Happy New Year everyone!
I recently did a rental kart race. I was the lightest driver there (70kg, while the others were around 100-110kg), so I had to use around 35kg of weights. The kart felt nearly undriveable in some corners and I was really fighting the wheel to get it turned, especially in the hairpins, and I was nearly 1 second off the fastest driver, who is the same weight as me (and had the same weights on his kart) and we have similar laptimes without the weights. I have driven weighted karts before (mostly racing karts, but also rentals at the same track, but at most with 10kg of weights), so while I expected to be slower I was still surprised by how hard it was to drive.
The next race is in a week, and I don’t want to be that much off the pace again. Does anyone have any tips on how I could drive such a heavy kart faster?
At my local rental track, the variation from one kart to another can easily be 1 second
Yup you might just be looking at fleet variability. Video would help to compare before and after. I wouldn’t say that a kart that’s weighted feels hugely different. It does but not super dramatic. 77lbs is a lot, though, and would be noticeable. General rule of thumb is 1/10 per 10-20 lbs.
Move you pedals all the way up and the seat all the way up. Even our largest drivers will drive like this as its the best way to get the rental SODI karts to turn. Also, Rentals are never even and I have run one and jumped into another on multiple occasions and had a one second difference in lap time. Just a heads up.
Unfortunately I don’t have a video to compare, but if it helps, the kart felt unnaturally understeering in the left handed fast hairpin on the track, which normally requires a small lift and a small turn of the wheel to get the kart turned. I had to brake and turn the wheel all the way in order to make the corner, and I noticed that I was losing most of the time to the drivers ahead in that corner. I had some small losses of time through other corners too, but not as much as in that specific corner.
Interestingly enough, I noticed that the corners that were harder to drive were the left handed corners. I think that has something to do with the weight compartment on the Sodi karts being on the left hand side of the kart.
It could be that the 70lbs or so does affect it. Generally, though, it seems like rentals that fight you in one direction have some bent bits. I dont think Ive ever had to carry 35kilos of ballast in rentals so I’m uncertain if the push you are experiencing is due to the weight tray on one side. Assuming you get different kart next race, I’d be curious to see if same result.
More likely, the chassis is not quite as straight as it used to be
I think reserve judgment until the next race. It could be the weight box, although it equally sounds like a bent chassis or alignment that’s off.
You can minimize some deficiencies by moving the seat around as someone said above.
At times I’ve also had to thump the side of the seat with my body at turn in to help the kart rotate. Try different things and see what works. Powerover on entry with exaggerated steering input, quick lock up or some trail on the brakes etc. leaning your body out in general can help free the kart a bit.
It takes some time in different karts to quickly asses what “treatment” it might need. But usually a turn from lock to lock while stationary will give you some clues.
So, I just finished the 2nd race. This time I got a different kart, which happened to be the kart of the winner of the last race. The difference was actually huge, my best qualifying lap was more than 1 second faster than the previous race (for comparison, in the last race I qualified P6 out of 15 drivers and 1.3 seconds off pole, but in this race I qualified on the front row and less than a tenth off pole). The kart was much more comfortable to drive, and there was a huge difference in the left handed corners, so I was able to consistently put in fast laptimes with no mistakes and had similar pace to the leader throughout the entire race (not enough to overtake sadly).
Interestingly enough, while the fleet mostly remained the same as before, the kart I had in the previous race was replaced by another. It’s probably a coincidence because other karts were replaced too, but I can’t help but overthink it
The one downside with the convenience of arrive and drive rental racing is the disparity between the karts in fleet. It’s hard to swallow when you get a crap kart but it’s part of the game, I guess.
I have found that some series/locations are better than others when it comes to the karts condition and maintenance. Try the various options available to you to figure out whose karts are good and whose are poorly maintained.
Yeah that’s just how it is. It’s just even worse when it happens in the first race of the new season, but then again it would definitely be better than on the last race, so there’s that. The guys at the track test the karts before selecting which ones will be used in the race but that doesn’t guarantee perfect results every time.
In most rental series I have been in you switch karts for heats to make it “fairer”.
Of course everyone has the mega unlucky back-to-back bad karts race.
