Fork Valve Turbulence Reducing Modification

[tyrroneous]

I'm not quit sure but I think it's borderline bouncy on the slow shaft speeds. You know, the under 30 MPH small consecutive bumps. A few more miles should help figure what the adjustment will be.

Thanks for listening.

<{POST_SNAPBACK}>

I think its cool what you're doing. Keep up the good work.

One thing I'd like to mention (and I think folks already know this but the above quote sounds kinda confusing) is that when talking about high and low speed compression or rebound settings, the reference to speed is not the speed of the bike(i.e. 30 mph). It is the speed of the up and down travel of the fork/shock that matters. As an example, a sharp edged bump in the road would cause the fork to compress and extend rapidly, where as a frost heave or slow undulation in the pavement would cause the fork to travel up and down slowly.

[Baileyrock]

BR,

I can see that POV, especially from a highly skilled and experienced suspension guy who knows how to tailor the mechanism to a very fine degree of control for a given situation. 

But I also see how the shims in the Racetech stuff can act to control flow in lieu of the more traditional orifice size.  That's why they're so big/tall compared to stock stuff.  In general, it seems to work for most average riders (like me).

What I REALLY think is the case is that Racetech has found a market niche that allows "tunability" for the non-expert (like me) while greatly increasing performance over OEM stuff.  They manage to do this with only relatively few products, having just a few valve sizes and lots of shim stacks "do the work" for a very large number of bikes and conditions.  Brilliant!  But I can also see how this Exotica For The Masses would get an unfavorable response from the real pros like Phil, etc.  The experts work both ends of the equation....tuned orfice sizes, tuned shim stacks.  Racetech only works one end...the marketable end.  Voila!! 

I liken it to this:  You can go to any speed shop and afford to buy roller rockers for your small-block Chevy, and they're MUCH better than factory stamped steel units.  Now you're feeling pretty racy, huh, now that you have  Exotica For The Masses?  Or....you could go to Jessel http://www.jeselonline.com/ and spend about a billlllliiion dollars and get a REAL roller rocker valvetrain that you have absolutely no real need for with your stock engine!  :salesman:    Same thing applies to musical instruments, stereo equipment, kitchen knives.....anything.  Marketing and pricing step-functions affect all consumers. 

How fast to you want to go?  How much money you got??

I agree completely and well said Trace ! :beer:

Everything can be made to work better than the one size fits all approach that Honda uses, as you say for the masses, even stock parts can be tuned for the each rider. I'm in no way saying there's only one way to improve what we have.

Ride on! :beer:

[Baileyrock]

I'n still trying to anylize in my head what the suspenion is doing and where it is lacking. If anything I think I should have gone stiffer on the rebound stack. I'm not quit sure but I think it's borderline bouncy on the slow shaft speeds. You know, the under 30 MPH small consecutive bumps. A few more miles should help figure what the adjustment will be.

Thanks for listening.

Sounds very familiar, after having my forks built by Aftershocks the front felt so much better in many ways, but strange or worse in some especially lower speed. Felt like the front was just bouncing across everything when just cruising, but improved as I quicken pace. This is how we started talking about Shim Stacks, I was planning on installing the F4 front end because I still didn't like the feel of the Re-done forks.

I found and was told by Phil (AS) that in order to maintain the bike balance and make that stiffer front end work right, I needed to increase the rear spring rate close to the same % as I stiffend the front which was 30%(.95). I fought the idea of a hard non-compliant stiff spring rear shock for over 4-5k miles and was ready to do the F4 swap when I decided I should try the recommended rear spring first which was a 19kg for my weight (195 lbs). It transformed the bike completely, it turns in better, holds a line better, does everything better and just Rails. I'm so much more confident on it now, it's amazing.

So what I'm saying is stiffen the rear spring close to what the front was (in my case I went 25%), stop playing with the front until you do because it will change everything. You will most likely use that last inch of travel without changing anything else.

Just Do It!

Here's the link to my"Transformed" post http://www.vfrdiscussion.com/forum/index.php?showtopic=19943

[Baileyrock]

The OEM oil setting is 130mm.  The standard thinking is if you have too much spring, reduce the oil (like 130mm+ height).  If you want "more spring", you add a little oil (less than 130mm height).  Of course, there must be some solid upper and lower limits to this, like + or - 10mm or so?  Dunno.

