Prolink front spring rate

[Warwick Biggs]

Does anybody know the specs for Prolink front springs?

I appreciate that the stock springs have a progressive rate but what I want is the rating on the non progressive main spring?

My reason is for asking is that I currently have the stock springs with the softer progressive part simply cut off and then preloaded back up with spacers. However, the stock spring is still a bit too soft for my weight in racing. The manual does not provide the spring rates. I need the existing rate to work out the next stiffer rate spring.

Alternatively, how can I measure my spring ? is it simply a matter of seeing what weight (kg or lbs) compresses the spring 1 mm or fraction of an inch?

[Warwick Biggs]

Using the Race Tech calculator I see the stock spring rate is listed as 0.61 kg/mm. I presume it was the same spring used for all models as they only specify the one cbx model. Is this correct?

The recommended replacement springs for racing start with 0.7 kg/mm up to 0.95 kg/mm which is rather a wide range. Can anybody advise? Nils?

[bobcat]

I don't know what the rates were/are but I always replaced the stock springs
with Progressive Suspension (brand) springs. They have a more firm rate and
a must for racing. Another thing we used to do is cap off the air assist and add
about 10cc more fork fluid. The smaller "air atmosphere" above the oil level
compresses at a faster rate. Adjusting the oil level is like adjusting the spring
preload.
I'm sure this has been covered somewhere here before.

[NobleHops]

Rick, I am a big buck at 230#, and my preferences run to firmer damping. The RaceTech calculator ends up specifying springs at .95 kg, and I use 15w oil at 140mm of “air spring”, measured with the fork collapsed and the springs and spacers out. Be certain to stroke the assembly to bleed the air in the damper rods before you measure.

10w suspension fluid will be more plush over broken pavement, etc,

Opinions vary on the merits of progressively wound springs in forks. They are definitely softer in the first bit of travel though, The RaceTech and Hyperpro are straight-rate springs.

Hope that all helps!

N.

[Warwick Biggs]

Thanks guys. Various racers have advised progressive springs are no good for racing where you require very firm, consistent feedback. The road is different where a more compliant ride is preferable over ultimate handling.

I presume that was why Trevor Manley (who used to work with Nikko Bakker) cut off the softer end of my springs and then preloaded the remainder with 6" tubing. But it is not stiff enuf' so I am advised by Racetech to go 0.97 kg/mm or as close as I can get and that looks like Race tech's FRSP S2938095 that is 0.95kg/mm and made here by Eibach.

I have also confirmed that these springs do fit the 39 mm Prolink forks and they are also recommended for Harleys. They are about as stiff as you can get to handle the weight. I'm waiting to talk to Roly b4 ordering a set.

[NobleHops]

Rick, can you run cartridge emulators and still be legal in class? Now is the time if so.

[Warwick Biggs]

Most of my competitors do so Nils but to be brutally honest, I don't understand much more than the basics of suspension set up and even on more modern bikes with cartridge forks I just leave the settings more or less in the middle.

I have tried experimenting with high speed/low speed compression and rebound damping and just get lost. I learnt to ride fast in an age when putting a set of konis on the back was sophisticated and the thought of Cerianis on the front was downright extravagant. You wound up the preload to the max and that was it. Adjustable stuff came in after I retired from racing and all my modern roadsters have computers to look after these things. With the GSXR and NC30 I have never really applied myself or been experienced enuf' to really notice the subtle differences in most settings and I just ride around my short comings.

I've ordered a set of the stiffest springs I can get and if that keeps the cases off the deck I will be happy. Refinements can come later but I assure you that I can hear the chorus and am grateful for the advice.

[EMS]

There are a couple of "cheap" and easy alternatives to the stock Prolink forks. The CB1100Rc/Rd forks fit into the triples without mods and are an improvement because of the anti-dive. I have also bored a Prolink triple to 41mm and used VF1000R front ends. Both should be "legal" for your purpose as they are Honda "contemporary".

[Warwick Biggs]

That is interesting EMS but getting anything off a CB1100R these days is difficult and expensive because of their collectability. There are 2 just up the road in Mount Gambier that were owned by the late Wayne Von Einem (pictured earlier in my blog) but his brother-in law has ridiculous expectations as to their value.

The VF1000 is also interesting but are the forks as long as the Prolinks? It is ground clearance that I am chasing after all.

There is no restriction on what I do to the internals but other than the gold valves I would not know where to start altho' anti dive would be great.

[EMS]

I am not exactly sure, but the CB1100F fork may be somewhat similar to the CB1100Rc/Rd fork. Do not look for a CB1100Rb, which may be more prevalent down under. The VF100R fork is as longs as the Prolink fork. I have both spare VF and R forks and if shipping to AUS wouldn't be outrageously expensive, I would offer them to you. BTW, this may be a stupid question: Have you replaced the clip-on bars with "Superbike" handlebars? In doing so, you can slide down the fork tubes another 1½-2 inches in the triples to gain a tad more ground clearance.

[Warwick Biggs]

Yes, I have light alloy after market bars and still have about 8 mms left in the forks where they protrude from the top TC but to drop them any further I must either raise the rear or increase the offset of the clamps otherwise steering becomes too heavy. The rear is already up over 3" on stock and any higher will cause other problems.

So far I have not found anybody willing to make me up a one off custom set of clamps.

I appreciate your offer by the way and might take you up on it if the new springs don't get me out of trouble. Here is one of Fran's pics that I've blown up that demonstrate the CBX's biggest drawback on the track.

[bobcat]

It looks like if you lean it any farther you will run out of tire !

[NobleHops]

Rick, IMO you’re at the bike’s limit, with your heinie on the seat. Any improvement from here is going to involve your riding style, and getting your butt OFF the seat, and that’s going to be very physically demanding to change. To increase ground clearance, you are going to have to move the COG of the bike away from the ground by moving your own toward it. That’s my $.02.

N.

[EMS]

Probably not that easy to find, but I am sure they are out there: A Triple Tree with less (than yours) or zero offset to reduce the wheelbase will make steering lighter. Different stem can easily be changed.

[Warwick Biggs]

I have more in the tyres but yes, I'm at the bike's limits (as it should be in racing) which is why I have to raise those limits. Mark was 4 seconds a lap quicker which is a lot but he was skating on the cases. I was not but to match the top riders that is the bar that I have to get over. That means increasing ground clearance and improving my own riding, including getting further off the bike.

The springs well help. If I need more then the clamps are the next step. Incremental development is the path I'm trying to follow.