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2015 YZ250 Forks on Stiff side

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Long story short.....bike when new had 44kg springs. They dived too much and were mushy for my liking. I had a Dave Johnson kit installed in it with 45kg springs. Much better but still on the soft side for my liking.

Now I went to 47kg springs springs and I believe they are to stiff. They feel great on jump landings and through breaking bumps bit it rides to high up front.

Bikes hard to settle in a turn up front.

 

I have the Compression clickers all out and Forks are 10mm up in the clamps to help with turning and outer Tube fluid level is 320cc of fluid. Valving feels good so the valving is ok.

 

Should I just get some 46kg springs?

 

Now with the 47kg springs in it,I love the way it feels off jumps when landing and also through breaking bumps,whoops,small chop ect.... it's just through the turns now.

Just need a some of my compression clickers back now to get the front down some.

 

Any ideas?

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Have you measured spring preload during any of those experiments ?

(in stock form my YZ125 was in the 8-9mm range, later reduce to 4mm it greatly helped a front tire washout issue)

 

By 'all out' on the COMP clicker, I'm guessing you mean full soft ?

Edited by mlatour

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Have you measured spring preload during any of those experiments ?
(in stock form my YZ125 was in the 8-9mm range, later reduce to 4mm it greatly helped a front tire washout issue)
 
By 'all out' on the COMP clicker, I'm guessing you mean full soft ?

Yep! Full soft. How exactly do you measure the Forks spring preload?
I do all my own work on Forks/Shock + charge the Nitrogen tank.

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No doubt there are YouTube videos but here's how I do it.

 

With the fork mounted in a bench vise by the axle lug (use aluminium soft jaws)

 

-fully assembled, measure the total length from the top to the bottom of the lower tube (where it enters the lug) 

 

-with the rebound adjuster / clicker removed and rebound rod disconnected, measure again

(oil drained from fork, rod disconnected so fork extends more)

A trick is to slightly wipe the tube / dust seal with fork oil to reduce stiction and then slowly

lower the upper fork tube assy until the internals sit on the spring, do it a few times to confirm your method is repetitive.

 

Can't remember my exact numbers be say as an example:

-fully assembled: 680mm

-rebound rod disconnected, tube just sitting on the spring: 684mm

equals 4mm of spring preload

Edited by mlatour

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No doubt there are YouTube videos but here's how I do it.
 
With the fork mounted in a bench vise by the axle lug (use aluminium soft jaws)
 
-fully assembled, measure the total length from the top to the bottom of the lower tube (where it enters the lug) 
 
-with the rebound adjuster / clicker removed and rebound rod disconnected, measure again
(oil drained from fork, rod disconnected so fork extends more)
A trick is to slightly wipe the tube / dust seal with fork oil to reduce stiction and then slowly
lower the upper fork tube assy until the internals sit on the spring, do it a few times to confirm your method is repetitive.
 
Can't remember my exact numbers be say as an example:
-fully assembled: 680mm
-rebound rod disconnected, tube just sitting on the spring: 684mm
equals 4mm of spring preload

I will do that when riding slows down a bit. I just want to get the Forks right by February when early riding season starts back.
But is it really necessary to drain the oil if the fork is upside down clamped by a vise by the lug? To me .......the oil should be fine In the tube. Unless the oil makes the spring want to float up bit the weight of the spring should be heavy enough to stay planted at the bottom(Top,since it's upside down in a vice).

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The method I described is with the tube right side up, clamped by the axle lug in a vise.

I've always measured it without oil as I add/remove spacers to obtain the desired preload.

Edited by mlatour

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You should not tune stiffness with springs , what do you weigh ?

 

 

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You should not tune stiffness with springs , what do you weigh ?
 
 

166 lbs in Birthday suit. I know you will say the 47kg springs are to stiff,but I like everything about how it rides and feels on a MX track.
Only thing is......I would like to just have about 4 or 5 more clicks softer on compression.

Now Dave J. Built me a kit on my 16 YZ450 using my stock springs 50kg and made the valving to where it is set in the middle. Before the kit with the 50kg springs I had the clickers all out just like on my 250 smoker right now.

My 250 feels good but the Forks don't settle in too good through a turn. If I just had about 3 clicks softer it would be just right.
Maybe if I slowed the rebound a tad it may help. The Rebound clickers is set at 16 out and I leave them here all the time.
But say if I turn em in 3 clicks to say 13 clicks out, the rebound doesn't want to follow the ground good.
Feels as if they are packing. I like a faster rebound feel so that the Forks recover.

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They are packing because your comp damping is too soft. The issues you are describing seem related to damping settings. You should get the proper springs for your weight and work on the valving to solve the issues you are having. 

