Installing a 140mm fork on a frame designed for 100mm- Mtbr.com
Results 1 to 34 of 34
  1. #1
    mtbr member
    Reputation:
    Join Date
    Oct 2009
    Posts
    32

    Installing a 140mm fork on a frame designed for 100mm

    Apart from the obvious like voiding the warranty, what are the advantages and disadvantages of installing a fork with a longer travel then intended for a hard tail frame?

  2. #2
    mtbr member
    Reputation:
    Join Date
    Nov 2008
    Posts
    423
    a broken headtube

  3. #3
    mtbr member
    Reputation:
    Join Date
    Oct 2009
    Posts
    32
    What are the odds of that happening? I've heard that quite abit, but it seems like it's not really happened to anyone either.

  4. #4
    GAME ON!
    Reputation: saturnine's Avatar
    Join Date
    Mar 2007
    Posts
    4,965
    depends on the frame. if you think it's never happened, you're naive.
    RIP Adam Yauch

    "M.C. for what I AM and do, the A is for Adam and the lyrics; true"

  5. #5
    mtbr member
    Reputation: hitek79's Avatar
    Join Date
    Oct 2008
    Posts
    1,313
    I say go for it. Don't be a p*ssy.

  6. #6
    What could go wrong ...
    Reputation: Zoke2's Avatar
    Join Date
    Nov 2007
    Posts
    1,996
    not to mention the horrid handling that will ensue
    I used to ride to Win ... Now I ride to Grin

    While my guitar gently weeps, my bike sits there mocking me

  7. #7
    mtbr member
    Reputation:
    Join Date
    Jun 2005
    Posts
    659
    140mm would be too long, I did this to my wife's trek fuel 80 wsd, but I put a psylo (80mm to 125mm) and she loved it. again 140mm not only would mess up the 'geo' but would make it very 'dangerous'. After all i love my wife smile......with all her teeth!

  8. #8
    mtbr member
    Reputation:
    Join Date
    Nov 2008
    Posts
    423
    I broke a downtube on a stock anthem, so I'm not the best to ask. I did go from a 80mm to 100mm fox on a haro 29er with no problems. What frame you got?

  9. #9
    mtbr member
    Reputation: Mr Cabletwitch's Avatar
    Join Date
    Apr 2009
    Posts
    445
    Unless its an adjustable fork and you plan to run it around 100mm most of the time I wouldn't do. 120mm is the most I would do. I did put a 130mm fork on a bike built for 100mm, but it was a Uturn fork so I ran it at 110 most of the time and ran it at 120 for some downhills, but 130 just didn't feel right at all

  10. #10
    Fo' Bidniz in da haus
    Reputation: FoShizzle's Avatar
    Join Date
    Jan 2004
    Posts
    17,281
    Quote Originally Posted by Kevin_Federline
    a broken headtube
    yep...the rest of the disadvantages vary in magnitude given the riders preferences, skill level, and riding style/terrain. a broken frame is objective risk that only a retard (i.e., 99% of MTBR viewers) would consider

    there are some VERY affordable and EXCELLENT longer travel (i.e., AM) hardtails which will be designed for such a fork and as such will be optimal

  11. #11
    Takin'er easy
    Reputation: Joss DeWaele's Avatar
    Join Date
    Nov 2004
    Posts
    184
    The longer travel fork will give you a slacker head angle, which for many riders is preferable for descending. However, the longer fork will also raise the bottom bracket, bringing your feet higher off the trail, and also raising your center of mass. For anyone who has ever played any stick-and-ball sports, you'll know that a lower center of mass is a more ideal athletic position.

  12. #12
    mtbr member
    Reputation:
    Join Date
    Oct 2009
    Posts
    32
    Thanks for the feedback. Don't think I'll be going that route!

