X30 balance

Chassis Setup, Tires & Handling Forum
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Hey all, first time posting here.
I’ve got an x30 on an older merlin LM30 (2010ish) chassis I’ve been running for fun at NCMP. MG Yellow tires. I’m 6’1" 170lbs with gear on.

I’ve been having a blast just running laps with my brother and this winter I’ve invested some time into getting the kart into a better baseline. The frame had a bit of a twist which is now straightened and the seat position when I bought the kart was a bit wonky, as in not flat with the bottom rails, tilted forward quite a few degrees. Handling was affected by these things I’m sure so I’ve repositioned the seat 620mm back from front rail and flat with bottom of frame rails. Seating position is now very comfortable for me as I also moved the pedals forward more and with the seat at the right angle (Tillet T11) the distance to the steering wheel seems more natural.

My uncle loaned me a set of scales and with brand new tires, proper laser alignment, equal tire pressures, level ground and full gear, no lead and a 60% full tank of gas I’m getting a very equal cross and side to side balance.

My question is regarding front-rear balance. I’m at 41.5% / 58.5%. From what I’ve read on here this is within a decent window but I also see a lot of comments about 43% front. If I fill up the tank all the way to the top I’m close to 42% but that’s about it. I’ve also read that being tall, a little more rear bias may be ok as I have more weight transfer to the front when on the brakes.

If I were to race I would need 5-10lbs of lead to make 360-365 also depending on fuel level. I understand placing weight up front, far from the center of the kart is not too ideal due to inertial moment of that weight during turn (my terminology may not be correct here sorry). I could also get a longer chain to get the engine further forward. I’m running a 104l right now. But would it matter or do we think 41.5% is close enough or even more ideal?

I like to tinker, I’m just doing this for fun, but would like a good baseline so I can focus on driving and proper tuning within a decent window.

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Your weight distribution is fine for your height and weight. If you need to toss on weight, I would put it on the steering fork in front just to get a little more front-end, but you’re in the ballpark and I wouldn’t stress about it too much. But it’s pretty common to run ballast on the front steering fork. Nearly everyone does.

As someone who won a lot of races on the LM30 in '08-'11, I can tell you we always ran about 5-10 pounds on the front fork and aimed for around 42.5% front weight (I’m 5’7").

Also here is the tuning guide I wrote for the kart back in 2010:
Study of Merlin Racing Kart and Tuning Characteristics.pdf (617.9 KB)

Some of the items in there are a little outdated and probably not as accurate (after 14 years of more learning I would change a few things), but overall I think the theories presented are pretty sound and tried and true. Jamie has mentioned he wants to change a few things as the karts have evolved but for a kart from the period it should be a pretty close generally.

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Thanks TJ. I actually read your guide a couple times already and watched some of your fundamentals videos. Very useful.

Appreciate the feedback, I’ll just run it as is for now knowing where to put weight if I need to in the future.