Jump to content

3rd gen fork setup


RhodeMoto

Recommended Posts

  • Member Contributer

- According to my (rough) estimates for my 6G, sprung weight up front is about 75-80 kg and the rider in normal riding position puts no more than a third of his bodyweight on the front wheel. 

 

I arrived at this by calculation based on my sag values, the known spring rate and the known preload. It's 100% guaranteed inaccurate (sag measurements taken alone are not very accurate) but it should not be waaay off either and better than nothing even for a 3G.

 

- You have a tapered stack in there where you counted the smaller OD .10 shims as 1, hence my remark. OTOH, I have no clue how much they contribute to overall stiffness so 1 might be better than nothing after all.

 

- Yes. Even if ShimRestackor works as advertised, it won't tell you what will work exactly as you'd wish.

 

Honestly, I'd just put in the RT rebound stack and see how that goes. You just might like it enough to forego any further fiddling. 

 

Nobody likes to mess with fork internals. I need to do my rebound stacks and find myself procrastinating big time. :laugh:

Link to comment
Share on other sites

  • Replies 136
  • Created
  • Last Reply


Clearly one can get lost for far to long in this,.....

I did make the acquaintance of the head mechanic at the best and oldest dealer in Rhode Island. 

Left with a handful of shims! Just "return what you don't use".

Should be able to create the RT stack.

Do have to take the cartridge part again, but better than a complete tear down.

They were closing so did not a chance to see what they carried for oil.

Getting closer.

Link to comment
Share on other sites

  • Member Contributer
18 minutes ago, RhodeMoto said:

Getting closer.

 

:fing02:

 

Good deal on the shims. It's not that they cost so much per piece but I haven't found yet any place that sells useful assortments rather than packs of 10 (or 50) of one size. :491:

Link to comment
Share on other sites

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.

20161113_091518.jpg

Link to comment
Share on other sites

  • Member Contributer

Very nice chart. 

I'm using the stock .70kg springs. Wish somebody made a strait rate .75 for us lightweights.

You can also affect the 'hardness' or 'softness' of the stack based on the diameter of the clamp shim. (one of the things I'll try in the future-I only change one-at most two things a a time-to easy to get lost) Gives the shims a bit more room to flex, which is probably more of a consideration for the street than track. 

Link to comment
Share on other sites

  • Member Contributer
54 minutes ago, rangemaster said:

I'm using the stock .70kg springs. Wish somebody made a strait rate .75 for us lightweights.

 

Are you sure you want to stick with springs that light ?

 

The RT calculator has your 135 lbs at 0.868 kg/mm. 

 

Considering that the bike on its own puts upwards of 150 lbs on the front springs and that the rider puts about 33% of his own weight on the front, we get:

 

150 + (135 / 3) = 195 lbs

150 + (210 / 3) = 220 lbs 

 

=> Spring rate difference: 220 / 195 = 13 %

 

I'm pretty sure that you can use 0.80 or 0.85 with no problem at all. 

Link to comment
Share on other sites

I am just making this up as I go,... I made up a reduction factor for the flex of the smaller dia. shims. Know this has no basis on reality, but thought it would still give some visual as to how different shims add up. I also have to work with what shims I have gathered. Will have to check the shim clamp dia. that I have - it seems most are 8mm? 

 

My proposed version is virtually matching R/T - Rh17, but with a tapered set. I know the discussion was that it did not matter for rebound,but,... I was reading the RT "bible" (mistake?) and there is reference to shim fatigue with all same dia.? The other thing mentioned is that there is some increase in oil pressure as the rebound stroke gets longer. R/T old school seems to have gone with same dia. - the "new" rebound list is all tapered.

My thinking is the 17mm stack will react first so if I zero the smaller ones out of the equation I get a force/lb factor of .123 (just about where rangemaster is). So starts compliant, then builds as each larger shim comes into play until it reaches full at .130/lb near Rh17 value.

So - time to sh_ _ or get off the pot.

Going to the basement and get to work!

Hopefully my next post will be with results.

 

 

Link to comment
Share on other sites

  • Member Contributer

Good on you Rhode. Let us know how you get on. 

