Foggy-Brain Dilemma: Pairing VFR800 Front Wheel with ZX10R USD Forks (CB900F Project) - too crazy?

[kixbox]

Hi everyone,

I am at a junction and hoping to tap into some expertise before I commit too far in one direction - seeking insight and technical guidance.

I’ve dug deep into the world of VFRs and learning as I go. It’s such a fascinating machine honestly — and I wish I had one, but I don’t unfortunately.

Some context: I’m mid-way through a cafe racer build (my second) based on a 1982 Honda CB900F (frame/engine) - current setup/plan:
- Rear end: 1990 VFR750 single-sided swingarm, suspension and brake setup (an a wheel from VFR800 2006) - already in progress (probably the best design feature on my build).
- Front end: 2013 Kawasaki ZX10R forks (USD), calipers and discs (but no front wheel yet - tbd). I’m in the process of machining a custom stem and upper/lower to adapt this assembly to the CB900F frame.

Now (and unexpectedly), I have the opportunity to pick up a matching VFR800 front wheel, complete with rotors and calipers (and in excellent condition and at a really good price). I am thinking this would visually tie in perfectly with the rear and really elevate the overall design of my build.

Before I say yeah and pull the trigger — or nah and stick with my current plan (while looking for a Kawi front wheel) — I’d like to understand if and how that VFR800 front wheel could be paired with the ZX10R fork assembly without compromising geometry or braking alignment.

Some specific questions that come to mind:

- Is it possible to fit the VFR800 front wheel to ZX10R forks? I recognize the axle sizes are different i.e. ~20mm on VFR800 vs 25mm on Kawi based on research

- If yes, what would typically be required — axle swap, custom spacers, bearing changes, etc.?

- (probbaly stupid questions here) Can the ZX10R rotors be adapted to the VFR800 wheel hub (bore size could be an issue?), or is it better to retain the VFR rotors and adjust ZX10R caliper spacing to suit the VFR rotors?
>> maybe a subset question: is there a rotor that follows Honda’s 6-bolt standard but has a height offset that would make it easier to work with ZX10R calipers? Maybe even something in the 310 mm or 320 mm range?
>> conversely, could the VFR800 calipers be adapted to mount on the ZX10R forks and work with the VFR rotors? (Feels like a long shot, but I figured I’d ask.)

If this pairing isn’t practical — or ends up feeling too Frankenstein-ish — what fork options (Honda or otherwise) might pair more naturally with the 2006 VFR800 front wheel, while still keeping the performance feel of an upside-down fork?

Desired Goal:
Keep the ZX10R front end if it’s reasonably adaptable, but ensure clean alignment of axle, rotors, and calipers — and avoid hacking together mismatched components.

All that said and as I write this, I’m starting to doubt myself and wonder why I’m not just using a modern front wheel and calling it a day. But then agai, where’s the fun in building café racers if we don’t at least try something different?

So this is me, trying...before I hit a dead end.

Any insight or firsthand experience with mixing VFR800 wheels and modern USD forks would be hugely appreciated.

Thanks in advance
K

...in my garage hibernating for the season: 1978 CB750K Cafe Racer, 2019 Kawasaki H2 SX, 2018 Indian Roadmaster (and currently building a modern cafe racer on a 1982 CB900F)

 

[ex119x]

I think the VFR wheel can be made to work. Swapping out bearings for the 25mm ID and the VFR OD should not be an issue. Without looking it up, most of the bikes use off the shelf bearings, so those should be available. You will also need to fit a 25mm spacer between the bearings if the ID of the VFR one is smaller than that. Easy lathe work. The wheel spacers are also easy lathe work to center up the wheel in the forks. Brake rotors may be an issue, but mixing and matching bolt pattern, offset and diameter along with a spacer should make everything bolt up. It might be really easy or it might require some machining and expense. All in all, it should be doable.
The other concern I have with people putting VFR swingarms on CB750/900F frames is that by the time you fit all of the suspension pieces in the original swingarm pivot, the rear wheel is set way back and looks out of proportion. It also puts considerable stresses on a frame that was designed around twin shocks and skinny tires. Moving the swingarm pivot as far forward as possible and bracing the frame is a worthwhile consideration, if you are wanting to do it right.

 

[kixbox]

Thanks so much for taking the time to write this, genuinely appreciate the detailed insight.

