Stainless Braided PTFE V Rubber Hose

Reason for Report

To establish the benefits of Stainless Steel Braided Hose versus Rubber Hose, specifically when used in Brake applications.

Prepared by Adrian Nield Head of Engineering
17th August 2005

Test Requirements

n Volumetric Expansion – This test is required for FMVSS 106 & SAE
J1401. The results will determine the level of brake pedal feel experienced during depression of break pedal. In addition the results will have a positive/negative effect with regard to the vehicle stopping distances (dependent on any other brake assist features incorporated within the braking system of a specific vehicle).
n Burst Pressure/Working Pressure. Required for FMVSS106 & SAE J1401
n Whip Test. Required for FMVSS106 & SAE J1401
n Hose Life Expectancy.

Results for Volumetric Expansion

Requirement as per FMVSS106
Low Expansion Hose –
- 0.33 cc/ft(1.08cc/m) @ 1000 PSI
- 0.42 cc/ft(1.38cc/m) @ 1500 PSI
- 0.61 cc/ft(2.00cc/m) @ 2900 PSI
Result -
Stainless Braided PTFE Hose –
First recordable data at 0.010% (0.0002932cc/ft) @ 4000 PSI.
Rubber Hose - Note – results may vary slightly dependent on manufacturer.
- 0.136 cc/ft @ 1000 PSI
- 0.150 cc/ft @ 1500 PSI
- 0.290 cc/ft @ 2900 PSI

Volumetric Expansion Conclusion

n Although the Rubber hose does meet the requirements of FMVSS106 it is clear from the results that the almost zero expansion rate of the braided hose cannot fail to have a positive effect on brake pedal feel/pressure at caliper and, potentially, stopping distances.
n To demonstrate the ACTUAL effect this would have we requested performance data from one of our key customers.

Results for Burst/Working Pressure

Requirement as per FMVSS106 / SAE J1401
100 % PRESSURE TEST all hose assemblies.
3000 – 3600 PSI – Hose assembly shall show no signs of leakage/rupture.
BURST TEST – required for initial approval.
4000 PSI FOR 2 minutes. Pressure is then increased to 7000 PSI.
Hose assembly shall show no signs of leakage/rupture.
Result -
Stainless Braided PTFE Hose – Burst test result 12750 – 13500 PSI
Recommended Safe working pressure 4250 PSI
Rubber Hose –
Note – Hose data supplied by other rubber hose manufacturers may vary.
Burst test results – 8000 – 9000 PSI
Recommended Safe working pressure 3600 PSI

Burst/Working Pressure Conclusion

Although the Rubber hose meets the requirements the safe working pressure quoted is no higher than the 100% pressure test requirement.
Also the burst test results give a SAFETY FACTOR OF 2.36 when divided into the quoted safe working pressure.
The Stainless Braided hose has a SAFETY FACTOR of 3.00 with a much greater burst pressure.

Results for Whip Test

Requirement;
A Hydraulic brake hose assembly shall not rupture when run continuously on a flexing machine for 35 hours.
Results;
Stainless Braided PTFE hose –
6 sets of tests carried out with varying hose lengths. Each set consists of 4 hoses.
Results range from 45 - 82 hours dependent on length of hose.
Date of tests Jan – Feb 2005
Rubber Hose –
Results stated from rubber hose manufacturer exceed 35 hours.
NB: Goodridge UK have performed internal tests on 5 rubber hose assemblies
(each from a different supplier). The results range from 15 – 27 hours.

Whip Test Conclusion

Although the UK rubber hose manufacturer states compliance to the Whip Test as per FMVSS106, our internal testing of rubber hose assemblies shows failure of hoses prior to the 35 hours minimum
requirement.
The Stainless Braid hose complies fully to the test requirement.

Hose Life Expectancy

There are no specific requirements for Hose Life Expectancy however this should be a consideration when deciding on which product should be selected for a specific application.
Results;
Stainless Braided PTFE Hose –
Guaranteed for Life of Vehicle, usually stated as150,000 miles.
This is possible due to the high quality PTFE liner and the Stainless Steel
Braid.
Rubber Hose -
3 years or 60,000 miles
Note - This is the average quoted life expectancy, We have not carried out any testing to verify this data.