The amazing, bouncing RC10GT!!! HELP!!

[elburro]

This thread is kind of related to the Ultimate Urban RC10GT thread in that it involves the same truck. I think the problem is that I don't understand suspension very well.

I did a couple of test runs this weekend on a pretty smooth concrete runway in Floyd Bennet Field. I do not understand the behaviors I saw so I throw them out for your opinions ...

1. The truck swings it's rear end out of turns.

2. Observing the front end during a straight line run at WOT, the front wheels bounce up and down to such an extent that you can here the engine wine bouncing with them and the truck becomes hard to drive in a straight line. Help!!

Heres the current setup ...

* Entire Chassis lowered .5 inches (front and rear).
* All shock absorbers rebuilt with 40W oil and spacers.
* 18T/66T gearing.
* Red springs in rear, silver springs in front.
* Stock caster blocks (waiting for 5 degree ones to arrive in the mail).
* Street tires with foam inserts. (I think they are "Road Hawgs")

EB

 

[Nitroaddict]

elburro - pick up the xxxmain tuning guide - it will really help u understand suspension setups among tones of other valuable information.

Remember - the rC10GT was never ment to be a road machine - so its not going to behave its best in that environment. if it spins out everytime u come around a corner, it means u are not getting enough weight to the drive wheels, therefore u need to soften up the rear suspension. However, if it is bouncing in the front, then u have the front suspension to hard, and need to soften it up, which in turn will cause the vehicle to spin out even more aggresivly in the turns. Another significant cause to the bouncing can be attributed to oil that is too thick. you didnt indicate what oil wt u are using, but it shouldnt be any thicker than about 30wt.

try this:

1. adjust the front Toe In to 2 degrees toe IN. this will help stabilize the truck in the turns.
2. Soften up the front suspension with either red springs, or switch to a much softer weight oil, such as 30WT.
3. Soften up the rear springs substantially, such as the green springs. also reduce the wt to 35.

 

[FastEddy]

Following the guidelines above will get you a bit closer.

In the rear, Hold the truck off the wheels and clip the springs to length so when fully extended the spring has 0 compression.
Doing this should let the rear sag. At this point you will be able to use ride hight adjusters to help dial in the rear. you should also do the same for the front.

As far as the front wheels bouncing, Is the entire front of the truck bouncing the same on both sides or is each side bouncing at a different rate. Sometimes its difficult to see but its important to know. Get down low and do a speed pass directly toward yourself.

• What tires are you running?
• What Shocks are you running?
• What pistons are you using in your shocks 1, 2, or 3 hole?

Just a stupid thought, Are your tires round and are they in balance? If you are using rubber street tires get rid of them or use them for corner markers. Get a set of foams. The rubber tires balloon at WOT and will make it impossible to handle.

 

[elburro]

Originally posted by FastEddy
Following the guidelines above will get you a bit closer.

In the rear, Hold the truck off the wheels and clip the springs to length so when fully extended the spring has 0 compression.
Doing this should let the rear sag. At this point you will be able to use ride hight adjusters to help dial in the rear. you should also do the same for the front.

As far as the front wheels bouncing, Is the entire front of the truck bouncing the same on both sides or is each side bouncing at a different rate. Sometimes its difficult to see but its important to know. Get down low and do a speed pass directly toward yourself.

• What tires are you running?
• What Shocks are you running?
• What pistons are you using in your shocks 1, 2, or 3 hole?

Just a stupid thought, Are your tires round and are they in balance? If you are using rubber street tires get rid of them or use them for corner markers. Get a set of foams. The rubber tires balloon at WOT and will make it impossible to handle.

* HPI V-Groove tires (not M compound).
* Stock shocks, rebuilt with 40W oil and silver springs (front).
* Stock shocks, rebuilt with 40W oil and red springs (rear).
* 2 hole pistons as I recollect.

My observation is that the wheel bouncing was on both sides but not in sync with each other. The rear wheels seem to not bounce at all. Also, I have never done any kind of balancing on my tires. I just glue them on and mount them. Should I be doing tire balancing? How?

