Where’s my caster?

[frayz]

Where’s my caster?

Okay, so I’m wondering if anyone has any thoughts on this. Basically my car has a lot less caster than I expect it should have. I’m lead to believe they should run around 3.10 degrees of static caster from the factory, of which I’ve seen plenty of cars running.

My car currently

- Clio 2005 FF with both cup packs.
- Correct Cup lower arms
- Powerflex black lower arm bushes
- Roll centre correction hubs
- AST 5100 dampers.
- PMS topmounts.

Upon having the geo done you can see I’m sitting around 2.3 area which is pretty low to my mind.

When I fitted the arms I even pushed (for what it’s worth) the uniball carriers as far forward as possible before tightening.

Puzzled by this is started to look back through the cars history, and found the caster angle has always been lower than expected, so clearly nothing I’ve done since has altered this.
As said, I’ve seen standard cars with more caster than this. If we are splitting hairs, in theory I’ve got a slightly lower rake angle (front to rear) over the whole car so should have marginally increased the caster that way anyway.

You can see from the images below the offset drilling’s in the arms indicating these are indeed genuine Cup arms. The Powerflex bushes are up against the machined stop indicating the arms are in their correct location. I don’t wish to run the AST topmounts as I prefer the design of the PMS variants with the associated brace and have seen the turrets fail with the ASTs.

So failing to re-drill my lower arms to offset the lower uniball carrier even further.
Any suggestions welcome as to why I’m seeing such a low caster angle?

Anyone seen this before or have any ideas?

Thanks. 🙂👍🏼

This is my current geometry.

This was back when the car was stock.

 

[cp1991]

following as my 172 cup is similar at 2˚41 and 2˚39 but my ph1 was at 3˚29 and 3˚16

 

[Usr117063]

Are they configuring the machine to read the actual caster? Because when I got mine done with corner weighting it was 4.6 ish, then some time after a quick toe setting at kwik fit with tyres was 3.2

 

[frayz]

Are they configuring the machine to read the actual caster? Because when I got mine done with corner weighting it was 4.6 ish, then some time after a quick toe setting at kwik fit with tyres was 3.2

Not sure really mate.

You’re always limited with these places as to how well they know how to use the alignment equipment they have or if they just make it all “green” on screen and give it back to you.

I used to have a fantastic alignment place local but not anymore.

 

[Eddie555]

My car is always Aligned at the same place and they really really know what they are doing.. They align race cars all the time.. My caster before Roll centre correction kit was roughly 3ish. Since fitting the RC kit i lost about 1 degree.. Nothing else was changed on my car..

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[frayz]

Interesting as to why you lost caster post fitting the roll centre hubs Eddie.
Doesn’t make sense to me, but I’m obviously missing something. Lol

 

[Eddie555]

Interesting as to why you lost caster post fitting the roll centre hubs Eddie.
Doesn’t make sense to me, but I’m obviously missing something. Lol

I'm not gonna lie.. I aint got a scooby either.. my guess is that its the direction and height that the wishbones sit at.. But i will add the steering feels so so much more precise and direct since the RC kit and i probably dont know what im supposed to be loosing out on by the loss of caster.. [emoji2369]

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[frayz]

I'm not gonna lie.. I aint got a scooby either.. my guess is that its the direction and height that the wishbones sit at..

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So because they’re lower they effectively make the strut stand more upright?

I must admit I’m seriously tempted to re drill a set of lower arms and move the balljoints further forward.

 

[Eddie555]

If it really bothers you then you could get the caster adjustable bottom wishbone bushes.. My real test will be in my times on track and how it feels on the same tracks in similar conditions... But due to this Covid i haven't really had a chance to test this year..

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[frayz]

If it really bothers you then you could get the caster adjustable bottom wishbone bushes.. My real test will be in my times on track and how it feels on the same tracks in similar conditions... But due to this Covid i haven't really had a chance to test this year..

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Not seen these.
I assume you shun them back and forth or is the rear bush eccentric and allows the ball to be moved forward?
I’ll have a butchers. Thanks.

 

[Eddie555]

IIRC.. Theyre from PMS.. theyll be spherical bearings and several shims to fit either side to adjust..

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[Usr117063]

Dude wheres my caster?!

Red arrow shows new location for lower joint, thats what could of happened. Or that Im wrong, or the alignment people didnt configure for caster, or it wasnt taken into consideration in the design.

 

[frayz]

Dude wheres my caster?!

Red arrow shows new location for lower joint, thats what could of happened. Or that Im wrong, or the alignment people didnt configure for caster, or it wasnt taken into consideration in the design.

View attachment 1467202

Thanks Zach, as I suspected.
But that doesn’t explain the zero change in caster post RCC hubs.
It’s always had less caster than desired.
So whilst your drawing makes sence in theory. It doesn’t appear to be the issue I may be suffering from.

