pushing

[skid jackson]

06 300

my bike seems to have a bit of a push, it will climb berms or blow out of turns. It may be rider induced or perhaps set up induced .. or I guess worse scenerio both ....

what kind of set up factor would cause a push

what kind of rider technique would cause a push

 

[jeffd]

What you describe can be caused by excessive rebound in the forks - forks are rebounding too quickly and rake the bike out as you are in the turn. Crank up the rebound 2 clicks at a time and repeatedly take the same corner and see how she behaves.

It may be time for a fork service/oil change...

jeff

 

[rpduc]

I'm trying to tame the suspension on my '05 MC 250 and definitely can attribute many of my problems to extremely rusty technique, but I've not experienced this "great turning" that GG seems to be noted for either... yet... I've got a ways to go in the set-up department me thinks...

For my own enlightenment, could skid's push not also be caused by soft spring or too much rebound damping in rear, or... stiff springs, too much comp damping in front? Same effect on geometry in a turn no?

I assume you have set your sag and assured proper spring rates.
I saw some interesting info that contradicted what my "common sense" evaluation would tell me about rear spring rate. If you get your rear race sag set up correctly and you measure too much free sag this indicates the spring is too stiff, not the other way around. Conversely if your rear spring is too soft, there will be insufficient free sag when the race sag is set correctly. In either case the spring ends up working in a less than optimal "range." I think I understand the physics, but wouldn't mind a explanation from someone who understands the theory. I imagine the same physics could be applied to the front?

In my case I have too much free (static?) sag and that seems to make sense since there is ( I think) a 56nm spring on there. Too stiff for my 190 lbs.

 

[skid jackson]

What you describe can be caused by excessive rebound in the forks - forks are rebounding too quickly and rake the bike out as you are in the turn. Crank up the rebound 2 clicks at a time and repeatedly take the same corner and see how she behaves.

It may be time for a fork service/oil change...

jeff

running rebound at 2 to 4 clicks past stock setting i.e rebound is slower than stock. just changed fork oil last weekend.
I wonder a bit about my springs ... bike was set up for 200lb rider, I'm down to 180/185. Talked with les and he said he thought the springs in there sgould not be any real issue ...yet. was still thinking of putting a 52 on the rear and 44 up front down from the current 54 and 46

 

[fury1]

that rear trials tire might have something to do with it pushing the front end

 

[GMP]

fury is right, all else being equal, the trials tire will push the front a bit due to the superior traction. Any of the other conditions rpduc mentioned will make it worse as well. I'd get it setup with a knobby so you have a good starting point and then mount the trials so you are sure of the effect. Also, the fork is too light on high speed rebound damping, having it fixed is a nice improvement.

The reason a too stiff spring gives too much static sag with correct race sag is that too little preload is required to acheive that race sag, and visa versa for a too soft spring.

skid,

.46 sounds stiff for a 180 lb. C rider in New England rocks I'm 185lbs and B and get away with .42s but when it gets faster I use the fork up quick so thinking of going to .44s.

Ross,

I think I have an Ohlins 54 on the shelf if you need one.

 

[rpduc]

Hey thanks Glenn,
I think I do need a 54. I'll let you know. I'm a little bit confused by the numbers on my spring though. 12 - 56, L344. What is that "L" number?

I started my own thread a couple days ago with more noobie questions.

 

[GMP]

Not sure, too high a number to be length. Maybe a series number or could be anything, I've had several springs and the #s vary quite a bit. The 5x number is a constant and in your case 56 is indeed a 56 Nm spring. Shocks on the older bikes (pre '03) were a few mm longer but they all use the same springs.

 

[skid jackson]

I double checked my spring stats ....
I'm running a 44 up front. I have the stock 42's in a box ...
I guess I could always toss them in and see what it's like??
I'll ride it as is for a bit longer tho.

I'm going to be swapping over to a knobby for an up coming race maybe ....We'll see If I notice a difference.

 

[widebear]

Make sure that the knobby is not to wide or you will be back to your original problem. I myself never run more than a 120 on the rear. I have found that is the only way that I can really throw the bike around like a bicycle.Crawing out of a rut can allso be caused by a to large rear sprocket i now use a 47 on the rear of my 300 and would on my 250 as well if it had the torque to pull it cleanly.

 

[Skidad]

To me even the .44 springs sound to stiff for New England even at you weight. Try the .42's and see how you like it or you can use 1 .42 and 1 .44 spring for a .43 rate.

Ohlins makes a .53 spring also. Stock on my 97 250 KTM and that bike is almost 250lbs dry. so .54 seems also a bit stiff perhaps for a New England C rider? I weigh 175-180, old A rider and the Ohlins guy said that was the correct spring for me.

I always set static first with less than 10mm of spring preload to JUST to hold the bike up to what I want. Once that is set check the rider sag you want to have. To little sag = spring to stiff, to much sag = spring to soft.

Linkage bikes have about a 20lb rider weight variance for a correct spring where as the KTM PDS bikes have about a 10lb variance. One reason a KTM is such a pain to get correct. You MUST have the correct spring. Let's not even get started on straight rate vs progressive.

Skidad