Why is less weight not always a good thing?

[mbeatle]

Though my E-Revo isn't here yet, and upgrades are still a ways off, I'm already planning upgrades. I've read that lighter weight is good to a point, but it eventually becomes "too light" and performance will start to suffer. Can anyone tell me why that is? In my days of auto racing "adding lightness" is one of the best, and sometimes cheapest, ways to improve performance. I can understand if you remove so much weight that the truck's balance is skewed significantly, but in general I see no negatives. Can someone educate me as to what happens when you go "too light?"

[Chachi_RC]

Yeah, I would have to agree with the statement of sometimes light-weight can be too light. I would think it is from not getting enough traction to the ground, because if it is too light, it spins the tires. Think of when you get stuck in snow, and you are just spinning the wheels. Then you get your buddies out to start bouncing on the back end so the tires will bite down and actually grab the ground and get you unstuck. Pretty weak analogy, but only one I can think of.

Also, I would think that it would have some effect in the air as well. Too light and it may get tossed around flying over a jump, where with some weight to it, it may fly straight and level. That said, starting with a 10lb truck, I don’t think you could lighten it up too much. Especially a MT with the big tires. I know the buggies probably run into this issue often.

The key I would think is getting the weight balance correct, not just trying to make it as light as possible. Just my thoughts on it…….

[jayjay283]

That said, starting with a 10lb truck, I don’t think you could lighten it up too much. Especially a MT with the big tires.

lol exactly, good luck lightening up and revo or emaxx TOO much. If you had gotten to the point where you felt you needed to add weight, Im sure you would be $20,000 in the hole.

[RcRacer4Life]

lol exactly, good luck lightening up and revo or emaxx TOO much. If you had gotten to the point where you felt you needed to add weight, Im sure you would be $20,000 in the hole.

hahah

Quoted for truth!

[mbeatle]

It'd be interesting to see a drag race between a very light weight truck and a heavier truck with the same powerplant and the same tires. Rally cars also race on low traction surfaces and I don't think they're concerned with being too light. They also use narrower tires to put more weight onto a smaller area, increasing grip on low-traction surfaces. I know that narrower tires in the snow are better for grip. Narrow, knobby tires are better in mud than wide, chunky tires, assuming you're not trying to use tires as floatation devices.

The jumping thing is completely new to me.

[TexasSP]

In my experience it does more to reduce rotational mass than to reduce dead weight on monster trucks. My focus is always getting a combination of lighter wheels/tires but still retain good traction. You also want enough weight so that the suspension responds properly, but a lot of that can be taken care of through suspension setup.

I think the second thing to consider is when adding hop ups deciding if it's really necessary and if it adds weight. Most hop ups people tend to buy do nothing more than move a weak spot to another location and pork out their truck. I know, I have been down that road as well. My goal now is to find a good balance between it all. Basically for me, if a hop up doesn't reduce weight or add performance, I typically don't use it.

[mbeatle]

Sounds like we're on the same page. I think I remember some people used the argument that a lighter truck will get "thrown around" on bumps, but that'd just be a symptom of being over sprung.

Rotational mass is where I'd want to start first as well, especially the wheels/tires. From there I'd try to eliminate as much unsprung weight as possible. It's nice to hear that the Revo is pretty strong right out of the box. According to Traxxas the E-Revo is 158 grams lighter than the 3.3. Assuming it's just as durable as the 3.3, that's cool! I also wonder how much weight a single brushless motor setup will save you over the Titans.

[TexasSP]

Depends on the motor, but I think it would be worth 6-8 ozs on average.

The few things I did that were worth while on mine was eliminating the bumpers, and some other unneeded parts along with replacing the stock hinge pins with JD Carbon hinge pins. Also replacing the push rods and tie rods with either JD Carbon or the Traxxas Tubes is a big plus. A single servo steering setup comes to mind as well. It's all really common sense stuff in the end without sacrificing strength.

[mbeatle]

Yeah, I also plan on a single steering servo at some point, but maybe not until the stockers strip.

Doesn't a bumperless truck leave you more vulnerable to damage? I know my Stampede was nothing without its RPM bumper!

[TexasSP]

Due to the design of the revo and the skid plate, it never caused me a problem.