On the front setup, that all makes a lot of sense. I figured the bearing swap and center spacer could be handled easily enough on the lathe, and your confirmation on that is really helpful. The rotor alignment is exactly the variable I was wrestling with - sounds like it’s a bit of “see how it fits, then act accordingly.” It’s reassuring to know it’s at least mechanically doable without venturing into impossible territory.

A couple of follow-up questions on the front end just to make sure I’m understanding correctly:

- In your experience, is there a preferred bearing spec (brand or type) when stepping up the ID to match the ZX10R axle?

- When mixing rotor diameters/offsets, is it generally safer to adapt rotors to the wheel or calipers to the forks? I’m trying to understand which approach tends to introduce fewer alignment headaches.

- And lastly, does changing the bearing ID and internal spacer have any meaningful impact on wheel rigidity or performance, or is that negligible if machined correctly?

Based on your input, maybe the plan could look like this (a bit repetitive but wanted to acknowledge/capture the proposed approach): start with adapting the VFR800 wheel to the ZX10R forks by swapping to a bearing with the correct 25 mm ID with VFR’s outer diameter. From there, machine a proper internal spacer to suit the new axle, followed by custom axle spacers to center the wheel between the Kawasaki USD fork legs.

For the braking setup, my thinking is to retain the VFR rotors initially and adjust caliper spacing on the ZX10R forks to suit their offset since that avoids chasing bolt-pattern compatibility or mismatched rotor bores. If rotor-to-caliper geometry ends up too far off, then the next step would be to explore Honda-pattern 6-bolt rotors with an offset and diameter closer to ZX10R spec (310–320 mm) so that the ZX10R calipers sit more naturally on the forks.

Put differently, the cleanest progression: bearings → internal spacer → axle/wheel centering → caliper spacing → rotor matching (only if needed). That gives me a phased way to test fitment without machining everything at once — and keeps the ZX10R front end intact unless the geometry truly refuses to cooperate.

On the rear end, I completely understand where you’re coming from. The VFR swingarm definitely pushes the wheel back (given the relaxed 110mm trail of the CB900 frame), and proportionally it can throw off the visual balance especially on a CB frame that already has a longish stance. I’ve hoping/planning to address that through the bodyline design (stretching while tightening the tail section, adjusting the seat-to-tank transition and visually keeping the mass balanced). This could be wishful thinking, but I'm going to try .

That said, I fully agree with you on the mechanical points about the load path and frame stress. The CB frame wasn’t built for that central shock load, so bracing the backbone and shock mount area, and tie the upper mount forward into the cradle for triangulation - will be critical math. My bigger concern is I'd like the pivot point to be higher than the wheel axle - I think it will not be that far off so that may also introduce another set of concerns. This build is going to be a fun 'ride' - of learning and experimenting.

Needless to say, really appreciate the thoughtful feedback. It’s exactly the kind of reality check that keeps a build honest. Happy to hear any additional insights you might have as I start mocking up both ends.

 

[Streetfighterkz]

I did a slow-ish skim through your two posts. (Not fast but not word for word either.)

Anyways, what is the diameter of the VFR rotor vs the Zx10 rotor? Some Zx10’s are 300, some are 310, a couple years are even 330mm, etc. IMO, since you are already machining up both top and bottom triple clamps, use the VFR rotors on a VFR wheel with the Zx10 calipers, then adjust your fork leg spacing accordingly. You may have to machine a new, longer axle, but I’m thinking you won’t need to.

As for wheel bearings, I prefer SKF or Timken personally. I use SKF industrial bearings a LOT in my machine designs for my day job.

Just my 2¢.

Later, Doug

 

[kixbox]

Doug, thanks for jumping in with this, really appreciate seeing it from from another angle as you proposed.

Your point about rotor diameter differences between ZX10R model years is a good call-out. In my case, the VFR800 rotors are 296 mm and the ZX10R rotors I have are 310 mm, so there’s a meaningful step between the two (or at least it sounds like it is). On paper, using the 296 mm VFR rotors on the VFR wheel and spacing the ZX10R calipers/fork legs accordingly does simplify the bolt-pattern and hub interface issue and the disc bore diameter which is an odd one on the VFR hub, but I’m not sure if that 14 mm reduction in diameter starts to become a limitation in terms of pad sweep, braking leverage, and overall performance. In your view, is that diameter mismatch still workable in practice, or is it smarter to stay closer to the ZX10R’s native 310 mm range? Taking your idea one step further, it could be possible to get another set of Honda 6-bolt patten and the right bore dial but in 310mm and center them to the zx10r calipers (I'm going to play with that - thanks for the idea).

