Tires - Michelin 2004 U320 - Steer vs. Drive tires - 275/80R22.5 vs. 295/80R22.5

Topic: Tires - Michelin 2004 U320 - Steer vs. Drive tires - 275/80R22.5 vs. 295/80R22.5 (Read 4215 times) previous topic - next topic

Re: Tires - Michelin 2004 U320 - Steer vs. Drive tires - 275/80R22.5 vs. 295/80R22.5

Reply #50 – March 17, 2021, 10:55:29 pm

Real world conditions are different than just turning the wheel and seeing if it touches or how close it comes. Ours is very close to touching in a static demonstration but when turning and loading the coach, especially on uneven ground, it does touch. Going forward, it just polishes the bottom plate. It could possible do more than that if the coach were in reverse. I'm thinking about backing into a campsite on gravel or dirt.

Pierce

Re: Tires - Michelin 2004 U320 - Steer vs. Drive tires - 275/80R22.5 vs. 295/80R22.5

Reply #51 – March 18, 2021, 06:30:19 am

Pierce brings up a good point....... so if the larger tires aren't really needed.....?..... I would seriously consider staying with the correct size and heaviest load rating available.

Re: Tires - Michelin 2004 U320 - Steer vs. Drive tires - 275/80R22.5 vs. 295/80R22.5

Reply #52 – March 18, 2021, 10:26:45 am

I understand wanting to have tires with an increased load rating and going to 16 ply will do the trick but in the existing size with a firmer ride. I have put larger sized tires on quite a few cars but even though the change only increases the tire radius just under 1/2 inch, it needs to be established that no damage can be done at any coach angle and loading while backing. Possibly, the cut could be adjusted so it would clear but I wonder what that would do to the coach turning radius?

So, staying with 80 aspect ratio at 295 size keeps 14 ply and a taller sidewall for a more comfortable ride while increasing the load capacity at lower pressures. But, FOT cannot recommend going to that size for legal reasons.

We are quite satisfied in the ride with ours at 110 psi all around but I see others may not be.

In case of a flat tire, the 295/75R22.5 is much easier to find while on the road if you don't carry a spare.

With our tires already polishing our airbag plates, I'm inclined to keep on the cautious side and let someone else give it a try. Remember, the coach was designed with the narrower 275/80R22.5 as the default tire. The 295/75 was a change that has proven successful with only a minor clearance issue.

Pierce

Re: Tires - Michelin 2004 U320 - Steer vs. Drive tires - 275/80R22.5 vs. 295/80R22.5

Reply #53 – April 14, 2021, 08:35:54 pm

Done. I'm the happy owner of a 2004 Foretravel U320. A beautiful coach. My thanks to the previous owner for taking such great care of the bus. It is in great shape.

Now the fun begins. I'm inspecting for things that need fixing and/or any desired upgrades.

First of all, it turns out this coach is riding on Bridgestone R268 295/80R22.5 tires. The tires under discussion in this thread. But, even though the coach is riding with the bigger tires that I wanted, I'm not convinced yet that the 295/80 are appropriate for this coach.

There are no signs of dry rot or sidewall problems with the tires, but they're 6 years old, so I plan to change them right away. I'll replace with the same size if I'm satisfied that the 295/80s are appropriate. Eight tires and 6 Centramatic wheel balancers. That's the first big expense for the coach.

On a related note, I have noticed that the underneath of the wheel well for both tag tires show obvious signs that the tag tires have been hitting the wheel well. But, I don't think the 1/3" height difference between the axle and the top of the tire when comparing the 275/80 with the 295/80 would be to blame. It seems the shocks may need some looking into. Also, on my 10 hour drive after purchasing the coach, I noticed a lot of bouncing of the coach, more than would be reasonable. But, not sure how much bouncing is normal for the MH. The other wheel wells do not show any similar signs of tire hitting.

Any thoughts from others on this issue with the tag axle?

Re: Tires - Michelin 2004 U320 - Steer vs. Drive tires - 275/80R22.5 vs. 295/80R22.5

Reply #54 – April 15, 2021, 10:15:17 am

Quote from: cucotx – April 14, 2021, 08:35:54 pm

Done. I'm the happy owner of a 2004 Foretravel U320. A beautiful coach. My thanks to the previous owner for taking such great care of the bus. It is in great shape.

Now the fun begins. I'm inspecting for things that need fixing and/or any desired upgrades.

First of all, it turns out this coach is riding on Bridgestone R268 295/80R22.5 tires. The tires under discussion in this thread. But, even though the coach is riding with the bigger tires that I wanted, I'm not convinced yet that the 295/80 are appropriate for this coach.