So mebbe your 140 is fine with your 1.0 spring @ 170 lbs.  I will prolly go to 128 or so, to reduce the air volume and thus add a little more "spring".  Like I said.....it's all voodoo!!  :beer:

I don't know what it is number wise, but tuners say just enough oil to cover the damper tube when compressed is the low limit and is basically where you should start. Then if your forks bottom on a test ride, start adding 5-10mm of oil at a time until it no longer bottoms out or rarely does. :thumbsup:

[R_Cote]

As promised earlier. Here are my stack numbers.

Pulled my valves apart and they go like this.

Stock stack compression valving:

12 x .1 bleed shim

17 x .1

17 x .1

16 x .1

16 x .1

8 x .2 clamp shim

11 x .4 spacer shim

Stock rebound stack:

17 x .1

16 x .1

15 x .1

8 x .2 clamp shim

11.5 x .4 spacer shim

Now for the modified stacks.

compression

17 x .1

17 x .1

16 x .1

15 x .1

14 x .1

8 x .2 clamp shim

11.5 .4 spacer shim

Rebound stack:

17 x .1

16 x .1

16 x .1

15 x .1

8 x .2 clamp shim

11.5 x .4 spacer shim

I wanted to add a couple more to the rebound stack but I ran out of the sizes I wanted to use so I figured just adding the 1 additional 16 x .1 would stiffin it a bit over stock.

[Trace]

As promised earlier. Here are my stack numbers.

<{POST_SNAPBACK}>

Vellly intellllesting!

[R_Cote]

Vellly intellllesting!

<{POST_SNAPBACK}>

Is that all you have to say?

I think I may go with baileyrock's advice on a higher rate spring for the rear. This makes total sense. I was just under the impression that the forks were the weak link on this bike. But it makes sense that the rear would be undersprung also. Seems I can always get the proper sag by cranking on the preload but I know thats not the proper way to get the correct sag. I should have known better than that. On my dirt bike I know I have to set the race ( rider sag fully geared up ) and then check the staic sag. If the static sag does not fall into a certain area when the race sag is correct then I need a spring change. Wow. How did I miss that one. I guess I don't spend enough time on the VFR to worry about it.

Baileyrock.

Do you think the stock shock is good enough to just respring? Should I get decent results with the stock valving on the shock and a higher rate spring? All this is assuming the rear is as bad as the front was. The rear shock doesn't look like its worthy of putting money into. Did you ever have your stock shock revalved and if so how was it? Right now an aftermarket shock is out of the question for me. Some day it would be nice to put one on though. I gotta tell ya. Looking at my KTM's White power shock makes the showa look like garbage.

[R_Cote]

I also wanted to add a note.

I noticed there wasn't much mention about free sag along with the race sag.

I know in the off road world it's absolutly critical. I would think the same would apply to the street or track world.

Any thoghts on that?

[Guest 767fixer]

I also wanted to add a note.

I noticed there wasn't much mention about free sag along with the race sag.

I know in the off road world it's absolutly critical. I would think the same would apply to the street or track world.

Any thoghts on that?

<{POST_SNAPBACK}>

man you must apply to ktmtalk also.... they preach the free sag. i imagine it would apply to the street also as it best determines the correct spring rate, more than preload or any other factor. i just never see it mentioned on street bikes....also the vinegar...not only good for the rads...lol....but also cleans the windscreen well and makes for a tasty salad dressing

[Trace]

Is that all you have to say?

<{POST_SNAPBACK}>

Well, I can't write a novel every post! :D And I don't quite know what to say....I'm frantically reading all my collected material about forks, shocks, shims, handling, etc.....in hopes of finding something to say. My head is spinning!! So, I might just sit back and learn. :thumbsup:

I love your question to BR about "have you ever had your shock revalved...."!! He's had just about every shock in the Western Hemisphere on his bikes. He's the Shock Master!

Certainly the subject of F/R spring rate balance is a good one. I don't know the exact spring rate in the used Penske I bought, but I have reason to believe it's 15.5, as it was intended for a cbr954rr with a 210 lb rider. So....that means my .95 aftermarket front springs are not "balanced" from a percentage of increase stiffness aspect.

[Guest Chris_VFR]

A note to keep in mind- the 5th gen has a bleed shim, the 6th Gen has a bleed internally through the piston thread centre, like the rebound....

