7 Reasons You're Slower on New Kart Tires (and How to Tell Which One)

Picture this, you're out there doing some pretty good lap times with used tires. And then you have this shiny new set of tires that you're ready to put on. And you're very excited because you're like, okay, now I'm going to find at least two, three tenths. And so I'm going to be the quickest on the track and I'm going to destroy my competitors that may already have been on new tires.

But then you're like putting the new tires on and all of a sudden you see your lap time at the end of the session, like what the hell? I'm two tenths slower than before with new tires. How is that possible?

I mean, I'm sure that it has happened to at least all of you, including myself, at least once in our lifetimes. And that may be very upsetting and surprising, I would say that's the right word when that happens.

And here in this guide, I'm going to unveil to you the seven reasons why that may have happened. Some of the reasons may be driver related. Some of the reasons may be tire related. And some of the reasons may be just conditions related.

1. The track got slower (80% of the time)

So the number one reason would probably be down to the track condition, because at the end of the day, the track condition is the most decisive factor because think about it, if the track suddenly gets super slow for whatever reason, maybe due to the weather, you know, it picks up a lot of humidity, or somebody just went off the track and brought so much dirt and mud on the racetrack, and so all of a sudden the conditions are worse. Or maybe simply, you know, there's been a few drivers driving with really bad tires like Maxxis, and you know, with very hard tires, I would say, that are going to make the track a bit slower.

And if all of a sudden these drivers show up, maybe it's a random practice day and it's just you and a bunch of other drivers, and you are driving with really high quality tires with a lot of grip that are very soft, and the other drivers are all of a sudden driving with very bad tire grips. Well, then you're going to be like, oh, what the hell has just happened? But then you just come to realize that they actually layered on the track, not real grip, but actually they layered like soap, as I would say.

So, you know, at the end of the day, the track is the most important thing you have to always monitor.

And if for some reasons again some drivers showed up with a bunch of really slow tires, then it's inevitable that the track is going to get slower, maybe three, four tenths. And even if you go on new tires, that's going to make you, let's say, two, three tenths quicker on paper, but the track compensates by becoming much slower. Well, then you don't have much of a chance, you'll just have to accept that, yeah, your lap times are going to go slower. So number one, if you get slower on new tires, you got to make sure that you consider track conditions, because I would say in 80 percent of the times, or when that happens, it's going to be the track.

If it's not the track, and you know that the other drivers are still going fast, whereas you actually went slower. So if the others are going fast and you're going slower, it can't be the track, because you guys were driving the same track, unless you were going on the dirty side of the track. But, I mean, that's your problem. So if you have worse performance and the others have the same performance, then you have to look into the tires.

2. You got a bad set

Many times you may pick a wrong set of tire. That may happen. Unfortunately, it's a bit of a lottery, especially in the wet, you know, when you select rain tires, it's a bit unfair. And one of the problems of our sport, that's, you know, you may do everything well, but then you just show up and you get an unlucky set of tire. And then there's not much, there's not much you can do. And you're going to be like surviving and being a passenger. And of course that's really upsetting, because there's not much you can do. Right.

But again, if it's the case, what you can do is try to get rid of those tires and try to get back on the other tires and see right away. And if all of a sudden you get faster with the older tires, it's 100% going to be the tire, maybe just the unlucky compound, or maybe it's just that the tires for some reason are very, very hard, because maybe they were stored in a place where it got a lot of heat cycles. Think about it, if they were stored in a warehouse where it had exposure to light, they would have a lot of heat cycles, from hot to cold, hot to cold, during your day, even just like a 20-30 degrees heat cycle during the day, it's, it's huge.

And it's going to create heat cycles, and the more heat cycles you have, actually the more hard the compound is going to become, and that's just ultimately not a good thing to have. So yeah, just, uh, just be mindful about that, it can be just down to the tires, especially if the tires look like blue or purple. I mean, if you see that, it's probably because they've been very old, and unfortunately you were unlucky and you just picked up that, uh, that set. But yeah, there's not much you can do, just have to replace the set, try another one, and see if all of a sudden your lap times get back to the normal.

