Straight Axle Caster Question

[Polara Pat]

Alright, technically it's an I-beam axle but we all know what I'm talking about. We used an axle from a '65 A-108 for our altered and it has between 4* and 6* of caster built into it. This car is pretty much race only so just wondering how much caster I should be running to avoid bump steer. Any and all advice is appreciated.

Thanks, Pat

 

[Centerline]

I run about 8 degrees on my 32 Ford highboy which works very well on the street. However, the angle has to be measured at ride height because the rake angle of the chassis has to be taken into account to get a true reading. The more "rake" you have the less caster you're axle will actually have so that built in 6 degree caster may actually only be giving you 3 or 4 degrees if your chassis has much rake.

 

[Cranky]

Straight axles are usually not plagued with bump steer....or at least not very much if any since they don't have tie rod ends coming off a center drag link but they do however have what's called roll steer but if your car launches up evenly, that will be reduced.

 

[Polara Pat]

I run about 8 degrees on my 32 Ford highboy which works very well on the street. However, the angle has to be measured at ride height because the rake angle of the chassis has to be taken into account to get a true reading. The more "rake" you have the less caster you're axle will actually have so that built in 6 degree caster may actually only be giving you 3 or 4 degrees if your chassis has much rake.

Some good points. Our car actually has a very subtle reverse rake. I'm thinking that 4* shims should get me where I want to be.

 

[383man]

Most drag ony cars put as much positive caster in them as they can. It gives the car much better stability and handling on the track. Ron