Michelin Agilis confusion??

[JetstreamAS]

Originally Posted by dznf0g

Although they do only show a single106mph speed rating (same as most all of the other sizes, and C-metric). And don't say if that's at 80 or 90psi. Not that mine will ever see anything north of 65mph, but it's still a mystery to me.

Solve the dilemma by buying the Agilis C-Metric next time and you also can then run at a far lower PSI for the same load without the punishing 80 PSI beatdown on your Airstream.

[dznf0g]

Originally Posted by JetstreamAS

Solve the dilemma by buying the Agilis C-Metric next time and you also can then run at a far lower PSI for the same load without the punishing 80 PSI beatdown on your Airstream.

Ok, again...there is no delimma. I was asking all this from a knowledge standpoint. The most I ever have on my tires is 2100#. Since I don't think there has been an AS ever produced (maybe the slide models?) with more than 10k GVWR. (Minus 1k on tongue) leaves 2250# available load for tires. C-metric is never REQUIRED. There is still 430# of headroom available, per tire. BUT, additional pressure 10psi is needed...IF one loads to axle capacity.....which means you are overloaded per gwvr.

If one WANTS C-metric, that's fine, but not necessary.

[JetstreamAS]

Originally Posted by dznf0g

I recently installed Agilis LT225/75R16 (NOT the "c" designated commercial tire) on the AS. The sidewall for that size, in LT denotes 2680# @ 90 psi. That size differs in max pressure from all the other sizes (LT) and I found reference to a construction difference in that size.



All the charts for the Agilis only cover 2680# @ 80psi. So what do I do when trying to determine the proper pressure at lower loads as installed on my AS? Do I just add 10# psi to the current charts which designate 80 psi max?



Apply a percentage difference to the charts??



Has anyone dealt with this?

Your first post is above. Subsequent posts were similar.

Originally Posted by dznf0g

Ok, again...there is no delimma. I was asking all this from a knowledge standpoint. The most I ever have on my tires is 2100#. Since I don't think there has been an AS ever produced (maybe the slide models?) with more than 10k GVWR. (Minus 1k on tongue) leaves 2250# available load for tires. C-metric is never REQUIRED. There is still 430# of headroom available, per tire. BUT, additional pressure 10psi is needed...IF one loads to axle capacity.....which means you are overloaded per gwvr.



If one WANTS C-metric, that's fine, but not necessary.

The questions you presented and the time you took to ask more questions on this issue did in fact show you had a "dilemma." A few definitions for a dilemma:



1. A situation that requires a choice between options that are or seem equally unfavorable or unsatisfactory.



2. A problem that seems to defy a satisfactory solution.



3. An argument that presents two alternatives, each of which has the same consequence.



Didn't say a C-Metric was "required" but suggested it as you can run at a lower PSI and there is not an “80/90 PSI” issue. I don't think most people run at max PSI for any tire, but I guess if that works for you then it works for you.

[BayouBiker]

Tires with higher load range at equal pressure generally accomplish this with thicker and stiffer sidewall and ply construction. So it is not a given a tire with higher load range inflated to carry actual load will be less punishing on the trailer than one with a lower load range also inflated to carry actual load. The null hypothesis would be the resulting damping will be the same.

[CapriRacer]

Originally Posted by dznf0g

Although they do only show a single106mph speed rating (same as most all of the other sizes, and C-metric). And don't say if that's at 80 or 90psi. Not that mine will ever see anything north of 65mph, but it's still a mystery to me.

By definition, the speed rating test is run at the rated load/rated infltion pressure.

So 80 psi.

[CapriRacer]

Originally Posted by BayouBiker

Tires with higher load range at equal pressure generally accomplish this with thicker and stiffer sidewall and ply construction. So it is not a given a tire with higher load range inflated to carry actual load will be less punishing on the trailer than one with a lower load range also inflated to carry actual load. The null hypothesis would be the resulting damping will be the same.

Ah ...... Mmmmm ...... Not exactly

Ya' see, the published load tables are a reflection of what the tire can theoretically do - and since there are different theories, you'll get slightly different answers. That means the difference between an LT tire and a C type tire with the same dimensions is the different value the formula gives - not an actual difference in construction.

