- 2,005
- 5,135
- 113
- Location
- Portland, OR
Those of you who have not driven an A1R or A1P2 probably will not understand this post.
The C7 trucks (serial #100,001+) including both A1R and A1P2 have a different air brake pedal valve and if you have driven A0, A1, and A1R you may have noticed that the A1R trucks seem to have a brake pedal effort, feel, and modulation that is "stiff" and for lack of a better term.... "broken". Indeed when I first bought my truck I assumed that something needed to be adjusted or rebuilt, or wasn't working properly because the pedal effort was more than I could reasonably consider would be acceptable to the engineers that designed the truck......
I was wrong. The design just absolutely SUCKS, For reasons unknown to me they changed the WABCO brake pedal valve out for a Bendix E-7 rotated 90 degrees and a significantly shorter pedal and thus less mechanical advantage. Considering the entire rest of the braking system, ABS, axles, etc are 100% Meritor/WABCO this seems an odd choice. The WABCO valve is "unusual" in the US trucking market - the rebuild kit had to come from Europe. But that's also true of our wedge brakes, etc. The air brake shop local to me tells me all this stuff is "old" and they rarely see them anymore - despite my truck being a 2008.
The original pedal valve, bracket, and pedal lever was attached to the underside of the dash and had a pedal-to-pivot length of 10.5", The "new" Bendix valve was rotated 90 degrees and due to the new orientation and integrated cast aluminum pedal the length was shortened to 7.5". I find it interesting that when you search for "Bendix E-7" you get results such as this guy:
www.finditparts.com
Which has an integrated 10.5" cast aluminum pedal. Which would be great except there's no room under the dash - the pedal would hit the floor. Even with the 7.5" pedal the location is lower compared to the WABCO and my size 12 EE is very close to the brake when operating the throttle. The WABCO, being the original design, affords more room for your foot on the accelerator.
In addition to the reduction in pedal mechanical advantage, the ports on the Bendix valve are all 1/4" NPT vs. the original WABCO valve being all 3/8" NPT. Both have 1/2" tube fittings. I don't know if this is significant but I changed out the tubing fittings to 3/8" NPT instead of using reducing bushings to ensure I removed this restriction in case it did effect operation.
Fortunately the cab and dash were largely unchanged and going back to the original design is not that hard - just have to get the entire assembly including the bracket for the A0/A1 and install it. The mounting points are still the same once you remove the Bendix adapter bracket and it only requires that you properly hookup the primary and secondary circuits and then sort out mounting the MMDC without the pedal bracket.
You can see here the stark difference in the pedal pivot and the mechanical advantage of the older assembly. The two pedal assemblies are lined up with respect to the pivot locations:
The adapter bracket created to hold the rotated Bendix valve and the MMDC:
For reference this is how my truck is configured with regards to the firewall hose routing. The two on the far right go to the Emergency/Hand Brake valve and aren't related to this install:
Overall this swap has DRAMATICALLY improved the braking on my truclk. Why S&S chose to replace the original valve with the Bendix is beyond me. I can't find any good reason. If you feel your A1R brakes don't work as well as you think they should - trust me this is the fix for it.
The C7 trucks (serial #100,001+) including both A1R and A1P2 have a different air brake pedal valve and if you have driven A0, A1, and A1R you may have noticed that the A1R trucks seem to have a brake pedal effort, feel, and modulation that is "stiff" and for lack of a better term.... "broken". Indeed when I first bought my truck I assumed that something needed to be adjusted or rebuilt, or wasn't working properly because the pedal effort was more than I could reasonably consider would be acceptable to the engineers that designed the truck......
I was wrong. The design just absolutely SUCKS, For reasons unknown to me they changed the WABCO brake pedal valve out for a Bendix E-7 rotated 90 degrees and a significantly shorter pedal and thus less mechanical advantage. Considering the entire rest of the braking system, ABS, axles, etc are 100% Meritor/WABCO this seems an odd choice. The WABCO valve is "unusual" in the US trucking market - the rebuild kit had to come from Europe. But that's also true of our wedge brakes, etc. The air brake shop local to me tells me all this stuff is "old" and they rarely see them anymore - despite my truck being a 2008.
The original pedal valve, bracket, and pedal lever was attached to the underside of the dash and had a pedal-to-pivot length of 10.5", The "new" Bendix valve was rotated 90 degrees and due to the new orientation and integrated cast aluminum pedal the length was shortened to 7.5". I find it interesting that when you search for "Bendix E-7" you get results such as this guy:
Bendix 107435N Air Brake Foot Valve + Cross Reference | FinditParts
Bendix 107435N E-7™ Dual Circuit Foot Brake Valve - New, Bulkhead Mounted, with Suspended Pedal ✓ Order now for same-day shipping on eligible purchases from FinditParts.com, America's online marketplace for heavy duty parts.
www.finditparts.com
Which has an integrated 10.5" cast aluminum pedal. Which would be great except there's no room under the dash - the pedal would hit the floor. Even with the 7.5" pedal the location is lower compared to the WABCO and my size 12 EE is very close to the brake when operating the throttle. The WABCO, being the original design, affords more room for your foot on the accelerator.
In addition to the reduction in pedal mechanical advantage, the ports on the Bendix valve are all 1/4" NPT vs. the original WABCO valve being all 3/8" NPT. Both have 1/2" tube fittings. I don't know if this is significant but I changed out the tubing fittings to 3/8" NPT instead of using reducing bushings to ensure I removed this restriction in case it did effect operation.
Fortunately the cab and dash were largely unchanged and going back to the original design is not that hard - just have to get the entire assembly including the bracket for the A0/A1 and install it. The mounting points are still the same once you remove the Bendix adapter bracket and it only requires that you properly hookup the primary and secondary circuits and then sort out mounting the MMDC without the pedal bracket.
You can see here the stark difference in the pedal pivot and the mechanical advantage of the older assembly. The two pedal assemblies are lined up with respect to the pivot locations:
The adapter bracket created to hold the rotated Bendix valve and the MMDC:
For reference this is how my truck is configured with regards to the firewall hose routing. The two on the far right go to the Emergency/Hand Brake valve and aren't related to this install:
Overall this swap has DRAMATICALLY improved the braking on my truclk. Why S&S chose to replace the original valve with the Bendix is beyond me. I can't find any good reason. If you feel your A1R brakes don't work as well as you think they should - trust me this is the fix for it.
Last edited:
