Tuned In

Field Report: Too FAST For Street Tyres — the RP968.

November 22, 2023 High Performance Academy
Tuned In
Field Report: Too FAST For Street Tyres — the RP968.
Show Notes Transcript

With WTAC moving from DOT-rated semi-slicks to full slicks, the RP968 was assured a faster lap time in 2023, and it delivered.

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Race engineer Dejan Ninic of Complete Analysis, an ex-WRC consultant amongst other accolades, gives us the rundown on the change from Yokohama Advans to full slicks for the 2023 edition of the World Time Attack Challenge.

The RP968 team & driver Barton Mawer managed to get the time down from their previous best of 1:19.27 to 1:17.86 over the course of the weekend, giving them the overall win for the 4th time in a row.

We also saw a massive jump up the time sheets from Cole Powelson, going from a previous best of 1:30:02 to a 1:25.94 in the Lyfe Racing R35 GT-R. The old S13 Hammerhead, now under new ownership and rechristened as Tanuki, also set a blistering 1:20.45 time on debut, noting the car has also had some huge changes to be dialled in and had to be retired before the end of the event.

The Open and Clubsprint classes also saw some new class records this year from the Xtreme GTR and DC Jap Automotive teams noting not all classes have had the same options in tyre open up to them either.

Note 2023 tyre restrictions for Pro and Pro-Am Classes were in place in regards to the car weight dictating the allowable tyre width and height, so while teams can now run slicks, there are still limitations.

Speaker 1:

We're here at World Time Attack Challenge 2023 and one of the big changes for this year has been the move away from a dot control tyre to a full slick. We're here with Deanne, race Engineer for the RP968 Porsche, fresh off resetting their own lap record out lap outright lap record, that is, with a 117.86. Welcome to High Performance Academies' tuned in field report podcast series. In these special midweek episodes we look back through our archives to find the best conversations we've had through years worth of attending the best automotive events across the globe. We've pulled the audio from these tech filled interviews with some of the industry's most well known figures and presented it in podcast format for you to enjoy as a quick hit of insider knowledge. Deanne, this change from the dot tyre to the full slick from what I've seen following World Time Attack now for a number of years, it's always been a challenge with these top cars with a lot of downforce, nursing that dot tyre through the out lap, not putting too much energy into it and not overheating it. And, of course, over the years we have seen a number of tyre failures and delaminations Before we get into the slick. Can you talk to us about the limitations or the problems with that dot tyre?

Speaker 2:

Well, first of all, let me say the AO50 was a great tyre, but as the competition evolved and, like you said, there's more downforce but also more power, and I think the power is the most significant factor and the nature that we would have to use a soft compound, roll straight out and allow pressure, build all that pressure over one lap, and then what we've found was we're getting a temperature gradient, a high temperature on the tread surface and still cool sidewalls, and that created a structural problem internally in the shoulder, as I understand it. I don't know what you're going to have to say, but that's how I understand it.

Speaker 1:

So is there a temperature difference between the cold sidewall and the hot tread? That was the issue.

Speaker 2:

Yes, and that was creating either a fracture in the shoulder or we would see the elimination of the tread.

Speaker 1:

Now it's a great tyre, but when you start putting 1200 horsepower in this engine, and so it's not as far it can go, so I think there's a belief out there mainstream that the issue around this tyre was it wasn't able to support the vertical loads due to the high downforce that the cars are producing. You're saying that's not the case. Is that actually okay?

Speaker 2:

I feel that that's a problem that's achievable and I know that Tilton did testing in the past with tyre warmers. I know that they've tested at high pressures and I know that when we tested with high tyre pressures we managed the situation. What we couldn't manage was the need to go out and set a fast step after the first step, so that created another problem that was unique as well, but the vertical load of the tyre just had pressure and it still works.

Speaker 1:

The other issue sort of you alluded to there is really with that dot tyre. You had one shot at it. It was a case of nursing the tyre around, not putting too much energy into it on the out lap and getting it too hot, then coming onto the front straight with 10 tenths and you get through, as I understand it again, maybe three quarters of a lap and it would start to sort of get a little bit squirmy and start losing a little bit of that grip. So absolutely there was no chance of doing two back to back flying laps.

