New guy intro with autocross questions


(Ji Simmons) #1

Hi there, ladies and gents. I recently picked up my first kart, an '05 TK Krypton 125cc shifter. I know, I know… shoulda started in an LO206… but please hear me out here.

I’m not new to racing or driving extremely high performance vehicles in hill climbs, road courses and autocrosses, and I have enough experience to know to take it easy as I learn the machine. I have no delusions of going out and winning any races against any karters and fully understand that if I tried to hang with the fast guys, I may very well get hurt or hurt someone else in the process. Additionally, because the local racing org couldn’t manage to negotiate their contract with the only kart track in the state, it looks like wheel to wheel action is dead in the water until they figure something else out. And so, I turn to autocross.

I’ve had the kart out a few times in the parking lot at my work, which is pretty smooth and bump free, but still managed to grind the frame at the front and just behind the waist. I had an experienced karter look at it and he said it’s not a concern all things considered, but advised to gain clearance and/or add some skid plates so it doesn’t get worse. I have some skid plates on the way and moved both shims above the spindle. He also suggested possibly running more tire pressure or a slightly taller tire up front. The kart currently has MG HZ (not HZ-i) tires on it, and since a 40- 50 second autox course won’t give me any time to build heat in the tires, I have a set of MG YZs on the way.

But his comment about a taller tire got me thinking… What about running rears on the front as well? It’d give me an additional half inch of clearance up front. I test fit one of the spare rears I have and it does clear the caliper and produces a 53" width measured from the outside edge of the wheel (the rear is 55").

What are your thoughts on running rears up front? Keep in mind, I’m not bound by any club or sanctioning body rules regarding tires and my competition will not be wheel to wheel. I’m not even worried about getting FTD; I really just want to go out and have some fun without destroying the kart in the process. Can you think of any harm or grossly increased wear that’d be incurred with this setup? If not, is there any advice on caster/camber/Ackerman that I should take? I did google this subject with no luck prior to coming here and posting but if I missed something and this has already been covered, I would greatly appreciate a link pointing me in the right direction.

Thanks, and I look forward to learning from you all and being a part of this community. :slight_smile:


(Dylan Paddison) #2

Not that I can comment from an informed/analytical point of view, but I can think of a few reasons to give this a go.

  1. You’ll need another pair of rear wheels, which you can keep around for rain tires.
  2. You’ll have a spare set of rear tires.
  3. Experimenting is fun.

You might go faster. You might love the way the front feels. You might absolutely hate it. Who knows? Either way, you’ll be spending money on useful consumables. Autocrossing a shifter sounds like a laugh. Good luck out there.

Also, get a rib protector if you haven’t already. Experienced driver or not, even slower kart classes are very physical compared to cars, and your ribs have to handle a lot of force. Rib protectors are worth their weight in gold. I’ve had the Armadillo for about a year and a half and it’s holding up wonderfully.


(Ji Simmons) #3

Hi Dylan, thanks for the reply. All good reasons, however here in UT, rain doesn’t really factor in. There may be a wet day or two in the early and late parts of the season but as I’m not out for points, I can just skip those days. But otherwise, I absolutely agree with having a spare set of rears if I don’t like it and from that standpoint, there is no risk.

I do have a rib protector. Safety is very important to me, so thank you for mentioning it. Prior to a few weeks ago, the last time I was on a shifter was back in the summer of '05 at some track near Montreal, Canaderp and I didn’t have a rib protector on. I can’t recall much other than being extremely sore in the ribs for a few days afterwards and coming away with a great deal of respect for the brutality and violence that these things are capable of. Sliding around the lot at work on cold, hard tires a few weeks ago brought a lot of those memories back.


(Dom Callan) #4

Now that you mention it, how do you deal with cold rubber in autocross kart? Not run slicks?


(Ji Simmons) #5

I was advised to just get the softest tires I could find, so I got MG greens. Maybe there are softer slicks out there, and I guess rains might be softer still? Even on cold MG reds, I had a blast and could tell it will be considerably quicker than anything else I’ve ever piloted through the cones, especially with the greens.

Warmers were suggested if I was really serious, but I’m not and I don’t want to buy and drag a generator and warmers around for what will probably end up being a total of about five to ten minutes of seat time dispersed throughout the day per event. Yeah, that’s barely one practice session at a kart track, but unless I drive seven hours to Vegas or to Denver, that is literally the only option for a timed event I can drive the kart at, and the only other option for any seat time at all is at work on a Sunday.


(Dom Callan) #6

Now that you mention in, the rain compounds are super soft. Worth a try but they will get hot fast on dry pavement. What about treaded non-race compounds?


(Ji Simmons) #7

You mean the ones used for dirt ovals? I’m new to all this, so I’m the last person to ask. Are they softer than soft slicks, but harder than rains?


(Dom Callan) #8

I was thinking more along the lines of normal car tires. They perform ok cold but don’t do so great hot. One would think that sort of tire exists for “fun” karts.

Could one of our dirt oval people chime in in what sort of compounds they use and wether they make any sense cold, without the tire prep?


(Matt Martin) #9

The main reason is that most modern kart chassis have been designed with spec tire sizes. Give it a shot, if you like; but i’m guessing you will have a ton of tuning work to do, and at the very least you’ll need to proportionally increase rear tire sizes to maintain the balance.

i would suggest reading through a few books on kart chassis tuning and vehicle dynamics books to understand what ride-height changes do, what tire-size changes do, how it might affect the various aspects of the kart.