Positive/negative camber clarification
paul_joh...@my-deja.com
top of the wheels and positive camber means the
wheels are farther apart at the top of the wheels? I was told that the
camber for the front of my 71 SB is 1 degree positive,
i.e. farther apart at the top. I have been messing with this and I am
starting to question what I know and what I think I
know.
As viewed standing in front of the car:
Positive camber \\ //
Negative camber // \\
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David Sayler
someone would want neg./ pos. camber.
MOON CHASER WOLF
top is out. you never want a lot of positive because when you turn hard your
turning on the outside of the tire. the trick is to have enough neg so that
when you corner the tire flattens out on the road giving you all the tread on
the road surface. but tooooo much neg and you will be wearing out tires fast
DJ
>Am I correct that negative camber means the wheels are closer at the
>top of the wheels and positive camber means the
>wheels are farther apart at the top of the wheels?
>As viewed standing in front of the car:
>Positive camber \\ //
>
>Negative camber // \\
Essentially this is correct.
David Sayler wrote
>Good question. Could whoever responds to this also clarify the reason why
>someone would want neg./ pos. camber.
The ideal suspension is one which maintains zero camber throughout it's
travel (or at least at the point in travel which is most critical to
performance) as well as during lateral chassis loads. Maintaining zero
camber maintains maximal tire contact and thus maximum potential traction,
directional control, and thrust.. Many things effect traction or grip such
as tire composition, tire pressures, temperature, speed.
Many vehicles are limited by their suspension design to the degree to which
they can maintain zero camber, and other times, resting loaded camber is
altered to obtain a camber benefit somewhere else in the travel arc.
In off-Road racing vehicles which require extreme lengths of travel in the
suspension, you see large camber changes from large negative thru zero to
positive cambers; Most are set up with sometimes substantial negative camber
in the resting loaded suspension in order to assure minimal positive camber
at the extreme bottom of the suspension travel. This way when the vehicle
clears an obstacle which drops the suspension to it's maximal bottom travel,
as close to zero camber is maintained, and control is maintained when the
hi-speed vehicle recontacts the ground or whenever the chassis is unloaded.
The last thing you want is to "jack", or fold an axle or control arm up
under your vehicle at a hi rate of speed.
An excellent example of this phenomenon is the swing axle rear end found in
older VWs. The swing axle has a high roll center, and experiences increasing
camber when unloaded such as under heavy braking or rapidly changing lateral
movement, this also happens with semi-trailing arms like those found on my
old Triumph TR6. It had somewhat less "jacking" tendency, but when the
trailing arms bolts pulled out of my rusted frame, the rear wheels wanted to
tuck under if the car was driven in reverse.
Vehicles which might benefit from a somewhat positive camber might be a drag
car which tends to have it's suspension loaded throughout it's run. A slight
positive resting camber might result in something closer to zero when under
load, and give maximal tire contact.
Does this help in understanding camber? A couple of books I have read that
help explain chassis setups are "Chassis Engineering" by Herb Adams, and
"How To Make Your Car Handle" by Fred Puhn. Both are put out by HPBooks, and
are probably available at Borders or Barnes and Noble.
Hope this helped some,
Doug
paul_joh...@my-deja.com
> The ideal suspension is one which maintains zero camber throughout
it's
> travel (or at least at the point in travel which is most critical to
> performance) as well as during lateral chassis loads. Maintaining zero
> camber maintains maximal tire contact and thus maximum potential
traction,
> directional control, and thrust.. Many things effect traction or grip
such
> as tire composition, tire pressures, temperature, speed.
To the point of being redundant. The 1 degree of camber specified for
my 71 SB is therefore assumed to be negative camber (closer at the top).
DJ
paul_joh...@my-deja.com wrote
<snip>
>To the point of being redundant. The 1 degree of camber specified for
>my 71 SB is therefore assumed to be negative camber (closer at the top).
The 1 degree of camber for the stock Super Beetle McPherson strut suspension
is positive 1 degree +20' to -40'.
+20' =+20 minutes. Degrees are divided into minutes and minutes into
seconds. Bentley also states that the camber difference between wheels
should be no more than 30'.
Doug
Mike Fritz
have 1 degree positive camber. I don't know where my Bently is, so I cannot
verify. And I believe the rear is 1 degree negative camber. It is my
opinion that the positive camber is to compensate for a full trunk/tank.
Mike
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paul_joh...@my-deja.com
Mike Fritz <mwf...@psn.net> wrote:
> IIRCC My 74 Super (different from the 71-73 Super slightly) is
supposed to
> have 1 degree positive camber. I don't know where my Bently is, so I
cannot
> verify. And I believe the rear is 1 degree negative camber. It is my
> opinion that the positive camber is to compensate for a full
trunk/tank.
> Mike
>
and clean trunk. I suppose in the factory that would have been the
case. I guess I could measure my camber with the trunk and tank both
empty and full and see if there is a difference. It just seems odd to
me to put a positive camber on the front after reading that write-up
from DJ. By the way that was a very good explanation DJ. Maybe another
possibility is that the front end rides down a bit while driving such
that you get 0 camber while driving yet positive camber while sitting.
