Nobody else tested brake calipers up to now. We did it. Three 6-piston brake calipers had to prove that they are better than the original Harley Davidson 4-piston caliper.The results were quite interesting.
Brake calipers are one of the main players when it comes to change parts for custom bikes. When a biker makes up his mind about new wheels, most of the times in connection with a wide tail, they usually go for brake discs with a matching design. Since the original H-D calipers are not exactly design award winning, they are exchanged too, on such an occasion. High gloss polished calipers take their place, mostly upgraded ones, calipers with 6 pistons have to do the job now, more pistons-better stopping.
That’s what one would expect theoretically, a 6-piston brake should better decelerate than one with only 4 pistons. Is that the reality? The amount of pistons does not automatically qualify for a more effective brake. There are things that are a lot more important to the problem. The ratio of amplification of the hydraulics, a reasonable brake fluid routing (which transmits the pressure of the lever to the pistons) and the mechanical accuracy of the brake’s interior and its fine tuning.
For example: Pistons that are too loose can lurch and finally jam, pistons that are to tight, can lock up, especially when it gets hot and materials expand at different rates. That means that you cannot identify a good brake from looking at it, the interior qualities are important.
That’s what we wanted to dig up with a road test.
The difficulty of testing is the fact that you have to come up with a procedure that is repeatable and measurable and creates the same conditions for every test sample. The best way to do this is within a laboratory using machines. Sounds really boring! Bikers don’t ride in laboratories and they are not programmable robots.
But if you want to do a test like this, you have to create an environment with people and bikes where all test subjects are treated equally. First, all tests have to be done with the same person on the same bike, with steady road and weather conditions. But how can we guarantee that the driver always applies the same force to the brake lever?
We came up with a simple and ingenious solution. We took a bracket with a thread and a variable bolt to restrict the lever movement to a certain amount. Then we installed a pressure gauge on the brake line, so we can limit the lever action to a value that creates exactly 290,08 PSI (20 BAR) working pressure in the brake line. So you can take all differences in brake design into consideration.
To record the dynamic characteristics of all test runs, we used a black box. This setup was created by Werner Müller, a well-known manufacturer of H-D aftermarket parts and designer of one of the tested brakes. The driver was the chief editor of DREAM MACHINES magazine, which was explicitly overseeing the tests to ensure everybody got the same conditions, including the warm up procedures for the brakes.
Four runs from 49.71mph (80 km/h) to an absolute stop were made with each brake. That meant, at a given point on the road, the brake lever was violently applied towards the limiter. Small deviations from these parameters due to human influence were mathematically corrected toward 49.71 mph, with the help of the black box, to get a usable result. The test bike was standard ‘07 Harley–Davidson Softail Custom with a single disc brake in the front.
Results
Reference was the original H-D 4-piston caliper. Some may think that’s unfair, a standard brake has no chance versus a 6-piston caliper. We believed that also, but read on and see for yourself.
As a matter of fact, we learned that the H-D standard brake was second best on this test. The fancy looking Performance Machine caliper was totally out of luck, despite that, the results improved with rising temperature, the overall readings were by far the worst (see graphs).
The French contestant from Beringer also did not impress us. Only one run out of four, the first one, was comparable to the H-D brake. With increasing temperature it encountered some fading indications.
The only exemption was the Müller 6-piston caliper, and that was significant. The Müller brake made the tire screach during the braking action. At 133,86 ft (40,80m) the Müller caliper created the fastest stop in the shortest distance. The longest distance was performed by the PM caliper at 209,32 ft (63,80 m) which is a different league. The Müller brake needed 2 second less (4sec) than the PM caliper (6sec), H-D and Beringer are in between.
CONCLUSION
What a surprise! Beringer and Performance Machine do not look that good in this comparison. Beringer made 3rd place which is not satisfactory, facing current technology. Really disappointing was the PM caliper, 17% less effective than the standard H-D brake. The Harley brake finished at 2nd place and did a real sharp job. Using aftermarket pads may even improve the results a bit. The only joker was the Müller brake, showing all its advantages. The Müller caliper brakes a lot more efficient than the competitors, mathematically by 15%. The distance to stop is way shorter and the time to stop melts down significantly.
A distinct 1st Place.
