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Rack position
gaz05 - 11/10/13 at 01:23 PM

Spent the last two hours reading all the search results and it's still as clear as mud

I'm building a Haynes and am assembling the front sus and steering. Sierra uprights,Escort MK11 rack,Protech shocks and everything to book.

First thing I've noticed is quite a bit of bump steer. I've got the bottom bone horizontal which I think is about the position it will be when on the ground. With a 12" rule clamped to the disc, when I jack it up about 50mm the rule moves out of straight about 20mm. I'm guessing this is too much and given that the rack is on it's highest position on the bracket it looks like I'm going to have to rip it out and fab up a new bracket.

My intention is to make the rack sit about 15mm higher and be adjustable fore and aft so I can experiment with a bit ackerman later on when the cars on the road. The rack already sits about 40mm behind the centre line of the TREs so will probably make that the centre point of the adjustment.

You can see the rack isn't in the best position. I know many variables come into play with suspension set ups. Is my plan a viable option?



Daddylonglegs - 11/10/13 at 01:36 PM

Not much help with your question I'm afraid, but all I can say is that the ride is going to be 'interesting' without springs!

But I had a nightmare trying to get rid of the bump-steer on my Locost. I've got it to a minimum but it's still got some.

[Edited on 11/10/13 by Daddylonglegs]


britishtrident - 11/10/13 at 03:26 PM

There is another option fit rose joints to the outer track rod ends which will allow yo to adjust the vertical height of the outer.

Looking at your picture I would also think you need longer track rod extension before IVA.


mark chandler - 11/10/13 at 04:19 PM

Pull back the gaiter on the rack, when you view from the front you should be able to draw a straight line through the centre of the knuckle on the rack and both bone pivot points, this sets your height, extend with something temporary to determine the best position then build the final solution in the optimum place.


gaz05 - 11/10/13 at 05:53 PM

quote:
Originally posted by britishtrident
There is another option fit rose joints to the outer track rod ends which will allow yo to adjust the vertical height of the outer.

Looking at your picture I would also think you need longer track rod extension before IVA.


They have 20mm entered each side. Should be enough. They could have been a bit longer though. The other stuff I got from 3GE needed work also.


Dusty - 11/10/13 at 10:30 PM

Can you post a longer range pic to show relative positions of the wishbones. That pic suggests they are close to parallel remembering that mechanically the wishbone is a line between the centre of the ball joint and the inner bush. Rack seems too low but difficult to tell from the pic you have posted.


britishtrident - 12/10/13 at 08:38 AM

Do you have offset mushrooms ?
Setting offset mushrooms with the ball joint hole to the rear will lower the steering arms which has (almost) the same effect as raising the rack.