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Re: Front wheel alignment

Twisting radius arms is a bad way.....yes it changes axle but since the spring is still bolted to the nosepiece trying to hold the axle in the same position via the spring and shackles you would be putting a twist on the end of the springs/shackles.

As mentioned above......tapered shim between nosepiece and spring with thick at back and thin at front will INCREASE castor......but really the radius arm chassis joint would need to be lowered (set castor required with shim then see where ends of radius arms naturally end up without any forcing).
A slight twist at each end of the axle in relation to the rest of the axle beam would achieve the result required whilst still leaving the radius arms, beam and spring bolted directly in the same place.

Bill Williams in his book Austin 7 Specials says "The makers specification gives 5 degrees as castor angle and two and a quarter degrees for wheel camber. The king pins are set, on all models at 90 degrees to thw axle beam"

That book deals thoroughly with the whole suspension subject using experience over many years.

Location: NW Devon

Re: Front wheel alignment

Many thanks to everyone for their helpful contributions. As usual, this forum delivers the goods!

Re: Front wheel alignment

One final question: is there an angle on the nose of the chassis so the spring and axle sit at the correct castor angle and are supported by the angled radius arm ends?

Or, do the radius arm end angles gently plush the spring and axle to the correct angle?

Roger

Location: Dorset UK

Re: Front wheel alignment

The answer is yes but it is more a matter of retain than push when all is perfect and correct. However springs may have acquired twist and set and so an element of push involved.

Location: Auckland, NZ

Re: Front wheel alignment

I think that might be two questions, Roger! The answer to the first one is yes, the answer to the second is yes, sometimes not that gently. So in essence I agree with Bob but, as he says, assuming all is perfect and correct

There are pitfalls for the unwary which I address in my post of 16th Oct 2013 in the thread "radius arm interchangeability". There is a bit of a clue in the title of the thread. Sorry, no idea how to do a link.

Regards,
Stuart

Re: Front wheel alignment
Re: Front wheel alignment

One point, or maybe two that everyone should remember is that the light radius arms particularly are extremely flexible and easy bent. The best solution on my opinion is first set the kingpin inclination to the desired angle with no radius arms fitted, pack spring if required to achieve 5 degree or what ever you wish to use. then offer up your radius arms and see if they align with the ball... most won't! Unless you have some seriously damaged arms a tweak here and there will bring the ends to reasonable alignment. On no account should it be necessary to spring the radius arms or to strain the front spring to achieve alignment of the ends with the ball. it may be necessary in some cases to pack the ball on the crossmember and on some specials even relocate the ball height, I can usually avoid this on a well designed car but not always. A final point is the brass cups must be in good condition, they must be a snug fit in the radius arms, and the ball in good shape, otherwise the whole assy will move under braking, ever noticed your front brakes grabbing in reverse, this is probably why!

Location: NZ

Re: Front wheel alignment

A quick search of the Forum under 'Caster' will explain a lot !

Unfortunately no pictures thanks to photo*ucket.

Cheers, Tony.

Location: Melbourne, Victoria, Australia.

Re: Front wheel alignment

Hi Stuart

Wow, now you have done it! A difference with the later radius arms would have occurred to very few. Hundreds of owners of high chassis cars with later axles will now be unsettled! Ian Williams recently established the difference as about 1 deg. I guess the spring assembly will reasonably accommodate this. Many obviously do. Some will consider the castor reduction significant.

As previous a card cut to 95 degrees held against the face of the radius arm nut, should present the other side horizontal to a spirit level. Assumes nut of uniform thickness and not over a spring washer.

Location: Auckland, NZ

Re: Front wheel alignment

My RN saloon has a Girling front axle with Girling rad rods.I did not want to lower the ball joint as this puts more torsion on the front crossmember and puts a larger eccentric load on the weedy centre strut. I bolted the front axle/spring assembly to the chassis with a similar amount of castor angle as my chummy and after cutting the Girling rad arm (just aft of the drop stamping carrying the spigot) vertically from the underside but stopping the cut just at the corner with the top flange I bent the arm up until it was aligned with the ball on the crossmember. This left a triangular gap of about 8 to 10mm at the base.I welded in a triangular piece of similar gauge mild steel as the rad arm.Car steers very nicely. I did this mod 14 years ago and have done x thousand miles in it since.
Dave.

Location: Sheffield