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  1. #1
    MK_
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    Changing travel on Fox F80/100 forks

    I remember this question coming up before, whether it was possible to adjust the travel on these forks. There was no certain answer and the best I got from Fox was that I needed to purchase a new assembly for the left leg (air spring side). Quoted at $30. Not bad, but not free. A while ago I picked up a used F80 RLT to use on my race bike. The frame was designed around a 100mm fork, but I figured to give 80mm a shot anyway, since it would drop the front end a bit and give faster steering. I didn't like the ride so I decided to open up the fork and check out the guts, and change the travel and oil. I was happy to see that the person who sold the fork to me did a complete overhaul prior to the sale and the oil inside was pristine. Anyway, onto the travel adjustment.

    In Floats and Vanillas travel adjustment is as easy as a rearrangement of spacers. In Floats it is easierst, since there are less springs. In case of the F series forks, this is more complicated, because in order to save all possible weight there are no spacers, simply, the travel adjusters, if you will, which are pinned into the assembly.

    In order to change travel, you don't need to touch the right leg at all, the one with rebound/lockout/threshold adjustment, only the left one, where the air spring is. Simply unscrew the bolt in the bottom of left leg with a 10mm wrench, and unscrew the top cap with a 26mm wrench. It will also help to remove the air valve cap before undoing the leg cap. Remember to let all the air out before doing any of this, otherwise you might have a little explosion of high viscosity oil. Let the oil drain out and remove the plunger assembly from the leg. This is also a good time to wipe down the inside of the slider and stanchion. The assembly will look like so:



    Examining more closely you will see a hole obove a black ring, like this:



    The black ring has a hole in it as well, through which a pin is inserted. In the picture it is sitting in the 80mm position. At first glance I was pessimistic as to my ability to do anything about it, however, I took a nail and flattened the end, inserted it into the hole in the black ring and banged at the pin with the hammer. (I would advise against a use of a sharp tipped object because the pin is hollow on the inside and the last thing you would want to do is to make the thing expand) After a bit of banging here's what it looked like:



    and a closeup:



    Now, just bang it out further until it almost comes out of the black ring. Try not to get it all the way out, because it might be difficult to insert back into the ring, but I am not sure. You will see when the pin leaves the shaft because the ring will be loose. Slide it to the upper hole and bang it back in:



    Voila! Your F80 fork is now F100. To lower travel just do the reverse. Assemble your fork back up, fill with proper amounts of oil. 20ml in the bottom, 7wt oil, like Maxima. 5ml of Float fluid at the top, to form the air seal.

    _MK
    Last edited by MK_; 03-28-2005 at 02:59 PM.

  2. #2
    nnn
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    It's funny how they provided a hole for increasing travel really cool

  3. #3
    MK_
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    The interesting thing is that the sliders are the same length as the rest in the Fox lineup. It makes me wonder if one could drill a hole a bit higher up and have a longer travel F fork, which would probably ride smoother due to increased air volume, not to mention longer stroke. At the same time, the construction of the F series forks is noticably weaker than that of the rest. The truss brace on the stanchions isn't present, the upper crown has a bit of material removed and the steerer is weaker. Makes me wonder about the feasiblity of the idea.

    _MK

  4. #4
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    Cool pix. My question is that if I want to lower my F100RL to 80mm, do I need to order a spacer from Fox or is it as easy as just re-arranging the spacers inside?

  5. #5
    MK_
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    Quote Originally Posted by Enoch
    If you have a travel adjust spacer I would use it, otherwise you can move the roll pin as described above. The spacer is just easier.
    Exactly. Also, if you're an ultra weight weenie, move the pin.

    _MK

  6. #6
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    If you have a travel adjust spacer I would use it, otherwise you can move the roll pin as described above. The spacer is just easier.

  7. #7
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    thanks...

    Quote Originally Posted by MK_
    Exactly. Also, if you're an ultra weight weenie, move the pin.

    _MK
    Thanks MK, a long time ago, I had the same question and nobody answered it, so looking at your pics, I cleared all my doubts.

    Something I need to know about forx user`s is how thick your drop-outs are. I ask this, because the "service frame" that appears at the first pages of the user manual, saying that they must be 6.20mm or thicker got me thinking. Mines are something like 6.22-23mm, (1 year of use). How thick are yours?

