So I decided the stock Summit VXL rear was sagging too much for my liking. Upgrading the springs and shock oil made a HUGE difference in my 1/10 E-Revo. Went into the LHS yesterday and they sold me 1/16 tan and black. But after installing, things got worse!
Come to find out the springs were almost 1/4 inch shorter, being designed for the MERV. On top of that the stock blue have a higher rating. Now I have to wait for the purple ones to be shipped out in February 2011. LHS is giving me a refund until then.
Here is a helpful link for those interested:
There are many posts on this forum about the springs. In my opinion the guys at your local hobby shop are not very knowledgable... They should have known that the summit has different suspension and requires stiffer springs than the merv. And I got my purple springs straight from traxxas, call them up and see what they can do for you.
yeah after not being happy with the stock blue, I went read on here that the purple were the way to go. I also went to the LHS and asked for the purple, They told me that they dont make them. I whipped out the iPhone and went to the fourm and found the part number and have them order it for me. Sometimes I truly wonder if they know RC or a cash register ????
Wouldn't you like to know...
Separately, I know you can change shock oil and springs. how should i think about those. From what I gather the thicker oil wil dampen the play similar to putting on thicker springs, so when should someone change oil weight versus changing springs?
1/16 E-Revo VXL
1/16 Summit VXL
Let's see if I can help to the best of my limited knowledge. While the MERV (1/16 E-Revo) and the 1/16 Summit VXL are built on the same platform, the suspension and gearing are different. This allow for the bigger tires and ground clearance of the Summit, and explains the speed difference of the MERV.
I discovered by mistake, and started this thread as a warning, that the springs for the MERV are 1/4 inch shorter than the Summit VXL. Traxxas coats their springs in red, sort of a trademark. However, the metal used can vary - thus the different "color" springs. The link at the top of this thread takes you to the Traxxas parts store for MERV & Summit springs. A higher rate equals a stiffer spring.
Shock oil thickness determines how quickly the piston can travel through the shaft. Once you take a shock apart, you'll have a better understanding of the mechanics. Basically, inside is a disc with holes in it. These come in different styles too. Either bigger/smaller holes or more/less of them. Ultimately the oil weight, hole size and number determines how fast the piston can plunge or retract through the shock.
Changing just the springs to a stiffer rating will cause the vehicle to be more "bouncy." This is useful if you are driving in rough terrain or jumping. The necessity for a stiffer spring comes from bottoming out. With increased stiffness comes a 'higher center of gravity' for cornering; since the shocks won't absorb much of the body roll. The Summit VXL comes with stock blue springs. My complaint is the back end bottoming out with hard acceleration and with mild jumps, thus my desire for a stiffer rate (purple being the only option from Traxxas.)
Changing just the oil weight affects dampening. From page 21 of the manual "Damping should be increased (with higher viscosity oil) if the model is bottoming easily over jumps. Damping should be decreased (with thinner viscosity oil) if the model is hopping over small bumps and feels unstable."
When to change springs or oil is debatable. Changing the oil is more common, with a thicker oil causing a slower response. In racing conditions, some people use different oil on each side for the track being run. However, a thicker oil puts more internal stress on the shock - thus leading to a 'blown shock' which occurs when they leak. Heavy usage of any weight oil in a shock may lead to blowouts too. Youtube has some nice videos on how to rebuild a shock. Trial and error seems to be the best way to determine your needs.
For my purpose, I'm going to a stiffer spring first, then I'll play with the oil weight. But I've got some really rough terrain to play in.
Thanks really helpful. What do you suggest for my merv and mini summit. So far we've run them around parking lots and out backyard with some small obstacles and jumps (very small maybe a foot) to run over. When it warms up will run at more fields and hopefully some local woods/trails.
1/16 E-Revo VXL
1/16 Summit VXL
A couple of things: my summit VXL came with red springs by default.
Also, I tried to change the spring preload setting (by twisting a nut on top of the spring), this had the effect of increasing the ride height. The truck didn't squat as much during acceleration. But I noticed that I don't have as much directional control during hard acceleration, i.e. steering was not as responsive. Which leads me to think the default setting is not that bad, even though the truck does seem to squat during acceleration. Also, i don't think bottoming out when landing a jump is a big deal. I'd rather have a suspension that handles the small bumps at high speeds (such as the default setup) than one that specifically handles big jumps, I don't think you're really damaging the truck by bottoming out.
Ultimately suspension comes down to keeping the wheels in contact with the ground while providing a more comfortable ride for the passengers. Since RC's don't have passengers, its more about control. Think of a series of speed bumps, one after another. If the vehicle is bouncing around, you can't accelerate or turn if you are airborne half the time. If you keep bottoming out, you have increased friction which will slow you down and potentially cause structural damage (ie loosening screws, jarring spur/pinion gear meshing, fragile electronics, etc.).
Your driving conditions really dictate how you should set the suspension.
A note about increasing the spring preload (as told to me by a hobby shop guy). You ideally want to adjust the preload to 25% from the top. This allows you some play when switching terrain and driving conditions. You can go up (0%/softer) or down (50%/stiffer) easily without having to change oil.
Don't know about the MERV, but the manual says the Summit VXL comes with 60 weight oil. Mine has stock blue shocks. I'm waiting for the purple springs to become available. But will probably try 80 weight oil in the meantime. My Summit seems to ride fairly low, and now my LiPo's are here its going to get beat up alot more!
According to buytraxxas:
Color Rate (stiffness)
Orange 1.76 1/16 Revo
Green 1.92 1/16 Revo
Tan 2.06 1/16 Revo
Black 2.22 1/16 Revo
Pink 2.77 1/16 Summit
Blue 2.925 1/16 Summit (stock (allegedly))
Purple 3.2 1/16 Summit
Hi all. Got my purple springs today and couldn't wait to get them installed.
Trust me. They make a pretty big difference even without changing the oil.
Not squating like before.
So! Not looking like a dog draging its *** in the grass and good terrain handling as well.
Happy SWEDISH mini summit owner.
How about cornering.. I stiffened up my springs and watched my Summit roll over and over and over... i'd like to keep that to more of a minimum.
2011 Traxxas Summit 1/16 VXL - White
When having the stiffer springs on I didn't have to adjust them in height. I left them in the same position as with the stock springs and got less squat and good cornering. I still have the stock springs on the front shocks.