First time on the CAT Scale

[Curtisgeiger]

Originally Posted by Saltydog44

As I understand it, the tag can be adjusted to change the weight distribution if it is sufficiently off to be a problem. I'd call Spartan CS. BTW Their school is one ot the best investments we've made - I think everyone who has gone would agree with that. One week for you and your wife and lots of hands on info. Then you can go on up into MI for great sightseeing. You can also hit Entegra along the way. BTW our weights were: F - 16220 M - 15620 T - 10010 Spartan said that was OK. I've moved some stuff around so I need to do a new 4 corner weight.

I called Spartan this morning who referred me to Goodyear.

Goodyear recommended I go with lowest PSI rating of 90 in the weight is below what the chart lays out.

So that means my steer axles are 115 and everything else will be 90.

Curt

[D Lindy]

F.Y.I. if you can adj the air pressure on the TAG axle you can use that to shift weight forward to the front axle by increasing air pressure, or remove weight from the front axle by removing air pressure from the TAG. Bear in mind though that any weigh removed from the front axle will end up on the rear axle.

[brobox]

Originally Posted by Curtisgeiger

I called Spartan this morning who referred me to Goodyear.

Goodyear recommended I go with lowest PSI rating of 90 in the weight is below what the chart lays out.

So that means my steer axles are 115 and everything else will be 90.

Curt

Curt,
On the rears since you do not have a 4 corner weight to work with, I would look at going + 5 PSI to allow for one side "maybe" heavier than the other. Just the way I air my tires and may not be correct for everyone.

[Saltydog44]

Originally Posted by brobox

Curt,
On the rears since you do not have a 4 corner weight to work with, I would look at going + 5 PSI to allow for one side "maybe" heavier than the other. Just the way I air my tires and may not be correct for everyone.

I agree except at 90 he is already over the PSI for his weight since it's below the lowest level of the chart?

[Sky_Boss]

Do you have all 6 corner weights? That is what you need to start with.

As to lowest PSI...that tire manufacturer specifies that. Michelin 305/70R minimum is 75 psi. I don't know what your tire size is.

To get all 6 corner weights on a CAT scale requires 2 weighings and a calculator. I built a spreadsheet to do this easily. Also...I have a 3' long wooden dowel rod I keep in my coach to reach the speaker button. I also go see the weigh master to tell them the second weight will be on pad 2 & 3 so they don't get all weirded out. I once had a trucker get all weirded out on my second weighing but after I explained it, he was pretty impressed.

1. Get full axle weights as you have. Make sure you have a spotter so you can split the tag and drive axles between pads 2 & 3.

2. Go inside and get ticket. You will need that ticket number for a reweigh.

3. Go back to scale and straddle the edges. I put the center of the windshield over the left or right side crack between the scale pad and the apron around it. I prefer to have my driver side wheels off the scale.

4. Put steer wheels on pad 2 and both the drive and tag wheels on pad 3. (Because of the protective arch over pad 1 you can not get the steerers on pad 1.) Get out of the coach and with your trusty rod push the speaker button and tell them it is a reweigh then give them the ticket number. If you put the diver side wheels on the pad that is PERFECT since you will be out of the seat and not have to add that back in to the pad 2 numbers if you put the other wheels on the apron.

5. Back up a tad as needed and exit the scales to get your second ticket. In my area the first weigh is $10 and the reweigh is $2.

Now the hard part...

your second ticket will have drive and trailer weights instead of steer, drive and trailer. So...

1. Subtract the second drive weight (wheel on scale) from the first steer weight to determine the weight of the wheel not on the scale. Use the highest weight between the second weigh and the product of your math to determine tire pressure.

NOW...the REAL tricky math work...

2. Divide the second trailer weight by the COMBINED drive and trailer weights of the first weighing. That will give you a % of one side compared to the other.

3. NOW...multiply individually, both the drive and trailer weights on the first ticket by the % of step 2...that will be the approximate (should be real close) the individual weight of the drive and trailer wheels that were on the scale for the second weighing.

4. Finally, subtract the numbers you calculated in step 3 from the full drive and trailer weights of the first weighing and you now have the approximate weight for the wheels that were off the scale. Use the highest Drive and trailer weight for your tire pressure chart.

