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Conference noted::bicycle

Title: Bicycling
Notice:Bicycling for Fun
Moderator:JAMIN::WASSER
Created:Mon Apr 14 1986
Last Modified:Fri Jun 06 1997
Last Successful Update:Fri Jun 06 1997
Number of topics:3214
Total number of notes:31946

1059.0. "Bike Frame Size?" by JOKUR::WHEELER (Ken) Wed Mar 22 1989 12:46

    
    
    
    I am in the market for buying a bicycle.....
    
    I'm 6'1" with a 34" inseam.....I was told that I would probably
    need a 28" bike frame
    
    I was curious if say, I was able to buy a 26" frame....Does the
    2" makes a big difference?
    
    Thanks
    
    
    Ken Wheeler
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1059.1check out the fit kitUSCTR1::PJOHNSONWed Mar 22 1989 12:504
    A two inch difference in frame size makes a BIG difference.  Ask
    about a fit kit to get you in the right ball park.
    
    Phil
1059.2TALLIS::JBELLCeci n'est pas une pipe. |Wed Mar 22 1989 13:2511
>    I'm 6'1" with a 34" inseam.....I was told that I would probably
>    need a 28" bike frame

    28 inches is HUGE.  The largest mass production frames are 27".

    I'm 6'2 with a 33" inseam.  My bike is 25" BB center to top.

    (I know you can't infer frame size from one person to another,
    but it can't be that far off.)

    -Jeff
1059.3AMUN::CRITZA noid is annoyedWed Mar 22 1989 13:329
    	I'm 6'6" with a 36 inch inseam. According to a Fit Kit
    	done by Paul Randazzo, I need a 25 1/4 inch frame, more
    	or less (I don't remember specifically; I do have the
    	correct frame size, though.)
    
    	If your dealer does not know about or use the Fit Kit,
    	find another dealer.
    
    	Scott (Someone is being taken for a HUGE ride0
1059.4A 28' FRAME WILL HURT YOUR PRIVATE PARTSAKOV11::FULLERWed Mar 22 1989 14:015
    You will probably end up with a desired size of 23.5 to 24.5 depending
    upon make.  A 58 cm frame center to center is 23.22".  I am 6'0"
    with about a 33" inseam and ride this size frame.  
    
    steve
1059.5MEMORY::GOODWINin a spasm of lucidity...Wed Mar 22 1989 17:4617
    There is no substitute for the fit kit but a quick way to approximate
    the frame size is to take your inseam and subtract 10.5". This can
    be derived by:
    
    	Take your inseam.
    	add 2" (distance from cuff to floor).
    	subtract 1" for clearance over toptube when standing.
    	subtract 1" for difference in seat tube do to seat angle.
    	subtract 10.5" for bottom bracket height.
    

    Still having a good bike shop size a bike for you with a fit kit
    is still the best thing to do.
    
    Paul    

    
1059.6Mountain Bike Frame SizeKRYPTN::MOLLINFri Mar 24 1989 18:146
    My son is 6'2" and wants to get  a mountain bike to ride in Boston.
    He goes to Northeastern. I don't know anything about the correct
    frame size for mountain bikes. What guidelines should we use to
    determine correct size?
    
    Dick
1059.7How about a 63 cm ?ICBB::JSMITHI Bike Solo IIFri Mar 24 1989 20:3911
    re. .6
    
    	Oh NO !  Not another 6 footer!
    
    	For a sizing discussion and possibly a good lead on 
    	a road bike see note 1062.
    
    	If your interested in trying a mountain bike on for size
    	before you buy see 584.3.
    
    					Jerry
1059.8What's in a frame sizeJUMBLY::VAL_KKassessinoff, now you know a foreign languageThu Apr 06 1989 10:2631
    None of these comment (nor the ones in note 1062) are ALL the story.
    There is a great deal more to be considered if (and only if) you are
    after greatest comfort rather that most efficient posture for compe-
    tative cycling.
    
    The man who suggested subtracting 10.5 inches from your measurement
    is fundamentally right. That's the best starting point. HOWEVER!
    
    I have a painful neck and can't ride with my torso in the horizontal
    and my head thrown back to see ahead. So I ride a size 2.5 inches too
    small and extend the seat pin to about 6 inches. This makes up for the
    distance to the pedals, and allows me to sit more vertically. I have
    also changed my front handlebar stem to one with no forward throw at
    all. Again, my arms are thus closer to the saddle position, with the
    same result. I know of riders with other back-problems who do the
    similar tricks.
    
    The main point to remember is that the seat-tube size also affects the
    rest of the frame dimensions. BUT these dimensions can also be altered
    by the geometry of the frame. The geometry of the frame is altered by
    changing the angles, so that the length of the horizontal can be
    shortened or lengthened. The angle also affects the responsiveness of
    the bicycle. It could become quite hard to steer. You see what I meant
    when I said it's not the whole story. There are so many variables that
    contribute to a comfortable posture, that I have NEVER heard of anyone
    who has been lucky enough to buy the right byke first time. Most have
    three goes. Some manage it the second time round.
    
    Good luck, you'll need it.
    Val.
    
