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Toe out


StewartG

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What benefit does a little toe out endow upon one's trusty steed? I'd like a faster steering response and less self centreing as although I'm happy with the under/oversteer balance it does take some effort to hold the car in the turn, if you know what I mean.
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Toe-out will make it 'sharper', more inclined to change direction. The way it loads up is dictated by the amount of castor. On a De Dion chassis you can adjust the castor by playing with the number of washes in front of/behind the legs of the lower wishbone. More castor (moving the wishbone forwards) gives more self-centering action (higher effort), but has the advantage of giving more camber with lock and also improves steering 'feel'.

 

Mike

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Mike.

 

I did this washer adjustment as the car was too 'live' on the steering when I first got it. It helped but couldn't cure it completely. To cut a long story short I used a different tyre pressure gauge. The one I had said 20 lbs etc. A borrowed one showed the true reading as 30lbs!! Needless to say the digital readout 'wonder' went back to Halfords. Have stuck with the 'heavy steering as it seems to elleviate the tramling effect.

Handling/steering = 100% better!!!

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You can get really nasty effects by getting a mismatch between castor and camber. If you alter one you have to optimise the other for the new setting before you can discard the setting as being gash.

 

I'm not recommending anything other than a suck it and see approach; just perhaps a structured suck it and see approach.

 

Generally, if you start by altering the parameter which has the fewest settings (castor) you should be able to bracket the appropriate castor pretty quickly. For me it was two washers either side. You can then forget about castor and move on to thinking about camber. Throughout camber changes, keep the toe straight ahead. Bracket the camber until you have what you like. Then tweak the toe either side of straightahead.

 

However, Stewart's question regarded steering weight building up in the corner. This is because he is holding the front end in against the chassis natural tendency to understeer. Rear steering by raising the ride heights will sort this out. Just alter it a small amount at a time.

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"However, Stewart's question regarded steering weight building up in the corner. This is because he is holding the front end in against the chassis natural tendency to understeer. Rear steering by raising the ride heights will sort this out."

 

How can you be sure? His symptoms (too much self-centering) sound exactly castor-induced to me.

 

Mike

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You're right. I'm not sure. My words may have sounded like I was sure, but it was merely a hunch and a hell of a lot less hassle to try out than a full re-jigging of the front end. I would advise a suck it and see approach above all others.

 

If I have a point it is this: Received wisdom describes "more castor gives you more self-centreing". This is an over simplification. If Stewart changed the castor and didn't attempt to optimise the other settings then the investigation would be futile. If the weight in the steering is being caused by some other imbalance then the investigation should start by optimising the current castor and camber set up, because anti-roll bars and rear ride height are easy and quick to change and castor/camber aren't.

 

Not sure I've ever been this concise on this topic.

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PC and MB let me get this straight. To reduce self-centreing I need to reduce the amount of castor, to do this I must move the lower wishbone forward that's what someone technical at Caterham said, however MB's earlier post says the opposite who's right?
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Peter obviously for me this week's seven puzzler is castor. I'm assuming that it's the same principle as the rake on the front forks on a bike, the steering pivot is not vertical but the lower end of the pivot is further forward than the upper end. On a bike the closer to vertical the pivot is the faster the steering with less self-centreing. Presumably the further back the lower wishbone is located (more washers in front of it) the closer to vertical is the pivot etc etc etc. Although I didn't realize the consequences I already have two washers in front of and one behind the wishbone so I guess I'm not going to get less self-centreing from that department maybe experimenting with my original toe-out idea is next or maybe a little more camber or a stiffer front arb only time will tell. Thanks for the feedback and if the above is incorrect I'm sure you'll let me know.
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Stewart,

 

The washer count is for the rear leg of the lower wishbone and there should always be four washers in some distribution on each side of the leg. At the same time you move washers from behind to in front of the rear leg, you have to remove washers from the front mounting. I think the count you have made is from the front mounting.

 

If you were describing the front leg of the wishbone, then one washer behind the front leg should equate to one washer behind the rear leg/three in front. This is the one step away from least castor position - probably about 6 degrees. I prefer mine with 2/2 which is about 6.5 degrees, but it will depend on tyre type and suck it and see changes to all other settings.

 

Peter

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Peter I know everyone else has a total of four washers locating the lower wishbone rear pivot but mine has only ever had three and it's a pretty tight fit to get all three in place, maybe I've got thick washers. I'm waiting for the roads to be dry enough to see if the changes I've made are noticeable.
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