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XZA3 275/80R22.5 Vs. XZE


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#1 rga48

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Posted 03 June 2013 - 05:00 PM

I recently replaced my original XZA3 275/80R22.5 with XZE's.  I can not tell you how much safer I feel!  I feel that the XZA3 contributed to a severe under-steer problem.  This was most noticeable on a downhill turn to the right with the road slopping right to left.  The coach would change a whole lane before I could comfortably get it back under control. This provided many heart stopping moments especially for an unfortunate couple on a motorcycle.   I originally thought it was my air leveling system and had the senors checked but they were found to be working properly. Now that I have changed tires the problem is gone.  The only issue I had was that my 90 psi rear tire pressure (based on four corner weight) was too soft and was causing rear tire sidewall to flex in heavy crosswinds.  I increased pressure to 100 psi and solved the problem.


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Rich & Patty Abrams
Jupiter, FL
2006 Allegro Bus 40' QSP
2007 Jeep Liberty 4X4

#2 mandalay40f

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Posted 04 July 2013 - 07:52 PM


I recently replaced my original XZA3 275/80R22.5 with XZE's.  I can not tell you how much safer I feel!  I feel that the XZA3 contributed to a severe under-steer problem.  This was most noticeable on a downhill turn to the right with the road slopping right to left.  The coach would change a whole lane before I could comfortably get it back under control. This provided many heart stopping moments especially for an unfortunate couple on a motorcycle.   I originally thought it was my air leveling system and had the senors checked but they were found to be working properly. Now that I have changed tires the problem is gone.  The only issue I had was that my 90 psi rear tire pressure (based on four corner weight) was too soft and was causing rear tire sidewall to flex in heavy crosswinds.  I increased pressure to 100 psi and solved the problem.


Was the XZA3 Tires original with your 2006 Allegro Bus? I have a 2007 Mandalay (XC chassis with ZF IFS front end) that was in production in 2006 and came with the same tires. I have 36K and starting year 7 with side wall cracks showing up. Time to change tires. I have experienced the same under steer issues with downhill curves. Increased tire psi to 110F & 100R with some improvement but still not comfortable at certain times. I'm looking at the XZE type and would like to know how the ride is with them vs the XZA3's? Another thought could the under steer be caused by downhill roll on rear tires tail swing in the curve? Always have a 2004 Tahoe toad attached.
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#3 DickandLois

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Posted 04 July 2013 - 11:43 PM

Regarding the XZE tires, I notice less wandering using them on the front. They are more of a truck tire and have a stiffer sidewall.

My total coach weight is less then yours so I can not speak for how they would work for you.

We do not see any difference in the ride with them though.

 

Rich. 


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#4 mandalay40f

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Posted 05 July 2013 - 10:08 AM

Rich, Thanks for the reply.  To be comparing apples to apples.  Just curious if your coach has the ZF-IFS front axle with 14,600# load capacity.  My GVWR is 34320# with the ZF_IFS front axle.  The tires that you replaced I assume were the XZA3 275/80R22.5 LRH not the newer  XZA3 275/80R22.5+ Evertread tire.  My XZA3's LRH came from mfr. original in 2007 which are the ones I'm replacing.

 

Larry.


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#5 DickandLois

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Posted 05 July 2013 - 10:58 AM

Larry, The tires on my coach are smaller over all with a different axle. Your front axle weight is a good 5000 lbs greater them my setup.

What I wanted to let you know is that different series tires from the same supplier react differently to road conditions, loads and air pressure.

One needs to keep in mind the rim, dual spacing requirements and load range. The XZA3 series is a unique series and design.

Hope that Tireman chimes in with his extensive tire background.

 

Rich.


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#6 Tireman9

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Posted 05 July 2013 - 05:39 PM

Thanks Brett for the heads up.  With 7 different forums on my list to monitor and two blogs to write I don't always catch every post that has a question.

I do accept direct email (   tireman9   at   gmail  )and a notice that there is a post and you would like a comment would be no problem at all. By using the post to ask questions we can hopefully help others who have similar questions.

 

Now to the question.  I note that the understeer problem seem to occur in downhill travel. Do you notice any problems on uphill or flat road steady speed travel? 

I note mandalay40F has a Tahoe toad. Any idea on its total towed weight?

