U270 Tire to Wheel Well- Distance When in Travel Mode

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U270 Tire to Wheel Well- Distance When in Travel Mode

January 01, 2020, 04:06:17 pm

Hello.

I am beginning my research on "ride height".

I have a basic question- What should I expect the distance to be between the highest point of the tire and the wheel well above it?

I am only looking for a ballpark range when in Travel Mode. It seems the gap is pretty small compared to SOB coaches.

I did a search of the forum but have not found this specific question answered. I know there is ride height information, but I thought I would ask this more basic question.

Thank you.

-FT

Re: U270 Tire to Wheel Well- Distance When in Travel Mode

Reply #1 – January 01, 2020, 04:50:43 pm

While someone could measure and give you an answer, you might tell us what the ride height is as measured by Foretravel and well discussed here on the Forum. Foretravel has never published tire clearance specs, but have never seen an issue with a coach at proper ride height.

Re: U270 Tire to Wheel Well- Distance When in Travel Mode

Reply #2 – January 01, 2020, 04:55:26 pm

Quote from: wolfe10 – January 01, 2020, 04:50:43 pm

While someone could measure and give you an answer, you might tell us what the ride height is as measured by Foretravel and well discussed here on the Forum. Foretravel has never published tire clearance specs, but have never seen an issue with a coach at proper ride height.

Add to that "with the proper tire size"

Re: U270 Tire to Wheel Well- Distance When in Travel Mode

Reply #3 – January 01, 2020, 05:27:19 pm

Thank you for the help.

I will come back with more information. The coach lives about 30 minutes from me. I will get the tire info, etc. next time I visit.

-FT

Re: U270 Tire to Wheel Well- Distance When in Travel Mode

Reply #4 – January 01, 2020, 05:53:08 pm

Yup, check ride height and also what tires is has. OE tires are listed on the GVWR plaque on the driver's wall.

Suspect 275/80R22.5

Re: U270 Tire to Wheel Well- Distance When in Travel Mode

Reply #5 – January 01, 2020, 06:08:26 pm

IMHO,You should be able to slide your fist over all of the tires.

Re: U270 Tire to Wheel Well- Distance When in Travel Mode

Reply #6 – January 01, 2020, 06:30:37 pm

Quote from: Protech Racing – January 01, 2020, 06:08:26 pm

IMHO,You should be able to slide your fist over all of the tires.

This is my spot check as I walk around the coach checking tires and brake temps.

I usually have an inch of up/down movement of my fist. Probably around 5" space.

Re: U270 Tire to Wheel Well- Distance When in Travel Mode

Reply #7 – January 01, 2020, 06:58:33 pm

Mike, Whose fist, mine, my DW's much smaller fist, My neighbor's MUCH larger fist? Seem kind of ambiguous.

Re: U270 Tire to Wheel Well- Distance When in Travel Mode

Reply #8 – January 01, 2020, 07:06:48 pm

The driver's fist of course.
5in or more. MOL

Re: U270 Tire to Wheel Well- Distance When in Travel Mode

Reply #9 – January 01, 2020, 09:07:34 pm

I found an few posts describing the determination of "ride height".

Am I correct in my understanding that the "simple" version of checking "ride Height" refers to the amount that each air bag has been compressed while in travel mode?

If yes, the measurement of the air bag is to be taken at the uppermost point of the top mounting plate, and the lowest point of the lower mounting plate. The desired distance between these two points should be 8-1/2"? This includes 1/4" for the thickness of each mounting plate.

On the right track?

Yikes!

Re: U270 Tire to Wheel Well- Distance When in Travel Mode

Reply #10 – January 01, 2020, 09:19:07 pm

Quote from: FtRoadTrip – January 01, 2020, 09:07:34 pm

I found an few posts describing the determination of "ride height".

Yes, you are on the right track. It's not rocket science. Try this explanation, and see if it makes sense to you:

ride-height-adjustment-in-motorhome-or-rv

Re: U270 Tire to Wheel Well- Distance When in Travel Mode

Reply #11 – January 01, 2020, 09:25:22 pm

I have a piece of plywood cut to the correct height as shown in the previous posts link, it only takes a moment to slip it over the airbag mounts to check that the ride height is correct.
If you are having work done on air bags just give the mechanic the "cut out" and it makes it so much easier for them to adjust all the ride height valves.

Re: U270 Tire to Wheel Well- Distance When in Travel Mode

Reply #12 – January 01, 2020, 10:37:45 pm

Quote from: FtRoadTrip – January 01, 2020, 09:07:34 pm

...the measurement is to be taken at the uppermost point of the top mounting plate, and the lowest point of the lower mounting plate. The desired distance between these two points should be 8-1/2"? This includes 1/4" for the thickness of each mounting plate.

THAT IS IT EXACTLY.

Re: U270 Tire to Wheel Well- Distance When in Travel Mode

Reply #13 – January 01, 2020, 11:28:24 pm

Thank you all very much.

New to RVing and trying to learn every system at once. I really needed a hobby. Looks like I found one.

