Jump to content
herrmann450r

My take on the KYB RE forks

Recommended Posts

22 minutes ago, MartyMOOSE said:

Oh we are so different not my cup of tea my son races a lightly tuned WR250f not my idea of fun. Its a 15 though but I image the engine would be close. His pulls way better than the 19 we have ridden. They respond really well to a 14.2:1 piston or if you like doing rebuilds a 14.5:1 the later option gets about 90 hrs out of a rod in our case. 

MM 

Here, less is more.  This bike will be good as is my 250RR.  No need for big motor mods.  Suspension is way more important.  

  • Like 2

Share this post


Link to post
Share on other sites
8 hours ago, GP said:

What springs are these coming with?

 

4 strokes 4.7N, 2 strokes 4.4 N (125 4N).

Share this post


Link to post
Share on other sites

Well I can't say too much for sure because I'm not familiar with the new chassis, but that still looks a bit light to me.  Plus, why are the 2stroke 250/300 target rider weights for stock springs different for F&R in that chart?  With the rear raised 15mm on the old chassis, which properly balanced it, its probably closer to the taller new bike than a stock old bike.  The bike works great a bit on the stiff side.  For example I run .46s up front and a 5.8 (that Steve measured as close to 5.9) out back.  At 185lbs that sounds really stiff but its perfect for me.   If you rode the bike you would never believe the rate numbers.  Stiff springs, minimal preload.  When you try to valve around soft springs things go to crap.

I'm done.  Anyone have any intel on the new KYB fork before I can get to mine please ping me.  Also need Restakor data(dimensions) for 50mm KYB shock piston.  Thanks.

Share this post


Link to post
Share on other sites
2 hours ago, SigPig said:

2020springrates.png.de6ac87dbb0a9bcd0843838c4ba7efde.png

When you convert from one unit to another, you need to know basic formulas.

So when you have force (N) and you need to express this in kilograms the (1st grade-level) formula is f=m*g (where g is the acceleration of gravity equal to 9.81 m/sec^2)

Hence to convert from Newtons/mm to Kg/mm the formula is m=f/g .

Therefore the 4 stroke standard fork springs in kg/mm are m= *4.7 / 9.81= 0.4791 = 0.48 kg/mm

*4.7 N/mm is the specification published on the manufacturer's site, therefore I take this as the correct one.

 

Edited by dirtbird

Share this post


Link to post
Share on other sites
On 2/18/2020 at 12:25 PM, MartyMOOSE said:

It's pretty easy dirt bird. Fit the spring perch to the cartridge fit the Springs into the fork put the cartridge in loose. Fully compressed the outer tube measure from the top of the outer tube to a point on the top cap. Then fit The Rebound adjuster to the bottom of the cartridge rod, screw it into the fork lug and remeasure that's your preload. As far as adjusting goes I machine the top edge off the spring perch. IMG_20190713_090855_01.jpg

Std preload measured, 4mm (ok and some tenths...).

  • Like 1

Share this post


Link to post
Share on other sites
9 hours ago, dirtbird said:

Std preload measured, 4mm (ok and some tenths...).

My forks are a bit of a mismatch of Yamaha and Honda parts :) Preload was 10mm dropped them to 6mm. These TC Kyb forks vary a bit inside with top out springs cartridge length ect etc. 

Share this post


Link to post
Share on other sites

Hi 

2020 RE KBS. 
What outer chamber oil quantity is stock and what have you guys found works best ? I would  like to just soften the forks a bit so I’m looking to drop a spring rate down to 4.2 and with Steve’s recommendation a little less oil.  I weigh 85kg 

Share this post


Link to post
Share on other sites
6 hours ago, Burger72 said:

Hi 

2020 RE KBS. 
What outer chamber oil quantity is stock and what have you guys found works best ? I would  like to just soften the forks a bit so I’m looking to drop a spring rate down to 4.2 and with Steve’s recommendation a little less oil.  I weigh 85kg 

That doesn't sound right at 188 lbs; is that riding weight or is that in your skivvies?

 

Share this post


Link to post
Share on other sites
7 minutes ago, mtdirtbag said:

That doesn't sound right at 188 lbs; is that riding weight or is that in your skivvies?

 

Steve had me keep the stock springs at 210 lbs. Usually I've always run a rate higher than called for but for whatever reason Steve seems to be recommending slightly lighter than normal.  

I've put cable ties around the lowers and it appears he is correct. Also fork sag is acceptable. It might have something to do with the relatively stiff ICS springs. 

