Birelart AM-29 tuning - 206 Heavy and Reds

Looking for suggestions to take grip AWAY from the AM-29 when running reds. 2021 MG or Vega Reds proved to be a challenge last year with the kart being stuck to the track. Went through every combination of axles, hubs, wheels, psi, and torsion bars, but struggled with hopping and bicycling all season. Same issue with 2019 and 2021 chassis. Anyone in 390# class have suggestions to combat this problem?

Any proven recommendations for a heavy class chassis?

As you already know, you are fighting an uphill battle. I wont even begin to try because you have already done all the things i would suggest.

On the 2nd part, I think you really only have 2 options in the “heavy” 4 cycle world. Comet Eagle or MGM Espionage. Don’t buy anything Birel based (Ricciardo, Comp Kart, Le Clerc, Birel) or OTK based (Tony, Red Speed, Kosmic, Exprit, plus like 5 more they added this year) because you are starting from behind again.

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Thanks Derek, we’re on the same page. It’s amazing the difference a tire compound and 25# can make in a kart.

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Sounds like you’ve tried everything I’d sugguest. Maybe someone with more info will answer up.

Just curious, are the reds a lot softer than blues?

Did you try moving the seat around at all?

If you’re familiar with the Flintstones, pretty sure they they used MG Blues as OEM tires. Rocks.

Blues are designed to last a long time on rental karts. On “pro karts” it’s not uncommon to get 2-3 seasons on a set.

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Sign me up. That’s amazing durability.

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Thanks James. We did play with seat position. Even with more weight biased to the rear, the better result was back a little compared to where we were previously.

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Up here in Canada, Briggs national class runs Vega Blues almost exclusively as do most of the clubs. I think we run reds in 2 stroke classes.

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I’ve never bought new tires for my son’s cadet kart, everyone I know running club level 4 stroke up here just buy used Blues and run them for a year or more.

Buy an Eagle, put on baseline setup, go fast everywhere on any tire.

Is the Eagle metric?

Tim Shutt seems to make the Compkart 4R work well in Masters and Legends.

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Yes, metric tubing. 17/40 spindle/axle

I don’t have “proven” recommendations but I wonder if you are beyond the useable range of weight for that chassis. If the chassis is a spring but you have to much weight will the spring work as intended? I would guess the 29mm chassis is intended for 365 or less.

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That’s a fair point. Our local club is LOADED with Birel karts, and now that you mention it, the AM29 is popular in Jr, but quite a few Sr and masters guys run the RY30 2 stroke chassis in briggs.

Jim and Robert, I believe you are on to something there. (the AM-29 is 28mm & 30mm tubing.) However, 2-3 years ago, with the exception of a few Eagles, the AM was a front runner in Sr 360 and Sr Heavy 390.

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I love my AM29 on low to medium grip tires. High grip tires it’s definitely a challenge to remove grip.

Definitely run the front bar and seat struts. Go low on pressures.

Have you tried adjusting the ride height or wheel base at all? Those two changes should make a significant difference for high grip tires.

With that sticky of a tire, it’s going to be tough. A thought would be to stiffen the front and rear of the chassis and keep the middle as flexible as possible. For the front, lower the height, take out all of the caster and use ackerman (this should help the kart release off corners) and play with front bar stiffness. For the waist of the kart, you either move to a supersoft seat or float it and keep it as low as possible. Rear, smallest rear hubs you can find, HH axel, struts (maybe), raise the axel, etc… outside of that, it would be a driving style change