Interpretation ID: nht81-1.9

DATE: FEBRUARY 3, 1981

FROM: J. KAWANO -- GENERAL MANAGER, U.S. REPRESENTATIVE OFFICE-TOYOTA

TO: FRANK BERNDT -- NHTSA CHIEF COUNSEL

TITLE: INTERPRETATION OF FEDERAL MOTOR VEHICLE SAFETY STANDARD NO. 105-75

ATTACHMT: OCTOBER 3, 1988 LETTER FROM JONES TO BURKARD, EBNER, AND TEVES, OCTOBER 9, 1981 LETTER FROM BERNDT TO KAWANO, JULY 10, 1974 LETTER FROM DYSON TO NAKAJIMA, MAY 24, 1974 LETTER FROM TEVES TO GREGORY, AND MAY 27, 1988 LETTER FROM TEVES TO JONES

TEXT: Toyota is currently considering a new type of brake reservoir, as shown in Fig. 1, in accordance with your letter enclosed herewith as Attachment #1.

We request clarification of our interpretation of @5.4.2 & 5.3.1 of FMVSS No. 105-75, concerning this type of brake reservoir.

S5.4.2 reads as follows:

Reservoirs, whether for master cylinders or for other type systems, shall have a total minimum capacity equivalent to the fluid displacement resulting when all the wheel cylinders or caliper pistons serviced by the reservoirs move from a new lining, fully retracted position (as adjusted initially to the manufacturer's recommended setting) to a fully worn, fully applied position, as determined in accordance with S7.18(c) of this standard. Reservoirs shall have completely separate compartments for each subsystem except that in reservoir systems utilizing a portion of the reservoir for a common supply to two or more subsystems, individual partial compartments shall each have a minimum volume of fluid equal to at least the volume displaced by the master cylinder piston servicing the subsystem, during a full stroke of the piston.

As far as our new type of brake reservoir is concerned, we recognize that if the following three conditions were satisfied, these reservoirs would conform to S5.4.2. Is this interpretation correct?

i) W + X + Y > C + D + E *

ii) X > A

iii) Y > B

* (Note: A vehicle equipped with this type of reservoir can be expressed as W+X+Y>C+D, since E is equivalent to zero.)

W; common capacity for fluid of front brake, rear brake & clutch as hatching part in Fig. 1

X; a compartment capacity for front brake fluid Y; a compartment capacity for rear brake fluid

A; volume displaced by front master cylinder during a full stroke of position

B; volume displaced by rear master cylinder during a full stroke of position

C; front capacity of fluid when all cylinder pistons serviced by the reservoirs from a new lining, fully retracted position to fully worn, fully applied position

D; rear capacity of fluid when all cylinder pistons serviced by the reservoirs from a new lining, fully retracted position to fully worn, fully applied position

E; clutch capacity of fluid when all cylinder pistons serviced by the reservoirs from a new lining, fully retracted position to fully worn, fully applied position

In accordance with the aforementioned interpretation, we recognize that if the warning level is not less than the level of 1/4 (W+X+Y), S5.3.1 would be satisfied. This "W" is the same volume as the "W" in expression i) of inequality. Is this interpretation correct? The main point in question is whether the "W" in expression i) of inequality can be considered the capacity in a case where the overall compartment system -- clutch included -- has not failed. We illustrate such a case in te hatching segment of Fig. 1.

We would appreciate a reply at your earliest convenience. If you should have any comments or questions, please contact Mr. M. Mori, a member of my staff, who can be reached at: (201) 865-2019. Thank you.

Enclosure.

Fig. 1. Warning level.