So i’ve had my merv for a while now and found the most interesting and frustrating aspect of it to be the suspension. It took me a while to try out all of the different shocks, springs, oils, rocker configs to understand how it all works. It took quite a while, but i finally found a config that works for me and while Im sure this info may be common knowledge to most of you guys, my hopes is that shareing my learnings may be able to help out those just starting out and make it a little less confusing. It may be overkill, but i kinda wish i knew all this stuff when i started out, i know it would have saved me alot of time and money.
Ill start by saying i drive my car 50/50 on the street and on grass/dirt. What ive found is a suspension setup that really works for this hybrid driving. I will list my config at the end but for now heres some of what i learnt. You might disagree and thats fine, again this is all my personal experience.
First off, The biggest mistake i made when starting out is how much i cared about how much the suspension there was when i push the car down at rest. I would always want the most amount of suspension, as i thought that was the way to go, ie. “wow look at all that suspension!’ . What i learnt is what you should be concerned about is the opposite. You really want the most amount of suspension travel when you PICK UP the car from rest. What that does is it lets the car stay level when you drive over potholes or divots in the grass as the suspension arm will dip into the hole and the chassis will remain level. Since You are never going to be going full speed over a huge rock, it doesn’t really matter how much ‘push down’ suspension there is. The only reason you should be concerned about how much ‘push down’ travel there l is if you want to raise your ride height. The more push down travel you have, the higher your car will be off the ground.
I find if you keep the drive shafts a bit higher than horizontal at rest, thats the best bet. So you push your car down and when it rebounds, have the shafts raise just over horizontal. And when you pick the car up, you really want the springs to expand 75% of way out. The more ‘pick up’ travel you have also allows you your car to survive much bigger jumps as the shocks will expand 100% on a jump, so you have that 75% to soak it up when it lands. This is all accomplished via the shock preloads. The looser the preloads, the more ‘pickup’ travel youll have. The higher your preloads the more ‘pushdown’ travel youll have. Of course this is done the same with looser and stiffer springs
Rebound speed. So i used to care about how fast or slow the car rebounded when i pushed it down and how fast/slow it took to return. I always thought slow was better than fast, but really its trivial. What you do need to care about is how SMOOTH the car rebounds. You want to make sure that the car rebounds in a such a manner that it doesn’t jerk up right away: That means your springs are too stiff. Or if your car doesnt rebound at all or takes a while to return: that means your springs are too loose. This is the hardest part i found of shock tuning, because the smoothness of the return is all based on the spring and oil combo you use. What makes it even harder is that there is no common or universal combo to go with because its all based on how heavy your chassis is. all chassis will have a different weight, some run 1 battery, some run 2. I will tell you my config later, but all i can say is its all trial and error. Of course the basic guideline is that the heavier oil you use, the stiffer spring you need, which is true. But i found when you have the shock removed from the car and you compress it, you want it to be a smooth expansion. Not slow, and not fast, just smooth
Along these lines, i learnt that you need heavier oil and stiffer springs in the rear. I think it says this in the manual, but i found out its not just because there is more ‘stuff’ in the rear (motor, wing etc) but i hated the way my car ‘squatted’ when i gave it throttle. To fix this, not only do you use stiffer springs, but the preload should also be higher in the back, and what you want to see is when you pick up your car from rest, it should be angled in downward slope towards the front. This will also really help when you land your jumps on the rear, the stiffer suspension will help absorb the blow. I learnt this the hard way by snapping a chassis in the rear because my preload in the rear was the same as the front . at rest the slope should not be as severe, you do want it a tad higher in the back, but when you pick it up with the shocks expanded, it should be.
And here are some of my lessons learned:
- Don’t use the stock suspension setup. Its way too loose for any kind of driving. You risk snapping your chassis if you bash
- Don’t use gpm shocks. They break and the pre load is impossible to adjust
- Get some aluminum shock towers. The plastic ones break, and the tower strength is very a important part of the system
- You want the least amount of preload in your springs possible. if you are preloading past the 1/2 mark on the shock, you need stiffer springs. The more preload you have the more wear on the springs during their life time. Less preload = more compression of the spring which is good
- The sway bars are not necessary. They may help reduce the ‘dog peeing’ stance in a turn, but you lose almost all the individual shock articulation which is a way worse trade off
- You can loosen the rod ends on the push rods which CAN eliminate the ‘bottoming out’ of the car. Meaning you can push the car down all the way, but the chassis will not hit the ground. Im not sure id recommend this as if you take a monster jump, all that energy when you land will be forced onto the shocks and it may not be able to take it. The bottoming out of the chassis helps transfer that energy across the whole car. So imo, you a suspension set up that allows the car to bottom out
- You really need bearings in your rockers and not plastic ones. Other than the wheels, the rockers move the most on the car, so do it a favour and get some bearings.
- I did not like the traxxas black and tan springs. Know they are shorter than the stock springs and require alot more preload than usual. Why they are shorter i have no idea , but they are. Either go with the purple summit springs, or get the 3 spring set in the gpm shocks. Trust me when I say They are by far the best springs out there. I must have like 50 springs in my toolbox, I've tried them all!
So yeah i may have gone on a bit long, but i hope it helps someone out there. If your the person who just likes videos have a look at my setup below. It should give you a visual about how my car rebounds and stuff, which is something ive always wanted to see in other peoples setups. It really works great for me however and i do recommend it to anyone who wants a solid 50/50 setup. I run 2s and sometimes 3s and it holds up. Good luck with yours and feel free to add any feedback or any of your experiences with suspension setups. I use:
- LT rockers. Plastic in the front. Gpm in the back
- Traxxas gtr shocks
- GPM black springs in the front, GPM Silver springs in the back (they come with the gpm shocks)
- 80wt oil all around
- I have 1 small spacer on all my pushrods. this makes my pushrods longer and gets me even more travel
- Bearings in the rockers