Advertise on Bikeforums.net



User Tag List

Results 1 to 11 of 11
  1. #1
    Newbie
    Join Date
    Jan 2010
    Posts
    3
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    custom geometry -- any problems?

    Hi,

    Long time stalker here. Can't decide if I'm going to try and build the below design myself (steel) or find someone to build it (ti), but I was wondering if you all could take a look at it and see if there are any problems wrt the geometry that I should be worried about. I think that stack and reach are tentatively OK, since it's on par with bikes that fit me well, but i'm worried about handling. FYI -- I'm a 5'4 female with a longer inseam and shorter torso.

    ps- the seat tube is 50.3 c-c, i think rattlecad is doing c-t. thanks!

    custom geo.jpg

  2. #2
    Randomhead
    Join Date
    Aug 2008
    Location
    Happy Valley, Pennsylvania
    Posts
    12,503
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    what tires are those, 700C by 23?

    If they are, I think you should go with longer chainstays

  3. #3
    Old fart JohnDThompson's Avatar
    Join Date
    Nov 2004
    Location
    Appleton WI
    My Bikes
    Several, mostly not name brands.
    Posts
    12,524
    Mentioned
    8 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by unterhausen View Post
    what tires are those, 700C by 23?

    If they are, I think you should go with longer chainstays
    Agreed. You'll have awfully tight clearance at the seat tube otherwise.

  4. #4
    Andrew R Stewart Andrew R Stewart's Avatar
    Join Date
    Feb 2012
    Location
    Rochester, NY
    My Bikes
    Stewart S&S coupled sport tourer, Stewart Sunday light, Stewart Commuting, Stewart Touring, Co Motion Tandem, Stewart 3-Spd, Stewart Track, Fuji Finest, Raleigh Pro, Trek Cycle Cross, Mongoose tomac ATB, GT Bravado ATB, JCP Folder
    Posts
    3,123
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    The other aspect that i picked up on is the possibility of toe overlap. The front center being only 578mm with 172.5 cranks. If you go to larger tires and/or have large feet and/or use a rearward set cleat that possibility is a real one. Whether toe/tire strike is a concern of yours is your to decide on.

    I also agree with the CS length being fairly short.

    If you go to a TI builder i suggest a full fit up by him/her and listen to the results. Andy.

  5. #5
    Member
    Join Date
    Aug 2012
    Location
    Seattle
    My Bikes
    753 Rivendell, Davidson Ti Disc Road, Scott carbon 29er, Tomasso w/ SR, Moulton F frame, Cannondale MTB Tandem, Baron Road Disc, Trek Madone Proj 1, Rock Lobster Euro CX steel
    Posts
    27
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Would a fork with more offset help the toe overlap thing? 62mm of trail seems like plenty and adding some offset might be enough to get to 50mm trail and add 10-12mm to the toe overlap buffer. I'm not sure how that will play with 70.5* HT angle though.

  6. #6
    coprolite fietsbob's Avatar
    Join Date
    Jun 2010
    Location
    NW,Oregon Coast
    My Bikes
    7
    Posts
    40,172
    Mentioned
    28 Post(s)
    Tagged
    0 Thread(s)
    maybe a curved seat tube to make more rear tire clearance?

    Jack Taylor did that decades ago ..


    there is the Ms.Terry solution , use a 600 wheel rather than a 700 up front.

    or 2_600 wheels , and a bit less BB drop ..
    Last edited by fietsbob; 03-24-14 at 10:30 AM.

  7. #7
    Old fart JohnDThompson's Avatar
    Join Date
    Nov 2004
    Location
    Appleton WI
    My Bikes
    Several, mostly not name brands.
    Posts
    12,524
    Mentioned
    8 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by fietsbob View Post
    maybe a curved seat tube to make more rear tire clearance? there is the Ms.Terry solution , use a 600 wheel rather than a 700 up front. or 2_600 wheels , and a bit less BB drop ..
    Or rear-loading track dropouts. And shorter crank arms for the pedal overlap.

  8. #8
    coprolite fietsbob's Avatar
    Join Date
    Jun 2010
    Location
    NW,Oregon Coast
    My Bikes
    7
    Posts
    40,172
    Mentioned
    28 Post(s)
    Tagged
    0 Thread(s)
    short chainstays required? seen dents pressed in the back of straight seat tubes ,
    and then there was the RiGi solution, split the seat tube in to 2 tubes so the wheel passed between them ..

  9. #9
    Senior Member
    Join Date
    Nov 2010
    Location
    River City, OR
    Posts
    570
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    Other than the drawing having too many dimensions... enough to confuse me and make my old eyes tired. LOL

    One dimension I have concern about is BB to saddle height. At that length it would be appropriate for someone with an inseam of 32.5-33" I know you're a long legged short lady but... Ladies tend to run that way and sometimes making a frame fit is just little more work.

    I also question the HTA. It's slack to make for a shorter TT to fit your short torso? Of course, any steeper would also reduce FC.

    172.5 cranks? Depending on what characteristic makes your legs "long," this crank length may not be appropriate.


    I like the others think the CS is a bit short. You didn't mention the purpose of this bike (geared or not) but if the axle slot isn't totally vertical, or the wheel loads from the rear (as is SS or track drops) you may have trouble loading an inflated tire/wheel.


    Don't know where you got your fit dimensions but I'd suggest you try elsewhere, and get at least another opinion. I've had good luck using the "fitting" calculator over at Strawberry's site. Strawberry Cyclesport Handcrafted Bicycle Frames

    And, like others have said- if you're having the frame built by someone else, let them do the math and be receptive to their input. Ain't nothing worse than spending big bucks on a custom frame and it don't fit!

  10. #10
    Senior Member
    Join Date
    Jul 2011
    Posts
    1,447
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Is this another one of those I am having my frame built in china threads? I get suspicious when I hear someone say they don't know how to design a frame they are planing on either building themselves, or "having built in Ti".

  11. #11
    Senior Member ftwelder's Avatar
    Join Date
    Apr 2010
    Location
    vermont
    My Bikes
    Many
    Posts
    3,093
    Mentioned
    7 Post(s)
    Tagged
    1 Thread(s)
    It's like an idea bomb just exploded in my face. What size tires are you planning to use? Is this for dirt or pave?
    1886 Surrey machinists Invincible, 1900 Nashua, 1937 Raleigh Golden Arrow, 1938 Raleigh Silver Record, 1951 Armstrong tourmalet, 1970 Motobecane Grand Record, 1971 Raleigh Professional, 1971 Gitane TDF, 1972 Legnano Gran Primio, 1973, Peugeot PX-10, 1975 Roberts, 1984 Battaglin Giro, 1985 Grandis Speciale, 2012 FTW

    frankthewelder@comcast.net

    le prix s'oublie,la qualité reste ,(michel audiard)

Posting Permissions

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