Truck Equipment Glossary - R

Radius Rod
Found in several automotive applications, most commonly for keeping the rear axle in correct position when starting and stopping.  
 
Rear Axle Ratio  
The numerical ratio of the drive shaft speed to the speed of the rear axle. 
 
Recovery Vehicle/Wrecker

Vehicle used to retrieve and lift tow other vehicles.  
 
Reefer
Slang for insulated van body equipped with refrigeration for controlling temperatures.
 
Reflectors
Glass or plastic prism lenses which reflect light.  
 
Regrooved Tire

A tire, either original tread or retread, on which the tread pattern has been renewed or a new tread has been produced by cutting into the tread of a worn tire to a depth equal to or deeper than the molded original groove depth.
 
Resisting Bending Moment (RBM)
A calculation used to compare frames of different section modulus and of different material. It is the product of the section modulus times the yield strength of the frame material. The formula is expressed as:

  • RBM = Section Modulus x Yield Strength

    It is readily apparent from the above formula that the yield strength of a frame is as important as the section modulus. The RBM should, therefore, be taken into account whenever frames of unlike material and section modulus are being compared. See Yield Strength.

Ridge Pole
Member that can be located in center longitudinally on an open top van body to support a tarpaulin in a tent like manner.  
 
Rim Pull
See Tractive Effort.  
 
Riser
Steel or wood section between chassis frame and van body underframe to give proper tire clearance and/or required ground-to-floor height.
 
Road Rolling Resistance

A measure of the retarding effect of the road surface to forward movement of the vehicle. Varies with the type and condition of the road as different road surfaces offer various resistances to the wheels of a truck. A concrete surface offers 12.5 lbs. of rolling resistance per thousand pounds of gross weight; gravel, 25 lbs.; and sand, 75 lbs. This is a vital factor in determining power and power train requirements.
 
Roadside
The left or driver’s side of the vehicle when viewed from the rear, opposite side from Curbside. 
 
Rolling Radius
Height measured from center of axle to the ground.
 
Roof Bow
Transverse member in roof of body.
 
Roof Rail
Member running longitudinally that connects the roof to the side of a body.  
 
Rope Ties

Rings, hooks, cleats or knobs attached to body wall frame members for use with lashing either inside or outside; liner slats or bars attached to wall frame members for lashing.
 
Rub Rail
Member running longitudinally providing rub surface on the side of a body.