    Tanks a lot!
    bye

  8. #8
    Lurking Homer
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    Nice post. Are the stanchions and lowers the same as an F100? I was under the impression that the stanchions were shorter and in-turn would make it so that there was not enough contact between the bushings and the stanchions. Does the fork seem to yeild any play now? Also, what year is it?

    Thanks for the great pics and descrip.

    L-Dogg

  9. #9
    MK_
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    Quote Originally Posted by fran
    Mines are something like 6.22-23mm, (1 year of use). How thick are yours?
    I haven't measured them, but this is stricktly because the fork that I got had almost zero use and the dropouts are the 2004, beefed up ones (vs 03 and earler).

    Quote Originally Posted by L-Dogg
    Are the stanchions and lowers the same as an F100? Does the fork seem to yeild any play now? Also, what year is it?
    The entire fork is identical, the only difference is where the spacer is pinned. No play in the fork, it is also much smoother due to increased air volume, much smoother. Year is 2004. Also, the only difference between this and the X series or innertia valve forks is the addition of the innertia valve in the damper leg.

    _MK

  10. #10
    try to re member
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    get the right tool

    Harbor Freight has a set of roll pin punches for $3.49:

    http://www.harborfreight.com/cpi/cta...emnumber=32954

    They have lots of other uses, too.

    Dave
    www.davewilson.cc

  11. #11
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    This is good info, thanks.

    I'm curious what the air volume chamber measures. It would be easy to measure from the top of the stanchion tube to the top of the air piston with the fork fully extended.

    So the cartridge was obviously long enough to extend to 100 mm as well? I wonder if this means it is the same cartridge as used in the 100 mm and maybe even the 130 mm versions?

  12. #12
    MK_
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    Quote Originally Posted by B R H
    I'm curious what the air volume chamber measures. It would be easy to measure from the top of the stanchion tube to the top of the air piston with the fork fully extended.

    So the cartridge was obviously long enough to extend to 100 mm as well? I wonder if this means it is the same cartridge as used in the 100 mm and maybe even the 130 mm versions?
    The cartridge wouldnt' extend much past 100mm, if you wanted to go higher, you would need a new one. Sliders on the other hand looked to be the same length as the rest of 32mm Fox brethren. As of the air volume, I would love to help, but Float fluid is so damn expensive, I dont' want to open up the spring side again, also, you would need to measure from the bottom of the threads to the top of the plunger, not top of the crown/slider, since the air valve that screws in with the cap goes in to the end of the threads. You could probably estimate it as 100mm + a few times the internal diameter of the slider or 80mm + a few...

    _MK

  13. #13
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    You shouldn't lose any fluid.

    Unless yours is different than my 2005 F100, all I have to do is unscrew the top cap, drop a rule in there, and extend the fork. In fact, I just did this and I get 144 mm from the top of the crown (flat machined sealing surface - top of threads) to the top of the air piston. It took less than 5 minutes.

  14. #14
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    My 2005 F100 measure 7.3-7.4 mm. There is no visually obvious wear, other than no paint, to the dropout clamp area.

  15. #15
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    that`s too thick (i think...)

    Quote Originally Posted by B R H
    My 2005 F100 measure 7.3-7.4 mm. There is no visually obvious wear, other than no paint, to the dropout clamp area.
    Thanks B R H. But did you measure them right?. No offense, I mean, 7.4mm seems to thick. Mine is a 2004 float model OEM. Are you measuring it, in the part where the hub and the QR go (clamp area)? Or the whole drop-out?

    Thanks again!

  16. #16
    MK_
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    Quote Originally Posted by fran
    Thanks B R H. But did you measure them right?. No offense, I mean, 7.4mm seems to thick. Mine is a 2004 float model OEM. Are you measuring it, in the part where the hub and the QR go (clamp area)? Or the whole drop-out?

    Thanks again!
    I wouldnt' be surprised if they were that thick. I got an 05 vanilla and the dropouts were massive compared to 04 Float.

    _MK

  17. #17
    MK_
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    Quote Originally Posted by B R H
    Unless yours is different than my 2005 F100, all I have to do is unscrew the top cap, drop a rule in there, and extend the fork. In fact, I just did this and I get 144 mm from the top of the crown (flat machined sealing surface - top of threads) to the top of the air piston. It took less than 5 minutes.
    Well, there's your answer I don't think that 04 is any different in volume. Also, a better measurement would be from the bottom of the threads, to get the actual air volume of the inside of the fork.