-FT

Re: U270 Tire to Wheel Well- Distance When in Travel Mode

Reply #14 – January 01, 2020, 11:39:51 pm

THAT IS IT EXACTLY

To add to that the measurement should be at the bags closest to the bulkheads. Said another way rear bags in the front, front bags in the rear.

Re: U270 Tire to Wheel Well- Distance When in Travel Mode

Reply #15 – January 02, 2020, 08:20:30 am

And the coach must be on level ground.

Re: U270 Tire to Wheel Well- Distance When in Travel Mode

Reply #16 – January 02, 2020, 10:20:39 am

And when you go through the proper set up, walk around and stick your fist above the tire . Now you have an instant spot reference.

Re: U270 Tire to Wheel Well- Distance When in Travel Mode

Reply #17 – January 02, 2020, 10:54:15 am

100% good suggestions.

One other: when adjusting, start with the BACK. Get both sides right on spec.

Only after that do you do the front. The front has only a single ride height valve, so you are "averaging" left side/right side. Obviously, if one side in the back is out of spec, it will affect the side to side height in front.

Re: U270 Tire to Wheel Well- Distance When in Travel Mode

Reply #18 – January 02, 2020, 10:47:31 pm

Thanks again.

Re: U270 Tire to Wheel Well- Distance When in Travel Mode

Reply #19 – January 03, 2020, 12:11:43 am

While starting on level ground seems prudent when setting ride height, why does it matter if you are measuring between the lower and upper air spring mounting plates? Just curious.

Re: U270 Tire to Wheel Well- Distance When in Travel Mode

Reply #20 – January 03, 2020, 08:18:19 am

The HWH system is constantly trying to keep the coach level while in travel mode. If the ground is not level, the ride height valves will compensate, causing the air bag measurements to be uneven.

Re: U270 Tire to Wheel Well- Distance When in Travel Mode

Reply #21 – January 03, 2020, 08:40:55 am

You could probably measure frame to frame, but the simplest constant is to measure the very accessible airbag mounts. Coach must be on level surface before measuring.

Re: U270 Tire to Wheel Well- Distance When in Travel Mode

Reply #22 – January 03, 2020, 09:27:48 am

Quote from: DayDreamer – January 03, 2020, 12:11:43 am

While starting on level ground seems prudent when setting ride height, why does it matter if you are measuring between the lower and upper air spring mounting plates? Just curious.

"Why does it matter?" I too have asked the same question. Consider this quote (by J D Stevens) taken from the source linked below:

"When you level while parked, the leveling system tries to level the coach for the comfort of people, refrigerators, water in containers, etc. While in motion, the leveling system tries to keep the chassis at a constant height above the axles.

When traveling, the ride height (leveling while traveling) will be controlled by the ride height valves. There are two in back and one in front. It is easy to see the mechanisms in the back. Look in the access doors for the batteries and isolator. The ride height controllers are the valves and mounts that look like a big Tinker Toy structures with one rod connected to the chassis and the other connected to the H frame (the frame for the axles and wheels). The valves attempt to keep the distance between the H frame and the chassis at 8" when the coach is in travel mode. When the coach goes around a turn, the chassis will lean outward, compressing the air bags on the outside of the turn and expanding the air bags on the inside of the turn. The ride height valves will attempt to correct by exhausting air from the expanded bags and adding air to the compressed bags. On the next turn in the opposite direction, the valves will again exhaust air from bags on the inside of the turn and add air to bags on the outside of the turn.

Changes in attitude from front to back because of bumps and attitude changes will cause adjustments. It is a dynamic adjustment system with the purpose of keeping the distance between chassis and H frames constant. In travel mode, "level" means that the chassis is the proper height above the H frames. When parked, "level" means the egg won't roll off the counter top while you get out the other ingredients. There are valves and controls for each purpose."

I read this to mean that technically speaking the HWH system in Travel Mode does not give a hoot what kind of surface it is parked (or rolling) on. Level or un-level, uphill or downhill - it doesn't matter. The system will try to keep the chassis at a constant height above the axles. So why does everyone say to park on a level surface when checking ride height?

I think you answered your own question: it just seems prudent. If we remove as many variables as possible from the process, we stand a better chance of satisfactory results. Parking the coach on a level surface means the leveling system has to do less "work" to maintain ride height. The ride height valves and linkage will be relaxed in the "centered" position...the air bag pairs (front to rear and side to side) will be at approximately equal pressure...and we will have provided the optimum conditions for getting the height set correctly.

ride-height-adjustment-in-motorhome-or-rv

Re: U270 Tire to Wheel Well- Distance When in Travel Mode

Reply #23 – January 03, 2020, 09:41:51 am

Quote from: DayDreamer – January 03, 2020, 12:11:43 am

While starting on level ground seems prudent when setting ride height, why does it matter if you are measuring between the lower and upper air spring mounting plates? Just curious.

Not as critical in the back, but in the front, there is only ONE ride height valve. If one side in the front is lower than the other your "averaging" of ride height dimensions will be skewed.

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