Suspension setup..

[djb222]

Trying to set up my suspension, and I'm in danger of losing my hair!!

I've set up the Camber fine, front and rear toe in is a different matter. Adjusting for the toe in is fairly straight forward but it's setting up the datum points that is the problem.

I'm using the string box method. setting up the string 150mm outside the centre of each wheel, ok good, but then the distance between the strings is not the same between the front and rear of the car. i.e. the strings are converging slightly towards the front of the car meaning any measurement or adjustment is useless.

Any suggestions as to what I'm doing wrong, or am I missing something obvious..

David

[BogBeast]

Its a long time since I tried the string box method and did so when I first built. I remember it being an exercise in futility and time wasting. I would have tried something like http://www.trackace.co.uk/ instead, especially considering how many bushes I have done over the years

[Corsair613]

Just get it as close as you can, but don't make yourself crazy with the string box method. Once the car is driving, take it to decent alignment shop, give them your desired specs, and let the laser do its magic.

[Equus]

djb222 said:

I'm using the string box method. setting up the string 150mm outside the centre of each wheel, ok good, but then the distance between the strings is not the same between the front and rear of the car. i.e. the strings are converging slightly towards the front of the car meaning any measurement or adjustment is useless.

It sounds like the thing that's wrong is that your car has differing track front and rear! The 150mm. dimension will need to be adjusted at one end of the car, to compensate (ie. to make the strings parallel).

[BogBeast]

Corsair613 said:

Just get it as close as you can, but don't make yourself crazy with the string box method. Once the car is driving, take it to decent alignment shop, give them your desired specs, and let the laser do its magic.

+1

I went to Dave at http://trackdevelopments.com/services. It was painful to see how far off my string box 'measurements' were..

Maybe a bit off your patch but Dave is very knowledgeable and very a resonable price IIRC

[djb222]

Thanks,

i'll try to get it as close as possible, then get it aligned professionally.

I can see that using the string box method is open to measuring errors including accurately finding the centre line of the car. I'll give it another go this week.

[drdrdrt]

You may want to think about checking this site:
https://www.tenhulzenautomotive.com/

The products were designed for an Ultima......... and can be used on just about any other car.

[Steve_D]

djb222 said:

......I'm using the string box method. setting up the string 150mm outside the centre of each wheel, ok good, but then the distance between the strings is not the same between the front and rear of the car. i.e. the strings are converging slightly towards the front of the car meaning any measurement or adjustment is useless.

Any suggestions as to what I'm doing wrong, or am I missing something obvious..

David

OK so it converges. Widen the strings at the front until they are exactly the same. Then measure again to each hub to ensure they are the same distance each side. The distances are not important as long as the strings are the same distance apart and equal distance each side of the car. Lets say they end up 150 from the rear hub and 159 from the front hub. This is fine provided the strings are parallel. once you have it set the strings ar parallel and the car is centred between them.
Now you have the strings set you can measure and set the front and rear toe.

Steve

[djb222]

After much faffing with what I have in the garage, I measured from the centre line of the car to set the strings parallel, and they are spot on. The distance from the centre of the rear wheels to the string are equal, yet at the front they are 5mm out, rechecked the string distance from centreline and it's accurate. Steering is centred.........Slowly getting there but the measurement at the front is a little perplexing.....

[Steve_D]

Why are you trying to find the centre of the car?
All you are interested in is the distance between the strings and the distance from the hub centres to the strings.

Steve

[djb222]

With the strings parallel (measuring from the centre of the chassis) then the distance from the hub centres to the string should be set front and rear. It's spot on at the rear, but I'm finding a 5mm difference at the front.

This is the method in the manual.

Just had some metal square section tube delivered, which will make life easier.

David

[Steve_D]

What I am saying is ignore the chassis just measure from string to string across the front of the car then make sure it is the same at the back. You now have your 'box' parallel.
Then measure from string to hub both sides at the back. If they are not the same you will need to move the box (or the car) over. Do the same at the front. It will take a while to do as you have to make sure your box is still parallel.

Steve

[V8Dom]

strange my reply has been deleted

to string a car you need to know the centre line of the car. otherwise the string box isnt square to the car/chassis.

front clip off rear clip off is easiest

car must be at right hight as if lowered it alter geo

mark centre line on floor . find centre car, cotton and weight to floor to mark.. do that front and back.

set up string and box.. then set up the wheels to the string .

once complete. you need to take the wheels off and bob weight with cotton each hub and measure diaganally to make sure one wheel isnt further forward than the other side..it should be square from side to side as well as front to back

alternatively Charles Dunn has made a setup guages just for setting ultimas from scratch. he can set up the complete suspension in half the time.

[Steve_D]

I don't seem to have made my point clearly enough.
Here is a diagram.


If we assume that the wishbones are manufactured the same length and likewise the bearing carriers and hubs then measuring from the box to the hubs will position the car centrally. The chassis need not be part of the equation.

All that is required at this stage is to get the toe set. Anything more will be covered when you take the car for laser alignment.

Steve

[Storer]

Steve_D said:

I don't seem to have made my point clearly enough.
Here is a diagram.


If we assume that the wishbones are manufactured the same length and likewise the bearing carriers and hubs then measuring from the box to the hubs will position the car centrally. The chassis need not be part of the equation.

All that is required at this stage is to get the toe set. Anything more will be covered when you take the car for laser alignment.

Steve

As usual Steve is right.

I use alloy box and string with split pins to hold the string through holes in the box. Support box on axle stands front and rear. The box can be out of square as long as the distance from string to axle centre each side is the same.

The front and rear axle don't measure the same string to axle centre. But string must be the same distance each side for each axle before you start any other measurements.

Paul

[V8Dom]

i understand but

all bushed cars they have a rose joint on the top of the arms so arm length is adjustable... you would have to do camber first.. are the arms equal side to side i thought n/s/f was 2mm out of square from past discussions years ago? .

i couldnt use Steves method on my car...mine is fully rose jointed inside and out and setting from scratch has to be centre lined. the rose joint arms are slightly different side to side and arm completely adjustable inwards to outwards but also adjustment to move wheel forward and back too hence triangulation measurements needed as well as centre line reference.