Been soldering on while we've had a few issues here and there this summer.
Anyway I measured my tires coming back to MN from the Dells with an IR gun as part of my walk around during stops. I measured my steers and tags around 105f, my drives where 135f , I'd expect them to be similar.
I run my fronts at 110 psi, and my rears around 100. I did have full water tank but empty waste.
Is this cause for alarm? Should I push my drive tires up some?
I'd first get an accurate weight by axle. Better even if you can find a scale to weigh the end of each axle, but at least you should know the weight on each axle when the coach is fully fueled and loaded as you normally travel.
Once you know the weight on each tire, you can use the manufacturer's inflation charts to calculate the proper inflation for the tires on the axles. I follow the recommendations of http://www.rvtiresafety.net/ and here is a link to a post of his that details how to determine the proper inflation using axle weights and tire inflation charts for anyone interested: http://www.rvtiresafety.net/2018/06/setting-motorhome-inflation-for-newbie.html
After the tires are set at the recommended pressures, then I'd say it's time to try and figure out the reason for a temperature difference. Might be due to a benign reason like the weight difference on each axle, might be because of the way the airflow is under the coach, or it might be something more serious like a problem with the axle (bearing, brakes, etc.)
Heat from engine, trans, brake drums, and drive axle, also restricted air flow will cause higher temps than front. Did all 4 dual tire temps equal?
If the temp was the same on both sides of drive axle don't worry about,the drive axle carries the most weight on all buses so they run warmer. It has always been a practice if you can touch a tire with your hand it's ok.If you follow the inflation chart on your bus and forget about all the axle weighing crap your tires will last longer and the bus will be happy to
Quote from: luvrbus on August 18, 2018, 06:52:59 AM
If you follow the inflation chart on your bus and forget about all the axle weighing crap your tires will last longer and the bus will be happy to
How is it possible to follow the inflation chart on your bus if you don't know how much the axle weighs?
Sorry to disagree, but the chart that came with my bus was calculated for bias belted tires, not modern radials, and there is no way I'd trust it to set the pressure on the Firestone FS400 tires on the bus at the moment. It takes all of about 10 minutes to run a bus through the scales after fueling, and then it's pretty simple to follow the tire manufacturer's inflation chart based on the actual weight the tires are carrying.
Quote from: richard5933 on August 18, 2018, 08:56:06 AM
How is it possible to follow the inflation chart on your bus if you don't know how much the axle weighs?
Sorry to disagree, but the chart that came with my bus was calculated for bias belted tires, not modern radials, and there is no way I'd trust it to set the pressure on the Firestone FS400 tires on the bus at the moment. It takes all of about 10 minutes to run a bus through the scales after fueling, and then it's pretty simple to follow the tire manufacturer's inflation chart based on the actual weight the tires are carrying.
They all sell tires all manufactures will tell you a fully inflated tire will wear longer and improve the fuel mileage. lol and they all tell you if park for long periods of time on concrete place a board under the tire how many people do that.
Folks do what they think will work best and in the trucking and tour bus world they don't care about weighing each axle the chart is their bible and they get 100,000 miles from a set of tires @ 70 mph
I have a Teltex weight gauge in my bus I can sit in the seat and watch the weight change and no way am I going to adjust tire pressure for a weight difference JMW I don't care oneway or the other what people do I do what is best for me the 315/80/22.5 costs a lot and I run just below the max loaded or empty
I see my drives are rated at 125PSI... I think I'll push them up and see if I notice any change.
People weigh their coach, check the tire charts, set their tires to the recommended pressure at 85 to 90 psi or so. Then after driving it, they don't like the squirmy feeling, then raise the pressures to 100 to 110. If you notice, almost all use that pressure range. Only ones that go higher on front or rear have pretty heavy rigs, close or over rated gvw, especially on front axles.
Neodaddy, hit a pothole with them at 125 and then put your fillings back in.lol
If you weigh all the axles on a bus if you go by the tire manufactures pressure chart and not the bus manufactures chart you will be buying new tag axle tires in hurry.Tag axles don't carry a lot of weight but they take a higher PSI so don't always believe what you read on a chart supplied by a tire co.You guys with the 2 axles buses maybe can get by
Don't know about those with a third axle - never had one and don't want one. Always driven two axle coaches and buses. Here's the chart that is in the Operator's Manual for our 4108a. Even using the GM chart that came with the bus, you'll need to have some idea of how much weight you're carrying. I'm also posting a piece of the Firestone chart for the tires currently on our coach, FS400.
Now factor in the vast difference between the tires that are the subject of the charts (bias belted) and those on most buses today (higher pressure radials) there's no way I'd use the GM bus charts. The max on the GM chart is 100 psi while the max on our FS400 tires is 130 psi.
