As some of you know, my company supplies most of the wheel alignment equipment for Ford, as well as most other manufacturers. of toe-out when it encounters a rut in the road. © 2021 Hearst Business Publishing, Inc. | This becomes more of a factor if the driver tends to be on the heavy side. We will show you that simply telling the alignment shop that it's a “P30 Chassis” will almost guarantee you an incorrect alignment. Front end alignment isn't something that most RV'ers will want to do and will opt to having a pro do the job. 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. If caster is to be adjusted, only one end would be adjusted. 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. Incorrect wheel alignment conditions affect tire wear and can cause drifting and/or pulling during cruise, acceleration and braking, plus poor directional control. Both SAI and IA are measured to verify that the fixed-by design angles are correct. An excessively negative scrub radius tends to increase steering effort, while excessive positive scrub radius (where the load of the tread is moved moves further outboard) can not only affect handling and ease of steering, but can overstress wheel bearings as well. Typical toe-in specs vary from one-thirty … The more “sensitive” the tire, the more susceptible the vehicle is likely to become to road irregularities, since wider tires with shorter sidewalls and/or tires that feature stiffer sidewalls have a greater tendency to “track” the road surface. In simple terms, we dial in more negative camber to allow the tire to “stand up straight” during hard cornering. 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. Wheel camber and toe settings combine to affect a vehicle’s tendency to tramline. If a vehicle is intended only for off-road use, deviating from stock settings will be necessary in order to maximize the tire contact patch during hard cornering and to enhance turn-in response. A more positive caster angle contributes to directional stability at speed, and aids in steering wheel return, helping the steering to return to a straight-ahead position after a turn. The performance- minded driver will benefit from a setting that’s negative. 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. This design feature reduces the tendency of tire scrub during turns and reduces the turning radius of the outboard wheel, reducing the car’s tendency to turn-in too quickly, while providing reduced recovery effort when the vehicle direction changes. Black Book. Since these two lines will eventually intersect, it’s this intersection point that we’re really interested in. Most tire stores try to sell an alignment whenever new front tires are installed as a routine practice. Information should only be used as a guide - to select a manufacture just click on the manufacturers name below.. Toe is specified at 0.06 +/- 0.25 (per side I think). If the front suspension features upper and lower control arms, the upper arm will likely be adjustable, either via the addition or removal of shims (between the upper arm and frame) or via eccentric bushings. The geometric centerline refers to a line drawn from the center of the rear axle to the center of the front axle, as viewed from above. An increase in toe-out can reduce an understeer tendency and will enhance initial turn-in during cornering. The toe angle is critical in terms of tire tread life. Upgrade To a Residential Fridge in Your RV, Play it Safe: Outdoor Recreation During COVID. Manufactured in 23 and 26 ft (7.0 and 7.9 m) lengths, the design was noted for its front-wheel drive and its low profile, fully integrated body. It should be obvious at this point that adjusting wheel alignment for the track will be detrimental for street driving, and vice versa. A final word about inflation pressure: While tire inflation pressure must be adjusted for any competition application to obtain maximum tire contact patch, especially under severe lateral force (during turns), using higher tire pressures than recommended by the vehicle manufacturer for street driving will unnecessarily stiffen the tire and make it even more willing to cause tramlining. Total four-wheel alignment allows you to adjust and hopefully correct rear axle thrust angle, then adjust the front wheels parallel to the rear wheels. Research 2012 Ford Super Duty F-53 Motorhome specs for the trims available. Alignment Specifications and Procedures W6000345 (Effective from September 2000) Over the past two years, representatives from Volvo Trucks North America actively par-ticipated, along with twenty-two companies, in developing Recommended Practice 642 entitled “Total Vehicle Alignment: Recommendations for Maximizing Tire and Alignment A vehicle’s thrust line represents the “aim” of the rear axle, as viewed from above. 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. Usually the amount of offset change is kept to a minimum, and vehicle tracking remains relatively unchanged. If the vehicle owner intends to use the vehicle for occasional autocross events, you can increase tire pressure to suit track conditions, but he must drop pressure to factory spec before driving on public roads. If the thrust angle is off zero, this can contribute to vehicle dog-tracking (crooked body relative to direction of travel), increased tire wear and unequal left/right turning. For high-performance driving, a negative camber angle is preferred, to compensate for the lateral forces experienced in cornering. 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. Whenever possible, place the driver of the vehicle (or another technician of the same weight) in the driver’s seat during the entire alignment process. In some cases, the new wheels will have slightly less offset than the original and in other cases, slightly more. It can be done though. Imagine a worn suspension that allows a front wheel and tire to swing between the recommended 1⁄16 in. 14) Once satisfied with alignment. The vehicles actual caster angles are within specifications. Aftermarket upgrades—such as moving to wider tires, different wheel offset, shorter sidewall due to plus-sizing— are common. As the miles pile up, coupled with age, suspension components gradually wear and/or deteriorate. 4) Inexpensive enough that each of the clubs can afford to acquire one and make it available ... the factory specs … Track settings are for the track, street settings are for the street. Installing wider tires or a plus-size tire and wheel package usually requires using wheels with a different offset than the vehicle’s original wheels. 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. I recently replaced all six tires with new Goodyear tires. It should drive like an SUV now. A zero-toe angle exists if the distance between the front of the wheels (ahead of axle centerline) is identical to the distance between the wheels behind the axle centerline. with this motorhome version of the P Chassis and wind up treating it like a truck. If a vehicle features rear wheel toe adjustment, we can achieve optimum wheel alignment using the total four-wheel alignment, which includes adjustment of all four wheels, allowing toe adjustment to bring the thrust angle to ideal zero, or as close to zero as possible. Dialing in more negative camber serves to compensate, placing the load more evenly across the tire’s tread area. If the wheel leans out at the top, this is positive camber. You may have been in my predicament of seeing tire wear, pulling on the steering wheel, and loss of steering control. This allows you to adjust the front wheel angles relative to the rear wheel angles, regardless of the geometric centerline. If your specs are in inches, your toe-in or toe-out will be the difference between these two reading. There's an art to engineering a motorhome, as elegantly demonstrated in the custom-built PowerGlide chassis. The correct general term is a “Motorhome P Chassis”. If you like MotorHome, pay just $19.97 for 11 more issues (12 in all). As viewed from above, if the thrust angle aims to the right (passenger side), this is a positive thrust angle. This 1⁄8-in. The caster in this vehicle is read four degrees plus or minus one half degrees (.5°). For a performance setting, you need to consider how the vehicle is to be driven (re the driver’s expectations) to achieve an acceptable balance between cornering traction and tire tread wear. 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