Static sag (at the front especially) is just as cruicial as it determines the accurate spring rate for the rider and bike. As is oil level- 120mm is good, but if you have gone a bit heavy on springs then go lower, to a max of about 140mm, past that you lose it's effect.

Hondas have always needed AT LEAST 35mm of front sag- I prefer 38mm on every bike I have ever had (up to my 5th VFR, had a firestorm, CBR600 and an XX). it helps turn and usually I don't shim the rear.

I've had 1.00 and 0.95 fork springs in my VFR's and found them too firm each time. (we have bumpy roads here in Oz) for a cheap fix I'm gonna get some CBR Blackbird forksprings and drop them in my VTEC. They are just about 0.90kg/mm and have a progressive rate. iF they don;t feel good I'll get some 0.90's.

me? I'm going to add a 17x0.10 rebound shim and go back to 5W oil. I'll leave compression stock for now. I may fine tune it to go.

Ultimately I'll end up doing the rear end (I may get a custom Ohlins with a compression clicker on a remote reservoir built), it currently has a 950lb/in spring, and works a treat. never more than a 1/8th turn of rebound IN from stock as it gets too harsh solo (on said goat tracks). 32mm sag is good. As an aside, fitting Staintunes changed the bikes handling dramatically, and I went down 2 ramps on the preload....

You need to balance your springing- always.

I am a medium-paced rider on the road. I weigh 100kg (I can hear the calculators from here guys :blink: ) This here is the exception- not the norm !:

http://www.ozvfr.net/gallery/VTEC/aam (any excuse to show it off :goofy: )

Hard luggage, esp the OEM on the 6th gen affects handling (it weighs almost 20kg on it's own)

[R_Cote]

man you must apply to ktmtalk also.... they preach the free sag.  i imagine it would apply to the street also as it best determines the correct spring rate, more than preload or any other factor.  i just never see it mentioned on street bikes....also the vinegar...not only good for the rads...lol....but also cleans the windscreen well and makes for a tasty salad dressing

<{POST_SNAPBACK}>

Absolutely.

Orange is the color of obsession.

As they say it. It's the best resource on the planet.

[Baileyrock]

  Baileyrock.

    Do you think the stock shock is good enough to just respring? Should I get decent results with the stock valving  on the shock and a higher rate spring? All this is assuming the rear is as bad as the front was. The rear shock doesn't look like its worthy of putting money into. Did you ever have your stock shock revalved and if so how was it? Right now an aftermarket shock is out of the question for me. Some day it would be nice to put one on though. I gotta tell ya. Looking at my KTM's White power shock makes the showa look like garbage.

No in general, without any adjustments and adding a 200-250 lb stiffer spring should throw the already poor valving into a frizzy!

I would suggest trying a F3 or F4 stock shock with a different spring (1000-1100 lb) to go with your fork springs and hope you can get acceptiable valving with the factory adjustments. I think I would be more worried about not having enough rebound to control the stiffer spring, but it could be close and still much better than stock IMO. That would be the cheapest route.

The next step is to watch for a Fox, Ohlins, Penske on eBay for a F2,3,4 and change springs again.

I'm using a Ohlins for a CBR F3 (eBay $300) w/19 kg spring and it seems to have no problem covering the stiffer spring within it's adjustments. Ohlins USA said they have never had to re-valve on of their shocks to cover the range of springs that might be needed for it's application. There's basically 30 clicks on both Comp & Rebound.

[Baileyrock]

Certainly the subject of F/R spring rate balance is a good one.  I don't know the exact spring rate in the used Penske I bought, but I have reason to believe it's 15.5, as it was intended for a cbr954rr with a 210 lb rider.  So....that means my .95 aftermarket front springs are not "balanced" from a percentage of increase stiffness aspect.

Hey Trace, I would offer a guess that your Penske came with a 18 kg spring for these reasons.

You say it's for a 954, OK stock 954 spring rate is like 14.3 kg and I would guess that Honda thinks the avg. rider is 160-170 lbs. You with me ?

Now you say it was set up for a 210 lb rider. Based on 170 lb factory, that's 25% heavier than stock. 25% stiffer than the stock spring (14.3 kg) is 17.87 kg which is at least how much they should have increased the rear spring rate, for racing it could easily be more. If 160 is what Honda thinks is avg. then it's a 19 kg.

