ECX Boost with Associated B4.2 steering components

i_r_beej

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Recently I've been really frustrated with the shoulder screws falling out of the caster blocks. I've been running the RPM replacements for the stock ECX parts, and while they are nicer and "stronger" they still suffer from the fundamental ECX design flaw of very shallow holes for the shoulder screws to thread into.

In looking for an alternative (I'm not crazy about aluminum parts in my steering assemblies) I discovered that some Associated B4 (specifically B4.2/T4.2) steering components are compatible with the 2WD ECX vehicles (Boost, Circuit, AMP for sure; maybe Ruckus and Torment). The Associated design uses a kingpin that slides completely through the spindle block and caster block and appears to be a much more reliable, stronger design. (I hope!)

I found a complete set of caster blocks, spindle blocks, bearings, ball studs--everything--on Ebay so I decided to give it a try. The parts arrived early so I decided to test one side. (I'll perform the complete the installation later.)

It looks like this modification will be a success! The Associated parts fit right in with NO problem! The Associated design uses a narrower caster block so that you can tweak the wheelbase of the car a few millimeters by inserting a spacer in front or behind the caster block. The stock Associated spacer is about 6mm and the ECX A-arm is not wide enough to accommodate it but I did have 3mm nylon spacers on hand (or I would have just sanded down the Associated spacer).

Here's the stock ECX steering components (left) compared to the Associated B4.2 components. Geometries appear to be identical with the exception of the position of the spindle in the spindle block. The ECX is "in-line" whereas the Associated is off-set or "trailing." (Apparently a trailing steering arrangement makes for easier handling at speed and is better for high-grip conditions. This is the stock, out-of-the-box configuration for the Associated B4.2/T4.2)
ecx-boost-associated-b4-steering-1.jpg

Here's the Associated B4.2 caster and spindle blocks installed in the ECX A-arm. Everything fits snugly, with no binding. Like they were made for each other! Interestingly the camber link ballstud is locked in place with a nut, instead of just threading into the plastic.
ecx-boost-associated-b4-steering-2.jpg

And here's the underside, showing the white nylon spacer in place. In the Associated B4.2 documentation it's recommended to put the spacer behind the off-set/trailing spindle block. Even with the space in place it looks like I will be shortening my ECX Boost's wheelbase by a few millimeters. This will probably not affect in any appreciable way. (And look at that! The steering link ballstud is anchored with a nut! Nice.)
ecx-boost-associated-b4-steering-3.jpg

I DO have a few minor hurdles to clear before I can get rolling on these new Associate parts. The spindle is not a metric diameter so I will need to get Associated hexes. The hex pin is a different, smaller diameter so none of the pins i have on-hand will fit. I will also need new axle nuts. I plan on taking my car to the LHS and checking out what they have. And finally I'll need a new hex key to remove/install the small screw that captures the kingpin.

I'll update this post with additional information and photos when I perform the complete installation.
 
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That does look like a much better design. Thanks for the writeup. Do the arms come the same distance inwards? Or will you need adjustable turnbuckles?
 
That's a good question and I'll address it in my full write-up. At first glance the ECX and Associated B4.2 spindle blocks look to be dimensionally identical. But they could be off slightly. I'll have to buy RPM's toe gauge to be absolutely sure.
 
Picking up this thread again. (Work has been crazy.)

I've installed the Associated B4.2 camber and spindle carriers on both sides. The arm of the spindle carrier/steering knuckle IS a little shorter than the stock ECX spindle carrier (or the RPM replacement). So once I reconnected the steering links, the car had 2-3 degrees of toe out. I made an adjustment by eye, turning each steering turnbuckle the same amount and go the front wheels to 1-2 degrees toe in.

NOTE: Measure the distance between the front edge of the front wheels before performing this modification, so you know how much you need to adjust to get your car's steering turbuckles!

I hit the track the next day and the car ran well! Despite the steering axis now being a couple of millimeters trailing I didn't notice much difference in how the car handled. If anything the steering seemed a little easier, less "twitchy."

So lost shoulder screws will not longer be a problem. However, since the B4.2 uses an SAE spec thread, I had to buy some 8-32 nuts. So now I require two wrenches to remove the wheels on my car.

In the end, this was a fun experiment, especially considering that the Associated parts fit almost perfectly with no cutting, drilling, or even sanding needed. But I think buying the ECX or Hot Racing aluminum spindle carriers and applying blue thread lock to the shoulder screws is an easier (and better!) solution to the problem of shoulder screws backing out of the spindle carriers.
 
For the record, here is a list of parts in the assembly that I installed:

Team Associated par numbers:
9880 steering block, hex style
6277 ballstud (short)
4449 4-40 locknut
3977 ball bearing 3/16" x 3/8"
7496 B4 front axle, hex
7369 1/16" universal roll pin
7497 Hex adapter (12mm, you could probably use any similar hex adapter)
9580 caster block
9622 Outer hinge pin
9645 2-56 x 1/8" button head screw
7260 4-40 nut (to secure ballstud on caster block)

The Associated ballstuds on this car are the same diameter as the ECX ballstuds because the RPM heavy duty rod ends that i use for steering and camber links fit without being tight or loose.

I didn't purchase each component separately but was able to find the complete camber/caster block and steering block assembly on Ebay.
 
I still have that component but I never did mount it. I realized that I'd need to mount much shorter shocks and spent some time pricing some Associated shocks from the B4 RTR kit and ultimately decided that it would be "throwing good money after bad." I don't think the car would really derive any benefit and might actually suffer. It was about this time that I found a TLR 22 3.0 kit at a VERY good price and began focusing my time and money on that car.

I did find a video on YouTube (a few years old) in which the user demonstrated their Boost with AE B3 parts but they didn't provide any part numbers or detailed information and the suspension action of the front shocks looked like it was limited and maybe even subject to binding. (In the video, you'll see that when the owner pushed the front of the buggy down, the shocks seem to bottom out before the front of the car does-- not good.)

Here's the video:
 
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*Great Job!! I recently purchased two older Losi XXXt-mf2 models off ebay with a DUMP LOAD of spares(so I could put together a vehicle for the wife). These models were obviously indoor only raced with a ton of extras and very AFFORDABLE.
**I was able to use brand new spares of Titanium Turn Buckles/Losi Rod Ends, and Lunsford Titanium Ball Studs(.375)....to replace all of the steering and camber links on my ECX Ruckus 2wd.(I even was able to swap the Losi XXXT shocks over with a set of highlighter yellow springs of unknown origin that work great)
***A huge improvement over stock!!
 
I tried a B4 front shock tower on my Boost and it bolted right on, but I only tried it with the team associated shocks. I'm not sure how it would work with the stock Boost shocks. The B4 tower is much shorter.
 
These are Originlal 2002 matt francis Losi XXXt-mf2 aluminium threded body front shocks.
-I am going to give you the center to center(of mounting holes) over-all length of the fully threaded adjustable Losi XXXT-mf2 front shocks first, **3.530"**
-Next you will want to know the travel of the shock...**1.485"**
-You probably also want to know how long the upper threaded(fluid portion) of the shock body is...**2.275"**
>>My first measurement I provided is on the small side/a touch off...(I am measuring off the model as installed)
 
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@jbalsamo23 were you able to get full travel with the AE shocks? Meaning, did the font end of the car bottom out before the shocks did?[/QUO



Yes, they were b4.2 big bore shocks, they were nice but on loan from a factory team car, I couldn't see a big enough difference to make that big of an investment
 

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