  **** & Lois do you have a toad? If so what is it?  Weight?

My response will be shaped by this information.

 

RE inflation. Glad to hear you have had the coach weighed to learn the "minimum" cold inflation. However I see no problem with running plus 10% as long as you are not going above the tire max as molded on the sidewall.

 

Will check back this weekend to see what info you can provide.


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Retired Tire Design and Quality Engineer (40 years experience).
Retired Professional race car driver.
Retired Police Driving Instructor.
Member, FMCA Technical Advisory Committee
Delivered Tire Seminar for RV owners & two seminars on Genealogy at FMCA Bowling Green 2009, Madison 2011,

Indy 2012, and Perry 2014

I am scheduled to present two seminars on RV Tires & Three on Genealogy at Redmond, OR  in August

See my blog www.RVTireSafety.com and subscribe if you want notice of new posts.


#7 mandalay40f

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Posted 06 July 2013 - 10:27 AM

Tireman9,

 

I have the understeer problem with down hill turns that are more in the  45 to 90 degree range with posted speed caution sign +/- 40mph.  Flat travel and up hill doesn't cause any issues.   It is usually followed by entering the curve while decelerating to posted speed so I'm thinking the tail swing with the toad pushing could cause the rear tires to roll which is when the understeer starts.  If speed is stable during the following horse shoe turns it performs much better.   


I have had the coach 4 corners weighed twice and traveling loads in the seven years are consistent.  Front axel is 12,600# and Rear is
20,500#    GVWR 33,100#   Allowable is 34,320#  Toad is 5,200#  GCWR is 39,520#  Allowed is 44,320#.  I have had alignment checks and are good as well as ride height and have Koni Shocks front and rear. 

 

I set my tire psi per load and temperature Michelin charts @ as close to a 70 degree day for base setting and added 5 psi to F & R to
F0-110psi & R-100 psi which has helped.  The  XZA3 275/80R22.5 LRH tires I'm replacing for age are discontinued and the replacement tires are XZA3 275/80R22.5+ Evertread. 


Short story I was wondering if the new Evertreads had any modifications over the LRH version that might help? 

 

Also interested in any pros and cons of using the  XZE's  for more stability and what was ride like.  


I'm happy with the existing tires as it rides like magic carpet with no vibrations or wobble but side walls started showing cracks.

 

 

Mandy40f

Larry


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#8 rga48

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Posted 06 July 2013 - 06:08 PM

When I was replacing my tires, I was told by the shop that 90% of the tires they put on coaches are XZE's.  I am currently on 49 day caravan in Alaska with many twisting and turning roads and I'm still very pleased with how well these tires have performed in comparison to the XZA3's.  Because of my past experience with the XZA3's, I'm still gun-shy of right-hand turns but as I get more confident my cornering has improved. 


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Rich & Patty Abrams
Jupiter, FL
2006 Allegro Bus 40' QSP
2007 Jeep Liberty 4X4

#9 mandalay40f

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Posted 06 July 2013 - 08:43 PM

Thanks for the update information.  I know that I'll never wear either tire out before they time out so that is not a factor in my choice.   I feel that the XZA3's are targeted for high way long drive wear and comfort and not twisty two lane and rougher road conditions, i.e. the back roads of America and Canada.   The specs. from Michelin kind of indicate this the difference in design.


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#10 chp007kd40

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Posted 06 July 2013 - 09:54 PM

Mandalay 40f I think you have this figured out correctly. I have the same chassis under my Itasca 40 DP with Z-1, 8.9 and about the same weight. I just switched from XZE to XZA3 all steer tires and I like the smoother ride. I do live in Northern Ca. and I'm in the mountains all the time. The difference is, I don't tow anymore and It sounds like that could be the difference between the two types of tires. David


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#11 Tireman9

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Posted 07 July 2013 - 11:44 AM

Larry, Thanks for the additional info.

While I don't think it is tire roll it is understeer that goes to oversteer (vehicle turnes more than you want) probably due to the toad pushing the rear of the RV to turn more after you are into the turn. The hint to this is the fact that is happend when going down hill when the toad may not be slowing down as fast as the coach. When I was racing I was pulling a 26' enclosed trailer with a Camaro and all our tools and support equipment. My tow vehicle was a 1-Ton dually w/slide in camper. I had electric brakes on the trailer with controller under the dash so I could gently apply the trailer brakes when there was a downhill sharp turn. This would immediately get things under control and the trailer was no longer pushing the truck.


