Camber adjustment to Camber/Castor Adjustment

[Makaveli_se7en]

The WRC fiesta goes the opposite way to the Polo:

I was discussing this recently at work, I have no idea why other than to fit in a long travel strut withiin the package space.

 

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I would lay bets it is for the allowance of a bigger longer strut to improve the suspension travel and also for less overall strut speed to bump ratio to help the suspension oil to stay more consistent in temperature and there for improved damping, remember caster is the angle from the lower arm ball joint to the top of the strut pivot not the strut angle.

 

[campbellju]

Interesting question Andy, I've not really looked into it much before for similar sentiments to Phil.

IIRC adding castor to the rear end on the Gtir will mainly add bump steer.

There might be a bit of anti/pro squat dive/lift depending on how you fettled it but this would be more minor. (If you wanted to bring in some "anti" geometry settings then your are better off fiddling with your subframe bushes rather than your strut/hub.)

More dynamic bumpsteer might be desirable to someone like Evan who was running a lot of rear toe out at the rear to get has back end round the hairpins but for street use I wouldn't have liked to use Ev's toe settings. So for our cars I've never given it too much thought as I can tell you how much static toe I like at the rear (not a lot) but not dynamic toe. Fiddling with one might completely mess up the other.

So why do other manufacturers do it? I can't find a MK6 but look at this mk5 below and you can see why you need the angle on your strut. It's an evolution of a tailing arm. (As is my M3)

http://www.vwvortex.com/artman2/uploads/1/008__scaled_600.jpg

The orientation of the strut compensates for the track control arm.

Looking at the standard fiesta :

http://static2.paultan.org/fiesta-suspension.jpg

This is a completely different strategy to the VW being torsion beam rather than independent.

Both cars go round corners, as can ours.

So why is the focus and fiesta WRC different? It's getting late but I believe the Focus is independent like your golf and looks like is also has an evolution of a trailing arm suspension. They call it control blade to make it sound cool/new.

So I assume the rear castor on the WRC isn't what you imagine at all and is more to do with the mounting points on the original cars that the WRC engineers started to scratch their heads with?

There might be something in the long travel strut but I reckon this is a red herring. Being honest on the WRC cars I can only guess as I don't know all the rules or their design objectives.

 

[fubar andy]

Interesting responses.

It was more of a curiousness than anything else, whether it would make any difference to the suspension characteristics even though there is no turning of the wheels.

As I'm looking to play with the suspension settings while the engine and mapping is been completed and I'm giving myself some ideas to implement for when I head back on to track.

I've also been looking to add more caster to the suspension struts to aid more turn in as Jim tried with adding plates and adding more aggressive camber angles to try and combat the remaining understeer that I seem to still have.

 

[campbellju]

Fiddling with rear caster I would avoid.

Stu and I looked at camber compensation first, my M3 has a clever setup that is a variation on a macpherson strut. After measuring the camber curve on the GtiR we felt that more caster would give us the results we wanted.

I would say your front caster with the mod is sufficient. If you add even more caster like I did then it will improve your second gear corners but less so your 3rd gear and no difference to your 4th. At high speeds you are turning your wheel very little so caster won't help camber compensation.

Not over lowering the car for the road or not allowing the suspension to travel too much for the track would be better strategies.

I then went fiddling with spring rates, track and messing around with KPI (king pin inclination). Again KPI is less relevant for a track car so you will get less benefit from the way I added more castor.

What Stu and I wanted to do next was a bigger front ARB that was adjustable from stock to stiff. The rear ARB is more straightforward but the front wasn't going to get done with the Nissan parts bin. This would give the ability to fettle stiffness without having to re-align everything again as with changing springs.

In terms of simple things for your car, IIRC you can run more static front camber on your car. I've used -2.5deg on road/track with road tyres in the wet. This level worked on track but not as well on the road so I settled around -2deg as a compromise for dry/wet/road/track. For your fast lap you are looking at a smooth dry track with slicks, -2.5deg can be your starting point.

An extra 1mm on your coarse camber mod is what you need to be thinking.

 

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spring rates are another thing that need to be mentioned, you need to run very very stiff springs if you are using slicks, where as if the car is road biased with road tyres you need soft springs and suspension travel...alot of aftermarket shocks have to little suspension travel.

 

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mark turbo is another one that can chip in with this

 

[fubar andy]

I would say your front caster with the mod is sufficient. If you add even more caster like I did then it will improve your second gear corners but less so your 3rd gear and no difference to your 4th.

As the car will be taken off the road in a year or so, purely to be used on track, would it be a consideration to add more castor?

What Stu and I wanted to do next was a bigger front ARB that was adjustable from stock to stiff. The rear ARB is more straightforward but the front wasn't going to get done with the Nissan parts bin. This would give the ability to fettle stiffness without having to re-align everything again as with changing springs.

I've always been a little put off with messing with the front ARB; as my thoughts were if I added a stiffer rear ARB to reduce understeer, would it then defeat the object to add a thicker front ARB as it would cancel out the rear ARB?

In terms of simple things for your car, IIRC you can run more static front camber on your car. I've used -2.5deg on road/track with road tyres in the wet. This level worked on track but not as well on the road so I settled around -2deg as a compromise for dry/wet/road/track. For your fast lap you are looking at a smooth dry track with slicks, -2.5deg can be your starting point.

I am keen to add more camber to the front and rear wheels, also look at playing with the toe, to see if I can get the car to turn in better?

spring rates are another thing that need to be mentioned, you need to run very very stiff springs if you are using slicks

My current spring rates are 10kg/mm front and 7kg/mm rear

 

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http://www.facebook.com/l.php?u=htt...-in-italys-most-insane-rally-cars&h=GAQEz5RlZ


now those cars handle,

 

[campbellju]

Playing with your camber and toe seems like a good place to start. forget messing with caster for a track like Oulton. ARB's are are not off the shelf so need development. Check your rear ride height, could add 5mm. Your relative spring rates will bias a little understeer still. I run 5/4 which is fairly neutral. Ev was 8/7 that he got to work in the end through chassis/damper tuning. Depending on whether you are happy with yout front rate you could change the back to compensate or vice versa. If you facny Andy we could do it for a project on here?