Fork Valve Turbulence Reducing Modification

[R_Cote]

When you guys are done discussing the Japanese school girls, we need a ride report from trace.

Even though my changes are way better than stock there's still room for improvement. Still riding and trying to sort it all out.

[Baileyrock]

When you guys are done discussing the Japanese school girls, we need a ride report from trace.

Even though my changes are way better than stock there's still room for improvement. Still riding and  trying to sort it all out.

What the Fork man, get on with it! :beer:

Keep changing and posting :thumbsup: !

[Trace]

Me sooooo fooooooorky....me ruv U longtime, GI.

It will be a few (2-3) weeks until I do the whole RaceTech thing due to "other scheduling things", such as wurk. I have all the parts [springs, valves, F3 parts, etc], and I've done my homework (according to the RaceTech gods, that is) and decided upon my shim stacks [how many millimeters in a furlong?], and.....bugged RaceTech about what to do if I have F3 adjustable internals....and it's all a crapshoot! I'll bet I go off the road at the first turn I find in Florida!

I plan to go either "standard" or "soft" with the comp and rebound damping, as I think too many would-be suspension experts all think they're tuning for 1) a Pro, or 2) themselves.....both of which are....nonsense.

The problem with me doing any sort of suspension reporting is that I can't ride for sheeeawt! :beer:

[R_Cote]

Quote

The problem with me doing any sort of suspension reporting is that I can't ride for sheeeawt!

End Quote

Sheeeawt? I can't ride for sheeeawt either.

I'm gonna ride it a bit more and then try 10 wt oil. Just to see the effects.

Baileyrock.

Do you have a rear spring I could try? (Buy) ?

I havn't given up yet, I just don't have a lot of spare time to do this stuff. It takes me forever to just put on 500 or so miles. Hell just changing the fork oil is gonna be time consuming.

Bottom line is wer'e having fun and learning at the same time.

[Baileyrock]

Baileyrock.

  Do you have a rear spring I could try? (Buy) ?

I havn't given up yet, I just don't have a lot of spare time to do this stuff.  It takes me forever to just put on 500 or so miles. Hell just changing the fork oil is gonna be time consuming.

Bottom line is wer'e having fun and learning at the same time.

Nope, had to buy new and retail my new Ohlins spring! :beer:

[R_Cote]

BR

Is it worth it to go with a 929 shock as they are easy to come by on E-Bay? Cheap ta boot.

I know this doesn't address the spring rate issue as far as increasing it to match the increase in the fork spring rate. But it does upgrade to more adjustablity. I only ask because you've been there, done that.

[Guest Chris_VFR]

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.

<{POST_SNAPBACK}>

Staintunes nothing fancy!

[Guest ex TZ tuner]

Hi all,

With 50k approaching I decided to overhaul the front end of my '97. Tapered rollers for steering head and new bushings, seals and dust shields for the tubes. After I got it apart the following modifications transpired. (Note - I don't think anything I've ever owned was left stock..)

Drilled/tapped fluid drains into bosses at bottom of forks.

Semichrome polished the tubes.

Ported/chamfered the compression and rebound valves.

Added another .15x17mm shim next to the compression valve.

Replaced a .10x17 shim with a .15x17mm next to the rebound valve.

Used a 50/50 mixture of Honda HP 5wt and Motorex 2.5wt.

Oil level set at (gasp) 9.6 inches down from the tube top w/o spring and with cartridge/sliders fully sacked.

I also polished the valve faces progressively up to 9000grit wet/dry. The .15x17 shims I bummed were a bit rusty, so I worked them up to the 9000g as well and they slid against each other a ton better than the stock unpolished shims. Considering that the shims work by rubbing together when flexing, I went totally anal and polished all the shims up to the 9000g w/d.

I also made up some spring spacers 10mm longer, mostly because I had the ABS laying around.

Now I've been trying to understand all the great info on The Independent Bike Suspension Forum, and had formed some gut opinions and, well, just went for it.

