Traction Brackets...

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jondee86
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Traction Brackets...

Postby jondee86 » Mon Jul 14, 2014 10:36 pm

This is what an AE86 traction bracket should look like...

Image

Because the holes that these install to in the factory axle bracket are
different sizes, the traction bracket needs special hardware. One spacer
tube that fits inside the factory bracket, and one that actually fits inside
the factory holes. If this hardware is not correct, the traction bracket
will be able to move under load... and it needs to be locked in position.

Notice also that there are three positions available for the end of the
lower trailing link to be secured. The holes should be slightly stepped
in an arc that follows the movement of the trailing link. These allow for
some tuning of the linkage geometry without changing the pinion angle.

Here are some (not the ones pictured above) installed...

Image

So what do traction brackets do, and should I have them on my car ?

Traction brackets are loosely the rear axle equivalent of the bump steer
spacers (RCA's) that are installed in the front of your AE86 after you have
lowered the car by 40 or 50mm. Dropping the car throws the factory links
out of alignment, which has a negative effect on certain handling
characteristics. On the rear axle two separate settings are affected...

Pinion Angle
Because the AE86 has unequal length trailing links, as the axle moves up
and down, the top arm turns thru a smaller arc than the lower arm. This
causes the nose of the pinion shaft to pitch down as the car is lowered.
When this happens, the axis of the pinion is no longer parallel to the axis
of the front half of the drive shaft, and the universal joints no longer have
equal angles. This is not good for the universals. Pinion angle is corrected
by the use of adjustable length trailing links.

Image

Trailing link Geometry
Real suspension geometry is way too complicated for me, but simplified
down, lowering the car changes the angle of the lower trailing link. This
is the link that is in compression when the car accelerates, explaining why
the lower arm is sturdy, while top arm (in tension) is skinny.

As the wheel rotates in one direction, the rear axle tries to rotate in the
opposite direction. This twisting motion is resisted by the lower trailing
link pressing against the short factory bracket. The force generated in the
link is transmitted to the chassis to accelerate the car. The angle of the
link determines how this force is applied to the car.

Image

If the link angles down from its attachment point on the axle, then the
force will try and push the car down (push axle up). If it angles up, then
the force will try and push the car up (push axle down). Easy to figure
then that if the axle is being pushed down, the tires will be able to get
more grip. This is where the traction bracket comes in... by lowering
the attachment point, it brings the angle of the lower link back to where
the factory wanted it to be.

Axle Wrap - Wheel Hop
The factory trailing links are fitted with rubber bushings to keep noise
and vibration levels down. Unfortunately, rubber is also compressible,
and when subject to heavy loading as the rear axle tries to rotate under
acceleration, the bushings allow a degree of movement. Old, worn out
bushings allow more movement, and under heavy loading when the wheels
start to slip, a rapid cyclic rotation can occur in the rear axle.

This is experienced in the form of "wheel hop"... a violent jumping up
and down of the rear axle which really spoils that big skid you were trying
to lay down :P

Fresh hard rubber or poly bushings resist compression, and go a long way
towards eliminating wheel hop. Traction brackets also help by lengthening
the torque arm (distance of the link end from the axle tube), correcting
the angle of the lower arm, and in some cases, improving the pinion angle.

So, do you need traction brackets ? For moderately lowered cars (<30mm)
street cars... probably not. For more than 40mm down and competition
cars, there are definite benefits to be had from traction brackets used
with adjustable rear links.

Cheers... jondee86
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phanist
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Re: Traction Brackets...

Postby phanist » Mon Jul 14, 2014 11:58 pm

beautiful write up wish you did last year while i was fighting to get my pinion angle right.....
:)

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Re: Traction Brackets...

Postby assassin10000 » Tue Jul 15, 2014 6:17 pm

Perfectly inline driveline is not good. Prematurely worn out u-joints will occur.

Andrew

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Re: Traction Brackets...