I keep hearing SKF come up from people who build and machine regularly, so getting that same recommendation from someone using them in industrial designs definitely gives me confidence in choosing SKF for the ID/OD changeover. After ex119x posted his ideas, I worked it out what is needed, I'd need bearings that are 25mm ID x 47mm OD x 14mm dep (to match the VFR bearing dimension, but I am only finding 25x47x12mm vs 14mm (not sure this is an issue).

Machining a new axle isn’t the end of the world, but if there’s a path to keep the ZX10R axle and solve the spacing and bearing fit at the wheel, that’s absolutely the cleaner option as you suggest.


Thanks again for the insights - another layer of clarity to how I’m approaching this front end.

 

[ex119x]

If the VFR rotors are 296mm then it is from a 2008 or so VFR. That uses the small bolt pattern rotors and it looks like a 2010 CBr600RR also uses that bolt pattern on 310mm rotors that would probably bolt up to the VFR wheel. The needed offset is unknown at this point. The ZX10 uses a 6005 bearing which is 25x47x12 and the VFR uses a 6204 bearing which is 20x47x14, so the ZX 10 bearings will work in the VFR wheel to mount in the ZX forks. That should be a start.

 

[kixbox]

This is great - I have a plan for the bearings now, and I presume the internal spacer for a 25 mm axle is easy enough to source or machine.

Based on all the input so far, I’m feeling good about moving ahead with the VFR wheel. It should make for a fun front-end assembly project.

I really appreciate your point about using a CBR600RR 310 mm rotor since it shares the small Honda bolt pattern. That gives me a clean starting option once I get to the rotor/caliper alignment stage. Out of curiosity, how do you find all this info so quickly? do you have these in y our memory bank - b/c it is impressive.

The one area I’m still trying to understand is the rotor offset. Since that’s the real unknown here, my next step is figuring out how to bridge any gap between the Honda rotor height and where the ZX10R caliper naturally sits on the forks. Where do people usually source rotor spacers/shims for a multiple thicknesses (5 mm / 10 mm / etc.)? Are there reliable off-the-shelf suppliers for these, or is this typically something you machine per application? I presume bolt length would need to change too so I'd need to source those. but spacer is the primary action here.

I’m not even sure if I’m asking this the right way, but essentially I want to prep for whatever rotor offset I end up needing once everything is mocked up. Thinking to start hunting for modular spacers now, or plan on machining them during the fit-up.

Thanks again - this helping me structure a proper strategy for the front end before I start cutting chips.

 

[ex119x]

I just looked up the respective bearing numbers on Partzilla and then searched for bearing dimensions online. I actually have most bearing dimensions written down as I have been mixing and matching wheels for years. As far as the disc bolt patterns, Honda has only used a couple of bolt patterns over the years, so if it is a small bolt pattern with the same number of bolts, it is probably the same. I just went on line and looked for a Honda from about the right era with the small bolt pattern and the 310mm diameter. I use this site to figure out a bunch of stuff; https://www.motorcyclespecs.co.za/.
The ZX10 uses radial calipers, set up for 310mm discs, so you won't need any spacers as long as you use 310mm discs. The offset may be a different issue depending on the distance between disc mounting surfaces of the ZX10 wheel vs the VFR wheel. If the VFR wheel is narrower and the Honda disc offset is smaller, then it is just a matter of spacers behind the disc to move it out. If the VFR wheel is wider or the Honda disc offset is larger, then there will be issues.
I wouldn't be trying to source any parts before you start mocking up your front end and doing some actual measurements.

 

[ex119x]

So, doing a little more internet searching, I found some numbers. Use at your own discretion, since it is internet info.
It appears that the 2013 ZX 10 has 132mm disc spacing, inside face to inside face. That is the target to hit with a Honda wheel.
It appears that a 2009 CBR600RR wheel has 132 or 133 mm spacing depending on who measured. It has 118 mm hub width with 7.5mm offset discs.
the 2008 VFR800 might have 132 mm disc spacing with 101mm hub width and 15mm offset. That does not add up to 132!!! so who knows without measuring, it also has 296mm discs.
2005 CBR1000R has 132.35 disc spacing I.

