Tweety

So technicalities aside... We can all agree that at F4i shock with untouched shim/valves and a swapped spring would be miles better than a stock VTR shock right? And probably good enough for me until I get rich and buy an Öhlins or whatever...

Hm... And how Do you change the spring? What tools are needed? If it needs special ones I'm out... If I can get by with standard tools I'll give it a go...

killer5280

You gotta make it longer, too.

E.Marquez

No special tools needed to change the spring.. But the swap will still need a custom clevis, and the need for that part to be swapped to the new shock... For that,, you'll need some special tools and the ability to recharge the shock.

Tweety

Clevis? what part is that? Remember english isn't my first language...

Are you saying I need special tools and re-charging the shock to swap the spring?

Because the lengthening isn't a problem... That I got covered...

JamieDaugherty

Correct, the F4/F4i shocks are much better overall than the stock VTR shock.


Actually, there are special tools required to remove the springs on streetbike shocks. You need a press with a fixture to hold the shock. I can't see any way that it would be possible by hand.




I'm not sure who you've talked to, but every tuner that I know goes stiffer. If you got a copy of the RaceTech Gold Valve installation instructions you'll see that it says to go up the valving chart. When I started doing Gold Valve installation I asked them about it and they said the valving chart assumes that the correct spring rate has already been chosen for the rider weight. As the rider gets heavier the spring rate goes up and you go up the valving chart for both the compression and rebound side.

Hawkrider

I understand your logic now. I was thinking statically. You're thinking dynamically. More person + bike requires more damping regardless of spring rate.

Consider same bike, same rider, same shock. The guy comes in and says to you he wants a new heavier spring but says don't change the damping - it's perfect for him. What do you do?

JamieDaugherty

You give them what they ask for!

All joking aside, I would probably make a suggestion to go stiffer on the valving but if they don't want to go with it then that's fine with me. I think I've already said this a couple of times but it's worth repeating - most riders aren't discriminating enough to tell the difference in small changes to the valving. Greg, you could probably tell in the first 100 yards down the road. It depends on the type of rider you are and the riding you do. There is nothing wrong with taking small steps, upgrading to the CBR shock now (with the correct spring rate, that is pretty much a must-have) and then ride the bike that way for a year or two. At that point considering a valving upgrade could be the thing to do, or just keep riding it that way and enjoy yourself!

E.Marquez

Umm, yes, sorry, did not consider a press a special tool. Special tools was in the realm of a Ni charging setup, very expensive 1/4 drive torque wrench use for valve shim stacks, seal drivers, and even soft jaw vice inserts.


The press is just a big orange thing in the corner of the garage, and I tend to forget there is not one in every garage..

Jamie is of course right.. Press and a way to hold the shock in the press required. My apologies for the lack of common sense answer.

Tweety

Ok... a ten minute google session turned up these numbers... Can anybody confirm or debunk any of them? Otherwise I'll add them to the swingarm thread as useful info for possible swaps...

Edited to correct F4i/RC51

killer5280

OK. That makes sense. I was thinking of the effects on damping of changing springs for a given rider weight, but I see that the place to start is to get the correct spring for a rider and bike weight and work the damping from there.

JamieDaugherty

Something doesn't seem right about the RC51's spring rate, that's pretty low. It's the same thing as what RaceTech shows (I'm guessing that's where all of the spring rates came from). I've got the RC51 shock as 324mm long in my notes but I don't have the stroke.

One error I see is that the F4/F4i shocks are 305mm long.

Tweety

Some of the spring rates are from there yes... Altough the RC51 has been checked against numeorus sources as I was baffled by that number as well... It seems the linkage on the RC is a lot different than most making it possible for a much softer spring to keep the rear from loosing traction... I have seen it vary between 9.8 and 11.2 on sources but all say it's a lot softer than the rest... And allso its supposed to be among the longer but haven't found a number... So 324 should make sense...

The F4/F4i I have seen as 304/309/315... So I'm wondering if there migth be a difference in F4 vs F4i???

JamieDaugherty

The data I've seen shows 305mm, which also matches the numerous F4/F4i shocks I've converted. I measure each one to verify and they all match that number. There is no difference between the F4 and F4i shocks.

You have to be careful when looking at info from aftermarket companies, sometimes they show the length that they produce for that model not the actual length of the stock part.

Tweety

Well, you should have seen a few by now, so that's good enough for me

reaper

So Jamie are you working/developing a clevis that will allow the F4/F4i shock to be used on the SH?

E.Marquez

I believe he is.... Last we spoke he was still a few weeks away from being done

JamieDaugherty

Yep, I'm still working on it. In fact, I spent some time this weekend prototyping parts for this conversion. I've still got some kinks to work out but should have something ready in a couple of months. Just in time for the spring rush!

JamieDaugherty

Just to clarify guys - I can convert a CBR600F4/F4i shock to fit the VTR right now. This conversion would have a set length that would not be adjustable. The cost for this is $175 with an additional $85 for a spring. The conversion that I am working on is an adjustable ride height version that, when ready, will cost around $250 plus the spring.

