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Bad Valve Stems / CO2 Inflator
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I can’t wait to put this tire pressure issue behind me and start worrying about other important things like where to stop for dinner.
I haven’t yet weighed my coach as we haven’t moved from this spot. I’ll probably find a truck stop and CAT scales somewhere along the road on Friday as we head north on I-25 towards Wyoming and then west into Montana. I will follow the expert’s advice and put the coach on the scale backwards so that the rear axles get the right measurement. I drove another coach onto the scales in the normal (forward) fashion a while back and the weight ticket that I received didn’t make any sense. This was due to the the scales being setup to weigh 18 wheelers and their axle configuration. If anybody has any advice on getting accurate per-axle weights from Love’s please let me know.
As for how to make things known to the folks on my website, well, it’s been a struggle. One of the rules that I’ve regrettably learned to accept is that most of my users won’t read anything. In addition, the longer the article, the less likely people are to read it all. I could write “don’t do this or your radio will catch fire….”, and the next day I would still have as many messages from people who didn’t read the article.
What would be really outstanding is a “Coach Operations Manual” that could contain the vetted advice from the majority of PC users on things that are common to all busses, regardless of converter. Things such as maintenance tips, before-start checklists, tires, driving tips, and other common sense issues that we’re likely to encounter. Of course, someone would have to curate and categorize these things, and that’s probably where the idea will die, i.e. searching for a volunteer.
I think the key to making things known is to make them easy to find. People will either seek out information or they won’t, and there is little hope for those who fail to become thoroughly familiar with their coach. Sometimes, they will adopt the attitude of “kick the tire and light the fire”, and then if anything breaks, just “write a check” to make it all go away. I’ve met owners exactly like that, who couldn’t tell me the most basic information about their coach’s systems. They keep the repair shops in business, and for the most part, everybody is happy.
I’m not one of those guys and I do strive to know everything I can about my coach. I’m in my 4th year of coach ownership now, and my second bus. I’m still learning as something breaks on every trip. I’ve not had any tire troubles up until this year, however. The troubles have been slow leaks which we all know by now have been caused by the failure to install Equal filtering valve cores when the tires were mounted. I bought this coach a year ago and it came with 6 new tires that were installed immediately before I took delivery. I didn’t know about the filtering valve cores and now fully appreciate the issue. I’ve also written to the dealer who sold me the coach so that they’ll know about it in the future.
As for the pressures on my coach, I have a sheet from Marathon that says 125/120/90 however it wasn’t until yesterday that I began to question whether this coach originally came with 315’s on front. I do not know the answer to that, and am eagerly waiting to get weighed to find out. Oh, and I could call Marathon I suppose…..
Someone else wrote about temperature rise. From what I’ve read, 180 degrees is the redline. It appears that any time spent at or above 180 degrees is going to be highly detrimental. The highest I’ve seen, in 110 degree weather in Arizona, was 156 degrees. The tire, a front 365, was at about 110 lbs when we departed from Phoenix. The asphalt temperature was in excess of 125 degrees. The infrared thermometer is great and I use mine at every stop, every rest area, a couple of times per day.
Pressure rise seems to be on the order of about 10 to 15 pounds from cold stop to hot highway. I have seen pressures in excess of 130 psi on the front’s after taking off with 120 PSI cold. There doesn’t seem to be a logical way to add air to a hot tire and figure the correct pressure. Topping off a hot tire to the “cold” pressure will result in safety for the moment, but it will then be underinflated in the morning.
I’ll be a very happy camper if I find out that my fronts will run at 110 instead of 125. I’m pretty sure that the 315’s on the drive axle are supposed to be at 120, and I’d say that replacing them with 455 super singles at 105 lbs would be sweet. Not now, however, as these tires are only a year old.
Also, it seems to me that if one were to inflate all his tires to the maximum rated pressure as depicted on the sidewall that such practice gives a margin of safety when other factors, such as axle weight, are unknown. The Prevost maintenance supervisor agreed with me on that fact and went on to say “that’s okay if you don’t care about the ride”, or on other words, it’s a harder, rougher ride with full inflation. Granted, I’m sure that the Michelin inflation tables also consider other factors such as tread wear and road contact, etc., but when the tire is operated at its rated pressure on an axle that does not exceed the rated weight, you will not overheat the tire. Heat is what kills these things and avoiding it is key.
So, I’ve already written too much and to those of you who’ve made it to the end, thanks! 🙂
-fred
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Fred, I just got back to the bus and read the info on Prevost Community. Your bus came with 315’s and that is likely why you are getting told 125 from Marathon. I normally run 105 in an XLII with 365’s and 110 in an H345. you should have filters on your stems, and that is what I thought you were having problems with. I carry a pressure doubler that let’s me have 240 psi from my coach air. I know that air is dry. Truck stops, and tire stores are notorious for having water in their lines. That may be what has caused corrosion in the valve cores. We had lunch in Creed on Monday, and we are heading to Taos in the AM. I hope you and Robin are having a great time.
