Long Travel Buildup

[mass-hole]

Ever since I built my TRX4 Sport kit I have been wanting to fit longer shocks on it in an attempt to get more travel and articulation, while maintaining the stock ride height, COG, and spring rates.



The first link in that chain is the upper shock mounts. There are several mount options out there that allow you to raise the upper shock mount by 10mm relative to the chassis. What this means is you could theoretically run a shock which has a 10mm longer compressed length while maintaining the same ride height and bottom out at the same point but get more travel.



I am not condoning people buy the hot racing shock mounts as the panhard mounts have been known to snap, there are ebay options with double panhard mounts.

The second step is the shocks. I have found two potential options that could work. But first lets talk about the specs on the stock TRX 4 shocks:



Extended Length: 90mm

Compressed Length: 65mm

Travel: 25mm



The first option is the long GTS shocks that come with the Traxxas Long arm lift kit. They are Part # TRA8160 and can be purchase separately from the lift kit:



Extended Length: 110mm

Compressed Length: 75mm

Travel: 35mm

Additional compressed length over stock: 10mm

Additional travel: 10mm or 40%



These actually are pretty perfect as you pick up exactly 10mm in compressed length which is offset by the 10mm taller shock mounts. And they are literally just a longer version of the stock shock so they should fit perfect.



The second option, and what I was going to try because I already own them, is the Hot Racing 120mm TD120RV02. These shocks are dual-rate shocks and for some reason offer a lot of travel for their size:



Extended Length: 120mm

Compressed Length: 77mm(!)

Travel: 43mm

Additional Compressed length: 12mm

Additional Travel: 18mm or 72%(!)



These shocks are not quite as perfect since they are 12mm longer compressed but close enough. The offer huge travel in a relatively small package.



Now for the pictures. I put a new shock mount and the Hot Racing shock on the left side of the rear axle and kept the right side stock. First up is the truck sitting at ride height after cycling the suspension. You can see its sitting level despite the left shock being 30mm longer overall:

Here is the shocks at full compression, again, level because the additional shock tower height compensates for the longer shock:

Here is the rear axle hanging with both shocks at full droop. This is where the difference lies:

Here is the articulation available(we assume the stock shock is a standing for the HR shock since they bottom out at the same point):

Here is stock articulation:

Last but not least, the stock TRX4 springs fit the HR shocks:

This means you could run the springs for the longer TRA8160 shocks on these hot racing shocks which should solve any spring rate issues you might run into.



I know someone is gunna say that travel is bad. What about side-hilling?! What about climbing?! I fail to see how that is an issue. If you run the same ride height and COG while maintaining the same spring rate and bottom out point, how can either of these be affected substantially? Maybe in some odd scenario the extra shock length could allow the tire to push off the ground where the stock shock might have reached full extension causing the tire to leave the ground instead?



I guess I would rather have more droop and flex to allow the tires to stay in contact. Imagine high centering on a rock where the stock shocks are hanging in the air and your tires arnt grabbing. Now imagine you tires can drop 18mm father down and are now touching the ground and have some bite to pull you through.



Worst case is I can experiment and see what happens. I already own the shocks and the towers were cheap. I may but a set of the springs for the longer GTS shocks and put them on my HR shocks and see how that works.

 

[durok]

The test will be in the driving, my man!

Very well explained and photographed documentation of why to try this out.

I'm looking forward to hearing your driving impressions - and maybe a video???

 

[Inspector86]

I'm doing a similar experiment but only on the rear. Instead of the HR mounts, I used the GRC rear axle end mounts which have 5 shock mount locations and also move the bottom end of the shock outboard. Using a pair of the long GTS shocks on the rear with the stock length GTS shocks up front has given me just a little more articulation without changing ride height, COG or being floppy. The nice part is that I can use the same springs on both shocks.

 

[alexleblanc]

i'm looking forward to seeing how well it sidehills compared to the stock setup.

 

[JC3]

Very impressive experiment. Thanks for the outstanding documentation. I like your reasoning regarding high centering, makes perfect sense to me. Looking forward to you test drive results!

 

[mass-hole]

I'm doing a similar experiment but only on the rear. Instead of the HR mounts, I used the GRC rear axle end mounts which have 5 shock mount locations and also move the bottom end of the shock outboard. Using a pair of the long GTS shocks on the rear with the stock length GTS shocks up front has given me just a little more articulation without changing ride height, COG or being floppy. The nice part is that I can use the same springs on both shocks.

Those GRC mounts are cool for sure. I wouldnt mind getting some but i am trying to restrain myself on the upgrades and take it ones step at a time.

Why is it that Traxxas specs stiffer springs on the rear of the TRX? I weighed my truck and the front end is heavier. Is it for climbing? Ive noticed that when i am going downhill off of ledges that the truck is a lot more prone to rolling than going up and i wonder if this is part of it.

 

[mass-hole]

Getting the springs right has been a little bit of an issue for me. To take up the full 43mm travel of the 120mm HR shock I am requiring that the stock TRX4 springs go under too much compression and it doesn't fully settle at stock ride height. I decide against going with the long GTS springs because they don't offer them in lower spring rates. The Sport Kit comes with white springs in the front and orange springs in the rear. Here are the options available from Traxxas:

So if I went to the long GTS springs, the minimum spring rate is .47 which is what comes on the Defender. I would have to increase the spring rate at the same time as the length, and I dont know if that would work on the lighter sport. The sport is 1.6 lbs lighter than the Defender according to Traxxas. I weighed mine with a battery and it was 6 lb - 10 oz.