[outkast187]

Id say my single easily weighs more than dual titans. Could be wrong, never weighed a titan..my single motor is right at 1lb.

[TexasSP]

When talking about that pletty, I don't doubt it. Those things are huge!

[Andrew32]

i say the biggest difference will be the ability to put weight down on the wheels.

o and heavier trucks hurt more when they hit you

[mbeatle]

If weight becomes a problem with traction, why not run narrower tires? Or is that not really an option? If you have 4 kg spread over a contact patch of 100 cm^2, that's 40g/cm^2. If you cut that down to 3kg you have 30g/cm^2 assuming the same tires. If you run tires with contact patches that bring the total contact patch to 75 cm^2 then you'll have effectively the same traction... I think. Someone who actually took physics can chime in anytime.

[Chachi_RC]

Sounds like we're on the same page. I think I remember some people used the argument that a lighter truck will get "thrown around" on bumps, but that'd just be a symptom of being over sprung.

I think you are right on the nose here. I think back to when I had my 1/18th RC18MT. I thought at first it was neat, but running it across anything with bumps, it did get “tossed around” pretty bad. I tweaked the suspension anyway I could, and tried different springs and oils, but to no avail. Basically it came down to me being used to the way an EMaxx handled bumps, and really it did come down to the weight difference. I know, that should be obvious with one being 1/10th (plus) and the other a 1/18th but I had hoped it would perform similar when the bumps were to scale. It didn’t seem to work that way. As I said, I think on the E-Revo you won’t really run into the issue of “too light” just based on its size. With that said, TexasSP is right on with being careful as to what your upgrades are. I know people like upgrades for different reasons (bling, speed, durability, weight, etc) but turning it into, as TaxasSP put it, a pig, just isn’t worth the money or the crappy performance. Common sense is the key! Think it through as to what its effects are by itself, and to the parts that attach to it. Sing with me…..The leg bone is connected to the knee bone, the knee bone is connected to the shin bone…….

[Tempted]

You guys should check out the videos between myself, Andrew32 and Larrydino. I ran a super-light single VXL E-Maxx, Andrew ran a super heavy MM/7XL and Larry runs a V-Twin. Both mine and Andrew's trucks ran about the same speeds at +/- 45mph and Larry ran 55+. I don't think there is such a thing as too light. The heavier you are, the harder you hit things. That means more broken stuff. My truck almost never broke due to a crash. I ran it into things intentionally to see what would break and then I made the required adjustments to prevent it from breaking again. Take a look at a few of my past videos and watch what I put it through. Because it was light I was able to drive away from things that would, and did cripple others. No, there isn't such a thing as too light, just set suspension appropriately. Also, one thing my truck demonstrated more than anything else was how little such a big 4wd monster truck stressed the motor/esc. My truck never ran hot with a VXL system. That is saying something when you consider the system was designed for smaller, 2wd 1/10th vehicles. So the recap, less weight equals less heat, less stress, less broken parts, longer run-times and a faster truck. What was the downside again?

[JAKETHESNAKE28]

A downside could be that you can't corner as well. But for speed runs it is more than fine.

[mbeatle]

I still don't understand how a lighter vehicle would corner worse than a heavier one, all else being equal. Any hardcore racers care to chime in? I know that 1:1 cars don't work on this principle, but these aren't exactly scale cars either...

[Tempted]

No, lighter doesn't make cornering harder. The reason is the lighter vehicle doesn't require as much energy transfer to change directions. In most cases a lighter vehicle will corner better due to less foward momentum which makes it easier to turn. Its all about suspension.

[mbeatle]

Its all about suspension.

I agree this makes the most sense, but I think there must be more to it, such as the contact patch issue I brought up. I could be wrong, however. Traxxas has their 4 articles on setting up the Revo. Weight is mentioned briefly in the first article, in how the writer's truck is 1.5 lbs lighter than stock. The second article goes into depth a bit more about weight, specifically balancing the truck. I can definitely agree that good balance is very important, but I thought it was odd that the writer would use ballast in the front to even it up. I guess balance is more important than raw weight reduction.

Nowhere do they mention tires... perhaps because they don't really make many tires?