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front suspension - last time!
robby - 21/9/03 at 09:33 PM

right! been thru all the threads on this, and i'm none the wiser! firstly, i've got the back irs done, to standard sierra d.shaft lengths - should i make the front w. bones longer to get the same track width? secondly, has anyone already done this, to save me working it out?! if i do do it myself, is the castor all i need to be careful with? (all being square & parallel etc.) thanks!


JoelP - 21/9/03 at 09:42 PM

are you using a standard chassis? if so then they do need to be wider.

as a word of warning i tried measuring mine and making them right, got it wrong, track is about half an inch wider at the front. and you have to make sure that the lower and upper ball joint on each side have enough freedom to let the two arms move thru the necessary range of motion, both up and down. at first mine wouldn't droop at all because the cortina bottom ball joint was pointing in too far. changed it and now its too far the other way. live and learn i guess.

the only important thing as well as castor is the bumpsteer, though that is actually to do with the steering rack. though i'd mention it in case...

my chassis is no standard so i dunno how big you want the lower ones to be. you could measure and just do your best if no one knows the right dimensions.

anyway good luck. joel

[Edited on 21/9/03 by JoelP]


Mark Allanson - 22/9/03 at 06:53 AM

Why would you need the track to be the same front and rear? As far as I know its only railway engines that HAVE to have identical tracks widths


robby - 22/9/03 at 07:56 AM

thanks for the quick reply's! about the track width's, thought i read someone say it might make the car oversteer (even more!) someone else disagreed, thats the problem i'm having - everything's been talked about before, but with no definite answer's. just wanted to know about someone who had the same problem, sorted it, and have ended up with a car that passed the test, and goes round corners!


kiwirex - 23/9/03 at 08:14 AM

I don't think it makes a huge difference.

In one of Carroll Smith's books (tune to win, I think) he talked about how there was a fashion in the late 70's (Ralt 74, mainly, I think) to have the front track narrower than the back. He thought that you were better to have them the same.

But I imagine it's not going to make a huge difference to the handling.

- Greg H


Dunc - 23/9/03 at 09:08 AM

What are you using for the front hubs and rack, sierra bits or 'da book' bits?


Rob Lane - 23/9/03 at 09:12 AM

My car is a 'Book' car with equal track.

We did some comparisons of cars when I was sprinting and tried each others cars.

As far as driving would tell, the narrow equal track was only just behind the wide track, narrow front, for rear end breakaway oversteer.
The general concesus was, that it was marginal.


robby - 23/9/03 at 10:08 AM

spoke to a local sprinter last night, and he said wider front is best! decided to make them equal, ie extend front 'bones to get it out to sierra rear's width. just done the drawings and made up a scale cardboard model, worked out the roll centres etc, and it's no looking too bad. to improve it would mean changes to mounts on chassis, where theywould be weaker and ugly, for very little gain, as i'm building for the road, not looking for fractions of a second on the track. off to make them now, if they work out i'll let you's know! if they don't...