J Common upgrades to ride height as a result of installing lower, stiffer springs and possibly aftermarket steering arms with raised spindle locations. Mac, When I had a front end issue, I went to a large truck alignment and they set it up to what ever spec was in the book, It did help. Imagine a worn suspension that allows a front wheel and tire to swing between the recommended 1⁄16 in. The vehicle will pull to the side that is most positive so a little bias will help the vehicle go straight on a crowned road. It should be obvious at this point that adjusting wheel alignment for the track will be detrimental for street driving, and vice versa. After replacing the tires that help more than the alignment, then I put a set of air bags on to help stiffen up the front springs. Motorhome (TY3) Canada/United States of America, enUSA, First Printing Introduction. 228.0 228.0 GVWR (lbs.) There's an art to engineering a motorhome, as elegantly demonstrated in the custom-built PowerGlide chassis. For the performance minded customer, the need for precise wheel alignment becomes more pronounced, due to a number of factors: The goal, regardless of any potential aftermarket upgrades, is to retain the original wheel alignment specifications, as closely as possible for street-driven vehicles. If the wheel leans inward at the top, this is negative camber. However, toe can also be used to alter a vehicle’s handling traits. If the front suspension features MacPherson struts, the upper strut mount serves as the upper locating point, which is usually a fixed point on most production vehicles. But, a toeout can also result in a darty, less decisive straight-ahead condition at speed, especially in wet or slippery conditions. All front suspensions, regardless of design, feature toe angle adjustment, at a location on the steering tie rods/tie rod ends. Since these two lines will eventually intersect, it’s this intersection point that we’re really interested in. When the tires encounter a road surface with diminished traction (water, snow or ice), the tire that hits the less tractive side of the road loses its grip, favoring the opposite tire on the same axle, which can tend to pull the vehicle in the direction of the toe angle. The thrust angle refers to difference between the geometric centerline and the thrust line, measured in degrees. Incorrect wheel alignment conditions affect tire wear and can cause drifting and/or pulling during cruise, acceleration and braking, plus poor directional control. We will show you that simply telling the alignment shop that it's a “P30 Chassis” will almost guarantee you an incorrect alignment. Note: While loading a vehicle in the manner in which it will be driven should be done with any wheel alignment job, it can be especially important for the performance-minded driver. RV Tech Savvy: What’s Wrong With the Wiring on the Motorhome? 24,000 26,000 The thrust line may or may not follow the geometric centerline. "Warning! Track settings are for the track, street settings are for the street. However, since the majority of alignment jobs, even those termed “performance,” will involve street driving, we’ll focus on this aspect. For the street, it’s best to stay within the limit range specified by the vehicle maker. Write CSS OR LESS and hit save. As a rear-drive vehicle moves forward, the front wheels may tend to try to crawl away from each other, while a front-wheel-drive vehicle’s front wheels may try to crawl inboard. This 1⁄8-in. Alignment assumes even greater importance as vehicle performance increases. CTRL + SPACE for auto-complete. If you like MotorHome, pay just $19.97 for 11 more issues (12 in all). Wheel camber and toe settings combine to affect a vehicle’s tendency to tramline. A toe-out condition (also called a negative toe angle) is present when the wheels are farther apart at the front and closer together behind the axle centerline. Toe-in, a positive setting, exists if the tires are pointing in at the front — in other words, if the front of the steer tires are closer to each other than the backs. Stripped Chassis 158" DRW Stripped Chassis 178" DRW Stripped Chassis 190" DRW Stripped Chassis 208" DRW Stripped Chassis 228" DRW Stripped Chassis 242" DRW Stripped Chassis 252" DRW If the wheel is set at a true vertical, this is zero camber. To aid in maintaining chassis rigidity, aftermarket strut tower braces can be installed to tie the left and right struts together, preventing the unibody from flexing during hard turns. Both SAI and IA are measured to verify that the fixed-by design angles are correct. The correct general term is a “Motorhome P Chassis”. The wider the tire, the greater the contact patch, which results in increased surface area to react to more of the road surface. The three factors that affect alignment are toe-in, camber and caster. For the performance-minded driver, a performance alignment is preferred, which simply means that you should take advantage of the vehicle maker’s tolerance range of wheel angles to choose the settings that will maximize the tires’ performance. While