I am the luckiest dude..the mods totally transformed the front end. No excessive brake dive and so plush that I was purposefully driving thru pot holls in amazement. Plush like a nearly flat tire: I stopped to check it. This wknd is the meet at KeithBob's in Newport, so I'll see how it all works in the twisties, loaded with camping gear..

I should add that I'm 155 w/o gear and have a Ohlins shock out back. That's pounds, and on the bike, respectively.

More to follow - maybe. :joystick:

Edited August 16, 2006 by ex TZ tuner

[The Phantom]

Excellent work, and a good write-up - thanks for sharing! That's a mighty big oil gap, but obviously it works.

9k wet/dry??? Wow, you must work in aerospace or something : )

[Guest ex TZ tuner]

Excellent work, and a good write-up - thanks for sharing! That's a mighty big oil gap, but obviously it works.

9k wet/dry??? Wow, you must work in aerospace or something : )

Hey Phantom,

Thanks for the opinion!

Though I used to work for Boeing, I now build boats (actually, we're branching out into cedar strip kayaks) and I use 320, 400, 600, 900, 1200, 1800, 2000, 2500, 4000, 6000, and 9000grit abrasives to sharpen my chisels and planes. The next step would be a leather shrop, but the edge I get with the paper system above gives me shavings I can see through. :D

J

[CornerCarver]

HELP!

I am putting my front end back together and have searched the site exhaustively. Does anyone know of the existence of a formula for determining the correct lenght for the spring spacer after a complete overhaul of the front end?

I am thinking it should be something like stock free spring length and new free spring lenght differential to find the additional lenght to add for the new spacer length. This does not take into account the difference in spring rates.

I went from stock rate to .95 kg straight rate.

[spud786]

The gold valve orifice is very open and requires the proper shim stack to slow the oil flow, if you open your stock valve up utilizing stock shim stack, might as well go ahead and throw it in the trash now.

[vfrcapn]

HELP!

I am putting my front end back together and have searched the site exhaustively. Does anyone know of the existence of a formula for determining the correct lenght for the spring spacer after a complete overhaul of the front end?

I am thinking it should be something like stock free spring length and new free spring lenght differential to find the additional lenght to add for the new spacer length. This does not take into account the difference in spring rates.

I went from stock rate to .95 kg straight rate.

Are these Racetech springs? The advice they gave me was start with new free spring/spacer length same as stock free spring/spacer length. WAY to much, felt like I was pointed at the sky. Starting with that though I progressively ended up taking off 10mm, 10mm and 5mm from the spacer, and felt it probably could have gone a little more. This was a 5th gen and their .95 springs. If you have the extra AL spacer tube or can get more that may be a starting point. Pulling the spacer out takes just a few minutes if you need to cut more down. HTH..

[CornerCarver]

Sounds like you wound up close to the stock spacer length after taking off 25mm from the recommended length.

thanks for the info Cap'n.

[Guest VFRFun]

HELP!

I am putting my front end back together and have searched the site exhaustively. Does anyone know of the existence of a formula for determining the correct lenght for the spring spacer after a complete overhaul of the front end?

I am thinking it should be something like stock free spring length and new free spring lenght differential to find the additional lenght to add for the new spacer length. This does not take into account the difference in spring rates.

I went from stock rate to .95 kg straight rate.

Here is the procedure I followed from Traxxion when I reworked my forks. It is also on their website. I ended up with a 91mm spacer on the left and a 95mm spacer on the right.

"With the fork hanging in a vise, insert one of the new springs and the washers that go above and below the spacer (some forks only require one) into the fork. Measure from the top of the washers to the top of the fork tube, and record this number (See Figure 4A). Back the preload adjuster all of the way out. Measure from the bottom of the preload adjuster (where it contacts the top washer) to the bottom edge of the top lip of the fork cap (this is the lip that will touch the fork tube when the cap is seated). Then subtract this number from the first measurement (See Figure 4C). This represents "zero preload". Add 15mm to this number. Using a tubing cutter, make your spacer this length. Deburr the ends of the spacer, and make sure that it is flat and square on both ends."

