Why have the axles weighed

Topic: Why have the axles weighed (Read 1693 times) previous topic - next topic - Topic derived from Re: Just Got Our Firs...

Why have the axles weighed

May 14, 2017, 06:59:29 am

Quote from: AKATheAlchemist – May 14, 2017, 01:00:21 am

@Old Phart Phred - Wonder screen name btw. Thanks for the tips. That will all go on my list. Just curious newb question... but why have the "Axels weighed"? And what's that even mean?

Pulled this question out and into its own topic for visibility. Here is a good explanation:

Wheel Position Weighing

Tire inflation is highly dependent on the actual weight of the vehicle being carried by the tire. That's why tire manufacturers publish load and inflation tables.

You load the coach as you would for travel, including all travelers in their regular seats. On a level surface, at minimum you get the weight of each axle (at truck stop CAT scales, etc). Better, get the individual wheel weights. Here are a couple of the larger services:

SmartWeigh

Weighing Schedule/Locations

Once you know your weights, you can inflate your tires properly, redistribute loads if needed, and be safer on the road

Michelle

Re: Why have the axles weighed (split from Re: Just Got Our First Foretravel)

Reply #1 – May 14, 2017, 08:41:11 am

CORRECT.

If you have 275/80R22.5 Michelins, for example, the correct PSI per the Michelin inflation chart (based on weight they are carrying) ranges from 75 to 120.

If the actual weight of your coach called for 120 and you ran 75, your tires would be severely overloaded and very likely to blow out.

If the actual weight of your coach called for 75 and you ran 120, you would feel each little bump in the road.

Until you do weigh (and, best to weigh individual wheel positions, as side to side loads are not perfectly divided) go by the GVWR plaque by the driver's area. It gives proper PSI if each axle is loaded to its GAWR (Gross Axle Weight Rating).

Re: Why have the axles weighed (split from Re: Just Got Our First Foretravel)

Reply #2 – May 14, 2017, 11:39:30 am

This last week when at OTM for repairs I was told by the tech my tires looked "over inflated", I was asked how many pounds I was running and I answered 95 front 90 rear...his reply was "that's to much, you should be running 85 lbs HOT. I was also told not to worry about weighing individual wheels as I have solid front/rear axles. Also, I was told the tires are radials and are designed to run a little "bulge" on the sides of the tire allowing the tread maximum contact with the road just as the radials on our cars. I don't want to get into the name of the tech and who said what but this tech has over 20+ years FT experience so after speaking with him I was again wondering if the tire pressures I had decided on were correct or not.
So, when I left OTM I drove to the CAT scales on the north side of town, just to see what I weighed. It was just me in the coach, all tanks were empty (well maybe 1/4 tank fresh H2O) half a tank of diesel, full propane. I understand this is not typical travel weight but I was after just some baseline info., will adjust and reweigh at another time. The scales showed 11340 lbs steer 19060 lbs drive. According to the chart given to me by tech., that is 95 lbs per tire front and 85 lbs per tire rear.
Now came/comes the question of "HOT". In all my 62 years of life never heard anyone state to fill the tires hot. But, and especially since installing a TPM system I have begun to question the hot pressure myself. On my last trip, the tire pressures jumped up about 8 to 10 lbs per tire as I drove along...so I was running 113 to 114 lbs., and yes at those pressures you do feel every pebble on the road, and the ride becomes stiffer. So I gotta say, to this noob the hot statement made a tiny bit of sense as if I were to set the, for example, front tire at 95 when hot then I am at the correct pressure for the load. BUT I understand the problems when the tire is cool, not being at the correct pressure until the tire gets up to temp., running in cold conditions etc., however the "hot" statement from the tech was/is not the first time I have ever wondered about if it. For me until I feel better about "hot" I will continue to test and fill cold.
Happy Mothers Day!
see ya
dave

Also if anyone is interested here are the alignment figures I was given:
Caster: Left 4' to 4 1/2' Right 4 1/2' to 5'
Camber: (not adj)
Toe: 1/16" to 1/8"
Ride Height: 8 1/4"

Re: Why have the axles weighed (split from Re: Just Got Our First Foretravel)

Reply #3 – May 14, 2017, 11:53:59 am

Quote from: dke1955 – May 14, 2017, 11:39:30 am

This last week when at OTM for repairs I was told by the tech my tires looked "over inflated", I was asked how many pounds I was running and I answered 95 front 90 rear...his reply was "that's to much, you should be running 85 lbs HOT.

