Rc51 (Sp1/sp2) Forks Vs. Cbr1000Rr Forks

I've been commuting to work in London a few days a week and, though my "hot rod" FP is holding up, I've pretty much decided that I need another VFR...  :wacko:

[image: honda-vfr-800-fi-07.jpg]

So, why not the exact same year and model I already know and love?  :happy:

And that means mods! 

So, do I go down the "tried and true" path to USD enlightenment?  Or do I really push the boat out, throw caution to the wind and experiment with another variety of early 21st Century Showa forks?

I have a set of 1000RR forks (I think they're usable), but when I took them apart years ago I recall thinking they seemed like cheapo imitations compared with the obvious quality of my SP1 forks.  But are they really worse?  I'm curious if anyone knows the answer to that?  Do the radial brake calipers make up for any difference?

(I've noticed that Honda has helpfully manufactured both a CBR954RR and a CBR600RR in the VFR's lovely PB-215C Candy Tahitian blue, so I can easily fit a matching mudguard--how convenient!)

Cheers,

I recently acquired a 2008 and I think I am going to the leave the second (or is it third?) generation LBS system intact and go with a set of cartridge inserts from Traxxion for the forks.

I would be more inclined to experiment with various newer USD options to lose the LBS if I weren't so anal about finding a set of triple clamps with with VFR offset in USD dimensions.

That being said, I do not know the answer to your question on real or perceived quality differences in the Showa offerings.

I'd go for some Showa BPF forks, regardless of manufacturer, I think they all use them now & they are he best sick design forks you can get.

I see you like the best bike in the very best colour ;)

Be aware that the 2008-> 'Blade (that has BPFs) reduced the fork width from 214 to 204. The front wheel was 5mm narrower than previously and the disc offset was also 5mm less so the 10mm fork width change was shared between the wheel and the discs.

The SP-1 and 2 (RVT) and 'Blades (prior to 2008 with USD forks) use the same 214 width and front wheel and disc mount dimensions (but with axle diameter differences), but the BPF from the later 'Blades will be a problem to fit due to the different widths noted above. Nothing's impossible, but one would need to be aware of those differences.

I believe the 204 width is used on the CBR600, so if you used the 600 yokes, then the late 'Blade BPFs with wheel and discs might be a good fit as long as they clear the frame. Unfortunately, all 'Blades use a rather short fork, a good 2" shorter than e.g. the RVT which may not then provide the desired steering geometry. As I said, nothing's impossible, but always helps to know these things beforehand.

On the subject of RVT forks, they are a useful starting point as they are long enough for use on many other bikes. But no radial caliper mounts. You can still get adapters for these (or make a hybrid with CBR1000RR lowers as I did for an SP-2, but that's another long story) or stick with the axial brakes of the RVT. Here's the thing:-

Radial mount callipers are no better than axial mount. All that talk of better load distribution is bunkum. The reason they were introduced in racing is because with radial mounting it's easy to change the disc diameter and just space the callipers accordingly. I know some will view this as heresy, but that's the way it is, pure and simple. So don't dismiss axial mount calipers due to any misguided notions of their efficiency. If you want radial mounts for the bling factor, fine, just don't kid yourself about how they work.

Similarly, radial master cylinders (a nonsensical description in any case) are used as it allows for greater mechanical leverage. The braking power available is solely due to this mechanical advantage at the lever, the relative diameters of the master cylinder and calliper pistons and the diameter of the disc. How they mount and work and in which direction is irrelevant. And don't kid yourself that fitting a Brembo master cylinder will automatically improve your brakes. It may, but it may not. It depends ONLY on the physical dimensions of the lever and the piston. I've read so many times how such a change really improved the brakes, but a simple calculation revealed they actually just ended up with a harder brake feel which they 'believe' is better, but in fact they have reduced their actual braking power. Not knocking Brembo, they make good kit, as do Nissin and Tokico etc. The main difference is Brembo sell to the aftermarket. But forget the name, just make sure you choose the right dimensions. Anyway...

