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1995 Roadmaster Chassis - Should the Ride be Smooth?


Joe Lee

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Hi! I’m bringing a ‘96 Crown Royale Signature back from the dead. (And, right now, I don’t think it wants to live!)

My question is about the quality of the ride. When I go over bridges or hit the dreaded pot hole, sometimes it feels like my teeth could be rattled out of my head!  I have 4 year old air bags and new shocks. I thought it would ride like an old Ford LTD!  Perhaps my expectations were to high!

 

Please let me know what your ride is like and/or if you have ideas for me to improve my ride quality. 
 

Thanks!!

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I have a 2009 Monaco Knight DFT 40 foot. I put new Koni shakes on 1 1/2 years ago thinking it would improve the ride. It’s not better. I don’t know what the life expectancies of air bags are. Maybe that is both of our problems. Maybe some one will chime in that knows more than I. 

Jim m

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All, I had the same problem with my 2002 Monaco Knight.  What I found out was my ride height adjustment was off and that the tires ( Michelin X2’s ) actually should only be running 88 psi in the front and 85psi in the back after I went and got each axle weight tested) in lieu of the 100psi it said in the manual.   The difference was night and day.  I made a 100 day trip across the US and could not believe the difference!!!!!!   

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Thanks for all the comments. 
Chargerman - I’m running 110 psi in the front and 100 in the rear. I’m just going by the book. I have Toyo tires. Not sure if I can lower the pressure, but I’m open to whatever could help!

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The "book" ... does that mean  110 and 100 were from the chart for the brand and size of the tire based on the weight on that axle?   My coach rode very hard when I first got it... tires were inflated to 100 plus psi, ran it across some CAT scales, got the front and rear axle weights, seems the tire pressure chart said for those weights I could run as low as 85 psi... I run 90 and the ride is much better.   I do not believe the rubber in the air bag gets hard with age and makes the ride rough.... JMHO.

Ken

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Joe,

Don't worry about your air bags.  If they are not broken then they are doing their job of supporting the weight of the coach.  The coach ride height system will adjust bag pressures using rear bags to adjust left and right level and front bags to adjust front to rear level.

Don't worry about your shocks either.  Your said they are new.  They dampen the bouncing of the suspension system as the tires hit bumps and holes.

What you can do is adjust tire pressures so they are adequately supporting weight while flexing enough to absorb bumps.  But first you need to weigh the coach so you know the weight at each corner so you know what weight each tire has to support.  Then your need to refer to tire manufacturer's tables to determine required pressures.  You said you have Toyo tires so you need to get the Toyo inflation pressure tables.  Info is available on their website.  Too high pressures will give you the jarring ride you are discussing.  Keep in mind these are big heavy coaches and you should expect to have some jarring.  Doubtful you'll ever get the floating smooth ride.  Best to shoot for stable controllable ride.

Rick M

2000 Executive 42ft

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Joe,

Rick M "hit the nail on the head" !!! Your tire pressures are most likely way too high for the weight plus cargo.

Get your corner weights done first with the coach loaded for travel, plus waste tanks empty, fuel tank full, fresh water tank full.

Then as Rick said consult the weight/psi charts for your brand, model and size of tires you are using.

The attached Michelin Brochure on page 5 & 6 has a good chart to use for having your coach weighed correctly to obtain the needed information in order to inflate your tires to the proper cold inflation psi.

Safe travels!

Michelin RV Brochure June 2009.pdf

Edited by Dr4Film
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After adjusting my tire pressures I still experienced quite a bit of porpoising, especially at bridge joints, etc., at first I thought that shocks were my problem, however, ruled that out after learning that I had fairly new Bilstein shocks.  The solution came when I installed (4) new Comfort Control Valves on my front air bags, they are manufactured by Source Engineering, Inc., in Elmira, OR, they sell for $100 each and take about 15 min. each to install in the air lines to the air bags.  Our '05 40' Beaver w/tag has a much smoother ride and even handles better on curves and when being passed by trucks.  This has been the least costly upgrade we've made to date!  Look up Source Eng. on line, call and ask for Jim!

 

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Wow!  All great information. I will weight it, consult the manufacturer’s chart(thanks for the chart, Dr4Film!) and look into new comfort control values. 
 

This is a great community of people!  Thanks for the support!

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Three things...

Just to echo what has already been said, NEVER, NEVER go by the manual to determine correct tire pressure for your rig. It will probably be bad for the rig and offer a bad ride. The manufacturer is the only one that knows how his tires behave under load.

One more thing, be careful when replacing tires. You can find tires that fit your rig that are actually made for trucks that typically carry loads greater than your rig. Those tires have heavier sidewalls and you will regret the ride difference. Ask your tire supplier or the tire manufacturer if their tires are designed for a Class A RV.

And lastly, don't think your rig is porpoising if it lunges down and up once after hitting a bridge joint. Once down and up and then settling for normal ride height is normal for good shocks.

-Jamie

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2 hours ago, Joe Lee said:

Wow!  All great information. I will weight it, consult the manufacturer’s chart(thanks for the chart, Dr4Film!) and look into new comfort control values. 
 

This is a great community of people!  Thanks for the support!

Just a reminder here.  You need to get the chart for Toyo tires.  Micheline tire inflation tables show lower pressures than Toyo.

Rick M

2000 Exec

2 hours ago, Joe Lee said:

Wow!  All great information. I will weight it, consult the manufacturer’s chart(thanks for the chart, Dr4Film!) and look into new comfort control values. 
 

This is a great community of people!  Thanks for the support!

Here is the Toyo table.

rv_inflation_tables.pdf

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