Rookie Darryn Binder 'witnessed at first-hand' a cold-tyre MotoGP highside during the final day of the Jerez test.

The first rider to move straight from Moto3 to MotoGP since Jack Miller in 2015, Binder completed his opening day on the 2021-spec RNF Yamaha with a best lap time of 1min 39.942s.

That put the South African one-second from next closest rookie, VR46 Ducati's Marco Bezzecchi.

Binder, brother of KTM MotoGP race winner Brad, then began the final day getting faster and faster, until a combination of factors resulted in a 'big highside'.

"I felt like I picked up straight where I left off yesterday, which was nice. So I could get straight back into it and start chipping away," Binder said.

"At the beginning of today we were just putting tyres and fuel and going, I was getting faster and faster, then just as we started to dive into a little bit the ride height device and stuff a little bit, unfortunately coming up to lunchtime I had quite a big crash."

Binder explained: "I'd done two exits already with the medium tyres and I really felt that it took a good lap to bring the rear tyre up to temperature. Many people had told me about this, 'you've got to be careful to make sure you bring the tyres up to temperature before you push'.

"When I pulled out of the pits, I saw there was a rider coming on track, so I did the first five corners as normal and then rode slow down the back straight to let the fast rider past. So that I didn't disturb him.

"I continued my lap, but because I had slowed down and I was going probably too slow, I think the tyre went down quite a lot. Then, I didn't really push or anything, I went in fairly slowly and unfortunately the rear just let go on me on entry and I had a big highside.

"It was a combination of things. When I went out it was also one of the windiest times, when the dust was coming across the track, so I think a couple of things played into that.

"But at least now I've witnessed at first hand and know that when I go out, I need to push, but not too much and definitely not too little. Because the tyre temperature, that's a really tricky thing.

"That [accident] really slowed down the progress unfortunately, I spent about a good hour or so laying on the floor of the truck just stretching out. Then in the afternoon we managed to get back out and we kind of started again, just building up into it, because I didn’t really feel my best.

"But at the end we tried a couple of small things with the electronics and I was using the ride-height device and stuff like that. I was still just improving and improving. Also we've tried the medium and soft tyres. Just figuring things out. Taking it lap-by-lap. Really just enjoying it."

Despite the highside setback, Binder went on to set his best time of the test on lap 53 of 55, a 1m 39.941. That was 3.069s from fastest man Francesco Bagnaia and 0.6s from next closest rookie Bezzecchi.

"I really feel like we could have made a bigger step today without the crash because we lost a lot of valuable track time with the good temperatures," Binder said. But unfortunately that's one of the things. You live and learn and try not to make the same mistake again."

Bottom of the timesheets on both days, Binder has been told not to worry about lap times until the official Sepang test.

"The team has been really helpful. Everybody is super calm, they are here to take this first test as a shakedown, just go out, ride the bike and we’ll start working next year. We've got the Rookie Shakedown test in Malaysia and then when the real [Official] test starts in Malaysia we can start to work," explained Binder, whose only Moto3 victory came in the 2020 season.

"Until then, it's just build-up slowly, learn what I need to do to ride this bike. Learn as much as I can about everything and then slowly start to put it together. I think there's no rush.

"Like today at, if was doing a '39 or a '38 it's still 2-3 seconds off. It doesn't make a difference. Right now, I just need to learn as much as possible and try and understand as best as I can. Get to know everyone and the bike. Just take it as it comes."

Experienced RNF Yamaha team-mate Andrea Dovizioso was 13th fastest on the 2022- Yamaha prototype.