So instead I bought the fluffier .22 yellow normal length springs. I will run those on the front and run the stock front whites on the rear. This will hopefully let the truck settle a little lower in the travel and be where I want it.

 

[JC3]

Those GRC mounts are cool for sure. I wouldnt mind getting some but i am trying to restrain myself on the upgrades and take it ones step at a time.

Why is it that Traxxas specs stiffer springs on the rear of the TRX? I weighed my truck and the front end is heavier. Is it for climbing? Ive noticed that when i am going downhill off of ledges that the truck is a lot more prone to rolling that going up and i wonder if this is part of it.

I thought that this was for the same reason that firmer foams are recommended on the rear, that is, to prevent rear weight transfer when going up very steep inclines.

 

[JC3]

Have you had a chance to do any testing?

 

[mass-hole]

Have you had a chance to do any testing?

No, I was down in Houston for work starting last sunday through last night, so no chance to look. I gotta fly to MA on Monday morning so It may be a little while.

 

[mass-hole]

Just wanted to post that i finally got around to getting everything installed(and the body finally painted) but havent driven it much. I had two 110mm shocks and two 120mm shocks so input the 110’s in the front:

The truck is sitting just slightly high in the rear. The front was at the same height as stock so i cranked the the springs up a little.

One thing to point out, the natural droop of the suspension linkage is shorter in the front:

So 110mm shocks are about all you need in the front. 120mm shocks would not realize their full travel. The rear can make use of the 120s no problem.

I may buy another pair of 110’s and run them in the rear to help bring down the ride a little. Either that or the GRC lower shock mounts.

 

[JC3]

Looking good. Thanks for the update. If these changes translate to improved crawling I might just buy another TRX4 and devote it to this upgrade. Very interested to see the crawling capabilities with the increased travel.

 

[Inspector86]

Those GRC rear axle mounts would allow you to lower the bottom end of the rear shocks while also spreading the lower end outboard to add in some stability and they are less than $10.

https://www.ebay.com/itm/1pair-Alloy-CNC-Rear-Axle-C-Hub-mount-L-R-For-TRX-4-Traxxas-1-10-RC-Crawler-Car/112931470197?ssPageName=STRK%3AMEBIDX%3AIT&var=413318742638&_trksid=p2057872.m2749.l2649

 

[mass-hole]

Looking good. Thanks for the update. If these changes translate to improved crawling I might just buy another TRX4 and devote it to this upgrade. Very interested to see the crawling capabilities with the increased travel.

Im still fighting with the ride height. Stock height without body(ground to the shock tower screw in the frame) was 103mm front, 107mm rear. I can hit 103mm in the front with the 110mm shocks but the 120mm rears are settling at like 112 mm, so like +5mm. It is a little top heavy although some of that might be that i finally painted the body and assembled to expedition rack which is all weight up high.

Trying to decide how to tackle it. I could swap to 110’s in the rear too, or i could get the GRC or GPM c-hubs with the 5 shock mount holes.

 

[mass-hole]

Those GRC rear axle mounts would allow you to lower the bottom end of the rear shocks while also spreading the lower end outboard to add in some stability and they are less than $10.

https://www.ebay.com/itm/1pair-Allo...var=413318742638&_trksid=p2057872.m2749.l2649

Bought these. Thanks for the heads up. Asia Tees was like $20-25

 

[JC3]

I think that the 110's all around is the way to go. I'm saying that because although the rear can accommodate the 120's, the 110's still represent a massive improvement while maintaining the low CG (ride height.) I feel like that CG is just as important as articulation.

 

[mass-hole]

I think that the 110's all around is the way to go. I'm saying that because although the rear can accommodate the 120's, the 110's still represent a massive improvement while maintaining the low CG (ride height.) I feel like that CG is just as important as articulation.

Traxxas just came out with lower rate springs for their long arm shock. It may be just whats needed to run the 120’s at the correct rideheight. I have them coming from amain to try out.

 

[JC3]

That will be interesting to see if they help with ride height. I was looking at my truck and began to wonder if there is a point at which the amount of articulation can become detrimental. I've done a fair amount of crawling and so far as of right now, can't really see why that would be, however I'm still wondering about it. I have heard it mentioned in a thread or two here on the forum.

 

[mass-hole]

That will be interesting to see if they help with ride height. I was looking at my truck and began to wonder if there is a point at which the amount of articulation can become detrimental. I've done a fair amount of crawling and so far as of right now, can't really see why that would be, however I'm still wondering about it. I have heard it mentioned in a thread or two here on the forum.

It probably depends on the terrain. A lot of side hilling and what not might be detrimental, but thats not really what i do. Most of my crawling has been on a rock slide at one of the local trails:

 

[mass-hole]

I finally managed to get out on the rocks and, i gotta say, this thing seems extremely capable on this type of terrain.

I dont know whats the overriding factor, but i can tell you that the tires rarely leave the ground. Its always got 4 points of contact and it just crawls over stuff like a spider. I do think this adds some inherent stability as its not lifting tires and flopping around as weight transfers and it teeters between the three tires in contact like it did stock.

High centering seems like less of an issue and it tends to pull itself through obstacles better. Not sure how much dropping the ride height will hurt this as it is a little higher than stock.