Steering geometry in trucks of same series but different wheelbase

[Ben L.]

Hello,

I was wondering whether trucks of the same series, for example Ford F350 series, which come in several wheelbase options (Single-cab, Crew-cab, etc...) have the same steering geometry?

As I understand it, different wheelbases requires different knuckles and/or steering linkages, but my intuition tells me that maybe those differences are minor enough so the same steering geometry is used for the entire series?

Thanks in advance

 

[GregLocock]

Typically the same linkage geometry is used. The main effect of this is the Ackerman, and the turning circle. It'll also affect the yaw gain and the understeer. I can't remember running different steering ratios in different wheelbases but that would be possible, which would help compensate for those two.

Cheers

Greg Locock


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[BrianPetersen]

All the suspension bits that I've seen for trucks with wheelbase variations, and that includes the upcoming next-generation Ford Superduty F-series (Customer of mine is going to be making those parts!), use the same bits no matter the wheelbase, including the steering rack/box. Ackerman is never perfect anyhow, and a little bit more or less scrub when the steering is cranked way over one way or the other is neither here nor there for the normal range of variation in wheelbase.

 

[SwinnyGG]

Also comes to bear that the platforms where steering gear and geometry are shared across multiple wheelbases are almost always platforms where ultimate steering feel/response/limit handling aren't major concerns (ie, trucks).

Vehicle families which share a 'platform' will have similar, but not exactly the same, steering gear - in that case the geometry is typically adjusted to match the goals of each chassis individually.

 

[GregLocock]

The most common tunable in hardware is the C factor of the rack, ie the overall steering ratio, and the tire selection of course. The latter is acceptable to some extent, the poka yoke implications of running outwardly identical racks in the assembly plant is not. I think I have been on programs with more than one C factor, but lately it is mostly handled in the tires/epas tune.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

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