This is absolutely wrong. Unfortunately, this has been discussed in the past and I believe it's the same tech giving this absolutely wrong information. This is VERY unfortunate.

1) You cannot state what the inflation should be without knowing the actual weights and looking at the load/inflation table for your specific tires.

2) You do NOT use hot pressures. You use COLD pressures.

Quote

I was also told not to worry about weighing individual wheels as I have solid front/rear axles.

Wrong again. You can be several hundred pounds different side to side (on some SOBs even over 1000 lbs different). If you inflate assuming both ends are the same, and you're off, one tire is going to be underinflated and you risk damaging the tire or having a blowout.

Quote

Now came/comes the question of "HOT". In all my 62 years of life never heard anyone state to fill the tires hot. But, and especially since installing a TPM system I have begun to question the hot pressure myself. On my last trip, the tire pressures jumped up about 8 to 10 lbs per tire as I drove along...so I was running 113 to 114 lbs., and yes at those pressures you do feel every pebble on the road, and the ride becomes stiffer. So I gotta say, to this noob the hot statement made a tiny bit of sense as if I were to set the, for example, front tire at 95 when hot then I am at the correct pressure for the load. BUT I understand the problems when the tire is cool, not being at the correct pressure until the tire gets up to temp., running in cold conditions etc., however the "hot" statement from the tech was/is not the first time I have ever wondered about if it.

All tire manufacturer load/inflation tables are for COLD pressures. The maximum inflation pressures stamped on rims are COLD pressures. The maximum inflation pressures on tires are COLD pressures. The manufacturers understand that tires are going to heat up when you roll, but that's going to be variable. You always inflate for your weights, your tires, cold.

Look for any post by Brett Wolfe (wolfe10) for more information on proper tire inflation. As he wisely advises in this thread, if you don't know your weights, until you do it's safest to inflate to the pressures on your plate for your axle ratings.

(ETA - I don't mean to sound harsh, but this is a safety issue and extremely important. If this tech is adjusting your tire pressures, it behooves you to recheck them yourselves ASAP and put them where they need to be per your tire inflation table)

Re: Why have the axles weighed (split from Re: Just Got Our First Foretravel)

Reply #4 – May 14, 2017, 11:56:33 am

First thing is, tires don't appear overinflated. Different brands and models have different construction. Some have a really flexible sidewall and others are stiffer. They may look quite different at the same pressure.

Tire pressure is cold not hot. What was this guy thinking?

Your pressures sounded fine the way they were. I use 110 psi all around and have been happy with that both professionally and in my private RVs since the '60s. Others may find the ride too firm with some tire brands.

I think everyone has to do their own research then use what they are happy with - otherwise they end up chasing their tails.

Pierce

Re: Why have the axles weighed (split from Re: Just Got Our First Foretravel)

Reply #5 – May 14, 2017, 12:04:44 pm

Michelle is correct and the tech has been giving the wrong information for a while now.

Re: Why have the axles weighed (split from Re: Just Got Our First Foretravel)

Reply #6 – May 14, 2017, 12:22:48 pm

Tire inflation pressure is a subject rife with misinformation, anecdotal "proof" of incorrect theories, and absolute wisdom imparted by every Bubba who ever worked at a filling station (even if his most challenging responsibility was washing bugs off windows).

Add to this the fact that very few tire pressure gauges are ever precisely calibrated, even when new. When they are 10 or 20 years old and have banging around in a tool box all that time, you will probably get just as accurate pressure readings by consulting your morning tea leaves.

What I do (you can do whatever you want to do...it's your life (and that of your passengers) riding on your tires:

1. Read and heed the tire manufacturer's recommendations.
2. Read and heed the advice of people you trust, assuming they don't give advice contrary to Rule No. 1 (above).
3. Buy the best tire pressure gauge you can afford, and treat it with respect (like the precision tool it should be).
4. USE THE GAUGE REGULARLY!
5. WHEN THE TIRES ARE COLD!

Re: Why have the axles weighed (split from Re: Just Got Our First Foretravel)

Reply #7 – May 14, 2017, 12:34:55 pm

Michelle & Pierce,
I understand your replies, and no you are not harsh. I agree with you both and Mr. Wolfe completely, I was just honestly a little taken back by the comments of the tech., and as I say, while it made me wonder for a second or two I will not and have not changed my procedures for checking tire pressures and weighing the coach. I AM intelligent enough to question rather than blindly follow, in addition the comments of Mr. Wolfe, you Michelle, and the others in the know on this forum ARE the places I go to when I want/need good, trustworthy, time tested advice and information. Did not intend to stir the pot or interject a post conflicting with yours...like I said at the end of my post, I will continue to test and weigh, and fill my tires as I feel is appropriate based on the manu. recommendations (cold fill). Probably should have not posted to begin with...but thought I would get feedback on what I was being told...well I got the feedback!