All that being said, I'd try to source a 2009 CBR600RR (other years are probably identical) wheel with discs, switch out the bearings and make new spacers and bolt it up to the ZX10 forks with the ZX10 brake calipers. But, that wheel is a 3 spoke wheel and will not match your 6 spoke rear. It looks like the CBR600F3 front wheel is the same spoke pattern and small disk bolt pattern but with 296mm discs with unknown offset, maybe 112mm hub width and 12.5mm offset, but that seems pretty wide to me. Further research might give an answer to that.
This is not new or rocket science, Googling should give you the answers you need if you are persistent and ask the same questions in multiple ways with different key words.
Ask away when you get and specific questions and I can Google some, too.

 

[kixbox]

Hi All,

Here is a quick update and some photos below. I’ve been working through the phased plan we outlined earlier: bearings → internal spacer → axle/wheel centering → caliper spacing / rotor matching (current focus).

Progress so far:
- Bearings: Installed 25×47×16mm (63005-2RS ×2). They seated perfectly in the VFR800 hub.
- Internal wheel spacer: Machined a new 25×32×86mm spacer in 6061-T6, matched exactly to the OEM VFR spacer length but sized for the GSX-R’s 25mm axle. Side note: I had to open one side of the VFR hub bore by ~3mm to allow the larger OD spacer to pass through — now fits cleanly.
- External axle spacers / wheel centering: Machined new fork-to-bearing spacers and was able to center the wheel perfectly between the GSX-R forks. Axle tightens smoothly, wheel spins true, and alignment is spot-on.

Front End Change (no effect on the plan): Originally I had a ZX-10R front end, but after teardown/cleaning, I found a hairline crack in one of the outer fork tube, bent internal tube and major pitting, seized/corroded calipers. The shop I got the assembly from was great. I returned the ZX-10R setup entirely and swapped for a much cleaner donor front end (1999 GSX-R750 a little older but its fine). I didn’t take the GSX-R wheel either (sticking with the VFR wheel), and even got some money back for that. This swap doesn’t change the plan - just gives me a better base to work from.

Now the Brakes (the part that is overwhelming me): I’ve measured everything as accurately as possible, and here’s where I stand:

- The VFR hub uses the standard Honda small 6-bolt pattern
- The 1999 GSX-R750 Tokico 6-pots are designed for 320mm rotors
- The measured offset (hub mounting face → caliper centerline) is ~10mm ±1mm → This is the exact rotor offset I need to match

My Current Options

1) “Plug and Play” dream scenario
Find a rotor that is: 320mm diameter, ~10mm offset, 6-bolt Honda pattern, 62mm center-bore (VFR). This would bolt straight to the VFR wheel and match the GSX-R calipers with no adapters. I haven’t found anything like this yet… specs from rotor makers are sparse.

2) Move the caliper inward
I could shift the caliper closer to the wheel to allow more rotor options. But… I only have 2–5mm of clearance before the caliper body touches the VFR spokes.So I might be able to make this work for some 320 mm rotors, but the margin is tight.

3) (Need feedback here)
I’m also considering adapting non-Honda rotors (e.g., early-2000s Ducati Supersport or 748/916/996/998 Brembos). Those often have: 320mm diameter, ~10mm offset, but a larger center bore and different bolt circle, which means custom adapter rings or carriers would be needed.

Where I’m stuck: Rotor manufacturers/reseallers rarely list offset (height), bolt circle diameter, center-bore. I’m struggling to find 320mm rotors that match the VFR hub without going into full custom machining territory.

I’d love the guidance. I can machine spacers and adapter plates — just trying to avoid unnecessary complexity or unsafe compromises.

Any thoughts on this or ideas? or am I stuck?

Appreciate all the help so far!

Below are some pics (mostly showing my progress, not for anything else).

View attachment IMG_8683.JPEG

View attachment IMG_8683.JPEGView attachment IMG_8676.JPEG

 

[ex119x]

It looks like a 2008 or so CBR1000RR has 320mm discs with 5mm offset and a 94mm center diameter. It might not be too difficult to make a 5mm thick spacer with the correct ID for the vfr wheel and a 94mm lip to center the disc. That should then all bolt up. Double check the year CBR since some of them are listed as having a 310mm disc diameter and later ones may be 330.

 

[Streetfighterkz]

I went back and jogged my memory. (Scary thing, I know). I’m pretty sure I tried using a VFR800 rim in a set of 91-95 Gsxr750 forks. They used a 20mm axle and 310mm rotors. I found that a set of Cbr1100XX rotors that bolted up. I’m 99% sure I still have them. PM me if you want and we can discuss.

Also, you could get axial to radial caliper adapters and depending on mix/match parts you may get away with 310mm rotors without machining.

Later, Doug