For many years Honda used Nissin axial mount calipers, e.g. on the RVT etc. These are VERY GOOD callipers, but not all the same size piston, whereas all radial mounts Honda have used are 30/32mm pistons. The SP-1 were 32/34, same as for the RRW and RRX 'Blades (just different colours). The SP-2 changed to the now ubiquitous 30/32 and same as the 954 'Blade. The 929 'Blade was odd with 30/34 pistons and the CBR600s? I've no idea. The point I'm making is that although they may look the same, they may not be. They're all very good callipers and will work, but unless some thought is given to the disc size and especially the master cylinder piston size, you may not achieve optimum braking. Don't forget, the harder the brake, the less actual braking force is available and the corollary of that is that softer brakes means greater braking force is available. Obviously there are limits in practice and using harder lines can reduce the softness, so you are able to achieve great braking yet not too soft.

One last point about OEM brake lines. Any expansion of the brake hose during braking does NOT reduce the pressure and hence braking force as is often thought. What is does cause is greater lever travel. So soft lines that then expand under braking can allow a lever to come back to the bars. What you want is to maximise braking force, while not allowing the lever to move too far. As with so many things, it's a compromise. Honda want to provide good brakes, but make it hard to lock the wheel and on the whole they do a pretty good job. But it's always possible to tweek them for personal preference.

Finally, the VFR800 (well, most of them) use a 1/2" master cylinder which is too small for most of the callipers I mention above. Terrific force available, but too soft and tend to come back and hit the bars. However, the very common 14mm master cylinder works very well with the SP-1's or CBR900RRW/X's 32/34 callipers. I've used that combination on many RVTs and they're stunning brakes. Any of the other smaller piston callipers will work, but not as well.

Happy braking.

Be aware that the 2008-> 'Blade (that has BPFs) reduced the fork width from 214 to 204. The front wheel was 5mm narrower than previously and the disc offset was also 5mm less so the 10mm fork width change was shared between the wheel and the discs.

The SP-1 and 2 (RVT) and 'Blades (prior to 2008 with USD forks) use the same 214 width and front wheel and disc mount dimensions (but with axle diameter differences), but the BPF from the later 'Blades will be a problem to fit due to the different widths noted above. Nothing's impossible, but one would need to be aware of those differences.

I believe the 204 width is used on the CBR600, so if you used the 600 yokes, then the late 'Blade BPFs with wheel and discs might be a good fit as long as they clear the frame. Unfortunately, all 'Blades use a rather short fork, a good 2" shorter than e.g. the RVT which may not then provide the desired steering geometry. As I said, nothing's impossible, but always helps to know these things beforehand.

All good stuff, Ken, which I agree with.  Just a query on the change from the '07 to '08 'Blades:  My data says the disc offset increased from 12.5mm to 15.25mm, but I don't know where I got those dimensions...

I think I now have almost all of the data for brake calipers for most sportish Hondas of the last 25 years.  The F4-on CBR600s had 34/32 pistons and 5/8" masters; the early 600RRs had 32/30 pistons and 11/16" masters (this is what I have purchased for the above "soon-to-be" VFR).  As you say, there is no way to tell from the outside which size pistons are used in similar-looking calipers, so I will measure them before I install them.  I think F4i calipers are black, and I know I have a set of silver ones somewhere, but all the rest are gold.

I would consider the more advanced BPF forks, but the shorter length would be a problem.  Besides, I already have a complete SP1 front end I could use for this bike...

Ciao,

Great Info!

Thanks for sharing guys!

:beer:   :fing02:

Consider the overall length is my suggestion.

The newer BPF forks are better no doubt, but check their overall length and think about possible fouling at full compression of the tire/fender and solid bits of the motorcycle.

... Just a query on the change from the '07 to '08 'Blades:  My data says the disc offset increased from 12.5mm to 15.25mm, but I don't know where I got those dimensions...