DJ
paul_joh...@my-deja.com wrote
>If you are right, then you should adjust the camber with an empty tank
>and clean trunk. I suppose in the factory that would have been the
>case. I guess I could measure my camber with the trunk and tank both
>empty and full and see if there is a difference. It just seems odd to
>me to put a positive camber on the front after reading that write-up
>from DJ. By the way that was a very good explanation DJ. Maybe another
>possibility is that the front end rides down a bit while driving such
>that you get 0 camber while driving yet positive camber while sitting.
I agree with Mike; The 1 degree of positive camber is likely to compensate
for a full tank of gas and the possibly full front boot...remember how much
larger the front capacity is in a Super. The point is that no matter how you
setup your suspension statically it will change since your suspension is by
nature dynamic, as are the conditions under which it operates (amount of
fuel wt., cargo wt., tire wear, etc.).
Now if you had just installed new balanced rims and tires, and rebuilt the
entire front end with new inserts, springs, bushings and such, and you KNEW
the normal operating frontend weight for YOUR car (i.e., you consistently
keep the tank at approximately the same level, and always load the boot the
same way) then you could set your camber at zero....for awhile. All car
tuning is like life...it is a series of trade-offs, and determining
priorities, and priorities change over time like everything else.
I won't sweat that little bit of positive camber in a daily driving car, we
not running at Hochenheim you now (you're not are you?). Those folks at VW
had some good ideas about cars, so I'll be setting mine at 1 degree
positive.
Doug
ANT The Monarch of Menace
arm suspensions) these shouldn'e have any camber change due to VERTICAL
suspension movement.
I'm not taking into account sideways forces exerted when going into corners
etc.
This suspension will see a bit of caster change though--at least the ball joint
front ends anyways.
-ANT
paul_joh...@my-deja.com
setting. I am buying Doug's theory that dynamic driving conditions
probably see 0 degree camber. I also know VW has done a lot of testing
over the years and most likely determined 1 degree+ was the best
compromise between handling and tire wear under actual driving
conditions. Thanks for the input.
ANT The Monarch of Menace
>setting.
I disagree. You're probably best of with at least 1 degree negative, especially
with the skinny stock tires. The moment you go into a curve that 1 degree
negative will immediately go away and you'll be at least at zero.
This is just like toe settings. The reason they're set negative (pointing
inwards at the front of the tires) is that when the car starts rolling the
normal slop in the linkage (ALL cars have a certain degree of freeplay, even
brand new ones) will force the wheels outward, so now they'll actually be
straight ahead.
Git it?
-ANT
Koyte 1
angles involved, SAI [steering axis inclination] or KPI {king pin
inclination} and incuded angle work together with camber to determine
other angles including scrub radius, toe in or out and toe out on turns.
On the rear camber is set negative to help with lateral stability while
caster on the front takes care of this. Caster also helps with
returnability ofthe steering wheel. On manual steering caster is set
negative to make it easier to initiate the turn at low speeds whereas in
power steering it is set positive to help with retunability and
stability. Positive camber on the front wheels also transfers the weight
of the vehicle to the larger inner wheel bearing. Camber is also set
positive on the front due to anticipated load on the suspension be it
fuel/ luggage or just passengers. This can bee seen to extreme on any of
the Ford E and F series trucks with twin I beam suspension.
Yes you are right that VW and all other manufacturers spent many years
and a lot of money to determine the best setting for alignment.
Hope this helps
Dan
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Koyte 1
tires are farther apart at the front edge. Negative camber will result
in the vehicle wandering more than it should and will require more
steering correction on the part of the driver. The tires are set with
positive toe [in at the front] not so that they will be pushed apart due
to the slop in the linkage but as a result of the scrub radius. Most
front wheel drives have a scrub radius opposite to rear wheel drive and
as a result toe is set negative [out at the front]. In actual fact there
are very few vehichles, front or rear wheel drive that are set with
negative camber. Of the American made vehicles the only one that comes
to mind is the 96 to current Ford Crown Victoria that calls for negative
camber on the front wheels.
In article <20001231150201...@ng-cs1.aol.com>,
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Mike Fritz
negative when it's underload? When turning a curve, I don't think the outside
wheel curves under making it more positive.
Mike
--
Koyte 1
the bottom of the tire goes out as the body comes down thus giving you
negative camber. In a turn, as the body rolls out, the outer wheel gets
more negative camber while the inner wheel goes positive. Similar to the
"grader effect".
Dan
In article <3A50A774...@psn.net>,
--
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ANT The Monarch of Menace
>negative when it's underload? When turning a curve, I don't think the outside
>wheel curves under making it more positive.
I give up, I can't take it no more. Where's my Vodka?
-ANT
Jan Andersson
ANT The Monarch of Menace wrote:
>
I drank it.
Jan
ANT The Monarch of Menace
>> -ANT
>
>
>I drank it.
You dirty rat bastid! Now I'll have to go back to guzzling Sterno.
-ANT