| Author | Message | ||
     Moosestang |
I decided to measure my sag. I turned the front fork preload to full soft and I only have 30mm of sag with the minimum preload. Are these springs just super stiff or do i need to start packing on the pounds? I didn't do the measurments in full gear, but even with helmet/boots/jacket I cant' weight much more than 150, which is probably good for 1-2mm. Are you light weights just running very little sag or did you set the preload to minimum? For anyone curious, my CR's front forks measure 133mm full unloaded and 103mm with me sitting on it balancing between a doorway. | ||
| Kevin_stevens |
When you say fully unloaded, you mean with the front wheel off the ground, right? That's the starting point, not with the bike weight on it (sometimes called "static sag"). KeS | ||
| Moosestang |
Yes, fully off the ground. I used straps to lift the front by the bars. With the bikes weight it measures 113mm. | ||
| Kevin_stevens |
So something's a bit off. You're getting 20mm sag from the bike's weight (~1/2 of 450lbs = 225lbs), but only an additional 10mm from your 150lbs. The initial sag numbers would predict more like 150/225*20mm= ~15mm from your weight, which would get you to a reasonable 35mm. Did you include your stiction average? (Rider on, press down, release, measure. Rider on, lift up, release, measure. Average the two.) KeS (Message edited by kevin_stevens on November 10, 2009) | ||
| Moosestang |
No I didn't, but I will. I don't see the average being that much different. The 103 was measured after using the front brake to compress the forks. I understand your math, but why 1/2 the bikes weight and not half my weight? I only weigh 140. Does it matter what compression is set at for measuring sag? rebound? I wouldn't think you would get the same amount of sag for every 10lbs (random #) you add. You would get less and less the more the forks compress, no? (Message edited by moosestang on November 10, 2009) | ||
| Kevin_stevens |
Duh, you're right, it's a fraction of your weight and I'm sure that's the discrepancy. Damping *shouldn't* matter for sag at all, but I usually set it with all the clickers all the way out, simply because it's my first setup step. Damping should only affect how quickly the suspension responds, not where it winds up. If you have straight-rate springs (you do), then yes, the response should be linear, at least on the forks. The shock sometimes is not because it operates through a linkage that may have a leverage curve as it moves. You'll hear things like "shock rate" vs "wheel rate" to capture the difference. A straight-rate fork preload should be pretty linear until a) the air spring effect of the air captured above the oil level begins to have a measurable effect, or b) the fork springs themselves deviate from a theoretical spring as they approach coil bind. KeS (Message edited by kevin_stevens on November 10, 2009) | ||
| Moosestang |
Kevin, you know way to much about suspension.  I forgot that I measured the static sag with 2 turns on the preload. The fork measurment was 106mm with me on it and 2 turns of preload. It only changed 3mm by setting the preload to 0 turns. | ||
| Kevin_stevens |
I know a lot about CAR suspension. I only know enough about bikes to get me in trouble.  KeS |