Ouchie!! Foams are expensive!! Whats a good source for less expensive foams? Also, can I use Foams on the front and rubber on the rear if I want or is that bad?

EB

 

[FastEddy]

Here are the tires you will need.
http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXCME3&P=7

You can use the rubber tires but will not get near the performance as using foam. All 4 tires must be foam or rubber. Dint mix drinks or tires at this point.

I would first follow my alignment directions in your original thread.
Next you will want to make sure your tire are round and balance them.

Lift the truck off the ground a spin a tire. This will give you an idea if they are true. If they are close, you will find that they have a heavy spot that will settle to the bottom when they quit spinning. I'm going to assume your tires are glued. When you have found the heavy spot you have 2 choices, Add weight to the lite side or take some off the heavy side. I like to take it off if its not to far out of whack. Use a drill and make a few holes on the inside of the rim. Removing plastic will remove weight.

If you have 2 tire/wheel setups that are truer then the others mount them on the front.

Next time you mount tires you can get the balance close by spinning the tire on the wheel to adjust the balance before gluing.

Get the balance close, align the wheels, clip the springs and let me know if it helps in getting you closer to the "ZONE"

 

[elburro]

Can we talk about the durability of foam tires? I'm asking cuz I get the feeling I'll be laying out cash every weekend for new foam tires. If this is the case then I may have to stick with rubber and sacrafice some performance.

How durable are foam tires anyway? The left rear tire is subject to getting sprayed with liquid fuel from the exhaust all the time. What can I do about that?

EB

 

[FastEddy]

I get a season out of a set of foams. This is about 3 hours of run time. I rotate them after every heat.

Try to tune your rubber tires first and see if they work for you.
Try using an exhaust deflector.

 

[elburro]

Originally posted by FastEddy
I get a season out of a set of foams. This is about 3 hours of run time. I rotate them after every heat.

Try to tune your rubber tires first and see if they work for you.
Try using an exhaust deflector.

I think I'm going to stick with rubber tires because the best I can do is switch the rear tires from left to right since front and rear are different wheels on the RC10GT. I'm gonna do the 5 degree caster blocks, get as much rubber on the floor as possible, set a little toe in and go for it. I think I'm gonna do red springs in the front and green in the rear and maybe that will help stabalize things. I'll let ya know.

EB

 

[specter]

but it shouldnt be any thicker than about 30wt.

Wow I run 60 weight all around with associated silver shocks in the front and these silver springs I took off of a tamiya king blackfoot. No handling problems yet.

 

[FastEddy]

Originally posted by specter


Wow I run 60 weight all around

I didn't catch the 30wt good eye!
I'm all with the thicker oil. I have tried up to 100wt at times but for your bashing conditions 50-80wt is more in the range.

 

[specter]

when I used the stock 30wt it was horrible I flipped over more times than I could count and the back squatted low enough to sweep the street.

 

[FastEddy]

Originally posted by specter
the back squatted low enough to sweep the street.

Contact the lot owner and see if you can make a few extra dollars

 

[elburro]

UPDATE: Today is the day!!

Today I get to go down the block during my lunch hour and buy springs!! I'm gonna get front and rear sets of red and green and if I can't get a combo that works, then I dunno what the hell I'll do. Striclty from a mechanical standpoint, this is what I have done so far to the truck ...

1. Installed 5 degree caster blocks so now most of the front tire surface stays in contact with the ground in all positions.

2. Installed 0 degree suspension mounts in the rear.

3. Front and rear camber adjusted so that maximum tire surface meets the ground at all times.

4. Ruined an entire set of green springs. I will avenge this lameness this afternoon hopefully.

5. Rebuilt all shocks with 40W oil and spacers shortening shock length by /12 inch.

... if all goes well today, I'll be road testing tomorrow morning for sure.

EB

 

[FastEddy]

Looking forward to an update.

 

[elburro]

UPDATE:

Ran the truck again on my street this Saturday. Quite speedy with .15 CV-R. The rear end comes out from under it in the turns though. Definitely need more traction in the rear.

EB

 

[FastEddy]

Lower the rear or bring the front up a bit.