My spreadsheet adds 2% to the highest calculated, individual wheel weight for each axle to cover all my bases. This is the weight I use on my tire pressure charts to determine proper PSI.

Are your eyes rolling to the back of your head yet? LOL Listen...it ain't that hard if I can do it.

BTW...your front tire minimum PSI is 80 and rears are 90 per GY charts. I'm not sure where 85 PSI ever came into play.

FINALLY...I run my drive wheels 10 PSI higher than my tag. WHY? By doing that I put a bit more weight on the drive. In effect I want my drive tire to stay "rounder" than my tag. From my testing this appears (as I was hopeful it would be) to make the drive wheel act more like a fulcrum. What that gains me is that it allows the weight of the coach behind the drive axle to lift a few extra lbs off of my front axle. It isn't an exact number/science but since I am nearly maxed out on my front axle, it helps. YMMV and if you are not pushing the limits of your front axle, it would be totally unneeded.

I am happy to share my spreadsheet to anyone if they PM me.

Are you still awake? I hear the class bell ringing.

[brobox]

Originally Posted by Saltydog44

I agree except at 90 he is already over the PSI for his weight since it's below the lowest level of the chart?

Not sure either. That is why I like to weigh after everything include people are loaded for the road. Not knowing more about Curt's weigh ticket, he travels with 6 people, was everybody and their clothes on board? Or was it just a weigh ticket to see what he can start loading on which axle? Once loaded tire presure can vary 5 or 10 lbs. I suggested the + 5 lbs just to be on the cautious for loading, then weigh again and adjust rear tire pressure. The front axle is almost maxed out, so that shouldn't change.

[DSL417]

Don, I knew you were an engineer...true to heart in every sense. How the heck did you get into ATC???

By the way, the Aspires now have Goodyears.

[Sky_Boss]

Originally Posted by DSL417

Don, I knew you were an engineer...true to heart in every sense. How the heck did you get into ATC???

By the way, the Aspires now have Goodyears.

Thanks Dave! 30 days left but who is counting...ME!

I forgot to edit the line out about Michelin...I looked up the tires on the Entgra site and quoted GY numbers.

[Steve Ownby]

Originally Posted by DSL417

Don, I knew you were an engineer...true to heart in every sense. How the heck did you get into ATC??? By the way, the Aspires now have Goodyears.

Since you guys are new to Goodyear tires I'll give you a heads up.

The Goodyear G670 tire has shown itself to be prone to "River wear" on the steer axle. This is wear of the second rib in from the outside. Goodyear does not consider this to be a warrantee issue and will not do anything.

The only thing that seems to help is to run the steer tires at 10 psi or so above the inflation table. Since RV tires age out before they wear out it may not be a problem.

Just FYI.

[Sky_Boss]

Originally Posted by Steve Ownby

...
The Goodyear G670 tire has shown itself to be prone to "River wear" on the steer axle. This is wear of the second rib in from the outside. Goodyear does not consider this to be a warrantee issue and will not do anything.

The only thing that seems to help is to run the steer tires at 10 psi or so above the inflation table. ....

And the plot thickens! Thanks for that tidbit.

[gruelens]

If you are traveling in Oregon, look for a highway scale station that is closed. Most in Oregon leave their outside digital displays on even when "closed". You can than weigh and play with wheel positions for free.

[Curtisgeiger]

Originally Posted by Sky_Boss

Do you have all 6 corner weights? That is what you need to start with. As to lowest PSI...that tire manufacturer specifies that. Michelin 305/70R minimum is 75 psi. I don't know what your tire size is. To get all 6 corner weights on a CAT scale requires 2 weighings and a calculator. I built a spreadsheet to do this easily. Also...I have a 3' long wooden dowel rod I keep in my coach to reach the speaker button. I also go see the weigh master to tell them the second weight will be on pad 2 & 3 so they don't get all weirded out. I once had a trucker get all weirded out on my second weighing but after I explained it, he was pretty impressed. 1. Get full axle weights as you have. Make sure you have a spotter so you can split the tag and drive axles between pads 2 & 3. 2. Go inside and get ticket. You will need that ticket number for a reweigh. 3. Go back to scale and straddle the edges. I put the center of the windshield over the left or right side crack between the scale pad and the apron around it. I prefer to have my driver side wheels off the scale. 4. Put steer wheels on pad 2 and both the drive and tag wheels on pad 3. (Because of the protective arch over pad 1 you can not get the steerers on pad 1.) Get out of the coach and with your trusty rod push the speaker button and tell them it is a reweigh then give them the ticket number. If you put the diver side wheels on the pad that is PERFECT since you will be out of the seat and not have to add that back in to the pad 2 numbers if you put the other wheels on the apron. 5. Back up a tad as needed and exit the scales to get your second ticket. In my area the first weigh is $10 and the reweigh is $2. Now the hard part... your second ticket will have drive and trailer weights instead of steer, drive and trailer. So... 1. Subtract the second drive weight (wheel on scale) from the first steer weight to determine the weight of the wheel not on the scale. Use the highest weight between the second weigh and the product of your math to determine tire pressure. NOW...the REAL tricky math work... 2. Divide the second trailer weight by the COMBINED drive and trailer weights of the first weighing. That will give you a % of one side compared to the other. 3. NOW...multiply individually, both the drive and trailer weights on the first ticket by the % of step 2...that will be the approximate (should be real close) the individual weight of the drive and trailer wheels that were on the scale for the second weighing. 4. Finally, subtract the numbers you calculated in step 3 from the full drive and trailer weights of the first weighing and you now have the approximate weight for the wheels that were off the scale. Use the highest Drive and trailer weight for your tire pressure chart. My spreadsheet adds 2% to the highest calculated, individual wheel weight for each axle to cover all my bases. This is the weight I use on my tire pressure charts to determine proper PSI. Are your eyes rolling to the back of your head yet? LOL Listen...it ain't that hard if I can do it. BTW...your front tire minimum PSI is 80 and rears are 90 per GY charts. I'm not sure where 85 PSI ever came into play. FINALLY...I run my drive wheels 10 PSI higher than my tag. WHY? By doing that I put a bit more weight on the drive. In effect I want my drive tire to stay "rounder" than my tag. From my testing this appears (as I was hopeful it would be) to make the drive wheel act more like a fulcrum. What that gains me is that it allows the weight of the coach behind the drive axle to lift a few extra lbs off of my front axle. It isn't an exact number/science but since I am nearly maxed out on my front axle, it helps. YMMV and if you are not pushing the limits of your front axle, it would be totally unneeded. I am happy to share my spreadsheet to anyone if they PM me. Are you still awake? I hear the class bell ringing.

Thanks for the detailed information

Please send (PM) me the worksheet

I am learning something everyday -- I just love it.

Curt

[Curtisgeiger]

Originally Posted by brobox

Curt, I just checked the Aspire brochure and your weight looks fine. Your front does not have much more room for any more loading once all of the passengers are on board.

Front rated 14,600 your weight 14,280
Rear rated 20,000 your weight 16,060
Tag rated 12,000 your weight 7180.

Gross rated 46,600 your gross 37520

Lots of room left in the rear of the coach for load.

Just as a precaution, I would weigh again once you are fully loaded and all passengers sitting where they normally ride to do a final adjustment on tire pressure.

I weigh at the State truck scale on I-75 near my home and those guys think it's great when an RV'er is that safe and comes in to check their load against tire pressure. With the new computer systems (no more printouts) I do have to go into the parking lot first, walk in and tell them I would like to weigh with a print out. They have always been super.

I had my coach weighed again loaded with the trailer hooked up.

Steer = 14,500
Drive = 17,860
Tag. = 15,040

Do I need to roll my SUV back a few more inches to take some weight off the tongue of the trailer?

Curt

[hogdriver]

Curt

Be careful putting your SUV too far aft on the trailer. You need at least 60% of the vehicle weight on the tongue. If the tongue is too light you'll get a lot of swaying back and forth to the point you could lose control. Better a heavy tongue than a light one! The engine of that suburban will help make that happen but I would call the trailer manufacturer and get their recommendation.