INSIGHT: What was going on with the brakes at Indy?

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INSIGHT: What was going on with the brakes at Indy?

Insights & Analysis

INSIGHT: What was going on with the brakes at Indy?


The biggest question during and after the Indy 500 involved the spate of locked brakes, crashes, and speeding violations on pit lane.

“None of the problems you saw were the drivers’ fault,” one team member said. “Those were created by their teams.” Another said, “I don’t feel bad for those that had problems. They brought it on themselves.”

There doesn’t seem to be a single definitive answer as to why those drivers had issues, but there’s a growing belief within the paddock that some teams might have been pushing the envelope with regard to how they set their braking systems up for the race.

Years ago, teams devised their own systems to keep the brake pads away from the brake discs on superspeedways like Indianapolis. Since the brakes are rarely used throughout each stint, and drivers can either lift off the throttle and let aerodynamic downforce and drag slow the cars, or downshift, there’s value in reducing even the slightest amount of friction caused by the pads and discs making undesired contact until they’re really needed. Any contact, even for a nanosecond, would create friction, and with brake friction, you lose speed, and with semi-regular friction, you have a slow car.

The generic term back then was “pullback springs,” and they did just as the name suggests: The springs pulled the brake pads away from the discs. And to get the brakes to function, drivers would need to apply some added muscle to overpower the springs and create enough clamping force so the brake caliper pistons would slam the pads into the discs.

Today, with the spec brake package supplied by PFC, teams have a built-in option to use. The days of teams making their own pullback mechanisms are long gone.

So with the PFC pad retraction kit, springs have been replaced with four little levers per caliper – two on each side – that hold the pads a pre-set distance away from the disc. Like the former pullback springs, it takes some force to overpower the levers and push the pads up against the discs.

But we have an important difference with how the spring-like levers can be set up. If you have ever walked through a door that was either spring-loaded at the hinges, or maybe walked through a revolving door that required some extra grunt to move until you got to the other side, it’s a similar principle here in terms of how hard or easy teams make it to push through the retraction levers.

The arrival of spec brakes has eliminated some of the DIY solutions seen in years past, but teams can make significant changes in brake setup. Joe Skibinski/IndyCar

Teams, through their choice of brake master cylinder sizing, and the gap they set between the pads and discs, leave each driver a unique challenge in getting their race day superspeedway brakes to clamp and slow the car. This is all based on predetermined decisions before the green flag waves, not a showcase of how some drivers are better than others at using the brakes.

This is why there’s a theory in some corners of the paddock that some teams chose to use a qualifying pad retraction setup in the race as an attempt to gain a tiny advantage by eliminating any chance of on-track friction.

It’s normal for teams to use the little levers in the race. But there’s a significant difference between setting the retraction levers to hold the pads back a minimal amount – maybe 10 or 20 thousandths of an inch away from the disc – and setting the gap at double or triple that distance like they would for qualifying. With only one car on track for qualifying and plenty of time to slowly and safely pump up the brakes before returning to pit lane, the big speed-giving gap is not an issue.

But if some teams were to try and use that bigger gap in the race, their drivers may not have enough time or good fortune to get the brakes to work while firing into pit lane when coming off Turn 4 at 220mph and had only a few seconds to build pressure. That’s where some issues could arise.

And if the pads are relatively far away from the discs, and there are strong spring-like levers pushing the pads up against the brake caliper pistons, those drivers would have to pump up the brakes to try and get the brake fluid to move and fill a void in the line behind the pistons. Think of a spray bottle that has no fluid near the spout; there’s liquid in the bottle, but it takes a few squeezes of the trigger to get that fluid up the hose and out the nozzle. Same here: there’s brake fluid in the line, but it’s not sitting and waiting at the ready to move the pistons and push the pads since the little retractor levers are holding everything well clear from the discs.

So that’s where the multiple pumps come into play – to get the fluid back out where it belongs, creating pressure on the pistons that smash the pads into the discs. That’s why, with a wider retraction gap, drivers look like they’re trying to stomp out a fire with how they’re forced to work the brake pedal to build pressure.

Hunter-Reay didn’t strike problems until his fifth stop. Unlike Wilson though, Hunter-Reay only locked his front. Motorsport Images

And here’s the rub. It’s easy to think of pumping a brake pedal being an exponential thing; where with every pump, more pressure gets built up until the brakes finally grab. But depending on master cylinder sizing, and how much fluid needs to be moved out to the pistons at the start of the process, there’s no guarantee that each pump will build adequate pressure. If a lot of fluid is moved during the first 80-percent of travel on the brake pedal, there’s only 20-percent left to try and overpower those levers and erase the big gap to the discs. And if you’ve only got the last 20-percent of pedal travel to slow the car, how would you do so in a clean and controlled manner? This is probably what we saw in the race.

When driving a road car, the normal braking process involves pushing on the brake pedal, receiving almost instant pressure, and having the full range of travel to build more pressure and modulate the force until you slow the car or come to a stop. They key here is when you have pressure – at the top of the pedal travel – and how much travel you have left to apply that force in a controlled manner. In that scenario, on the street, or in an IndyCar at the Indy 500, most are able to brake normally and without locking up the tires.

As some of the drivers possibly experienced on Sunday, there was no immediate pedal resistance due to a big retractor gap. And when the brakes did finally start to work, the pedal was so close to the floor, there wasn’t enough pedal travel left to properly modulate the force.

But again, there is no single theory here that explains every problem. There was a lot of randomness: Stefan Wilson’s car was the first to have problems as he had a ton of rear braking force and not much up front; we know this because his rear wheels locked and speared him into the pit wall. This happened on his first pit stop.

After the crash, on the NBC broadcast, he mentioned pumping the brakes repeatedly, all to no avail, and finally, on the last desperate pump, they worked, but not in unison on all four corners, and the car turned itself into the wall. His teammate Ryan Hunter-Reay had the exact opposite happen, as his fronts locked, the rears didn’t appear to do much, and he flew through pit lane, nearly hitting Simona De Silvestro’s car. Speeding penalty; race ruined with a top five all but assured.

Hunter-Reay completed four pit stops without an issue, and on the fifth and last, he mirrored Wilson’s first, but because it was his front brakes that locked, it didn’t turn the car into the wall. And then we have Will Power and De Silvestro’s brake-related loops, and Scott McLaughlin having a similar experience to Hunter-Reay in sailing past the start of the slow-down stripe. Speeding penalty for the Kiwi, and his chances of a strong finish lost.

How many drivers got lucky and kept from adding themselves to the list? It would be optimistic to think these are the only five. Am I saying the teams that had brake problems were doing something wrong or risky? No, but don’t be surprised if IndyCar involves itself in future speedway races and sets a maximum brake pad retraction gap.