Hi, I am driving a 2021 Birel AR29 LO206 and I am struggling to keep up with the competition.
When I follow others in my class, I notice that at turn in I loose speed and positions. Further on I loose speed in fast flat out corners where my kart seems to bind.
It seems like my Birel has a lot of rear wheel traction and I overdrive the front tires, which also wear out quicker then the rears (MG red).
A lot of others in LO206 (senior) have 2 stroke chassis with 50mm axles and for some reason I feel these chassis are driving better through corners. I came across the topkart webpage and found a very interesting driving technique section.
Anyone who has a TopKart can give some feedback?
Here is the text.
As compared to many other chassis brands, Top Karts have very powerful turn-ins. This means that in most cases, drivers will experience corner entry oversteer as opposed to corner entry understeer. Top Kart chassis maintain their front-end integrity much better than most other chassis brands, and this makes Top Kart a formidable contender on race days. Many drivers experience primarily a sliding of the rear of the chassis on practice days and see their Top Kart only get better as the weekend progresses. But, as is the case with most forms of motorsport, every driver is a little different and their style impacts the drivability and conformability of their Top Kart Chassis. Let’s give you some helpful hints on how Top Karts prefer to be driven.
Loose hands, loose hands – A light, comfortable grip of the steering wheel is often all that’s needed to corner in a Top Kart. Minimal steering input (as minimal as possible) increases the efficiency of the Top Kart’s rolling speed and stabilizes the chassis through the duration of the corner. Of course, this all depends on the proper setup and alignment of the front wheels.
10-15 degrees will do please. In dry conditions turning the steering wheel more than 15 degrees makes for inefficient cornering on most chassis, and staying within that degree limit is difficult to do on a consistent basis. What will help Top Kart drivers work within these parameters is to slow the turn in rate. Of course, an adjustment may need to be made on where to initiate the corner, but slowing down the speed at which the steering wheel is turned will certainly both increase the stability of the Top Kart chassis, as well as make the corner more predictable, lap after lap.
A wet exception – In damp or wet conditions and especially when racing in the rain, massive amounts of steering input are usually necessary, as long as you stay off of the brakes and throttle while making your corner. Turning the steering wheel to such an extensive degree will also help continue the deceleration of your Top Kart, so you may be able to increase the approach speed to the corner, allowing the steering wheel to do some of the braking for you. If you are finding it difficult to remember this technique, think of it this way: Top Kart loves to do one thing at a time, whether it’s accelerating, braking or steering. Any combination of the two may result in less-than-desirable handling.
I think chassis drive differently, but I wouldn’t jump to a different chassis entirely just yet. Plenty of people are fast with the AR29 in 206, and there may be adjustments to get that feel you’re looking for.
Have you played around with different ride heights? Could also try a different axle to free up the rear, and different hubs as well. I know @StahlRacing has a lot of experience with Birel in 206 so maybe he can guide you on how to address it specifically. I will say it’s a common consensus that OTK has more front end grip and turn in than Birel.
I’ve driven an AM29 for a few years now, and would be happy to chip in some setup advice for it. I had similar struggles to what you are experiencing, and it’s very likely it can be turned around! Do you mind answering the questions below? Also, I included 2 of our baseline setups, in case it can help you.
Your height and weight:
Track you race:
Now to get a feel for your setup. Which front bar:
Front spacers on the inside of hub:
Front ride height:
Toe:
Camber:
Axle type:
Rear wheel size (210 or 180mm):
Rear hub: stock 75mm?
Rear track width (edge of tire to edge of tire measured through axle):
Rear ride height:
Seat struts on?:
Seat:
Here is my baseline. I’m 6’4 and 190lbs
Which front bar: Chrome (stock bar)
Front spacers on the inside of hub: 2 (2 big spacers each side)
Front ride height: Low (both spacers on the bottom)
Toe: 2mm out
Camber: 0 to 2mm positive
Axle type: Freeline f2.5 (hardest)
Rear wheel size (210 or 180mm): 210mm
Rear hub: 40mm PKT short hubs
Rear track width (edge of tire to edge of tire measured through axle): 50.75"
Rear ride height: Low (Top hole)
Seat struts on?: Yes
Seat: Beasley CIK Laydown
My brother Ben’s baseline setup. He’s 6’ and 175 lbs
Which front bar: OTK silver (cut down to fit)
Front spacers on the inside of hub: 2.5 (2 big 1 small each side)
Front ride height: Low (both spacers on the bottom)
Toe: 2mm out
Camber: 0 to 2mm positive
Axle type: Stock Freeline B
Rear wheel size (210 or 180mm): 210mm
Rear hub: 40mm PKT short hubs
Rear track width (edge of tire to edge of tire measured through axle): 50.75"
Rear ride height: High (Bottom hole)
Seat struts on?: Yes
Seat: Stock Freeline
Hello Kacy,
thank you very much for the response and I really appreciate the feedback including your setup info.
Below my setup
Your height and weight: 6’1", 175lbs
Track you race: Stockholm , MN
Now to get a feel for your setup. Which front bar: stock Birel round, steel
Front spacers on the inside of hub: 2 thick+2 thin, 30mm
Front ride height: middle, washer top and bottom
Toe: 1mm out each side
Camber: +2degree
Axle type: Started with B Freeline, now soft Righetti Ridolfi 1040mm
Rear wheel size (210 or 180mm): 210 Freeline MG
Rear hub: stock 75mm? yes Freeline
Rear track width (edge of tire to edge of tire measured through axle): 1355mm, 53.25 inch
Rear ride height: low, top hole
Seat struts on?: yes 1 each side
Seat: Firrst Freeline, now Ribtech Fiberglass
I have to add a few things:
With the stock axle width, about 1300mm (51inch) Freeline B 1000mm and the stock 75mm hubs I had bad hopping in the rear. It was so bad that my ribs started hurting. After some research (a friends setup sheet and an arrow owners manual) I moved the rear out to over 53 inch, anything below 53 and its hopping in fast corners.