Feel free to PM me if you are interested.

smokinjoe73

So in the end. Whats the verdict. How much benefit vs hassle is the f4i conversion? I want a better than stock shock for the street & 2up riding but do you have to change springs, valves, clevis, etc? At what point is it not worth it to wind up with a not-quite-right shock??

JamieDaugherty

I guess that's all really up to you. The conversion is not that expensive relatively speaking, so it's a low-cost way to bump up the performance. In addition, the CBR shock is a better platform for future improvements because it's more easily upgraded. The only part that is changed is the lower clevis, if you don't look down there you'll never know that it's a special shock.

Again, it really depends on what you want. Personally, I think a RaceTech modified CBR shock performance ranks up there with the aftermarket race shocks. I'd make the claim that only the high level racers could tell the difference. The kicker is that it's about 1/4 the price.

Tweety

You got me thinking now Jamie... That's usualy a bad sign... It usualy ends up with me tearing my bike apart (yet again!) and becoming a poor man...

I think I have figured out a bolt on way of extending the shock to the correct lenght and getting it height adjustable... possibly... I'll go out and play with an old (and leaking) shock and see if my thinking works in practice... If it does I'll likely order up a re-sprung (possibly valved) shock from you, sans height modifications...

And It's not a reflection on your handy work... It's just a little obsession I have... I have other vehicles that I have had work done on... This is my project bike, all modifications that I know how to do will be done by me... It's a failure everytime I use an unmodified stock part or something someone else has worked on...

Yeah... I'm nuts... But it keeps me from going insane...

trinc

WoW... how cool jamie !

i bought a penske 'cause there really wasn't another 'easy' option. the stock
shock really is a POS ! i imagine you'll be busy if you could provide a valved/sprung option for just a couple hundred bucks.

tim

JamieDaugherty

I'll give you a little tip: you can't remove the lower clevis without discharging the nitrogen first. I've had several folks send me shocks because they pulled the lower clevis off only to get sprayed with oil. I've been trying to work out a way for guys to do this themselves, but no matter what it will require recharging when it's back together. The idea is not to break open the fluid side, if you do the shock would need to be completely disassembled in order to get it bled out again.

Tweety

Actually my solution is even simpler than that... No need to remove anything...

The guys over at the Vfr forums welded a spacer to the upper shock mount with a tube and that got me thinking... Take a block of alu and thread it... A long bolt from upside, through the frame and a swivel mount at the bottom to fasten to the shock... Just twist the Alu block and you can adjust +-10mm or so...

As only the few mm of adjustment will be exposed thread and with a very beefy bolt it should be ok... It's that way on the HRC prepped RC51's I have seen... And quite a few others as well...

JamieDaugherty

Sounds like it would work, just make sure it's very rigid. I get a little concerned about things folks do at the mounting points. There are some pretty huge forces going on there and deflection in a suspension system causes all sorts of nasty things. I also get concerned about parts breaking too.

Tweety

Yeah... don't worry... I'm kind of **** about those things too...
I'll have one of the mech engingineers at work look it over and run the numbers for me before I do anything...

But as the forces on that mount are longitudial (most forces are within 5 deg deflection on the shock from my measurements...), and the shock is actually in line with the mount on the VTR (not very common?) So a beefed up bolt M10/M12? in high grade steel and with a rather beefy alu block and exposed thread no more than 10mm it should be ok...

The RC51 HRC kit uses an M8 bolt and has 10mm exposed thread at baseline setup... then +/- 10mm adjustment...

JamieDaugherty

Most of the setups like that I've seen use at least an M16 thread. That's a whole bunch stronger than an M8! I certainly would not use something that small. Sure, the shock is inline but there will always be some buckling loads, especially in a dynamic system like this. Don't forget that the measured forces on that mount will be in the thousands of pounds, not hundreds.

Tweety

Well... Hence my plan on the beefy bolt... Altough I was thinking a M12 would be enough... An M16 would require drilling the hole in the frame a lot bigger... Not sure I like that idea...

Dan Cronin

RE: "I am working on is an adjustable ride height version that, when ready, will cost around $250 plus the spring" AND "RaceTech modified CBR shock ...it's about 1/4 the price".

Sorry if I'm asking the obvious but the $250 + spring cost would include the valve upgrade and the ride height adjustment, right? I'd just need to supply a shock.

Tweety

I just figured out a simpler way... Bolt the alublock to the frame solid using the stock bolt hole M10 and thread the other end with a larger thread...

Then take the stock u shaped mount and put a beefy (M14/M16) bolt instead of the M10... thread a nut close to the other side and weld it to the bolt...

The bolt can swivel and using a garden variety tool you can then thread it out to raise the rear... Still only about 10 mm of exposed thread, and a seriously beefy bolt... Should let me adjust the shock from stock lenght to plus 10-15 mm or soo...