Third bearing conflicting info

(Marin Vujcich) #1

Hi all
I need advice on 3rd bearing fittment. When to use or lose. Kart is an exprit noesis.
Thanks in advance

(TJ Koyen) #2

Running the same kart, we keep it loose as our baseline setup, and rarely tighten it.

Tightening will effectively stiffen the axle. This will reduce flex in the rear of the kart and eliminate some of the inside rear wheel lift. If the kart is hopping from being too soft in the rear, the 3rd bearing is a good quick adjustment to help eliminate that.

We usually use it as a quick test adjustment to see if we need to go stiffer on the axle. If we tighten it and the kart gets better, then we know that we should probably go to the next stiffest axle if the track continues to grip up.

(Marin Vujcich) #3

Thanks for quick reply.
What would you suggest as a base setup?
Rotax, dunlop DFH, 165kg (364lb). Tracks low to med grip.
Trying to free up off the turn.

(TJ Koyen) #4

Like I said, we run it loose as a base. I believe that is the OTK recommended setup as well.

I always start with the OTK baseline setup and rarely stray too far from it.

If the kart turns in well but isn’t getting off the corner properly, I would take a look at reducing some caster. If the kart isn’t free off the corner, the inside rear wheel isn’t staying lifted long enough. The lifting action is happening too quickly. Reducing caster will help slow down that lifting action and keep the inside rear up longer, helping the kart roll off the corner better.

There are several adjustments you can make, but I would start there. Any time you can reduce caster and keep the front end working well is good.

(James McMahon) #5

Welcome @Marin_Vujcich!

Don’t be afraid to experiment and try changing one thing at a time.

(Marin Vujcich) #6

Thanks for the responses

(Christopher Ramnauth) #7

Hey Marin,

Did you do some more testing yourself on this? I’d be interested in hearing your findings/thoughts on running the bearing loose vs tight on the rotax senior application

(Marin Vujcich) #8

Yip have done.

In short the 3rd bearing in on the OTK makes the inside wheel drop to quickly and more likely to get an exit push.

Never run it now. Might be ok in the wet, but havnt experimented with that.