I don't think they did change the fork size on the ER
The 185ER dont change much as the bike worked well for the marketing program.
Suzuki had other models to cater for people wanting change.
30mm
##TS-185 R/J/K/L/M/A/B “Sierra” (71-77)
32mm
##Suzuki
##DR-125 Z/D/E (82-84) 32 Suzuki GN-125 Z/D (82-83) 32 Suzuki GN-125 EM/EN/EP/ER/ES/ET/EV (91-97) 32 Suzuki SP-125 Z/D (82-83) 32 Suzuki TS-125 T/X (80-81) 32 Suzuki DS-185 N (79) 32 Suzuki DS-185 T (80) 32 Suzuki TS-185 N (79) 32 Suzuki TS-185 T/X (80-81)
35mm
Suzuki
RM-80 K/L/M/N/P (89-93)
RM-80 R/S/T/V/W/X/Y/K1 (94-01)
RM-100 N/T/X (79-81)
DR-125 G/H/J (86-88)
DR-125 SER/SES/SET (94-96)
RM-125 M/A (75-76)
SP-125 G/H/J (86-88)
DR-200 G/H/J (86-88)
DR-200 SET/SEV/SEW/SEX/SEY/SEK1/SEK2/SK3 (96-03)
RL-250 L/M “Exacta” (74-75)
SP-250 Z/D/F (82-83, 85)
TS-250 1 “Savage” (69)
TS-250 B/C/N (77-79)
GN-400 T/XT/XX/TX/TZ (80-82)
TM-400 K/L/M “Cyclone” (73-75)
GS-450 LD (83)
GS-450 LF/LG/LH/LJ (85-88)
GT-500 A/B “Titan” (76-77)
RE-5M, A
GS-550 LX/ LZ (81-82)
GS-550 B/C/EC (77-78)
GS-550 LN/LT (79-80)
GS-550 LG (86)
GT-550 J/K “Indy” (72-73)
GT-550 K (KAYABA)/ L (73-74)
GR-650 D/XD “Tempter” (83)
GS-650 EX/EZ(81-82)
GS-650 GLX/GLZ/GLD(81-83)
GS-750 B/C/EC (77-78)
GS-750 EX/EZ (81-82)
GS-750 LT/LX (80-81)
GS-750 TZ/TD (82-83)
GT-750 J/K/L/M/A/B “Lemans” (72-77)
http://organ-donor.org/motorcycle-data/fork-tube-diameter-list/#tube35