On a completely unrelated note…
We gonna have to start differentiating between electric and gas rentals when it comes to how much time weight costs.
Gas karts we throw around basically 1/10th of a sec per 20lbs. This is approximately true with gx270.
But electric bottom end is so strong that that guys who are 250+ are not getting creamed. The e-kart power seems to mostly compensate for their weight on the bottom end.
There, I fixed that for you
Trying to guess how much time a pound costs is one of the dumbest hills to try to climb, in my so humble opinion. We all know where the weight is can be more important than how much it changes the power/weight ratio. What if electric karts are less sensitive to mass, not because of mass itself, but because they inherently have a lower and heavier CG from the battery pack, so a bunch of weight way up high is necessary to free the kart up? A 150lb 5’10"er like me will struggle with a bound up electric kart worse than a gas kart. With gas karts, I have to really lean hard out of turns, but electric karts are much worse and just flat slide for me.
Then there’s drag. 100% of the electric rentals I’ve driven were indoors, and 100% of the gas ones were outdoors. In the US, this seems to be a pretty strong trend. Along with that trend, speeds tend to be slower indoors, so drag penalty goes wayyyy down (cubic when looking at drag power and speed). So the big guy is punching a larger hole in the air than a small guy, and this has a noticeable effect at higher speeds and lower power. Take even 5mph off everyone’s speed, and the penalty for broad shoulders goes way down (the drag power at 50mph is 70% of the drag power at 55mph).
In short, a tall 200lb guy may be significantly at an advantage over a short 200lb guy, yet the “1/10th per 20lbs” baloney would say they can run the same time. The tall guy has both a higher CG and narrower frontal area, so, for the same skill, would have a better time, especially if the kart has a heavy, low CG.
Sorry you are correct on the weight. 1/10 per 20.
True. But… the series I’m in I was surprised by how well the heavier guys were doing relative to gas rentals.
I think that body position does matter and does affect things. I am 165. I always slam the seat as far forwards as possible (and never use insert).
My pal @nikspeeds weighs 200+. He tried slamming seat forwards and as a heavier guy, found that it doesn’t work for him at all.
I think it’s the actual powerplant. The bottom end torque overwhelms the mass way better than gas and accelerates a 250lb guy as well as 150lb guy (for all intents and purposes).
It’s not subtle either, there are guys 250+ winning their heats in their divisions against skinny guys.
There is no draft. We do not hit high enough speeds and the kart simply tops out. It appears to push the heavier guys pretty much about the same.
Even from K1 themselves, gas karts actually make more power most of the time:
If you gear both the gas and electric karts to have the same top speed, say 50mph, the gas kart will be more powerful past 25mph. If the electric kart is heavier, it loses even more power advantage. Yes, I know these curves aren’t labeled for karts, but it makes sense to assume K1 chose representative curves
Yeah my experience at Supercharged is that the pull is very strong off the bottom and it then hits top end in a purely linear fashion and then rides limiter. There is no rising “revs” as you go down straight. Which is why electric is so good on the swooping indoor stuff without straights. Theres very little powerband.
I think we will keep seeing uppy downy indoor twisty stuff because it’s so well suited to the power these provide. To get EOS speed fun, you still need to go to UK, NJMP, etc. There’s no top end excitement on electric. (But on an appropriate layout, it’s great).
How are the powerplants being chosen for comparison? Peak output numbers or?
I think they are very much just qualitative. There is a strong trend in EMs to have torque fall off in a 1/rpm fashion before halfway to redline though, so that is the valid part of my point. Most of the time spent during a lap will be higher than half of your top speed. For my own kart, I am never below half of my top speed, so that’s even being a little generous. This makes EVs very forgiving if you really botch a turn and drop way below pace, that’s for sure. But comparing fast lap to fast lap, they lose that advantage.
I suppose that sort of depends. In the ones I’m driving, your rear grip is breakable under acceleration and the axle “hops” as it seeks purchase. It won’t spin from standstill but it will spin rears if you give too much power midcorner (hop hop hop).
However, it doesn’t seem like the runs you get are anything like the runs you get in gas karts. You both top out super quick.