Brake Fluid (Glycol-based) Resistant O-Rings
Compatibility ratings for 7 O-ring materials in Brake Fluid (Glycol-based) service
Glycol brake fluid (DOT 3/4/5.1) defeats both NBR and FKM — both rate D. This is why brake systems specify EPDM, which rates A. A reminder that material selection follows fluid chemistry, not the price ladder.
Brake Fluid (Glycol-based) (Fluids) compatibility with the seven most common O-ring elastomers, rated on the standard A/B/C/D scale: A = excellent, B = good, C = fair, D = not recommended. This data also appears in our interactive chemical compatibility chart and is available machine-readable at /api/chemicals.json.
| Material | Rating | Guidance |
|---|---|---|
| NBR | D | not recommended — rapid degradation expected |
| FKM | D | not recommended — rapid degradation expected |
| EPDM | A | excellent — recommended for continuous service |
| VMQ | B | good — suitable for most applications |
| PTFE | A | excellent — recommended for continuous service |
| FFKM | A | excellent — recommended for continuous service |
| HNBR | B | good — suitable for most applications |
Why These Ratings
- NBR (D) — documented weaknesses include “Glycol-based brake fluids.”
- EPDM (A) — documented strengths include “Glycol-based brake fluids.”
- PTFE (A) — documented strengths include “Virtually all chemicals.”
- FFKM (A) — documented strengths include “Virtually all chemicals except molten alkali metals.”
FluidsService: Concentration & Temperature Notes
This category is defined by chemistry families, not viscosity. Glycol-based fluids (brake fluid, antifreeze glycols) belong to EPDM — NBR and FKM both rate D in glycol brake fluid. Phosphate esters (Skydrol) defeat NBR, FKM and HNBR alike; only EPDM, PTFE and FFKM rate A. Never assume 'hydraulic fluid' describes a single chemistry.
Recommended
- EPDM O-rings (A)
- PTFE O-rings (A)
- FFKM O-rings (A)
Use With Caution
- VMQ O-rings (B)
- HNBR O-rings (B)
Avoid
- NBR (D)
- FKM (D)
Related Guides
Related Chemicals (Fluids)
Frequently Asked Questions
Is Brake Fluid (Glycol-based) compatible with FKM (Viton) O-rings?
FKM is rated D for Brake Fluid (Glycol-based): not recommended — rapid degradation expected. Ratings are general guidelines; concentration, temperature and exposure time all affect real-world compatibility, so validate critical applications with ASTM D471 immersion testing.
Is Brake Fluid (Glycol-based) compatible with NBR (nitrile) O-rings?
NBR is rated D for Brake Fluid (Glycol-based): not recommended — rapid degradation expected. NBR is the lowest-cost elastomer, so when it earns an A or B rating it is usually the economical default; when it rates C or D, do not substitute it for a higher-rated material to save cost.
Can I use PTFE O-rings with Brake Fluid (Glycol-based)?
PTFE is rated A for Brake Fluid (Glycol-based): excellent — recommended for continuous service. Remember that PTFE has no elastic memory — in demanding service it needs spring energization or an elastomer core (FEP/PFA encapsulation) to maintain sealing force.
What is the best O-ring material for Brake Fluid (Glycol-based)?
EPDM, PTFE, FFKM are rated A (excellent) for Brake Fluid (Glycol-based) in our compatibility data and are the recommended starting point for material selection. Final selection should also account for operating temperature, pressure and whether the seal is static or dynamic.
Can I use EPDM O-rings with Brake Fluid (Glycol-based)?
EPDM is rated A for Brake Fluid (Glycol-based): excellent — recommended for continuous service. Always confirm the specific fluid concentration and temperature before specifying EPDM for this service.
Need O-Rings for Brake Fluid (Glycol-based) Service?
Send us your fluid, concentration and temperature — our engineers will confirm the right compound. MOQ 1 piece.