4 wheel alignment/geometry set up cost?
17 December 2015, 05:58 PM
#62
Scooby Regular
Join Date: Aug 2013
Location: hertfordshire
Posts: 117
Likes: 0
Received 0 Likes
on
0 Posts
17 December 2015, 09:57 PM
#64
Scooby Regular
Join Date: Aug 2013
Location: hertfordshire
Posts: 117
Likes: 0
Received 0 Likes
on
0 Posts
17 December 2015, 10:41 PM
#65
Scooby Regular
iTrader: (3)
Join Date: Jan 2013
Location: Oxford
Posts: 739
Likes: 0
Received 0 Likes
on
0 Posts
Having an alignment will still end up with a poor driving car.
Look at your picture you posted.
Your lower control arms are pointing upwards!
Now look at the diagram below comparing a correctly lowered car and a overly lowered car.
In diagram A the bottom arm is correctly positioned, this gives a high roll centre and it's very close to the cars centre of gravity.
And in diagram B the bottom arm is parallel, this gives it a low roll centre and its further away from the centre of gravity.
Now if you can imagine the cars centre of gravity was a bolt and the roll centre was a spanner, do you think it would be easier to turn the bolt with the higher or lower position??
Obviously It would be easier with the lower roll centre point as you have more leverage.
So what your affectively doing by having a low roll centre is increase the leverage of lateral forces acting on your car during a corner.
If you were to lower your car and keep the same spring rate the car would roll more the lower you go!
So to combat this overly lowered Springs have a much stiffer spring rate to fight against these extra lateral forces,
But there's problems with this, obviously the extra lateral forces are still there but instead of the being disperse through the suspension geometry there now transferred to the tyres so the tyres limit of grip would be reached earlier and at a lower speed. Especially apparent in wet conditions.
Second problem as we all know is that ride quality will also be massively affected.
Not much of a problem on a smooth race track, but on a uk road all this will do is upset and unstable the car,
This will be even more pronounce with a spring that's to low as there will be very little if not no bump travel.
What do you think would be quicker on a British B road a low stiff sprung touring car or a higher soft sprung wrc car??
Now if a cars suspension is lowered correctly maintaining a good degree of roll centre it can be used to tune a cars behaviour.
You can have different roll centres front to rear to fine tune understeer oversteer balance and the overall degree of body roll.
Prodrive did this with the rb set up,
They slightly lowered the front roll centre and kept a fairly high rear whilst keeping a fairly mild Spring rate.
This effectively increases load transfer across the front wheels to improve turn in response and help reduce understeer.
The other over looked part that comes with the bottom arm position is camber curve or camber gain as it's also known.
When your suspension compresses the bottom control arm moves up in a arc.
If the arm is at a downward angle it will push the bottom of the wheel hub outwards increasing in negative camber as you turn helping gain grip.
If the control arm is positioned parallel It's already at its furthest point in the arc, so as the suspension compresses during a turn the bottom of the wheel hub will be pulled inwards gaining positive camber and reducing grip.
This would be even worse if the arm was past parallel and starting to point upwards.
Like I said in a earlier post, yes you can lower a MacPherson strut suspension system but not by much.
Other types of suspension like double wishbones handle lowered ride heights a lot better,
Look at your picture you posted.
Your lower control arms are pointing upwards!
Now look at the diagram below comparing a correctly lowered car and a overly lowered car.
In diagram A the bottom arm is correctly positioned, this gives a high roll centre and it's very close to the cars centre of gravity.
And in diagram B the bottom arm is parallel, this gives it a low roll centre and its further away from the centre of gravity.
Now if you can imagine the cars centre of gravity was a bolt and the roll centre was a spanner, do you think it would be easier to turn the bolt with the higher or lower position??
Obviously It would be easier with the lower roll centre point as you have more leverage.
So what your affectively doing by having a low roll centre is increase the leverage of lateral forces acting on your car during a corner.
If you were to lower your car and keep the same spring rate the car would roll more the lower you go!
So to combat this overly lowered Springs have a much stiffer spring rate to fight against these extra lateral forces,
But there's problems with this, obviously the extra lateral forces are still there but instead of the being disperse through the suspension geometry there now transferred to the tyres so the tyres limit of grip would be reached earlier and at a lower speed. Especially apparent in wet conditions.
Second problem as we all know is that ride quality will also be massively affected.
Not much of a problem on a smooth race track, but on a uk road all this will do is upset and unstable the car,
This will be even more pronounce with a spring that's to low as there will be very little if not no bump travel.
What do you think would be quicker on a British B road a low stiff sprung touring car or a higher soft sprung wrc car??
Now if a cars suspension is lowered correctly maintaining a good degree of roll centre it can be used to tune a cars behaviour.
You can have different roll centres front to rear to fine tune understeer oversteer balance and the overall degree of body roll.
Prodrive did this with the rb set up,
They slightly lowered the front roll centre and kept a fairly high rear whilst keeping a fairly mild Spring rate.
This effectively increases load transfer across the front wheels to improve turn in response and help reduce understeer.
The other over looked part that comes with the bottom arm position is camber curve or camber gain as it's also known.
When your suspension compresses the bottom control arm moves up in a arc.
If the arm is at a downward angle it will push the bottom of the wheel hub outwards increasing in negative camber as you turn helping gain grip.
If the control arm is positioned parallel It's already at its furthest point in the arc, so as the suspension compresses during a turn the bottom of the wheel hub will be pulled inwards gaining positive camber and reducing grip.
This would be even worse if the arm was past parallel and starting to point upwards.
Like I said in a earlier post, yes you can lower a MacPherson strut suspension system but not by much.
Other types of suspension like double wishbones handle lowered ride heights a lot better,
Thread
Thread Starter
Forum
Replies
Last Post
scottydouk
Subaru Parts
4
22 November 2015 06:31 PM