Thanks,
dave

Re: Why have the axles weighed (split from Re: Just Got Our First Foretravel)

Reply #8 – May 14, 2017, 12:52:42 pm

Dave - you were right in posting since this is something that has come up before. I'm sure there are some who would follow the tech's advice without realizing the implications, or would stop and question what they had previously read.

So don't apologize - you provided the forum a very important topic for clarification and it was definitely not stirring the pot

(ETA those of us who jumped in quickly did so because we care about member safety, and wanted to make sure the correct information was getting out. My apologies to you if I came across as jumping on your post - I was more running after you as you drove out of the parking lot, waving my arms to get you to stop before you got too far down the road with bad info)

Re: Why have the axles weighed (split from Re: Just Got Our First Foretravel)

Reply #9 – May 14, 2017, 01:51:49 pm

Quote from: Michelle – May 14, 2017, 12:52:42 pm

Dave - you were right in posting since this is something that has come up before. I'm sure there are some who would follow the tech's advice without realizing the implications, or would stop and question what they had previously read.

So don't apologize - you provided the forum a very important topic for clarification and it was definitely not stirring the pot

(ETA those of us who jumped in quickly did so because we care about member safety, and wanted to make sure the correct information was getting out. My apologies to you if I came across as jumping on your post - I was more running after you as you drove out of the parking lot, waving my arms to get you to stop before you got too far down the road with bad info)

Michelle absolutely no apology necessary or warranted. You and the others on this forum we all turn to for advice and information do a fantastic job, and I mean that will all sincerity. It IS very comforting to know there are those on this forum who WILL take the time to run after any of the members screaming " you're about to make a serious mistake"! It is also a comfort to me personally to understand I was correct in listening to that little voice in my head that said, "HOT...seriously?...Nope not doing that...sounds interesting but NOPE not doing that", and of course I got the information for making and staying with that decision based on the information such as what you and Mr. Wolfe posted herein, and previously.
Thanks for what you do!
Have a good day!
dave

Re: Why have the axles weighed (split from Re: Just Got Our First Foretravel)

Reply #10 – May 14, 2017, 01:52:51 pm

Here's an example:

Re: Why have the axles weighed (split from Re: Just Got Our First Foretravel)

Reply #11 – May 14, 2017, 05:31:40 pm

Very good Mike, I had my three coaches weighed and adjusted the pressure accordingly. I will second what Michelle said about jumping pretty hard on the question. I have seen the damage a tire can do to a coach. Gary Omel had the front passenger tire blow and it messed up the side and blew a hole thru the floor. Another friend pulled into FOT with his drivers side Eyebrow missing. Inner dual blew and he had pressure pro on too.

Re: Why have the axles weighed (split from Re: Just Got Our First Foretravel)

Reply #12 – May 14, 2017, 05:59:08 pm

Looking back on two previous SOBs, NOBODY ever suggested I have the coach weighed. It was always the stock, "110 in the fronts, 90 in the rears". My coaches always ran hard, and I'd figured that's the way things work. I badmouthed Toyo for tires that wore out early, and my Goodyear dealer gave me the same bad advice. This one runs smooth with the correct pressure for this type of tire, which the PO gave the weigh paper to the dealer from Brett when switching over to the wider Michelins.

Re: Why have the axles weighed (split from Re: Just Got Our First Foretravel)

