[OTK] Gaining in hairpins, losing in high speed sweepers

My home track has few low speed and/or hairpin corners. Most of the corners are highspeed or sweeping like a horseshoe or double rights/lefts. This is a problem for me because I seem to gain on my competition coming out of the hairpin and low speed corners but all the rest of the corners I lose so much due to excessive hopping. Is this indicative of any specific tuning problem? Center of gravity? I’m at 58% rearward bias.

I’ve tried all season to make the hopping bearable but it’s not close. The harder OTK axle and low ride height have had the most positive effects but I’m out of tuning options to free up the rear and feel like the problem is causing a huge loss in lap times. The variable that I can’t fully account for too much is seat position. I know… probably the most important but I use a DeepSeat so I can’t mount based on the OTK factory guide. What is the general rule for moving weight forward or back to reduce the hopping problem?

Before we move the seat, are you on the hardest OTK axle? There’s the A, H, HD, and HH, so there are options there.

What are you running for seat struts? Have you taken caster out and narrowed the front?

If your rear bias is 58% you’re probably pretty close on seat position.

HD. So you’re right. I’m not 100% out of options there. Going from N to HD has a small positive effect (i think) but considering another $200 for one step harder is a big bullet to bite when I thought going from N to HD would make a much bigger difference. Thoughts?

No seat struts. I’ve tried one on each side. Made the problem worse.

I’ve gone to one inside 5mm spacer with minimum caster. It definitely freed up the kart but still aggressive hopping on exit. Maybe its worth noting that the kart feels great for about 2 laps, okay for another couple laps, then the hopping gets worse and worse every lap after that. I’ve played around with tire pressure but can’t seem find a trend.

If I gain 9 lbs, I can race in masters. Thinking about trying that so I can add lead on the kart and lower my CoG.

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Okay so it sounds like you’re making the right choices. I would agree that the $200 to go one step harder on the axle is a hard sell in your position.

‘Minimum caster’, so you have eccentrics top and bottom, with the top arrow facing backwards with the bottom arrow facing forward? That would be full negative caster, which would be extreme but understandable. Of course you can get more extreme pills too for a bigger adjustment, but if we are pulling THAT much caster out we are probably out of the ballpark anyway.

Any video to show?

Could also reduce steering rate which would lighten steering and make it not as front heavy, but I’m not sure that would really solve the issue, more like band-aid it.

And you’ve got the rear width maxed out I assume?

Just for reference, our track compared to some across the country is more mid to low speed corners. We don’t really have “high speed” corners like some of the bigger tracks back east. You’re a pretty tall guy so you may want to consider a laid back seat, or a more reclined seat like the T9.5t.

Unfortunately, I don’t think adding weight is going to help. Even if it gets the CoG down, you are still going to fight it. On a positive note, your competition would theoretically be slower :wink:

Is the Deepseat still as stiff as I remember it being in the past? If so, this could be adding to your issues, and you may want to consider a softer seat.

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Sounds like my 2022 crg kt5. It has had a hopping problem through this season.

I have experimented with moving the seat back and forth 30mm - didnt help. Balance changed but the hopping didnt go away.

Track width changes at the front didnt help.

Running with seat struts made the hopping worse - felt like the strut is going to pierce my torso

Front ride height to max made positive improvement in over all grip but not to hopping.

High rear tyre pressures reduced the hopping but made rear tyres eventually over heat.

I am running stock medium axle - have tried two different width rear hubs. No help. Rear is at max width as reducing the width made the kart hop more

What took the hopping away was installing another set of snipers and taking almost all the caster out. There are only two lines left at the bottom

For me the right amount of caster was found while driving around the corners as fast as possible on the limit of adhesion and looking at the steering wheel. The fast line is there but I am over here - is it possible to steer a little bit more so I can get over there without the rear stepping out - Does the rear brake away if I turn past a certain point. I observed that in all fast corners the kart would only take so much steering and after that the rear would step out. So kept reducing the caster until I could be on the line I wanted and the rear wouldnt step out

I have the eccentric on top, nothing adjustable on the bottom. Been thinking it would be a good purchase to get the bottom. Camber gets all messed up when I can only adjust caster with the top. But for my kart currently, yes, I had the top arrow pointing back. It felt like I lost the front end but iirc, it was only one session and I put caster back in. Should I take caster out and try other front end adjustments to compliment?

Yes. I’ve run 55" only. Haven’t narrowed at all other than for rain.
I’m running the factory magnesium hubs. I think they are somewhere around 90mm? Ive tried longer aluminum hubs. Can’t really tell a difference.
Front ride height all the way up and down - down freed up the kart in general, but didn’t have an effect on hopping.
Rear ride height in middle position and chassis down. Down always feels better.
Seat struts on and off. At times I felt like it helped to take them off but other times with them on, I had the fastest lap so I’m really confused with the seat struts.

@Rdub3 ah gotcha. This is a good thing to note. The horseshoe and double right handers are where I’m losing so much ground but coming out of turn 2 (our lowest speed corner) my kart doesnt get too upset and I gain a lot of ground on my competition.

Will do! You guys don’t do a “try before you buy” program for seats, do you? lol

I don’t know if I’m the best one to answer because I don’t have a lot of experience with seat stiffness but it feels relatively flexible compared to the old seats I have around. Not sure.

I feel like we have the exact same issue. So you’d recommend I get an eccentric pill on the bottom of my spindles so I can take more caster out? Or like @tjkoyen said, they make even more extreme pills.

Man I don’t know, this last race, the leaders in the masters class were only a tenth slower than me and they have 30 extra lbs! But the real positive is the masters class has 4x more karts to race with so there’s that.

Sounds like Mikko had good luck with double eccentric pills to remove even more caster. That’s where I would go next. It’s also just good to have that extra set of eccentrics to fill out your arsenal a bit more.

I would leave the struts off. On our taller drivers in anything lower horsepower, they seem to prefer with it off. Echoing Mikko’s notes; some have noted that they just felt like they were getting pummeled in the ribs with the struts on and the kart was just chattering across the track like it was too stiff.

I would also look at a more laid back seat.

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Is the laid back seat approach purely to lower your center of gravity relative to the rear track width?

I’d try to decrease the front ride height as it’s overpowering the rear.

Austin I would buy the extreme caster kit - just as TJ said - It never hurts to have a lot of tuning options :+1: I wouldnt have known that the hopping goes away if I hadnt had a spare sniper kit and tried it.

Keep an eye on your toe out settings when changing caster - they need adjusting back

Tyler - I tested the front at every possible height and found out that the front up I could drive faster. I was thinking before testing that the lowest height would be the fastest but low ground clearance just didnt give any good effects. It just forced me to start lifting as front wheels were coming off the ground in places where lost of contact is a bit do or die situation

I spent most of the summer thinking that I am binding the chassis in the corner and that makes it hop.

I tried various front widths, short hubs, long front hubs that were spread out

added caster to max

I tried different front stabilizers to make the front more rigid so steering input would make the kart 3 wheel in the corner.

The right solution was making the kart stay flatter - more on 4 wheels. The same worked on my previous kart - road rebel. Road rebel didnt hop - if it hopped it was very mild compared to kt5 - it just liked to slide. I couldnt transmit power to rear wheels. I slipped and slided through one season - tried all the things harder rear axle, hubs, seat position etc but not one them made a real difference. Then I noticed caster kits being sold to tony karts and figured heck I might as well try that too. I will add another sniper kit. My lap times got better and better the more I took caster out. Made my lap record with all the caster out

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