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3rd gen fork setup


RhodeMoto

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31 minutes ago, RC36Rider said:

Just found some potentially interesting info on...err... another VFR dedicated board: Stock shim stacks 

 

Seems that your rebound stack is actually stock.

 

That was a good find. I'm of a similar mind about the benefit of a Gold Valve (or equivalent) vs the 6-port Showa valves. The flow area will be pretty similar, certainly a mile better than the HMAS valves that Honda used in my VTR1000 and the 5th and 6th gen VFR. Matter of fact, I got some used 6-port Shoma valves from a suspension tuner/ex co-worker, and I used the compression valve in my VTR with great results; for whatever reason, I like the fork action of my VTR the best.

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You do this just to mess with my head?

OK  - So read that other site thread. He seems quite pleased with his setup.

By my math - that (his) rebound is now 45% stiffer than stock/mine?

What I do not know how shim stack add up relative to either spring rate or compression. Does a 45% increase in shim stiffness result in a 45% rebound resistance? 

More importantly, now that I am ready to assemble, should I consider adding shims to rebound?

1 - I am more concerned with getting compression right, and would actually be good with a quick/light rebound.

2 - Am I repeating things,....Did we find that RaceTech rebound confirmed what I had as actually an increase over stock?

 

I had not priced the RedLine yet just seemed like they offered a good product. Overkill?

 

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Redline is great stuff. But to get the weight I wanted in my 4th gen forks, with the stock 6 port valves and a modified shim stack, I went with 2.5 Silkolene. [I only weigh 135 lbs.] The rebound on my 4th gen was WAY underdamped, so a bunch more shims for your 3rd gen doesn't surprise me. I went with 130 mm air gap on the forks and am VERY happy with it-the fork dive is only about 25% of what is was and is very controlled. 

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8 hours ago, RhodeMoto said:

Overkill?

 

For forks, yes but then I'm a pathologically cheap bastard. :laugh:

 

Red Line Lightweight is 16 cSt (perfect) and has the highest VI I've seen at 512 where even premium brands of fork oil rarely exceed 140 or so.

 

OTH, a high VI does not hurt anything and cost is only about 22 bucks for a quart so if that gives you peace of mind about the product's quality, it's money well spent. 

 

RT's "magical" fluid is actually even more expensive and I just don't trust that it's anything special. 

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11 hours ago, RhodeMoto said:

You do this just to mess with my head?

 

No, that's just a side benefit. :goofy:

 

Seriously, I had no idea what the stock stack was and I chanced upon this post. 

 

NB: RT's baseline for reshimming the stock rebound pistons was (6) .15 x17 so quite a bit stiffer than what you have. 

 

Up to you of course.

 

PS: I relish in advance the time when I'll be able to tell you: "I told you so". :goofy:

 

PS2: Please excuse my appalling sense of humour. I just can't seem to restrain myself. :blush:

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A scroogy Belgian.............   never thought I'd come across one.....  :goofy:

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3 hours ago, Dutchy said:

A scroogy Belgian.............   never thought I'd come across one.....  :goofy:

 

F* right off, cheesehead ! :tongue: :wink:

 

Always be friendly with the neighbours. :laugh:

 

PS: To the Moderators: Cheesehead is a term of endearment we Belgians use for our northern neighbours. It's not rude. Not at all. :goofy:

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Why on earth would you want to come to Belgium ? Don't you know it's a hellhole full of Islamic terrorists ? :goofy:

 

I take it you are less than thrilled with your new president. :laugh:

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Duvel beer

Shrimp croquettes

Frietkot

K3

What is not to like?

 

0k, back to suspenders! :-)

 

 

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On 09/11/2016 at 3:30 AM, rangemaster said:

The rebound on my 4th gen was WAY underdamped, so a bunch more shims for your 3rd gen doesn't surprise me.

 

Yes. Back to suspenders. :laugh:

 

Any idea what the shim stack was on your 4G, rangemaster ?

 

Dutchy, did you take your rebound valves apart ?

 

I could have a look inside the stock 4G forks I have but that would involve... you know... work. :unsure:

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I took the rebound apart yes, but didot measure them.

Only recently did I source a micrometer from (sorry Donald...)  China

 

rebound.jpg

 

Sold the lot on so no way of measuring them now.

 

+1 what JZH stated earlier that the rebound valve is considered "OK" overall.

That RT offers these because people want (and will pay for) them?

 

 

 

and here the photographic evidence that yes, it makes sense to clean the internals...

 

i'd bought a set of forks a long time ago with unknown mileage/refresh..

 

sludge.jpg

 

 

after a wee clean

sludge2.jpg

 

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1 hour ago, Dutchy said:

+1 what JZH stated earlier that the rebound valve is considered "OK" overall.

