Back section went a lot smoother, no misalignment after i learnt my lesson on the front bit .


 
It really does make a big difference to the sound of the panel, its more a "thunk" when you tap it with your finger vs a real tinny/drumming noise on the quarter panels where there is no product yet.

I've decided I'll stick with the normal stock hubs for now and upgrade in future if I want to. So I'll drop them down to the powder coater next week to get a freshen up, then it's just bearings, rotors, seals and studs to get and the front suspension will be completely together. 

Well at least you won't hear the hail hitting the roof. Sorry, hope that never happens.

PartTimeMK2
OH instant center, anti squat, axle tramp and traction. 

For leaf springs its real easy, draw a line from the tire contact patch through the front spring bolt. Then find your cars centerline of gravity by weighing it and where those lines meet is your IC.

Problem with leafs is that line moves all the time, because the angle of the front half of the spring changes (from saddle to front bush) under load, turning and braking - that's why drag cars will put on caltracs to lock the IC by limiting the movement/angle of the front section of the leaf, they can then change the IC by lengthening or shortening the caltrac (to an extent) or changing tire/wheel size/tyre pressure.  

Yes Mark, I see your all over it. It was not really all that relevant for me cause I was going 4 link with watts, but doing the calcs was interesting. As you say, change certain variables and see how the IC location changes. My cousin was a drag racer and built a few ground up chassis. They have some interesting work arounds for the leaf spring issue.
I used to naively think it was all about grunt. But its how you get that grunt to the ground.

Yah with leafs a common thing to do is raise the front shackle mount or even have multiple holes for it so you can adjust as you need to dial it in.

One thing with 4 links - bar angle really matters, you can have two different settings - with different top and lower bar angles and still achieve the same IC, but one setting will tramp and try to pull the front off the ground whilst the other hooks up and gives great traction. 

Here is a good visual of it.

That's brilliant thanks Mark.
When I was fitting the bars up, I was wondering about the adjustment and effects thereof.
Figured I'd cross that bridge when I came to it.
 
There are three holes (vertically aligned) in the front brackets (in the cabin) and I just fitted the top bars into the middle hole. The bottom bars you have no choice with the mounts supplied (see pic).
As for the adjustments on the bar ends at the diff brackets, I left them kind of at half adjustment until I had some more info.
I spoke with MST and they were about as useful as tits on a bull. Same as Burton are as I have found.
 
I understand how to determine the IC location, but the effect of its location will be a mystery until the rubber hits the road?
So feel free to shoot me any other similar technical info on this thanks. It will definitely help when it comes time to diagnose the rear end characteristics.

Ok - the MST/GPR4 kit has a fixed lower bar position yes? In my mind then the lower bar should closely match the standard leaf front section angle, from diff saddle to front leaf mount. 

Looking at your photo that seems to be the case if that's the rear suspension at ride height - I can see the middle of the bar is damn close to the middle of the front leaf mount which is good.


If the kit is set up the way I think it will be, the middle hole on the kit will be the "neutral" bar angle all things being equal and should behave very much like a standard suspension car. 

Move the top bar up and it will push your instant center toward the front of the car and higher, This will give you more anti squat - less weight transfer to the rear - but can cause axle hop and spin.

Move the top bar down and it will pull your instant center toward the axle and down, This will make the car squat - more weight transfer to the rear - better for traction but the car will feel lighter in the front under power.

Now the setup due to fixed lower bar angle can't put the IC below "ground" level - so it's not designed to give a ton of squat - which makes sense due to it being a rally/track car, it really shouldn't be squatting like crazy and upsetting the weight of the car.

Your rose joints and the adjustment there is for setting pinion angle once you are happy with your bar angle - I would try to make it -2 to -4 degrees down relative to the driveshaft at rest, this will allow the pinion to rotate "straight" under load relative to the driveshaft and help with how smooth the car feels and how well it delivers power to the wheels. This can also have a big effect on traction and stop things shuddering and in the worst case binding.

After that write up I had some motivation and time to get back out in the garage, I was going to get the hubs powder coated but then I thought that might mess up all the clearances. So out came the wire wheel and the blasting cabinet to clean them up. Ill mask em up and hit them with the rustoleum (same stuff i used for the diff and type 9) then hit them with a the high temp clear to try and keep the rust off the bare surfaces.
 

 
Also the joining tape arrived for the firewall mat so I can get cracking on that this weekend. Hopefully the diff and front shockers arrive this week too and I'll have plenty to get on with!

They look way gooder than before, something I've got to do to mine plus change bearings out.
if you paint them silver you can pretend they are alloy hubs 😜

Probably should have put this topic on my original thread about this build rather than sabotage this one!
 
Fully get the rationale there Mark for the top bar angle variations. Probably good the bottom bar position is fixed, as it takes a variable out of the equation.
 
I have the engine down 3 deg which is what I have done on previous builds.
 
And on these builds I have just tried to ensure the angle of the driveshaft is a few degrees different to the gearbox and pinion, so the uni's do not run in a straight line. 
 

PartTimeMK2
Ok - the MST/GPR4 kit has a fixed lower bar position yes? In my mind then the lower bar should closely match the standard leaf front section angle, from diff saddle to front leaf mount. 

Yes it does, which I had not paid much attention to, so good spot thanks.

MarkA
Probably should have put this topic on my original thread about this build rather than sabotage this one!
 

All good! I love talking about this stuff so no worries