I finally purchased a Sniper aligner and found that we were off and have an issue. We had toe in and negative camber. The problem found was while performing the caster sweep. The left front swept the ruler near the top just before full steering lock. The right front swept the ruler about 2 inches right of the ruler and about 1.5 - 2 inches high. I set the toe to almost +2deg total and swept caster again with about the same result. I then set the camber to almost +2deg total and seen things come together better but still off. On a third try I found a happy medium with the toe set again and the camber 90% equall and got the sweep to be 95% equal at or near lock but I still believe we are a little bent up somewhere.
So we scaled before all this and suspected something was off with the kart. We were 10lbs light on the right front and just about 20lbs light on the left rear. I made a slight seat to left adjustment and changed did the best I could to relocate his weights on the seat that day. So now that the alignment is set we scaled again. This was done with bathroom scales. I balanced scale readings with a 25lb weight. I used a level to find the flatest possible spot. I shimmed the scales (I will say that cheap mechanical scales are not all equally flat on the bottom), and checked checked stagger. This second time we got similar numbers but better in the front:
Left front 62.5 Right Front 61
Left Rear 79 RIght Rear 91
Worth mentioning is that his seat is favored left as much as you normally see, and due to us having to buy such a small rear sprocket that day at NCMP his engine mount is as far forward as it will go and will actually have to come back to a normal position once we put a 16 tooth clutch on and add teeth to the rear.
So 38% front weight? That’s really low. 41-44 is the range on most karts. Would be interested to see how the rear weight resolves itself if you moved the seat forward a bit to get the front/rear distribution better.
And you’re at actual positive camber on the Snipers as well? In general a little negative seems to be good. Half a box per side is where I’m usually at.
Sounds like the kart was/is twisted a bit if the cross is off in that way.
I am getting 42.1 % front, 57.9 % rear. I would think that the kart should run a little negative camber as well but read alot about OTK in particular suggesting 0-1deg positive. I wouldn’t argue with you, I see that you are an OTK guy with much experience. That said I can tell you that we eat up the inside half of the fronts (worse near the dots) with it how it was before and that was with tow in. The outside edges are fresh looking. I don’t know if now that I should flip them on the rims, or is it too late and just finish them off? I feel that we have had issue with getting this particular kart to jack in the rear. I have with this alignment almost everything going that direction I think. Examples: The seat is up 14mm from flush to bottom of frame, rear ride height is set high. N axle set all the way in. Front torsion bar full stiff. Front width is 1 thick and 1 thin inside. Front ride height is neutral. Caster is all I can get. Weights are not low on seat. Rider is thin slender 5’9" 130lb 15yr old setting up average. I want at this point to see the thing hop/bicycle just once and then back it down since I sorta think this chassis is maybe flexed out. Along with all this we seem to struggle with grip compared others which besides lap times is why I have played with it trying to “see” a difference. I will add that my son is far from being able to give me feedback and he certainly needs to improve his driving. I feel that if we are 2.5 seconds off the fastest 2 in class that he is probably at least 1.5 seconds as to why.
I will try this alignment although the camber does seem wonky, and if it doesn’t repsond well we will back down to zero and then -.5 each side.
Sorry, I’m an idiot and haven’t done math in a while, you’re right 42% front. Okay in that case you’re good on that.
Most karts eat the inside front of the tire up as normal due to the front geometry. If you’re going to flip the tire on the rim, do so every session or every other session. If you do it after the fronts have worn in a lot, you significantly reduce the contact patch because of the camber in the tire and will have all variety of handling issues.
The rest of your setup seems fairly normal, as I’m also around your son’s size. If you are 2.5 seconds off, most of that isn’t the kart or setup. Unfortunately setup accounts for 0.5-0.8 of your lap time deficit probably.
With that setup, there is no way that thing isn’t jacking if driven properly. I’m 5’7" and if I ran that setup, I would be hopping all over the place, and your kid is 2 inches taller. My seat is even mounted roughly the same height as yours.
You’re doing all the right things setup-wise to get it to lift, but I imagine the kart isn’t really at it’s limit and it isn’t going to work until your driver starts getting closer to the limit. I don’t think the kart is flexed out. I’ve seen/driven OTKs with several seasons on them and they still work just fine, so unless this thing has lived a rough life, I’m guessing it’s okay.
Couple of notes in general on the OTK especially for New Castle…
Max caster is going to scrub the front and bind the kart in all the 90s and fast flowing corners, so if you can get away from that, you’ll benefit a lot from better rolling speed in any corner that isn’t a tight, technical corner.
Front torsion bar in the vertical setting is going to give that thing a lot of initial lift and jack, but it will set it down almost immediately. You are stiffening the whole frame, so while you gain on entry, it’s going to sit flat at apex. I almost never would run the blade bar vertical for that reason. It will kill your apex → exit speed.
With the rear ride height high, I have to imagine this whole kart is just being worked too hard and binding up in the corner in conjunction with the other adjustments you’ve made. If you just continue to add jacking to the kart, you’re really forcing the tire into the track and binding the tire, you’re working the chassis super hard and binding the chassis, and the kart isn’t going to roll off the corner very well, especially in 206.