That RT offers these because people want (and will pay for) them?

 

I [used to think the same but I] have changed my mind a little bit about RT's rebound valves. 

 

The stock Showa pistons have the same port geometry on rebound and compression. They are quite similar to RT's comp pistons but rather different from their rebound ones (see pic above). 

 

Ironically, there just might be more benefit in fitting the rebound kit and just re-shimming the stock comp pistons than the other way around. :unsure:

 

Remember, the rebound valve needs to pass roughly 3 times the volume of oil that the comp valve has to pass so they need very large refill ports to leave the oil flow as unimpeded as possible on the compression stroke. 

 

The rebound ports do not need to be that large since the required damping force is about 2-3 times greater than on compression and the velocity range does not go nearly as high.

 

Quite how much difference this makes in the real world, I just don't know. :blush:

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6 hours ago, RC36Rider said:

 

Yes. Back to suspenders. :laugh:

 

Any idea what the shim stack was on your 4G, rangemaster ?

 

Dutchy, did you take your rebound valves apart ?

 

I could have a look inside the stock 4G forks I have but that would involve... you know... work. :unsure:

 

Yes Sir, this is what I found when I opened up my 4th gen forks:

 

Compression stack was  one .15 x 17mm, then two .10 x 17mm and then the rest were the clamp shims etc. 

Rebound stack was two .15 x 17mm, then three .10 x 17mm and then the rest were the clamp shims etc. 

 

BOTH the compression AND rebound valves are the SHOWA big port valves, NOT the small port HMAS valves like on the 5th gen. I have a set of 5th gen fork guts for comparison. 

 

What I have in there now is: 

Compression: five .10 x 17 shims  

Rebound: five .15 x 17mm shims

2.5 wt Silkolene fork oil [cSt 13.6]   (Stock Honda SS-5 is cSt of 15.6)

Air gap of 130 mm

 

Result for me (135 lb rider) is much less brake dive, firm on little stuff, softer hit on big stuff, rebound MUCH more controlled. 

 

Next time they are apart I'm going to try a tapered stack on the compression side ( .10 x 17, .10 x 16, .10 x 15, .10 x 14, .10 x 13) and may be go with the Red Line extra lightweight fluid [cSt 9.8] to get a bit softer hit on the small stuff. But I'm in no hurry because what I have now is a lot better (for me) than stock and, well, "it involves work". 

 Random notes:

The HMAS valves might be worth trying on REBOUND only because that is a function of spring return. But that's for down the road (no pun intended.)

130mm air gap uses exactly 1 quart of suspension fluid.

The 5th gen springs are a bit stiffer than the 4th gen and quite a bit longer. Something else to try later. 

 

Just my 'dos centavos' worth.

 

 

 

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Just wrote up a whole dialog regarding this,.. lost it.

was working on compiling what I could from various suggestions.
vfr shim calculator.pdf

Long story short. Based on this data.

Ideal falls between .08/lb (soft/fast) and .12/lb (hard/slow)

Plan to increase rebound from stock .06/lb to .10/lb +/-

 

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Some more messing with your head ? :goofy:

 

Kidding. Just a few remarks on your calculations. 

 

- Rider weight in isolation is irrelevant.

 

What counts is overall sprung weight and unsprung weight.

 

Of course, since we are talking about VFR's which have not changed drastically across generations in terms of overall weight, weight distribution, wheel weights, etc, rider weight is the main factor but still...

 

- The shim stiffness factor of 3.37 (which is simply relative thicknesses cubed) is a close approximation but only when comparing shims with the same OD (leverage). 

 

- The most important factor in overall stack stiffness is clamp shim diameter as it determines how much leverage oil pressure through the ports works with and is thus a key determinant of how much edge lift you get.

 

This explains IMO why RT's recipes vary only in the number of face / seal shims.

 

Any other type of change and the resulting stack stiffness becomes very difficult to estimate. To the point where you may not even know if you have indeed made it stiffer. 

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Yes! This was a crude late night mess with own head endeavor. 

I was using rider weight as an indicator of or hopefully relative to sprung rate. Assuming anyone messing with shims had to be changing springs as well. 

Just put in what I had found to see if there was some correlation.

This is all regarding rebound so, as discussed earlier, shim diameter is mostly accepted as same for entire stack.

I really do not want to take cartridge apart that is all set for my shiny new tubes, but now that we have discovered rebound is at stock I feel adjustment should be made.

Even if I had shimstackor software, I would still be flying blind without a goal graph to shoot for. 

May be off here as well, but the range from plush to track could be charted, and should have similar characteristics with rider weight, etc. accounted for.

So if someone had software, and time on their hands, they could compile a reverse engineered average of all who have found their way the hard way,...

Then,......I could send my rider data and request a result that was say midway between track and plush, and get results.

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