Hey all, I’ve got this strange behavior on my kart. On corner entry, it feels as if the rear end wants to go straight, so an understeering condition, but then it grabs up after the apex like it would when you have a shorter rear width, losing time on corners when I need the kart to roll up and use the track and also corners where I need to turn sharp. Front alignment changes dont work, removing the front bar makes it worse, front width doesnt do it either. it’s completely out of balance at the rear.
we race with MG SH tires, the harder compound, since this chassis is a bit tricky to tune and before trying unconventional ways to tune it, I might as well ask here.
The regulation state that a set of tires must last 2 race weekends. So with new tires im not having too much of a problem (but still I would like to make the front end a bit pointier) but on the second race weekend, with rubber laid up on the track, it’s just impossible to drive fast this way.
im pretty sure im not tuning it properly, my intuition tells me the rear is too stiff with the M20 axle and 2 seat struts per side on 165kg min weight, racing with the IAME MY10 engine (X30 without clutch) but wanna know if anyone is more familiar with the Heron frame before I go crazy on it and make it butter soft at the rear and hope for the best
Sounds like it isn’t jacking weight quickly enough. Increasing caster would probably be the first suggestion.
What is your weight distribution/seat placement? If your typical adjustments aren’t working, always double-check those two things to make sure the kart is fundamentally set up correctly or close to it.
That engine package on that tire sounds tough to tune.
I have an IPK silver seat, and i did not try 1 strut per side this weekend, ran 2 per side all day. However in the past I ran 1 per side and it behaved similar, turns out that adding struts might be useful on a green track or cold winter days
Tried shorter hubs but all it did was make the kart bog down a little more out of corners, they didnt seem to affect turn in at all and the “effect” they give is more subtle, again something i can use on greener tracks but not on warm days with rubber on track
The kart is much more balanced on test days where there arent many karts to rubber coat the asphalt
Edit: seat is positioned 15cm perpendicular from the axle and 20cm from top of the seat to the axle
I use a Greyhound soft seat, similar to T11
Here is my best setup
3.5 spacers front
2 deg camber
Front bar in (plastic)
3rd bearing loose
2 seat stays
1 seat stay engine side
Loose rear bar
Seat flat bottom
140mm to axle from rear of seat @ 90deg from the seat
thanks everyone for the help, I was close to becoming crazy when suddenly something clicked, sent the frame to be straightened out. The caster and the camber were out of position, the front end of the frame was lower than factory specs.
Then we went to another track, the tendency to understeer was still there and was very evident so we did the following:
-Raised front end
-alignment: 2.5 camber (positive) and 3 degrees toe out
The kart now turns properly and holds in well on longer corners. also we tried no struts vs 1 per side vs 2 per side. 1 strut per side is ideal