If indeed I have an issue at all 🤷🏽‍♂️

 

[Usr117063]

I reckon its the alignment machine then mate. I doubt it would on Eddies take away 1 deg just lowering the joint slightly. Admittedly I always wondered how you measure caster, until recently phil on driftworks did it on his porsche. He turned his wheels lock to lock on the alignment machine which measured the camber change, I think thats how it works.

 

[frayz]

I reckon its the alignment machine then mate. I doubt it would on Eddies take away 1 deg just lowering the joint slightly. Admittedly I always wondered how you measure caster, until recently phil on driftworks did it on his porsche. He turned his wheels lock to lock on the alignment machine which measured the camber change, I think thats how it works.

Yes it does. Just measures the change in dynamic camber and calculated the static caster.
The plates on the wheels have circles on them and the cameras measure the ovality of the circles as the wheels go through their range of motion.

 

[Usr117063]

But do you know for sure they did that?

 

[Eddie555]

But do you know for sure they did that?

I know 100% mine were done correctly and i know 100% i lost 1 degree and i know 100% nothing else was done apart from RC kit..

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[frayz]

But do you know for sure they did that?

Yes i watched.

 

[Usr117063]

Well just put it down to renault then. If you both have the same kit then I dont know. 60v54mm hubs, wishobones different or subframes different (theyll all the same but they're not, I dont know what to believe)

 

[Usr117063]

What were you using before asts? bilsteins?

 

[Eddie555]

My car..

AST 5100 90kg springs all round
54mm hubs
Black series bushes
172 cup wishbones
Pms Strengthening plates
Northloopcup RC
Ride height set at 30cm wheel centre to wheel arches front and rear..

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[Usr117063]

Looks good! I like the added mushrooms 195 or 205s?

 

[Eddie555]

Looks good! I like the added mushrooms 195 or 205s?

195 R888rs

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[Usr117063]

This is why i want to fit the Laguna hubs with adjustable caster so I dont have this problem. I have the hubs.. But getting the asts welded, not keen.

 

[frayz]

What were you using before asts? bilsteins?

Cup dampers and Eibachs

 

[Usr117063]

Then there will be 3 ways to adjust caster, top mounts, wishbones and lower joints.

 

[scullyg40]

This is why i want to fit the Laguna hubs with adjustable caster so I dont have this problem. I have the hubs.. But getting the asts welded, not keen.

Get a set of BC's, and it's a piece of cake. But if you want a lot of caster with the Laguna hubs, you need to modify your wheel hub. 😉

 

[Usr117063]

Cup dampers and Eibachs

I dont know really but if theres caster change over ride height, your lower joint may have not moved, so youve gone lower with the asts and moved the joint back down to where it was with the eibachs. Just a thought.

 

[Usr117063]

@Eddie555 when you lost the caster, were your coilovers at the same ride height as they were before?

 

[Eddie555]

@Eddie555 when you lost the caster, were your coilovers at the same ride height as they were before?

Yep.. Its always been the same.. this was before..

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[Usr117063]

If there is a significant caster change, its just a thought, thats why mine has 4.7, because Im lowered on asts with adjustable top mounts and wishbones increasing camber, there may be an increase with the wishbones.

 

[Usr117063]

Without roll centre correction

 

[Usr117063]

@frayz Whatever H5 or H2 measurements are then for some reason they can come with 2.4 up to 4.2 deg standard? This is new to me. This is for 172 cup

 

[Eddie555]

@frayz Whatever H5 or H2 measurements are then for some reason they can come with 2.4 up to 4.2 deg standard? This is new to me. This is for 172 cup

View attachment 1467302

Where and how do you measure the H2 H5?

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[Usr117063]

Where and how do you measure the H2 H5?

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I have no idea, never heard of them.

Its amazing how in 20 minutes you can go from wanting to develop the car further to not wanting anything to do with it. Why is there a lucky dip of alignments on these cars?

 

[Eddie555]

I have no idea, never heard of them.

Its amazing how in 20 minutes you can go from wanting to develop the car further to not wanting anything to do with it. Why is there a lucky dip of alignments on these cars?

FFS.. Wheres my hammer[emoji1787]

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[Usr117063]

 

[Usr117063]

@frayz Its your subframe

 

[frayz]

I wondered this Zach. I assumed there wouldn’t be much in the way of movement in it.

 

[Steven103]

The tolerance from factory isn't 2.44 to 4.20, it's just +/-0.3 (+/-30' sorry)

The reason they give a range of castor values is so that the tech can take any customer car, with any amount of fuel in the tank or s**t in the boot and get a castor target for whatever that particular car's ride height happens to be.