Spring rates fireblade shock

[jamiedaugherty]

Fluid does not "flow" through the piston rod. There is fluid around the adjustment needle, and this fluid is under pressure. That means if you simply removed the lowere eye the adjustment needle would pop out and you would get a nice oil bath. Unless you are into that sort of thing I'm going to assume that is not a desirable outcome.

I think if you saw every piece of both shocks laid out in front of you it would make more sense. In which case you would probably be a little disappointed in the CBR shock, it's not that much different. Depending on the year the CBR shock will either have the exact same piston as the VTR shock or a design that is even worse. The earlier 46mm shocks have very crummy valving - you would be better off with the the VTR shock in this case. The later 40mm shocks are almost identical internally.

Something to keep in mind is that both the CBR and VTR shocks offer compression damping, the CBR shock just has an external low speed adjustment for the compression direction. That's a nice feature to have but, in my opinion, probably not a reason alone to make the change. The bigger differce is the reservoir itself. The reservoir allows the shock to run cooler and therefore be more consistent performing. Those two features would be important later if you decide to get the shock revalved. My adivce is to not both switching to a CBR shock unless you revalve it for the VTR application. A revalved VTR shock will perform better than an otherwise-stock CBR shock.

I hope this helps!

[Geordie]

Thanks Jamie .. But I've no compression damping on my vtr shock ... That I can see anyway .. Only one adjuster at the bottom ? Im just after something that has more adjustment available .. If it was possible to have all the leverage forces figures for a whole range of bikes it must be possible to home in on another model of bike that would have close to the same suspension geometry forces etc as the vtr and perhaps that bike may have a standard more adjustable shock that could easily retrofit .. Im off to have a look at my old mans aprilia .. !

[jamiedaugherty]

Your shock does have compression damping, just not an external adjustment! The internal valving generates a damping force in both the compression and rebound directions. The one damping adjustment on the stock VTR shock actually had an effect on both directions at the same time.

[Geordie]

yes sorry I meant to say external damping adjuster. Right so the screw at the bottom of the vtr shock adjusts the damping on both comp and rebound strokes.. ? Thought that was just rebound .. Hmm .. Seems like im aswell just replacing the standard shock back in as is and do more homework on other shocks while on the lookout for used hagon maxtor nitro etc .. Just can't justify cost of any of these new .
I'm always having a go at these things myself .. More fun that way ;-) ill repost any wresting experiments .. !
Thanks for your input Jamie and others.
Geordie

[jamiedaugherty]

Probably not a Hagon - those perform worse than your stock VTR shock and last about a year. FYI.

[oldbikeman]

For a start the standard spring is way too hard (960lbs).I now have a Ohlins with four springs ranging 800-1000 pounds.A 850 is about right for me (10stone)but this then upsets the linkage rates and the rear end stalls in stroke.So I am back to a 960 and put up with the stiff ride.Funny thing is it works better two up but isn't cured by a softer spring.Linkage setup and spring needs looking at and is not a damper issue.

[oldbikeman]

I was thinking about doing a bit of cutting and welding but looking at the physical restraints Honda must have made the best of a bad job.Only way I can think of sorting the rear is to convert it to twin shock which aint happening.Any way you alter the bottom linkage points ties you in Knots so we're stuck with it.

[jamiedaugherty]

What makes you think that the stock spring is excessively stiff?
How do you know the shock is, as you call it, stalling in the stroke?

[oldbikeman]

Even two up it's stiff but better because I am not being thrown out of the seat and the swinging arm actually reacts to bumps .Bounce all my weight on the seat and it barely moves.A 825lb spring is ideal for me but it goes dead in the stroke under rebound.It will not preload to set sag,it just crushes the spring.The linkage movement appears to need an over strong spring to return to sag point.Some body who Knows about trigonometry,parallelograms and stuff would have a better idea.

[AMCQ46]

Even two up it's stiff but better because I am not being thrown out of the seat and the swinging arm actually reacts to bumps .Bounce all my weight on the seat and it barely moves.A 825lb spring is ideal for me but it goes dead in the stroke under rebound.It will not preload to set sag,it just crushes the spring.The linkage movement appears to need an over strong spring to return to sag point.Some body who Knows about trigonometry,parallelograms and stuff would have a better idea.

Oldbikeman,
your desription of the std spring and even the 160 spring is what I saw, very little movement and getting kicked out of the seat. but on the 145 [825lb] I dont have any problem setting sag, or returning to the initial position, so interested to compare notes on what specificaly you see when "it goes dead in the stroke under rebound".

where are you based, might be worth comparing notes and bikes to look for an optimum

[benny hedges]

Spring rates fireblade shock

sounds like a headline from The Sun!!!

[jamiedaugherty]

Sounds like you have a valving problem, not a spring problem. Kicking over bumps is never caused by the spring - FYI.

[oldbikeman]

Yes incorrect valving does cause this but not in this case.I am fitting a 7" long 850lb spring to a Proflex shock to see if there's improvement but I am not optimistic.Look where the rear cylinder is and think of the engineering nightmare when expected to produce a rising rate mono shock.Suzuki managed to kill a few folk with this problem.Ducatis have the rear cylinder tilted forward out of the way so they had a better chance of getting it right although I hear they are now tilting it back to get better traction and doing away with linkages to save space like Kawasaki have.In the nineties we expected rising rate like now we would expect upside down forks even if there is no real advantage.Bikes lately have become somthing of a fashion statement instead of the tip of engineering and science.
Mr Rant

[jamiedaugherty]

I guess my comments are that I would suggest that you clean up your valving and go with a higher rate spring. I think you will find that it does wonders for the handling out back.