Suspension mods started

[ohiorider_imp]

Guth, I talked with Dan at TD a few days ago, and followed up with sag information for the fork.
Sag of CB1100 fork (09 25 17)
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”
So, 1" from fully extended no load to loaded with bike and rider. I had no one to hold me up, but I was able to keep the bike level with very little foot pressure, so I think the loaded reading is good. Used a zip tie on one fork leg to 'record' the loaded sag.

His first thought was that they may have provided spacers that were too long. He asked that I:
- elevate front wheel by elevating and allowing the fork to extend.
- remove one fork cap & measure the distance between top of fork spring and bottom of fork cap.
per Dan this measurement should be between 15-20mm.
- it measured 20mm, and the spring didn't seem to be under undue pressure.
- fork cap against the spacer was easily depressed and replaced.

They will be sending me a lighter set of fork springs to try. Re two additional bleed holes - we discussed, but he didn't indicate doing this.

I will be removing the fork tubes, draining them, removing the springs and GV emulators. I am not planning to split the forks, but leaving the TD damper rods in place. I will double-check the settings on both GV emulator springs. Probably go with lighter fork oil (10-15w), lighter fork springs, and slightly more air space. They recommend 125 mm below top of fork tube without springs or GVE in place.

That's where it stands at the moment.

Bob

[Guth_imp]

Interesting. Thanks for sharing! I'll be keeping watch on this thread for further updates.

[spacetiger_imp]

Guth, I talked with Dan at TD a few days ago, and followed up with sag information for the fork.
Sag of CB1100 fork (09 25 17)
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”
So, 1" from fully extended no load to loaded with bike and rider. I had no one to hold me up, but I was able to keep the bike level with very little foot pressure, so I think the loaded reading is good. Used a zip tie on one fork leg to 'record' the loaded sag.

His first thought was that they may have provided spacers that were too long. He asked that I:
- elevate front wheel by elevating and allowing the fork to extend.
- remove one fork cap & measure the distance between top of fork spring and bottom of fork cap.
per Dan this measurement should be between 15-20mm.
- it measured 20mm, and the spring didn't seem to be under undue pressure.
- fork cap against the spacer was easily depressed and replaced.

They will be sending me a lighter set of fork springs to try. Re two additional bleed holes - we discussed, but he didn't indicate doing this.

I will be removing the fork tubes, draining them, removing the springs and GV emulators. I am not planning to split the forks, but leaving the TD damper rods in place. I will double-check the settings on both GV emulator springs. Probably go with lighter fork oil (10-15w), lighter fork springs, and slightly more air space. They recommend 125 mm below top of fork tube without springs or GVE in place.

That's where it stands at the moment.

Bob

Bob,

Good informative post; a few observations:

1. Your static sag measurements are a bit on the low side; 1" out of 6.5" = 0.15. I would think you should be closer to 0.25 or as high as 0.3.
2. I note the preload spacer is long enough that when you get the fork cap on, it is introducing about 20mm of preload on the spring. A bit on the highside, but not bad - it really depends on the steel spring rate. A lower rate would use a longer spacer, a stiffer spring would use a shorter spacer.
3. The advise to set the oil level with the GVE out of the fork is not correct. The GVE will not compress, so it takes up a certain amount of volume in the fork just like oil. If you set the oil level with it OUT, then put the GVE in; the oil level will rise about an inch or 2.54cm. That is a lot. That could be part of the problem.
4. The lighter weight oil is a good thing. I'm going to guess they didn't too much adjustment to the GVE, so I would try the 10wt oil. The 125mm oil level is high as that converts so 4.92".

My recommendation until you hearback from TD: Cut a pvc spacer 5mm shorter than your current length. Use 10wt fork oil but go with a lower fill level (set with GVE IN, spring OUT) 7" from top (that is 175mm, not 125mm). That is going to sound high, but look at the side of the compressed fork and put a piece of tape (blue painters tape) and mark the oil fill level. Now look at that mark and picture the where the GVE is in relation to that mark (The GVE sits on top of the damper rod). You will see a BIG gap between the top of the GVE and the mark. That tells you you have plenty of oil to do the damping function - the oil level is to set the air spring. With less preload on the spring and a lower oil level to reduce the air spring + lighter weight oil to flow through the oil passages, I think you will find the bike will ride much smoother. You sag reading at 1" should be around 1.625" (0.25 x 6.5"). The shorter preload spacer and oil fill will help you get closer to that number. Once underway, the compression damping will be lessened so the front will feel better.

Also, can you measure the bike sag? to do this, lift the front end again, move the zip tie down the fork, then lower the front of the bike so only the weight of the bike is on the front suspension. Then lift the bike up and see how far the zip tie moved (it will be less than inch). The difference between that measurement and 1" is attributed to your 160 weight.

Jerry

[PowerDubs_imp]

Back in my dirt bike days I would measure sag both by raising the suspension and sitting down (in full gear) - measure- and then push down, let rebound and remeasure.


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[spacetiger_imp]

Back in my dirt bike days I would measure sag both by raising the suspension and sitting down (in full gear) - measure- and then push down, let rebound and remeasure.


Sent from my iPhone using Tapatalk

That gets you rider sag. You also want bike sag. The difference between the 2 lets you estimate spring rate.

[ohiorider_imp]

Jerry (Spacetiger,)

Your post is very informative, and I suspect that taking your advice I'll end up with a CB1100 with suspension that works for me. You mentioned dropping fork oil level to as much as 175mm. Got me to thinking about the instructions that came with a Progressive spring I installed on my 2003 Bonneville several years ago. They show a range anywhere between 140mm and 190mm below the top of fork tube.

Thanks again,

Bob

[spacetiger_imp]

I bought a set of 2014 CB1100 forks that had been a slight mishap for a different project. If I can get some time this coming week I'll try to get them apart to do some measurements. I just have to figure how to post pics since photobucket is toast.

Jerry

[Cormanus]

Pictures: Imgur.com or Postimage.org.

[ohiorider_imp]

I bought a set of 2014 CB1100 forks that had been a slight mishap for a different project. If I can get some time this coming week I'll try to get them apart to do some measurements. I just have to figure how to post pics since photobucket is toast.

Jerry

I could supply you with:
- the stock damper rod length
- length of stock springs
- length of stock spacers

Let me know if that would be useful. You may be looking for more detail, however.

Bob

[spacetiger_imp]

Bob,

I have a stock fork set, so I can get those measurements. Can you get the bike sag measurements?

Jerry