Just wondering....Looking at the Avante and Egress

[TamiyaBB]

Hi all,

I was looking at the Avante and Egress (pictures, because I don't own one of them) and I asked myself why the setup at the rear is not used on other models. I mean the L-shaped rear arms.

I've read that the Avante is fragile and Tamiya improved this on the Egress. Is the Egress a good runner and when you compare it with the Top Force, which uses normal rear arms. What is the better setup? And why is the rear setup used on the Avante and Egress not used on 2wd buggy's?

Just wondering...

[Saito2]

I've wondered this too. Back around when these cars were new, Team Losi launched the first JR-X2 which featured a five link rear setup very similar to the Avante/Egress three link arrangement. Losi soon offered a way to retrofit "H-Arms" (standard lower control arms) in place of the 5-link deal. Their next car, the JRX-Pro came with these stock. I vaguely remember Gil Losi saying something to the effect that the standard lower control arms kept the chassis flatter in the turns but I could be mis-remembering as that interview was from '90. I do know that the trailing link design of all these cars seems to cope better with rough and choppy terrain, something that also gave the old Kyosho/Cox Scorpion an edge in the early days.

[Nitomor]

Vajra has similar setup too, I believe this is closer to the Egress but I can't confirm as I'm not overly familiar with the Egress, looks like an effective setup, the plastic will allow a fair amount of give too...

[Saito2]

Yes, the Vajra, Egress, Vanquish and Avante 2001 all had the same plastic three link setup. The Avante's was/is the same design but incorporates metal pivot ball ends. In the original Avante, the threaded portion these ball ends attached to could bend in competition. That, along with the extra weight led Tamiya to replace the assembly with the stronger (but less exotic-looking) and lighter one piece plastic part on the following models based on this design.

[TamiyaBB]

I didn't know the Vajra had the same setup...nice to know..

I gues it will work on a 2wd in case off the Scorpion....interesting...

[94eg!]

Just to clarify:

The front suspension of the original Avante was designed to flex backwards with impacts. The rear end was not. The rear's multi-piece lower arm allowed for the slight adjustment of either wheel-base or possibly toe-angle though it was never explained in the manual HOW this was supposed to be done.

On the subject of...

What you guys are talking about is a "trailing arm" or "trailing link" rear suspension. These suspensions were all phased out because they do not offer any benefit over a standard double wishbone suspension. As trailing link suspension moves through it's arc of motion, the trailing link forces the rear upright to move fore and aft. When the trailing link is parallel to the ground, the upright is as far aft as it will go. In the case of the Avante series, the lower arm (trailing link) is perfectly in line with the driveshaft. As a general rule, buggies should always be setup so the ride height puts the driveshafts parallel to the ground. That means a proper suspension setup ALSO puts the lower arm at or near parallel with the ground. This means that every time you hit a bump, the suspension must compress not only upward, but forward too. This is what is known as negative anti-squat. The drivetrain actually begins fighting the compression of the suspension causing the rear tire to loose traction. It makes the rear end of the car less forgiving (twitchy) over bumps.

Now you can sort of compensate for the negative anti-squat by raising the front mount of the lower arm (or lower the rear) at the chassis.....but at some point the trailing link suspension design will always pull the upgright forward through it's motion.

Additionally the Avante's trailing link causes the rear to toe-out as the suspension moves away from parallel. This means under braking AND under acceleration, the rear end geometry becomes less stable.

Now perhaps we can understand why even the TRF racers that used the Egress switched to a more typical double-wishbone setup (see Jamie Booth's Egress).