3. The two tires aren't the same size

And the third reason of why you may be having worse performance on new tires versus with used tires, this is still coming down to the tires, and this has nothing to do with the compound, but it has to do with the shape of the tire. So if the shape of the tire has some defects for whatever reason, there's some blisters, but I mean, it's very unusual to have a blister on a new tire, otherwise you should definitely return it back to the, to the store that sold you.

But, you know, maybe something more nuanced, for example, if one tire has a circumference of like 83 centimeters, whereas the other has a circumference of 85 centimeters, you know, one of the two is going to be wrong. You know, and, and, and so not only it's going to be changing a lot the final drive ratio, you know, the, the higher the circumference, and you know, it's like the smallest sprocket, whereas the opposite is going to give you bigger sprockets, so like more exit and less stop.

But the point being is that it's going to also unbalance massively the chassis when you have two tires with a different circumference. And I personally hate it, because it's going to have a huge effect on the straights and even on the braking. So yeah, there's something I really hate to have, is two tires that are asymmetrically. So it's just something you don't want to have. And yeah, if that happens, there's not much you can do, either you pump up the tire that has the smaller circumference and you try to expand it so that it gets to the same circumference as the other, but still it's probably not going to be good anyways, because the tires just don't love to be expanded, and, you know, the tire thread is going to probably suffer from that. So that's one of the reason, it may be a little bit more evident than the compound, you can literally see and feel it when you drive.

And also that could be whether the tire is super unbalanced, but you should fix it yourself by putting some weights on the, on the rims, so you can balance it back. Of course, if the tire is super imbalanced, it's gonna be, not, not so bad for the performance, but just very bad for the drivability, and the driver is gonna struggle with that.

4. Somebody left the wrong pressure in

Then number four is actually whether you got something wrong from your side, whether in your driving or whether in your setup. So, for example, let's say you put the new tires on, but for some reason you, you just set up a wrong tire pressure, maybe it's too high, maybe it's too low, but like, it has to be really high or really low. Let's say your hot target is 0.90 normally, and in that case you go 1.2 bar, the hot target. Well, then in that case your tire pressures are way too high, and yeah, you're not gonna have the right grip level, except maybe on lap one or two.

Vice versa, if they're way too low, for example, if you have like a puncture or something, or not really a puncture, but like if you have so low tire pressure that it feels like there's a puncture, even though the tires may be new, of course you will not be able to extrapolate lap time and performance, because, I mean, at the end of the day, uh, if they're new but they have the wrong tire pressure, uh, it's still, it's still not going to be good for the tires.

So, if you set a completely wrong tire pressure because of a mistake, maybe you're in a hurry and you left the tire pressures maybe at two bars, well, even though they are new, you're not going to extrapolate any performance at all. So that has, has happened in the past to, um, you know, drivers, unfortunately even in, in my case, in the team. I want to say two mechanics, maybe they were in a hurry, and by mistake they forgot to, you know, lower the tire pressures after, you know, putting the, the new tires on the rims. And so, the, yeah, unfortunately the, the driver felt it, and so they had to come back in the pits, lower the pressures back, but then you kind of lose the peak of the tire. So yeah, that's of course something you have to look after, and it's something that you should be responsible to together with your mechanic.

5. Too much grip for your setup

Then number five will be actually having too much grip on the kart. So suppose you are gonna go new tires and there's no other problems, whether the track grip is, is fine, the tire pressures are fine, the compound is fine, the, you know, the circumference is fine, everything, but you still go slower. You know, maybe the tires that you were on were not that bad, you know, they had like one, two, three sessions, they were quite good, but then you go new tires and you actually go not that much slower, maybe be just one tenth slower, you do the same time. Well, in that case the only reason maybe is that the tire had the really good grip, but it gave you too much of a grip for the actual setup you had. So your setup was so grippy that by the time you put new tires on, it actually made too grippy, and you didn't really have performance anymore.

That happens quite a lot in 60 Mini, for example, because those karts, whenever they have too much grip, they are actually going to suffer, especially the engine is going to suffer if there's too much grip, and quote unquote the kart is stuck.