  • Like 2

Share this post


Link to post
Share on other sites

I am between springs rates, at the top end of 4.2’s and bottom of 4.4’s I’ve usually gone with 4.2 as I like a slightly softer feels and with the KYB’s being on the stiffer side, Was recommended to go with the 4.2 and a slightly lesser oil volume 

Share this post


Link to post
Share on other sites
2 hours ago, Burger72 said:

I am between springs rates, at the top end of 4.2’s and bottom of 4.4’s I’ve usually gone with 4.2 as I like a slightly softer feels and with the KYB’s being on the stiffer side, Was recommended to go with the 4.2 and a slightly lesser oil volume 

One of each for a 4.3

Share this post


Link to post
Share on other sites

Maybe I am crazy but can people really feel a .1 kg/mm difference?  I see posts about people arguing over 3mm preload on a spring, that is less then a 1/8 inch on a fork with 12 inches of travel.  Maybe I am just cranky today, dirt biking isn't rocket science get it close and ride, there are way to many variables out in the real world to worry about  .1's or 1mm in 12 inches... 

  • Like 1

Share this post


Link to post
Share on other sites
1 minute ago, rharr said:

Maybe I am crazy but can people really feel a .1 kg/mm difference?  I see posts about people arguing over 3mm preload on a spring, that is less then a 1/8 inch on a fork with 12 inches of travel.  Maybe I am just cranky today, dirt biking isn't rocket science get it close and ride, there are way to many variables out in the real world to worry about  .1's or 1mm in 12 inches... 

Jeez, don't get them started, it's almost as bad as jetting threads. lol

  • Like 1

Share this post


Link to post
Share on other sites
Posted (edited)
42 minutes ago, rharr said:

Maybe I am crazy but can people really feel a .1 kg/mm difference?  I see posts about people arguing over 3mm preload on a spring, that is less then a 1/8 inch on a fork with 12 inches of travel.  Maybe I am just cranky today, dirt biking isn't rocket science get it close and ride, there are way to many variables out in the real world to worry about  .1's or 1mm in 12 inches... 

I agree !!

To me changing the fork springs to make half a spring rate isn’t something I would feel but going down one proper rate and also dropping the oil level is noticeable and I would certainly take advice from @motoxgiant 👍

Edited by Burger72
  • Helpful 1

Share this post


Link to post
Share on other sites

Beta forks have traditionally been fitted with 0.42 kg/mm fork springs, but the last set of KYB springs I measured were 0.45 kg/mm.

In MY2020 the bikes are lighter and the valving stiffer - reasoned judgment is that the bikes are oversprung relative to the MY2019s and prior, for a given rider weight. Techinique and speed also play into the spring rates we recommend.

  • Like 1

Share this post


Link to post
Share on other sites
Just now, motoxgiant said:

Beta forks have traditionally been fitted with 0.42 kg/mm fork springs, but the last set of KYB springs I measured were 0.45 kg/mm.

In MY2020 the bikes are lighter and the valving stiffer - reasoned judgment is that the bikes are oversprung relative to the MY2019s and prior, for a given rider weight. Techinique and speed also play into the spring rates we recommend.

I believe you're correct. I have yet to bottom the forks. Beta's recommendation was 4.6 for my weight, obviously incorrect.

Share this post


Link to post
Share on other sites
Just now, motoxgiant said:

Beta forks have traditionally been fitted with 0.42 kg/mm fork springs, but the last set of KYB springs I measured were 0.45 kg/mm.

In MY2020 the bikes are lighter and the valving stiffer - reasoned judgment is that the bikes are oversprung relative to the MY2019s and prior, for a given rider weight. Techinique and speed also play into the spring rates we recommend.

Thanks Steve as always, what oil quantity Would you recommend going to on these for a softer  set up in conjunction with the 4.2 springs for a good mix of slow and technical and single track ? 

 

Share this post


Link to post
Share on other sites
52 minutes ago, Burger72 said:

Thanks Steve as always, what oil quantity Would you recommend going to on these for a softer  set up in conjunction with the 4.2 springs for a good mix of slow and technical and single track ? 

 

We have been stepping down oil quantity to 315ml at present. All of the forks we do go out with an o-ring on the non-disk leg to keep track of travel used (being mindful that full stroke does not wipe the entire chrome leg).

Share this post


Link to post
Share on other sites
Just now, motoxgiant said:

We have been stepping down oil quantity to 315ml at present. All of the forks we do go out with an o-ring on the non-disk leg to keep track of travel used (being mindful that full stroke does not wipe the entire chrome leg).

Legend thanks again,  as always spot on 👍 at 88kg with out boots and helmet I’m on the brink of 4.4’s on the charts but as you’ve pointed out there stiffer so dropping down should make that difference. With the stock RR 2020 forks 4.2’a were a touch soft and I went up to 4.4 but those forks for me didn’t work out at all

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...

×
×
  • Create New...