Our classics are typically a balancing act between form and function, and though many factory parts work just fine in our modified cars, sometimes we crave something that just, to be blunt, looks better. Pedals and pedal covers would fall into this category, and for the most part, fall under want way more than need. Although installing aftermarket pedals is an aesthetic deal, there's also some science involved with determining the correct pedal ratio.
As stated, there's nothing wrong with the functioning of the factory pedals, but if you've updated the look of your interior, they can seem a bit dated in appearance. Also, because our Camaro has an electronic throttle pedal (LS Swap) the pedals match in terms of style. One functional issue we did have was the throttle pedal being so much lower than the brake pedal, and this was a great opportunity to fix that.
Clayton Machine Works offers an aluminum replacement pedal assembly that bolts in place of the stock setup. Our car has a manual transmission, so the pedals are bound as a pair for the brake and clutch. You can also get the kit for an automatic, which would have one swing arm and a wider pad.
The pair of stock pedals hang on a large factory bracket under the dash. To start, we disconnected the rods connecting the pedal arms to the clutch and brake masters. We then unbolted the swing arms from the dash bracket.
Once our factory pedals were out of the car, we were able to compare them to the new pieces from Clayton. Although similar in shape, the Clayton pedals have a decidedly modern look. These pedals work on several different cars (Camaros, Chevelles, etc.) and are configured for each car by changing the bushing and spacers where the two pedals join and pivot.
On the clutch arm, there were two holes to choose from to get the right ratio (angle) on the clutch master pushrod. Right angle? Yep, like everything in life there's a right and a wrong. For hydraulic clutch systems, you want to get a 6:1 ratio (provided your clutch master is 7/8-inch bore or smaller). If this ratio is wrong, the pedal will be hard to operate. If it's really wrong, you can damage the clutch master through too much side loading. So, with some math you can find the right spot to attach the clutch rod to the pedal arm. You can see where we had to drill holes in the stock pedal arm to get the right ratio. In many cases, it will be one of the two holes provided in the Clayton arm.
But not always. You need two measurements: the length from the pivot/fulcrum of the new pedal to the pushrod hole (Y) and from the fulcrum to the center of the brake pedal (Z). This formula ends up being Y/Z = ratio. So if your pedal is 12 inches long (Z) and the pickup point is 4 inches from the center of fulcrum, then your ratio (12/4) is 3:1. Given this, you'll need to add a hole to get the right ratio for your application. A pickup point 2 inches from the fulcrum would yield the desired 6:1 ratio. If your clutch master is larger than 7/8 bore, you will need to do a little research to find the optimal ratio. Also note that if the angle to get the right ratio is too sharp there will be bind. The only way to fix the bind is to move the clutch master or check out the adjustable clutch master firewall mount from American Powertrain that lets you dial in the angle of the clutch master in relation to the firewall.
The brake pedal attaches to the brake master pushrod via this clevis. There are two holes on the brake pedal arm: an upper hole for manual brakes and a lower hole for power brakes. You can use the same math to check your ratio here as well. For power brakes, you want a ratio between 4:1 and 5:1. For manual brakes, you want a ratio between 5:1 and 7:1. Our car has manual brakes, so we used the upper hole.
For those who think visually, this should clear up how you determine your pedal ratio, and this diagram works for the brake as well as the clutch pedals.
Although Clayton does offer a traditional cable-actuated throttle pedal, our car has an electronic throttle body. As luck would have it, Clayton had us covered here as well. Before ordering this, we would advise a call to Clayton to confirm your application, ECU, and what pedal your system requires because this isn't as universal as a cable system.
The key part of this is the Accelerator Pedal Position Sensor (APPS). This has been calibrated by Clayton, so there's no need to mess with it. The biggest challenge with this pedal is mounting it to your firewall. We were ahead of the game here because we already had some structure in place to hold our existing GM pedal. The two rear holes are 3/8"-24, and the bolts are not included because the length will change based on how you mount it. The holes are 2.25 inches apart.
The kit included this pigtail extension harness to plug into our existing GM harness. They also have a harness with butt connectors and wiring diagrams to interface with many popular ECUs from GM, Ford, and Mopar.
Even though you could bolt the throttle pedal directly to your firewall, we've found that the firewall is rarely flat where you want to mount the pedal. In our car, we had a fabbed-up brace for our GM pedal. Going this route let us easily put our pedal in the perfect location. When we're done, we really should paint this.
Here you can see our stock GM pedal next to the brains of our new Clayton pedal. We simply made a plate that matched up the three mounting points of our GM pedal, and then mounted the Clayton APPS right where we wanted it. Chances are your needs will be different in terms of how you mount it, so enjoy the fabrication process that is hot rodding.
After working with several brackets, we came up with one that not only secured the new throttle pedal to the firewall, but also let us move it forward to a spot in line with the brake pedal. Once all the pedals were installed, we simply had to recheck all the fasteners and adjust the brake light switch.
The new pedals are in and the modern design certainly fits better with our updated TMI interior. Between measuring ratios, fabbing APPS brackets, and dialing everything in, we spent the good part of a full day getting these installed correctly.
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August 14, 2020 at 11:36PM
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Installing Aftermarket Pedals And Determining The Correct Ratio. - Hot Rod Network
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