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Geometry checked

Want to know what to brakes/springs to buy?
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Dan
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Geometry checked

Postby Dan » Tue Oct 16, 2007 5:35 pm

So went to Dave McCann Tyres to get my camber etc checked out and as i thought all angles were way out since fitting the coilovers and front strut brace. After an hour of the lads hitting underneath the car with hammers and sdjusting with spanners, all is good. Car feels so much smoother, havent really driven it much but seems like there is a definite improvement. Splash out on 4 new Eagle F1's while i was there. I'll have to test them out later properly!


The lads there know what there doing and are sound to talk to. Only 70 Euro too. Going back to have a chat with them soon about the measurements Tony @WIM recommended for my setup to see if it can be improved some more

Geometry checked and adjusted and 4 tyres fitted and balanced for 600 Euro.

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Noel
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Postby Noel » Tue Oct 16, 2007 6:08 pm

Good Value :wink:

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Dan
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Postby Dan » Tue Oct 16, 2007 9:58 pm

ye cheaper price than eiretyres.com. Heres the before and after stats is anyone is interested. Showed these to Tony@WIM(www.wheels-inmotion.co.uk) just to ask him to check that the lads set things right and OMFG this guy knows a crazy amount about suspension/geometry setups!

Geometry Before and After

Primary angles before:
Front
Caster left: 7º05’
right: 7º22’
Camber left: -1º22’
right:-1º35’
Toe left: 0º04’
right: 0º08’
total 0º12’
Rear
Camber left: 2º09’
right: 2º19’
Toe left: 0º10’
right: 0º13’
total 0º22’
Thrust angle: -0º01’

After
Caster left: 7º29’
right: 7º38’
Camber left: -0º58’
right:-1º02’
Toe left: 0º03’
right: 0º02’
total 0º05’
Rear
Camber left: -1º29’
right: -1º32’
Toe left: 0º02’
right: 0º02’
total 0º04’
Thrust angle: 0º00’

The end positions are typical for the lowered car.... In truth this is not necessarily bad since the dynamic gains are reduced.

Down side is that the castor is very high so the steering may well feel heavy and we could have a conflict with the camber/castor on the corner but without some bench testing actual figures are impossible to predict.

Explanation
On the steer axis during cornering there is a mechanism to maintain as near to 100% tyre-tread contact patch.

This is a changing of values between the camber lean and the extension of the castor angle.

Maths example> For those that like that sort of thing.

Camber Change - If a wheel has positive Castor, then the top of the wheel leans into the corner whichever way it is steered. The change in Camber is approximately:

Camber Change = Castor x steer-angle / 60 (measured in degrees)
Example: Camber Change = 6 degrees
Steer-angle = 10 degrees
Then:- Camber Change = 6 x 10/ 60 = 1.0 degree

The change in camber that results from positive Castor is beneficial to the grip of both front wheels during cornering, providing it isn't excessive. A negative Castor (top of the steer-axis leaning forwards) changes the wheel Camber angles in the 'wrong' direction during cornering, this is not desirable.

Transitions
In a forward position the front cambers will be / \ (looking from the front) if for example this car turns to our left the transition of the camber (accentuated by the castor) will move the camber to \ \.

Curve
The gains left and right are dependant on the (adjustable camber) against the fixed castor.

If the dynamic positions do not correlate left/right then the angular gain generated against one incorrect camber on the corner will roll the weight distribution onto the sidewall and wear the tyre.

Sweep-test for yourself
The castor/camber sweep is something you can observe...And this is how?

1> Start the car
2> Drivers window down
3> Stand outside of the car
4> Turn the steering full lock left......And look a the left wing?
5> Turn the steering full lock right.....And look at the right wing?

What happened!
You have witnessed the bonnet rotating up-down as you turned the steering from lock-to-lock.

The reason for this is that the castor on the inner lock extended forward and by doing so lowered the car in a (simulated turn) "transition", if you take time to look at the attitude of the cambers on each lock you will also see the opposing positions (negative-positive)

Summery
Since the castor is a fixed angle you cannot manipulate how it manages the camber on the corner.... But you can manipulate the position of the adjustable camber prior to the corner and the acceptance of this relationship.

