Suspension mods started

[ohiorider_imp]

Bob,

I meant for you to take bike sag readings on your current set up. Those will go with your bike sag readings from your earlier post.

I see your current springs are 0.9 kg/mm? That would convert to 50.4 lb/in. That is a bit high for your weight of 160 lbs. Your total steel spring capacity is preload plus spring capacity over 6.5" so, that would be (0.78" (20mm) x 50.4) + (6.5 x 50.4) = 39.7 + 327.6 = 367.3 lbs for a single fork. I am guessing they used a straight rate spring.

As a data point, I am 20 lbs heavier (180) and in my XL1200T (a little heavier than the CB1100) and I am running 0.85 lbs/in (47.6 lb/in) springs. I also have a shorter front suspension working range than your 6.5". I am also running lower oil levels so there is less air spring effect. In effect, your set up has about 20, possibly 30% (depending on oil fill) greater capacity than mine. And, your are lighter than me (by 20 lbs). You can see, even the "suspension guys" get it wrong. It seems like they set up the front suspension for a 200+ (aggressive) rider.

If I read your weight and spring rate correctly, you will have to go to lighter weight springs. A 0.8 kg/mm spring would lower your capacity to 35.3 + 291.2 = 326.5. That is getting you closer. A 0.75 kg/mm spring with only a 15mm spacer would have a capacity of 24.8 + 273 = 297.8 lb. That looks like a better starting point as you can adjust that capacity with your oil level. I know understand why your sag readings are too low (0.15). Also, the compression damping is adding to your over stiff suspension using the heavier weight oil.

Once I test the fork I have, I can tell you what the stock spring rating is.

Jerry

edit. The front suspension travel seems high at 6.5" The stock is 4.7". Are you at 4.7 or 6.5"?

Jerry, I didn't mean to imply that the total suspension travel was 6.5", but that when I measured (with wheel off ground - unloaded,) the distance between bottom of lower triple clamp and top of wiper was 6.5". Here's cut and paste from my previous post:
Bottom of lower triple clamp to top of wiper with front wheel off ground/fork fully extended: 6 ½”
Bottom of lower triple clamp to top of wiper with front wheel on ground, 160# rider in saddle: 5 ½”
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Not related to our discussion, but thought you might like to know: It appears that the stock CB1100 fork springs are progressively wound. I took these rough measurements this morning.

Total spring length removed from fork: 13.25" approx
10 tightly wound coils: 3"
20 loosely wound coils: 10.25"