What distinguishes the C type tire that has that apparently higher load rating is that the C type tire is tested at that higher load, so we know the tire design was tested at that higher load - and we don't know that for the LT equivalent.

Besides, it isn't a thicker or stiffer sidewall that makes the difference when a tire is upgraded. It's the rubber itself that has been improved.

Yeah, I know, this is kind of complicated and it's difficult to explain.

[BayouBiker]

Capriracer, I understand they use a different load chart derived using a different formula and have different test criteria. But are you stating factually that in this case the "C" Agillis and the "LT" Agillis are constructed the same using the same materials etc. that they are for all intents and purposes the same tire?

[dznf0g]

deleted

[BayouBiker]

I was told the 225/75R16C Agilis has a third steel belt. Checking the internet I find several references seemingly confirming this. So the C-metric for the tire in the size in question is constructed differently and more robustly then for the LT225/75R16. It remains unknown what are the spring and roll rates at pressure and thus which tire is likely to be more forgiving on a trailer.

[JetstreamAS]

Originally Posted by BayouBiker

I was told the 225/75R16C Agilis has a third steel belt. Checking the internet I find several references seemingly confirming this. So the C-metric for the tire in the size in question is constructed differently and more robustly then for the LT225/75R16. It remains unknown what are the spring and roll rates at pressure and thus which tire is likely to be more forgiving on a trailer.

It does not "remain unknown" at all, the C-Metric has indeed been "more forgiving" than previous iterations of the LT Michelins on our trailer.

[dznf0g]

Originally Posted by JetstreamAS

It does not "remain unknown" at all, the C-Metric has indeed been "more forgiving" than previous iterations of the LT Michelins on our trailer.

Can you give any quantifiable data to make that an absolute?

[BayouBiker]

I too would like to see the "known" spring and roll rates or any other proxy for a tires contribution to suspension spring moment for the c-metric Agilis along any same size comparable Micheline LT load range E tire. Alternatively if you have done some kind of objective test to directly compare the different tires that would be great. Until then, it remains unknown. This information will help clear up some of the remaining confusion surrounding the Agilis tires.

[JetstreamAS]

Originally Posted by dznf0g

Can you give any quantifiable data to make that an absolute?

Yes, my experience (as was stated above) is quantifiable and makes it an absolute - for me. I don't need data from someone else, but apparently you do and good luck with your analysis paralysis.

Your ongoing dilemma and thirst for a white paper to make you feel better about a prior choice or a future one reminds me of an article that a physician friend of mine was talking about recently when it came to off-label prescriptions. For years, the conventional wisdom was that Minoxidil (Rogaine, etc.) should be applied topically for hair loss. However, it has been known by many dermatologists for years that a small dose or Minoxidil administered orally is far more effective in combating hair loss. It is not FDA approved and it is prescribed off-label as an oral medciation. Little on this in the published literature and really no rigorous studies yet dermatologists all over the world know it works as do their patients.

Hmmmm........

https://www.nytimes.com/2022/08/18/h...oss-pills.html

Originally Posted by BayouBiker

I too would like to see the "known" spring and roll rates or any other proxy for a tires contribution to suspension spring moment for the c-metric Agilis along any same size comparable Micheline LT load range E tire. Alternatively if you have done some kind of objective test to directly compare the different tires that would be great. Until then, it remains unknown. This information will help clear up some of the remaining confusion surrounding the Agilis tires.

See above. There is no "confusion" other than what has been manufactured in these discussions that simply never end.

[BayouBiker]

Subjective experience with tires and apparently prescription remedies are qualitative as opposed to quantitative. It's a shame really.

[JetstreamAS]

Originally Posted by BayouBiker

Subjective experience with tires and apparently prescription remedies are qualitative as opposed to quantitative. It's a shame really.

Not at all, but "analysis" like this does help your quantitative post count.

Bravo.

