I was just looking through some previous topics about front suspension and I noticed one post saying that the front A-arm pickup points on the chasis must be parallel to the center line of the chasis, Is this true, or is it misguideing?
This will be the next area of my build I will be concentraiting on just trying to do some homework on the subject, you know what they say ask twice weld once

Mike

if they arent parallel, they will move forward and back in bump and droop. Not the end of the world, just make sure you have taken it into account. With bushes the eyes must always be in line too.

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Originally posted by JoelP
With bushes the eyes must always be in line too.

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And if your using book bones, move the top ones back a bit to correct caster, (IMHO)

Guess who didn't, and has got to remake his top bones. Doh.

Paul G

It's also been mentioned that i should make the front track width of the car a tad narrower that the back track width.
Is there a reason for this too?

Mike

ive not heard it recommended myself, and can think of no reason why it should be narrower at the front. It would be interesting to hear the reason why people have recommended this.

I personally wouldnt be concerned about the minimal change in castor or camber caused by either antidive or unparallel bones. My next car will have an antiroll bar and stiff springs, so it wont matter much anyway. My rosejoints also wont be in line or parallel!

quote:

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Originally posted by quattromike
It's also been mentioned that i should make the front track width of the car a tad narrower that the back track width.
Is there a reason for this too?

Mike

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Having a narrower front track promotes better turn-in - over do it and that translates to oversteer.
If you're stuck with a narrower front track, a front anti roll bar or stiffer front springs can help.
Don't read that as a cure, it's just the effect; you really don't want to stiffen the front springs any more than is necessary to hold the car up.

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Originally posted by Rorty
Having a narrower front track promotes better turn-in

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Ooo err,

Either, I've had a serious measuring accident,

or, I've misunderstood this thread completely. (more than likely)

By track we mean tyre centre to tyre centre, left side to right side; yes?

I have a book chassis, dimension wise, with book wish bones.
Admittedly it's 100mm wider, but that's all the way down, i.e. back +100 and nose cone +100

The back wheels are (centre to centre) 1455mm.

The fronts, 1375mm.

So an 80mm difference;
so IF I haven't cocked up, all book chassis with book bones should be narrower at the front.


Yes / No

Paul G

quote:

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Originally posted by 907
Ooo err,

Either, I've had a serious measuring accident,

or, I've misunderstood this thread completely. (more than likely)

By track we mean tyre centre to tyre centre, left side to right side; yes?

I have a book chassis, dimension wise, with book wish bones.
Admittedly it's 100mm wider, but that's all the way down, i.e. back +100 and nose cone +100

The back wheels are (centre to centre) 1455mm.

The fronts, 1375mm.

So an 80mm difference;
so IF I haven't cocked up, all book chassis with book bones should be narrower at the front.


Yes / No

Paul G

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Sorry my rear hub face to hub face is actually 1600mm dunno where i got the other size from.
Paul the book is made with the escort width in mind but i think your useing the sierra width are you, because 1455mm sounds like sierra.

That's a relief

Yup, Sierra dif & drive shafts, not cut down.

So is a true book Locost with Escort back axle wider at the back, if so, by how much?

Paul G

Escort axle is 4" narrower than a sierra rear end. More and more poeple that want a live axle set up are using Cortina/Capri axles or Sierra stuff with a de-dion tube as these are all 4" wider than the escort and in my oppinion looks much better with the fatter rear arches.

Capri axles are a mid point between Escort and Cortina and are a good bet for a 'book' Locost as the wheels fill the arches better. Use the Cortina one if you want wide arches. I personally prefer the narrower arches on a book chassis.
BTW I agree with Rorty, don't put stiff springs AND anti roll bar unless going for serious track use. It will bounce about like a good 'un on the road. An anti roll bar allows the use of softer springs, compensating for the additional roll generated, for a smooth ride.

Marcus

This may be a bit off post but has anyone used anti-dive on their front A-arms, If so how much off the horizontal would you say would be best?

Mike

if you work out your 3d centre of mass, and aim the pivots up towards it, you *should* get no dive. Its entirely possible though ive not quite hammered out the details in my head though, so if anyone thinks different, please say!

As a small aside, in my locost on track last weekend, i didnt notice any dive with a normal setup. Obviously it did to a certain extent, but it wasnt noticable. Also, antidive geometry causes the pivots to get a little stiffer when braking than normal, so bumps will hurt it more when braking