Advertise on Bikeforums.net



User Tag List

Results 1 to 18 of 18
  1. #1
    B17
    B17 is offline
    Senior Member
    Join Date
    Apr 2005
    Posts
    282
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    Threaded headset and fork question- How low should the threads go?

    I have a lugged CX/all-rounder frame on the way, will be replacing the 1" threaded unicrown fork with a lugged one (also threaded, same length & rake, no probs) to match the lugged frame. Seller lists head tube as being 105mm. Fork comes in three different steerer tube lengths- 145mm, 165mm and 185mm. Each has a thread length of about 42mm. I'd like to get the 165 and use 2cm or so of spacers, but I'm not sure the threads go low enough on the steerer tube to allow the headset to be installed.

    165mm (total steerer length) - 42mm (thereaded portion) = 123mm.

    Head tube, again, is 105mm.

    So, 123mm (unthreaded portion of steerer) - 105mm (head tube length) = 18mm

    If I install a standard 1" threaded headset, say from Tange or Shimano or Campy (fork crown is 26.4) will I run out of thread before the upper cup secures the upper bearings?

    Thanks so much to anyone who can provide even a little help.

  2. #2
    Senior Member
    Join Date
    Mar 2008
    Posts
    4,337
    Mentioned
    3 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by B17 View Post
    .. I'd like to get the 165 and use 2cm or so of spacers
    Spacers, particularly at that height, are a thing of threadless forks & headsets. I don't think I've ever seen such a spacer stack on a threaded fork. Maybe 2-4 mm worth of washers to allow for future headset replacements.

    Also, while you can fit spacers between top race and lockring, the top race has to thread all the way down to the head tube.
    Will crown race + bearing balls + lower cup + upper cup + bearing balls really eat up 18 mm?
    Last edited by dabac; 07-10-12 at 02:29 AM.

  3. #3
    Senior Member
    Join Date
    Apr 2006
    Posts
    1,024
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    I am no professional bike mechanic but I think that you are going to have to go with the 145 mm tube because you will not be able to get the upper bearing race to screw down far enough with the 165 mm tube and only 42 mm of threads.

  4. #4
    Mechanic/Tourist
    Join Date
    Apr 2007
    Location
    Syracuse, NY
    My Bikes
    2008 Novara Randonee - love it. Would have more bikes if I had time to ride them all. Previous bikes: 1968 Motobecane Mirage, 1972 Moto Grand Jubilee (my fav), Jackson Rake 16, 1983 C'dale ST500.
    Posts
    5,312
    Mentioned
    7 Post(s)
    Tagged
    0 Thread(s)
    You probably can't use the 165 because although the headset will take up about 37 - 45 mm (stack height) the top race must be able to screw down sufficiently. There's no way we can tell you for sure - why don't you just measure the amount of threads used on your current setup? If you have a good 5mm of leeway with the 165 then it technically should work.

    That being said, the 145 is a much better fit - depending on the headset you choose you may not need to cut the fork at all. It is not a good idea to raise the fork that much unless you have determined that will work properly for you as far as fit. It's best to adjust fit horizontally before going higher in front, as that changes weight distribution more than it does reach.
    Last edited by cny-bikeman; 07-10-12 at 08:14 AM.

  5. #5
    Senior Member Grand Bois's Avatar
    Join Date
    Mar 2005
    Location
    Pinole, CA, USA
    Posts
    15,443
    Mentioned
    15 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by dabac View Post
    Spacers, particularly at that height, are a thing of threadless forks & headsets. I don't think I've ever seen such a spacer stack on a threaded fork. Maybe 2-4 mm worth of washers to allow for future headset replacements.
    Now you have. It's not so unusual. You can see more on the Rivendell site. It gives extra support to tall stems when the goal is to get the bars up higher.

    Last edited by Grand Bois; 07-10-12 at 08:36 AM.

  6. #6
    Senior Member
    Join Date
    Apr 2009
    Location
    New Rochelle, NY
    My Bikes
    too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter
    Posts
    22,140
    Mentioned
    60 Post(s)
    Tagged
    1 Thread(s)
    There's just about zero benefit to using spacers on a threaded headset. Obviously the threads have to extend beyond the headset so the threaded upper cup can fit. That means you need about 1" of thread below the top nut of a typical headset. But there's a second requirement, and that's that the stem extend into the fork beyond the threaded section of the fork because the depth of thread is roughly half the wall, and the steerer needs the stem to carry stresses below this weakened area. How far beyond the thread is necessary is hard to say, but figure 1/2" at a minimum and up to an inch desirable (more than that won't help).

    So if you measure the fork very carefully and have the thread end just below the upper race, you might be able to add 1/2" of spacers under the locknut, but that's about it. If you need more height than a typical quill stem affords, you have a few choices.

