Sam's build thread

[simon k]

interesting... something else I know nothing about. I've learnt a hell of a lot in the past 12 months since I put it on the road

I see what you mean - there ought to be a way of mounting a sandwich plate on the LCA to mount a link. The position on the LCA would give stiffness adjustment too



If I'd known about mounting the links to the LCA I would have set that up when I converted my Bilsteins, it would have given me another 50mm of spring adjustment instead of cutting the sleeves down

[Sydneykid]

The length and/or angle of the swaybar links makes no real difference to the bar's rate. If we replace the rubber bushes (in the ends of the link) with sphericals then that also doesn't change the rate. But what it does do is take the delay (caused by the rubber compressing) out of the effect of the swaybar. So it feels initially like it has more rate.

The round section of the bar enables it to flex, whereas the blade section (if parallel to the link) doesn't flex. So if we extend the blade section to accommodate, 2 or 3 holes then overall the bar will be stiffer, plus it will get stiffer again when utilising holes further up the arm. That's leverage effect, the arm is shorter hence has less leverage to bend/twist the rest of the bar.

Not sure if you can so this on the Polo, due to clearance issues, but moving the pivot point (of the link) on the lower control arm closer to the wheel increases the anti roll rate. The tyre has less leverage on the swaybar. So if you have a bracket on the lower control arm with multiple holes for the link then you can adjust the anti roll rate by moving the link in or out. Something like a bolt on bracket at the ball joint that extends inboard to the OE link position. Clearance is the trick of course.


Cheers
Gary

[simon k]

Not sure if you can so this on the Polo, due to clearance issues, but moving the pivot point (of the link) on the lower control arm closer to the wheel increases the anti roll rate. The tyre has less leverage on the swaybar. So if you have a bracket on the lower control arm with multiple holes for the link then you can adjust the anti roll rate by moving the link in or out. Something like a bolt on bracket at the ball joint that extends inboard to the OE link position.

that's kinda what I was thinking - using the balljoint bolts as the forward mounting point is a good idea, then another set of holes at the chassis end

if the link needs to mount in front of the LCA like the Golf picture above, could it be as agricultural as a piece of 6mm angle welded to a piece of 6mm plate that sits on top of the LCA?

something like this (use your imagination to make it pretty and lightweight)

[sambb]

Ok. I was thinking of just welding a thick plate along the front face of the control arm and then drilling and tapping it for the links. The control arm is pretty thin steel so no idea if it would warp and not handle the heat, but it'd be nice if it did and probably stiffen the arm up too.
I'm pretty sure the mk4 golf control arms have a different rear LCA bush arrangement, vertically bolted into the subframe. I think mk 1 Audi TT ones though are a similar design to ours with the spigot that goes laterally into the forward facing rear bush, but then that still doesn't necessarily mean they'll fit and they may or may not use the links direct to the control arm. Have a feeling they used the strut mounted drop link too.

[sambb]

still waiting on my bloody super pro FARB bushes 20mm for the stock bar. The stock rubber ones I have in there now are mush.

I've just loaded a new throttle map into the car courtesy of the guy that helped me with the tune. Feels great so far. The last one had linearised the whole throttle map which made the car less light switchy as boost was coming on in the midrange, but also created a bit a dead band in the throttle below 2000rpm. eg hillstarts would need a lot of throttle but then as you got under way you'd have to pull your foot out of it quick smart as it'd sail up onto boost. Where its at now is somewhere in between stock and what I've been running for civilian driving but has kept it linear above 2000rpm to give you a bit more intuitive pedal progression to match the torque delivery. I'm now back to being able to just bump the clutch and take off from the lights in second if its a slight down hill grade, but the car isn't trying to boost every time you come down off the back of a traffic hump and just brush the throttle inadvertently like stock.

[Sydneykid]

From memory (it's been while since I was under a Polo, with lots of other cars since) the lower control arms look like this?




If so I'd be tempted to try bolting on a piece of right angle alloy to the top of the control arm. Using say 3 through bolts, with crush tube inserts in the lower control arm to prevent the arm itself crushing when the bolts are tightened. A centre bolt with one closer to the ball joint and the other closer to the inner pivot. Then say 3 or 4 holes in the bracket, around 5 mm apart, one where the current sway link would effectively be, so you can duplicate the "standard" amount of anti roll when using the OE swaybar.


Cheers
Gary

[sambb]

yep that's exactly what we have. Yeah it is swiss cheese so there are a few holes we can utilise and yes they'll definitely need crush tubes. I'll get under there this weekend and see where things line up. What I'm struggling with is how having droplinks mounted to the control arm (even if the droplinks are mounted further out ie not vertically below the bar ends) can result in higher anti roll than stock. As it is the wheel: droplink movement ratio is around 1:1 isn't it as its attached to the strut? If you have droplinks mounted anywhere in board of the ball joints though, aren't you giving the wheel more leverage to twists the bar more easily which would result in less anti roll ie the bar cant resist a given amount of wheel movement as easily. I know I'm probably wrong but assuming we can only set the droplink pick up on the control arm a certain distance out and cant reach the ball joint area without the drop link being nearly flat, I'm struggling to see how we could duplicate the same anti roll with this system unless we had a stiffer bar. Just struggling to see it any other way and happy to be schooled!

[simon k]

If you have droplinks mounted anywhere in board of the ball joints though, aren't you giving the wheel more leverage to twists the bar more easily which would result in less anti roll ie the bar cant resist a given amount of wheel movement as easily.

correct, the wheel has more leverage against the bar, so the bar twists more for the same amount of wheel movement - a little bit of twist in the bar is easy, it's a lot of twist in the bar is hard.

unless I'm thinking about it the wrong way up too, but from the opposite direction

[Sydneykid]

I think we might be confusing "movement" and "leverage". Move the link closer to the wheel and the link is going to move more in relation to how much the wheel moves, hence the bar is going to have to twist more. Plus the wheel has less leverage when the link is located closer to the wheel, so the resistance of the bar (wheel's movement) is greater. Like a wheel barrow, the longer the handle the lighter that load feels.

In a MacStrut the centre of the strut usually moves around 90% of the wheel movement, which means 10% more leverage and 10% more movement. So if the swaybar is, say, rated at 100 then it's effect (on the tyre) is 100 x 0.9 x 0.9 = 81. Once more from memory, I think the swaybar link connects to the inside of the strut, so depending on the arc that the lower control arm follows the strut movement it may well be less than 81.

It's easy to measure, just jack the car up and measure how much the swaybar end moves in comparison to how much the wheel moves. It should be something like 50 mm at the wheel = 45 mm at the swaybar.

You may well find that you can't locate the bracket outboard enough to get as much as you currently have can with the strut drop link. If that happens you can use the heavier swaybar knowing that you can soften it by moving the link inboard some more.

As you mentioned in a previous post, getting the swaybar link off the strut is very worthwhile just on its own as it removes the swaybar movement when the strut rotates (steering). The adjustability is a bonus.


Cheers
Gary

[sambb]

Ok gotcha thanks Gary. Think I'll be hanging onto the stiffer bar in case the car cries out for it and if it goes back in i'll look into what can be done differently with drop links. I think the Mt Panorama hillclimbs in march will be the perfect test of where I'm at with front end roll stiffness and i'll know which way I want to go after that.