Spring Brake Control Valves Compared
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Spring brake control must perform three functions: the release of air pressure to engage the spring brakes, an anti-compounding partnership with the service brakes, and the safe employment of the spring brakes (i.e. “modulate” the spring brakes) in the event that the service brakes fail. These functions have been evolving.
Spring Brake Control for TrucksBendix has little competition for the spring brake control valves used on a straight truck or tractor. The SR-1 valve is a basic valve that provides the modulation of the spring brakes in event of service brake failure but must be combined with a quick release valve to actuate the spring brakes. For a tandem axle the SR-1is often paired with the R-14.
The Bendix SR-7 and R-7 valves combine all of the spring brake control functions into one valve but the R-7 offers only two delivery ports and the SR-7 four ports. Follow this link to find piping illustrations that use these spring brake control valves for trucks.
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 Bendix SR-1 valve provides very basic spring brake control for trucks & tractors  Bendix SR-7 for trucks & tractors |
Spring Brake Control for Trailers
Bendix has more competition in designing spring brake valves for trailers. The most recent update in standards for emergency braking on trailers accepted that safety can theoretically be insured with no more than a single reservoir supporting both service and emergency braking. (Two reservoirs may still be required simply to provide the volume of air that is necessary.) Prior to this latest change in standards it was commonly believed that safety required two reservoirs with one reservoir being dedicated, isolated, or “protected”. The SR-2 valve uses a dedicated spring brake reservoir for release of the spring brakes. The SR-4 valve does not require a reservoir dedicated to the spring brakes but uses the service reservoirs for releasing the spring brakes. The SR-4 has not been used on new trailers since 1992. The SR-4 was superseded by the modern SR-5 which uses no reservoir at all but rather trailer supply line pressure for releasing the spring brakes. There are still trailers in service built under the older safety standard and employing two reservoirs. The Bendix SR-4, Haldex RT4, and several Sealco valves are functionally equivalent in protected reservoir systems. As you might guess from the pictures, the orientation of the ports for each of these valves is not exactly the same and some re-plumbing would be required to replace one brand with another. Of all the valves shown here only the Sealco valve 110800 is claimed to be able to replace the SR-5 valve for single reservoir applications with very minor re-plumbing The Haldex FF2 is unique in that it performs both the service brake and spring brake functions with four delivery ports for service braking and two delivery ports for spring brakes (two spring brakes are connected to a single delivery port).
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 Sealco pn 110800 replacement for Bendix SR-5  Bendix SR-4 "Old" design pn OR101622X  Sealco pn's 110170X, 110171X, and 110191X have features for supporting two-reservoir protected systems  Haldex RT4 pn KN26000X  This revised design of the SR-4 is functionally equivalent to old version simply more compact. It also was superseded by the SR-5. |
Trailer Spring Brake Control Valves In Stock
| | PN | Style | Sprng Brake Delivery | Supply port | Control pt | Reservoir A | Res. B |
| Bendix | OR102761X | SR-2 | 4 x 3/8" | 1/4" | 1/4" | 3/4" | 1/4* |
| Bendix | OR101112X | SR-4 | 4 x 3/8" | 1/4" | 1/4" | 3/4" | 1/4* |
| Bendix | OR101622X | SR-4 | 4 x 3/8" | 1/4" | 1/4" | 1/2" | 1/4* |
| Bendix | K033223 | SR-5 | 4 x 3/8" | 1/4" | 1/4" | 1/2" | 1/4" |
| Bendix | OR109615X | SR-5 | 4 x 3/8" | 1/4" | 1/4" | 3/4" | 1/4" |
| Bendix | OR109617X | SR-5 | 4 x 3/8" | 1/4" | 1/4" | 1/2" | 1/4" |
| Haldex | KN28600 | FF2 | 2 x 3/8" | 3/8" | 1/4" | 3/4" |
| Haldex | KN28601 | FF2 | 2 x 3/8" | 3/8" | 1/4" | 1/2" |
| Haldex | KN28601X | FF2 | 2 x 3/8" | 3/8" | 1/4" | 1/2" |
| Haldex | KN26000X | RT4 | 4 x 3/8" | 3/8" | 3/8" | 1/2" | 3/8" |
| Haldex | KN26010X | RT4 | 4 x 3/8" | 3/8" | 3/8 | 1/2" | 3/8" |
| Haldex | KN26020 | RT4 | 4 x 3/8" | 3/8" | 3/8" | 1/2" | 3/8" |
| Sealco | 110170X | 4 x 3/8" | 3/8" | 3/8" | 1/2" | 1/2" |
| Sealco | 110171X | 4 x 3/8" | 3/8" | 3/8" | 1/2" | 3/8" |
| Sealco | 110191X | 4 x 3/8" | 3/8" | 3/8" | 3/8" | 1/2" |
| Sealco | 110500 | 4 x 3/8" | 3/8" | 3/8" | 1/2" |
| Sealco | 110700 | 4 x 3/8" | 3/8" | 3/8" | 1/2" |
| Sealco | 110800 | 4 x 3/8" | 3/8" | 3/8" | 1/2" |
NOTES: Reservoir port A is the reservoir to which the valve attaches. Res. B is a second port for connecting to a second reservoir. SR-2 and SR-4 valves have two of these additional reservoir connections. Haldex FF2 valves also have four delivery ports to connect service brakes.
