VTEC suspension upgrade / overhaul.

[ciprinakos]

Hi to all,

since I was with work in US, I took the opportunity to get myself the Race Tech Fork Gold Compression and Rebound Valves. I got the package with some instruction sheets and a DVD. All nice and fine but when I look in the VTEC's service manual I cannot see any of the valves (see attached diagram) nor there is any mentioning about them, hence my two questions:

- are they inside the fork damper ?

- can anyone direct me to a place/link which shows how to disassemble them ?

Some of the users here did the valve settings by themselves so I'm kindly ask to share some of their knowledge.

Many thanks!

[zRoYz]

Yes the valving is inside the damper cartridge, this may help http://forks.darladog.com/

npat the vtec standard springs are correct for a 75kg rider but you have to remember there progressive springs, for example if you fit a linear spring suited to a 75kg rider forks overall will feel stiffer (think there 0.8)

[ciprinakos]

Thanks a lot. I'll study & try to have some fun with suspension when I'll get home.

[npat]

Ok... I'm "pulling the trigger", so to speak. I've already ordered the 0.95kg/mm springs (from racetech) together with their "gold" compression and rebound valves. Tomorrow I'll place the order for a HO-605 shock from Ohlins with a 19.3kg/mm spring. As soon as they arive I will have a local suspension guy put them together using the valving suggested by racetech, and 5w oil.

Last chance to stop me if I'm doing something stupid! :laugh:

Let's hope it will be a considerable improvement, else I'm wasting a whole lot of money...

[npat]

Today I (tried to) install the Ohlins HO605 shock I just bought. Some comments:

1. The installation was a huge PITA! We had to practically strip most of the rear part of the bike. Especially painful has trying to route the hyraulic preload adjuster.

2. As it turns out the remote preload adjuster hose is too short to be routed the same way as the stock adjuster. This is most likely a problem with the specific part (assembly error?). We ordered a replacement hose (which is of the correct lenght) but now we have to wait for it to arrive with the bike half-stripped (there's no way I'm gonna put it back together only to take it appart a few days latter).

3. We replaced the stock 170N/mm spring (that came with the shock) with a 190N/mm one. With the hydraylic adjuster at the MINIMUM SETTING I measured a static sag close to 10mm, with the bike half-stripped (no exhausts, no tail covers), and a dynamic sag close to 40mm (a little less). When I remove the shock, I will try to reduce the (mechanical) minumum preload as much as I can (in order to get the same sag measurement with the hydraulic adjuster cranked-up a bit)---sadly, due to the hydraulic adjuster mechanism (colar), there it not much room for this and (I think) I will only be able to take away 2-3mm of preload. This could (potentially) be a problem if someone tries to use this shock with a stiffer spring. (I will try to verify that I didn't do something stupid and come back on this, and I will also try to measure minimum possible spring-preload)

[Baileyrock]

Does anyone know what is the stock fork-springs rate for the VTEC? I thought it was 0.75kg/mm, or is it 0.85?

The rear is 15.3, right?

.74

BR

[npat]

Does anyone know what is the stock fork-springs rate for the VTEC? I thought it was 0.75kg/mm, or is it 0.85?

The rear is 15.3, right?

.74

BR

Yes, that's the number I found in several places on the internet, but then I saw that racetech says 0.85 (I guess they are wrong)

Also, since (I think) the stock springs are dual-rate, is 0.74 the rate for the soft part of the stroke, or for the stiff?

[Baileyrock]

Just get straight rate .95's for your needs!

[npat]

Just get straight rate .95's for your needs!

I already did!

[Baileyrock]

I would have picked either a 20-21kg rear unless you plan to loose 25-30lbs.