Maybe if I go really small in the back, the hopping will go away again? I have not tried that.
One time I had mild to none hopping at 53 inch rear width and removed the seat struts which connect the seat to the bearing carrier. The kart was undrivable due to extreme hopping. I tried a medium axle because we thought the rear could use more stiffness and that did not work either, hopping was bad.
I am not sure what rear width others are driving at the track but I try to eye if the rear wheel lines up with the bumper, and it is similar to my kart on the other 40mm rear axle karts.
BTW we have many 2 stroke chassis in the 206LO senior and junior. Right now it looks like the grass is greener on the other side of the fence.
The hopping is not the big issue any more since I went wide in the rear, but I have been struggling with turn in and loose a lot of speed in fast corners. My son and I compared AIM data and he is in his junior kart as fast in the fastest corner of the track because my kart slows down so much there. These fast corners are the locations where other people catch up and pass me shortly after.
I am tempted to try narrowing the front to get a rear tire into the air, but per the book this makes front end grip worse?
Also lifting the rear drive height should work to help with rotation at corner turn in?
I will try a few things next weekend, this discussion definitely made me think about a few more settings+ driving style.
besides what I wrote in my other post I moved a 5 pound weight to the front of the gokart. I usually keep the tank 1/2 to 3/4 for weight reasons.
Moving the seat forward…I hope that is not needed with my long legs. But maybe this might be a good tip. I also have to put the kart on scales to see the corner weights.
Other things I tried are torsion bar with and without, I changed front width slightly but maybe I need to go more extreme, no spacer vs. 30mm worth of spacers.
I drive a birel in dd2 class. One thing i can confirm is that hoping in the back. Mostly it comes from smaller rear width or too hard axle i experience that on the standard f axle. But its only in high grip conditions. But it occurs only in slow tight corners or very fast 90 degree corners. I went for shorter hubs or or tried also the r axle and it was better. Buuut i havee to say i like it like this. Had a tony before, it was pretty loose. With the birel i am alot faster and more confident. This small hoping i could also control by adapting my driving little bit.
But to say it happened for me only on high grip conditions.
You’re 6’1", so you’ve probably got the seat well back. That’ll put a lot of weight on the inside rear tire in corners, and cause understeer. You’ve probably got good traction and can outbrake people readily, right?
If you can, move the seat forward to get weight off the inside rear at all times, up a bit too if possible so it takes more weight off the inside wheel under braking and cornering. As a guess from your description, try two centimeters forward and one up.
And also what i can tell birel does not like to have the seat too far in the rear compared to the other Chassis i drove. the position of the official chart nailed it
Dimitri and Charles, this is a great suggestion. I will check out the Birel seat setup sheet and move my seat there. I think I have a little room to play with.
Thanks for all the awesome feedback.
Edit: put the bathroom scale in use today and my son and I build up a great setting with some 2x4 studs. At absolute level we found the kart+ fuel+ me to be at 43/57%. That seems to be decent. I will for sure do the rake change and the other suggestions mentioned above.
Not much left in the seat position, otherwise my knees will interfere with steering.
I assume that the am chassis has quite the same size like a normal one? I am 5,95’ and i have plenty of room in my Chassis. Maybe you could post a picture with you in the kart? And what type of seat are you using?
I would be very interested to see your seat position. That could play a big role here as well. If you can send a pic of your seat positioning that could be helpful . As @CrocIndy said, 53" is far too wide for the AM29. We rarely deviate from 50.75". Also, the soft axle probably needs axed. It looks like your issues really boil down to a bound up kart. I think the soft axle is making this even worse. Thats because the AM29 is a very soft chassis, so a softer axle will cause it to flex even more and lead to binding. The AM29 is opposite from a lot of other chassis’ in this way, soft axles add rear grip and harder axles free up the kart. The good news here is you are running the kart about as soft as you can get it, so there should be lots of room to stiffen / free it up!
Here is what I think you should try for a baseline setup next time you are at the track. The setup uses only stock parts. If you’re up for it, you could pickup a Freeline Hard front torsion bar to use. Stiffening the front will add front grip and free up the rear. It’s around $50 from PSL, and is a very helpful tuning tool. It will definitely free up the rear of the kart more than the stock bar
Front bar: stock Birel round, steel (chrome) [Ideally use the Freeline Hard bar]
Front spacers on the inside of hub: 2 thick+1 thin, 25mm
Front ride height: middle, washer top and bottom
Toe: 2mm out each side
Camber: 0 to +1 degree
Axle type: Stock B Freeline
Rear wheel size: 210 Freeline
Rear hub: stock Freeline 75mm
Rear track width (edge of tire to edge of tire measured through axle): 50.75" Use the plastic insert in the hub, and butt it up against the edge of the axle.
Rear ride height: low, top hole
Seat struts on?: 1 each side
Seat: Ribtech Fiberglass
If you do try this, please let me know your feedback. If this takes you in the right direction, then there are more things that can be done to stiffen / free up the kart more.
I would definitely try to figure out the setup of the Birel before switching. I have heard from people that the Birel tends to drive on the nose more than most chassis though. Personally I drive a Merlin which is similar to a Topkart (correct me if I’m wrong) and the rear likes to do more of the work which isn’t always great in the 206 since sometimes the sliding scrubs speed. Overall though I love how it handles even if its a bit twitchy sometimes. Plenty of people are competitive on the Birel however so try to work on the setup to iron out the issues.
I’m with David, I wouldn’t jump to a new chassis until you’ve exhausted every available option on your Birel. Birel make good stuff and there are lots of fast guys running them.
