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Discussion Starter #1
I know it's referring to how willing the car is to start turning, can someone explain it better? R&T mentions the IS300's "voracious turn-in".
 

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Obviously, a car with centralized mass for a body with low rotational inertia.

In terms of suspension geometry it's a combination of:

1. front camber close to zero deg to give you the maximal contact patch at no body roll
2. low caster (kingpin angle close to vertical) to maintain that contact patch with the wheels turned, but with the body yet to roll
3. low "lateral caster" (lateral kingpin angle close to vertical, don't have the term for it) to not lose contact patch in turning the wheels while the body has yet to roll
4. front toe-in close to zero, or even toe-out
5. Ackerman close as possible to "perfect". (Long definition omitted)

But you'd also need tires with nice stiff sidewalls and a low slip angle.

Basically, you're making sure that as much of the front tires' contact patches are available at zero body roll (body still going straight) but with the wheels turned, slightly or more.

(Of course this doesn't necessarily mean that the maximal contact patches will still be there when the body begins to roll after turn-in, or even in the instance when you compress the front suspension by braking weight transfer. Real-life tuning for good turn-in is a compromise of these complications, in addition to tuning out some turn-in so the car doesn't spin at the slightest jerk of the steering wheel.)

(Amazing what you learn playing with R/C cars.)

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051/LP/SR/LD/HH
 

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Ahhh! Luc, stop!

You're givin' me a swelled ego, and that gets me into Overlord mode. Trust me, it ain't classy or pretty!

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051/LP/SR/LD/HH
 

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Originally posted by DtEW:
Obviously, a car with centralized mass for a body with low rotational inertia.

In terms of suspension geometry it's a combination of:

1. front camber close to zero deg to give you the maximal contact patch at no body roll
2. low caster (kingpin angle close to vertical) to maintain that contact patch with the wheels turned, but with the body yet to roll
3. low "lateral caster" (lateral kingpin angle close to vertical, don't have the term for it) to not lose contact patch in turning the wheels while the body has yet to roll
4. front toe-in close to zero, or even toe-out
5. Ackerman close as possible to "perfect". (Long definition omitted)

But you'd also need tires with nice stiff sidewalls and a low slip angle.

Basically, you're making sure that as much of the front tires' contact patches are available at zero body roll (body still going straight) but with the wheels turned, slightly or more.

(Of course this doesn't necessarily mean that the maximal contact patches will still be there when the body begins to roll after turn-in, or even in the instance when you compress the front suspension by braking weight transfer. Real-life tuning for good turn-in is a compromise of these complications, in addition to tuning out some turn-in so the car doesn't spin at the slightest jerk of the steering wheel.)

(Amazing what you learn playing with R/C cars.)

amazing what is currently flying over my head reading that damned book...
back to reading...


[This message has been edited by HIBBoyScott (edited March 26, 2001).]
 

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Discussion Starter #6
Thanks DtEW, but I'm really asking what does it feel like to the driver. Someone complained that a BMW 540i, no matter what he does to it, "Doesn't turn in". I assume that's cause it's heavy. The IS300 is heavier and not 50/50 weight balanced like the BMW 330, yet has better turn in, is this just suspension geometry? Quicker steering?
 

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Originally posted by ckolsen:
Thanks DtEW, but I'm really asking what does it feel like to the driver. Someone complained that a BMW 540i, no matter what he does to it, "Doesn't turn in". I assume that's cause it's heavy. The IS300 is heavier and not 50/50 weight balanced like the BMW 330, yet has better turn in, is this just suspension geometry? Quicker steering?
maybe it isn't the total weight but where the weight is on each car...i don't know how each car's weight is distributed so...just fwiw...if you had a car that weighed only 2000lbs that would be light right...but if the weight was concentrated on the bumpers you'd have a hell of a time turning it...if there was another car that weighed 4000lbs that would be a lot...but if that weight was situated near the center of the car it could be turned effortlessly...
 

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I am not a suspension expert, so correct me if I am wrong. A car with good turn-in should allow the driver to feel effortlessly when going into a corner. If you turn the car into a corner, and the car does not resist at all, then the car has good turn in. It is more to do with just weight distribution of the car and the weight itself. It has to do with how the car's balance is shifted to you turn the wheel. A good turn in car generally has either very little understeer or a bit of oversteer (such as go-kart).
This is why I said my car now has S02 Poleposition (at 35psi) and a good alignment have very good turn in compare to the stock tires. The car feel alot closer to neutral, and you do not have to do anything when turn into a corner, because the car just seem to do it by itself.
 
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