[dznf0g]

Let's back up the horse here. The reason for my own raising of tire questions arises from my observation on the forum that there seems to be a subset of new(er) folks who are seemingly running (whichever) tire (non- ST) at pressures lower than they should per the margins prescribed by actual experts in the tire field.
It seems that some within that subset automatically assume that tire A, run at a lower pressure equals a softer ride. I am not convinced that is necessarily the case. I do believe that some (many??) Of these folks are simply using the "line 3, column 4" number which corresponds with known? Weighed? Axle(s) load, without applying the added weight margins needed for using an LT or C-metric tire on a trailer.....especially a dual axle trailer. Of course a too low pressure will soften the ride. Perhaps at the potential for tire failure and a lot of damage.

[CapriRacer]

Originally Posted by BayouBiker

Capriracer, I understand they use a different load chart derived using a different formula and have different test criteria. But are you stating factually that in this case the "C" Agillis and the "LT" Agillis are constructed the same using the same materials etc. that they are for all intents and purposes the same tire?

No, I am not stating that the 2 tires have the same construction. I am stating they COULD have the same construction.

In fact, they don't. The C type has 3 belts, where the LT has 2. The 3 belts is the way many tire manufacturers do their all steel construction - meaning steel body plies, in place of polyester normally used in LT tires.

BTW Michelin is not the only tire manufacturer to have a C type 225/75R16 121/120 LI. Unfortunately, Tire Rack doesn't seem to bring those up when you search by size. But Discount Tire does.

And just to be clear, the Michelin C type tire seems to use polyester in the body plies, not steel.

[dznf0g]

Originally Posted by CapriRacer

No, I am not stating that the 2 tires have the same construction. I am stating they COULD have the same construction.

In fact, they don't. The C type has 3 belts, where the LT has 2. The 3 belts is the way many tire manufacturers do their all steel construction - meaning steel body plies, in place of polyester normally used in LT tires.

BTW Michelin is not the only tire manufacturer to have a C type 225/75R16 121/120 LI. Unfortunately, Tire Rack doesn't seem to bring those up when you search by size. But Discount Tire does.

And just to be clear, the Michelin C type tire seems to use polyester in the body plies, not steel.

That is my understanding as well. Both have "similar" polyester construction, with the C-metric having one additional steel belt. How that affects load capability, ride quality at a given pressure and what other material/manufacturing processes are different.....who knows.
Again, what really concerns me, regardless of which tire is being used, is, are folks utilizing the pressure recommendations you discuss on your website.
I don't care which tire someone buys, as both have more than enough capacity (following your recommendations) for any 10k gvwr airstream ever produced.
For me, it seems your margins are very ample, and I saw absolutely no need for the extra margin on top of the liberal margins available with the LT.
After some 70k miles with LT tires run at 80 psi, I have seen no ill effects.
I think that there are far more ill effects caused by out of balance running gear than tire pressure (assuming proper pressures are utilized by your methodology)
..and of course, healthy axle rubber.

[hairyclive]

Originally Posted by dznf0g

I recently installed Agilis LT225/75R16 what do I do when trying to determine the proper pressure at lower loads as installed on my AS? Do I just add 10# psi to the current charts which designate 80 psi max?

Apply a percentage difference to the charts??

Has anyone dealt with this?

! way to check this is to run the tires over some paper and look at the pattern. If most of the wight seems to be supported at the centre of the the tire the pressure is too high. If most of the weight is supported at the edges the pressure is too low. Since you are running the tires at about 70% load 70% of full allowable pressure would be a good range to start at. If you find the pressure that gives the best contact patch a little wonky to tow, with too much side wobble, increase the pressure to stiffen the sidewalls.

https://kktse.github.io/jekyll/updat...footprint.html

https://www.enginebasics.com/Chassis...t%20Patch.html

Too much pressure will wear the centre of the tread out sooner and will give the trailer a harsher ride causing some extra frame and body flex.

There is lots of info on selecting correct tire pressure to improve handling and tire contact at the online racing sites etc.\

https://www.youtube.com/watch?v=sIB69wC9KAk

[tjdonahoe]

I’m happy with my 235/75/16 E defenders on our 13 31’ classic fully loaded 7800#’s on the axles…..I run 68#’s air