static toe (with wheels aimed straight ahead) allows both front wheels to rotate at the same speed and parallel to each other, during a turn the individual wheel toe angles differ when the steering wheel is turned more than 20°. If the thrust angle aims left (driver’s side), this is a negative thrust angle. tiffin-specs. So whaddaya do if you want a “performance” alignment? Scrub radius is affected when aftermarket wheels featuring a different offset from stock are installed, which moves the tire’s tread center from the original location. It can be done though. Caster angle settings for street-driven vehicles should provide a good compromise to achieve an acceptable steering effort, confident high-speed stability and turning/cornering performance. Workhorse and Chevrolet Chassis Motorhome Forum: 2: 03-09-2010 01:42 PM: Wheel alignment. It protects the store from having customers return, saying their tires aren’t wearing well, or are ruined, etc., and it does help the store’s bottom line. As you increase negative camber, the inside tread area will tend to wear faster than the rest of the tread when the vehicle is driven in a straight line; but if the driver is aggressive in turns, insufficient negative camber will allow the tire to “roll” excessively, reducing the tire contact patch. Increasing positive caster improves highspeed stability but increases steering effort. For example, when the steering wheel is turned to the left, the left front wheel will exhibit greater toe-out as compared to the number of degrees that the right front wheel toes in. Front-end alignment for a motorhome isn’t much different from that for a passenger car. Send them to [email protected]. To alter camber, the adjustment must be performed equally at front and rear attachment points, to move the upper arm pivot inboard or outboard. This approach allows you to refer to and consider the rear, while a total four-wheel alignment allows adjusting of both front wheel angles as well as rear toe. Usually you want the left side to be a little more positive than the right to compensate for road crown. Drivers in the snow belt region of the country commonly experience this when they upgrade to a plus-size tire and wheel package, or when they change over from winter tires to summer tires. Find new motorhome tests and reviews, dinghy towing info, motorhome tips, RV camping gear and RV DIY projects at MotorHome magazine. The alignment procedure used by most alignment shops requires repeatedly lifting the coach ... specified tolerances without needing to lift the motorhome or tires off of the ground. © 2020 Good Sam Enterprises, LLC. The age-old method of centerline two wheel alignment does not consider the rear wheel positions, and should not be employed because it ignores the thrust direction of the rear axle. Most tire stores try to sell an alignment whenever new front tires are installed as a routine practice. Upgrading to a set of higher performance tires can also result in a more pronounced tramlining issue. Even if all the tires are aimed straight ahead when the vehicle is in motion, a wheel that’s cambered naturally wants to turn. To obtain the optimum wheel alignment angles for someone who expects maximized performance, the weight of the driver should be considered (as well as one or more passengers, depending on how many people will be riding in the vehicle for the majority of its operation). This will allow you to better tune the wheel angles in a loaded condition as the car will normally be driven. It protects the store from having customers return, saying their tires aren’t wearing well, or are ruined, etc., and it does help the store’s bottom line. 13) Perform alignment and recheck. Get a FREE issue of MotorHome magazine. Sign up for your trial subscription and you’ll receive a FREE issue. I recently replaced all six tires with new Goodyear tires. As some of you know, my company supplies most of the wheel alignment equipment for Ford, as well as most other manufacturers. John Arch l Via email. The steering axle’s caster angle has a major influence in directional control. John Arch l Via email. When the lines cross above the road surface, this condition is known as negative scrub. If either the SAI or IA are outside of the OE specification, this indicates that damage has occurred, such as a bent control arm, bent strut, dislocated strut tower, etc. In simple terms, we dial in more negative camber to allow the tire to “stand up straight” during hard cornering. The performance- minded driver will benefit from a setting that’s negative. F53 Chassis Cab/ F59 Commercial Chassis 91 esourcebook.dealerconnection.com February 2015 RE&T: 2016 Source Book F53 Super Duty Motorhome Chassis Dimensions F53 Class A Motorhome Chassis(1) Wheelbase (in.) When the lines intersect below the road surface, the condition is called positive scrub. Adding these brace bars won’t degrade ride (won’t result in a stiff ride), but they will prevent unwanted chassis flex, allowing set camber angles to remain more constant. 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