  13. #13
    mtbr member
    Reputation: Luigiugueto's Avatar
    Join Date
    Oct 2007
    Posts
    1,538
    Besides putting your teeth in danger, you'll mess up the geometry, sell your 100mm frame and buy one suited for a larger shock

  14. #14
    mtbr member
    Reputation: Broccoli's Avatar
    Join Date
    Jun 2008
    Posts
    5,762
    If you can spend money on a 140mm fork, you should spend a little bit more on a proper frame that is designed for it. Inbred 456 for example.

    There is no good reason to slap 140mm fork on a frame that is designed for 100. It will no ride better and it may break, like many other already noted.

  15. #15
    mtbr member
    Reputation: k31ron's Avatar
    Join Date
    Jul 2008
    Posts
    104
    I put a 130mm RS fork on my Kona which came with a 100mm Marz fork, although the RS had 30mm more travel due to the marz fork having vey long lowers (in comparison to RS) it actually only increased the A2C by about 10mm so barely changed the Geo but gave the bike a whole lot more travel...worth baring in mind, a longer travel fork may have less affect then you think (or vicer versa) depending on manufacturer.
    Last edited by k31ron; 11-12-2009 at 04:02 AM.

  16. #16
    mtbr member
    Reputation: Broccoli's Avatar
    Join Date
    Jun 2008
    Posts
    5,762
    Quote Originally Posted by k31ron
    I put a 130mm RS fork on my Kona which came with a 100mm Marz fork, although the RS had 20mm more travel due to the marz fork having vey long lowers (in comparison to RS) it actually only increased the A2C by about 10mm so barely changed the Geo but gave the bike a whole lot more travel...worth baring in mind, a longer travel fork may have less affect then you think (or vicer versa) depending on manufacturer.
    Forks with shorter A2C are shorter at full compression - so it makes maximum head angle steeper (by almost a degree in your case). You may, or may not like how it affects handling.

    In your case, with 30% sag you do get you almost the same angle, (130mm fork will be sagged 39mm, and 100mm fork - 30mm, so here goes your 10mm) and ~1 deg steeper at full compression.

  17. #17
    mtbr member
    Reputation: k31ron's Avatar
    Join Date
    Jul 2008
    Posts
    104
    Quote Originally Posted by Curmy
    Forks with shorter A2C are shorter at full compression - so it makes maximum head angle steeper (by almost a degree in your case). You may, or may not like how it affects handling.

    In your case, with 30% sag you do get you almost the same angle, (130mm fork will be sagged 39mm, and 100mm fork - 30mm, so here goes your 10mm) and ~1 deg steeper at full compression.
    thats a very good point, (sorry when i said ~10mm greater A2C - I meant when sagged) so I get a ~1deg slacker angle when not compressed and ~1 deg steeper when loaded (which i hadn't thought about) but i guess that's the nature of longer travel forks your going to get a greater range of HA change from un-compressed to compressed the more travel you have. The HA is pretty slack on my Caldera anyway and with more suspension I tend to spend less time fully compressed - so Its working pretty well.

  18. #18
    ChiliPepper1
    Guest
    Quote Originally Posted by skyn
    Apart from the obvious like voiding the warranty, what are the advantages and disadvantages of installing a fork with a longer travel then intended for a hard tail frame?
    First, what HT frame do you have bro or disciplined frame (XC, AM, FR, DJ)?

    If it is a XC bike frame, then definitely not recommended, but running a adjustable or a 120mm would be OK. Why do you really want that much travel anyways? Are you going to be doing a lot of DH or big hit drops? If you really want a bike with that much fork travel for a HT, then just spend the monies on a frame that is suited for that long travel. Ya know what I mean bro.

  19. #19
    mtbr member
    Reputation:
    Join Date
    Jul 2009
    Posts
    44
    What about a 120mm fork for a bike that had 100mm stock? I do like jumps and drops, but not trails where that's all it is and I don't do anything extreme, i.e. not doing like 4' drops or jumps over 2' tall. Other than that I believe my riding falls into XC. I guess it boils down to just piece of mind thinking I probably wouldn't bottom out a fork with a little more travel than stock. My ride is a HT.

