[SpringheelJack]

Questions abound here. I tried installing new fork springs today and dumping the fluid. The new springs are RaceTech straight rate, I think .95kg. (Got them from Sasquatch when he rebuilt my shock.) The replaced spring is some kind of progressive spring - from the pics it doesn't look stock, at any rate. New fork oil is 10wt, set at 135mm from the top of the fully compressed fork. I weigh about 220 today as I sit here on my couch. (Pounds, not kilos. Sheesh.)

What I can't figure is this. I can only get about 20mm dynamic sag (as in with me sitting on the bike dyamic.) Adjusting the preload changes it some, but the smallest I can get (preload all the way in) is about 15mm. I've tried two sizes of preload spacers, the second ones about 20mm larger than the first and a bitch to install, with no change in sag. :headbang:

Also, the bike seemingly experiences more fork dive now than it did with the progressive springs.

One thread on VSRI indicates I should be trying to get static sag of at least 40mm. I know it's all different with different bikes, but still. Half of that number doesn't seem right, and neither does the softness.

Any help out there? Am I just worrying about nothing here? :headbang:

 

[LordSmoke]

I could be 180 degrees wrong in my thinking, but wouldn't screwing in the preload and/or using longer spacers reduce dynamic sag? I'm approximately your weight and installed 0.95 sonics, and dyn-sag was spot on. I cut my spacers to match overall stock spring length. Still have substantial brake dive.

 

[SpringheelJack]

I could be 180 degrees wrong in my thinking, but wouldn't screwing in the preload and/or using longer spacers reduce dynamic sag? I'm approximately your weight and installed 0.95 sonics, and dyn-sag was spot on. I cut my spacers to match overall stock spring length. Still have substantial brake dive.

Yes, longer spacers *should* decrease sag. I was hoping it would stiffen things up some. But ... neither of those things changed.

Do you remember how long your spacers were? Did you factor in the OEM spacers in your measurements?

Thanks for the reply.

 

[dtalk]

The replaced spring is some kind of progressive spring - from the pics it doesn't look stock, at any rate.

FYI, just thought I'd throw in that the stock springs on the 650 are progressive. I'm not sure what the liter bike comes with.

 

[LordSmoke]

Yes, longer spacers *should* decrease sag. I was hoping it would stiffen things up some. But ... neither of those things changed.

Do you remember how long your spacers were? Did you factor in the OEM spacers in your measurements?

Thanks for the reply.

I recall that, as per the instructions, I laid out the whole stock spring assembly (spring, spacer, and maybe some other doodads) and cut the new spacer so the new assembly was the same length. That was on a six-fiddy.

Using a zip tie to measure things by myself, all sag settings and suspension travel during normal riding, including unpaved washboard roads, are spot on suggested values.

I put a few extra turns on the preload to reduce brake dive, but that didn't do much.

 

[PTRider]

Sag is set by the preload on the springs, both the spacers and the preload adjustment. The purpose of correct preload & sag is to get your suspension in about the middle of the travel for about equal chance of not bottoming out nor topping out. Reduce the preload adjustment and/or shorten the spacers to get the 40 mm sag. This does not effect the spring rate (stiffen things up) nor the brake dive. Brake dive will be effected by the spring rate and the damping rate.

 

[SpringheelJack]

Sag is set by the preload on the springs, both the spacers and the preload adjustment. The purpose of correct preload & sag is to get your suspension in about the middle of the travel for about equal chance of not bottoming out nor topping out. Reduce the preload adjustment and/or shorten the spacers to get the 40 mm sag. This does not effect the spring rate (stiffen things up) nor the brake dive. Brake dive will be effected by the spring rate and the damping rate.

Yeah, I realized this after waking up this morning and confirmed it with a tech article on the SonicSprings site. I was pretty fried late last night. So ... with a straight-rate spring, if I take XX off the spacer, do I get XX back in sag? It can't be that easy, I think ....

Also, per what LordSmoke wrote above ... the 650 has s different fork setup than the DL, but would matching the OEM - or in my case the PO's setup - spring and spacer length have any value?

Thanks everyone!