I understand.
How was the very initial turn in response all the way to mid corner in tight corners? This will help understand if they used a very soft front tube, which turns out to be too flexible for hard tires.
I think the indication that the chassis frees up with softer axles also is a tell tale sign that the rest of the kart is relatively stiff vs the front.
Funny, Iâm in the camp of 100% loctite all the time. I snug the set screws to âpretty tightâ, back off a 1/4 turn, the tighten 3/8 of a turn, which should get it to âtightâ but not denting the axle. I canât remember the last time I had an axle shift, and this is in the shifter only running set screws on the outside bearings.
One thing Iâm adamant about with grub screws is no lube. Ie make sure everything is clean with brake cleaner or whatever your favorite solvent is. Iâll add a smidge of locktite for fun.
Same technique my dad uses but I never do the tighten-loosen-tighten method on the OTK and never have issues. But every kart has quirks so on this one I will be doing that method now. I also tape the screws sometimes as well. And I have heard many arguments for and against Loctite. Personally I have always used it but I know some people hate it.
The kart just feels like the front is âsquishyâ on turn-in to the apex. Like it is yielding too soon and flexing too much. I think youâre right and the front tube is too soft because the frame design is the same between this kart and the stiffer kart, the material is just different. So on the stiffer kart it isnât as much of an issue but with the softer material now that front tube is softer and doesnât have the strength to deal with the steering input. So even with caster in it still burns the front tires up a bit.
Also, I should note it is a small problem, the kart still had pace and once we put the 9F wheel on the tire temp was well controlled but still just slight understeer.
@tjkoyen more for me trying to wrap my head around the front changes for futureâŚ
You mention no bar and looking at hubs and spindles to stiffen or add front. Is the front bar too much change, affecting entire kart or ??
We tried the nylon front bar before but even that just flattens the whole kart. This frame design is made to work with no bar. Some karts a front bar is optional, some itâs mandatory, some itâs useless.
The more I drive this kart, the more it feels like the ART GP chassis I had which also didnât use a front bar. Which is a good thing; that kart was epic.
Another important info.
Geometries meant to be used with no bars either have longitudinal chassis rails that are designed to increase turn in (see KR, CRG Road Rebel, which have longitudinal rails that converge into each other) OR a conventional parallel geometry but with a front cross tube thatâs stiff enough to compensate (like the Parolin) .
The upside of having a dedicated mid section geometry that helps turn in, such as the KR, is that you can afford to go soft and flexible with the front transversal tube, which can help depending on the situation.
From pics, it seems that the BestKart is indeed of conventional design and would indeed maybe benefit from a stiffer front cross tube for harmonization for your application.
Would be interesting to test the frame on an X30/ OK-N with softer tires and see how it reacts, maybe it would shine under such circumstances 
Is this before it merged into Birel ART?
Yes, ART had a chassis for a few years (Leclerc, Hanley, and I forgot who the other KZ driver was, were the factory pilots in Europe) and it was very strong. Birel was in a bit of a slump and partnered/bought out/merged with ART to form BirelART as I understand it. The ART design eventually became the MadCroc/Croc kart I think.
I know a couple people here in the States bought up all the ART frames that were left because they liked them so much.
I think you said you went with a softer chassis for Stars so an all 30mm frame or was it a special blend of 11 herbs and spices to get it softer?
Curious on the in-house components as to me itâs the little things that add up to a nice quality of life when wrenching on the kart. Anything you would change there?
Lastly, cool to see you ran with Prodigy, had some good times racing their group of guys around GoPro.
I ran medium soft. TJ was on soft. They are all 30/32.
More bestkarts at the next race.
The frames are the same design but special herbs and spices to make the material softer or stiffer.
Overall the components are nice. There are a couple little things I might like changed but overall there isnât any dumb design aspects that make me annoyed when working on it. I agree thatâs a big thing. Every kart has quirks but there arenât any issues with bolts fouling into components or things like that. Some karts I work on and go âwhy the f would you design it that wayâ, and the BestKart seems like most stuff is pretty common sense and laid out in a decent way.
Did you consider raising the front height?
Ah I forgot you were giving them a try. You were previously running KR?
I suppose it wouldnât take much of a slimming or widening of the waist to effect torsional rigidity. Or they could just do it with mechanical properties of the tubes.
@tjkoyen - above you said:
Ackermann : Standard
What are the alternatives? And what set of holes does it map to?
Thank you for the excellent write ups.
The BestKart has additional holes on the spindle to change the Ackermann effect, or there are other steering columns with different mounting points for the tie rods to do the same.
I considered it. Had we had a proper rain session, we wouldâve run it up. I didnât try it in the dry just because of lack of sessions to test everything. Itâs on my list for testing this week.
It is pretty crazy to think about the infinite combinations of tubing diameters, wall thicknesses, heat treatments, and then minute adjustments to frame design you could make to have tons of different characteristics with each kart. Iâm certainly learning a lot about actual chassis design by working with Tommaso and the BestKart guys.
Awesome thread. Enjoyed reading!
Will be back out testing Friday at Dousman. Grip will be low as the track hasnât rubbered in and it has been raining non-stop in the Midwest for days. Should be interesting to see how the softer kart works in those conditions.
I will be testing some different front hubs, front ride height, possibly Ackermann if I have time, and some other little ideas I have bouncing around in my brain.
I donât think Iâll be able to get new components before USPKS, so Iâll be cobbing together a few things to try and accomplish the goal. Itâs actually really fun; feels like we are doing proper homebrew development like racing in the early days.
Take it with a grain of salt, but that gearing seems too short for senior class for that layout. I think you wouldâve been faster with something like a 10/70 ratio.
The lower gear felt boggy. I put three teeth on and the max MPH stayed the same but I picked up off the tight corners. Could be motor dependent, but at the last USPKS race I did at New Castle, 1st and 2nd ran nose to tail the whole final and one was spinning 15k and the other over 17k, so I think either end of the spectrum can work there depending on your motor or the way your kart is setup.