OK - got to get the FU tubes fitted, but want to make sure they are in the right place for castor angles.

I am using something close to a book chassis, but have MK Indy wishbones and Sierra uprights. I have the relevant dimensions for distances apart for upper and lower bones, and the height between them, but need to know how much further back the top bone front mount should be than the bottom bone front mount. Alternatively, the relative lateral distance between the outer ends of the bones to give the correct castor angle. Some have suggested that to get the required self centering the Indy bones may not be ideally positioned on the MK chassis so any thoughts on this would be appreciated.

May as well try to get it right first time

[Edited on 31/12/05 by andyps]

You really need to make a simple jig to fit them correctly. A quick search through the archives should show plenty of examples.

Yep - leave the FUs out (or just tack them in) until you're ready to fit the suspension brackets.

I fitted mine to the book, and had to shift them back a fair bit when it came to final fit-up.

David

Likewise, I have left mine off, I am building wishbones first, then will be fitting all the suspension components with a jig, and putting FU tubes on where they are needed to support the top rear wishbone bracket.

Ultimately it has to be wherever it has to be to make the top wishbone bushes line up parallel to the centre line of the car, and with build tolerances the easiest way to find out exactly where that is, is to place your brackets and see where they land.

Making a jig is the best way for placing them.

Increasing castor gives other challenges. Don’t make S & T to permanent as you may need to drag them back to support the tops of Fu which sit inboard abit.

pic2

I am wanting to get the suspension mounts fitted, and intend to make a jig of some sort for alignment, but at the moment I am not sure what position the top bone should be relative to teh bottom to ensure the correct castor with MK Indy bones and Sierra uprights. Once I know this I will put the FU tubes in the right place for the mounts.

Don't forget to bear in mind where ther steering column is going to go

Mick

Doubt the steering column would go through any of that lot.. track rods?

Doubt the steering column would go through any of that lot.. track rods?

On a book chassis one way to get nearer to the optimum position of the wishbone brackets is by insetting the lower end of the FU tubes, if you decide to go this route it is best to consider where the steering column, (the lower part where it attaches to the rack), is going to fit.

Best not to ask how I know this

Mick

Ah, heh. I seem to remember something about the bottom of FU making it difficult to bolt up the lower wishbone rear mounting..

I have a +4" chassis so maybe I can jammily move the bottom of the tube in and be OK anyway. hopefuly I'm not too far from that point (although I was thinking the same thing in the summer)

Yep been down this route and had to rip it all out again. By inseting Fu it all fits a treat untill you look at the steering rack

See Link

What I really want to know is the dimensions for A and B when using MK Indy wishbones with Sierra uprights. Can anyone measure this for me?
Rescued attachment front_susp_jig2.jpg

i fitted the lower bones first, jigged them as per the piccy, then fitted the upper wishbones and fu tubes to suit the castor/location as required.

http://www.locostbuilders.co.uk/upload/IMG_0797.jpg

Ned.

Andy,

I've done a similar setup to you.

I stand to be corrected on this but:

That standard book wishbones/uprights need a castor of 22mm.
With Sierra uprights I seem to remember Mark Allanson had calculated it to be 25mm.

Your MK wishbones are the similar to the book but longer. 2" in the bottom wishbone (approx!) and less than that in the top.
Even if the bush tube spacing is different it doesn't matter as long as your castor is correct.

Just build a jig as per the pics in my archive :
http://www.locostbuilders.co.uk/photos.php?action=gal&user=James&folder=Bracket%20Jig

With the wishbones fitted you can check your castor setting is correct and then align FU1/2 into the right place.

Easy Peasy!

Hope that helps,
James

[Edited on 10/1/06 by James]