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Author Topic: Best track alignment set up?  (Read 19201 times)

Offline the bruce

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Re: Best track alignment set up?
« Reply #15 on: June 26, 2011, 07:17:33 pm »
A change of weight distribution does happen in the moment you start
turning the steering wheel. Something very similar does happen when
you hit the brake pedal.

No doubt - maximum G requires different slip angles outer and inner
wheel.

I don't know why they align toe out. I just wonder why they do so.
Maybe the individual steering kinematics is the key point.

Just try both on your own - toe in and toe out - and you'll know more.
In case of us non-professionals it may be way a question of taste.
"You get what you pay for."

Offline _Nathan_

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Re: Best track alignment set up?
« Reply #16 on: August 10, 2011, 05:10:03 pm »
Page 25 of this months Race Car Engineering magazine confirms my thoughts and gives the reasons why.  :happy2:
E90 M3, E46 CSL Race car

Offline rex

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Re: Best track alignment set up?
« Reply #17 on: August 12, 2011, 01:36:02 pm »
Meaning that the information presented above is correct?

Offline the bruce

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Re: Best track alignment set up?
« Reply #18 on: August 12, 2011, 07:02:06 pm »
Would like to have a view on that page.  :smiley:
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Offline _Nathan_

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Re: Best track alignment set up?
« Reply #19 on: August 12, 2011, 10:18:07 pm »
It was in answer to a question regarding why the popular wisdom of toe out for turn in is correct, was answered by a chassis consultant specialising in handing and chassis set up, I typed the answer out for you:

"Cars do generally exhibit quicker initial turn in with static toe out. My analysis is that this does not have to do with the lateral (y axis, per SAE convention) forces from the front tyres, but rather the longitudinal (x axis) forces, which can produce yaw moments.

When a car is running straight, and the front tyres have either toe in or toe out, the tyres are both running at a slight slip angle, and accordingly generating both some lateral forces and some drag forces. The drag forces are roughly equal and additive. The lateral forces are roughly equal, and opposite in direction, so they approximately cancel.

When the steering wheel is turned just a tiny bit, one front wheel will be running straight, the other will be turned in to the corner, generating a bit of drag, and some lateral force in to the corner.

If the car has toe in, it will be the inside front wheel that's running straight, and the outside one that has some slip angle. In this condition, the lateral force creates a yaw moment into the turn, but the drag force creates a yaw moment out of the turn. The two yaw moment components are subtractive.

If the car has toe out, it will be the outside front wheel that's running straight, and the inside one that's making lateral force and drag force. Now the lateral and drag force both create yaw moments into the corner, and are additive. Consequently, the net yaw moment is greater, and the car experiences a greater yaw acceleration. That is it turns in quicker. "

It is a good magazine, I suspect you'd like it.

www.racecar-engineering.com
E90 M3, E46 CSL Race car

Offline Tfsi_Mike

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Re: Best track alignment set up?
« Reply #20 on: August 12, 2011, 11:05:51 pm »
I've nearly posted querying best fast road alignment a few times but it gets super technical super fast.  :sad1:

Offline the bruce

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Re: Best track alignment set up?
« Reply #21 on: August 12, 2011, 11:49:27 pm »
Thank you, Nathan.  :happy2:

I understand the argumentation, but I guess you understood the
one I posted before.
Drag and yaw components will be present, but weight distribution
will be as well.
So toe out is causing some amount of delay in the first moment.

The race engineer I asked prefered toe in and VW Racing did so
on Laurent's car.

I guess if you ask 10 engineers you'll get 11 answers. Both have
(pretty good) arguements and the rest is a questions of personal
preferences, at least on our kind or cars.
"You get what you pay for."

Offline _Nathan_

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Re: Best track alignment set up?
« Reply #22 on: August 13, 2011, 09:53:54 am »
Be interesting to see why these people are going against popular wisdom though, every text book I have ever seen suggest toe out.

Maybe the books are all talking about proper race cars rather than soft road cars, or maybe it is just a case that VWR think toe out on a track car that is also used on the road is too nervous on the road (and to be honest it would be a nightmare with following road cambers etc).

When my CSL was a road car with aftermarket suspension (Intrax so adjustable top mounts) I had it set up for parellel toe on the road but a quirk of the BMW is that the chassis slots in which the top mounts are secures are approx 1 degree from inside to outside so with the car in the road it'd be fine running parellel and 2 degrees negative camber but get to the track loosen 5 bolts each side, push the top mount inwards are far as it would go and you ended up with circa 3 degrees camber and toe out, after the day move the top mount as far out as it would go to get back to your original road settings. That is a case in point of track settings that would be horrible on the road and give uneven tyre wear yet on the track tyre wear was perfect and turn in was brilliant.

In summery perhaps everyone needs 2 cars, one set up for road and one for track  :grin: :grin: :grin:
E90 M3, E46 CSL Race car

Offline rich83

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Re: Best track alignment set up?
« Reply #23 on: August 13, 2011, 10:00:35 am »
Can a little toeout on the front make up for the slow steering rack?

Offline Tfsi_Mike

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Re: Best track alignment set up?
« Reply #24 on: August 13, 2011, 10:03:07 am »

Ever hear of mkIV racks been used as the response is quicker?

Offline the bruce

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Re: Best track alignment set up?
« Reply #25 on: November 04, 2011, 01:18:22 pm »
Fuscobal has good results with the Mk.VI steering rack.
Electro-mechanic as well but solid mount instead of rubber on Mk.V.

Steering rack of Seat Leon Supercopa may fit as well, but hydraulic
instead of electric and so an additional pump is needed.

I will give the Whiteline steering rack mount a try.  :wink:
"You get what you pay for."

Offline the bruce

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Re: Best track alignment set up?
« Reply #26 on: November 04, 2011, 01:34:01 pm »
Fuscobal has good results with the Mk.VI steering rack.
Electro-mechanic as well but solid mount instead of rubber on Mk.V.

Steering rack of Seat Leon Supercopa may fit as well, but hydraulic
instead of electric and so an additional pump is needed.

I will give the Whiteline steering rack mount a try.  :wink:
"You get what you pay for."

Offline dionet

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Re: Best track alignment set up?
« Reply #27 on: February 14, 2012, 01:26:33 am »
I don't know if this information is any good, but i have done quite a bit of karting, and on a wet track we have always run WAY more toe out, than in dry conditions, this really sharpens the turn in..

In wet we would run 5-6mm toe out each side :surprised: And in dry about 0,5 mm each side, but when you sit in the kart it will flex, so it would likely be around 0, or a little toe in..

Just thought i would share this :smiley:
« Last Edit: February 14, 2012, 01:29:03 am by dionet »