Speaker 2:

Well, we managed to do in time two back to back flying laps, but only because we found that afterwards we generated enough pressure in the tyre to get it there over the lungs. But when you're doing cool runs, like in the evening that we had last year, in the evening you were running the carcass temperature was 18 or 17 degrees and then when you do one run that's all you've got In terms of the tread itself, the rubber. We could go two laps, but as the power increased and as the load increased, that was diminishing. So two full laps were never possible, one and a half maybe.

Speaker 1:

Okay, so talk to us about the differences from a race engineering perspective, moving from the dot tyre to a slick. I mean, obviously, no matter how much money's been spent on the car, how much power it's got, really it's down to that tyre contact patch as to how fast you're going to go. A slick's designed obviously for this purpose, so does it give you a big advantage?

Speaker 2:

Yes, I think what it does is it pushes us into an envelope where we can push again. Now it's a safety factor that we've just achieved. So, in terms of what the slick does compared to the dot tyre, first of all we have a slightly wider tyre from a 205 to a 305, slightly bigger diameter. We went from, I think it was, 660 to 680, and that gives you more strength because you've got more side warm. From an engineering perspective, it's increased the rolling radius, so our acceleration isn't as great, but we always had trouble putting the power down anyway, so it just increased our gearing. And then, in terms of the handling side of it, the tyre is actually quite good. It's quite similar in its characteristics, in terms of its response, its stability and what it has allowed us. Because the sidewall is taller, we can actually run it with less camber on the rear, because it's a rear wheel drive and that means that we're not hitting up the inside edges as much, and so we needed the camber on the AO50 at the rear to give us stability. But this time, with this tyre, we can run less camber, and so we're getting a compound benefit as opposed to a compound loss.

Speaker 1:

Do you want to take your car knowledge game to the next level? Join us in the next free lesson at hpacademycom and start developing your own skills today. Now the ability here as well unlike the DOT tire is you can do lap after lap with this tire. I'm interested from an engineering perspective as well as a driver perspective. What is the process of managing the tire? Getting it up to temperature? I see you're using tire warmers now.

Speaker 2:

Yeah, absolutely. We did some testing with Yokohama and we tested without tire warmers and with tire warmers and I even got to the point in the test without tire warmers. I knew what I could do. I knew I could make the tire fail If we tried, and whereas when we use the tire warmers we would never have that problem. So introducing tire warmers allows us not just to make the tire warmer and ready for use, or uniform temperature, it also increases the pressure in the tire. So we're rolling out with 30 psi in the tire, not 22 like we used to.

Speaker 1:

So that out lap is safer on the tire.

Speaker 2:

Essentially, yes, absolutely, yeah, absolutely. So in terms of the driver, when they roll, that all he has to do is phase the tire and scrub them in so that he's got a better wear pattern on the front. So we take the release agent off of them and then he's ready to go. But this is a medium compound In this tire. We could also go to a soft compound, which would be similar, I guess, to the dot tire.

Speaker 1:

That gets you back into potentially that problem of sort of the tire going away after one lap maybe.

Speaker 2:

Yeah, possibly, and that's why Yokohama said look, trust us, you don't need it. This is the right compound and, as we can see, there's time in it, you know.

Speaker 1:

Let's be honest, it's working, isn't?

Speaker 2:

it Absolutely. And the construction of this tire. He's given the driver, the moment we put them on, more confidence.

Speaker 1:

Yeah, the other element I'll just come back to. You mentioned that this is 20 millimeters I think you said taller in rolling diameter. I'm guessing that this also affects the aero platform, because the underbody, in particular the sensitivity of that to the ride height, is quite critical. Is that just a similar case of dropping the car back to get the ride height back to essentially where it was, or is a bit more to it?

Speaker 2:

We try to do that. But because the suspension's designed with packers and bump rubbers, if you just try and drop it on the purchase, you're going to find that you're having to re-engineer or all that. What we did was we just went straight out as it was and then we found that that was okay and we've been tuning ever since and making small changes. But in any case, I would recommend someone just try and reinvent the wheel that. Just put the tires on and have it. Go and send.

Speaker 1:

I think okay is perhaps an understatement. This again is an outright lap record faster than an F1 driver and an open wheel wings and slicks A1G P-car. This is no joke. But there's still another couple of sessions ahead. Are we likely to see that benchmark drop even lower?

Speaker 2:

I think there's the opportunity to improve you Look thanks for your time, deanne.

Speaker 1:

You're playing your cards pretty close to your chest, but I respect that. Thanks again, and we wish you all the best to improve that time.

Speaker 2:

Thank you thanks for your great videos.

Speaker 1:

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