Reply #13 – May 14, 2017, 08:04:46 pm

Quote from: dke1955 – May 14, 2017, 11:39:30 am

This last week when at OTM for repairs I was told by the tech my tires looked "over inflated", I was asked how many pounds I was running and I answered 95 front 90 rear...his reply was "that's to much, you should be running 85 lbs HOT. I was also told not to worry about weighing individual wheels as I have solid front/rear axles. Also, I was told the tires are radials and are designed to run a little "bulge" on the sides of the tire allowing the tread maximum contact with the road just as the radials on our cars. I don't want to get into the name of the tech and who said what but this tech has over 20+ years FT experience so after speaking with him I was again wondering if the tire pressures I had decided on were correct or not.
So, when I left OTM I drove to the CAT scales on the north side of town, just to see what I weighed. It was just me in the coach, all tanks were empty (well maybe 1/4 tank fresh H2O) half a tank of diesel, full propane. I understand this is not typical travel weight but I was after just some baseline info., will adjust and reweigh at another time. The scales showed 11340 lbs steer 19060 lbs drive. According to the chart given to me by tech., that is 95 lbs per tire front and 85 lbs per tire rear.
Now came/comes the question of "HOT". In all my 62 years of life never heard anyone state to fill the tires hot. But, and especially since installing a TPM system I have begun to question the hot pressure myself. On my last trip, the tire pressures jumped up about 8 to 10 lbs per tire as I drove along...so I was running 113 to 114 lbs., and yes at those pressures you do feel every pebble on the road, and the ride becomes stiffer. So I gotta say, to this noob the hot statement made a tiny bit of sense as if I were to set the, for example, front tire at 95 when hot then I am at the correct pressure for the load. BUT I understand the problems when the tire is cool, not being at the correct pressure until the tire gets up to temp., running in cold conditions etc., however the "hot" statement from the tech was/is not the first time I have ever wondered about if it. For me until I feel better about "hot" I will continue to test and fill cold.
Happy Mothers Day!
see ya
dave

Also if anyone is interested here are the alignment figures I was given:
Caster: Left 4' to 4 1/2' Right 4 1/2' to 5'
Camber: (not adj)
Toe: 1/16" to 1/8"
Ride Height: 8 1/4"

There is a LOT of bad information in this post about proper tire inflation. Without taking the time to pick each and every portion of the post apart, let us first say that our position at OTM on proper tire inflation is in complete agreement with the info posted by Michelle & Brett. That has always been our position and we will get to the bottom of the misunderstanding tomorrow morning. We have made our fair share of mistakes, and I would not put it past one of our techs or any of us at OTM to say or do the wrong thing from time to time.

However, for anyone to suggest that tire pressure should be measured "HOT" is absurd. There clearly was a misunderstanding and not even the least experienced tech at OTM would intentionally suggest running 85 PSI cold - much less "HOT" in front or drive axle tires on a U295 or any Unicoach period.

We will clear this up tomorrow. Thankful for the customers who took the time to contact us directly to make sure correct information is posted. We apologize for the confusion, and proper tire pressure is not something we take lightly.

Sincerely,
Old Town Motorcoach

Re: Why have the axles weighed (split from Re: Just Got Our First Foretravel)

Reply #14 – May 14, 2017, 09:54:37 pm

I had a much different experience with OTM. I have not had my coach weighed but OTM did recommend I consider doing so. However, when I left OTM in April I got tire pressures adjusted by and advice from OTM more consistent with the information given by Michelle and Brett. We had planned to weigh our motorhome in Livingston but that didn't work out so hopefully it will happen in June. Advice to me from OTM was to weigh coach by each axle and, if possible, each wheel corner in travel loaded mode, check pressures regularly when cold, adjust using tire mfg's recommended pressures, don't exceed tire and wheel recommended pressures, and try to redistribute load as required. After checking my pressures which had been adjusted, before departure to Nacogdoches, by Mike's Truck and Trailer Repair in Birmingham/Tuscaloosa area, OTM checked all pressures cold and reduced my tag pressure, I believe, to 75psi. Given the recent OTM post, I suspect we will see this issue addressed and clarified quickly.

Re: Why have the axles weighed (split from Re: Just Got Our First Foretravel)

Reply #15 – May 15, 2017, 12:17:42 am

Tire Pressure gauges are notorious not very accurate. A gauge that is within 5% depending on the gauges total range is pretty good. Cannot vouch for the truck scales accuracy, but I would guess it's in the 5% range. I have a grain elevator about 10 miles away, that scales are open 24/7 and the weight is displayed in the window. Little bit of a sine/cosine error but you can probably get within 5-7% of tire weight. Maybe todays best practices would include a walk around of the coach every 2-3 hours while traveling, with an IR temperature gun and shooting vital components.

Re: Why have the axles weighed (split from Re: Just Got Our First Foretravel)

Reply #16 – May 15, 2017, 06:39:31 am

If you had Issac working on your coach, he is top notch and would steer you properly.

Re: Why have the axles weighed (split from Re: Just Got Our First Foretravel)

Reply #17 – May 15, 2017, 07:30:12 am

Must be --two--OTM's in NAC . The one across the street from MOT does not have a tech that puts out dumb stuff like that . Got to be another one some where .

