Front fork oscillation under braking

[ohiorider_imp]

Should probably have said 'fork compresses and rebounds under light to moderate braking."

A couple of things I will try, in an effort to eliminate this.
1. First, I've swapped out the OEM fork springs, first with .90 weight, then went softer with .80 weight. Also installed Race Tech emulators. I mentioned this to the tech at Race Tech. He suggested going with heavier oil, since it was his opinion, after setting up bike forks for Race Tech for 18 years, that Honda SAE10 is too light. He reminded me that the RT valve is pretty much indifferent to heavier oil under compression, since heavier oil controls mainly the rebound damping.

2. Clean rotors with dry 3M green pad by elevating the front wheel, holding the 3M pad so that it cleans brake pad residue off the rotors as you rotate the wheel. Finish this off by wiping the rotors down with contact/brake cleaner and a soft rag. Think I'll try this first just to see if it makes any difference. Any of you cleaned your CB's rotors this way? Do you see any issues in doing so?

Bob

 

[Lord Popgun]

Thats pretty much how I clean my rotors. Doesn’t have anything to do with suspension rebound though.

I just don’t rotate while cleaning as I don’t want any thing going to the pads. Just in case. Clean what I can, rotate and repeat.

 

[GoldOxide_imp]

I have never serviced front disc brakes, never had a need. However, I have had a front disc go blue-glazed, but the bike was sold by that time. :-/

Disc pads, on the other hand, I have changed a few times.

 

[Cormanus]

Clean? What's that?

 

[the Ferret]

:rofl:

 

[flynrider]

Clean? What's that?

Slightly shinier than this?

 

[Cormanus]

That's how I like 'em, Flynrider.

Even though I recall there was a bit of fork oil mixed in which is not so good.

 

[The A-man]

Oh my! Is there a "CB Abuse Hotline"? I have a report to make!

 

[jtopiso_imp]

Should probably have said 'fork compresses and rebounds under light to moderate braking."

A couple of things I will try, in an effort to eliminate this.
1. First, I've swapped out the OEM fork springs, first with .90 weight, then went softer with .80 weight. Also installed Race Tech emulators. I mentioned this to the tech at Race Tech. He suggested going with heavier oil, since it was his opinion, after setting up bike forks for Race Tech for 18 years, that Honda SAE10 is too light. He reminded me that the RT valve is pretty much indifferent to heavier oil under compression, since heavier oil controls mainly the rebound damping.

2. Clean rotors with dry 3M green pad by elevating the front wheel, holding the 3M pad so that it cleans brake pad residue off the rotors as you rotate the wheel. Finish this off by wiping the rotors down with contact/brake cleaner and a soft rag. Think I'll try this first just to see if it makes any difference. Any of you cleaned your CB's rotors this way? Do you see any issues in doing so?

Bob

If the fork oscillates under braking due to the brakes, the the oscillation should be proportional to the speed. Does that happen?

Otherwise, it's about the damping or the tyre. And don't focus 100% on the front end, as the rear end could also be the culprit.

 

[the Ferret]

Clean? What's that?

Slightly shinier than this?

Slightly shinier than this?

or this? :rofl:

 

[GoldOxide_imp]

Clean? What's that?

Slightly shinier than this?

Slightly shinier than this?

or this? :rofl:

Lol - You must go through a "hose down" before entering the house?

 

[Cormanus]

 

[GoldOxide_imp]

Knarly Cormanus.

Is there gonna be a thread started called, "The most hideous CB1100?"

 

[the Ferret]

:rofl: Cormanus would win since I never ride on dirt roads. No sir if I'm riding on dirt it's because I've blown a turn

 

[GoldOxide_imp]

Heh, it would be interesting to showcase a few in the Estate Realm Dungeons.

 

[dave]

Should probably have said 'fork compresses and rebounds under light to moderate braking."

Sounds like a warped brake rotor. Do you have a dial indicator to check it? I purchased an inexpensive dial indicator at Harbor Freight.

 

[Cormanus]

Thank you, Dave, for returning the thread to some semblance of sanity.

On the other matter, the Ferret is correct.

 

[ohiorider_imp]

Dave, I do have an inexpensive dial indicator (Harbor Freight) but it was certainly good enough to check the run out on my R100GS. I doubt it is a run out issue with either of the front discs. More inclined to think that I've gone so soft on the front fork springs, and am running light fork oil. Matt Wiley from Race Tech immediately suggested I move up to either 15 or 20 wt Honda fork oil, since, with the Race Tech Valve, oil wt has little or no effect on compression damping, but is how rebound damping is controlled.

Aside from the very slight pogo'ing issue, the bike's suspension is now compliant enough I can take on most every secondary road in the area. I've only owned two bikes in the recent past that caused me to avoid many of my favorite roads, the 2012 Moto Guzzi Griso, and the CB1100.

Still, I'm going to try the '3M pad and brake cleaner' routine, just to see if the easy fix actually does any good. If not, its dial indicator time!

Bob

 

[Lord Popgun]

Someone is going to have to explain to me how rotor warpage affects suspension compliance. Cause I don’t get it. Pulsing or shimmy I get.

 

[ohiorider_imp]

Someone is going to have to explain to me how rotor warpage affects suspension compliance. Cause I don’t get it. Pulsing or shimmy I get.

Popgun, sorry if my original post was confusion. Let me try to clarify. I wasn't intending to imply that rotor warp would affect suspension compliance. I meant that, after making incremental changes to the spring weight and to the Race Tech Valve, that I now have the CB1100 suspension where it is compliant for me and my weight. However, with the .80 weight fork springs, the front end may tend to want to pogo slightly under braking. It's now up to me to determine if this is because:
- rotors have spots where brake pad deposit causes brake to pulsate.
- rotor warpage.
- the fork springs are now so light that minor issues with brakes are transmitted thru suspension.
- If the fork oil is too light, which in turn doesn't control fork rebound movement as it should. That was the opinion of Matt Wiley, an 18 year tech support individual with Race Tech.

Bob