How about another Ask TJ?

[Justin Martin]

Well TJ, I read your post on moving the seat forward and how you usually ont because your seat weighs 60 pounds... If you ask me, it sounds like you might have a similar build to myself.

I am 5'7" and weigh 135+/- (Light, I know). That being said I have 55 pounds of weight on my seat to ensure I meet weight.

I balance 50/50 left/right and 42/58 front/rear. To do this however most of my weight is around my hips, and the front underside of my seat. This translates to a very low CG. I am not able to move weight higher up the back of the seat or I easily jack up my balancing to 40/60-38/62.

To counter this I have been using a 1020 axle, and rear width I generally adjust between 53 7/8 to 54 1/4.

I am using the narrow width to counter my low CG and allow the inside to pick up. It seems to work okay, and I am truthfully fastest at the narrowest width.

What is your opinion on my course of action?

I guess my only other option would be moving my seat forward, so I can raise CG, then run wider width....

I am currently fastest at my local club, however I feel I have time that I can squeeze out.

[Justin Martin]

To follow up;

Racing Rotax/Tag Sr

2011 intrepid cruiser chassis, previously owned by a Gatorz/Skusa team.

The prior driver had the same, or similar body build to myself and was running a 1020 as well.

My seat is at factory position and feels and fits well.

[TJ Koyen]

I'm 5'6", about 120 suited up.

I've got seat at factory settings with 4-6 weights on the back of the seat starting at the top, one on each side, two under the front tabs, one in the center under the crotch. I've never had an issue getting enough front weight. I'm at about 42% right now. So it's interesting that you have trouble getting there if you try to put the weight on the back/top of the seat.

What you're doing sounds logical in theory. If it works, it works. My only question is why the factory seat settings make your front weight percentage so far off. The reason those are the factory recommended settings, is because that should make your weight percentage pretty much spot on.
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T.J. Koyen
OKTANE VISUAL - Custom Helmet Paint & Graphic Design
www.oktanevisual.com
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DB Motorsports
Exprit/Leopard

[Dan Haynes]

Does seem odd. We have about 35lbs. of lead on our seat with about 20-25 of it on the back of the seat. We usually keep the weight up high unless there is a ton of grip. I guess moving it low might add a few tenths of a percentage but I don't think it's enough to make a difference to matter, only the height of the weight matters.

We usually scale our kart at the beginning of the year in the garage and put all but the last 5-10lbs. on it until we get to the track. We then figure out where we need that last bit of weight and place it accordingly. We don't scale the kart again until the following year.
_________________
Blaise Haynes
#3 Arrow X1-CIK
TaG
Cook Racing Engines Parilla Leopard

[Justin Martin]

hmm. I just double checked and I could be about 1cm off, but I think because its a small seat it wont be "right" anywhere.

If I move it 1cm foreward than the rear would be too far forward, vise versa.

The rear is a tad forward, the front is a tad rearward, and the bottom is dead on.

Just curious if it is worth moving forward that little bit, so I can add weight up the rear. Currently I have 2x 5lbs weights underneath the front tabs, one 10 pound underneath the crotch, one 5 pound on the right hip, and a 5 pound as well as a 10 pound on the left hip. So it is all low.

Also, what is considered safe for hub adjustments? I have my axle marked every 5mm from bottomed out. So far my fastest times are narrow, and I haven't gone out more than 10mm each side, 2cm overall width. I was timid to go any further. This put me in the range of a 1040, and it was much slower.

[Justin Martin]

Alright guys, moved my seat forward 1/2" as well as rotated the back holes about 1". (In other words, both front and rear were moved 1/2, plus the rear had an extra 1/2" to rotate the seat more upright)

I scaled and I only changed about 1/2 a percent.

I am now at 42.5/57.5, with the 5 pound hip weight moved from the side/hip up to the top back left of the seat.

Now, the question, I would like to add 5-10 pounds so that I have a "safe zone" Currently at the end of 20 laps I am withing .5 pounds of tech, and have had to re-weigh a few times finding the "sweet spot" on the scale to meet weight. So realistically I am probably about 1 pound over, but due to scale inaccuracy I cut it close.

So, If I add the 5 pounds back to the hip, plus the 5 on the top of the back how much would that realistically change my vertical CG?... I imagine not much. So should I add 10 pounds up the back and forget about the hip weight? This would be Ideal as I would now have a 5 pound buffer, plus 10 up high.

Problem is, how much do you think the extra 5 would move my F/R cg? Considering I am at 42.5/57.5, with only 5 pounds on the back/top do you think the extra 5 (total 10) up the back would move me back that extra .5%? If so, how critical would that be as opposed to a lower CG?


I know these are kind of shoot-in-the-dark type of questions, but you all are more experienced, thus you can give me better guesstimate.

Thanks again!
-Justin

[Dan Haynes]

10lbs extra is quite a bit. We, and most racers I see, cross the scales about 2-3lbs. over. If we are cutting it too close and the kart is handling well we just add a little extra fuel. Doesn't change the % much. At about 6lbs. per gallon 1/2 gallon gives us that safety net. If we need more than that then we let the handling dictate where it goes. We sometimes will remove a 3lb'er and put a 6 in its place to get a few extra pounds.
_________________
Blaise Haynes
#3 Arrow X1-CIK
TaG
Cook Racing Engines Parilla Leopard

[Justin Martin]

Well, thats what I figured, I only want to run 5 over. I am already accounting for at least 5/8 tank fuel at the end. I usually start about 15/16 full and finish 3/4-5/8 full. So I am already high on fuel to get my weight forward, and to meet weight. Down at 1/4 tank I don't meet tech, and I am down to about 40.5/59.5%