RV Tech: FMCA Tech Talk
Replacement Tire
I have a 2003 Newmar Dutch Star motorhome on a Spartan chassis. While traveling through Nevada recently, we experienced tread separation on an outer dual tire. I called around looking for a replacement (275/70R22.5). Most places either were closed or did not have what we needed, but we finally located a tire and the shop installed it.
Now my problem: The damaged tire was a Goodyear G670RV, installed new in February 2012. It is listed as 37.6 inches in diameter; 548 revolutions per mile. The new tire is a Michelin XZA2 Energy all-position tire. It is listed as 38.0 inches in diameter; 545 revolutions per mile. So, the difference in diameter is 0.4 inches. Just how at risk am I?
I know that duals should be replaced as a unit; the shop had only the one tire in stock. An internet search indicated that same-set dual tires may be up to 3/4 inch different, and the “new” condition of both installed tires is within that criterion. However, the Goodyear tires were installed more than five years ago and have worn to some degree, and therefore the diameter is now suspect.
John Heimer, F368508
Emery, South Dakota
You should have had the tires rotated with the new tire installed on the front axle so that all four duals match. You could then have replaced the other front tire with a matching tire at your earliest convenience. If you have room, consider purchasing a spare tire and rim so this won’t happen again.
Also, the publication “Michelin RV Tires” states: “Tires mounted in dual must be matched so that the maximum difference between the diameters of the tires does not exceed 1/4-inch diameter or a circumferential difference of 3/4 inch.”
Shimmy Shake
I have a 2004 Honda Pilot with 145,000 miles, and it has been towed about 30,000 miles. After towing, I experience an intermittent front-end shimmy at 20 to 23 miles per hour. I have balanced the tires, installed new brakes and tie rod, and aligned the front end, without any improvement. I am thinking the transmission may be the source of this shimmy. The shimmy doesn’t happen when the vehicle is being towed. It is sporadic in nature but seems to be more of an issue after the vehicle has been towed. The most predictable aspect is it occurs at 20 to 23 mph and goes away as I accelerate to highway speed. The car never acts up or feels insecure other than the shimmy.
Norwyn Newby, F325672
Bend, Oregon
Two or three things should be checked. Since you’ve already had the vehicle aligned, the shocks may be worn out. Or, you might have a bent rim, in which case, try rotating the tires. You also could be correct about the transaxle — the constant-velocity (CV) joints could be severely worn.
Noisy Engine
An RV Tech Talk letter from Ed Antus described extremely loud fans that come on as the engine of his 2005 Fleetwood Bounder gets slightly warm (“Noisy Engine,” December 2016, page 20). The noise may not be from fans. My 2008 Bounder made a loud noise when I got up to speed on the highway because of resonance from the round tubes of the coach’s grille. I took the plastic caps off the ends, pushed wooden dowels into the tubes, and then replaced the caps. The noise was gone. Hope this helps.
Jim Molleca, F392173
Birdsboro, Pennsylvania
Thank you for writing to share your fix with fellow members.