Wheel Alignment Time ?

By Rudy Morris

Updated 10-21-07

In my opinion, your wheel alignment should be checked once per year or around 12,000 miles, depending on your driving habits. Regular alignment will save wear and tear on your tires and maximize their useful life.

In fact, you may want to have an alignment done right away.

• If you buy a new coach, your coach builder has the last responsibility to make sure the coach has the proper alignment. Make them an offer...check the alignment (four-wheel), if it is within specs (including thrust angle)...you will pay for the labor involved...if it is out of spec, they pay for the check-up and alignment correction. Yes, a new coach has a good chance of not being within specs on alignment, especially the rear thrust angle! That's because no one in the RV industry that I know of, does a 4 wheel alignment. Try it and let me know the results.

 

• If you buy a pre-owned coach, unless you have maintenance records, you probably have no way of knowing when the last alignment was performed and you should consider having a four-wheel check done sooner than later. I assume you checked the tires thoroughly before you bought the coach. Any abnormal tire wear is a good indicator that the wheel alignment and/or tire balance is out of spec. Also note that most RV tire mfg. recommend changing the tires after Seven (7) years regardless of tread wear!  That is because many MHs do not put that much mileage on the tires to wear out the tread but age, UV damage will cause sidewall rot which threatens the tire safety.

 

On Freightliner XC Chassis, the ride height should be checked and if needed, set correctly BEFORE the alignment is attempted. You may have to request the ride height check be done and make sure they do it first before checking/performing any alignment. I've found more than one F/L dealer who didn't realize the ride height needed to be done first. Incorrect ride height will affect the caster on a front I-beam axle and will affect both caster and camber on an IFS system.

The correct measurements and points of measurement vary depending on the particular model chassis. You should call the F/L technical hotline to get the correct dimensions and points of measurement for your chassis. Also see the new Ride Height info on Tech Tidbits page for a comprehensive table of measurements. Provide this info to the F/L dealer...they usually 'already know' what the measurements are and based on my experience are often wrong, or measure them wrong! 

In NO CASE should you attempt to adjust the ride height yourself. Some of the newer IFS systems have low ground clearance, and adjusting the air valve could cause the chassis to drop...crushing you if you're in the wrong place!

Also, ask for a four-wheel alignment, not just a front-end (two-wheel only) alignment. Many F/L dealers only do a two-wheel alignment which does not check the rear wheels. That is because they do mostly 18 wheel tractors which have shorter wheelbase and usually have dual rear axles...probably don't care about 4 wheel alignment.  It also does not measure the THRUST ANGLE...the measure of whether the front and rear axles are truly parallel to each other and perpendicular to the frame rails. If the thrust angle is out of tolerance, you may experience abnormal tire wear on your rear tires. By the time you find abnormal wear patterns on your rear tires, the damage is done...the tires will not 'correct' the wear even if the alignment is corrected.

The RV chassis builders I'm familiar with, only do a two-wheel alignment. Most chassis builders use a jig to align the rear axle, then fasten it to the frame rails, assuming that the tolerances will be 'close enough' that any abnormal wear will be negligible or go unnoticed by most owners. FCCC in Gaffney uses a 'Bee Line' laser tool to measure the alignment between the front and rear axles. The FCCC thrust angle tolerance is +/- .25 degree! That is a pretty tight tolerance.

However, my 2004 motorhome did not have the correct ride height, or rear thrust angle by either F/L or the coach builder!

I suspect this is true with most chassis and coach builders. 

Updated 10-21-07

Created 4-01-05