Postby riddleyo » Tue Jul 15, 2014 8:06 pm

Thank you for the excellent write up

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jondee86
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Re: Traction Brackets...

Postby jondee86 » Tue Jul 15, 2014 8:20 pm

assassin10000 wrote:Perfectly inline driveline is not good. Prematurely worn out u-joints will occur.

Funny enough, I was going to put that in, but decided not to introduce
another complication :) In the automotive world, I would expect that the
normal movement of the suspension would provide enough change of
angle to ensure lubrication. But if used in an industrial application
where both ends of the shaft are attached to static machines, perfectly
in-line would be fatal.

Cheers... jondee86
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idreamofdrifting
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Re: Traction Brackets...

Postby idreamofdrifting » Wed Jul 16, 2014 11:25 am

+1 Fantastic.

I've driven my lowered 86 without them, and with them.
Difference is night and day.
When you car is lowered significantly, traction brackets is a must!
Last edited by idreamofdrifting on Thu Jul 17, 2014 8:29 pm, edited 1 time in total.
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phanist
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Re: Traction Brackets...

Postby phanist » Wed Jul 16, 2014 2:54 pm

So your upper and lower link should be in an upward angle when your car is lowered on the ground?
From diagram above the leveled paralled link is bad setup correct?

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Re: Traction Brackets...

Postby jondee86 » Wed Jul 16, 2014 4:01 pm

phanist wrote:So your upper and lower link should be in an upward angle when
your car is lowered on the ground? From diagram above the leveled
paralled link is bad setup correct?

Have a read here... http://www.hachiroku.net/5link

I believe that the Toyota factory engineers did a pretty good job when
they designed the AE86. So I try not to change any of the basic suspension
geometry when modifying my car. In the front I dropped 40mm so I used
40mm RCA's to put the lower control arm and steering link back to the
factory angles.

While I don't have Traction Brackets on my car, if I was to put them
on, I would drop the end of the trailing arm to use the holes that are
closest to 40mm down from the factory fixing holes. That way the angle
of the trailing arm will be restored back to factory.

Real suspension engineering is very technical (beyond me), and changing
the angle and length of trailing links can affect the cars handling in many
ways. But as I see it, changing the angle of the lower trailing link mainly
affects the squat/anti-squat characteristics.

If the link is parallel to the ground, the driving force does not change
the force holding the tire to the road. A link that slopes up from the axle
will add downward force on the tire (anti-squat) and a link that slopes
down will reduce the force on the tire (squat). NOTE that these changes
in forces are dynamic, and only exist under hard acceleration. While
cruising or stationary, the angle of the link will have no noticeable effect.

What this means is that if you want traction off the line and out of low
speed corners, your lower link should slope up. If you want your car to
slide easily, parallel to the ground would be the way to go :)

As the rear of the car has a natural tendency to drop due to "weight
transfer" under acceleration, this will change the angle of the lower
trailing arm. So springs also need to be considered when tuning rear
suspension. Trying a number of settings over the same piece of track
is the practical way of finding the angle that works for best for you.

Cheers... jondee86
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Re: Traction Brackets...

Postby gotzoom? » Thu Jul 17, 2014 9:39 am

In a perfect world, you would want the upper and lower links to be the same length, parallel to each other and roughly parallel to the road surface. Traction brackets can help you achieve near parallel to the road surface on the lower links, but there is no way to do this on the upper links without modifying the pickup points on the chassis. Unfortunately, as you lower the car, the upper link angle starts to increase quite dramatically, which also introduces binding, which further reduces grip, particularly under cornering.

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Re: Traction Brackets...

Postby jondee86 » Thu Jul 17, 2014 5:59 pm

Yes... the problems of spring wrap and axle tramp have been
well known to the hotrodding fraternity since forever. Anti-tramp
bars were more or less standard fittings on any car with leaf springs
in the rear. Serious AE86 race and rally cars also use traction boxes
with equal length links, and these are available as kits from several
aftermarket parts suppliers...