So it happens a lot that when you go on new tires you go slower, then it's because 100% you're too high on grip, and so you have to release some grips, whether that, whether it's someone from the, from the rims, by going magnesium, or whether it's going smaller hubs, whether it's going lower central gravity, you know, what is going more camber, lower tire pressures, wider rear track with less caster, etc. There's a bunch of things you could be doing. I mean, of course it really depends from the specific kart balance that you have in that specific moment, uh, we can't generalize too much, of course.

But if you have too much grip and you go new tires and it actually starts hopping, it starts to, uh, you know, pushing, and you get stuck in a way, you need to definitely release grip. You'll want to reduce the contact patch, you'll want to, you know, make the, the hubs smaller, again, there's a bunch of things you want to do, but ideally you want to also reduce the central gravity, and yeah, there's a bunch of things you should be, uh, you should be doing, that's going to, um, yeah, release the grip. And so next time you're gonna go out with the new tires, you're gonna find back the performance.

Normally, if you're feeling too good, remember this, there's a rule of thumb, but it's very important. If you feel too good with the used tires, and the grip is perfect, and you're like on rails, then when you're gonna go on new tires, you're gonna probably struggle a bit. So what's better is actually that you're sliding a little bit on, on used tires, and then when you go on new tires you're gonna be spot on.

So that's why, for example, you can't have exactly the same setup between used tires and new tires, because, yeah, you know, what's going to work on used tires is something which is a little bit more grippy, whereas when you go in new tires you may want something that's a bit more slippery. So yeah, it's really, it's really, really important, and you have to be mindful about this, don't forget it.

If you go slower on new tires, especially with single speed karts, you probably have to release some grip because you have too much.

6. You didn't adapt your driving

So the sixth reason is something related to you again, and it's related to your driving. Probably you didn't adapt your driving, because let's be honest, when you go on new tires you got to take advantage of the extra, you know, as, as I said, if you pick up extra grip but you're not using it, and let's say your kart is on the edge already have having too much grip, well, if you're not taking advantage of that grip, then you're not going to be able to go faster. You're probably going to go slower, because your kart is gonna get quote unquote stuck, and if you're not pushing more, the kart is going to start to hop and stuff, and stuff like that. So that goes hand in hand with point number seven, which is that...

7. You drove under the limit

You probably drove under the limit, and you didn't really use the extra grip that you had from the tires. So if you really drive under the limit, what's the point of using new tires?

You know, new tires are for those who are pushing the limits, for the ones that are going beyond the slip angle, that are using all the friction circle that the tires are giving you in that moment.

And so you can't expect to be, you know, going faster if you're driving conservatively, if you're driving under the limits. So, you know, new tires reward those that push, those that really trying to carry more speed by braking later, by carrying more minimum speed, by getting on the gas and carrying a lot of exit speed, and, yeah, just overall, just entry, mid, exit, and try to pick up a lap time.

Of course, what I notice is that on new tires you don't really get a lot of lap time on the braking, you get more lap time in the mid-corner, I notice, and on the exits if you need a lot of traction. But yeah, mid, exits, that's where you get most of the lap time, and, in mostly not in the slow speed corners but in the medium to fast corners, that's where you pick up the most amount of grip, um, normally, that's based on my experience.

Investigate it like a detective

So, yeah, here are seven points that I believe are great for, for you to have in mind for next time you go on new tires. If you still feel like you're going not fast enough on your tires, pay attention to these seven points, to this checklist, I'm sure that they're gonna help you massively in detecting the actual problem. Try to really, uh, go from one point to the other, and try to, yeah, just, like, make an investigation almost like a detective, and try to come up with a, with a reason why that happened.

And I'm very confident that if you ask PURPL, it's going to help you a lot to investigate and figuring this out. I feel that's going to be your coach, that's going to really help you analyzing your data and coming up with some really useful insights. So let me know how that goes. Sign up to PURPL, you have a free trial to get started, and also make sure you check out the six-month training program. I'm sure you're going to find lap time there. And, you know, I'll see you next time.