 

I should warn you if I did not before...tinkering with suspension is also a recipe for disappointment. There is always the feeling that "it could be better if I just...". When you leave it stock, you can just say "well, that is how it is". Having said that, all three of my current bikes have "benefited" from my suspension tinkering!

 

Keep notes, and try to keep any testing as consistent/comparable as you can. I've tended to start with the RT recommended set-up of springs and shims, and then vary one element at a time (if my patience was up to it). I've spent the most time on my VFR and specifically on the compression stack, as I seem to have a bit of a deaf ear when it comes to monitoring rebound changes. I guess I sense the effects of the leading edge of bumps and dips, but care less about a few weaves afterwards.

 

YMMV

 

Link to comment
Share on other sites

  • Member Contributer
4 hours ago, RC36Rider said:

 

Are you sure you want to stick with springs that light ?

 

The RT calculator has your 135 lbs at 0.868 kg/mm. 

 

Considering that the bike on its own puts upwards of 150 lbs on the front springs and that the rider puts about 33% of his own weight on the front, we get:

 

150 + (135 / 3) = 195 lbs

150 + (210 / 3) = 220 lbs 

 

=> Spring rate difference: 220 / 195 = 13 %

 

I'm pretty sure that you can use 0.80 or 0.85 with no problem at all. 

 

A LOT of the stuff I've read says the Race Tech stuff is exactly that-geared for the track, so a bit stiff for a given weight for the street. That being said, I'm also dealing with New Mexico roads, NOT the most bike friendly I've been on. I'm more a sport TOURER than a SPORT tourer, being a old guy and all. But should I find a deal on some .80's, I would love to try your suggestion. With what stuff I've done it's still a bit harsh on the little stuff, but about perfect (for me) on the bigger stuff. 

Link to comment
Share on other sites

  • Member Contributer
2 hours ago, rangemaster said:

 

A LOT of the stuff I've read says the Race Tech stuff is exactly that-geared for the track,

 

RT's setups do have that reputation but what is frequently not appreciated IMO is that the spring rate does not have such a dramatic effect on suspension hardness over bumpy stuff.

 

I messed up a bit in my post above. I forgot to say that the 210 lbs rider is me and that I ran 0.90 RT springs in my 4G (way back in 2003). RT recommenced 1.0 but I was like you and let myself be convinced that it would be race hard so went with 0.90.

 

Result: Heavier springs (within reason) make the ride tauter but not harsh.

 

Harshness is mostly a function of damping, I believe. For the VFR (and most Japanese bikes), the road to firm and controlled yet plush is heavier springs, mild compression damping and adequate rebound.

 

Long story short, I think you can try 0.80 without any fear of turning the forks into a bone shaking, teeth rattling affair.

 

As a starting point, just make sure you have your preload / sag right and don't even touch your current valving.

 

Oh, and get your springs from DMr or some other place that sells Sonic's. RT is overpriced. 

Link to comment
Share on other sites

  • Member Contributer

One more thing. 

 

I'd wager New Mexico roads have nothing on Belgian roads when it comes to crappy tarmac. 

 

Pretty much anything that's a bit fun to ride comes at the price of a grotty surface over here so I am certainly not looking for a setup that is only fit for smooth stuff. 

Link to comment
Share on other sites

New delema,..

All clean, shims sorted, ready to assemble.

The new tubes have a wall thickness of 3mm. This leaves an ID of 35mm. The OEM is 2.5 wall, ID 36mm.

The race tech Springs are 35mm.

I can push the spring in, but it is not a drop fit. Seems this would bind and or wear the inside of tube.

Ideas?

Does anyone need some 1kg springs? I could probibly drop to .9 or .95 if someone wants to swap. Need spring to be 34mm dia.

Link to comment
Share on other sites

  • Member Contributer
6 hours ago, RhodeMoto said:

The new tubes have a wall thickness of 3mm. This leaves an ID of 35mm. The OEM is 2.5 wall, ID 36mm

 

Oh, bummer ! :huh:

 

I use the 35 mm OD RT springs in my 6G's 43 mm forks with no problems but I would not use a spring that is a tight fit.

 

All coil springs need some clearance as they widen a bit under compression.

 

Fork springs being long and slender also have a tendency to buckle so they need that little bit extra. 

