This article is from the Bicycles FAQ, by Mike Iglesias with numerous contributions by others.
From: Eric Salathe <email@example.com>
Date: Wed, 10 Mar 1999 11:52:55 -0800 (PST)
> 1) Could someone provide a definitive answer (I have been told
> different things) about whether the newer Ultegra pedal will accept the
> same cleat (I also have the PDA525 on another bike that I would like to
> wear the same shoes with).
According to the Shimano web page FAQ:
What cleats work with which pedals?
The SM-SH70 and SM-SH71 work best with both the PD-7410 and the PD-6500.
The SM-SH51 and SM-SH55 work with the PD-M747, M636, M545, M535, M515,
M434, M323, A525, M737 and M525.
There are a couple usable combinations which can be substituted for
the recommended cleat:
PD-M747, M636 M545, M535, M515, M434 can use all cleats (70,71,51,55).
The PD-A525 and PD-M323 work with all cleats except SM-SH70.
The new SH-90, SH-81/91 and SH-82/92 are only compatible with the PD-7700,
PD-6600 and PD-5500 SPD-R type pedals.
Based on this, I made the following table, which really ought to be on
Sheldon's web page (the 70/71 cleats are the standard road-racing cleats
and 50/51 are standard two-sided pedal cleats):
M747 M636 M545 M535 M515 M434 M737 M525 A525 M323 7410 6500 SPD-R
SH70 ok ok ok ok ok ok no no no no yes yes no
SH71 ok ok ok ok ok ok no no ok ok yes yes no
SH50 yes yes yes yes yes yes yes yes yes yes no no no
SH51 yes yes yes yes yes yes yes yes yes yes no no no
SPD-R no no no no no no no no no no no no yes
So the direct answer is that only the multi-release SH71 cleat will work
both with your A525s and with Ultegra 6500 SPDs.
> 2) Does anyone have any leftover PDA525 single-sided road pedals
> for sale?
I don't see what purpose the one-sided A525s serve. Svelt one-sided
road-racing pedals make sense for the extremes of weight shaving and
corner clearance, but these are not met by the heavier and clunkier A525.
You are just giving up the two-sided convienience of the M535 or M515 with
no benefit in return except possibly the bogus claim that they are `road
pedals' not `MTB pedals'