    _MK

  18. #18
    Chrome Toaster
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    Most excellent post! Thanks for the info. I have an F80 RLT 2005 and was wondering the same exact thing. My biggest concern was that the stanctions might be shorter to save weight and that would make it very difficult to increase the travel. I did pretty much the same mod to my Manitou Black. I found they had the notches drilled into the piston shaft precisely were you would need to put the stopper to change the travel. The difference is manitou did shorten the stanctions to save weight so you could reduce travel but not increase it beyond the original spec without a new set of uppers.

  19. #19
    MK_
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    Quote Originally Posted by Hecubus
    Most excellent post! Thanks for the info. I have an F80 RLT 2005 and was wondering the same exact thing. My biggest concern was that the stanctions might be shorter to save weight and that would make it very difficult to increase the travel. I did pretty much the same mod to my Manitou Black. I found they had the notches drilled into the piston shaft precisely were you would need to put the stopper to change the travel. The difference is manitou did shorten the stanctions to save weight so you could reduce travel but not increase it beyond the original spec without a new set of uppers.
    Next time I do an oil change, I should measure the length of the sliders (per Marzocchi manual, circa 2000, stanchions are the parts that are commonly called lowers and sliders are what is commonly called stanchions. I am confused as to what is proper so I will use Marzocchi terminology). It appeared that the sliders were standard length, however, the limiting factor is the damper, anyway, not the sliders, therefore, you can't really go above 100mm without spending money.

    _MK

  20. #20
    WC3
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    Close to full travel at 80mm?

    I have a Fox F100RL and the most travel I have been able to get out of it is 75-80mm, so I was wondering when you had your Fox Fork set for 80mm did you get near 80mm of travel? Good post & pictures! I think I'm going to change my Fox to 80mm and see how it rides.........

  21. #21
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    By stanchions I'm refering to the upper tubes that attach to the crown. The bottom leg castings(is this what you refer to as sliders?) are the same on all models regardless of the travel. My concern is with the stanchion length because if they are shortened to save weight there will be less bushing overlap when the travel is extended.

    Quote Originally Posted by MK_
    Next time I do an oil change, I should measure the length of the sliders (per Marzocchi manual, circa 2000, stanchions are the parts that are commonly called lowers and sliders are what is commonly called stanchions. I am confused as to what is proper so I will use Marzocchi terminology). It appeared that the sliders were standard length, however, the limiting factor is the damper, anyway, not the sliders, therefore, you can't really go above 100mm without spending money.

    _MK

  22. #22
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    More measurements.

    On my 2005 Fox F100 RLT OEM: stanchions measure 300 mm in length (not including the portion that is pressed into the crown). The air chamber measures 144 mm (top of crown to top of air piston).

    On my 2005 Fox Float 130 R: stanchions measure 300 mm in length (not including the portion that is pressed into the crown). The air chamber measures 174 mm (top of crown to top of air piston).

    The only difference I can see between the 100 & 130 is the extra material removed from the arch on the leg castings of the 100 (565 vs. 538 grams, but neither are perfectly clean yet). The steerer is black on the 130 & silver on the 100, but both are aluminum and seem to be the same otherwise. The air piston is white on the 130 and black on the 100, but are otherwise appear identical.

    The Stratos ID cartridge is the same for the 100 & 130 but different for the 80.

    It would be really nice if someone could provide these same measurements for an 80 mm fork.
    Last edited by B R H; 03-29-2005 at 03:22 PM.

  23. #23
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    It's correct.

    I just checked it again.

  24. #24
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    My understanding is 2004 is different.

    Fox advertises that they made the spring rate more progressive for 2005 models. In other words, I believe the air chamber is smaller for 2005 for a given amount of travel.

    PS. At this point I don't really care what the actual volume is. I'm just looking for an easy to repeat measurement to encourage others to post info on the other Fox models. If I wanted to get the exact volume, I'd probably measure it with fluid instead, but it's really not that critical.

  25. #25
    MK_
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    Quote Originally Posted by WC3
    I have a Fox F100RL and the most travel I have been able to get out of it is 75-80mm, so I was wondering when you had your Fox Fork set for 80mm did you get near 80mm of travel? Good post & pictures! I think I'm going to change my Fox to 80mm and see how it rides.........
    First, make sure the air spring is set to your body weight. If it is, open up the right leg, the one with the lockout lever and take out 5ml of oil. close it back up, and go for a short ride, you should be getting more travel already, if it still isn't full 100, take out another 5, until it is. It is comon that forks have too much oil in them from factory.

    _MK

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