Now your toad is lighter than my trailer relative to the total loading but 5,200# is still going to push a little and when the coach in long and at an angle it is easier for a lighter load to generate a larger leverage force.

Now how do we fix this?
Your tire sidewalls at 100+psi are pretty stiff so I don't think changing tires is going to make much difference but increasing the coach tire pressure will decrease the tendency. I won't get all technical with cornering coefficients etc but increased coach tire pressure gives the coach tires more control in cornering.

A lighter toad will generate less of this turning force in corners.

If you can apply the toad brakes lightly but not the coach brakes (as I could with my set-up) that will also improve things. Also slowing down more before you enter the turn will decrease the rear swing out.

I see you mention "70 degree day" but this does not apply to tire inflation and the load tables. Set your tires when they are not in the sun, are the same temperature as the surrounding air and haven't been driven on for at least two hours.

"Evertread" seems to be a marketing item aimed at long thread life which for most RV owners is not an issue.

RE Ride. I am not aware of anyone doing a controlled test to compare tire-A vs Tire-B.  Also based on my experience in evaluating hundreds of passenger tires on many dozen different cars it is not unusual to find Tire -C on vehicle X  is better than Tire-D  but when we test the same tires on Vehicle Q many times Tire-D is better than Tire-C.


Simply relying on what you felt with an old worn set vs a new set of tires is not a valid engineering comparison. In my opinion this is about as helpful as trying to compare your wife's chocolate cake vs your mothers or grandmothers.


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Retired Tire Design and Quality Engineer (40 years experience).
Retired Professional race car driver.
Retired Police Driving Instructor.
Member, FMCA Technical Advisory Committee
Delivered Tire Seminar for RV owners & two seminars on Genealogy at FMCA Bowling Green 2009, Madison 2011,

Indy 2012, and Perry 2014

I am scheduled to present two seminars on RV Tires & Three on Genealogy at Redmond, OR  in August

See my blog www.RVTireSafety.com and subscribe if you want notice of new posts.


#12 mandalay40f

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Posted 07 July 2013 - 07:46 PM

Thanks Tireman9 for the reply. 

 

Yes, over steer is the correct problem.  I will consider increasing the psi until I decide on which tire to get.   I mentioned the 70 degree temp  setting as it is the common psi line for the 110 psi and 100 psi.  I waited for a even 70 degrees and set the psi's  so it is easy in a cooler morning or warmer day to know what the tire pressure reading should be do to current temp reading on the temp chart.  I  use a temp gun and pressure gauge for checking when not in the sun and temp is even.  I use the Temp gun for walk around checks during stops checking for any over temp issues.   As for toad braking I use a air brake proportional  system to match the coach brake so I'm unable to induce any pre-braking, which sounds like a useful tool.

 

Larry


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#13 mandalay40f

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Posted 27 October 2013 - 11:22 AM

Thanks for all the post help!

 

I just want to report my first trip with the new XZE's v.s. XZA's 6 year old 35K mile tires.  Same mountainous road on a rainy/windy day wth same tahoe toad.   The handling was a definite increase in stability in cornering down hill turns and ride smoothness was very comparable, maybe old v.s. new tires.  The comparison in turns are using posted recommended mph signs.  I will try the same route without the toad and to compare toad pushing affect in the turns.  I felt straight freeway driving was steadier with less effect from road crown steering me.

Larry


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#14 rileylene

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Posted 21 April 2014 - 06:19 PM

Hello,

 

I have a 2009(built Oct 09) 37.5 Tiffin Phaeton with Michelin ZXA3's on it. They are 4 - 5 yrs old and just starting to get very small sidewall cracking and I always keep them covered and never put any tire polish on them. I see in this post that maybe the XZE's may be better.

 

What is the best tire for our coach, we do get some wandering on the road but the tires run very smooth and our fuel economy is good (Well for a house rolling down the road LOL).

 

We run 95 lbs in the frt and 98 in the rear. 

 

Thanks


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