[npat]

Today we rebuilt the forks using the Racetech 0.95 springs, Gold compression valves (c35 shim stack) and gold rebound valves (r20 shim stack). We used 5w oil (amsoil ultra light) @ 120mm and we cut the spacers for a preload of 15mm (with the adjusters at the minumum-preload position). A rough measument shows approximatelly 25mm of static sag (with the adjusters at minimum-preload, ad the rear part of the bike stripped). I haven't ridden the bike yet (obviously) but when I bounce the front I think that the rebound is faster than stock (I don't know if this is how it's supposed to be) and, naturally, it feels stiffer...

Now waiting for the Ohlins remote preload adjuster hose to arrive..

[Baileyrock]

Good stuff, keep it coming!

[npat]

Today we rebuilt the forks using the Racetech 0.95 springs, Gold compression valves (c35 shim stack) and gold rebound valves (r20 shim stack). We used 5w oil (amsoil ultra light) @ 120mm and we cut the spacers for a preload of 15mm (with the adjusters at the minumum-preload position). A rough measument shows approximatelly 25mm of static sag (with the adjusters at minimum-preload, ad the rear part of the bike stripped). I haven't ridden the bike yet (obviously) but when I bounce the front I think that the rebound is faster than stock (I don't know if this is how it's supposed to be) and, naturally, it feels stiffer...

Now waiting for the Ohlins remote preload adjuster hose to arrive..

I forgot: we also drilled 1.3mm bleed holes on both, the compression and rebound valves (exactly as recommended by racetech, for street use). Let me just note that the suspension guy that did the work (I was present, helping him) was a little reluctant with this (1.3mm bleed holes seemed a bit to much to him, and he was worried that this may result in too little damping. But since he had never worked with gold valves before, he went along assuming that racetech knows what they are doing). We also substituted the r19 rebound shim stack (recommended by racetech) with r20 (one slower).

[npat]

Bike ready! Rode it for a few miles, both in town traffic and in a twisty road I'm very familiar with, so I can share the very first impressions.

Specs, settings, and sag measurements:

REAR: HO605 ohlins shock. 190N/mm spring. SS: 7mm. RS: 35mm. Rebound: 10clicks from fully closed. Compession: 14 clicks from fully closed. Rear raised 1.5mm from stock height.

FRONT: 0.95kg/mm RaceTech springs. SS: 22mm, RS: 38mm (15mm preload by spacers plus 5.5 turns on the the adjusters from minimum). Gold comression valves (c35 shim stack with 1.3mm bleed), Gold rebound valves (r20 rebound stack with 1.3mm bleed), 5w oil (AMSOIL ultra light @ 120mm).

Impressions / comments:

I was afraid that I was going way hard on the springs. I COUNDN'T BE MORE WRONG! I could have easily gone with a 200 or even 210 rear! Never mind, there's nothing a little more compression-damping (and maybe me loosing some weight) can't fix. The bike feels plush but composed. You can open the throtle hard on corner exits, and the rear stays planted (may I need a bit more rebound and compressing damping, but even at these settings it feels very good). Bumps and potholes are absorbed with ease.

At the front I could CERTAINLY use some MORE rebound damping. After I counter-steer hard (especially if I also trail the brakes a bit) and when opening the thortle near maximum lean, the front feels a little vague for a moment (like it wants to push, especially if there's a bump or ripple near the apex), and then it stabilizes. I think with 7.5w oil, it will be perfect (or with 1mm bleed holes, instead of 1.3mm but I can't change this now). ANY SUGGESTIONS ON THIS WILL BE APPRECIATED.

Final comments: Guys weighting more than 180 / 200 lbs, and suggesting 160 / 170 N/mm springs at the rear are NUTS! Don't even think of putting anything softer than a 190. Baileyrock was absolutely spot-on.

That's all for the momment: I go waste some fuel now...

[Baileyrock]

I think with 7.5w oil, it will be perfect (or with 1mm bleed holes, instead of 1.3mm but I can't change this now). ANY SUGGESTIONS ON THIS WILL BE APPRECIATED.

Thanks for the update! Sounds like a Big improvement!

