I am looking into purchasing a kart for 206 racing. As I have looked at many different chassis I have noticed that majority of the 4 stroke specific chassis are a mix of 28mm and 30mm tubing. What advantage does this offer over a more traditional 2-stroke all 30mm chassis? Does driver size play a role as well? I am 6 feet and weight about 195lbs.
To give an example of two options I am considering, would a Birel Am29 (4 Stroke Specific) be better, or a Birel R30? I will also add that the track I will race at runs MGIR (very hard) tires.
Mostly what I see in 206 is softer frames, because the engine doesn’t have that much power. So the frame needs to be softer, so it can somewhat jack and move around properly. That’s why you normally see older frames that have been used, or smaller diameter tubing.
Quick answer… Unless there’s a compelling reason to not use the AM29, it sounds like a natural choice without knowing your situation on budget, price, condition etc. Also, if others are running the AM29 in the 206 class then it’s easier to compare notes too.
Longer answer: You’ll find people have been able to make almost any kind of chassis and axle size work. The four stroke specific chassis usually have two main features: 1) Lower price point, 2) More clearance between the right side. Beyond that there’s some differences sometimes like a 40mm axle vs 50, but again, like I say you’ll see both types at the front of fields.
The problem with grouping a chassis as “stiff” or “soft” based on frame rail size is that there are other factors that affect load transfer and spring, arguably more. Material, wall thickness and of course tube layout make a big difference too.
If you want to geek out, here’s a good topic on four stroke chassis (As much as I dislike the term )