Dear Don and Digby
Gribeauval Field Artillery
Gribeauval was only involved in the Field Artillery. He did not want even the 4-pdr let alone the Rostaing guns. He considered battlalion guns as a poor use of artillery. His objections to Marshal de Saxe concept of battlalion guns supposedly casused him to seek employment outside the French Artillery with Austria. Since 1729, no foreigner could serve in the French Artillery so it is no wonder there was a lack of innovation. Gribeauval did bring the ideas he had seen of the Austrian and Prussia Ordnance.
Therefore if we restrict this to his equipment we have [7 wheels].
Howitzer limber single draft until 1790s
8/12-pdr limber and front of caisson wheel
Caisson rear wheel
This ignores [4 wheels]
4-pdr limber wheel
Swedish 4-pdr wheel (infantry were still issued with them in war)
Rostaing 1-pdr wheel
The M1775 "Valliere" Siege guns [5 extra wheels]
M1732 Limber wheel [as Howitzer above]
M1775 Valliere Garrison Guns [10 wheels]
M1749 Gribeauval Garrison carriage had a different fore wheel and truck wheel for each calibre
M1786 reforms by Manson used the same as field/siege guns and the same truck wheel therefore only one extra wheel.
M1786 Manson Coast Guns [1 wheel]
Mounted on Meunier Carriages with one size truck wheel.
There were the same number of wheels in 1765 as 1776 = 26 wheels
This was reduced to 13 wheels by Manson according to the Manson drawings.
This hopefully clears things up a little. The Garrison guns is complex. Remember the french were still using calibres to determine their wheel wize that dated back to practices in the 16th century or before.