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VTR1000F Fork Swap

RC36/VTR Fork Swap

The RC36 series featured Honda's standard brake calipers of the day, two-piston, one piece NISSIN calipers mounted on floating pins. For the majority of uses, these calipers are perfectly adequate, but they can be improved. In addition, the RC36 featured Honda's basic cartridge-type forks, made by Showa, with either no adjustments (as in the case of the '90-'91 VFR750FL-M) or adjustment for preload only (as in the case of the '92-'97 VFR750FN-V). In view of the fairly good interchangeability of parts on Honda sport bikes, the OEM forks can relatively easily be improved in order to allow for additional adjustability.

The following relates to the swap of '98 VTR1000FW forks and brakes onto the '90 VFR750FL, mainly to improve the latter's braking ability, but also to gain some degree of suspension adjustability. The VTR forks were chosen mainly because they were the only 41mm RSU-type Showa forks that featured NISSIN four-piston, two-piece brake calipers. These forks also featured adjusters for preload and rebound damping—both of which the VFR750FL lacked. It should be noted that the VTR forks are not very different from the VFR forks (or from CBR600F3 forks) in construction or operation. In fact, many VTR owners expressed considerable disappointment with the harshness of their OEM forks and had them rebuilt by suspension specialists or with valving kits, such as RaceTech Gold Valves. Consequently, the VTR forks were also rebuilt before being installed on the bike.

The size and configuration (41mm and RSU-type) of the VTR forks were considered important because these were also the specifications of the VFR750FL's OEM Showa forks. Keeping the fork tube diameter constant eliminated the need for modifying the bike's triple clamps—or for somehow swapping triple clamps from another bike as well as forks. (The CBR600F3's forks are somewhat longer than the VTR forks, and also feature preload and rebound adjustment, but they use the same brake caliper as the RC36.)

An additional consideration was the length of the forks to be swapped onto the VFR. Longer is not a real problem, but too short is. As it happens, the VTR forks are shorter than the VFR's original forks, but the difference is not so great that the VTR forks cannot be successfully swapped—but it was close! The following calculations illustrate the necessary fork length considerations:

Measurement Comments
791mm VFR750FL extended fork length (center of axle to top of stanchion tube)
- 778mm VTR1000F extended fork length (center of axle to top of stanchion tube)
= 13mm difference in extended length between VFR and VTR forks
39mm distance from top of triple clamp to top of stanchion tube on stock VFR750FL
- 13mm difference in length between VFR and VTR
= 26mm distance from top of triple clamp to top of stanchion tube with the VTR forks mounted in the same relative position as the stock VFR forks
26mm available length of stanchion tube projecting above VFR750FL triple clamp
- 33mm thickness of VFR750FL clip-ons
= (7mm) distance from top of VFR clip-ons to top of VTR stanchion tube (they do not clear)
(7mm) distance deficit to be made up
5mm typical amount VFR forks are raised in the triple clamps
+ 2mm thickness of the VTR fork cap
= 0mm installed distance between top of VFR750FL clip-on and top of VTR1000F fork cap

VFR750FL/VTR1000FW right clip-on In other words, with the equivalent of a 5mm upward fork height adjustment (a modification made by many RC36 owners), the VTR forks fit flush with the tops of the VFR clip-ons—perfect, unless you plan to use Gen-Mars... (This photo and the one to the right also show the mounting of the VTR1000FW master cylinder's remote fluid reservoir.) View from the top

There are three further considerations, however. The four-piston NISSIN brake calipers use a 14mm master cylinder, whereas the RC36 has a 12.7mm master cylinder. Although this difference is not great, the master cylinders should also be swapped in order to preserve the VTR's brake lever ratio. In addition, the VFR750 uses the front wheel from a later ('94-'97) RC36 (which is similar to, but not identical to, the CBR600F3's front wheel). The wheel from the VTR would also work, but it is a three-spoke design, so it wouldn't match the VFR's rear wheel. As was evident from a test fitting, the early RC36 front wheel probably doesn't actually need to be replaced for the swap to work, but note that the brake disks are not the same thickness (although they appeared to be mounted in the same relative position).

The final consideration is related to the front fender. The VFR and VTR forks have different fender mounting lug positions, so in order to use the original VFR front fender, spacers and some short brackets would need to be fabricated. As it happens, the VTR's red paint is the same as the early RC-36's "Italian red" (the Honda paint color code is R-157), so the easiest solution was simply to find a VTR front fender and use that. The countour of the VTR fender doesn't precisely match the styling of the rest of the bike, but it is very doubtful anyone will ever notice!

In conclusion, this swap isn't the most radical you can attempt, but it is a relatively easy upgrade to make. Most of the difficulty involved getting accurate measurements and determining exactly what would and would not fit. Yes, CBR900RR forks would have been more adjustable, but the fork tubes are larger and the forks are probably too short for the VFR. People who have done this type of swap report having to modify the fork stops (presumably because the forks would otherwise hit something...), which decreases steering lock. CBR600F4 forks would probably have been long enough, but again, have a larger diameter. CBR600F3 forks are the same diameter as the VFR's forks, but offer no braking improvement. As anyone who has ever ventured down this sort of path knows, there are many advantages to a true "bolt-on" swap... Home Copyright © 1999-2005