[sunline]

It is very important to set front and back suspension. I rebuilt my front end with racetech and springs, Fox shock and spring. First test ride had bike walloing all over the road. Increased preload on Fox shock till wallowing disapeared. This was after setting sag in the garage. Since then bike has tracked beautifully. Replace oil in forks every 10 or 15k. Last time I used royal purple syn auto trans fluid. 7wt I believe and works great. Dont remember all the shim stack settings, compression tube length etc. as was to long ago but bike is much better than stock. Spring rates were deduced from calculators on the web sites.

[supraman66]

Would you create a significant problem is you installed the racetech compression valve but not the rebound? I've got some pretty big pot holes around cleveland and am looking for a spring and valve solution to handle my weight but not break the bank.

[R_Cote]

Ok so it has been a little over two years since I started this valving thing. I had been wanting to redo the rebound valves since I read a post where MikeG gave reference to the Race Tech recommended shim stacks using the stock rebound valves. 2 years is too long and I apologize for my tardiness. 2 years has been long enough to get aquainted with how these stiffer 1.0 springs are too stiff for the stock valving, even though achieving the proper sag with them is easy. Wouldn't it figure how stiff this stack needs to be to overcome the heavier springs. Like wow. An incredible amount of shim resistance compared to stock. I thought it to be an excessive amount of shims but I thought I would give it a go. I just wanted to share my findings on what I came up with so far. Keep in mind this is not really tested yet, but I couldn't wait to post this up. I guess you could say I'm excited about it.

So this is what I came up with just this past week on my vacation.

I'd like to call this " My Second Valving Attempt"

Race Tech calls for this (so I’m told) on the rebound valving for the stock VFR rebound pistons using their heavier springs. So I thought I would give it a try seeing how the stock stacks with the heavier springs is very bouncy.

With 5 wt oil:

( 6 ) 17 x .15

( 1) 9 x .1 clamp shim

With 10 wt oil:

( 5 ) 17 x .15

( 1 ) 9 x .1 clamp shim

I did not have the proper quantities of 17 x .15 shims so I used the shim calculator to find out what I could substitute to achieve the equivalent, or as close to it as I could get, of their recommended stack. Just to put into perspective and give the stack a visual number to identify its overall stiffness I wrote it down and did the math. The stack stiffness for the (6) 17 x .15 = a total of 20.4 not including the clamp shim. Because a .15mm thick shim equals a stiffness factor of 3.4. (6 x 3.4 = 20.4) That’s 3.4 times as stiff as a .1mm shim.

Here is what I came up with for 5 wt oil.

LH Leg:

(3) 17 x .15 = 3 x 3.4 = 10.2

(10) 17 x .1 = 10 x .1 = 10.0

(1) 9 x .1 clamp. 20.2 total = very close to the targeted 20.4

When you start looking at the (10) 17 x .1’s, it looks a bit excessive but I am relying on the math and going with it. I will eventually get more .15 shims and switch them out if need be.

RH Leg:

(1) 18 x .2 = 1 x 8.0 = 8.0 à where one .2mm shim is 8 times stiffer than a .1mm shim.

(2) 17 x .15 = 2 x 3.4 = 6.8

(5) 17 x .1 = 5 x 1 = 5.0

(1) 9 x .1 clamp 19.8 total = close to the targeted 20.4

Preliminary ride report feels very good. Much better than the previous rebound stack, which was pretty much the stock factory stack with 1 added meaningless shim. The bounciness feels almost all gone. I'm sure it is still not balanced though, but I'm not finacially able to pop for a better rear shock yet. Pushing down on the bars ( pumping) with the brake applied is a lot less bouncy and you can hear a hydraulic shushing sound when you do this. That sound wasn’t there before. I believe the sound is the much needed rebound resistance, the sound of the oil being forced through the bleed hole at this low speed. I think this is going to work. I will wait for my first ride ( later today hopefully ) and report back .

Thanks for listening gents.