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3 hours ago, CaptainKnobby said:


166 lbs in Birthday suit. I know you will say the 47kg springs are to stiff,but I like everything about how it rides and feels on a MX track.
Only thing is......I would like to just have about 4 or 5 more clicks softer on compression.

Now Dave J. Built me a kit on my 16 YZ450 using my stock springs 50kg and made the valving to where it is set in the middle. Before the kit with the 50kg springs I had the clickers all out just like on my 250 smoker right now.

My 250 feels good but the Forks don't settle in too good through a turn. If I just had about 3 clicks softer it would be just right.
Maybe if I slowed the rebound a tad it may help. The Rebound clickers is set at 16 out and I leave them here all the time.
But say if I turn em in 3 clicks to say 13 clicks out, the rebound doesn't want to follow the ground good.
Feels as if they are packing. I like a faster rebound feel so that the Forks recover.

You got it, slow ur rebound should do the trick. 

164 in a bday suit, I use .48 works great 

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Exactly

But why does the Forks feel mushy and soft with correct spring rate?
The bike with correct springs was valved stiff but they still felt soft.
However they did feel harsh on the small stuff like chop and they slapped hard when landing from big jumps.
With these stiffer springs they feel much better.
Even through turns they are Not that bad. I would just like to have back some clickers on my compression. Just maybe 4 clicks softer is all.

Surly they is something you could do to gain back just a few clicks aren't they?

Other than get softer springs.

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You got it, slow ur rebound should do the trick. 
164 in a bday suit, I use .48 works great 

I went in just one click on Rebound today at track. It might have helped just a tad in the turns. Should have tried o e more click to 14 out on Rebound and seen how that would have done.

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2 hours ago, CaptainKnobby said:


I went in just one click on Rebound today at track. It might have helped just a tad in the turns. Should have tried o e more click to 14 out on Rebound and seen how that would have done.

Dont be afraid to add compression. Maybe 2-3 slower rebound and 2 clicks stiffer comp at the same time. 

Side note, do your forks ever bottom?

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You don't seem to get the role of springs , soft spring are not soft if they are correct for your weight, springs hold the bike at the correct height and set the chassis level , if the bike is diving too much the damping needs to be adjusted , the midvalve has a huge effect on dive , also to some degree so does spring seats ( more to do with midstroke but you can feel in in breaking ) also preload on the Spring's. You can go up one rate than the recommended but you should not be using spring's to alter the front as it will be out of balance with the back .

So I would suggest go up one rate from recommended and tune with the midvalve to get the stiffness right

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Dont be afraid to add compression. Maybe 2-3 slower rebound and 2 clicks stiffer comp at the same time. 
Side note, do your forks ever bottom?

No they don't bottom normally. However today on this one jump, it's a pretty good size double. You come out of a sweeping left hand turn and I am I. 2nd gear, hitting the face of thus jump I. 2nd gear wide open. Sometimes if you don't stay all in the throttle going up the face, you will land a hair short.
I did and the Forks bottomed.

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12 hours ago, CaptainKnobby said:


But why does the Forks feel mushy and soft with correct spring rate?
The bike with correct springs was valved stiff but they still felt soft.
However they did feel harsh on the small stuff like chop and they slapped hard when landing from big jumps.
With these stiffer springs they feel much better.
Even through turns they are Not that bad. I would just like to have back some clickers on my compression. Just maybe 4 clicks softer is all.

Surly they is something you could do to gain back just a few clicks aren't they?

Other than get softer springs.

You complain about them being too soft and mushy, yet you're trying to find a way to make them softer...

I still think you would make them feel softer if you went harder on comp damping. And get the right springs for your weight, with proper preload.

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6 hours ago, CaptainKnobby said:


No they don't bottom normally. However today on this one jump, it's a pretty good size double. You come out of a sweeping left hand turn and I am I. 2nd gear, hitting the face of thus jump I. 2nd gear wide open. Sometimes if you don't stay all in the throttle going up the face, you will land a hair short.
I did and the Forks bottomed.

If you are not bottoming all the time, however still bottoming occasionally, that for the most part rules out fork oil level. 

I would try a few clicks slower rebound, and a few clicks stiffer LS comp to compensate.

You could however try lowering the front end 5-10 mms as well (raising the forks in the clamps, or adding preload to the rear shock) as an alternative adjustment. 

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You complain about them being too soft and mushy, yet you're trying to find a way to make them softer...
I still think you would make them feel softer if you went harder on comp damping. And get the right springs for your weight, with proper preload.

Working on it with Dave J!

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