At 06:00 PM 3/23/2009, Mike S wrote:
>1) Current FMVSS don't apply to our older vehicles, which are
>grandfathered. I don't see any reference in 108 (
>http://edocket.access.gpo.gov/cfr_2004/octqtr/49cfr571.108.htm ) to
>"candlepower," "cp," or "ratio." Perhaps you can provide a more
>specific citation?

The ratios were my own calculation based on the range btw minimum
tail : maximum stop and maximum tail : minimum stop.  Other than
that...from the same URL:

>  S5.1.1.6 Instead of the photometric values specified in Table 1 of
>SAE Standards J222*December 1970, or J585e September 1977, a parking
>lamp or tail lamp, respectively, shall meet the minimum percentage
>specified in Figure 1a of the corresponding minimum allowable value
>specified in Figure 1b. The maximum candlepower output of a parking lamp
>shall not exceed that prescribed in Figure 1b, or of a taillamp, that
>prescribed in Figure 1b at H or above. If the sum of the percentages of
>the minimum candlepower measured at the test points is not less than
>that specified for each group listed in Figure 1c, a parking lamp or
>taillamp is not required to meet the minimum photometric value at each
>test point specified in SAE Standards J222 or J585e respectively.

* [my addition] J222 incorporates by reference (or similar wording)
J585d and J586c for tail and stop respectively.

>2) 80 cp sounds way to high as a minimum for a stop bulb. The 1156
>is a common US stop light bulb, and puts out 32 CP.

I thought so too, but look at the values they allow for front turn
signals that are near headlights!  Could it be a mistake in
units?  Note that U,D,L,R,H in the figures mean Up, Down, Left,
Right, Horizontal.  As I understand it, Figure 1a refers to fixtures,
whereas 1b refers to the actual lamps.

>                        Figure 1a--Required Percentages of Minimum
> Candlepower of Figure 1b
>----------------------------------------------------------------------------------------------------------------
>
>Turn
>             Test points
> (deg)                                              signal     Stop
>     Parking    Tail
>----------------------------------------------------------------------------------------------------------------
>10U, 10D.................................  5L,
>5R.......................        20        20        20        20
>5U, 5D...................................  20L,
>20R.....................      12.5      12.5        10        15
>                                            10L,
> 10R.....................      37.5      37.5        20        40
>
>V............................      87.5      87.5        70        90
>H........................................  10L,
>10R.....................        50        50        35        40
>
>[[Page 274]]
>
>
>                                            5L,
> 5R.......................       100       100        90       100
>
>V............................       100       100       100       100
>----------------------------------------------------------------------------------------------------------------
>Note--Minimum design candlepower requirements are determined by
>multiplying the percentages given in this Figure
   by the minimum allowable candlepower values in Figure 1b. The
resulting values shall be truncated after one
>   digit to the right of the decimal point.
>
>
>        Figure 1b--Minimum and Maximum Allowable Candlepower Values
>------------------------------------------------------------------------
>                                                 Lighted sections
>                  Lamp                 ----------------------------------
>                                             1          2           3
>------------------------------------------------------------------------
>Stop.................................     80/300      95/360    110/420
>Tail \1\.............................      2/18       3.5/20    5.0/25
>Parking \2\..........................    4.0/125
>Red turn signal......................     80/300      95/360    110/420
>Yellow turn signal rear..............    130/750     150/900    175/1050
>Yellow turn signal front.............    200/-          240-    275/-
>Yellow turn signal front \3\.........    500/-         600/-    685/-
>------------------------------------------------------------------------
>\1\ Maximum at H or above.
>\2\ The maximum candlepower value of 125 applies to all test points at H
>   or above. The maximum allowable candlepower value below H is 250.
>\3\ Values apply when the optical axis (filament center) of the front
>   turn signal is at a spacing less than 4 in. (10 cm.) from the lighted
>   edge of the headlamp unit providing the lower beam, or from the
>   lighted edge of any additional lamp installed as original equipment
>   and which supplements the lower beam.
>
>
>     Figure 1c--Sum of the Percentages of Grouped Minimum Candlepower
>------------------------------------------------------------------------
>                                  Turn
>     Group and test points       signal      Stop     Parking      Tail
>------------------------------------------------------------------------
>1 10U-5L, 5U-20L, 5D-20L,            65         65         60         70
>  10D-5L.....................
>2 5U-10L, H-10L, 5D-10L.....        125        125         75        120
>3 H-5L, 5U-V, H-V, 5D-V, H-         475        475        420        480
>  5R.........................
>4 5U-10R, H-10R, 5D-10R.....        125        125         75        120
>5 10U-5R, 5U-20R, 5D-20R,            65         65         60         70
>  10D-5R.....................
>------------------------------------------------------------------------
>
>
>

  --
David Beierl - Providence RI USA -- http://pws.prserv.net/synergy/Vanagon/
'89 Po' White Star "Scamp"