Image

The only problem with these is that they do require cutting, welding
and fabrication skills, that are not always available to the average
DIY guy.

Image

Personally, if I was having a problem in controlling the rear axle and
decided to modify, I would be going for something like the old school
hotrod ladder bar setup.

Image

This eliminates the upper links and converts the rear to 3 link. Putting
a Watts Linkage in to replace the lateral bar would make a pretty solid
rear end.

Cheers... jondee86
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Re: Traction Brackets...

Postby RuizXIII » Fri Jul 18, 2014 8:50 pm

A lot of good suspension technical info here. Learning is a good thing.
irony.cc

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Re: Traction Brackets...

Postby phanist » Fri Jul 18, 2014 11:08 pm

jondee

never fail to impress me.. alway take time to explain every thing with details :D

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Re: Traction Brackets...

Postby jondee86 » Fri Jul 18, 2014 11:55 pm

Everyone loves pictures ;)

Cheers... jondee86
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Re: Traction Brackets...

Postby riddleyo » Sun Jul 20, 2014 8:15 pm

Speaking of which, host that last picture from lugnutz somewhere because they don't allow direct linking and we can't see it!

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Re: Traction Brackets...

Postby jondee86 » Mon Jul 21, 2014 1:07 am

Done :)

Cheers... jondee86
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Re: Traction Brackets...

Postby sooty » Mon Jul 21, 2014 9:15 pm

I was just starting to do some research with traction brackets and I saw this! Great info! I was reading PBM's write up on their style traction brackets, a lot more fab work. Might just pick up some T3's to mate up with my battle version lower control arms for now.
So in theory a watts link in combination with equal length upper and lower control arms is best?
Image

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Re: Traction Brackets...

Postby jondee86 » Tue Jul 22, 2014 2:38 am

I'm guessing you are talking about this product ?

Image
http://www.partsshopmax.com/e107_plugins/forum/forum_viewtopic.php?10277.0

Certainly looks sturdy enough, and they go to a lot of trouble to make sure
the brackets are nice and firm, so no movement once they are torqued up.

Equal length upper and lower links mean that as the rear axle housing moves
up and down, the pinion angle does not change. Your pinion bearings and
universal joints will like you for this :) A Watts linkage means that there is
no sideways movement of the axle housing as the suspension moves thru
its travel. Both of these modifications require welding and fabrication skills,
and neither is really justifiable on anything less than a full-on competition
car.

The combination that I was referring to above, comprises this...

Image

... hotrod style lower link/ladder bar plus a Watts linkage. This does away
with the top links to create a three-link rear end without having to cut any
holes in the back seat area. You could use these links with a lateral bar if
you wanted to keep things simple. JSP version...

Image

When you have four trailing links and a lateral bar (panhard rod), you don't
have a lot of problems if the axle housing movement is restricted by stiff
springs and short shocks. But if you have a lot of vertical movement and
soft springs, you can get binding. Under hard cornering when there is a lot
of body lean, one end of the axle is down and the other end is up. Because
the AE86 has unequal length trailing links, the axle housing rotates as the
suspension moves up and down. When the car leans, one end of the axle
housing wants to rotate more or less than the other end :o :?

Bit of a mind phuck, but the end result is that the suspension can kind of
lock up and behave strangely until the car levels out and the links unwind.
Downside is that the forces involved are strong enough to eventually tear
the link mounting brackets off the sheetmetal they are welded to on the
chassis. More of a problem for rally guys who need a lot of suspension travel
and use softer springs. That is why they are more likely to weld in the traction
boxes and use equal length links.

Cheers... jondee86
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Re: Traction Brackets...

Postby hachirokkos » Fri Jan 15, 2016 7:28 am

So ? Traction bracket will help eliminate axle tramp/ wheel hop ?

I have brutal wheel hop when accelerating, to exit the corner

I am driving, a trueno, in track @ local time attack championship

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Re: Traction Brackets...

Postby jondee86 » Fri Jan 15, 2016 2:21 pm

hachirokkos wrote:So ? Traction bracket will help eliminate axle tramp/ wheel hop ?

Axle tramp in an AE86 is due to the rear axle housing having some degree
of freedom to rotate forward and back in relation to the chassis. The usual
cause is worn or soft bushings in the trailing arm links. The usual cure is to
fit hard rubber bushings (TRD) or to replace the rubber bushings with harder
polyurethane bushings (Prothane etc).

For a dedicated race car the ultimate setup is to replace the factory trailing
links with adjustable links that have spherical bearings at both ends (T3 etc).

The installation of traction brackets is complementary to any of the above.
By correcting the suspension geometry on a lowered car, the tires will have
better traction under acceleration.
And this is the real reason for installing
traction brackets... not as a cure for sloppy bushings.

There are other factors that affect the tendency of a car to wheel hop. Tyre
grip. tyre stiffness, shock absorbers, spring rates and power to the ground,
wheel speed, road surface roughness etc. If your car is severely lowered, you
should have adjustable trailing links with either hard urethans bushings or
sperical bearings, and traction brackets.

Cheers... jondee86
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Re: Traction Brackets...

Postby hachirokkos » Fri Jan 15, 2016 2:35 pm

jondee86 wrote:
hachirokkos wrote:So ? Traction bracket will help eliminate axle tramp/ wheel hop ?

Axle tramp in an AE86 is due to the rear axle housing having some degree
of freedom to rotate forward and back in relation to the chassis. The usual
cause is worn or soft bushings in the trailing arm links. The usual cure is to
fit hard rubber bushings (TRD) or to replace the rubber bushings with harder
polyurethane bushings (Prothane etc).

For a dedicated race car the ultimate setup is to replace the factory trailing
links with adjustable links that have spherical bearings at both ends (T3 etc).

The installation of traction brackets is complementary to any of the above.
By correcting the suspension geometry on a lowered car, the tires will have
better traction under acceleration.
And this is the real reason for installing
traction brackets... not as a cure for sloppy bushings.

There are other factors that affect the tendency of a car to wheel hop. Tyre
grip. tyre stiffness, shock absorbers, spring rates and power to the ground,
wheel speed, road surface roughness etc. If your car is severely lowered, you
should have adjustable trailing links with either hard urethans bushings or
sperical bearings, and traction brackets.

Cheers... jondee86


I already have polyurethane bushings, on oem links.

I have ordered already traction brackets.
Do you think i should get adjustable links ?
I personally see no reason since my bushings are good in health, and good brand. But, if new links are a must i will order some

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Re: Traction Brackets...

Postby jondee86 » Fri Jan 15, 2016 4:14 pm

Because there are a number of factors that can affect the onset of
wheel hop, it is better to change one thing at a time and see if there
is any improvement in the problem. Fit the traction brackets and test.

Check the bushes when you fit the brackets, as urethane can break up
(disintegrate) under severe conditions, and this is not always obvious
from the outside.

Cheers... jondee86

PS: Since wheel hop is the result of the tyres losing traction, I assume
that you also get hop during hard acceleration from a standing start ?
Not just when exiting corners ?
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Re: Traction Brackets...

Postby hachirokkos » Sat Jan 16, 2016 4:10 pm

jondee86 wrote:Because there are a number of factors that can affect the onset of
wheel hop, it is better to change one thing at a time and see if there
is any improvement in the problem. Fit the traction brackets and test.

Check the bushes when you fit the brackets, as urethane can break up
(disintegrate) under severe conditions, and this is not always obvious
from the outside.

Cheers... jondee86

PS: Since wheel hop is the result of the tyres losing traction, I assume
that you also get hop during hard acceleration from a standing start ?
Not just when exiting corners ?

I will. Thanks mate, and i will come back to you.

I can not answer your final questions, beacause i did not try those.

I will come back to you

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