 psi / 7468 lbs
4307 lbs/ 55 psi / 8152 lbs
4667 lbs/ 60 psi / 8833 lbs
5025 lbs/ 65 psi / 9511 lbs
5382 lbs/ 70 psi / 10186 lbs
5737 lbs/ 75 psi / 10859 lbs
6092 lbs/ 80 psi / 11530 lbs
6445 lbs/ 85 psi / 12199 lbs
6797 lbs/ 90 psi / 12865 lbs
7148 lbs/ 95 psi / 13530 lbs
7499 lbs/ 100 psi / 14193 lbs
7848 lbs/ 105 psi / 14854 lbs
8197 lbs/ 110 psi / 15514 lbs
8544 lbs/ 115 psi / 16173 lbs
8892 lbs/ 120 psi / 16830 lbs
9238 lbs/ 125 psi / 17485 lbs
9583 lbs/ 130 psi / 18139 lbs
9928 lbs/ 135 psi / 18792 lbs
10273 lbs/ 140 psi / 19444 lbs
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Old 11-29-2022, 03:57 PM   #13
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Some like to answer this often discussed topic with a lengthy discussion. Weigh the loaded coach, consult the correct Load Inflation Table for the tire you have. Set the pressures to the charts recommendation plus 5-10% for a convenience factor. It's such a simple task and doesn't have to be complicated.

Read what the only known certified tire expert on the forum has to say here:

https://www.irv2.com/forums/f258/jus...ml#post3850777
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Old 11-29-2022, 04:15 PM   #14
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Originally Posted by Crasher View Post
Some like to answer this often discussed topic with a lengthy discussion. Weigh the loaded coach, consult the correct Load Inflation Table for the tire you have. Set the pressures to the charts recommendation plus 5-10% for a convenience factor. It's such a simple task and doesn't have to be complicated.

Read what the only known certified tire expert on the forum has to say here:

https://www.irv2.com/forums/f258/jus...ml#post3850777
X2 to that. I'm no tire expert, but after having my Michelin XZE's installed I simply consulted the Michelin tables for that tire and set the cold psi accordingly. As long as you know the approximate load on each axle, set it and forget it. Your tires are never going to heat up anywhere close to failure, too little cold pressure per the load however is a big problem. The larger the patch ( the tire-road contact) the greater the heat buildup from friction, a soft tire will heat up and fail long before a slightly over pressure tire ever will.
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