Continental Tire has issued a major bulletin to the IMSA GTD class teams in the wake of a series of significant issues and disputes during and after the 2017 Rolex 24 Hours at Daytona.

The race saw action aplenty on track, and the intervention of poor weather for prolonged periods added further layers of complexity to the overall picture.

Multiple paddock sources though have confirmed to DSC that there were as yet unreported issues at play that added even further unwelcome dramas on and off track to the racing efforts of a number of GTD teams including Audi, Lamborghini, Lexus and Porsche runners, with 10 cars of the 27 car entry now confirmed as having been affected to some degree.

Several of these issues revolved around some alleged issues for Continental Tire’s wet weather rubber, with multiple failures reported and reports too that either wet rubber supplies were running very low, and/ or that some tires were incorrectly mounted (tires clearly labelled as left rears were mounted as right rears for instance) with subsequent highly detrimental impacts on available pace!

After speaking to several of the teams involved DSC now understands that there remains significant dispute between the teams and tire supplier over the basis for both issues.

After being approached by DSC for comment Continental responded by copying us in on a memo dated yesterday (marked Confidential) addressed to the GTD teams.

After querying the ‘Confidential’ marking on the memo, DSC was given clearance late yesterday evening to publish its content though it is perhaps interesting that the memo was instantly published on a rival sportscar news website beneath a Continental Tire sponsorship banner — the published piece contained no input from any of the teams affected.

In very brief summary of the points raised and answered (the full memo is published below). Continental clearly accept that there were issues caused by a specific combination of conditions they had never experienced in testing, they offset that acceptance with points raised indicating a belief that some of the issues could have been avoided by the adoption of more conservative tyre strategy.

They also add that the construction of the left and right rear tyres is identical and that exchanging one for the other should not cause any issue, a point very specifically disputed but one team who saw major drop off of pace.

On the shortage of tyres, Continental explain that teams were buying up reserve stocks in anticipation of continued bad weather leading to shortages for others. They plan to address that issue by bringing more wet weather tyres to future races.

They confirm too that the lessons learned at Daytona will be incorporated into a current programme to develop a new wet weather GTD tyre for 2018.

DSC further understands that several GTD teams took their concerns to IMSA to attempt to raise safety concerns about the situations they found themselves in during the Daytona race.

After being approached yesterday by DSC for comment IMSA responded:

“IMSA is aware of concerns raised by some GTD teams that competed in the 2017 Rolex 24 race at Daytona. As such, IMSA is working with its partners at Continental Tire to review tire performance and appropriate steps for the future.

“Continental also distributed a post-race report memo to GTD teams on Thursday afternoon. IMSA and Continental have maintained this tire supplier partnership since 2011 and are proud of the continued development of technology through sports car racing.”

It would not be the first time that the extent of poor weather has caught out a tyre supplier for the event. Back in 2004 a lengthy red flag period resulted from a combination of very poor weather and the fact that, despite repeated denials, tyre supplier Goodyear simply did not have sufficient supplies of wet weather rubber on site.

This is Continental’s memo to the teams in full:

To all GTD teams-

Continental Motorsports would like to take this opportunity to provide a summary of the details surrounding the issues that teams encountered during the Rolex 24 At Daytona, along with our assessment of the key contributing factors and our plans moving forward. The goal of this communication is to be fully transparent with our partners, and work towards a mutually beneficial solution. The issues that surfaced at Daytona are completely unacceptable to us at Continental, and we are taking aggressive steps to make sure we have a robust solution for any possible conditions at Daytona in 2018.

Summary:

A total of 10 GTD cars (out of 27) experienced an unusually high rate of wet tire fatigue during the 24 Hour race, some of which had multiple issues through the night. These issues began when rizzling rain started around 7:45 pm through midnight, when the track conditions became wet/damp in some areas combined with dry sections, especially on the banking.

Continental Tire has always been tasked with providing a single wet tire compound and construction for each class which is suitable for all variety of cars, for all weather conditions, and at every track on the IMSA WeatherTech Championship schedule. As all are aware, a wet / dry track can be a worse case environment for a wet tire, therefore Continental Tire has always focused on developing a solution that is robust to this abuse. We pride ourselves on developing solutions that allow the teams a large operating window to work within, without having concerns related to the function of the tire, however, when multiple teams have issues it is a signal to us that we must thoroughly investigate the situation and if necessary look to increase the margin available in the tire.

The current GTD tire was run in 2016 in wet conditions, however we understand this was not comparable to the loads, run time, or conditions that were experienced in the 2017 Daytona 24hr race. We understand and acknowledge that this perfect storm of conditions and loads exceeded the amount of durability that our teams and partners deserve.

Analysis:

Of the failed tires that were analyzed, the root cause pointed to shoulder fatigue, where the construction of the sidewall and the tread meet. This fatigue is caused by localized deflection and impacts a very specific part of the shoulder between the sidewall and tread transition. In any tire, the load of the chassis is supported by the internal air pressure and the sidewall construction of the tire, therefore any reduction in internal air pressure (especially in conjunction with increased loads at Daytona) will reduce the protection to the sidewall, regardless of the level of robustness.

We also gave consideration to the following:

Changing conditions made it difficult to set cold pressure and achieve hot pressure targets.

While we recommended minimum hot pressures in our Roar Bulletin, it is not a straightforward process on how to achieve them. The pressure build is dependent on the track temperature and prevailing conditions, which changed drastically early in the race.

Cold track temperatures delayed the pressure build for many more laps than we have ever experienced in testing and past races. All of our wet tire testing in the past occurred at more mild temperatures, which gets the tire up to pressure faster. Although we have had good results in testing, the additional time at low pressures at Daytona was unaccounted for.

Cold grip levels. Continental understands that Competitors placed a premium on wet grip going into the evening. Typically, it is a common practice to lower tire pressures to generate heat in the tire and develop better mechanical grip, nonetheless with the current wet tire, finding the best pressures for grip in cold conditions may have brought the tire near the edge of not having enough pressure for shoulder durability at Daytona.

It appears that most incidents appear to have occurred up until the teams concerned adjusted their approach. In conversations with the teams that avoided tire issues during the entire race, we learned that they employed the critical strategies below and instructed the driver to do the following:

a) Protect the tires during low pressure windows.

b) Avoid the curbing and do not push the wet tire on dry surfaces.

c) Utilize the wet spots of the track to keep the wet tire from overheating internally.

Teams also implemented the following procedure:

d) Used starting pressures between 26-27 psi, (our bulletin recommendation, depending on conditions), which allowed double or triple stinting of tires.

Inventory:

The inventory levels of wet tires are based on past years’ experiences and possible expectations for a full wet race. During the 2017 Rolex 24, we found that in the early morning hours we were running low on right rear tires. In an effort to balance the remaining rear tire inventory, we pulled from the left rear tire inventory. A number of factors contributed to this course of action:

Many teams were replacing wet tires after every stint in an effort to protect against the fatigue risks described above. A wet set of tires is typically used for more than one stint, which would have reduced the consumption in this case.

Teams were buying up right side rear tires in anticipation that conditions would continue throughout the race, determining that an increased consumption rate would be necessary to avoid a fatigue risk. As a result, we distributed many more right rear tires than were being actually consumed. Many were returned at the end of the race.

Please note: Both rear tires are the exact same tire in every aspect except for the yellow graphic transfer on the sidewall.

Consequently, we will plan to bring more inventory of wet tires for all classes to future IMSA events and especially the Rolex 24 At Daytona. The evolution in recent years has brought increased car count, improvement in car durability and team execution, and less attrition than in the past. We will update our predictive models to cover these extreme scenarios.

Future Specification:

Introduced in 2017, our new DPi and LM P3 tire development has evolved the technology that we use in the IMSA WeatherTech Championship and IMSA Prototype Challenge.

Work has already begun on plans to incorporate similar technology into the new GTD wet tire for 2018 that will result in an increased load capacity and higher durability for Daytona and the 2018 season.

We will be fully transparent with our development, and work with IMSA to coordinate an acceptable implementation date in the 2017 season.

We are moving forward from the challenges that we all faced at Daytona with an increased focus on safety and protecting our paddock in extreme conditions. We are pulling ahead the testing and production plans to release a more capable and durable tire as soon as possible. We care deeply about the important role that we have in the IMSA WeatherTech series, and value the partnership that we have built over the years with our teams and manufacturers.