Another important point to note is that modifications are not generally without consequence..... The aim is to have as much benefit at the lowest sacrificial cost.

If in the case of your car you can retain reasonable tyre wear with elevated looks and handling then the rewards surpass the losses.

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Gerbo
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Postby Gerbo » Tue Oct 16, 2007 10:23 pm

The end positions are typical for the lowered car.... In truth this is not necessarily bad since the dynamic gains are reduced.

Down side is that the castor is very high so the steering may well feel heavy and we could have a conflict with the camber/castor on the corner but without some bench testing actual figures are impossible to predict.

Explanation
On the steer axis during cornering there is a mechanism to maintain as near to 100% tyre-tread contact patch.

This is a changing of values between the camber lean and the extension of the castor angle.

Maths example> For those that like that sort of thing.

Camber Change - If a wheel has positive Castor, then the top of the wheel leans into the corner whichever way it is steered. The change in Camber is approximately:

Camber Change = Castor x steer-angle / 60 (measured in degrees)
Example: Camber Change = 6 degrees
Steer-angle = 10 degrees
Then:- Camber Change = 6 x 10/ 60 = 1.0 degree

The change in camber that results from positive Castor is beneficial to the grip of both front wheels during cornering, providing it isn't excessive. A negative Castor (top of the steer-axis leaning forwards) changes the wheel Camber angles in the 'wrong' direction during cornering, this is not desirable.

Transitions
In a forward position the front cambers will be / \ (looking from the front) if for example this car turns to our left the transition of the camber (accentuated by the castor) will move the camber to \ \.

Curve
The gains left and right are dependant on the (adjustable camber) against the fixed castor.

If the dynamic positions do not correlate left/right then the angular gain generated against one incorrect camber on the corner will roll the weight distribution onto the sidewall and wear the tyre.

Sweep-test for yourself
The castor/camber sweep is something you can observe...And this is how?

1> Start the car
2> Drivers window down
3> Stand outside of the car
4> Turn the steering full lock left......And look a the left wing?
5> Turn the steering full lock right.....And look at the right wing?

What happened!
You have witnessed the bonnet rotating up-down as you turned the steering from lock-to-lock.

The reason for this is that the castor on the inner lock extended forward and by doing so lowered the car in a (simulated turn) "transition", if you take time to look at the attitude of the cambers on each lock you will also see the opposing positions (negative-positive)

Summery
Since the castor is a fixed angle you cannot manipulate how it manages the camber on the corner.... But you can manipulate the position of the adjustable camber prior to the corner and the acceptance of this relationship.

Another important point to note is that modifications are not generally without consequence..... The aim is to have as much benefit at the lowest sacrificial cost.

If in the case of your car you can retain reasonable tyre wear with elevated looks and handling then the rewards surpass the losses.



Im off to easons, saw a book there "suspension geometry for dummies", going to buy this along with a new collins dictionary. Then I might understand what he is talking about :shock: :shock: :shock:

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lex looter
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Postby lex looter » Tue Oct 16, 2007 10:28 pm

LOL
you spin me right round baby,right round,like a record,right round,round round

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shakey
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Postby shakey » Wed Oct 17, 2007 11:41 am

hahaha :lol: in eason eh!!!!!!!

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3S-GE
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Postby 3S-GE » Wed Oct 17, 2007 4:44 pm

Can I Have Your Old Tyres?? Plzzzzz . . . :lol:
BEAMS: Breakthrough Engine with Advanced Mechanism System.

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Dan
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Postby Dan » Wed Oct 17, 2007 5:08 pm

they are gone to tyre heaven im afraid Eric

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Bobby
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Postby Bobby » Thu Oct 18, 2007 6:10 pm

sounds like eric is lookin for burners :lol:
I BEG TO DIFF-ER!!

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altezza_nz
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Postby altezza_nz » Fri Oct 19, 2007 6:20 am

I'm going to ask a really dumb question here.

But is this the same as having a wheel alignment? :oops:

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Dan
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Postby Dan » Fri Oct 19, 2007 11:30 am

its basically just fancy alignment!

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elexes
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Postby elexes » Fri Oct 19, 2007 7:23 pm

but how dose it feel
if ive helped you in anyway vote for carlow to be the first tezzaworld drinking session


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