I would think you could always soder or braze those bleed holes and re-drill them the 1.0mm. The other thing you could do is install CBR F4/F4i rebound internals so at least you could adjust one side of the damping. That way you could change oil to effect the compression and adjust the rebound to work with whatever oil worked best.

Yeah, it's hard not to thing that BIG SPRING RATE CHANGE wouldn't be harsh or stiff, but it's not! The spring just supports you and the bikes weight and the damping controls the spring and transitions.

BR

[npat]

After riding some more I got convinced that the slow-speed rebound damping was inadequate. Maybe not dangerously inadequate, but certainly very noticeably inadequate. Since the bleed holes dominate the characteristics of the slow-speed damping, going to an even slower shim-stack configuration would *not* fix the problem (as the shim stacks affect mostly the high-speed damping characteristics). One solution would be to fill-in the bleed holes and redrill them at a smaller bore. A simpler solution would be to increase the oil viscosity. This has the drawback of also affecting the high-speed (shim-stack based) circuits, but shim-stack based damping is (I believe) generally LESS sensitive to oil-viscosity changes than fixed-orifice based damping. With these in mind, I replaced the oil with an Ohlins Fork Oil #5 (cSt @ 40 = 23, while AMSOIL #5 I was using had cSt @ 40 = 15.7). The fork was, almost magically, transformed. It is now VERY close to how I like it. I can't tell how much the high-speed damping was affected, but certainly there were no dramatic changes.

I checked and rechecked everything and I'm pretty sure we didn't do anything wrong with the Gold Valves installation. I'm a bit perplexed about how could ANYONE like a rebound damping so fast as with the 15.7 cSt oil!

[npat]

I forgot: I also increased the oil level to 110mm (from 120mm) to increase bottoming resistance at (VERY) hard braking.

Next step: For now I will leave the fork as is. When the time comes to change oil, I will: Put a good quality 26 - 28 cSt shock oil (high VI) and go to one-faster rebound stack (r20 --> r19), and maybe one-softer compression stack (c35 --> c34) to compensate the high-speed circuits for the viscosity change.

[npat]

After riding some more I got convinced that the slow-speed rebound damping was inadequate. Maybe not dangerously inadequate, but certainly very noticeably inadequate. ...

The last day or so, I 've been scratching my head trying to figure out WHY ON EARTH the low speed rebound was so fast when I followed RT suggestions regarding bleed hole diameter and oil weight. Only two things seem possible:

1. I drilled biger holes, by mistake.

2. The cartridge has SOME OTHER BLEED orifice which I had to block (and I didn't).

Other than this, the only possibility is that RT's suggestion regarding bleed-hole size is nonesence.

Does anyone know anything about this? Is there another bleed method in the VFR showa cartridges? Any suggestions would be very helpful!

[Baileyrock]

After riding some more I got convinced that the slow-speed rebound damping was inadequate. Maybe not dangerously inadequate, but certainly very noticeably inadequate. ...

The last day or so, I 've been scratching my head trying to figure out WHY ON EARTH the low speed rebound was so fast when I followed RT suggestions regarding bleed hole diameter and oil weight. Only two things seem possible:

1. I drilled biger holes, by mistake.

2. The cartridge has SOME OTHER BLEED orifice which I had to block (and I didn't).

Other than this, the only possibility is that RT's suggestion regarding bleed-hole size is nonesence.

Does anyone know anything about this? Is there another bleed method in the VFR showa cartridges? Any suggestions would be very helpful!

That 1.3 mm bleed seems fairly standard for VFR forks if I remember correctly. Also seem to remember bleed holes in the cartridge tubes or an I thinking of F4i cartridges?

BR

ps I have both apart at the house if you want to PM me tonight, I'll check them out for you.

[npat]

That 1.3 mm bleed seems fairly standard for VFR forks if I remember correctly. Also seem to remember bleed holes in the cartridge tubes or an I thinking of F4i cartridges?

BR

ps I have both apart at the house if you want to PM me tonight, I'll check them out for you.