Brad Metzger

Re: Why have the axles weighed (split from Re: Just Got Our First Foretravel)

Reply #18 – May 15, 2017, 09:38:46 am

Glad to see OTM chiming in.

Without going into details, based on posts over the past years, there's a tech in Nac who has recommended "non-standard" tire inflation practices for a while (I can find posts going back 3 years with exactly this incorrect recommendation), likely due to getting bad information himself. It's not ill-intended, he just doesn't have the correct information. It's been discussed on the forum in the past, when he worked for a different company. "As Nacogdoches Turns", he happens to work for OTM now.

Rather than painting this in a negative light, I see it as fortunate we had this discussion so we can get everyone on the same, manufacturer/industry-recommended page when it comes to load and tire inflation. Now, it might not ever become standard industry practice, but one of the storage/service facilities in the DFW area, NIRVC in Lewisville, added the equipment to do individual wheel weights a year or so ago. It's nice to see more in the RV biz understanding how important weights and tire inflation are.

Re: Why have the axles weighed (split from Re: Just Got Our First Foretravel)

Reply #19 – May 15, 2017, 09:56:40 am

Quote from: Michelle – May 15, 2017, 09:38:46 am

...one of the storage/service facilities in the DFW area, NIRVC in Lewisville, added the equipment to do individual wheel weights...

I called the NIRVC in the Atlanta area. They offer the service as well for $85. If you're interested call Tino at (770) 979-4051. He needs a few hours notice to get the scales setup so he's ready when you roll in. Usual disclaimer, I have no financial interest in NIRVC etc.

I wonder if it's worthwhile getting our weighed since it's not yet loaded with anything except tools, fuel and water? The tires are currently inflated to the placard weight and we are indeed feeling every little pebble on the road. It is, shall we say, a firm ride.

Re: Why have the axles weighed (split from Re: Just Got Our First Foretravel)

Reply #20 – May 15, 2017, 10:43:12 am

I thought I had posted a video I found a few weeks ago re: tire pressures in trucks. I cannot find it now.

It explained how low pressure is bad in a multitude of ways, while high pressure is not unless you exceed rated pressures.

It explains how inflating cold is done so they will reach the correct operating pressure after running.

Adding my own thoughts, the only "bad" about running higher than a little safety margin is a harsher ride. Using a TPMS like me PressurePro allows me to know and then monitor normal vs abnormal operational pressures.

Also, that 120psi molded in my sidewalks is not the max cold pressure, just that more pressure than that won't gain more load capacity. The 120 max stamped on my rims is the max cold, not hot.

Re: Why have the axles weighed (split from Re: Just Got Our First Foretravel)

Reply #21 – May 15, 2017, 11:11:33 am

Quote from: Tom Lang – May 15, 2017, 10:43:12 am

I thought I had posted a video I found a few weeks ago re: tire pressures in trucks. I cannot find it now.

It explained how low pressure is bad in a multitude of ways, while high pressure is not unless you exceed rated pressures.

It explains how inflating cold is done so they will reach the correct operating pressure after running.

Tom,

I don't see a post by you with a tire video, but there is one by Kenhat in Fire Ring Tire inflation theory

Re: Why have the axles weighed (split from Re: Just Got Our First Foretravel)

Reply #22 – May 15, 2017, 11:27:35 am

Yes, that's the same video. Thanks for posting the link here. Lots of good information there.

Re: Why have the axles weighed (split from Re: Just Got Our First Foretravel)

Reply #23 – May 15, 2017, 12:19:09 pm

Correct rear tire pressure on the rear axle on our weighed u320 at full load per the Michelin chart for our xza-3+'s is 87 psi.

I bought the expensive 1% accuracy power tank co2 commercial digital gauge and filler someone posted here to get a more accurate pressure.

Have not done left to right yet to fine tune this even more but as posted here and in my old experience two psi is noticeable for most tires.

The comment was that they would not let out a unicoach 295 with 85 pounds might be correct with load range "g" tires but not "h's." At least on our coach.

A totally empty u295 with g's might only need 85 in the rear.

Re: Why have the axles weighed (split from Re: Just Got Our First Foretravel)

Reply #24 – May 15, 2017, 02:27:41 pm

I sent my pressure gage back to the manufacture for recalibration. I asked if he had any latitude when adjusting the gage, yes. I said I was intrested in 100 PSI.
When I got my gage back it included a picture of my gage on the test bench next to the master gage. Both sitting on 100 PSI
Cost was $7.00 postage each way.

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