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wheel alignment - do I have too much caster? 

 

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 Post subject: wheel alignment - do I have too much caster?
Posted: Sat Jun 21, 2008 8:00 pm 
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Wheel alignment on EB just done. The final readings I was given have the caster at LH +5.8deg, RH +5.4deg. Specification in the Max Ellery manual gives 2.5deg as the max caster. Is this caster excessive? What is the effect of excessive caster? (and) How is the caster adjusted?

BTW the car has a shim type camber kit fitted.
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Posted: Sat Jun 21, 2008 8:28 pm 
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Does sound like a little too much caster, however its not going to destroy the handling if you can adapt to it.

More caster gives more stability in high speed on straights, and also gives more steering response in transitions of oversteer- for example: if you are drifting, when you want to transition the other way, the steering will flick back faster in the correcting direction, if you have more caster.

I guess just drive it and see if you like it, you can have too much caster, but not sure what would be "too much" on a falcon.

The catser is adjusted also by the shims in the top control arm.

Hope you understand this, i can't think of another way to explain it.

andrew.

 

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Posted: Sat Jun 21, 2008 8:45 pm 
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PIMP_LTD wrote:

More caster gives more stability in high speed on straights, and also gives more steering response in transitions of oversteer- for example: if you are drifting, when you want to transition the other way, the steering will flick back faster in the correcting direction, if you have more caster.



Does this mean the car will be more twitchy when correcting from losing the rear (oversteer) and likely to oversteer the other way? (or) Does this mean the car will be easier to correct comfortably from massive oversteer?
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Posted: Sun Jun 22, 2008 12:52 pm 
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My EBII owners manual says max. castor of 3.5deg, but i think the EA/EBI are different to the EBII/ED. I guess i'm saying Max could have made an error, or it could be worth checking anyway.

The steering ought to be firmer when turning, and as mentioned above have a greater effect of returning to centre.

 

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Posted: Sun Jun 22, 2008 3:40 pm 
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Thanks for the replies guys.

The spec Max quotes is for EA-ED, so 2.5deg is probably a typo. Yes the car does now take more effort to turn into corners, and will understeer initially, before oversteering if cornering is too enthusiastic.

Googling on wheel alignments tells me that optimum handling on a rear wheel drive is achieved with max caster (typically around 5deg), slight toe in, and a little negative camber. Apparently the greater the caster the more straight line stability is increased and more dynamic negative camber obtained when cornering, however the car will still turn in easier with lesser caster. I dont really need high speed stability as I dont do high speeds. I think that from the feel of the car it has a little too much caster.

The EB1 is slightly lowered and whilst certainly no race car, handling is important to me. Does anyone have any comments on optimum wheel alignment settings for the early E series. Probably a key consideration for me is controlability during oversteer. What are peoples preferences, and what settings work well on road cars.
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Posted: Sun Jun 22, 2008 6:48 pm 
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What you found googling is correct, except the toe part. Toe in is s**t, ideally even toe, or slight toe out is better, although toe out creates outer tyre wear a bit faster than normal. Toe in kind of corrects the wear that the neg camber gives.
Quote:
Does this mean the car will be more twitchy when correcting from losing the rear (oversteer) and likely to oversteer the other way? (or) Does this mean the car will be easier to correct comfortably from massive oversteer?


You kind of have the idea here. More caster will make the car return to centre faster, but not exactly "twitchy", more like fast but graceful.

For an example, the wheel alignment settings on my drift car are as follows
Camber - neg 4.5 degrees
Caster - pos 8.5 degrees
Toe - 4mm toe out.

These settings make the car very controllable, turn in to oversteer is very easy, just a light flick of steering wheel, or slight blip of throttle required to enter a drift, to transition the other way, the wheels flick be in the opposite direction fastly, but smoothly. The toe out helps to create "artificial extra lock" essentially giving more steering lock, while also helping with allover steering stabilty.

Personally, on my EB, when i get mine aligned properly, i will be aiming for 2.5 neg camber, 5 pos caster, and about 1mm toe out.

Hope this helps,

Andrew

 

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Posted: Sun Jun 22, 2008 8:42 pm 
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Thanks for that info Andrew. My camber is -0.60deg LH and -0.30deg RH. Possibly not quite enough, whilst toe in is 1.1mm total. Slightly more neg camber would probably help my turn in with the caster as it is, however the alignment Bob Jane have done is probably quite acceptable for a road car. I am yet to decide if I will be a difficult customer and whinge until they redo it. They do another free alignment at 5000k so I may just wait till then to get these specs changed. Also the slow steering response may be partly due to new tyres and tread squirm. From your info I would increase neg camber a little and go to around zero or slight toe out.

