So, an interesting theory popped up this weekend at the Texas Sprint Racing Series regarding the new weights for KA100 Sr. I know SKUSA did a full audit of the weights on the karts to determine how to drop the weights, and they said it was for safety concerns. Most people aren’t buying the safety reasoning because USPKS and other series have not dropped their weights; most of us have not seen a safety related incident involving the ballast on a kart.
With all this said, is it possible that you drop the weights low enough that you leave the “older”, or heavier, racers with one place to go, shifter class. X30 is only 10 lbs. heavier than KA, and I am sure the radiator and water comes close to that additional 10 lbs. This came up as a theory because when it was discussed on Kart Chaser’s Happy Hour, both Jake French and Race Liberante stated that they would be overweight in KA, but still have their shifter. Since the phase out of Honda shifter, and the attempt to bring about the IAME SSE (which has not been popular), the shifter class in SKUSA has not seen the numbers that they had as recently as 3 years ago.
Again, this was just a theory that started floating around the paddock this weekend.
I think that theory was floated initially as well. It makes a lot of sense to me. Trying to make the 175 work after all the investment and time. No doubt the shifter category has taken a big hit in the past few years.
Pardon my n00b-ness. Is this 345lb a max limit? I always assumed that it was a min limit but I’m getting the feeling from here that if one can’t make 345lb then you’re out?
If it is the min limit, why all the commotion? Our organization has a 340lb min limit in the Senior Briggs class. If you weigh more, no big deal, you’re just at a slight disadvantage. I’m actually in the process of dropping 15lb down to 155lb just to make sure I have wiggle room. (That and 155lb is roughly where my BMI “should be” for my height according to Health Canada)
WTF1 and Jack Aiken did a video on added weight in karts, set benchmark times, then added 20kg (44lb) of weights to their rental karts and found that it was only 2/10ths of time difference per lap… but that was on a multi-level indoor course with ramps. Jack Aiken was saying that with the added weight he had much better traction on the tyres and the majority of the time lost was the kart having to work harder on the up-ramps to pull the extra weight. So on flat outdoor tracks I can only assume that the time difference isn’t quite 1tenth/10kg it’s probably more like 5hundredths/10kg.
Anecdotally weight in rentals matters a bunch. I imagine that it varies but the fast skinny kiddos become slower as they grow. Which makes me happy. Muahahaha! 2/10 for 40lbs seems a bit on the low side but close enough. Over 5 laps that’s a second.
It’s a minimum weight and remember we are talking about a fairly high level of racing, not indoor rental karts or club racing. A minimum weight of 345 puts basically any driver who weighs more than 160 at a weight disadvantage, as they won’t be able to get down to minimum weight. No one wants to pay a couple thousand dollars and 4 days to go compete at a high level only to be 15 pounds overweight and at a 0.2-0.3 disadvantage all weekend that you can’t overcome.
The video with Aitken is misleading. A rental kart weights far more than a race kart, so the percentages are different, and the track conditions are vastly different to what you encounter in race karts. The benefit of more weight providing extra traction on a slippery indoor track might be legit. In rain situations, heavier karts sometimes handle better too. But a heavier kart will always be slower in some regard, especially on an outdoor track where it is affecting your braking, acceleration, and cornering ability. And remember that a race kart functions differently than a rental kart. The chassis is flexing and lifting the inside rear wheel, so weight balance becomes for more important.
We’ve had this discussion before:
General consensus is about 0.1 per 10 pounds. That can be a lot when you’re looking at the time charts of a big high-level race. Could be the difference between 1st and 5th in qualifying.
That makes sense. Thanks for taking the time to type it out. I’m a ‘numbers’ kind of guy so I might start looking in to recording down weights and corresponding them to lap times this summer. Mostly just curiosity.
My .02 to this. I practiced at our regional heavy weight all day Saturday which is 400 for x30.
I dropped to 365 for the race yesterday and immediately went 4 tenths faster. By the end of the day Sunday it was 7 tenths.
Now the 7 tenths I attribute more to me getting a better handle on the kart. But changing nothing and dropping 35 lbs was an immediate .3 and that is tangible in my opinion.
1tenth per 10lb?? Well then… that’s a much bigger change. Do you guys weigh out your fuel and dial in your lead like that every race day? I see some persons where their weight fluctuates quite a bit week-by-week to where it could actually carve in to this territory.
What kind of fluctuations do you all notice on the weigh scales after a race? I’m sure the higher end classes have it dialed right in and down to a science. Can’t imagine club level looking to cut grams just to get as close to min weight as possible.
You have to remember though, there’s a lot of other factors that will affect the laptimes like temperature, rubber laid down, draft, etc.
The closest reference I know of is Yamaha Jr. vs Sr. Can at my home track. The overall track records on the original track were both set on the same weekend, and Yamaha was a unique situation where the junior class just runs 50 pounds lighter than the senior class, with the same engine setup. No restrictors, tire differences, or anything. The junior time is about a second quicker than the senior time exactly, so by that measurement 10 pounds is worth about 2 tenths of a second.
The other thing to note about rentals is what TJ was saying, the karts weigh a lot more. 20 pounds on a kart that weighs 345/360 is a lot larger difference percentage wise than on a kart that weighs 600 pounds before the driver gets in it.
It’s different everywhere, but most people are scaling after every session and making a note. I don’t think people usually are counting grams per se, but trying to keep it within 5 lbs of minimum weight is my rule of thumb. That way if I lose a weight during the race, I still have a shot at making weight at the end.
I usually scale after the first two practices to see what the scales say, then I don’t scale again until before qualifying to double-check.
Maybe not grams but certainly single pounds. I want my kart with a mostly empty tank at min weight as we weigh at the end of each race. So I am usually less than 5lbs over on the scales.
Is it possible that SKUSA is pushing the lower weight in Senior to try to make a bigger speed difference between Jr and Sr KA classes? When I had run with both Jr/Sr together in the past Jr was actually faster through tighter sections of the course due to lighter weight and initial acceleration out of corners, but Senior would have advantage on longer straights. Maybe they want Senior to be a bigger difference without having to open the restrictor discussion again on Jr KA?
Either way not going to apply to me, I couldn’t make 345lb without cutting off a leg. Moving to old fat guy masters and won’t run anywhere with SKUSA rules.
That’s actually a really good idea. I was worried about that aspect myself. Don’t want to overload the fuel but also don’t want to get DSQ for not making weight. Guess I’m making a trip to the dollar store for some scales. Thanks!
