|   Fox Shox tech support | Man+Bike=Mike
Oct 15, 2003 10:02 AM | | I was wondering about some peoples experience with Fox Tech. I was thinking about sending my Vanilla back for repair until I had this story relayed to me by my good friend B----.
B calls Fox to set-up an RA for some bushing play. The tech says that the bushings are "life bushings" meaning they don't wear out. B states that he has the fork out of the bike in a work stand and can rock the lowers back and forth on the uppers. Fox tells him that they have NEVER had any bushings wear out on a Fox Fork. He then says that the oil is low in the damper (would cause a gap in the lockout). B says that there is no gap in the lockout. Fox maintains it could not be the bushings.
After hearing this and reading another post (which I couldn't find) regarding Fox telling a customer that slight bushing play is a "design feature". I am skeptical about what on earth these guys are doing.
Anyone else had an experience like this? Is Fox trying to blow smoke up our asses? |
| Here's their explanation of the "design feature" | Mikey
Oct 15, 2003 10:16 AM | | From the manual [snip]...
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FOX FORX use hydrodynamic lubrication. In our system, oil is force fed into the tall slotted bushings during the compression stroke. When the fork cycles up and down the oil is trapped between bushings, upper tubes and seals.
...
Show Room Testing - As you rock the fork back and forth while stopped with the front brake applied, the bushings have only a small amount of lubricant separating the bushing / upper tube. At this time you may notice a small amount of bushing play. Fork bushings must have clearance to perform correctly. Too little clearance will cause high friction, binding or bushing seizure when hot.
Real World Testing - During normal riding conditions, hydrodynamic lubrication occurs when there is a complete separation of the upper tube from the bushing by a thin film of oil. Hydrodynamic lubrication is characterized by very low friction and no wearing of the bushings or shaft since there is no metal to bushing contact. During hydrodynamic lubrication normal bushing clearance will not be noticeable.
Bushings should be checked annually for excessive wear. If excessive fore and aft movement is detected between the upper tubes and lower legs, contact an Authorized FOX Racing Shox Service Center or FOX Racing Shox for further instructions. Grasp the lower legs at the drop outs (axle). Push the fork straight back towards the rear wheel. Then pull it towards you. Next grasp the fork near the upper tube/seal junction and try the same thing. If excessive movement is noticed, refer to page 4 of this manual and contact FOX Racing Shox or an Authorized FOX Racing Shox Service Center.
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I guess you need an expert opinion as to whether you have normal or excessive play. Is there a shop near you that's really experienced with the Foxes? |
| Here's their explanation of the "design feature" | Man+Bike=Mike
Oct 15, 2003 1:50 PM | | I have read the manual on several occasions. Being senior mechanic at a shop, I have worked on Fox, Manitous, Rock Shox, Marzocchi Forks for years...and am well aware of what is and isn't acceptable.
From what the manual says, the uppers are "hydroplaning" on bushings. In a perfect world, this might work, but there is no way a fork is ever subjected to perfect linear load with each impact. In fact, I would dare say this may never happen.
Also, oil does not rest all the way to the upper bushing. This means that before there is even a possibility of this working, the uppers have to plunge so far into the lowers as to push oil to the upper bushing, but not cause a hydraulic lock of the fork.
Every other fork manufacturer recommends replacing loose bushings to avoid premature wear on other fork components.
How is bushing play a positive feature all of a sudden? |
| Here's their explanation of the "design feature" | Dougal
Oct 15, 2003 2:19 PM | | Hydrodynamic bearings are used in engines. It's a great setup but to acheive it you need either fast shaft speed to pull the oil into the gap or pressurised oil.
I can't see either happening inside a fox fork. Take a look at 123shocks.com for a solution to fox bushing play.
Dougal.co.nz |
| Where on the 123shocks.com website is that? (nm) | DaveG
Oct 15, 2003 4:22 PM | | |
| 2nd paragraph from the bottom. nm | Dougal
Oct 15, 2003 7:31 PM | | nm |
| So, 123shocks can fix bushing play, but Fox says it's hydrodynamic lubrication... | SS_MB-7
Oct 16, 2003 5:53 AM | | "Ex: loose bushings? Depending on the fork and age of the fork, it might or might not be worth having repaired vs. the cost of a new fork. I can tighten up Fox fork bushings IF, and I say IF this is really the problem. Be absolutely sure your headset is tightened correctly, grab front brake firmly, rock fore and aft to determine where the loose feel is coming from. Many a times it has been a loose headset or loose brake and brake pads especially on disc brakes."
So, 123shocks.com can tighten up Fox bushings, but Fox says it's "hydrodynamic lubrication". Any idea what 123shocks does to "tighten" the Fox bushings? How will this impact the design intent of "hydrodynamic lubrication"?
Ride Hard,
Mike B.
http://www.one-speed.com |
| So, 123shocks can fix bushing play, but Fox says it's hydrodynamic lubrication... | Threesticks
Oct 16, 2003 7:21 AM | | Has anybody put a micrometer to the bushings and legs to get the ID and OD to see what the measured clearance is? I think that this would be better that going by "feel". |
| So, 123shocks can fix bushing play, but Fox says it's hydrodynamic lubrication... | DGC
Oct 16, 2003 7:42 AM | | I wont tell anyone how I do the bushing tightening, I will tell you this, not all Fox forx come out of the box with the same bushing tollerance set up. I have checked and or ridden a few hundred to come up with what I call loose bushings. The Bushings are also slotted which allows oil to pass all the time no matter how tight or loose they are. Some people having come in the shop locally with what they claim as loose bushings has been something else not the fork like headset, brake pads, rear shock bolts etc, so be sure before you claim loose bushings. I also put more than the 30cc's in the spring side leg. For the company to say it needs to be what feels like slightly loose to allow oil to pass by the slotted bushings yet they put so little oil in the spring side to get up to or past the upper bushings seems a little silly. I am running 50 cc's in my spring leg Vanilla RLC, and have run 100 cc's a few times before with no problems. The extra oil does not cure loose bushings, it might quiet them down while riding. My bottom line: Fox has a tollerance guideline they adhere to, I think it is too loose. Why do other fork manufacturers out there have no bushing play and their forks work just fine?
Dave C.
123 Bikes. |
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