  20. #20
    mtbr member
    Reputation: Broccoli's Avatar
    Join Date
    Jun 2008
    Posts
    5,762
    Quote Originally Posted by PiranhaFisher
    What about a 120mm fork for a bike that had 100mm stock? I do like jumps and drops, but not trails where that's all it is and I don't do anything extreme, i.e. not doing like 4' drops or jumps over 2' tall. Other than that I believe my riding falls into XC. I guess it boils down to just piece of mind thinking I probably wouldn't bottom out a fork with a little more travel than stock. My ride is a HT.
    Note that on a hardtail effect on angles is stronger as only one end sags. There are a bunch of adjustable travel 120mm forks - maybe that is something you could check out..

  21. #21
    ride more
    Reputation:
    Join Date
    Mar 2007
    Posts
    2,626
    without knowing what frame your talking about, I'd say 120mm would be better.

  22. #22
    mtbr member
    Reputation:
    Join Date
    Feb 2016
    Posts
    1
    Quote Originally Posted by FoShizzle View Post
    yep...the rest of the disadvantages vary in magnitude given the riders preferences, skill level, and riding style/terrain. a broken frame is objective risk that only a retard (i.e., 99% of MTBR viewers) would consider

    there are some VERY affordable and EXCELLENT longer travel (i.e., AM) hardtails which will be designed for such a fork and as such will be optimal
    Even though this is a very old post I wanted to share my experience here as before upgrading my 100mm fork to 140mm I was googling for advice and this and this post was one of the first to show up.

    It is really confusing to read all of this. I totally agree that broken frame (HT) has nothing much to do with a fork. If the head tube will brake it will brake because of what you do with the bike (bigger jumps etc.) not because of the fork. Few degrees cannot affect stiffness of the frame. It would be the same to say that your shorter travel fork will brake head tube if you will be descending by same degrees, not to mention what would happen landing after a jump in different angles.

    Not to mess up geometry of a bike you should compare axle-to-crown length. Rising a front by 40mm wouldn't be such a good idea however it still won't brake the frame.

    as k31ron mentioned, difference in travel length of the fork does not always change the overall length of a fork by the travel length difference.

    My SR Suntour 100m fork had a stanchions almost 115mm (even though travel is 100mm), thicker crown and a bit longer lowers compared to FOX float 32. At the end front of the bike raised for less than 20mm, considering a bit higher sag on 140mm there is almost no difference in geometry after putting 140mm fork.

  23. #23
    mbtr member
    Reputation: scottzg's Avatar
    Join Date
    Sep 2006
    Posts
    6,494
    This thread comes up fairly frequently.


    New rider- 'i want to inexpensively make my beginner bike more competent on the intermediate trails i'm trying with a taller fork!'
    Experienced riders- 'that's not a good idea, it exposes you to risk and goofs up the handling, there's better ways to do this'
    That guy- 'but there's about a thousand details and exceptions we can debate!'
    *rabble rabble rabble*
    New rider- 'well i'm confused so i did it anyway, and now i can straightline stuff better and it's been 4 months and i'm ok! thanks!'
    "Things that are complex are not useful, Things that are useful are simple."
    Mikhail Kalashnikov

  24. #24
    Life Is Short
    Reputation: fatcat's Avatar
    Join Date
    Mar 2006
    Posts
    2,569
    about 90% of the time when someone asks about this 140/130mm fork for a hard tail its because they either
    1)can get it free or cheap
    2)can't afford a long travel bike

    thats it man.serious. its all about the money.
    Cheap people buy things twice

  25. #25
    mtbr member
    Reputation: One Pivot's Avatar
    Join Date
    Nov 2009
    Posts
    9,448
    You wont die. It'll ride weird. Give it a shot.

    Imagine if bikes really were designed where the limit between breaking the head tube off and smashing your teeth out, or juuust not breaking was that small!