So I would think your pretty close to the proper spring rate if you weigh less than 210 or so. IMO!!!!!!!!!!! :beer:

:P

[Guest VFRFun]

The OEM oil setting is 130mm.

For VTEC owners, the OEM oil level is 100mm. When I purchased new springs from Traxxion, Max McAllister recommended that I go with a level of 125mm for the VTEC because with the right springs there is less need to rely on the air shock to avoid bottoming.

Do you think the stock shock is good enough to just respring?

I'm sure most suspension tuners will tell you if you do the fork you need to do the shock too to get the value of the upgrade. From what I've read, the general consensus is that the VTEC shock is not worth the expense of re-valving and respringing. Unlike an Ohlins, Penske, Works, or Elka, it is not meant for periodic servicing.

While there is trial and error here, there is science behind this. Using a dynamometer, a tuner can model the damping characteristics for any combination of valve port size and shims. I think most tuners would opt for larger ports than HMAS because it allows more adjustability of the curve through the shim stack. The tradeoff is between traction, feel, and plushness as shown in this picture from Lee Parks book Total Control below. This is where it becomes subjective in terms of what is the right balance for each rider on the basis of the type of riding they do and the surface they ride on. A set up for sport touring on rough public roads would be different then a set up for aggressive riding on a smooth track. Because most of us aren't going to regularly rework the suspension, this is at best a compromise.

border='0' alt='user posted image' />

CompDamping.jpg

[Trace]

Hey Trace, I would offer a guess that your Penske came with a 18 kg spring for these reasons.

You say it's for a 954, OK stock 954 spring rate is like 14.3 kg and I would guess that Honda thinks the avg. rider is 160-170 lbs. You with me ?

Now you say it was set up for a 210 lb rider. Based on 170 lb factory, that's 25% heavier than stock.? 25% stiffer than the stock spring (14.3 kg) is 17.87 kg which is at least how much they should have increased the rear spring rate, for racing it could easily be more. If 160 is what Honda thinks is avg. then it's a 19 kg.

So I would think your pretty close to the proper spring rate if you weigh less than 210 or so. IMO!!!!!!!!!!! :beer:

? :P

<{POST_SNAPBACK}>

BR,

According to Racetech, the stock 954 is 14.6 (whereas you said 14.3, no biggie). But oddly enuff, their website's "spring engine" show springs from 13 to 15, no higher. Of course, that must mean that the stock 954 shock can't handle any more spring...one can assume. They show springs for 5th Gens from 6.7 (!) to 16.1. So what did Penske put on this shock that I bought from FotoMoto last September? Wellllll....I follow your logic and I hope your right. I do know that that shock/spring made a very nice difference. Smooth, comfortable, positive motion. No harshies, no bouncies, no bottoming (even two-up), ...I don't really even think about it being there, which is good! :thumbsup:

Anyway, let's hope your assumptions are right and that I stay just below 200 lbs!!

[Baileyrock]

BR,

According to Racetech, the stock 954 is 14.6 (whereas you said 14.3, no biggie).  But oddly enuff, their website's "spring engine" show springs from 13 to 15, no higher. Of course, that must mean that the stock 954 shock can't handle any more spring...one can assume.  They show springs for 5th Gens from 6.7 (!) to 16.1.  So what did Penske put on this shock that I bought from FotoMoto last September?  Wellllll....I follow your logic and I hope your right.  I do know that that shock/spring made a very nice difference.  Smooth, comfortable, positive motion.  No harshies, no bouncies, no bottoming (even two-up), ...I don't really even think about it being there, which is good!  :thumbsup:

Anyway, let's hope your assumptions are right and that I stay just below 200 lbs!!

Yah, 14 something, .3kg is like 16 lbs.

Race tech sucks :P

Of course MY logic is better than RaceTech's

Didn't Doug know what spring it had or were there any numbers on it ? :beer:

[FotoMoto]

Didn't Doug know what spring it had or were there any numbers on it ? :beer:

I don't recall what or even if it had any number on it. I could only go by what the ebay seller told me. I do know that it work mighty fine on my superhawk which requires an even higher spring rate than the vfr but I weighed about 175 so I had no problems with getting proper sag, compliance, or bottoming. FWIW.

