Is your clutch pedal slowing you down?

Want lower lap times? Right now, you can spend a few minutes dialing in the action of your clutch pedal. It’s an easy garage project.

When trying to trim down lap times, explains James Clay, president of BimmerWorld, properly timing the clutch engagement is very important. 

“And to do that,” he continues, “it is critical to put the stop just slightly below the release of the pedal. Too high and you wear out your clutch or, worse, your transmission synchros. Too low and there is no way you can get your pedal timing right, and the long travel will take too much time–plus, you also beat up your clutch and driveline because of shock caused by poor timing.”

The data backs up those claims. An accomplished driver can shift gears in half a second, Clay says. “A driver that is good and focused on shifting quickly takes 0.4 seconds,” he adds. “Our gold standard for a pro-level driver with some lighter-weight equipment–clutch and flywheel–is about 0.25 seconds.”

So, about those faster lap times: The BimmerWorld team has found that those quicker shifts can raise straightaway speeds by up to 3 or 4 mph. 

Here’s the data to back up those claims. These graphs compare two drivers on VIR’s back straight. 

Click on either graph to open in a new window.

From the top, the data cells show speed on track, throttle pedal position, engine speed, and total time gained/lost. The lower chart is just a zoomed-in version of the top one. “The zoom better shows the resolution of the throttle trace and rpm spike in that shift,” Clay explains. 

“Before the first shift on the back straight–third to fourth–both drivers are approximately the same speed,” he explains. “After the first shift, the blue driver is 2 mph faster than the red immediately.”

Clay dives deeper into the data: “In this shift, red comes off throttle at 1:19.766, back on at 1:20.269–almost exactly 0.5 seconds. Blue comes off throttle at 1:19.928, back on at 1:20.269–about 0.3 seconds.”

“Note that clutch pressure would be an interesting data point also,” he continues, “and the blue driver shows the negative effects of shifting too fast: trying to jam all the actions of the sequence in. 

“The ‘shift tail’ in the rpm graph shows that the driver overlapped pedals–a big no-no. The clutch pedal was already going down before the throttle pedal was fully released, although you can see in the graph that it was more of an issue of inertia than late throttle release. 

“Nevertheless, this is one of the ways that shifting fast can damage the engine, clutch, or driveline–although adjustment of a proper clutch stop does make this much easier to time.

“Over the duration of the full back straight, and with no other factors in these runs, faster shifting and the increased terminal mph achieved has made the blue driver, who came onto the straight slower, a total of 0.3 seconds faster in this straight alone.  

“Add the front straight and the shorter middle straight and you just put at least half a second in your pocket through proper equipment adjustment and perfecting technique.”

To help dial in that clutch action, BimmerWorld has developed its “Junior Puck” Clutch Stop. It replaces the stock, tiny clutch stop–about the size of a quarter–with a meaty one based on a 2.5-inch-diameter junior hockey puck. Retail price is just $19.95, and it simply threads into place, replacing the factory stop. 

Why go wider in the first place? The heat of battle plus worn pedal bushings make it possible to miss the tiny stock stop and simply press the clutch pedal too far. The BimmerWorld stop is also longer than stock, as it’s designed to accommodate aftermarket equipment. 

“There is a tremendous art to shifting a manual car properly and fast, and from years of selling these parts and coaching drivers, I see a wide range of talent and prowess,” Clay adds. “The clutch stop is a small but critical piece in setting up even a stock clutch system that is fast and functional.”

Photography Credit: Kevin Adolf

Wait, you might be saying, I don’t have a BMW but I’d still like to get in on this action. If you can add the appropriate threaded bung, you can add this clutch stop. (And really, could you make one this nice for less money? BimmerWorld already picked out a stop that’s the right size and hardness.)

If adding your own mount, we suggest strengthening that part of the floor with some extra sheet metal or at least some fender washers. 

We fit the BimmerWorld to our BMW 318is project car–a super-simple job–and we have made our own for other cars over the years. It’s one of those little details that add up to a dialed-in machine.

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