Honestly if you’re 2.5 off and have done all this work to the kart, it’s probably time to go back to the neutral setup and reevaluate what path you’re going to take on the setup. And with that time deficit, I would be focusing all my efforts on driving improvement.
The weight figures aren’t that bad to me. 10 lbs off in the rear isn’t the end of the world, especially if you’re running NC in the counter clockwise direction.
You speak the truth that neither me nor my son wants to hear. He doesn’t need a another kart. I need a different driver lol. J/K
Seriously I agree with you. We started off with rear height low and neutral caster. We played with front width and back then if we went any wider we saw mid corner push in the tighter corners. We played with the torsion bar some, didn’t see alot either way before I broke a clamp and it didn’t handle well while it was out. I would have to look but I may have it 45deg roated now. We actually ran WRP last year and he only got 2 practice sessions for about 50 laps each. Then 4 races and one late practice day at G&J after WRP shut off early for expansion. When he looks his best the tires come off hot and gooey. We usually go out 14-15psi. Usually 15.
His kart seems to take 2 laps to come in.
I did buy a MGM roller recently that I thought about letting him try a KT100 on (I picked up 2 Jr can engines and 2 Sr engines this past year). And I have a like new stock animal we could put on it just for practice laps. But I get it, I can only try to give him the best with what we have to work with and the rest is up to him at some point.
I have limited time with him and WRP is 5hrs drive round trip. NCMP and G&J are each 6hrs. So seat time is tough to get. I have scheduled my to vacations this year around races that his mother would have him just to capitalize on opportunities to race.
I love to learn these things and like to be able to picture the workings or theories of operation in my head. I will say that I stuggle to picture and understand axle stiffness and flex when it comes to contact patch, while trying to get jacking. I look at it like a softer axle will cushion the snap load on the tire and maybe flexes enough to keep a flatter patch while jacking? Maybe some twist factor there too. I was under the impression that generally most Lo206 guys favor soft 90%. Then the other day I have someone saying that he thought most fast Jr. guys are running stiff axles. I understand that wider means less weight loading the tire (while effectively changing the center of gravity while turning or it’s leverage) but struggle to picture the effect on jacking the inside rear. I understand how caster binds up the kart. I understand that the sharper turn is when it will bind the most.
I may back it down some, sodten the front bar some and maybe play with widening the rear a little at a time which is one thing we really have not tried much.
Last year at WRP we usually were 3.86 to 3.73 and I was guilty of trying low gearing early on to overcome newbie driving.
At NCMP we went showed up geared too short like I new we would be and immediately went to 3.53 and he thought that was pretty close. It was a cold slick day. He liked NCMP better than I thought he would. I like all of them but favor WRP and G&J. We picked 2 seasons worth of rubber on his tires at G&J and the kart mostly handled the same with them looking like that. We did not have a tach last year and he at times struggled to tell if when and where he was on the limiter. We have a new Alfano to mount before SIRA at WRP. I am going to try and gear taller this this year. And he needs to get his corner speeds up so he can carry said gear right?
And generally speaking widening the rear with a soft axle is a way to free it up some? What percentage of effect does one expect to go from standard hub width to wider hub width vs N axle to the next stiffness?
Not on an OTK. Softer will give the rear more traction, it’s the rain axle.
N or A axle for 95% of conditions
H axle for high grip and hot track
Q or U for rain
The N should be fine. I run the N most of the time even at big national races.
I almost never change rear hubs. I don’t like how they change the tire’s contact patch interaction with the track surface.
Honestly the baseline neutral setup in the OTK should get you within a second of the fastest guys in almost any condition. So my recommendation would be until you are within a second of the leaders’ times, you’re wasting energy and overthinking the kart setup. I get that seat time is tough in your situation but honestly that sounds like what the kid needs. Plus maybe some coaching or a data review.
Thanks TJ
I thought about that contact patch angle being a factor. I will be using go pro on the kart this year and I hope we can use that to correct some things. My goal will be keep it on track most weekends, hope to have mid pack speed and not get lapped. Most importantly fun quality time.
This. Put the OTK baseline on it and leave it alone until he can drive good. Messing with the kart on a new driver just makes learning to drive harder. You’re just going to go out of the tuning window trying to make the kart work with inexperienced driving ability.
OP, when you’re at WRP stop by the furthest garages north and closest to the track. Burpo and I can take a look and see if there is anything obvious that can help.
If you bought it used, then I would ensure that chassis is square by either taking to a chassis straightener or a kart shop that can does straightening. What year is it? Does it have standard OTK wheels?
I agree with TJ, put everything back to neutral and put the seat where it should be and let him drive until he is 1 sec off fast time. The OTK kart at the neutral setting will right for 90% of the time and if you don’t have a lot experience, it’s probably good for all conditions. Ask around and find out the gearing and maybe add a tooth or two. To see if he has progressed, take 2 teeth off and see if goes faster.
Okay in that case you’re good on that.