Based on our actual weight plus a safety buffer our minimum cold inflation is about 85 psi, but we run at 95 - 100 psi since handling at 80 psi was a bit too sloppy for my taste. No way I'd run at 130 psi unless I wanted to shake my teeth loose going down the road. Besides, running at too high a pressure can actually reduce traction, reduce tread contact area, and cause premature tire wear.
There is no need to readjust every time a few pounds are added - I weighed the coach with full tanks (fuel, water, and LP) and then add a small buffer for safety's sake since I know we're going to pick up more weight as we shop along the journey.
Richard , the cross belted bias tire and radial belted tires have always used the same air pressure when carrying the same weight with the same size tire, I feel bad for the Prevost and Newell people running 130 psi shaking their teeth out I run 125psi and don't have that problem and my DL3 rides excellent,it could be 9 inch wide rims take that away who knows and you can still buy bias tires
Richard, you need also to take in ply rating. 12 ply, 16 ply, 20 ply, load range g, h, j, k. Each has different load carrying capacities and at rated pressures which are different. Without looking, I'm thinking the bias ply tires were 12 ply in the GM manual specs.
Tire pressures are all up and down depending on whose opinion prevails. I would go with the opinion of the manufacturer of the bus who has an interest in the safe and efficient operation of the bus. I drove tanker tractor-trailers for a while, and my company required that each tire be checked physically each day, and the pressures recorded. They mandated that every position be set at 90 psi, which they judged was a good balance of tread contact for braking, and for mileage, even though the maximum allowed pressure was 110 or 120. My 1984 Eagle calls for 105 psi on the front, and 90 psi everywhere else. That level tracks well, and the ride is good. Whether going to higher pressures will increase mileage or cause a different wear pattern, I do not know, but I don't want to experiment with my new expensive Dunlop's.
Keep in mind that no matter what pressure you start out at, in just a matter of a few miles it will go up about 10-12% due to the tires warming up. :)
I guess what's confusing about all of this is the notion to just 'go what the bus manufacturer' recommends. The recommendations GM made were based on speed, load weight, and tire size. The charts gave a minimum psi and there was an allowable range above that. They made their recommendations based on the tires available at the time and with the bus intended for commercial revenue service.
According to the chart in the Operator's Manual my coach left the factory with G-rated tires, while I'm running L-rated Firestones at the moment. The Firestones also have a chart which is also based on multiple factors. The pressure I run is based on the load being carried as well as how the pressure affects handling, as I mentioned earlier. The pressure I chose does coincidentally fall in the range of pressures on the charts in the GM manual, so in a way you could say that I am following their recommendations if you wanted.
Pressure will go up in all tires as they are driven, but its my understanding that the engineers take this into account when they develop the inflation charts. Our TPMS does monitor temperature, but I don't focus on that too much unless one of the tires spikes differently than the others. Otherwise, all tires are inspected by me at the start of the day and periodically throughout the day when we stop for breaks.
"L rated" man that is a 20 ply tire
Quote from: luvrbus on August 18, 2018, 07:29:23 PM
"L rated" man that is a 20 ply tire
Yeah - that's what I thought when I first researched them. More tire than we need for certain. They came with the bus, were in great condition, and seem to ride nice. So we kept them. Now that I've grown to like them I'll probably get another set when we start replacing these next year. The guy we bought from was a commercial bus operator and I'm assuming he installed what he kept on hand for his revenue coaches.
There's no debate here. The only way to determine what tire pressure to run is weigh your bus by axle then refer to your tire manufacturer by your size and model and follow that tire pressure, period. Good Luck, TomC
LOL you loose a Michelin and ask for warranty the first thing they tell you is NO the air pressure was low BTDT to many times.I am not going to putter around at 55 mph from El Paso to Junction TX on I 10 I hit the cruise and go.I don't run the 80 mph speed limit and get passed a lot but I will run 70 to 72 mph without any fear with the higher psi
This board never fails in getting me to mutter WTF? now and then. It seems so dead logical to follow the inflation chart provided by the tire manufacturer for that specific tire and weight. Period, as TomF states. For a variety of common sense reasons, the number in the charts are the reference points for general use. One can make a case for some adjustment off those numbers based on road or weather conditions but just setting them all at some fixed range does not compute for me.
Ok Don, the manufacture that designed, built the bus and spent hours, days or months to make a safe and long lasting vehicle and placed a inflation tire pressure chart in each bus according to our government rules.