 

No way around getting new springs there, I'm afraid. :unsure:

Link to comment
Share on other sites

  • Member Contributer

Once bought, them springs do not eat any bread, so store them..

New ones do cost bread...

 

c'est la vie....

 

Link to comment
Share on other sites

  • Member Contributer
20 hours ago, RhodeMoto said:

Does anyone need some 1kg springs?

 

I could use them but I checked the shipping rates to Europe and that would only leave you with some pocket change for your trouble. :huh: 

Link to comment
Share on other sites

  • Member Contributer

If you can't return the Racetech springs for a more suitable size, I'd suggest you go to Sonic Springs as they manufacture and supply to others, so I suspect they will be able to provide exactly what you need.

Link to comment
Share on other sites

Story form Sonic;

Ours are 35mm (nominal) also, actual is in the 34.8-34.9 range. There is a
bit of variance. You do need a little room, but you don't need much. I'd
try them and see, if they just drop in you're fine, if there's any
interference or binding at all then you need smaller OD springs. The next
size down that I have is a 32mm OD spring, we use those in some 41mm forks
that have thicker tubes, like the original Kawasaki Concours and the
Yamaha FJ1100.
The 1.0 is a bit on the stiff side for you, but ok if you're a fairly
aggressive rider. If not, then 0.95 would be better. 0.05 is a small
difference, hard to feel.

 

Race Tech is same from tech guy. Next size down is 32mm. They suggest light surfacing of the circumference to allow spring to drop in tube.

I was considering this, but talked myself out. Now I am thinking - What have I got to loose? I only need a few thousandths. It may "weaken" the spring rate but that may be OK. It will not cause the spring to fail. 

Now I have to figure out some way to run a tube or rod though it and turn to try to get as even as possible.

I am sure I have done dumber things in the past and gotten away with it.

Link to comment
Share on other sites

On 11/14/2016 at 5:37 PM, RC36Rider said:

 

Harshness is mostly a function of damping, I believe. For the VFR (and most Japanese bikes), the road to firm and controlled yet plush is heavier springs, mild compression damping and adequate rebound.

 

 

And friction: excess static friction will have very much the same feeling as overly stiff compression damping.

 

I agree 100% with your comments regarding spring rate. Though it may seem counter-intuitive the key to a firm yet plush ride is heavier springs with less installed preload (I aim for around 10 mm). They are also the key to the most desirable handling. Heavier springs with less preload will:

 

  1. give more linear dive on the brakes (esp. when combined with good comp. damping)
  2. increase bottoming resistance, and make tuning the total fork travel with oil height much easier.
  3. cause the front end to stand up less if the front brake is applied in the corner, making changes to speed and line easier
  4. cause the front end to extend less on acceleration, making the bike less inclined to run wide on corner exit
  5. give much better feedback about road surface, grip levels etc.

 

Link to comment
Share on other sites

I hope to acheived all 5 points as listed above,....

I was trying to come up with an accurate method to size springs, and then went with use what you got. Slipped spring on dowel rod clamped to bench. While spinning spring, ground surface with 80 grit right angle grinder. Light touch, and watched the flat that was created. Found it was not that difficult to keep even, and checked fit. When I had 3mm flat it seemed good. Switch pad to a red 3M scotch pad to smooth and ease edges.  Went straight to buff wheel and polished.

I measure that I took .25mm off, net .5 clearance. I changed the spring in that measurement by 7%. Can we assume that the spring is now 7% lighter rate? 

Have one assembled. Will do a spring rate check and see if there is measurable change.

If no new setbacks and find some oil, may be rolling this weekend.

20161118_195718.jpg

Link to comment
Share on other sites

  • Member Contributer
21 minutes ago, veeferbkk said:

And friction: excess static friction will have very much the same feeling as overly stiff compression damping.

 

True that. To quote the Race Tech Bible: "Friction: Bad !" :laugh:

 

I haven't bothered with friction beyond checking that my stiction (as measured by static sag difference between the forks compressing and extending) was within an acceptable range. Meaningfully improving this is something I consider beyond my modest DIY technical and/or financial means.

 

By the same token, I don't mention reducing unsprung mass because I can't afford carbon or forged wheels. 

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.


×
×
  • Create New...

Important Information

By using this site, you agree to our Privacy Policy.