According to Andrea Dovizioso, current MotoGP championship challenger, the braking systems available to premier-class contingent are continuously evolving.

Improvements with electronics, tyres and outright power means the job of Brembo, the brake supplier for each of the premier class' six factories, never stops, as its product copes with the demands of ever-quickening machinery, and a variety of riding styles. sat down with Brembo engineer Lorenzo Bortolozzo to discuss how the Italian company copes with these ever-changing demands, and some of the recent challenges they have faced, with particular attention paid to the change from Bridgestone to Michelin as tyre supplier at the end of 2015.

Bortolozzo also offers up a fascinating insight on how means of using the rear brake has changed in recent years, the talents of Casey Stoner, and recent developments that have allowed riders to use front carbon brake discs in wet weather conditions.

This is a follow up to an earlier interview with Dovizioso, in which the Italian spoke about Brembo's role in MotoGP. Click here to read the interview with the Italian.
Andrea Dovizioso said that with the continued development of electronics, MotoGP machines are able to brake later and later. I guess that means Brembo's braking systems always need to evolve.

Lorenzo Bortolozzo
As Andrea said before, not only because of electronics, but also for the performance of the tyres. With Bridgestone tyres in the past, we introduced different specifications of discs, pads and callipers. We increased the diameter of the discs, increased the contact surface of the pad and designed a special calliper in order to cool it as much as possible. The temperature of the calliper is also important. I think with Bridgestone tyres, with the 320mm disc we were very close to the limit. With the 340mm disc, the Bridgestone tyres, the increased pad, and a bigger calliper, which we call a heavy-duty calliper, we solved the problem. Now with Michelin tyres, the braking style of the riders changed a lot. We saw that the temperature of the carbon material is 100 degrees less than with the Bridgestone tyres. This is because the rider cannot brake really, really hard. It's a completely different braking style.
How did you adjust?

Lorenzo Bortolozzo
For us, the change of tyres was very important. With Bridgestone tyres all the riders asked Brembo to increase the initial bite. The stiffness of the Bridgestone tyre was very high and it was very important for the riders to brake very hard in order to modify the shape of the tyre to achieve the best grip. With Michelin, the stiffness is much different. Now the riders' ask to reduce the initial bite. For this reason, we designed a different master cylinder, which is a different calliper in order to try and reduce the initial bite, and give the rider the maximum control inside the corner.
So in theory if the riders had the same braking system from 2015, fitted a Michelin front tyre, and braked with the same intensity, it would lock the front wheel?

Lorenzo Bortolozzo
Sure, and you would also lose the front if you tried to brake inside the corner. It's necessary to be very careful.
Has the change from Bridgestone to Michelin brought about a change in Brembo's rear brake, or the technology you use for it?

Lorenzo Bortolozzo
Not for the rear brake, because the performance of the Michelin rear tyre is good. But now a lot of riders use the thumb master cylinder to brake with the thumb and not with the pedal in the right corners. Now the rider use a lot the rear brake during the acceleration time. Not only during the braking time. Maybe the first one without the thumb was Casey Stoner, who used the rear brake a lot during the acceleration. I think that now all the riders must use the rear brake during acceleration. We develop a special thumb brake in order to give the riders the possibility of using the thumb brake during the right corners. Now the riders use the rear brake a lot. We have different specifications of rear master cylinders, rear callipers and thumb master cylinders, because we try to satisfy the requests of all 23 riders. Our dream is to standardise the braking system, but it's impossible!
So Casey was the first guy you saw using this method. I'm guessing his talent was clear from the data you could see.

Lorenzo Bortolozzo
Yeah, but I think Casey was unbelievable - completely different to all the other riders. Now he is the test rider of Ducati. For example, I know that one year ago at Sepang one of the Ducati guys asked the technicians to check the telemetry data of Stoner and the technician said, 'No, for you, it's impossible.'
Impossible in what way?

Lorenzo Bortolozzo
Impossible because Casey is special. The use of the throttle and the use of the brake is not normal. The use of the bike... Casey was the only one that won with the Ducati bike. He was first and the second was at the end. Maybe this was the problem of Ducati. He's special.
You mentioned Casey's use of the rear brake. Was the way he used the front brake special or different as well?

Lorenzo Bortolozzo
No, no, no. The front brake, not. The rear brake, yes. Casey used the rear brake a lot but very gently. For example, in the past Nicky Hayden at Ducati used the rear brake a lot. For this reason, we made a very special rear disc - a huge one - but Nicky used the rear brake especially during the braking time [before the corner entry]. For this reason the temperature was very, very high. We made a special calliper and disc to guarantee the safety of the rear brake system. Casey used the rear brake during the acceleration time very smoothly. For this reason, the rear brake system of Casey was standard.
Last year, it was rumoured that Cal Crutchlow was using the rear brake for 70 percent of the lap at Assen to try and limit the wheelie.

Lorenzo Bortolozzo
Yeah [but] maybe with different pressure. If we compare the braking time to the acceleration time, the pressure is different. But it's correct. For me it's unbelievable! But I'm a street rider, not a MotoGP rider. And I'm old! I think the MotoGP riders are completely crazy but very clever. If there is some change the MotoGP rider needs just one test to adapt to the riding style or the braking style to the change. They are very clever.
Is using the back brake this much now a common thing?

Lorenzo Bortolozzo
I think now this is mandatory. If you want to do a good job, you have to use the rear brake a lot. I repeat, not just during the braking time, but also during the acceleration time.
Is this because of the switch to the standard electronics ECU? Are the anti-wheelie systems now less effective than what the top factories were using in 2015 and before?

Lorenzo Bortolozzo
No, because also in the past many riders use the rear brake. I think now, with the power of the bike, it's very high. In order to keep the line at the exit of the turn, it's mandatory to use the rear brake.
Would the Honda guys use it more than others?

Lorenzo Bortolozzo
No, now I think that all the riders use the rear brake at the same level.
So just how different is the braking system different on each bike? How, for example, does Yamaha's differ to Ducati's?

Lorenzo Bortolozzo
Ducati and Yamaha use every time the 340 discs but they use different callipers and different master cylinders. The biggest difference is with the HRC bikes. HRC use every time the 320 discs. I don't know why to be honest. HRC ask me, 'Why do Yamaha, Ducati, Suzuki use the 340 discs?' And Yamaha, Ducati and Suzuki ask me, 'Why does HRC use the 320 discs?' I think that it's not so easy to explain the difference. Maybe it's the engine brake. I don't know. But HRC is the special one. Aprilia, KTM, Suzuki, Yamaha and Ducati all the time use the 340 discs.

In the same tracks with the same conditions Ducati, Yamaha, Suzuki etc achieve the same temperatures with the 340 discs as HRC do with 320 discs. HRC riders, and also Cal, brake very aggressive. It's not the braking style [that is the reason they use these discs] but more the style of the bike.
As you supply all of the manufacturers, how do you choose what is the best development direction? I assume feedback is not always universal.

Lorenzo Bortolozzo
We receive all the feedback of the riders. Sometimes they also complain. We try to understand the way to solve the problem, or the way to improve the performance of our calliper. For example, it's very us for us to see the wear of the carbon material. We introduced some instruments in the calliper in order to improve the wear of the discs. Improving the wear of the disc and pad, we improved the stability of the lever, and the performance of the braking system.
Do any ex-racers work at Brembo?

Lorenzo Bortolozzo
We develop just from rider feedback. We don't have an internal test team. Honestly speaking, the comments from the different official riders are different from the test riders. The lap time is different. The official riders are every time over the limit. The test riders are close to the limit. For us, it's very important to understand the performance of our braking system when we are over the limit!
Dovizioso also mentioned that a lot of riders don't fully understand the potential of the bike until the first round of the season, as that is the first occasion when everyone is pushing the limits on every lap. Is this the case for Brembo, when you have something new to test?

Lorenzo Bortolozzo
Correct. Maybe not only in one run of just three or four laps, but after twenty laps because we have to guarantee the consistency of the braking system for all the race; not only for one run during free practice. Obviously free practice and qualifying are important but the most important thing is the race.
How is it possible for riders to now run carbon discs in wet conditions, as we have seen in several wet sessions (and even the Sepang race last year)?

Lorenzo Bortolozzo
It's a strange thing because the last time we used the carbon material in wet conditions was maybe twenty years ago. The carbon material was different to the actual [current] one. The result of the test was not so good. To be honest I don't know the reason. When I joined Brembo I tried to understand because I'm an engineer. If there is some problem I want to understand it.

We continued to develop the carbon material. Now we have four shapes of disc in two different sizes. We have the 320 disc in standard mass and high mass. We have the 340 disc in standard mass and high mass. We have different shapes of pads. Also the teams make a special cover, to cover the disc against the water.

Two years ago I suggested to the team that during some tests, if there is some rain, please try the carbon material because Brembo thinks it's possible in wet conditions. We performed many tests at Brembo. In our opinion the safety was guaranteed but in our dyno it's not so easy to understand the performance. To be honest, from last year, when Marc used the carbon discs during the Sepang race many riders understood it is possible to do this.

Today during FP1 many riders used it with a cover, and a different shape of the disc, according to the different behaviour of the bike. Also in dry conditions, riders use a different size of calliper, pad and disc. Now we know that the most important thing about using carbon discs in the wet is to guarantee the minimum temperature.

If the temperature is more than 250 degrees, the performance is good. But this is the same in the dry. Between 20 degrees and 800 degrees the friction coefficient of the carbon material is very stable. Under 200 degrees the friction is stable but it is different from one corner to another. We lose the stability of the level. For the riders this stable level is very important.

By Neil Morrison

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