[Trace]

Didn't Doug know what spring it had or were there any numbers on it ? :goofy:

<{POST_SNAPBACK}>

Nah....he said this, which I'm pasting from an email exchange we had last November--**From the guy I bought it from (ebay) told me that if was for a 210 lb/954 shock. I got correct sag on mine where it was so it's definitely higher than a stock 954. I'd suspect in the 16kg range but I don't know that for sure. **

In his original For Sale post on VFRd, he said *954 shock set up for a 210 rider. This puts it in prime VFR spring rate range......**

I saw no numbers on the spring.....but come to think if it, I don't remember how hard I looked for 'em, since I din't know they were there somewhere. Got a hint on typical location?

So, it's all a guess, this suspension stuff. Voodoo!!!! :beer:

Hey, wow!! There's FotoDougoto now!! I'm sure glad I didn't badmouth him or question his credibility...I'd be SOOOOoooooo embarassed! :salesman:

Edited April 6, 2006 by Trace

[fallzboater]

Hey Trace, I would offer a guess that your Penske came with a 18 kg spring for these reasons.

You say it's for a 954, OK stock 954 spring rate is like 14.3 kg and I would guess that Honda thinks the avg. rider is 160-170 lbs. You with me ?

Now you say it was set up for a 210 lb rider. Based on 170 lb factory, that's 25% heavier than stock.  25% stiffer than the stock spring (14.3 kg) is 17.87 kg which is at least how much they should have increased the rear spring rate, for racing it could easily be more. If 160 is what Honda thinks is avg. then it's a 19 kg.

So I would think your pretty close to the proper spring rate if you weigh less than 210 or so. IMO!!!!!!!!!!! :beer:

  :P

<{POST_SNAPBACK}>

Methinks you neglected to include the weight of the bike. If the bike plus 160 lb rider weighs 700 lb, adding 50 lb (210 lb rider) is only about a 7% increase, not 25%. That would be the amount to increase the spring rates, IF you think that the stock rates and f-r balance were appropriate for a 160 lb rider. I doubt it, personally. If it happens to work out that increasing both front and rear rates by 25% works out well, great, but I think it illustrates that the stock spring rates are too light for anyone but a japanese schoolgirl.

Also consider that the rider CG may not be located vertically over the bike CG. If not, a much heavier rider would change the f-r weight distribution, as well as the total weight. In addition, a heavier rider will raise the CG of the total system, and the bike will exhibit proportionally more squat and dive, so even heavier springs may be desireable.

Good thread. I'm especially interested in the home-brew shim stacks. I'm still debating whether to throw more money at my VFR, or buy either a second bike, or a different one.

[fallzboater]

http://www.ozvfr.net/gallery/VTEC/aam 

<{POST_SNAPBACK}>

Dude, your bike sounds MEAN! What the hell pipe is that? I've got to get someone to video mine with Lazers and see if it sounds near that good.

[fallzboater]

Methinks you neglected to include the weight of the bike.  If the bike plus 160 lb rider weighs 700 lb, adding 50 lb (210 lb rider) is only about a 7% increase, not 25%. 

<{POST_SNAPBACK}>

Actually, I should've said the sprung weight of the bike. So, include the bike plus rider, minus the weight of the wheels & tires, brakes, rear spindle and sprocket, half the weight of the swingarm and suspension components, etc. So, that would make a 50 lb heavier rider increase the sprung weight somewhere around 10-12%.

[Baileyrock]

Actually, I should've said the sprung weight of the bike.? So, include the bike plus rider, minus the weight of the wheels & tires, brakes, rear spindle and sprocket, half the weight of the swingarm and suspension components, etc.? So, that would make a 50 lb heavier rider increase the sprung weight somewhere around 10-12%.

:blink:

You are out there my friend, What are you smoking David ? :lol: Not that your not correct either!

But hey, I'm just guessing at everything too!

Actually, I'm just using the same formula everyone(Pros) uses to select spring rates. Like on my VFR with a stock spring rate of 15.3kg for whaterever rider and bike, now add a 195 lb rider and the Experts recommend a 19kg spring ! You tell me what % increase in rate that is ? :idea3:

That is the same formula I applied here to Trace's shock.

[Trace]

I'd rather discuss the Japanese schoolgirls....... :salesman:

[Baileyrock]

I'd rather discuss the Japanese schoolgirls....... :salesman:

:idea3:

:joystick: