RV Handling Issues

[markopolo-ClassB]

I thought a very general discussion on improving handling issues might be useful for folks who don't know where to start to correct problems.

I'm not an expert in this.

I'd start with:

1. tire pressures - assuming the tires are still good
2. if equipped with air suspension bags - check and adjust pressure
3. alignment - take it to an alignment shop & get it aligned
4. if there's a shake or shimmy at speed then the wheel balancing could be needed
5. new shocks - heavy duty shocks like Bilsteins should get things like porpoising under control
6. have bushings inspected and replace if worn out
7. install rear air bags (I think I'd do this before installing a sway bar - comments needed)
8. install rear sway bar
9. install new front coils

Hopefully, for your wallet, you won't have to go down too far on the list.

As mentioned, I'm not an expert. There are members here that truly understand this stuff and are very helpful answering questions.

 

[Bruceper]

Consider upgrading from rubber bushings to polyurethane. They might be a little squeakier, but they are more durable. This can be done at any time, but typically done at replacement time.

Shocks. Some older RV's came with skinny automotive shocks. These worked properly for about a week (exaggeration). New shocks for RV's are heavy duty and made to withstand the 8-10,000+ pounds we have on them.

Do you know why it's called a lube shop? They also lubricate grease points in your suspension. Yes you can change your own oil to save money, but missing out on the lube can actually lead to noises and squeaks and can end up costing you money in early parts replacement. Most newer vehicles do not require lubrication in the suspension components as they are sealed, but it doesn't hurt to ask your dealer if it's required!

Note - Lube shops do oil changes and lubes. NEVER use a lube shop to do any work on your transmission or cooling system. Just say "no thanks". Please please please go to a transmission shop for any trans issues.

Sway bars help reduce body roll on corners and on uneven surfaces. This is a simple answer of what a sway bar does. Wikipedia has an excellent article on anti sway bars I would invite anyone to look at. It has general and technical information so it's good for everyone. Many vans don't have them. And remember bigger is not always better as if you go too big you could be restricting what your suspension is supposed to be doing.

Cheaping out on tires is easy to do, since one brand looks like all the other tires. But if you go cheap you might feel like you're driving on marshmallows. The issue is the sidewall stiffness. Two brands can look the same, and have the same specifications, load ratings, ply layers etc, but drive very differently.

Gimmics don't work. Ever. They say they can reduce air drag, increase fuel mileage, reduce the side effects of your medication and restore your hairline for only $14.99 a month. Save your money.

Weigh yourself! By that I mean weigh your van when it's loaded, with you and your passengers in it. Weight the front and back and if possible right and left side. Right and left should be close to even, if it's not you can feel it when you corner. You might not know why your van makes left turns differently than right ones. Your front and back weight should be under your GAWR for each axle. You may need to shift things around to balance yourself out.

Hope this helps someone!

 

[booster]

Marko has hit all the high points of general concerns and things to look at. Trying to fix specific handling complaints or issues is nearly impossible until all the parts are in good condition.

In the inspection area, I would start with the front end parts. Ball joints, tie rods, idler and steering arms, control arm pivot bushings (very often overlooked but often bad in older vehicles), sway bar bushings and end links, steering gear, steering shaft u-joints, wheel bearings. In the rear, you have the front spring eye bushings the shackle bushings, and the spring perch locating pin a u-bolts. It is a lot of parts, and many are kind of hard to check because they really should be in the operating position, eg with the weight on them when you check them. Ball joints are an exception and are usually checked without weight, using a pry bar. It is very useful to have a trusted suspension shop to check this stuff out, but really is important if you want to have a good starting point. I went through this on my old Buick Roadmaster last winter. 20 years old, front end all original, sagging springs, very cracked up a-arm bushings. I just replaced it all rather than piece it together and wind up doing more later. I replaced all the parts except the steering gear, including springs and a-arms for something in the $500 range.

Get the best shocks you can afford, Bilsteins are great. If you get other high performance shocks, check carefully for reviews to see if they may be to stiff. Most shocks are single damping force, so to get control better they are very highly damped and can give a rough ride, especially on small bumps. Bilsteins are variable damping so they can have good control and still be soft on small bumps.

Urethane bushings have been mentioned, and they are a good product, but not as much an improvement as they use to be IMO. Most of the end links and sway bar bushings are now some sort of polyethylene (I think) material, which is quite hard, very slippery, and quiet. Urethane's major benefit had always been the stiffness, so less deflection, so that is now gone. Urethane shock mounts are very good, durable, but often pretty noisy. The stock Chevy 3500 shock mount is one of the best I have seen, and is much better than what Bilstein supplies with their shocks. There are places you don't want to use urethane because they do a sliding bushing setup instead of twisting (bonded to the parts) rubber. This would include a-arm bushings and spring eyes.