    1- use a stem with an obtuse angle so the forward extension rises gaining you more height.
    2- use one of those "tall boy" stems - though, IMO, they tend to be pretty crappy.
    3- if you're buying a new fork anyway, go threadless which will afford some more choices, and the ability to add up to 2" of spacers, but don't forget that this won't net you much because you lose the 2-3" of height that a quill stem has above the headset. One nice thing about the threadless option, is that there's a nicer selection of quality rising stems (any mounted with the smaller angle on top.

    Before spending any dough, take the time to figure what you're trying to achieve (desired handlebar height) and use this stem calculator to see how the various options play out.
    FB
    Chain-L site

    An ounce of diagnosis is worth a pound of cure.

    “Never argue with an idiot. He will only bring you down to his level and beat you with experience.”, George Carlin

    “One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN

    WARNING, I'm from New York. Thin skinned people should maintain safe distance.

  7. #7
    Senior Member
    Join Date
    Apr 2009
    Location
    New Rochelle, NY
    My Bikes
    too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter
    Posts
    22,140
    Mentioned
    60 Post(s)
    Tagged
    1 Thread(s)
    Quote Originally Posted by Grand Bois View Post
    Now you have. It's not so unusual. You can see more on the Rivendell site. It gives extra support to tall stems when the goal is to get the bars up higher.

    This is a potentially dangerous arrangement. The spacers may improve rigidity for the stem, but do nothing for the fork. They also distort the minimum insertion calculus, making it possible to fool yourself into believing the stem is deep enough when it isn't.

    For the system to be sound, the bottom of the stem must extend beyond the lowest thread in the steerer by 1/2-1" to avoid breaking the steerer. Plus with the added leverage, it's important that the stem extend well below the upper bearing, otherwise the steerer becomes a cantilever structure, something it isn't designed to be.

    Of course it's possible that this particular bike meets all the conditions, but it's impossible to tell from the photo, and if the stem is only inserted to the 2-1/2" minimum insertion mark, it probably doesn't.
    FB
    Chain-L site

    An ounce of diagnosis is worth a pound of cure.

    “Never argue with an idiot. He will only bring you down to his level and beat you with experience.”, George Carlin

    “One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN

    WARNING, I'm from New York. Thin skinned people should maintain safe distance.

  8. #8
    Senior Member
    Join Date
    Mar 2008
    Posts
    4,337
    Mentioned
    3 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by Grand Bois View Post
    Now you have. It's not so unusual.
    Now, to me that setup is just plain ol' ugly. I can sort of abide with the huge shiny lump making up the top half of the headset. But such a tall upwards part of the stem, and then a forwards protrusion that's horizontal at best.
    It's like they've put extra effort into putting a sharp angle pointing directly towards the rider's crotch/abdomen - for no practical gain.

    But what to expect from a bike featuring a utility-oriented front basket but w/o fenders....

    Nice cork grips though.

  9. #9
    Senior Member Grand Bois's Avatar
    Join Date
    Mar 2005
    Location
    Pinole, CA, USA
    Posts
    15,443
    Mentioned
    15 Post(s)
    Tagged
    0 Thread(s)
    That stem is very long and it's inserted deeply. It's a fillet brazed city bike stem from Belgium. I don't feel threatened by that "sharp angle".

    No, spacers don't reinforce the fork steer tube. What a ridiculous thing to say! The extended steer tube does reinforce the stem, though. I'm sorry you don't like the bike. Fortunately, you don't have to ride it.

    There is no room for fenders, but I don't need them. It rarely rains here. Some of my bikes have fenders, but they're just for looks. When it does rain, the 39 year old bike stays home. I built it for trips to the farmers market.


  10. #10
    Senior Member
    Join Date
    Apr 2009
    Location
    New Rochelle, NY
    My Bikes
    too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter
    Posts
    22,140
    Mentioned
    60 Post(s)
    Tagged
    1 Thread(s)
    Quote Originally Posted by Grand Bois View Post
    That stem is very long and it's inserted deeply.
    That's the key. As long as it's going 1" or more below the upper headset bearing, and beyond any threads, (whichever is deeper) it's mechanically sound.

    After that the only thing that matters is that you're happy with it.
    FB
    Chain-L site

    An ounce of diagnosis is worth a pound of cure.

    “Never argue with an idiot. He will only bring you down to his level and beat you with experience.”, George Carlin

    “One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN

    WARNING, I'm from New York. Thin skinned people should maintain safe distance.

  11. #11
    Senior Member
    Join Date
    May 2011
    Location
    Upstate NY
    My Bikes
    Bianchi San Mateo and a few others
    Posts
    718
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by Grand Bois View Post
    There is no room for fenders, but I don't need them. It rarely rains here.
    I grew up in your neck o' the woods. I used to take the top off my Jeep in April and put it back on in October or so, and I don't recall the interior ever getting rained on.

  12. #12
    Senior Member
    Join Date
    Dec 2009
    Posts
    771
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by Grand Bois View Post
    Now you have. It's not so unusual. You can see more on the Rivendell site. It gives extra support to tall stems when the goal is to get the bars up higher.