There are no signs of dry rot or sidewall problems with the tires, but they're 6 years old, so I plan to change them right away. I'll replace with the same size if I'm satisfied that the 295/80s are appropriate. Eight tires and 6 Centramatic wheel balancers. That's the first big expense for the coach.

On a related note, I have noticed that the underneath of the wheel well for both tag tires show obvious signs that the tag tires have been hitting the wheel well. But, I don't think the 1/3" height difference between the axle and the top of the tire when comparing the 275/80 with the 295/80 would be to blame. It seems the shocks may need some looking into. Also, on my 10 hour drive after purchasing the coach, I noticed a lot of bouncing of the coach, more than would be reasonable. But, not sure how much bouncing is normal for the MH. The other wheel wells do not show any similar signs of tire hitting.

Any thoughts from others on this issue with the tag axle?

Congratulations on new coach. Over the road trucking is allowed to operate tire up to ten years old. Your old tires may have a resale value. Does your tag axle lift on your coach? May have caused spinning down retracted?
Scott

Re: Tires - Michelin 2004 U320 - Steer vs. Drive tires - 275/80R22.5 vs. 295/80R22.5

Reply #55 – April 15, 2021, 10:55:14 am

Here is a Michelin Ref for RV tires.

Loaded rolling radius for a 275/80R 22.5 LRH XLine Energy Z is 18.7"
Loaded rolling radius for a 295/80R 22.5 LRH XZA2 is 19.1"

The distance rolled by the 295 per revolution is about 2.1% greater than for the 275. If your coach was setup for the 275 size then speed and miles shown will be less than actual. In 10,000 miles it will be off by 210 miles.

It is common for VMSpc users to ask about the difference between ECU reported miles and the dash gauge, they are always different. Loads, tire pressure altitude, temperature all play into the difference but they are rarely more than 1%. Changing to a different tire size will make a bigger difference

Re: Tires - Michelin 2004 U320 - Steer vs. Drive tires - 275/80R22.5 vs. 295/80R22.5

Reply #56 – April 15, 2021, 11:14:53 am

Quote from: dsd – April 15, 2021, 10:15:17 am

Over the road trucking is allowed to operate tire up to ten years old.
Scott

Not sure there is a law on the books regarding older than 10 year old tires in commercial use.

How Long Can Your Commercial Truck Tires Last? - Green Towing Los Angeles

Re: Tires - Michelin 2004 U320 - Steer vs. Drive tires - 275/80R22.5 vs. 295/80R22.5

Reply #57 – April 24, 2021, 11:59:25 pm

Quote from: Roger & Susan in Home2 – April 15, 2021, 10:55:14 am

Here is a Michelin Ref for RV tires.
Loaded rolling radius for a 275/80R 22.5 LRH XLine Energy Z is 18.7"
Loaded rolling radius for a 295/80R 22.5 LRH XZA2 is 19.1"

So my recent purchase of a 2004 4020 U320 has 6 year-old Bridgestone R268 295/80R22.5 tires. The R268 have a loaded radius of 19.4". The tire that I would like to start using is the Michelin X Coach H LZ LRH 295/80R22.5. That tire has a loaded radius of 19.3". As a side note, the X Coach tires mounted single have a load rating of 8270 lbs at 123 psi. R268 is 7830 lbs at 123 psi. The X Coach have a dual mounting load rating of 7160 @123 psi. The R268 has a dual load rating of 6940 at 123 psi. So the overall goal for using the X Coach with the U320 is to run them at under 100 psi and still meet the GAWR of the U320.

So the question remains, is it at all safe and practical to use the 295/80R22.5 tire size as a replacement for the stock 275/80R22.5 with a 2004 4020 U320?

1 - The first thing that I did with investigating this was to check for any signs of rubbing in the wheel wells and with the air bag mounting at all tire positions. My inspection of the U320 did not show any rubbing with the wheel well or air bags for the steering and drive axle positions. It does come close, so it may be "polishing" the air bag support bracket. It may just be that it is not leaving any obvious visible signs.

Both tag axle positions do show rubbing of the wheel well, but that may have other causes other than tire size, as per number 2 below.

2 - I have noticed that when the coach is leveled while parked, the top of the tire in the tag axle wheel well which is positioned up hill from the opposite tag axle does come very close to touching the wheel well. It's half an inch of spacing or so. In trying to balance the coach while parked, obviously the downhill tag axle bag is inflated more to raise that side of the coach, increasing the distance from top of that tire to the underside of wheel well. The bag in the uphill wheel well is somewhat deflated in the attempt to balance the coach.

In my opinion, this may be the cause of the signs of rubbing of the tag axle tire within its wheel well. That is, would it be possible for one of the tag axle tires to rub against the underside of its wheel well while turning in uneven ground and while the tag axle is lifted?

3 - An obvious question that I thought about, and which continues to bother me is this: Are there sensors in place or would it be possible that the leveling system won't be able to realize that there is a bigger tire installed and thereby end up with the bottom of the wheel well resting on the top of the tire instead of balanced appropriately by the air bags? That is a scary thought!

Thanks in advance for any help with this.

Re: Tires - Michelin 2004 U320 - Steer vs. Drive tires - 275/80R22.5 vs. 295/80R22.5

Reply #58 – April 25, 2021, 12:50:00 am

The air bags will keep the same distance no mater what tire is on, so a larger diameter tire will get closer to the floor. Not sure how much depends on the 1/2 distance of the larger diameter difference of the tire.

Re: Tires - Michelin 2004 U320 - Steer vs. Drive tires - 275/80R22.5 vs. 295/80R22.5

Reply #59 – April 25, 2021, 07:43:28 am

Just to mention again, 295/75R22.5 is a very close match to the 275/80R22.5.

Might want to solicit comments from those who have gone that route.

Re: Tires - Michelin 2004 U320 - Steer vs. Drive tires - 275/80R22.5 vs. 295/80R22.5

Reply #60 – April 25, 2021, 08:29:24 am

Quote from: cucotx – April 24, 2021, 11:59:25 pm

3 - An obvious question that I thought about, and which continues to bother me is this: Are there sensors in place or would it be possible that the leveling system won't be able to realize that there is a bigger tire installed and thereby end up with the bottom of the wheel well resting on the top of the tire instead of balanced appropriately by the air bags? That is a scary thought!

You are giving the HWH leveling system credit for intelligence it doesn't possess. There are no sensors to tell it what tire size is fitted. Correct ride height is the same regardless of tire size.

If you put a tire that is taller or wider than OEM stock on a coach, it will be more likely to touch, hit, or rub on something that is unyielding. Might be a serious problem - might not.

Re: Tires - Michelin 2004 U320 - Steer vs. Drive tires - 275/80R22.5 vs. 295/80R22.5

Reply #61 – April 25, 2021, 09:02:32 am

I run 295 75 22.5 Toyo tires, very little polishing on the airbag seats, they do touch with the air dumped the 75s are very very close to the 275 80s why would you want to go all the way up to 295 80 that are quit a bit larger. With a tag coach a LR H tire should be plenty.

Re: Tires - Michelin 2004 U320 - Steer vs. Drive tires - 275/80R22.5 vs. 295/80R22.5

Reply #62 – April 25, 2021, 09:51:12 am

1 - I was checking the maintenance records for the coach. It turns out both shocks for the tag axle were replaced about 6 months ago. That could account for the signs of rubbing of the tire in the wheel well. You can definitely learn a lot about a used coach by checking the repair records for it.

2 - What I think I'm going to do is stick with the 275/80R22.5 tire size that was designed into the coach by the smart people at FT. It may be safe to change to 295/75, but there would be no gain in the load rating for those tires, so why do it. The bottom line is that I really don't know enough about the coach to make a wise decision. And I don't have enough time to test for acceptable safety prior to buying the bigger tire.

I have purchased a TPMS with 12 sensors (coach and toad) and plan to install 6 Centramatics wheel balancers for all coach axles. The new tires, once properly inflated, the TPMS and the Centramatics should be good enough to roll down the road safely. In the meantime, I have plenty of other things to immediately fix and enhance in the coach, e.g. new chassis and house batteries, new FET battery isolators, proper multi stage dc-to-dc chargers for both the chassis and the aging AGM house batteries.

Thank you all. Great feedback and help from the knowledgeable Foretravel community. Much appreciated.

Re: Tires - Michelin 2004 U320 - Steer vs. Drive tires - 275/80R22.5 vs. 295/80R22.5

Reply #63 – April 25, 2021, 09:56:06 am

Quote from: cucotx – April 25, 2021, 09:51:12 am

What I think I'm going to do is stick with the 275/80R22.5 tire size that was designed into the coach by the smart people at FT.

Bit of a oxymoron to me. Some were smart, some missed the boat entirely.

Pierce

Re: Tires - Michelin 2004 U320 - Steer vs. Drive tires - 275/80R22.5 vs. 295/80R22.5

Reply #64 – April 26, 2021, 11:51:17 am

Keep in mind that taller tires will accelerate and decelerate slower. The CG will raise and the coach will be slightly more susceptible to wind movement.
Fuel mileage will suffer a little also as the tires weigh more and the effective gear is taller .
The exception is the 4 speeds that can use a little more gear , like my 88 , Cat .

Re: Tires - Michelin 2004 U320 - Steer vs. Drive tires - 275/80R22.5 vs. 295/80R22.5

Reply #65 – April 26, 2021, 12:37:35 pm

Quote from: Protech Racing – April 26, 2021, 11:51:17 am

Fuel mileage will suffer a little also as the tires weigh more and the effective gear is taller .

A taller gear ratio should give better fuel mileage not worse. Piston travel is less per mile. It's like a slight overdrive. Our U300 could use a little taller ratio in 4th but a taller ratio would give slightly slower acceleration.

Pierce

Re: Tires - Michelin 2004 U320 - Steer vs. Drive tires - 275/80R22.5 vs. 295/80R22.5

Reply #66 – April 26, 2021, 12:52:46 pm

Quote from: wolfe10 – April 25, 2021, 07:43:28 am

Just to mention again, 295/75R22.5 is a very close match to the 275/80R22.5.

Might want to solicit comments from those who have gone that route.

Bumping Brett's comment about a potentially more appropriate size alternative to the 275/80R22.5

Re: Tires - Michelin 2004 U320 - Steer vs. Drive tires - 275/80R22.5 vs. 295/80R22.5

Reply #67 – April 26, 2021, 01:19:45 pm

Fuel mileage will suffer a little also as the tires weigh more and the effective gear is taller .
The exception is the 4 speeds that can use a little more gear , like my 88 , Cat .
The reality is that it may be a wash . The taller heavier tire needs more throttle angle for the same V vs the taller Inches per revolution.

In my case the OE speedo read 9% high , Now the GPS speedo read DFN. 2300RPM is 63 MPH.

Re: Tires - Michelin 2004 U320 - Steer vs. Drive tires - 275/80R22.5 vs. 295/80R22.5

Reply #68 – April 26, 2021, 02:24:49 pm

Quote from: Protech Racing – April 26, 2021, 01:19:45 pm

Fuel mileage will suffer a little also as the tires weigh more and the effective gear is taller .
The exception is the 4 speeds that can use a little more gear , like my 88 , Cat .
The reality is that it may be a wash . The taller heavier tire needs more throttle angle for the same V vs the taller Inches per revolution.
In my case the OE speedo read 9% high , Now the GPS speedo read DFN. 2300RPM is 63 MPH.

Weight does not have much to do with it except for a slight difference in rotating mass when starting or stopping and only a tiny, bit. Yes, you do have to open the throttle slightly more but the decrease in piston travel per mile more than makes up for it.

Here is a primer for gear ratios vs MPG. The Pinto/Mustang photo says it all: Advance Auto Parts - Down for Maintenance

Now, anytime you change the aspect ratio, you do put more surface on the road which can increase the rolling resistance and lower the mpg slightly. But if the aspect ratio stays the same, the taller tire will get better mileage. So, a 295/75R22.5 will use a little more fuel than a 275/80R22.5 because of more square inches of rubber on the road. But lower aspect tires have shorter sidewalls so flex less and have slightly less rolling resistance because of less flex.

In flying, my twin used 31 gallons per hour so once I got to cruising altitude, I would increase the bite on the props with lower RPM so I could lower my GPH to about 25 and going further per gallon. A little slower but more than made up for it in less fuel burned. Remember the film, The High and the Mighty? That's how they got to San Francisco.

Now, how do you compare a 4.1 to 1 vs 2.73. to 1? The car with the 4.11 will always accelerate faster but going on a trip, it will always burn more fuel in the same distance traveled. Increasing the tire diameter will always decrease the engine RPM and the distance in feet the pistons travel per mile. Tire weight has nothing to do with it in the real world. Changes to the gear ratio or the tire diameter will always change the engine speed.

Pierce

Re: Tires - Michelin 2004 U320 - Steer vs. Drive tires - 275/80R22.5 vs. 295/80R22.5

Reply #69 – April 26, 2021, 10:23:03 pm

Ok. I can't give up this easily.

Here is a new plan: Since I need new tires anyways, I will buy two of the Michelin X Coach 295/80R22.5 and install them for the steering axle. If it turns out they hit anything under the wheel well, they come out and get moved into the tag or drive axle. I would then buy the smaller 275/80 for use in the steering axle and forget about this whole idea for good.

Question: I would like to cover the edge of the metal mounting bracket for the air bags and the underside of the wheel well for the steering axle with something that will show that there is interference. What can I use for this test? Chalk?

Does anyone know the upper limits of the onboard air compressor? Is it 120 psi? The reason for asking this is that I would like to use the onboard compressor to air up the tires. It will be a lot easier to air up the X Coach 295/80 tires to 100 psi from the onboard compressor than 115 psi or higher when using the 275/80 stock tires.

I have built this whatchamacallit thingy for airing up the tires: https://www.youtube.com/watch?v=n5fK54DKWP0

Re: Tires - Michelin 2004 U320 - Steer vs. Drive tires - 275/80R22.5 vs. 295/80R22.5

Reply #70 – April 26, 2021, 11:24:40 pm

Paint the brackets with spray paint, if it wears off you will see it , if not you will have repainted them. Win win situation
Good luck
David
PS: drive tires make more road noise than steer tires

Re: Tires - Michelin 2004 U320 - Steer vs. Drive tires - 275/80R22.5 vs. 295/80R22.5

Reply #71 – April 27, 2021, 12:46:34 pm

Quote from: cucotx – April 26, 2021, 10:23:03 pm

Ok. I can't give up this easily.

Here is a new plan: Since I need new tires anyways, I will buy two of the Michelin X Coach 295/80R22.5 and install them for the steering axle. If it turns out they hit anything under the wheel well, they come out and get moved into the tag or drive axle. I would then buy the smaller 275/80 for use in the steering axle and forget about this whole idea for good.

Question: I would like to cover the edge of the metal mounting bracket for the air bags and the underside of the wheel well for the steering axle with something that will show that there is interference. What can I use for this test? Chalk?

Does anyone know the upper limits of the onboard air compressor? Is it 120 psi? The reason for asking this is that I would like to use the onboard compressor to air up the tires. It will be a lot easier to air up the X Coach 295/80 tires to 100 psi from the onboard compressor than 115 psi or higher when using the 275/80 stock tires.

I have built this whatchamacallit thingy for airing up the tires: https://www.youtube.com/watch?v=n5fK54DKWP0

I added a second ball valve so it can be used as a gauge without hooking up air.

Re: Tires - Michelin 2004 U320 - Steer vs. Drive tires - 275/80R22.5 vs. 295/80R22.5

Reply #72 – April 27, 2021, 10:39:21 pm

Quote from: cucotx – April 26, 2021, 10:23:03 pm

Does anyone know the upper limits of the onboard air compressor? Is it 120 psi? The reason for asking this is that I would like to use the onboard compressor to air up the tires. It will be a lot easier to air up the X Coach 295/80 tires to 100 psi from the onboard compressor than 115 psi or higher when using the 275/80 stock tires.

I have built this whatchamacallit thingy for airing up the tires: https://www.youtube.com/watch?v=n5fK54DKWP0

If you have this compressor, as does ours, 100PSI is the limit.
THOMAS 1/10 hp HP Piston Air Compressor, 12V DC, 100/100 Max. PSI Cont./Int....

If you're talking about the engine driven compressor, 120-125 PSI, depending upon the setting of the governor. Our governor is set to 125PSI and it takes a long time to inflate over 100PSI. To get the tires over 100PSI you have to finish airing the tire just before the governor unloads the compressor.

Greg

Re: Tires - Michelin 2004 U320 - Steer vs. Drive tires - 275/80R22.5 vs. 295/80R22.5

Reply #73 – April 27, 2021, 10:56:35 pm

I set mine to 130 makes airing the tires much easier.

Re: Tires - Michelin 2004 U320 - Steer vs. Drive tires - 275/80R22.5 vs. 295/80R22.5

Reply #74 – May 13, 2021, 07:50:40 pm

Order for 6 Centramatics wheel balancers for the bus.

From Centramatics Tech Support:
- For the steering tires: Part 700-720. A pair for $199.
- For the drive axle: Part 600-640. A pair for $215
- For the tag axle: Part 600-640. Since the tag axle has disc brakes and the rim is the same as that for the drive tire, it is the same number.

Total of 6 for all three axles (including shipping): $659.
They have a backlog of orders right now, so ETA for delivery is about 3 weeks.

When ordering from Centramics. Their technical support group will need the following info:

Year, Make and Model of coach
Wheel size
Tire size
Number of studs
Is it DRUM or DISK brakes for the front axle?
Steel or aluminum wheels?
If you have a tag, they'll want to know if that rim looks like the drive wheel or the steering wheel? They also wanted to know if the tag axle had disc or drum brakes.

For my U320, the wheels are:
- Steering, tag axle and outer drive: 22.5 X 8.25 Alcoa Aluminum #883643DB
- Inner drive wheel: 22.5 X 8.25 Accuride Steel Wheel #50408

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