YES PLEASE! If you have them disassembled, please do check them. It will be VERY helpfull. Observe carefully for bleed holes for REBOUND and compression (though I'm pretty certain that stock compression bleeds through a bleed-shim).

You will save me having to dismount and disassemble my forks for a third or fourth time!

[npat]

After riding some more I got convinced that the slow-speed rebound damping was inadequate. Maybe not dangerously inadequate, but certainly very noticeably inadequate. ...

The last day or so, I 've been scratching my head trying to figure out WHY ON EARTH the low speed rebound was so fast when I followed RT suggestions regarding bleed hole diameter and oil weight. Only two things seem possible:

1. I drilled biger holes, by mistake.

2. The cartridge has SOME OTHER BLEED orifice which I had to block (and I didn't).

With the help of Baileyrock (who happened to have a VFR fork already disassembled) we managed to diagnose the problem:

As it turns out, there ARE, after all, bleed holes on the showa valve holders. There's a 1.0mm bleed hole on the compression holder, and a 1.2mm bleed hole on the rebound holder. If you follow RaceTech's suggestions, and drill 1.3mm bleed holes on the valve bodies, then you MUST block the bleeds on the holders. Neglect to do so and you will end up with VERY FAST reboung and VERY SOFT compression (toying with the shim stacks WON'T FIX these).

Alternatively you could avoid drilling the RaceTech valve bodies altogether, and instead re-bore both bleed holes on the holders to 1.3mm diamemter. If you have not already drilled your Gold Valves this is probably preferable as it is much easier to drill the holders than the valves themselves.

Here are pictures of the stock bleed holes on the valve holders. You can either block them (I silver-brazed them) and drill the valves, or use them (after boring them to the propper diameter) instead of drilling on the valves:

On the compression valve holder:

On the rebound valve holder:

Here's how the rebound valve holder looks after brazing the hole:

And here's how the valves look fully assembled:

Many thanks to BaileyRock who helped a lot in diagnosing this issue.

[npat]

Generally, if you are installing RT Gold Valves in a non-adjustable fork, then try to figure out how the stock configuration achieves some shim-stack bypass flow for low-speed damping. You must make sure that you have eliminated this flow-path before installing gold valves with bleed holes drilled on them. Otherwise you risk getting too weak low-speed damping (fast rebound, soft compression).

[Baileyrock]

Many thanks to BaileyRock who helped a lot in diagnosing this issue.

Hey thanks! I don't know much, but happy to share what little I pretend to know!

Thanks for posting this us as it should help many members doing their own RT fork mods.

BR

[npat]

It seems that rebound damping circuits have something personal against me. I can't explain it otherwise.

Once I sorted the front, I started fiddling with the rear. (I remind you: Brand new Ohlins HO605).

I try to increase rebound damping, no noticable difference. Try to increase it even more, nothing again. Try more still, nothing once more.

I remove the shock and take it back to the ohlins dealer. They do some stuff to it (they say they changed fluids and gasses and I don't know what else) and say they've sorted it out. I put it back on the bike, and try to adjust rebound. There is noticeable difference if I increase or descrease the setting on the adjuster,

BUT: With the adjuster at 6 clicks from fully closed the rebound damping IS NOT TERRIBLY STIFF. Is this reasonable? I was expecting that a 6 clicks from maximum it should feed rock-hard.

At how many clicks (from max) do you usually run the rebound adjuster on your Ohlins suspender?

[Baileyrock]

I don't think it matters what setting number works as long as you can find one that does!

If you have to max out settings in any direction then that indicates that the internal valving needs to be redone.

Just go full stiff on rebound and if the shock doesn't almost stop rebound movement then you have an issue.

I suggest you focus on rebound adjustments first, then work compression setting.

A word of caution with rebound adjustments, especially on the rear! Too much rebound can/will cause many negative effects on all aspects of handling from rear packing, poor turn-in, poor braking, etc.,etc. I found that being on the too little rebound side much more desirable than the too much side.

BR