Miyata Rake / Offset 916, 914, 912
What happens if I increase, or decrease the rake. I know it will affect the handling, but if you have a higher number does that make it more twitchy, or always wanting to turn?
Miyata considers Rake and Offset to be the same. Increasing / decreasing rake should increase / decrease your wheelbase correspondingly. A longer wheelbase provides greater stability, a shorter wheelbase increases maneuvering / quick turning ability.
Vintage race bike wheelbases were typically at or under 990 mm (39 inches). Racers in groups (pelotons) will generally want quick maneuvering ability (shorter wheelbases). A longer wheelbase may be better suited to open road events such as a triathlon. [Sheldon Brown, Bicycling July 1985]
https://sheldonbrown.com/bridgestone/pdfs/bstone6001985.pdf
In addition to changing the wheelbase, a curved fork rake is thought to add a level of shock absorption; thus a larger rake could add both stability and comfort
Miyata 916 | Frame | Offset/Rake | Wheelbase | |
(Year not specified) | 50,52 | 50 | 975 | |
(my guess 1993) | 54,56,58 | 35 | 975 | |
| 60 | 35 | 985 | |
| 63 | 35 | 995 | |
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https://1.bp.blogspot.com/_whtVpXkKwlQ/R2CnzTQprvI/AAAAAAAAAnc/3CBst28ECSE/s1600-h/img307.jpg ;
Miyata 914 | Frame | Offset/Rake | Wheelbase | |
(Also Team frame) | 48 | 55 | 980 | |
1989 | 52, 54 . . | 50 | 990 | |
(50 & 60 omitted | 56, 58 | 45 | 995 | |
for simplicity) | 63 | 40 | 1000 | |
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https://www.miyatacatalogs.com/2007/12/miyata-catalog-1989.html
Miyata 912 . . | Frame . . | Offset/Rake | Wheelbase | |
1984 | 50 | | 999 | |
| 54 | | 1005 | |
| 57 | | 1010 | |
| 60, 63 | | 1025 | |
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Miyata Bicycle Catalogs: Miyata Catalog 1984
Lastly, with respect to forks, Nashbar offers a 1 inch threaded Carbon fork. Whatever replacement fork you buy, make sure the crown race spec matches that of your headset (eg. 26.4 mm or 27 mm).
( Nashbar Carbon 1-in Threaded Road Fork - Road Bike Forks)
(I know it's a old post, but my answer is meant to assist future internet queries)