-
Michelin 315 tag tire issues
-
Jon, please help me understand how side force on a steer tire that is being turned to go around a corner is comparable to a tag axle tire that is staying in a straight line when making turns. I am not having any luck wrapping my head around the concept. Thanks!
1999 XLV X-6872, liberty #440 -
I, too, as a service mgr in the 70’s, was taught to keep radials in the same direction when rotated. Mine were, but I don’t believe it to be true anymore as I’ve switched direction on my Hoosier race radials on my BMW many times without incident.
I also believe at this point that, while I would rather blow out a tag than a steer for control reasons, the twisting motion to which the tag is subjected may be more damaging than steering.
After hearing of the 365 rotation failure, I’ve pretty much decided (at the moment!) the problem may be rotation as opposed to overloading or simply that the tag tires are the most seriously abused tires on the coach. Therefore, unless you need load capability, which I don’t, I’m now leaning toward installing 2 new 315’s on the tag leaving me with a 365/455/315 setup and no longer rotating.
-
joeselman:
How about posting a photo of the single 455s on your coach.
Thanks!
-
I will, but first:
1. The back ends jacked up because I’m fixing air leaks
2. I’ll have to learn how to post pictures.1999 XLV X-6872, liberty #440 -
When you do post the photo, please include some details. Wheels used, costs and other variables involved in the changeover, and what you think of the performance.
Could be something I’d consider if the laod range would carry the weight of my drive axle. Seems the weight is limited to 11700 per tire according to Michelin.
-
My drive axle weight is just over 20,000#. You’re correct that the limit is 11700#/tire. Actually, I believe some states enforce a 20,000#/axle limit (Ohio?). And remember to calculate for trailer tongue weights in the equation.
The reason I changed was an attempt to get more airflow over the brake drums/wheel seal area because of frequent wheel seal failures and high diff oil temps. It did lower temps slightly but I MAY have licked the problem with a different brand of wheel seal (fingers crossed—I’ve now gone 60,000K miles on a drive seal—new record for me!). I’ve noticed no difference in performance/handling. Price/mile of tires is close. I doubt that I would highly recommend this change to the average individual.
-
That’s interesting! Thanks for the input.
I remember having wheel seal failure with my ’96 XLV and several friends who had seal and bearing failure with drum brake equipped XL and XLV models.
New technology is always interesting to me – especially when it comes to the mechanical aspects of things. Must be the old service manager blood still in my veins. 🙂
-
I wish there was a way to measure the tire deflection or side forces on a tire. If the average IFS coach with typical axle weights is making a sharp turn it appears to my uneducated eyeball that the side forces on the steer tires is significantly greater than the side forces on a tag, especially since the typical tag might be carrying 2/3 of the weight carried by the steer.
If anyone wants to see side forces on a set of tires, watch a semi with a spread axle trailer make sharp turns while backing in or pulling out of a parking space, or watch a tri-axle fully loaded dump truck make a sharp turn. You can almost hear the steer tires screaming for help.
-
If side
force was the determining factor causing tires to fail as discussed in this
thread, even a new tire wouldn’t last under the same distress as experienced on
the tag axle. It has to be something to do with the wear pattern
initiated on the steering axle that the tire cannot tolerate when placed in a
ridged position on the tag axle. I.e.: wear pattern difference causing
excessive sidewall stress (one sidewall) caused by the uneven tread height exacerbated
by reduced air pressure required at the tag position.Come on Jon just admit that I could be right. 🙂
-
Grizz, I just cannot get my brain wrapped around your theory without someone who has a tag tire failure measuring tread depth across the tire to prove there was unusual sidewall loading.
There is one constant in our driving that almost always subjects our coaches to sidewall loading on all tires, and that is the crown in the highway. I know the vast majority of my miles are in the slow lane on interstates and because of that my coach is always leaning slightly to the right due to the crown. Perhaps our in-house expert on highway design, Express Bus can jump in and give the specs on the slope to the side, but regardless of however slight it is always there. That suggests to me that our tires can handle uneven side forces.
Bear in mind the steer axles even on a perfectly level highway are constantly subjected to a side load, however slight because the toe in is a nominal .13″. That means they are always scrubbing sideways even though the amount is slight.
-
Jon and others,
Typical slope in a tangent section of roadway is 0208″/foot. That would be .25 inch over a 12 foot lane. The slope is for draining water off the road surface. Typical maximum cross slope in a horizontal curve is 08″. That would be almost 1″ over a 12 foot lane.
Just for the confusion factor, on some old four lane highways the roadway was crowned at the center of the two lanes. The slow lane (#2), where Jon says he hangs out would be sloped down to the outside by 0.25″, while the inside lane (#1) where Tom rides would be sloped to the inside by 0.25″. So find an old four lane highway and fix your irregular wear by swaping lanes frequently!
As for the weigh transfer across the tread of a tire resulting from the slope, I’ll leave that calculation to others.
Log in to reply.