Weird handling Bronco

[RudyF6]

So I picked up an early Bronco and so far loving it.
BUT...
When turning left at any speed it will pick up the front wheel like a desert racer turning at speed and then left suspension will stay extended until it bounces around in a straight line a bit. Stays flat turning right.
Nothing binding, all 4 shocks feel a bit gritty, but all the same.
Maybe a characteristic of panhard bar suspension? (Note - my 1:1 Broncos never did that!)
Can "torque twist" be that excessive?
I'm stumped, any suggestions?

 

[Fallen]

Believe it or not, it's the torque twist. The stock Bronco, while still fun, has too much down travel in the suspension. That combined with how soft the suspension is and the lack of any sway bars makes it a sucker for torque twist.

Now I don't recommend adding a sway bar or firming up the suspension. But lowering the Bronco to reduce the down travel helps quite a bit.

The thread I made about my Bronco details how I lowered mine. There's lots of help on YouTube about it also, as many people have had the same problem and applied the same solution.

 

[RudyF6]

I've already thought about lowering for a more scale appearance, especially if it helps with that. I already rolled it down the rocks on my first pack when the high side stayed extended. Scratched one corner of the body too - I almost felt bad!! :roll:
Thanks Fallen, I'm gonna' go re-read your thread now.

 

[ferp420]

check your servo end points

 

[RudyF6]

check your servo end points

I tried that, but it still starts lifting with only half steering input.

 

[ferp420]

I tried that, but it still starts lifting with only half steering input.

look for binding issues in the steering parts

 

[hnoroian]

When did this start, front end pic?

Track bar attached to the servo horn?

 

[RudyF6]

So after watching vids of lots of these doing the same thing, looks like shorter shocks will lessen but not eliminate it.
Wonder if a 4-link setup would cure it? No room to squeeze it in there without re-engineering the whole chassis.
I might experiment with track bar mounting - I think that contributes due to its angle. I'd like to see it closer to parallel with the axle.

 

[ferp420]

So after watching vids of lots of these doing the same thing, looks like shorter shocks will lessen but not eliminate it.
Wonder if a 4-link setup would cure it? No room to squeeze it in there without re-engineering the whole chassis.
I might experiment with track bar mounting - I think that contributes due to its angle. I'd like to see it closer to parallel with the axle.

can you get.it on video im not understanding what the issue is

dose the body lean when taking off on flat ground or while climbing a hill

or dose the wheel come up when turning

if the wheel lifts when turning thats a binding issue the servo is pulling on the suspention instead if just turning the wheel if your at max angle thats normal just turn down your steering rate or set the end points

if its doing it in the middle of the steering through something is binding up

the panhard bar needs to be parrallell to the drag link or your gona have a bad time



you can play with the front upper link that will change your anti squate and anti dive settings but i dont think the stock chassis gives you alot of choices on that mounting point but changing this might help depending on whats really going on with your set up



going 4 link wont stop torque twist but will stop tire lifting while turning but then you need to figure out how to get that link in there and on top of that you would need to mount the servo on the axle or you will have a bad time



if its torque twist you can add a sway bar to help tame the twist



if its tire lift take everything apart and clean and check every thing in the steering

 

[Fallen]

Timely conversation. I'm in the process of modding a Losi LMT sway bar to fit on the rear end of my Bronco.

It'll probably turn out to be way too stiff, at least at first.

 

[ferp420]

Timely conversation. I'm in the process of modding a Losi LMT sway bar to fit on the rear end of my Bronco.

It'll probably turn out to be way too stiff, at least at first.

ive had good luck making my own sway bars

i have been using insulation suports there 1/16th spring steel about 15 inches long makes 2 sway bars about

the longer the arms the softer they are

 

[RudyF6]

Can't find anything binding, the thing's brand new.
Left front lifts while turning left on flat concrete, but stays flat going right. Also does it climbing straight under load. This is why I think it's torque twist as Fallen addressed it.
Think about the angle of the track bar and drag link relative to the axle. Axle moves sideways with suspension travel however slight that may be, it moves right when compressed and left when extended. That changes R/L balance as the axle travels. More variables enter when you add steering to the puzzle. As I see it steering left pulls against the already steep angle of the track bar, weight is transferred right with body lean and axle moving left, all while torque is trying to drive the axle downward and the left is already "un-weighting" itself. Combine all this with short wheelbase and tall compliant suspension with lots of down travel and...
Google "Watt's link" and that's what I'm thinking of trying if I can come up with something workable. That would keep axle movement vertical with no arc. I'm no engineer, but I'm a hell of a tinkerer!
Having said all that, I'll probably try some 90mm shocks first, much simpler!!

 

[RudyF6]

Ok, odd side note -
Since I'm looking closer at front end links and such, I noticed the wheelbase was off by 3/16 side to side; front axle was crooked!!
Fixed, but no effect on the problem...

 

[Fricker08]

I’d definitely get 90mm shocks like some traxxas gts trx4 take offs on eBay and swap to those. Either to the stock location or to the lower link


Sent from my iPhone using Tapatalk

 

[ferp420]

theres no way to stop the axle from moving side to side it is what it is
it still sounds like something is wrong in your front end it shouldent do that there is only a few rhings that can cause that but i guess it could be torque twist it Just sounds extreme by the way your discribing it

 

[diceman42]

I'm seeing the torque twist in mine. I think it is twisting enough for the lower shock mounts to pop off. Yes, I've moved the lower mount but it's still occurring. Thoughts?

 

[RudyF6]

Definitely torque twist.
I've lessened the effect by about half with just a little preload or the r. rear shock and a shorty battery in the side tray. Big difference vs. the massive 5000 mah battery in the rear.

Haven't seen shock mounts pop off, but here's a weird one...
I have 2 of these, one's getting used and abused, run probably a dozen times with no problems occurring.
The other will be a project shelf queen, but I ran it right away to make sure everything worked. First rock maybe 30 seconds in, apparently the perfect storm of articulation, twist, and turning - the front driveshaft popped apart!

 

[diceman42]

Ya, I've been running my 5200MaH batteries in the rear. I'll give a smaller battery a try.

 

[Fallen]

I've heard of one other instance of a front driveshaft coming apart during a run. It hasn't happened to me, but I only drove mine for maybe 2 batteries before making suspension changes.

I just didn't like how unrealistic the stock suspension looked. It offered too much articulation in my opinion to look close to a daily driven trail truck, which is the look I was after.

 

[FaustKnight]

I switched to Incision 90mms, which are shorter but stiffer than stock and that solved my torque steer issues and the lifting tire.

Adding heavy brass knuckles helped too.