I think I now have almost all of the data for brake calipers for most sportish Hondas of the last 25 years.  The F4-on CBR600s had 34/32 pistons and 5/8" masters; the early 600RRs had 32/30 pistons and 11/16" masters (this is what I have purchased for the above "soon-to-be" VFR).  As you say, there is no way to tell from the outside which size pistons are used in similar-looking calipers, so I will measure them before I install them.  I think F4i calipers are black, and I know I have a set of silver ones somewhere, but all the rest are gold.

I would consider the more advanced BPF forks, but the shorter length would be a problem.  Besides, I already have a complete SP1 front end I could use for this bike...

Ciao,

My memory indicates that the disc offset (width) reduced and thinking about it again, from first principles it would need to be less to suit the '08-> narrower forks. I can check to confirm as I have both types here, but I'm very sure the offset was reduced.

Apparently the narrower fork spacing helps reduce the frontal area and hence wind resistance of the bike and also some steering inertia. But the frame needs to be designed to suit really as otherwise the narrower forks with fat USB legs can hit the frame. Not only that but the bottom yoke design can also impact on what fits what. Try to fit a flat CBR lower yoke on an RVT and it'll hit stuff. That gull wing bottom yoke is like that to clear things like the oil cooler, rad etc. Fortunately for us, these variations mean there's probably something out there that will fit almost anything we want. 

I didn't realise the 600 ever used the 32/34 calipers, but I never had anything to do with the 600s. The 11/16" master cylinder is one of the crossover type. The lever design is such that they are virtually the same ratio as the later radials, so for all those the leverage calculation would be the same. But they are all very different from the earlier master cylinders, such as on the early 'Blades, VFR800, Firestorm, RC45 and many others. You simply cannot compare the piston size. The old style 14mm master cylinder is roughly equivalent to a 19mm in the new style (and also radials) with the longer levers.

For the RRW/X 'Blades with the 32/34 calipers, Honda used a 5/8" master cylinder (old style of course). These brakes were an improvement on the earlier 27/30 calipers with 14mm master cylinder. But as we know, the 14mm master cylinder works great with those 32/34 calipers. However, I do like very strong brakes and accept that it is possible to squeeze too hard in an emergency, something Honda have always been very keen to avoid. They try very hard to make good brakes.

Most of you won't remember the first disc brakes that simply did not work in the wet and I mean really did NOT work. Most bikes combined front discs with drum rears so you at least had some braking in the wet. The situation came to the attention of the government (Department of Transport) who thought new legislation was necessary to eliminate the problem. Fortunately they did discuss their 'Wet Weather Braking' proposals with the industry first. Honda was adamant that legislation was NOT necessary and that the notion of the problem being due to the stainless discs used was misguided and far from the truth. The oft recommended cast iron discs were not in fact the solution which in fact would be found in new better pad materials, about which they were researching and working very hard to come up with the real solution. Honda requested strongly that the DOT just hold off from introducing any legislation until the problem was really solved with new pads.

The rest as they say is history. New pad materials were developed and legislation was avoided and now years later, we don't even think to mention wet weather performance of disc brakes, it's simply not a consideration. Now that's progress.

What does puzzle me though is that Honda's main brake supplier is Nissin, hardly a surprise as they are wholly owned by Honda, but the brakes they use on the top of the range bikes are from Tokico who I believe are not similarly owned by Honda. Nissin do make radial calipers, but Honda don't use them. Odd.

Honda did use Nissin, but Tokico's are cheaper. Nissin may be owned by Honda, but they operate as a seperate company, and as required by most countries competition laws, wholly owned companies can NOT give discounts to associate companies, so Nissin sets their prices & Honda or anyone else can choose them or not.

A bit like the wet weather braking, I remember when you stripped any Japanese bike in the 70/80's EVERY part had "Made in Japan" stamped on them, you rarely see that these days with the worldwide supply chain ! With a lot of Japanese bike parts being made in their south east asia factories, where labour costs are greatly reduced.