Are you saying that was a waste of time and all BS ? just use the tire manufacture chart.Open your friggn door on your automobile it has a chart,this is stupid adjusting a tire just for ride , the bus manufacture did their home work for stopping, driving in different weather conditions and wear on the chassis parts.I don't care what people run for air pressure it's their bus and money but it's the vehicle manufactures chart for me
Clifford,
I agree 100% that a tire inflation tag mounted to a vehicle is 100% accurate when the vehicle rolled out of the factory. In the case of a seated bus, I will assume the intended purpose is to carry passengers, like the mail, through snow, sleet, and sunshine on tires with specifications of the time.
The validity of that tag was based on these assumptions and after a few decades and significant modification, our bus conversions are configured and used in ways that differ from the original intent. So, are they still valid numbers I don't know.
The tire manufacturer prints inflation guides not knowing the specific vehicle running the tires, is that any more correct, I don't know. My gut tells me the current tire manufacturer producing the tires we run today are legally more on the hook that some 50 year old defunct bus maker.
If I had to place a bet, my money rides on the inflation guide printed by the tire manufacturer for tires specified to run on buses and heavy trucks.
I'm not arguing here or stating what is the right answer, just pointing out that there is a wide variety of opinion and stating mine with a bit of rationale.
One last thing, my criteria is safety first, ride comfort second, and durability/milage last. A commercial tour operator or others may have a different set or order based on their own needs.
Ok Don what changes ,the Prevost,Eagle,Vanhool and MCI conversion shells use the same inflation chart as a the seated passenger bus so where does it change ?.I don't know of any tour operators that screw around with tire pressure. I am all ears hoping to learn a reason
My 1968 Cutlass came with tire pressure recommendations of 24 psi front and rear. That was based on the factory-installed tires and tire technology available in 1968. Things have changed lots since then, including tires designed to run at higher pressures.
I drove this car for 30,000+ miles, mainly on high-speed freeways. I had upgraded to modern radial tires with recommended tire pressures of 36psi. Had I continued to run at the factory recommendation of 24 psi at freeway speeds, the radial tires would have likely overheated and failed early, perhaps catastrophically. Unless I was going to run retro tires made to 1968 standards it seems safer to have the pressures match the tires.
Following the logic of always obeying the factory recommendations just doesn't make sense, especially when tire technology has evolved so much since our coaches left the factory.
I think that a much better way to follow factory recommendations would be in the selection of the tire size & type.
The point is we are all dealing with different makes and models of buses, the tire manufactures chart does not work for all buses.some have tags,bogies,tag steering and IFS not the old straight front axle BTDT and it cost me
Clifford,
that is the point. With different vehicles running the same tire, the only reasonable variable to use is load on the tire. Thus the tire mfg. chart is based on that figure. The more weight the higher the tire pressure.
It's great to have different opinions and they are valued here. It seems like this one is about done though and no need to take it much more, clearly the different options to the bus num with a air pressure hose in hand is clear at this point.
LOL all I can say Don use the tire chart on your MCI tag and you will be looking for 2 tires ;D
Just got through the scales.
10,780 front
21,140 drive
31,920 total
what you missed the tag axle
the temps. you got on the front and tag are about the same as I have had on both the M C I and the Featherlite and the drives as well .
so long as the inner and the outer drives are about the same but for me some times the inner drive would be a little higher . wait until it is hot on one side due to the sun and cooler on the other side
I use the temp . gun on every stop when on the road and after a while you will be comfortable with the different readings . but if the temps. go way up then it is time for concern
dave
Quote from: sledhead on August 19, 2018, 02:37:27 PM
the temps...so long as the inner and the outer drives are about the same but for me some times the inner drive would be a little higher...
dave
When we started using the Tireminder TPMS, we noticed that the inner drives are about 5 degrees warmer than the outer. I figured it had something to do with air flow, and since both sides were the same I wasn't too worried. The temp didn't keep rising, but stayed consistently about 5 degrees higher inner vs outer. If one tire spikes different than the opposite one, that's a different story, I figured. Still pretty new to us, this TPMS thing, so I'm still establishing what 'normal' is for the system.
Inside hotter than out the outside is normal ,the inside wheel has a brake drum or disk brakes, out here in the west it's not uncommon to see a 20+ degree swing when coming down grades using the brakes a little and setting a TMP off.Most drivers out here know that happens and don't even stop to check
The weights from the scale are front axle and the rear axleS (both drive and tag). I just planned on taking the total weight of the rear and dividing by 6, assuming each tire carries about the same amount. Richard doesn't have a tag so cannot confirm temps of the six tires. Anyone else set the tires at the same pressure on the drives and tag tires and monitor the temps?
It seems to me that the tire manufacturers charts are guides as to what pressure is required to carry a given load, and what maximums are allowed. The vehicle manufacturer considers that as well, but also considers cornering, tracking, and vehicle stability going down the highway. Going by the tire manufacturers guide only misses the unique setup of particular coaches. In cars, the tire pressures can affect the qualities of understeer and oversteer, why not in coaches? Eagle might be gone, but I'm still going by what they said is best.
