So I did a little searching for a topic like this, couldn’t quite find the answer —
Running YLC’s in a sealed animal class (taken 1st all 3 events I’ve ran this season, .5 to 1 sec per lap in front of the guy behind) and I’m really just having trouble gauging how long to run a set of tires. I see the wear dots, but how low do I let them get? Do I run them until the guy who runs behind me starts catching me/until my times fall off? Can I use a tread depth gauge? Ive run these since the first race of the season (3 race days, 5 heats of 10 laps on .75 mile track each) and a couple of practice days too. I’m still improving as a driver so it’s hard to concretely look at my times and say “I need new tires.” I’m a grad student and don’t have a large racing fund, so I’d like to use them for their proper life, but I’m also competitive and don’t want to give up positions I don’t have to.
depends what you have on the line? I don’t think the fall-off will be so cliff-like that you’ll go from that lap delta to falling behind without a bit of a progressive drop off.
I’m cheap, and like to use every bit of life in my tires; but, i’m rarely at the pointy end of the field, so take my advice with a grain of salt.
My brother and I are in the same situation and trying to figure out the same thing. Our experience with YLC’s thus far has been that after the first session or two they have very little fall off until they are dead, and then you’ll know because they are a handfull to drive.
We’re been fortunate enough to be at the pointy end of our fields too and had theorized that we could get 3 race days competitively out of them before worrying about changing…but I took a set that I thought weren’t going to be competitive any longer and finished 2nd with them at New Castle last weekend proving that we can likely expand our comfort zone to at least 4 race days before turning them into practice tires
We’ve been tracking heat cycles and that set I used last weekend was on heat cycle 18 at the end of the race and were still good. I think anywhere near 20 heat cycles and you better have new ones sitting there at the ready if your intent is to stay near the front.
Thank you, that’s actually very helpful! Let me know if any of this changes, I’ll pay attention the next two races and see what happens, I’ve got to be awfully close to 20 cycles
I have a theory that the difference between old and new YLCs is minimized when it’s very hot in the summer and there’s less “warmup” period for the tires as well. I think there’s more magic in the new tires when grip levels are power and temps cooler. I don’t have any data to back that up though just an observation.
If you have a 2nd set of wheels/tires we’ve also been using our practice wheels/tires during warm-ups on race day then mounting the race tires only for the races to keep their heat cycles minimized and extend their life as far as race days.
Wear varies from tire to tire, but one tip I have found with several brands of racing slick tires (we also run a pretty hard tire here that isn’t traditional) is this:
When the inside edge (sometimes called the ‘feather’) begins to have a concave feature leading to it, those tires are pretty much done. To clarify, if you look from the front or rear of the kart at the profile of the tire, which is usually a gradual convex profile, the inner edge (closest to center of chassis) can develop a concave “divot” area on the tire near the area of the feather, where rubber builds up the most. The more the tires wear, especially towards the end of their life, the worse this gets.
Tires are a fascinating topic that I don’t understand nearly as much as I want to. But, what is apparent that at operating temperature rubber on the surface becomes semi-fluid, and “sluffs” or migrates off the tire. Naturally, in hard corners this behavior generally will be most dramatic on the inside edge of the tire as most racers run some negative camber. So, after a while, which area will run out of rubber first…the inside edge. It’s also the area that is worked the hardest on most karts, so if it begins to degrade, there go your tires.
Bridgestones regardless of compound tend to be a fairly oil tire (compared to an Evinco or a LeCont). Each tire is a great tire, but this can make judging wear on Bridgestones more tricky.
Ultimately, I’d strongly suggest chatting with other local racers, as depending on their competitive ambition, budget, and track conditions tire life can change dramatically. Ball park for a set of tires to last adequately for most racers to get reasonable performance is between 1.5-3 track days depending on the track surface, but sometimes you can get more than this if the track is easy on tires.
Eric brings up a good point. Depending on the surface # of heat cycles may not translate from track to track as some tracks are more abrasive than others.
None the less I’ll add more data points and maybe more discussion points here as well.
This weekend I did practice and warmups on a set of YLCs that had 18 heat cycles on them at the end of the last warmup and they felt fine. I switched to my “race tires” which only had 9 cycles on them going into the day and they felt worse than the warmup tires. That said I brought home P2 and was only .1 off of quick lap of the race. Air Temps also went from low 70’s in warmups to just over 90 at race time so the track was changing.
3 variables come into play for consideration on why the race tires possibly felt worse than the practice tires.
1- Age of the tire. I’m starting to wonder if age of the tire, once you start using it, plays a factor as well as number of heat cycles. I’ve been trying to put as few heat cycles as possible on those race tires which means i originally ran them at the very beginning of May and have been using them sparingly over a 10 week period since I started. The practice tires with more cycles on them have only been used for the last 6 weeks and just been used more frequently. When swapping them between wheels the set with more cycles subjectively felt easier to work with and manipulate onto the wheels.
2 - Wheels. This somewhat goes back to another thread but my practice tires were on OTK MXJ cast magnesium wheels and my race wheels were on OTK MXL forged magnesium wheels. It was 90 degrees yesterday and should have been the perfect weather for the MXL wheels to shine, but I’ve had more than a couple people tell me that the MXL is just too stiff of a wheel for the hard compound YLC tire. They claim the YLCs like a wheel that produces a little more grip.
3 - Heat - It just got hot and the first two heats the kart was a touch free to put power down but in the final it actually wasn’t bad, just still not quite what I wanted. Everything was hot and greasy at that point though.
So I’m left to ponder these things but though I’d share them in my journey with understanding these tires better. Oh…and to really blow your mind I went the same pace in the race as I did in the final warmup so feel aside they were still pretty much the same on the clock. I just wonder if when I was pushing hard in the race if I couldn’t have put down a better lap on the other set of wheels / rubber.
Here in Brazil we use MG Red tires and we try to do not go beyond 100km with the same set of tires if we are trying to setup a kart or trying to get good lap times. But when we are just driving for fun we can go up to 200km or so.
MG Yellow tires are softer and so presents a shorter lifespan.
But the numbers I gave above are an average once different surface conditions, different tire pressure, different driving style and etc. changes the wear index of the tires.