Weird steering behavior: Kyosho PureTen Mantis FWD

[Germano]

Hi guys

I converted a RWD Kyosho PureTen Mantis to fwd. Now, I've been having problems to keep the car in straight line.
I've realized some weird: When I push the car down, the front wheels increase the "toe in" (more convergent). Please, check the video. I'm not able to solve that.
https://youtu.be/M8xDtIT537Y

[romulus22]

Just some bump steer, easily fixed. Just put some washers under the ball studs either on the hub side or the bellcrank side. Hard to tell looking straight down on it. The more washers you end up using the more leverage you will have on that part though. So keep them to a minimum.

[Germano]

Where do I need to put those washers?

[shodog]

You need to take some stack out of area between the knuckle and ball end. Drop the links and make them almost parallel to the arms.

[Mr. ED]

You need to take some stack out of area between the knuckle and ball end. Drop the links and make them almost parallel to the arms.

That would be right if the steering links were roughly the same length as the upper links and if he were fighting toe out. But he is figthing toe in: because his steering links are longer than the upper link on the left (and much longer on the right). He'll need a dual becrank set up to get this correct.
The space to work with is terribly cramped though ... study the recent wave of fwd touring cars to see if you can steal an idea is the best thing to do

[romulus22]

I would still recommend removing some from the knuckles. The turnbuckles look like they are currently up at an angle. As the arm sweeps it makes the turnbuckle even shorter. If you lower the turnbuckle at the knuckle as the arm cycles the turnbuckle will not sweep as high up therefore keeping its length as long as possible through the travel

[Mr. ED]

I would still recommend removing some from the knuckles. The turnbuckles look like they are currently up at an angle. As the arm sweeps it makes the turnbuckle even shorter. If you lower the turnbuckle at the knuckle as the arm cycles the turnbuckle will not sweep as high up therefore keeping its length as long as possible through the travel

nope, the opposite. When you watch the video it shows toe in is increasing when the suspension is compressed. Maybe raising the top links anchor point on the front shocktower is possible also? (It's not possible to see in the video how much the wheeltops lean inwards)

[romulus22]

You’re correct. I couldn’t remember what it was doing in the video. I’m at work and quickly read/miss read thought somebody said it was toing out.

That’s what I get for trying to Internet while working

[Mr. ED]

back to work you naughty little...

[Germano]

more pictures

[Germano]

I would still recommend removing some from the knuckles. The turnbuckles look like they are currently up at an angle. As the arm sweeps it makes the turnbuckle even shorter. If you lower the turnbuckle at the knuckle as the arm cycles the turnbuckle will not sweep as high up therefore keeping its length as long as possible through the travel

I bought a shorter servo saver. That will decrease the steering links angle.

[Germano]

You need to take some stack out of area between the knuckle and ball end. Drop the links and make them almost parallel to the arms.

That would be right if the steering links were roughly the same length as the upper links and if he were fighting toe out. But he is figthing toe in: because his steering links are longer than the upper link on the left (and much longer on the right). He'll need a dual becrank set up to get this correct.
The space to work with is terribly cramped though ... study the recent wave of fwd touring cars to see if you can steal an idea is the best thing to do

I think the FWD version of that chassis was poorly designed. Maybe, that's the reason there isn't the manual on kyosho site. I thinhk they know about that issue and decided to eliminate that fwd chassis from his history.

EvolutionRevolution has been working on the same chassis. So, he'll have the issue.

I bought a dumborc with gyro. I hope it helps.

[Coelacanth]

As the guys have said, you need to get those steering links roughly parallel to your front arms. A shorter steering servo combined with possibly replacing your ball-ends on your steering arms with low-profile ball-studs would probably get those rods parallel to the arms. Here's a sample picture; you can buy ball-studs that are low-profile so there's hardly any neck at all below the ball. That would help you drop the outer ends of the links up to 5 mm or more.

[Mr. ED]

Mark, the steering links are about twice the length of the upper links. That makes it impossible to keep them parallel to the upper links or lower arms throughout the suspension travel. Bumpsteer is inevitable without shorter steerinlg links

[Mr. ED]

Germano, you could get a little improvement by lowering the toplink outer mount on top of the C-carrier