1059.9ICBB::JSMITHI Bike Solo IIThu Apr 06 1989 11:588
    	Note 1068 should give you an idea of the road bike
    frame sizes used by other noters in this conference.
    Again, only to be used as a guide, not a replacement 
    for a fit kit.  Many, many people have commented on
    Top Tube Length as being a more important variable and
    this is what Val is refering to with changing the frames
    geometry.
    					Jerry
1059.100 mm. stem??ULTRA::WITTENBERGSecure Systems for Insecure PeopleThu Apr 06 1989 17:349
Re: .8

    Where do  you  get a stem with no forward throw? The shortest I've
    been  able  to  find  is  40 mm. Even that's a bit too long for my
    girlfriend,  so  I'm  looking  for something shorter. I've thought
    about  turning  the  stem  to point backwards, but I'm afraid that
    that would make the bike unstable.

--David
1059.11I've seen it doneTALLIS::JBELLCeci n'est pas une pipe. |Thu Apr 06 1989 17:4614
>   .... I've thought about  turning  the  stem  to point backwards,
>   but I'm afraid that that would make the bike unstable.
>   --David

    I've seen pictures in books of this.  I think it was The Complete Book
    of Bicycle Commuting by John Allen.

    I don't think that it would change the stability that much.
    How much does it change the stability to move your hands from the
    corner of the handlebars to the brake hoods?  (Most of the change
    is due to your body changing position.)

    -Jeff Bell

1059.12DON'T EVEN TRY TO FIND SUCH A SHORT STEMAKOV11::FULLERThu Apr 06 1989 18:4116
    re:1059.10
    
    Even if you could get a 0mm stem, it would not be optimal if she
    wishes to ride a lot.  Her weight would not be distributed properly
    giving overall less control.  There are many frames on the market
    with shorter top tubes, sell the frame she's got and get a Terry
    or have something made.  It may cost you, but it may make the
    difference between keeping a great sport or dropping altogether.
    (I got my wife, girlfriend at the time, a new frame and components
    and it certainly paid off in our relationship by riding together
    more)
    
    Note: don't look at newer mountain bikes even if the frame are smaller.
    Industry is lengthen the top tubes for weight distribution.
    
    steve
1059.13Turning the stem could lead to problems!CIMAMT::CHINNASWAMYOH Bother!Mon Apr 10 1989 12:1930
I would not turn the stem around. I havn't done the technical theory
into this but, I believe it would make the bike much more dangerous.
Imagine if she were riding and used one of her hands to grab her
water bottle. Now she has only one hand on the bars. If the front wheel
were to hit a bump and cause her to loose her grip slightly, she would
still be pushing the bar forward with the one hand she has on the bars.
If the stem were normal then she could push the bar a little before the
geometry of the setup would limit it. After you push it so far that side
of the bar would have to come back toward you to turn it any more. Her
forward weight would limit that. Now if the stem were turned around, she
could end up swinging the bars so that they were parallel with the top
tube. The front fork rake would still try to limit this but her forward
weight on the bars may overpower the saftey benefits of this. I guess a
good test would be to look at the position on the bars where you would 
normally place your hands. Now swing the bars left and right and look at 
the arc this position makes. The farthest forward this arc is from your
bike will be the limiting swing position. To make the bars turn more, you
would have to actually pull them back toward you. Try this test again with
your stem turned around and see where the farthest point is with respect
to the amount your handle bars are turned. I would think that they would
turn almost 90 degrees.  

All this is just an isolation of her weight with respect to the turning
force required. Many other factors such as fork rake, front tube angle,
stability of the bike come into play. However, I feel that turning her
stem around would make the bike more dangerous and more susceptible (sp?) to
that one incidence which could lead to a nasty fall.

Mano

1059.14In a word...ULTRA::BURGESSMon Apr 10 1989 13:517
re  < Note 1059.13 by CIMAMT::CHINNASWAMY "OH Bother!" >
>                 -< Turning the stem could lead to problems! >-

	TRANSLATION:	Astable.

	R

1059.15How to measure frame size..ALFA2::PEASLEETue Jun 14 1994 14:206
    Since this is a bike frame note, could someone tell me how I would
    measure a mountain bike to determine the frame size.  I am sure there
    is a note in here somewhere....I just can't seem to find it.
    
    Thanks,
    Nancy
1059.16PAKORA::GGOODMANLoonaticTue Jun 14 1994 17:426
    
    In the UK, it is from the centre of the BB to the centre of the bolt
    that holds the seat pin in place. However, it can be measured different
    ways in different countries.
    
    Graham.
1059.17JURA::MACFADYENsmile and mean itFri Jun 17 1994 08:356
Re .16:  Doesn't that only apply to a conventional frame with a
horizontal top tube? You know what mountain bikes are like...
anything but conventional.


Rod
1059.18Center to Center or TopSTRATA::HUIFri Jun 17 1994 12:4517
      
Re .17

Depending on the MFG. Most Mountain bike still measure Center to Center even on
sloping tube (Samll frames). The critical part of a mountain bike is the
overall standover height. 

On a typical road bike, the stand over height changes pretty close to the
change in frame size. This of course also depends on the seat tube angle. 
In a Slope tube Mountain bike frame however, a 16 inch frame to a 14 inch 
frame might only reduce the stand over height about 1 inch instead of 2 inches.

However, Cannondale Delta V frames and probably several other vendors are not
effected by this because of there frame design.

Dave

1059.19TOP TUBE LENGTH MORE IMPORTANTSTOWOA::SWFULLERFri Jun 17 1994 13:027
    Mountain bike sizing is slowly becoming top tube length's not seat
    tube.  For example, in the upper line of Cannondale, a 17" and 19"
    were measured, same seat tube length, the top tube is what was
    different.  In addiition, BB height varies a lot as well as sloping
    top tube.  End result, ride the bike and find one that is comfortable.
    
    steve