Do you like settings on both sides to be equal (camber, caster) or slightly different to allow for the camber of the road on a road car?

Regards Brett
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Posted: Sun Jun 22, 2008 9:50 pm 
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Yes, my settings must be same left to right on any car.

A couple of times i have had s**t alignments done, and have not paid until they did it again properly. In my own applications, i insist on the alignment to be perfect.

Most shops say that because of the slight camber on most roads, that the left to right should be different, and this is partially true for a road car, however they sometimes use this as an excuse for them to get a little lazy. The cars they service still drive fine, but could be better.

My cars with my own settings (same left to right and my figures) have always behaved great on roads, yet handle like a kitten on carpet on the racetrack or mountain road. :D

At the end of the day, if you like to drive in a way that requires such specific settings, alignment is all about following guidelines, and experimenting with settings until you find something that you like, and that suits your all round driving style.

When you get it redone, make sure they do it how you want it. Wheel alignment is a delicate thing.

:thumbsup:

Andrew.

 

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Posted: Tue Jun 24, 2008 12:32 am 
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PIMP_LTD wrote:
Toe in is s**t, ideally even toe, or slight toe out is better, although toe out creates outer tyre wear a bit faster than normal. Toe in kind of corrects the wear that the neg camber gives.

The idea of having slight toe-in when stationary is so that when rolling resistance enters the equation the wheel ends up close to neutral. When RWD cars i've had have had toe-out they've driven pretty horrible.

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Personally, on my EB, when i get mine aligned properly, i will be aiming for 2.5 neg camber, 5 pos caster, and about 1mm toe out.

One of my EBII's had about 2.5deg or more neg camber when i got it and it was twitchy, but there are a number of other factors that played a role in that. I put more shims in to sort that out, the front doesn't look broken anymore ;)

 

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Last edited by relaxed_diplomacy on Tue Jun 24, 2008 2:01 am, edited 1 time in total.

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Posted: Tue Jun 24, 2008 1:00 am 
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any more than -1 deg camber you will wear inside of the tyres,its multiplied when going around roundabouts,taxis have left hand extreme tyre wear.what size tyres are you running?how fast do you drive?

 

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Posted: Tue Jun 24, 2008 2:15 am 
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Im running 1.5neg camber 2.5 pos caster and 0 toe and have found that pretty good for street trim.
My 2c.
oh and the same both sides.

 

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Posted: Tue Jun 24, 2008 2:25 am 
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It may be that front ends fitted with nolathane bushs justify/require a slightly lesser amount of toe-in than the factory setting, due to being stiffer and therefore less affected by the forces generated by rolling resistance. But maybe the difference is so small as to be negligible.

 

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Posted: Tue Jun 24, 2008 8:17 am 
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a diagram that helped me to understand this discussion......

 

 

Attachments:
wheelangles.jpg
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Posted: Tue Jun 24, 2008 7:58 pm 
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EB92 wrote:
a diagram that helped me to understand this discussion......
very nice drawing,the best i have seen.nolathane bushes stiffen the front alot----have you checked all your front moving parts for excess wear,as it will change rapidly---check your tyre wear--often.

 

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Posted: Tue Jun 24, 2008 10:13 pm 
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Well I went back to Bob Jane who were more than happy to change my settings to what ever I wanted at no charge, however he talked me into leaving the settings the same. If I went to -1 or -1.5deg camber warranty on the alignment and new tyres would be void. He claimed that at -1deg camber the tyre life would be vastly reduced (std on falcon is -.25deg). As for toe out, he claimed that with the 240+ k's on the front end my 1.1mm toe in would translate to around even dynamically. As for even both sides, his argument concerning allowing for the camber of the road was convincing. Considering the age of the suspension components, the fact I only bought cheap tyres anyway, and that the car handles so much better than it was before alignment and tyres, I will wait for my free 5000k alignment and change the settings then if it looks like my front end can maintain an alignment.

As for my original question "Is my caster too great?" my research suggests that the more positive caster the better as it increases dynamic negative camber, and as Pimp Ltd pointed out it aids in correcting oversteer. Thanks for this most useful discussion guys.
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