Best shocks for track use?

[Rock3400]

I'm looking for new shocks to put in my Amp (which is basically a Circuit now) for off road carpet track use. I'm debating between ECX Aluminum, Traxxas big bore, and Hot Racing aluminum shocks. The track doesn't have any massive jumps, and has small bumps in it if that helps.

 

[sc302]

It won't be the shock as much as the oil Weight. Maybe a 30 or lighter.

 

[i_r_beej]

I'm documented the conversion of my AMP MT to race-worthy Circuit >here<

I've used both ECX aluminum and Traxxas Big Bore. My problem with the ECX shocks is that the shaft seal has no spacer so there's not much support of the shaft to keep it from torquing. Observing the action of the shocks, I noticed that the shaft would first torque upwards under load and THEN begin to travel into the shock body. The Traxxas Big Bores are much nicer and also smoother.

I am still tuning my Circuit for the track (it just competed in its first race- astroturf) and right now I'm using 30wt oil front and rear with Losi orange springs in the front (2.9 rate) and yellow springs in the back (2.0 rate). Still not super happy with the response of the rear suspension. (I'm used to buggies.)

But Traxxas Big Bores with Losi springs is a good setup.

 

[i_r_beej]

Traxxas part numbers: #2661 X-long (front) and #2662 XX-long (rear). Or you can buy the set #5862 which is composed of 2661, 2662, and the progressive springs (which are really too stiff for the AMP/Circuit).

I've found that the "buggy" (2") springs will work just fine on the 2661 Big Bores, you'll just need to use a pre-load clip to remove play (and add more clips to add pre-load, if desired).

Here's the list of Losi springs that work with the Big Bores:
Losi Part #
5128 2" Spring 2.5 Rate (Red)
5129 2" Spring 2.9 Rate (Orange)
5130 2" Spring 3.2 Rate (Silver)
5132 2" Spring 3.5 Rate (Green)
5134 2" Spring 3.8 Rate (Blue)

REAR BUGGY & TRUCK (front and rear) SPRINGS
Losi Part #
5144 2.75" Spring 1.4 rate (Gold)
5146 2.75" Spring 1.6 Rate (gray)
5147 2.75" Spring 1.8 Rate (White)
5148 2.75" Spring 2.0 Rate (Yellow)
5150 2.5" Spring 2.3 Rate (Pink)
5152 2.5" Spring 2.6 Rate (Red)
5154 2.5" Spring 2.9 Rate (Orange)
5156 2.5" Spring 3.4 Rate (Silver)
5158 2.5" Spring 3.7 Rate (Green)
5160 2.5" Spring 4.1 Rate (Blue)

Unfortunately these are out of production so you may have difficulty finding them at your LHS. Check around. Then maybe hit Ebay.

 

[Rock3400]

Thanks man, your build is awesome! I'm looking to do a similar build on mine. I know people put weight in the front of their circuit to get some droop, but what do people actually use for weights?

 

[i_r_beej]

I use "Core RC" brand weights. They have adhesive backs and come in 10 and 5 gram weights. If you ever need to reposition them just peel up and remove the adhesive backing (takes some work!) and apply a square of servo tape. You can also find bars of weights at your hobby store. They're scored to easily snap in to smaller segments. You'll need to apply servo tape to one side. I think Du-Bro is a common brand (i think they're used to weight airplanes).

I placed two 5g weights on either side of the central rib just under the bellcranks and two 10g weights just forward of the servo. That's a total of 30g right now. I'm going to reposition the two 10g weights so I can add a third 10g weight for a total of 40g. I've seen other racers stick the weights to the top of the servo. Sometimes people will cut sheets of brass to fit within the chassis. But the Core RC weights (and similar products from ProTek) are the most convenient.

With soft springs (Losi red or orange) I get a decent sag- the suspension arms are level/horizontal with the ground.

Technically speaking, "droop" is the amount of downtravel of the suspension past the "ride height." "Sag" is the compression, under the car's weight, of the suspension. The resulting height of the chassis above the ground/track/road is "ride height."