Steve -
Fred
I am going to defer to others on most of your last post… where I might be able to help a bit is the best way to scale out. Here is what I did after a couple of bad attempts… after fueling I went in and talked with someone at the counter and explained I have a bus and I am trying to get three different weights…. They watched for me and then talked me thru it on the speaker as they can monitor real time what weights are showing on each plate of the scale… so we adjusted back a forth a bit and then we got a ticket that was reflective of what the coach weighed. I would suggest doing it with full fuel and water at what you normally run with… in our case I keep 40% fresh and always start the day with black and grey empty. Additionally if you have a towd with you I would drop it prior to the scaling… it just makes things more difficult and it’s easy to get the GVW of any car if you need it. I must of missed the post above where someone said to back on the scale… But I wouldn’t advise that as you won’t be able to hear what they are saying from the seat. Good luck
Bill
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I’ve weighed all three of my coaches and always drive on forward. Even with 2 45s and a 40 I was always able to get each axle on a different scale section. I could always see from my mirrors so I never needed anyone to help.
If your drive axle is in the 20 to 22,000 range your tire pressures are going to be close to 85 or 90.
If you do have moisture in the tires the Equal has clumped up and needs to be replaced with dry Equal and then fill with air that is moisture free such as the coach will provide. My aux system with the engine running gives me ample pressure to top off a tire.
As to filling a hot tire if you have to do that, it is best to anticipate the need, get your hot pressures on tires that have been driven hard for each position and use them as the pressures to use when hot. The problem is how hot is hot because as is noted ambient temperatures play a role in tire temperature and tire temperature affects the hot pressure. The 156 degrees on a 110 ambient day is not surprising in view of me seeing 135 on a 85 degree day, with higher or lower temps based on ambient.
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Bill what were you wieghts? Just like to compare.
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Fred,
Steve solved the tire pressure as suspected and if your heading up I-25 one exit south of I-70 near Cheyenne, there’s a Loves that you can weigh (and use your PC Loves card for .10 discount I may add). Just call the fuel desk from your phone, you can’t reach the button or speaker at the scale and tell them your a private coach. Then just split one of the platforms between the tag and drive with the steer on a different platform and that will give you 3 weights, it’s very easy. My H is heavy and with 365’s front and tag, my pressures are 105/95/85 per Michelin.
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Checking my tire Temps, I noticed that my last trip, while pulling a stacker, at 65 mph on a 90 degree hot day, that my drive temps were reading 140 degrees on the outsides. The inside drives, were reading 165 degrees. I am assuming, that being that the insides are not as much in the air flow, and, they are closer to the disc brakes, is why they run hotter. Has anyone else noticed this? The tire pressures are the same, inside and out.
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As to a manual for things owners need to know I suspect that falls into the area of responsibility Prevost has.
As owners we have different opinions about things, and not all of those opinions are consistent with what Prevost publishes in their owner or operator manuals. We all fudge some things. For example Prevost calls for brake chamber changes every year or 100,000 miles whichever comes first. I know nobody that does that. But we really can’t pick and choose. I would not want to bear the responsibility to create an owners list of stuff to know because I can see that leading to a lawsuit sometime down the road. I would and do consider the Prevost publications to be the final word.
The motorhome owners manual as published by Prevost is the best example of brevity I have seen in a long time. It basically says about wheels and tires to make sure the lug nuts are tight (450-500 ft. lbs.) and to inflate the tires to the recommended pressures. It does not specifiy the pressures or how to determine what they should be. My suggestion is to ask Prevost to correct their manual. Then the real challenge is getting owners to actually read the owners manual. I believe there will be peace in the Middle East before owners read their manuals.
https://secureus5.volvo.com/technicalpublications/pdf/MTH%20Section10-Care%20and%20Maintenance.pdf
See page 92
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My inside runs hotter also Jerry.
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Pressure Pro’s would have alerted Fred to his leaking tires…
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JIM
Please elaborate. If the valve stem fails (common when folks add extensions to them) all pressure will be lost. If a valve stem failure did not cause a loss of air, then there is a “check valve” internal to the tire that would prevent air loss, but it would also prevent the ability to check tire pressures.
Are you talking about valve stem caps with the fill through cap feature that provide a second seal? -
I’m not trying to sell that particular brand of valve stem cap, but I have used them for about 10 years now and they not only have made checking pressure and airing up the tires much simpler, but my air loss in tires has dropped to almost nothing, an indication that conventional valve cores with typical valve stem caps do not offer that second seal and therefore permit air leakage.