Rich.

[Baileyrock]

Welcome back to your continued testing, waiting for your results again! :mad: :goofy:

[Guest PIrat]

Thanks to all who are putting in all of this work trying to figure this "voodoo" out, and for being guinea pigs so that the rest of us lemmings can follow right along :mad:

R cote, What oil weight were you using with the stock valves and 1.0 springs? Does the racetech valve setup use the stock valve shims just in a different configuration? Or do they include a new set of shims to be configured to preference.

Correct me if I'm wrong but, heavier oil (ie 10wt) offers more flow resistance than lighter wieght (ie 5wt) right? Just making sure it's not some odd system of measurement like electrical wire gauge where smaller is bigger (Insert inappropriate SIZE joke here) :blush: .

[R_Cote]

Thanks to all who are putting in all of this work trying to figure this "voodoo" out, and for being guinea pigs so that the rest of us lemmings can follow right along :mad:

R cote, What oil weight were you using with the stock valves and 1.0 springs? Does the racetech valve setup use the stock valve shims just in a different configuration? Or do they include a new set of shims to be configured to preference.

Correct me if I'm wrong but, heavier oil (ie 10wt) offers more flow resistance than lighter wieght (ie 5wt) right? Just making sure it's not some odd system of measurement like electrical wire gauge where smaller is bigger (Insert inappropriate SIZE joke here) :blush: .

With the stock valves and heavier springs, I was using 10 wt oil. Yes the heavier oil does offer more resistace to flow but keep in mind the resistance affects both compression and rebound. I believe the stock oil is a 10 wt but I'm not sure. Changing the individual shimstacks is a better way to tune and for me it seems necessary for the rebound valve as the 1.0 springs are that much heavier than stock and they overpower the stock shimstack. You will have to buy more shims because there isn't that many in the stock valves. With this new (Race Tech recommended ) shim stack, I just put in Redline brand full synthetic suspension fluid. I went with the 130mm oil level. Still haven't been able to really test it out yet, but I did do a little 5 mile jaunt with it today and so far it feels way better than previously. Still a little bouncy but not bad at all. I definitly need to address the rear shock to get things balanced out. I think I'm headed in the right direction.

Will keep you posted.

Rich.

[R_Cote]

OK, so I was able to put on some miles this week but I still don't like it. It turns out that it is still bouncy but not as bad. So I know the heavier rebound stack is working and is working pretty good, but it is still way too stiff. I'm going to change my springs. I odered a set od .90's from Sonic Springs. What I don't understand is that 2 years ago when I checked with the Race Tech websit spring calculator I could have sworn it recommended 1.0 springs. I went back to their site the other day and inputed all my data, which is still the same and they recommend .90 springs. The funny thing is I also used the Sonic spring calculator and the same data at their site has me at the 1.0 springs. So I get a bit confused and decide to drop from the 1.0's to the .90's. I figure .90 is quite a bit heavier than stock and quite a bit less than what I have now. I think it's where I need to be. Also the Race Tech calculator gives me the rear spring rate very close to stock. Hopefully I will have the Sonic Springs next week and I can give some feedback on the results. I am totally convinced that 1.0's are too stiff for my 170lb but. Come to think of it I never did physically measure the actual spring rate. I'm assuming they were not boxed or tagged wrong. I know the most important thing to do is get the correct spring rate first and from all the feedback on here it seems convincing, by how many have gone with the .90's and .95's, that the .90's are where I should be. The stock springs are rated at .74 and I measured mined and that's exactly what they are. But they are dual rate and when I measured the second part (with double the weight compressing them) I got a reading of .88. So I feel that the stock springs could be good if one wanted to cut off the closely wound coils at the bottom. I guess this is still an option but I'm not fond of cutting springs.

Anybody know much about the second rate on the stock springs and what it is supposed to be? I think I'm pretty close at what I measured and the way I measured them, all be it the caveman method.

And the quest for the best suspension go's on. Good thing it's a fun journey, else I'd be pulling my hair out.

Rich.