During some recent side by side comparative testing between the Heng Long Abrams, T90 and Challenger 2 I broke one of the suspension "limiters" on my Abrams. As seen here the #4 road wheel on the right side hanging down below the other wheels.
At first I thought to simply replace it and continue the test but it appeared to not be causing any issues and went on to complete the testing broken. During this though I kept an eye on it and noticed it was working to help tension the track as the Abrams suspension would flex and were the track would usually become rather floppy/loose this was now greatly reduced.

So this lead me to think the very dangerous "WHAT IF" thoughts, the kind that usually create more problems than solutions. Since I was planning on swapping out the suspension arms for metal ones anyway, way not see what happens if I remove ALL the "limiters" (the nub shown below). Will this give the Abrams greater suspension/wheel travel both up and down and in doing so will it also act to automatically tension the track?
So I removed all the "limiters" and upon attempting to run the Abrams discovered a bit more work than simply removing them was going to be needed. No "limiters" even with the spring set at the low tension point, cause a fair amount of unexpected "lift" to occur and the tank looked more akin to a monster truck. So I had to find a sweet point that would provide greater down travel but not a huge amount of lift. I found this point was ~1/3" (7mm) past the factory stop point show in the below photo. I then added some small screws just forward of each control arms to act as the new down travel limiters (note: The plastic control arms seen on the Abrams have a metal "C" sleeve attached. These are not part of this modification).
Once I set the down travel stops and began to run the tank making small adjustment to the spring rates (using the factory spring rate wholes) I found that it went from being a "Burt" to a "Monster". The overland high speed, rough terrain, overall obstacle handling performance and track tensioning was greatly improved. Giving the Abrams a much smoother flatter ride and superb road wheel travel allowing it to make more efficient use of the spring rates and conform its suspension more effectively to the terrain. It also provided for a small amount of lift ~ 1/4" (5mm) giving the Abrams better ground clearance that is now on par with the Heng Long Challenger 2. This does of course mean the Abrams has a slightly different stance/look as seen here during the test of this suspension modification






At this point I have a fair number of hours running this suspension modification and other than me pushing the Abrams far beyond what I did in the past (which was crazy then) I have had no issue except for loosing a track. Was / is this a worth while suspension modification experiment? For me YES, as my focus comes from the old Jeepers saying of "flexablity equals mobility" which the Abrams now has more of. Thus terrain handling performance, durability, reliability and scale top end speed show marked improvements in all areas, making an already fun to drive tank even more fun. The only down side I can see for some people is the overall stance of the Abrams is slightly higher and "not accurate". Its stance now is more like the Heng long Leopard 2 and Challenger 2. I don't mind it at all, it does provide for a more aggressive looking tank IMHO.

I plan on running this modified Abrams during my next side by side comparative test course "Battlefield Debris", were I will once again be pitting the Abrams, T90 and Challenger 2 against several additions to my prior test course. This should be posted within the next week.

As always your constructive input or questions are welcome.

That is interesting and very cool.

I got a chance to take my Abrams out and do this today. Went through some pretty rough terrain and didnt get it stuck but did slip traction a little, plastic track not gripping.
i found the left track continues to throw on the sprocket. Really dissapointed that i couldnt drive a couple minutes without it coming off, mostly in left turns. Pretty much makes it un useable for battling.
also broke off the picture frame on the rear of the engine and the coaxial mg barrel dissappeared as it was not glued.
i wonder if the metal tracks would stay on better.

Did you add new down travel stop points limiters? I found this very important to do. If not the suspension will over travel and cause issues like the one you discribe and worst. The plastic track might have to much tension for this mod unless you add an additional link. I did not test my plastic track as it was tight to begin with when I was running it and would only be tighter with this mod. I run my Abrams exclusively now with metal/rubber padded tracks and a metal sprockets with a track retainer rings.

Also it is important to set the spring rates correctly. This will work to tension the track with this mod. I run the #1 #6 and #7 road wheels at the heavy settings. This works well for my track type, sprocket and overall tank weight.

Lastly I found that with the Heng Long Abrams it is important that the #1, #7 road wheels, suspension arms and sprocket have as little wiggle or play as possible to ensure the best track retention (especially if one is going to run their Abrams hard and fast). If these wiggle or have a lot of play it will only exaggerate issues with detracting. Mine have added supports and shims to help keep things tight and aligned. Hope these additional thoughts help with tuning the your suspension. I had to discover all this for myself as there is very little information on the Heng Long Abrams out there in this area, aside from simply adding aftermarket metal parts that half the time still need "tuning" to work well (I have a buck load of these types of parts, almost all failed to provide much in the way of performance and reliability improvements).

On loosing the rear "picture frame" LOL! It just means you were driving your Abrams hard. I ripped mine off at some point long ago. Did not even bother to put it on my second Abrams. Notice it is missing in the photos below.

When everything is set correctly you should see reliable performance doing high and low speed hard turns and crossing terrain like seen below from my upcoming comparison review of the Abrams, T90 and Challenger 2 on my "Battlefield Debris" course.

Mine is all stock save better motors. The left track that keeps coming off is looser than the right which does not detrack on the sprocket. Basically it's too loose. What is needed is an adjustable idler wheel up front to maintain tension on the track at the sprocket.
i am not aware how to change the spring load on the wheels?
I really didn't want to to get very involved with this tank as I just wanted one modern tank for modern battles. Sherman's are my passion, the Abrams was supposed to be fun and fast with little work. I don't plan to upgrade or rebuild this thing.

Two thing that worked for me when I was running plastic track on my Abrams. The drive shaft hull support bearings and a metal sprocket with track retainer rings. Both I purchased from Tucanhobbys (spelled something like that) for under $25 combined including delivered from HK.

Those matched to some “RED” HL motors (390s) an 8.4v battery pack internally mounted in forward hull and you should have a scale top speeed of 40ish + mph. Been running this voltage since day one in all my tanks with never an issue. Also mounting the battery more forward in the hull helps with balancing the weight which in turn reduces the noise bouncing while at higher cross country speeds. If you want to smooth out the cross country “noise bounce” even more just add some additional internal weights to the noise. The Abrams has a huge hull that lend itself to endless tuning possibilities and larger battery options.

The spring rates can be increased by simply switching to the second spring attachment hole. If memory serves it is the lower hole that increases spring rates by increasing the amount they bend and twist. On an all plastic Abrams with no added internal weight you will end up with a very bouncy tank if you reset more than the #1 and #7 road wheels to the heavier rate.

There is also a so a simple, cheap and fast solution to the wobbly road wheels but for that I would ask you to PM me as I was planing to do a write up later on that topic in a separate thread.

A friend saw my post and called me and reccomended the sprocket with the center guide channel. Got a set on evilbay.
i also think the hollow back side of the track allows the teeth to sink into the hollow area thereby allowing the sprocket to grab and off track. Whereas id the rear were solid and not open, the sprocket teeth would not be able to sink in and grab and the track might not slip off especially with a center guide.
funy, i didnt even know real abrams have a center guide on the sprocket. Ive never paid attention to that detail when I have been close to them.