Somebody on Reddit asked how much slower they were because they weighed 40 lb more than their buddy. Half the answers said it depends. A few said a second per 10 lb. We’ve heard the same thing in the paddock, so we went and checked.
What we did
We took clean laps from our own MyChron loggers at three tracks: a KA100 Senior and a Mini Swift. The logger records speed, elevation and engine RPM all the way around the lap, so we could work out how hard the engine was pushing at every point. Then we added weight on paper and drove the lap again.
Weight doesn’t change much in the corners or under braking, because the tires grip harder as the kart gets heavier. It costs you coming off the corners. The same engine has more kart to push, so you get back up to speed a little later on every straight.
Time lost per lap for every 10 lb over the minimum
| Track | KA100 Senior | Mini Swift |
|---|---|---|
| K1 Circuit, full track | 0.14 s | 0.23 s |
| Apex | 0.10–0.15 s (depends on layout) | 0.17 s |
| Willow Springs | 0.12–0.13 s | 0.18 s |
So 40 lb over is roughly half a second a lap in a KA100. In a Mini it’s closer to a full second.
Two things make the Mini number bigger. Ten pounds is a bigger share of a 245 lb Mini than of a 360 lb KA100. And a 60cc engine has less power to haul the extra weight, so it spends more of the lap fighting it. Tracks matter too. K1’s full track has long straights and slow corners you accelerate out of, so weight costs more there than at Willow, where the lap flows.
Checking it against real races
Tri-C runs TaG Senior and TaG Master with the same engine and tires on the same day. Master is 20 lb heavier. Across the 2026 rounds at Willow and Apex, the top three Masters ran about 0.9 to 1.5 s behind the top three Seniors. That gap isn’t all weight. Masters are 30 and up, and the Senior field has some very fast young drivers. If you give half the gap to age, you’re left with about 0.2 to 0.3 s per 10 lb. That’s a little higher than our numbers, and it’s still nowhere near a second.
People who have run the same kart at two weights on the same weekend report about a tenth per 10 lb. That matches what we found.
Class minimum weights (kart plus driver in full gear)
| Class | Tri-C | SKUSA ProKart Challenge |
|---|---|---|
| Micro | 225 lb | 220 lb |
| Mini | 245 lb | 245 lb |
| KA100 Junior | 320 lb | 320 lb |
| KA100 Senior | 360 lb | 355 lb |
| KA100 Master | 380 lb | 390 lb |
Every series sets its own numbers, so check the rulebook for yours. You’re weighed on the scale after the session. If you’re under, you bolt lead to the kart until you make it.
What it looks like in our pits
I’m one of the drivers carrying lead. My class minimum is 380 lb. I’m 170 before gear and about 180 in it, my kart weighs about 177 with roughly 7 liters of fuel in it, and I bolt on 25 lb of lead to get to 382. The extra two pounds cover a scale that reads differently from ours, or a hot session where I sweat a pound out. A liter of race gas weighs about 1.6 lb, so the 7 liters in the tank count for about 11 lb on the scale.
Our Mini driver is at the other end. He’s 94 lb, about 100 in his gear, and he makes the Mini minimum without a single plate of lead. As he grows, every pound goes straight onto the scale, and that’s when the numbers in this article start to matter.
What it means
If you’re at the minimum, you’re carrying the same weight as everyone else. If you’re over, it’s about a tenth a lap per 10 lb in a KA100 and about two tenths in Mini and Micro. Over a 15-lap race, 20 lb in a KA100 adds up to three or four seconds of total race time. It matters, but it usually isn’t the reason one driver is a second and a half faster than another. Seat time and consistency are almost always worth more.
For the Reddit question: 40 lb was probably costing about half a second. The rest of the 1.5 s gap was something else.
We’re a karting family, not engineers. These numbers come from our own logged laps and a physics model, so your track and kart will vary. If you’ve tested it yourself, tell us at kartingsocal@gmail.com.