    Just check out what 40mm really looks like, and picture in your head just how much added force that is. Theres already a 500mm lever, 540mm is 8% more leverage. If your frame is designed with an 8% safety margin, it was junk to being with.

    Broken head tubes were a lot more common when drops to flat were still popular. Just keep it sane and you'll be alright.

  26. #26
    mtbr member
    Reputation:
    Join Date
    Oct 2015
    Posts
    132
    It's fine for xc or average trail/AM riding. If you are hitting some serious jumps and drop offs you should man up and get the correct bike.

    Or get an on one evo456 HT like I did and use 100 to 160mm. Steel is real.
    Last edited by Ernest72; 03-20-2016 at 05:50 PM.

  27. #27
    mtbr member
    Reputation:
    Join Date
    Mar 2010
    Posts
    97


    New frames are great but upgrading an old bike can be just as good.
    Been rocking this 97 trek 6500 since... well... 1997.

    Stock it came with an RS Indy C, 80mm elastomer, if memory serves.

    Next it was the 2001 RS Judy SL, 100mm, Coil, w heavy springs.

    After that it was the 2006 RS Revalation 426, u-turn 85-135mm, coil w heavy spring. (pictured, kept it at 135 full time)

    Now I'm running a 2012 RS Revalation RLT TI, Air, 120-150mm (pretty much keep it in 120 unless there is no climbing in sight)


    Stock my head angle was 70deg. Today w/120mm travel its about 67deg and My wheelbase is longer.. Both of these are hallmarks of modern trail geometry.

    If I want to get picky, my bottom bracket sits a hair higher as well as my stand-over height, but that's about it. The bike handles pretty much like it always did. Once you're into sag and deeper travel the geometries aren't that far out of original spec anyway, and the ride is a lot better.

    I'm a 200lb rider and have bashed this frame on a variety of long travel forks for nearly 20 years... You'll be fine.

  28. #28
    mtbr member
    Reputation:
    Join Date
    Mar 2010
    Posts
    97
    From the original 96 trek technical manual:

    "Suspension Ready Geometry· The entire ABT mountain bike line is suspension ready, but with a slightly different fork length specification than the Trek 830 and 850. This is because the ABT mountain bikes are designed to accommodate longer travel forks like Rock Shox Quadras, Manitou Mach 5s, or air/oil forks with an axle-to-fork crown race seat dimension around 408 mm. Some longer forks, like Rock Shox Judy XC or SL, will also ride very well in these bikes."


    Though they specify their original design spec for suspension forks, 408mm, designers were fully expecting users to install longer travel forks than what was shipping at the time.

    At least for my frame, a 96/97 "ABT" Trek, I know I'm good running a long travel fork.


    Go long.

  29. #29
    inner peace to make peace
    Reputation: TrailNut's Avatar
    Join Date
    Apr 2004
    Posts
    2,292
    I have installed a 130MM Marzochi Z1 FR ETA on my Kona Lavadome CrMo HT that had as OEM R.S. Indy S 50MM fork (that had no real damping), over ten years ago. I still have all my teeth. I did break the frame at the starboard chain stay and had it weld repaired. I also alternate with a Kona ridged fork and a 100MM Marzochi, coil and oil, fork since 100MM travel handles faster on twisty single tracks, but the 130MM travel is more fun on fast fire roads: The travel reducer ETA gets used on steeper climbs.

    Now, I am again tempted to try a 130MM fork, that has a travel reducer Launch Control, for my carbon 105MM FS bike. I would keep the OEM 100MM fork for racing.
    “Everyday is a good day,” from the Blue Cliff Records, Yun-men (864-949 AD).

  30. #30
    mtbr member
    Reputation:
    Join Date
    May 2015
    Posts
    45
    I'm just going to add my experience for those researching this topic. I have a 100mm travel full suspension bike, and I went to a 95-120 Fox Terrlogic fork. It was fine. But then I got a Fox 130-160mm fork, and I loved it! It felt so good! I run it at 160mm all the time.