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We got weighed today.
A talked to the attendant prior to weighing and they couldn’t offer even the slightest advice. To them, the CAT scales are a hammer and every vehicle that enters is a nail. They knew less than nothing. They said that there were three weighing pads and so I should pull up accordingly, or however I wished. Luckily, I was able to do just that and split the drive and tag across two pads, and the front axle on another pad, thanks to the painted lines. Unfortunately, I had to leave the Toad attached, however it’s weight is well known: 4000 lbs, so, I just subtracted it from the final tag weight since it and the tag were both resting on the same scale pad.
The weights were:
Front: 17880
Drive: 21920
Tag: 14420 (or 18420 minus the 4000 lb toad)
Total: 58220, or 54220 minus the toad, which is the weight I expected (54K).
According to the Michelin charts, at 17880 the Front 365’s should be at 105 PSI. The drive axle 315’s were loaded to 21,900 lbs which is below the lowest weight on the chart, which was 23360 lbs at 85 PSI. I can’t really imagine 85 PSI for the drive axle. It seems way too low.
The tag axle also came in at 105 PSI on the Michelin chart.
So, it’s looking like 105 all the way around might be a good choice. I’m going to deflate the tires in the morning when they’re cool, and start out on a fresh day (350 miles) of driving.
Also, note that we all love Michelin and consider their charts to be gospel. Their docs say that tires in RV service should be replaced after 10 years. The consensus around here seems to be 5 years, or 7 max. Hmmm.
-fred
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Calll me old-fashioned, but I think topping up a hot tire is nuts! There’s really no way of gauging how much your newly added cold air will expand in a hot tire. Don’t do it! To me this is a far greater safety risk then driving on what may be percieved as an underinflated tire. Cold air into a hot tire can result in an explosion.
To the admins of PC, two or more times in this thread the idea of search has come up. PC needs a better search facitlity. Please take ten minutes and implement google’s free site search. If tire safety is as important as you say it is then the risks of google (if any) are worth it.
Sticky’s also came up. The idea of having a set of threads that are always at the top of the heap is sorely needed. There’s a wealth of information that can be culled from a forum and put at the top of the forum in the form of a set of sticky threads.
Weighing a coach reliably comes with experience. Stop at as many weigh sites as possible, weigh as often as possible, get a feel for how your coach weight changes as you deplete fuel and fresh water and add waste water. The only way to do this is to weigh often.
If Michelin says 100 psi for a 365 to support 17500 lb, then why do we add 5 psi? Trust me, Michelin already has their safety margin built in.
And Jon, why do you measure tire temps at the center of the tread when the most highly flexed portion of the tire is the sidewall about an inch from the tire shoulder? The sidewall is where a failure is most likely to start.
Lastly, inside duals always run hotter, this is because of the crown of the road. Many operator’s install Crossflow’s to even out pressures.
Google search! Let’s do it!
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We’ll leave the google search discussion for another thread and another day.
But a couple of comments. Fred, add whatever you want to what Michelin says to your drives. You are far better off than if you have less. Just be aware it is not needed and is likely to make the ride in the rear a little harsher.
David brings up some interesting observations. I can envision someone with a small leak adding air to a hot tire. I have done it to get home to service. If a tire leaks a small amount such as 10 PSI in 4 or 5 hours and it needs air, the tire on the opposite side has the hot air pressure to use as a guide. Not precise but as long as an excess of air is added such as 10 PSI over the hot good tire pressure the tire with a leak is safe to drive on. I don’t understand how adding air to a hot tire can create an explosion, but I do know running with low pressure can.
I check the tread because I can get my IR gun to read the center of the tread on all tires so all my readings are consistent. It is unlikely a sidewall is going to be so significantly different from the tread that I will not detect a low pressure tire. When I do check the visible sidewalls they are a little different than the treads but not so much as to be way out of line.
As to the crown causing the inner dual to be hotter. I disagree. I still cannot say my inner tires are exactly the same temps as the outer dual, but they are within a few degrees. Less than 5. I think less than 3 from what I remember. Any difference I attribute to less air flow beneath the coach wiping across the inner tires than the outside tire. Roads are crowned. Lanes are not. If the lanes were crowned there would be a puddle between lanes after a rain. If the roads are crowned it is to create a slightly high spot between the lanes which then slope down from that point, or one side of the lanes is higher than the other to promote drainage. To exaggerate if the lane was crowned only the inner portion of our treads would contact the surface causing unusual wear so I have to disagree that somehow our inner tires are always going to run hotter because a crown in the highway surface has them carrying the load. If that were the case our charts would be asking for higher pressure on inner tires.
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