Nope, the tag suspension has a separate regulator, set doesn't change, the drives are aired by the leveling valve.
Very different weights, the tags are way lighter.
Drive the coach forward on the scale to get drives off the plate, and get a reading with the tags alone.
You'll be using the minimum rating for them.
Happy coaching!
Buswarrior
Quote from: windtrader on August 19, 2018, 05:08:02 PM
The weights from the scale are front axle and the rear axleS (both drive and tag). I just planned on taking the total weight of the rear and dividing by 6, assuming each tire carries about the same amount. Richard doesn't have a tag so cannot confirm temps of the six tires. Anyone else set the tires at the same pressure on the drives and tag tires and monitor the temps?
Will the typical truck stop with scales take 3 measurements, front, drive, tag? When I had it weighed there wasn't much issue with getting the two weights recorded.
Yeah I messed up. I've got 24 hours to do another weight in.
There were 3 pads, one for front, another for drives and another for the trailer. For whatever reason I figured "I better get the tags on the same platform as the drives".
In any case my PSI seems fine. Probably due to brakes and load the tires are running warm, but nothing outside of spec.
Part of this is still chasing better MPG. Gah, got 5.1 in Wisconsin recently with a toad. I've been keeping it near 60-63. I'm starting to think I need to go faster. When I cared less I got 6.3-7 mpg. I know these engines like to run 1700-1800 rpm if I'm correct.
While researching tire load inflation tables by various tire manufacturers a couple weeks ago for a FB thread, I found on three or four manufacturer's load inflation charts an *, which led to a footnote that basically said (paraphrasing here): "*These inflation guides are based on the Tire and Rim Association recommendations." TRA is the industry trade group, of which you have to be a member: http://www.us-tra.org/
Hmmm. . .
Further investigation discovered that nearly every manufacturer's tables were withing 5-10 psi of each other for the most common size bus tires, load ranges and axle weights (which are usually just labeled S or D for Singles or Duals.)
Interesting, eh?
FWIW & HTH. . .
;)
TIP: When weighing a three-axle bus, most CAT scale operators will allow you to pull forward just enough that the drives are off the scale but the tags are still on. That will give you the weight on the tags. (Helps to have a co-pilot to help spot you while doing this.)
Quote from: DoubleEagle on August 19, 2018, 06:33:19 PM
It seems to me that the tire manufacturers charts are guides as to what pressure is required to carry a given load, and what maximums are allowed. The vehicle manufacturer considers that as well, but also considers cornering, tracking, and vehicle stability going down the highway. Going by the tire manufacturers guide only misses the unique setup of particular coaches. In cars, the tire pressures can affect the qualities of understeer and oversteer, why not in coaches? Eagle might be gone, but I'm still going by what they said is best.
In theory I agree - tire pressure affects handling. But then how do we explain the chart that GM put into the Operator's Manual that came with my 1974 GM 4108? It lists pressures ranging from 50psi all the way up to 100psi. That's an awfully wide range of pressures, so I'm going to have to assume that their chart was based on weight loading more than anything else.
Quote from: richard5933 on August 20, 2018, 03:22:43 AM
In theory I agree - tire pressure affects handling. But then how do we explain the chart that GM put into the Operator's Manual that came with my 1974 GM 4108? It lists pressures ranging from 50psi all the way up to 100psi. That's an awfully wide range of pressures, so I'm going to have to assume that their chart was based on weight loading more than anything else.
Despite the overall level of pressures, I believe it is the relationship of pressures that affects handling. It always seems that the steers have a higher pressure than the rest of the tires.
One thing that amazes me with bus people they will buy tires that exceed the load limit on their wheels by 2 or 3k thinking they are safer.I show some read it on the wheel you have 7500 lb rated tire on a 5000 lb rated wheel what is the point here you wasted money.I saw some Chinese aluminum wheels 22.5 that only had a 4500 lb rating watch those
Quote from: luvrbus on August 20, 2018, 06:22:23 AM
One thing that amazes me with bus people they will buy tires that exceed the load limit on their wheels by 2 or 3k thinking they are safer.I show some read it on the wheel you have 7500 lb rated tire on a 5000 lb rated wheel what is the point here you wasted money.I saw some Chinese aluminum wheels 22.5 that only had a 4500 lb rating watch those
Now there is a combo to watch out for: Chinese wheels with Chinese Tires. :o
Getting near impossible to buy any tyres that aren't made in China here in Australia
Most brands now have them made there to the company's spec or they come out of Korea
Cooper is the only US sourced 4wd tyre
Bridgestone are from Japan, European brands can be anywhere including Mexico
But there again the Hummer H3 is made in China