After you get all this good, you can consider getting a good alignment, to get a baseline of handling to compare to. At this point I would shoot for the middle of the manufacturer's specs but make sure you have about 1/16" of toe in, and the proper amount of caster "stagger" between the right and left. Don't let them tell you in it is all "in the green" and OK. You can be within on everything and handle very poorly as the ranges are huge. Get a printout of what they final settings are for later reference, then go out and drive it under varying conditions and make some notes. Does it pull to one side, does it run down right and left crowns the same (it really shouldn't in most cases, as it will go down a left crown a little faster), does it take big steering corrections to stay straight, do trucks blow it around, does it feel twitchy or dart one way or another, does it pound hard into bumps or porpoise? Basically anything you don't like about driving it.

Now you can start looking at what you need/want to do to improve things.

 

[markopolo-ClassB]

Thanks Bruceper & Booster - excellent info!

 

[Davydd]

I have talked to many Sprinter owners and one common complaint has been wheel balance especially when driving above 70 mph. We noticed that in ours. We bought new Michelin Defender tires from Discount Tire and I noticed there were way more wheel weights than we had before. In fact one wheel had 5 weights! I asked why so many and got the retort that that's what they needed to balance the steel wheels. It looked strange and I suspect MB could not or would not dare deliver a van in that condition. As it turned out, Discount Tire was right. I got up to 80 mph and not a bit of shimmy.

 

[booster]

On my last post, I mentioned that once everything was fixed, it was time to drive a bunch to find out what you like and don't like. I dug around and found a couple of documents that I have used many times for relating real world driving to the setup of the vehicle, both settings and parts. I have never tried to attach a multpage PDF, but we will see if it works.

First what the alignment numbers mean and what changes will give you.

http://www.classbforum.com/forums/attachment.php?attachmentid=3436&stc=1&d=1465516099

Then what different parts may do for you, or other changes like tire pressure, size, etc

http://www.classbforum.com/forums/attachment.php?attachmentid=3437&stc=1&d=1465516099

These are both very good reference and a good place to start when you compare you test ride to what you want to accomplish.

 

[booster]

Downloading PDF files to read them sucks, but the forum doesn't work with them inline like pix. I think it will take two post do to the limit of attachments, but I will put the first PDF about alignment effects in as JPG pix to see how that works.

Two more pages on next post.

 

[booster]

Continuing alignments effects from previous post

 

[booster]

This will be the second PDF file about how suspension changes give different effects.

 

[Tenbike2]

Jim here... We have had the vibration on our sprinter camper since new. Am in the process of trying to identify what is causing it. Took the van in for "road force balance". They dynamically balance the tires. They were only slightly out of balance. Then up to 1400 lbs. of pressure is applied to the wheels while they are spun. The difference in push back is measured to check for roundness. They would like to get it below 15 lbs. usually they need to rotate the tire on the rim to match the flat on the rim and bulge on the tire. Supposedly if it exceeds 25lbs. It is detectable by the driver. The best they were able to achieve with the stock tires was 58 lbs. of push back . Have not yet pursued this but I wonder if the tires being out of round may be part of the issue and installing after market tires that don't have this issue might help resolve the problem.

 

[Bruceper]

It's possible. Not all tires are made the same, and different processes can result in different results.

However, if it is an "out of round" issue, there are actually some shops that can fix that. Some bigger shops that do retreads for big rigs may have the equipment to do this.

 

[Tenbike2]

Bruceper Thanks for the suggestion. I do think I will take it in to a sprinter dealer first to see if they will resolve the issue.( we only have 4000 miles on a new vehicle and the issue has been present since new)

 

[booster]

Bruceper Thanks for the suggestion. I do think I will take it in to a sprinter dealer first to see if they will resolve the issue.( we only have 4000 miles on a new vehicle and the issue has been present since new)

With it that new, the dealer is far and away the best choice, they should do whatever it takes to fix it.

That said, if nobody can find it, there is one more place to look. The rotors. The balancing tolerance on most rotors, including OEM, is not very good, and often can cause perceptible bouncing or vibration. The only consistently good ones that I have seen are the high performance aftermarket rotors like Brembo or Hawk. My old Buick Roadmaster Wagon had an annoying small vibration, at 67+mph, to it even since I got it 3 years. Had good Michelin tires, I rebalanced the wheels twice, moved wheels front to rear, nothing changed. Checked the front rotors for balance, and although both had factory balancing holes in the them, one was way off of balance. Did some more balance holes and vibration totally disappeared. This is the third vehicle (2 were ours) that the impossible to find vibration turned out to be rotors, so it is certainly not terribly rare, I think. Most rotors can easily be checked on an old school bubble balancer or vertical static balancer (old Snap-on balancer).