    The changes of lifting the front include a slacker head angle (good for going down a hill, potentially not as good for climbing) and a higher bottom bracket (less pedal strikes because bottom brackets seem to be so low these days).

    I did this 5 years ago. My head tube did not break off. Now I'm searching this topic now because I'm considering using that same 95-120 fork on another frame designed for a 100mm fork. I also just happen to have a 140mm Fox fork, which feels much better to me. I'm debating whether to put the 95-120 on it or the 140. 40mm is just 1.6 inches. The bottom bracket would only go up half of that max. I don't think I'm going to notice a 0.75 inch height difference.

  31. #31
    mtbr member
    Reputation: mr_manny's Avatar
    Join Date
    May 2016
    Posts
    455
    Here's a good site to play with frame geometry changes.

    Frame Geo Calc

    This calculator also allows you to experiment with angle headset changes, and it's affects on your frame.

    If your not familiar with your Frame Geo, the following site might help.

    Geometry Geeks
    Ride, Enjoy...Repeat.

  32. #32
    mtbr member
    Reputation: One Pivot's Avatar
    Join Date
    Nov 2009
    Posts
    9,448
    Ahh, the good old days when everyone swore 40mm would snap your bike in half!

    The easy math is 1 degree per 20mm. This applies to the seat tube too, and it shortens your reach. Over forking a bike basically turns it into old-school 26er geometry with the slack seat tube and sloppy handling. The hta is most often talked about, but the sta slackening, and bb raising is a bigger deal.

  33. #33
    mtbr member
    Reputation:
    Join Date
    Jun 2013
    Posts
    310
    I had a SC 5010 v1 designed for 130mm fork. I swapped out the noodle Fox Float 32 for a Pike 130/160. 160mm was great on the downhill, but really sucked on climbs. For those runs that are predominantly downhill, but have climbing sections, I got real good at reaching down on the move to flip it back and forth. After a few years I got tried of having to fiddle and just want a newer bike, so went to a fixed 150mm (Yeti SB5.5). Doubt I'll go with a dual position fork again.

  34. #34
    inner peace to make peace
    Reputation: TrailNut's Avatar
    Join Date
    Apr 2004
    Posts
    2,292

    Cool-blue Rhythm

    Quote Originally Posted by FluorescentPinkPanda View Post
    I'm just going to add my experience for those researching this topic. I have a 100mm travel full suspension bike, and I went to a 95-120 Fox Terrlogic fork. It was fine. But then I got a Fox 130-160mm fork, and I loved it! It felt so good! I run it at 160mm all the time.

    The changes of lifting the front include a slacker head angle (good for going down a hill, potentially not as good for climbing) and a higher bottom bracket (less pedal strikes because bottom brackets seem to be so low these days).

    I did this 5 years ago. My head tube did not break off. Now I'm searching this topic now because I'm considering using that same 95-120 fork on another frame designed for a 100mm fork. I also just happen to have a 140mm Fox fork, which feels much better to me. I'm debating whether to put the 95-120 on it or the 140. 40mm is just 1.6 inches. The bottom bracket would only go up half of that max. I don't think I'm going to notice a 0.75 inch height difference.
    Try the 140MM.

    I've got two forks (120MM installed and 140MM as backup, inhibits on steep climbs) for my SC Blur XCc 105MM frame, designed for 100~120MM forks,
    and have three forks for my steel hardtail (rigid, 100MM, and 130MM installed).

    I've been over forking my MTBs since the last Century and I still have all my teeth. Only frame I broke was on the drive side chain stay on a steel HT.
    “Everyday is a good day,” from the Blue Cliff Records, Yun-men (864-949 AD).

THE SITE

ABOUT MTBR

VISIT US AT

© Copyright 2020 VerticalScope Inc. All rights reserved.