OTK entry Loose\Oversteer sliding issue. I'm lost!

Chassis Setup, Tires & Handling Forum
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Hi, great forum.
I have had my 2013 OTK X30 for 18 months now after a lengthy absence from karting.
I have been plagued with corner entry oversteer or sliding. It feels like im driving a hammer, as the rear starts to rotate past the fronts trajectory. The rear won’t bite or grip like the front. The slide starts from very early entry with brakes locked up or not. This is on fast and slow corners. It requires the slightest turn of the wheel to initiate. It requires a lot of concentration to be so slight of the wheel it gets very tiring.

I loose time through the whole corner due to the slide as I can’t get back on the power early. I watch as many similar classes as I can. I notice the fastest karts grip well in the rear, just unloading the inside rear enough to turn in well. They look so much easier to drive that way too.

I have tried moving the seat back, forwards, up and down. I have had to fibreglassed it up three times because of the holes.

I found a H axle give slightly more grip that the N which I continue to use. I have tried all front end adjustments including ride height, toe in/out.

The inside 1/4 of the rear DFM tyres chew out in a couple of meetings while the fronts show hardly any wear. I had a theory the rear was not lifting just flat sliding causing the inside chewing of the tyres. I now have my seat back at the local OTK shop recommended position just 2-3mm higher.

I find max caster helps the rear bite on entry.
I am thinking of going for a softer Q axle to see if i can get bite.

It has always taken half race distance to start griping up well enough. I often do my fastest laps at the very end of the race.

Im lost at the moment and loose all motivation with bad results. I am contemplating a
different make of chassis now.
Any suggestions greatly appreciated.
Thanks.

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Hey @Bmarshall, welcome to them forums! There are a lot of great people on here.

First and foremos, I know how it feels to be completely frustrated with Karting setup. It sounds like you’ve actively tried working on the problem, including moving the seat and changing axles, which is much more committed than many racers are before they consider throwing in the towel.

Without watching you on track, knowing your region, or even the tire you are running on, it’s a little hard to make a concrete judgement. However, here’s a few things to consider to start:

Are you racing at tracks that rarely gain any rubber? If so, the kart may simply have way, way too much front grip (tonykarts especially are very “front positive” out of the box even at factory settings).

What about the weather? On a cold track, karts can be frustrating to drive. Even with a great setup, if you don’t compensate for a cold track with higher tire pressures, this could be a reason why your kart takes a while to come in during a session. If you are out at the track next time, even without a temp gun, just place your hand on the ground in the pits. Even on a relatively sunny day in some regions you’ll find often from morning to mid day many tracks/pits will be cold to the touch. If this is the case, karts will struggle at normal pressures, as the track temp is not up to where it needs to be (ideal conditions are 80-120 degrees track temp). While ambient temperature affects this, it’s really much more a factor of how much sunlight the track gets, due to albedo and fun things like that.

I touched on tires a moment ago. Are you racing on a relatively hard tire, or a soft one?

Setting aside most of the things you’ve tried so far, and going on the info you’ve provided in your post, I suspect if you are consistently loose on corner entry, you may want to consider tinkering next with your ackerman. If the kart feels very twitchy on corners entry often this is an ackerman issue in addition to other issues. To make the steering more lazy, you can move the steering shaft bolts “upward” closer to a position near the actual shaft. A narrow front track width can create a similar issue, and will also limit mechanical jacking and lift. Similarly, a narrow rear track can make a kart super sketchy under braking, even if it has ok grip in the middle of the corner.

I’m excited to hear some more info from you, as I suspect together you and the KP forum people can help you find a way to fix your handling issues.

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Ditto to everything Eric said. If the oversteer is happening immediately on turn-in, it sounds to me like you don’t have enough outside rear tire bite.

I take it you moved the seat up to get the kart to tip more and get the outside tire to dig better? If caster and raising the seat helped, that tells me you need more weight jacking to get the rear to dig in. Two things that I would try would be raising the rear ride height and narrowing the rear track. We’ve found rear ride height to change the balance a lot in a kart that is struggling with side-bite.

What front bar are you running as well?

It also could be a driving style issue. Although it’s rare, we’ve had a couple drivers who were very harsh on the wheel, to the point where they constantly complained about the front having too much grip, regardless of what changes we made. The only remaining adjustment we could make was to completely remove the front bar which is basically unheard of on an OTK kart. But it worked, the driver instantly felt better about the handling. Worth a shot as a last resort.

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I have two questions…

  1. Is this a new thing for you with this kart and tires, or have you had it from the outset?
  2. Have you scaled the kart?

…After re-reading your post a couple of times. I’m almost thinking your chassis might be cracked or out of square. You shouldn’t have to work THAT hard, I can understand your frustration.

Do you have a video you can share with us?