    The only thing that could make that set-up cooler, is if it was a lugged stem.
    I like the high bars thing, which is exactly why I just bought a Rivendell Bleriot.
    BTW, how id you mount the bell right up against the headset like that? That's what I wanna do, but don't know how.

  13. #13
    coprolite fietsbob's Avatar
    Join Date
    Jun 2010
    Location
    NW,Oregon Coast
    My Bikes
    7
    Posts
    2,541
    Mentioned
    41 Post(s)
    Tagged
    0 Thread(s)
    Bike Shop may have a steerer tube thread cutting die, to cut the threads further down.

  14. #14
    Senior Member VeloBrox's Avatar
    Join Date
    May 2011
    Location
    Oslo, Norway
    My Bikes
    1951 Armand Carlsen, 1969 DBS Deluxe, 1949 Diamant, 1978 DBS Winner Tandem, 1955 Herkules... to infinity and beyond!
    Posts
    378
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by lungimsam View Post
    The only thing that could make that set-up cooler, is if it was a lugged stem.
    I like the high bars thing, which is exactly why I just bought a Rivendell Bleriot.
    BTW, how id you mount the bell right up against the headset like that? That's what I wanna do, but don't know how.
    One of the headtube spacers is probably tapped for the bell to screw into. Elegant solution.
    Last edited by VeloBrox; 07-11-12 at 09:16 PM.
    -------------------------------------------------------------------------------
    1986 Peugeot PY10M
    1983 Trek 620
    1980 Peugeot PY10S (everyone needs two of these)
    1961 Monark 90320
    1953 Crescent modell nr. 11
    1942 Diamant modell nr. 11
    ...and a basement full of unrideable old stuff.

  15. #15
    B17
    B17 is offline
    Senior Member
    Join Date
    Apr 2005
    Posts
    282
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Okay, frame arrived last week and fork got here this morning. The original fork's steerer tube is only 139mm, so I went with the 145mm steerer on the new fork instead of the 165 I was considering. I was hoping against hope that the crown race on the stock headset would be a match for the new fork's crown, but it isn't. The old crown race drops onto the new crown and is very loose. That means the old race is 27.0mm JIS and the new fork crown is 26.4mm ISO. Now I have anorther problem. I'm willing to buy a new headset (the stock one is a bit... unrefined), but I have no way of knowing whether the head tube of my frame (early 90s lugged Bianchi Advantage hybrid) accepts 30.0mm JIS cups or 30.2mm ISO cups. That's a measurement I don't trust my LBS to get 100% right.

    I'd rather not try the pop-can shim. Should I:

    1) try to find a 26.4 crown that looks like the one on my old headset? How close must the crown be to the old one? The headset itself is a very simple steel job, upper and lower bearings are identical, 16 bearings per cage.

    2) Buy a JIS headset from a company that makes indentical JIS and ISO headsets, try to press-fit the cups into the headtube (if they go in easily, it should mean that the headtube is 30.2 and so I can just go and buy the ISO headset of my choice). If they don't go in easily, then the headtube is 30.0mm and I need to buy a 26.4 crown from a matching ISO headset.

  16. #16
    Old fart JohnDThompson's Avatar
    Join Date
    Nov 2004
    Location
    Appleton WI
    My Bikes
    Several, mostly not name brands.
    Posts
    12,999
    Mentioned
    11 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by B17 View Post
    Should I:

    1) try to find a 26.4 crown that looks like the one on my old headset? How close must the crown be to the old one? The headset itself is a very simple steel job, upper and lower bearings are identical, 16 bearings per cage.

    2) Buy a JIS headset from a company that makes indentical JIS and ISO headsets, try to press-fit the cups into the headtube (if they go in easily, it should mean that the headtube is 30.2 and so I can just go and buy the ISO headset of my choice). If they don't go in easily, then the headtube is 30.0mm and I need to buy a 26.4 crown from a matching ISO headset.
    Just get a new ISO headset with the appropriate stack height (you haven't trimmed the fork yet, have you?), mill the head tube to ISO dimensions and install the new headset.

  17. #17
    B17
    B17 is offline
    Senior Member
    Join Date
    Apr 2005
    Posts
    282
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by JohnDThompson View Post
    Just get a new ISO headset with the appropriate stack height (you haven't trimmed the fork yet, have you?), mill the head tube to ISO dimensions and install the new headset.
    No, haven't trimmed the fork, don't plan to. I need to add a cable hanger in there somewhere anyhow, which will take up about 3-4mm. Is this milling an expensive idea?

  18. #18
    Old fart JohnDThompson's Avatar
    Join Date
    Nov 2004
    Location
    Appleton WI
    My Bikes
    Several, mostly not name brands.
    Posts
    12,999
    Mentioned
    11 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by B17 View Post
    No, haven't trimmed the fork, don't plan to. I need to add a cable hanger in there somewhere anyhow, which will take up about 3-4mm. Is this milling an expensive idea?
    Probably about $20 to do just the head tube. Maybe a few bucks more if you have them install the headset. If you buy the headset from the shop, they may be inclined to give you a bit of a discount.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •