SportBiKeZ

The penultimate pre-season test came to a conclusion at the Circuito de Jerez in southern Spain on Monday afternoon after three days of intermittent track activity courtesy of unusually turbulent Spanish weather. Rain and wind prevented teams, riders and tyre manufacturers from conducting uninterrupted running over the entire three days, including a damp official practice on Sunday in which Ducati’s Casey Stoner was fastest. A dry final day offered some meaningful running with more useful information collated by Bridgestone’s engineers.

A flurry of late qualifying runs shuffled the timesheets on the final afternoon of practice with Valentino Rossi ending the session as the fastest rider on Bridgestone tyres with a time of 1m39.568s. Several other Bridgestone riders were present in the top ten over the course of the test with some solid performances on race tyres. However, the final timesheets show that Bridgestone’s qualifying performance still needs to be further improved ahead of the season start in Qatar in three weeks’ time.

Q+A with Tohru Ubukata - Bridgestone Motorsport – Manager Motorcycle Race Tyre Development

What has Bridgestone managed to achieve over these three days with the mixed weather conditions?

“It was a difficult test for everybody with tricky track conditions over all three days. After the dry first day, we were able to carry out some wet weather tyre testing on Sunday, which was the first occasion for some of our riders to sample our wet specifications. In spite of those conditions, Casey did an exceptional job to set the quickest time and to win the car. On Monday, we had a brief shower at the start of the morning, but from then on it stayed dry, although with some quite gusty wind which was not helpful. We worked on evaluating tyres with a lower temperature compound range compared to the last tests in Sepang and Phillip Island to prepare for the Qatar night race and the Spanish GP in Jerez. We also continued to look closely at our qualifying tyres with many riders conducting detailed evaluation of different specifications.”

Has Bridgestone obtained all it needs from this test?

“Of course, we would have preferred a dry day on Sunday, but our riders worked really hard to get many laps in over the three days and we are grateful for their efforts. Today in particular we have seen some progress that we are sure will prepare us better for the race in March.”

In what specific areas does Bridgestone still need to improve qualifying tyres?

“We are quite happy with the durability of the qualifying tyres at this circuit, but it is clear that we are still in need of more grip to allow our riders to make an important step up in terms of lap time. Although our rivals continue to be very strong in this area, I believe we have made improvements since last year and even since the first test of this year. We tried several different specifications on Monday with different riders so we are sure that the variety of detailed feedback will benefit our development in this area.”

What is the plan for the next test in Qatar?

“Qatar test is going to be valuable, not only because it allows us to prepare our tyres for the opening race of the year at the same circuit, but also we will be following a night schedule for the first time. We will understand more clearly exactly what track temperatures we are likely to face and how that will affect our tyre performance by racing so late into the night. This will aid the tyre selection process on the Thursday of race weekend when our teams and riders must finalise the 22 rears and 18 fronts that they will have at their disposal according to the tyre restrictions.”

Published by Tasha Crook

Tires are the intermediary between a fastest lap and a trip to the gravel pit. And with Japan, Italy, England, Germany and now even the U.S. producing 1000cc-plus motorcycles that crank out upwards of 130 horses to the rear wheel, the time has come for a new generation street tire that can handle those mega-power outputs and the associated loads that accompany putting that much power to the pavement.

Tire development is all about compromise. Make a tire too sticky and we’ll burn them up in a few hundred miles. Make a tire too hard and we’ll get the mileage we desire but sacrifice grip and warm-time. Integrate numerous tread cuts and it displaces water but compromises our coveted contact patch. We could continue or dissertation on compromise, but Pirelli believes that it’s found the right middle ground with a tire that can meet the needs of both 21st century man and machine.

The Pirelli squad mounted up a set of Diablo Rosso tires (120/70-ZR17 front and 180/55-ZR17 rear) on our 2007 Honda CBR600RR. With the tire pressure set (36 psi front, 42 psi rear), we hit the streets of Ventura County. Once under way, it became immediately clear that the tires do not offer the greatest feel. Throughout the street ride we felt disconnected from the road below. However, steering was extremely neutral and side-to-side direction changes were no better or worse than the OEM Bridgestones that were previously fitted. The lack of feel from the rubber made it difficult for us to really push hard through the curvy, mountain route that Pirelli had laid out for us. The few times we were able to man up and actually work the tires, they performed flawlessly without a hint of instability or lack of traction. In fact, adhesion levels felt very consistent. During our photo shoot, a few times we locked up the rear wheel to speed up the turn-around process, sliding the bike around 180-degrees. The rear rubber consistently slid, making us look like we actually knew what we were doing. Normally our CBR600RR delivers a relatively plush ride on the street for a 600cc sportbike. But with the Rosso underneath us, that smooth ride was compromised. The CBR’s tires normally work in unison with the suspension to help soak up some of the irregularities and bumps in the pavement, but the Rosso tires have a stiffness to them that translated every bump and pavement ripple directly through the bike.

Tags: tires, performance, wheel, motorcycle, pirelli