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IMG_1427IMG_1426Hi guys,
Tyres are DFMs. Tracks I have only driven two so far but I would rate grip level as medium to medium-high from other drivers information. It has always had heavy steering compared to karts I drove as a teenager, that was on hard SL tyres. It took a good 6-9 months of racing and practice to calm my driving style down from the heavy steering.
I have tried akerman and front bar in and out.
The kart does respond to changes as in slowing the turn in rate and increase in some rear bite, however the sliding or oversteer from entry through to exit is still significant enough to wash of speed. I don’t think it is binding as I don’t feel bogging or sapping of power due to high grip. I have tried to change different styles of braking and turn in phase but these and setup changes don’t make enough difference in the rear grip/bite.
Seat dimensions are 640 from front bar to seat front lip and 220 from axle to rear seat lip 3mm above bottom of the frame rails as per otk dimensions. I am 74ish kg

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I think at this point, the more you describe it the more I would be curious to see if the frame has a crack in it. I know a friend of mine had a similar issue to you in terms of trying everything he could think of in a shifter kart at Lancaster this year, only to find out after the weekend the seat strut support on the right side was fractured. I think it is very premature to jump to that, but the fact that things only seem to kind of work on medium to high grip tracks makes me suspect it’s worth at least looking.

As James said, a video of you driving would help a lot.

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So, I don’t have as much experience or knowledge as the other guys here, but this last year I struggled with tuning on my '12 Kosmic. I could never feel the kart as well as I noticed I could in other drivers karts.

We knew through the year that the frame was fairly worn, it cracked countless times over the season and I would say that had a large part in it. Check every weld on the seat struts, and in the middle frame rail, where the rear crossbar meets it. Those are where my frame had cracked all year, so those are likely the places you would want to check among others.

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Listen to Aaron his kart has been named the kart of a million welds. If anyone would know it would be him.:+1:t2:

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Thanks. I have not noticed any cracks but will check all weld areas a bit closer then.
Cheers.

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Hi Ben
Are you based in Australia (assumption from X30 and DFMs?) if so i know lots of guys are running 17mm front stub axles in the otks to calm the front down this seems to help with the balance in restircted and KA classes.
Cheers
Michael

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Hi Michael, yes.
I have not seen any OTKs use the 17mm stubs yet that I’ve noticed.
I’ll keep it in mind.
Cheers.

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Hi Ben,

check out the below link
http://www.tonykartaustralia.com.au/tonykart/set-ups/Downloads.asp?whichcategory=10&AreaID=16&sortorder=Alpha

i always found the DFM HST set up pretty close in KA Medium in a 2014 30mm otk so it may be of some help to you.

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Ok. Thanks Michael.
I think I will try the softer Q axle and do back to back tests with the N and H.
I will post my thoughts afterwards.

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Ben,
Did you notice in the link Michael posted that shorter than normal rear hubs were suggested. I would think that the shorter hubs would give you more axle deflection between the bearing cassette and the wheel resulting in more rear grip.

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Do you know the history of the frame before you bought it? If setup changes don’t affect how the chassis reacts the frame could be plain worn out. Re-framing is a cheaper option than a whole new kart.

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Hello! Welcome! Definitely try a different axle. Have you tried a softer seat? A softer seat could give you more grip in the rear and more overall chassis flex. Just a thought.

Cheers

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Ive been back to the track to test seat position. I fitted the N axle back and the rest otk recommended settings. I reset the toe out as it was too much which may have attributed to the sudden oversteer.
I found the kart to be best overall balance when the seat was forward as it felt better in the rear than the seat back. I think the tyres were over working maybe when the seat is too far back.
I tried the forward position below the bottom of rails and just above. The high position did have a sturdy rear on entry but mid and exit didn’t come off the corner so well. The lower forward position felt best through the whole corner and in the braking zone. The seat is about 625mm from front bar and 225mm axle to top of the seat with 3-4mm below rail.
The front end still feels extremely positive and steering still heavyish side.
I feel I can push harder with the better rear but still have to be smooth and can not really lean on it as it will slide too much.

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Thanks for reporting back

Can you take some caster out?

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Hi all,
Im getting better rear stability on corner entry and braking the wider I make the rear track. I am at max legal 1400 now. I find the steering even lightens up and less darty the wider the rear is. I have 1 small spacer on the inside front stubs, will try going wider.
Is this handiling trait normal for a wide rear track? I still experience mild oversteer that is slowing me down mid and exit corner.
I was always under the impression a narrow rear is better for rear grip.
I am thinking now a softer axle is maybe the way to go for less oversteer.

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Like anything in karting, narrow rear track gives more rear bite, up to a point.

If you go too narrow, it’ll become so reactive on turn-in, that it’s over-lifting and causing handling woes mid-corner. Wider is better for overall stability.

I remember a specific instance wrenching a few years ago for a junior driver… He was getting faster and faster the narrower we went on the rear track, but it got to the point where he could no longer be consistent and the kart was just unstable at that width. We widened the whole kart out and he was able to be much more consistent and basically just as quick.

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