Linear vs. Progressive

[avlehtine]

I found out stuff for people who have progressive rate springs and might be considering going to linear.

I changed the .43 and 4.8 progressive springs on my -00 YZ250 to .45 and 5.4 linear springs.

I previously had like 15-20 mm. unloaded sag to get about 115 mm. of race sag. Clearly this spring was too soft for me.

The surprise came when the new spring gives me about 110mm. race at 25mm. unloaded.

I would've thought I would have to be nearer to 40mm. unloaded to get anywhere near normal race sag due to the huge difference in spring rates.

Just food for thought.

 

[Jeff Howe]

Hmmmmmm... How's your bike handle now? Worse? Better? Feel better?

 

[Jeff Howe]

Yep, and all valving curves are too.

 

[avlehtine]

I'm talking about straight-rate and variable rate(that is, the amount of force needed to compress the spring a given length varies when you compress it more) springs here. I'm sorry if the finer nuances of the English language sometimes escape me.

The rear end of the bike feels better, even though I think the track has gotten worse (nasty natural whoops). The rear wheel just sticks to the ground much better. I'm still definitely in tuning phase though, the front seem very hard and I got my hands tired pretty fast (possibly from attacking harder, I'm not exactly consistent).

I really have to get the video, I find it helps me tremendously in analyzing my technique and the bike's setup.

 

[Jeff Howe]

Okie, maybe you should clarify that for everyone so they aren't so confused about it. All springs are not progressive.

 

[Jeremy Wilkey]

LOL...This is a fun one.. Okie is right.. Virtually all.. any Jap OEM spring is by matter of design progressive.. Is it an issue no is it "progessive in feel" no is it progressive in rate yes..

Remmber od is a huge impact in spring formula. So a spring with a narower and a wider end is progressive albeit very slighlty.

We have dialoged about this shocknut!

Jer

 

[Jeff Howe]

"Barrel" springs have tapered ends. They do not deflect at the same constant "linear" rate. So "technically" that makes them progressive. Is 3 mm on one end of a spring worth getting technical about to cover a blanket statement? No!

However, ALL springs are not built in barrel configuration. At this point I am unaware of any "barrel" winds being used on stock fork springs. I'm going to say this one last time. ALL springs are not progressive!

 

[Jeremy Wilkey]

Shocknut, I'm not talking barrel springs! I'm talking OEM springs with a wide and narrow end.. They are not barrrel but cone shapped and yeild a progressive rate.. (but only by a matter of techincality) We talked about this not just barrel springs..
Jer

And we are talking shock springs here so your right about the fork springs..However there are some cuurent fork springs that are tappered however.. The DRZ being a progressive fork spring..

 

[MACE]

Hey, pogo-dudes. How about you cast up some "spring rubbers" like them NASCAR hillbillies* use for tuning. I bet you'd sell a bushel basket of $20 rubbers if they did the job of a $90 spring.....


*those hillbillies with 50,000 sq ft shops and $6 million annual bugets that is. Swimmin' pools - movie stars....

 

[Jeff Howe]

Mace,
I have been looking into that. That's one of the things I found in the NASCAR world last spring. I just haven't gotten around to talking with them yet. But the idea sounds cool don't it. I'm just wondering how well they will stay put.

 

[MACE]

In a similar vein, I saw a neat spring adjuster on one of those SODA truck racers you see on espn2 late at night. Basically it was a threaded adjuster which ran on the preload adjuster threads but stuck out between coils in the active portion of the spring - providing a seat for the spring. As you screw it down it reduces the number of active coils. It essentially alters the spring length and therefore rate just by turning the adjuster.

Do you guys have a feel (off hand) for how much additional deflection a spring can take before it coil binds with our typical shock springs? Coil binding would limit how many active coils you could "inactivate".

------------------
MACE

"Prime Directive - Serve the public trust, protect the innocent, uphold the law."

 

[Jeff Howe]

I believe our typical shock springs come pretty close to coil bind as is. sometime if you ever have your spring off clean it up and look at the paint between the coils. That can be an indicator sometimes.

There is another system that has been being used in sleds just recently and off road trucks for years. It uses a 2 spring system that employs a spacer of sorts between the springs and clip or collar on the shock body. The springs will deflect at the combined rate until the spacer comes into contact with the clip or collar on the body then continues to deflect at the single rate of the larger spring. Something like that anyway. I have seen some of the factory sleds using this and I think the Walker Evans snowmobile shocks are using this system. Pretty easy system to build really. You just need to source the springs. This would be a better alternative to progressive wound coils. I think so anyway. More tuneable with the right inventory of"helper" springs for sure.