[QUOTE]
Quote Originally Posted by string View Post
I think these arms are marketed at those with higher than usual power who are susceptible to wheel hop or torque steer.
Not sure how much "higher than usual is", for circuit racing we are looking at around 300 bhp and 220 ft lbs of torque running N/A on E85. That's around double the standard power output, but of course nowwhere near the 700 + bhp the drag guys are extracting forced induction and methanol.

All I can say is with bush upgrades and caster kits running R type tyres, we don't see any wheel hop or torque steer.



Maintaining longitudinal position helps maintain toe. Allowing the upright to move forward will pull the tie-rod forward, toeing out the wheel. The "traction bar" virtually eliminates this factor.
But it does nothing for the upper control arm. That's why we replace the rubber bushes in the upper control arm with polyurethane as well.


The new constraints on the suspension geometry will offer lateral compliance advantages in two ways:
1) An applied pure lateral force at the lower ball joint must partially pass through the radius rod linkage since the radius rods are not perpendicular to the control arm. The angle is quite small (20 degrees conservative approximation) so it's aid will be less than 10%.
It is also mounted inboard, at the shock mount.

2) The resultant force on the two-piece (effectively a rigid body) LCA can now never be purely lateral, it must always be perpendicular to the radius rod. Now you have the compliance bushing helping in a purely lateral force (which without the radius rod, could potentially load solely the inner LCA bushing).
There are 4 bushes involved, the lower control arm inner, the lower control arm rear and the 2 upper control arm bushes.




The benefits above will be enhanced the closer the applied force is to parallel with the radius rod (engine power).
Not quite as the driveshaft is mounted above the lower control arm. As is the steering arm.


The radius rods will have the least (zero) effect when the applied force is exactly perpendicular to the radius rod (i.e. the applied force is not at all constrained by the radius rod).
Exactly, that's why they are of zero use in controlling camber.


Without any data on the relative strengths of the compliance bushing and the inner LCA bushing, it's impossible to give any real numbers. Suffice to say, the effects on lateral compliance and therefore camber compliance, are an infinite times more than nothing.
You lost me. The aftermarket traction rod would allow horizontal and verticle rotation around its attachment point to the lower control arm. Any bush compliance, and there is a lot in the standard rubber bushes when new let alone after 15 years, would result in uncontrolled changes in caster, camber and toe.

My opinion, as stated above, is that the traction rod kit is pretty much wortheless unless you are drag racing and even then I would argue that there are better methods that would achieve a superior result.

So why are they made and sold? It's got more to do with the Japanese market than pure engineering. So it is worthwhile investigating the reason behind that market. Japanese workshops charge upwards of $500 per hour for mechanic’s time. That’s why Japanese aftermarket parts supplies sell 100% complete products, that come with every nut bolt screw and washer necessary, perfect thread, perfect holes etc. The workshop’s customer is not going to be very happy if he buys a $300 part that costs $1500 to fit because the mechanic spent a couple of hours searching for the right fasteners and drilling some holes. This huge disparity in the cost of parts versus the cost of labour means that solutions, to problems such as suspension geometry, have to be bolt on. Quick, easy, simple, in and out of the workshop. Plus they wouldn’t require a wheel alignment, bolt them on and drive out. All up maybe 30 minutes, say, $550 for parts and labour

The problem is this leads to unusual solutions to problems that would be better solved with other methods. Let’s take the upgraded bushes that we would typically apply in Australia where workshops labour rates are more like $80 an hour. The polyurethane bushes to fix this problem would cost less than $250 and take around 2.5 hours to fit. Add the necessary wheel alignment, you should never fit new bushes without one, and all up, say $500, parts and labour.

Technically there is no doubt the “Australian” solution is superior, but it would never happen in Japan, $250 in bushes plus $1500 in labour to fit them is just not going to be accepted by the workshop’s customer.

Personally I would take the opportunity to build in adjustment for caster and camber while I had the front suspension apart for fitting of the bushes. So I would spend and extra $100 to $150 on the bushes and get a far superior solution.

Cheers
Gary