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53/54 vs 55/56 which size must I go for?(10 posts)

53/54 vs 55/56 which size must I go for?Thierry
Jul 15, 2001 1:55 PM
Hello, I am about to buy a road bike and I am really puzzled with what should be the right size for me. I have tried several bikes, 53 and 55 Lemond's or Bianchi's, 54 and 56 in other geometries like Trek, Specialized or Cannondale, and even compact frames like Giant or Schwinn in large and medium. The best fit seems to be 53 in Lemond, or 55 in Bianchi and large in Schwinn. I feel a little bit streched on the 55 Lemond and 56 in traditional frame geometry. I don't want to buy a frame that will feel to small nor one that will be too big. Anyone can help with recommendations? Thanks a lot!
how can we help without inseam and height????C-40
Jul 15, 2001 3:35 PM
You have to gives us experts something to go by.

The frames you have looked at are in my size range. I'm 5'-7" with a long 32-5/8 inch inseam. The genral formula for vertical frame size (c-t) is .67 times inseam. I ride a 55cm (c-t) with a 54.3cm top tube, 79.5cm (31.3 inches) standover and 74 degree seat tube angle (which effectibely lengthens the top tube). I can ride frames in the 54-56cm range. If you are looking at compact frames, you need to measure the head tube length in addition to considering top tube length. I won't buy a frame unless the head tube is in the 125-140mm range.

Proper inseam measurement is critical. It should be done in bare feet, with cycling shorts. A bike with a level top tube works better than the often recommended book in the crotch method. Block up the wheels until the top tube creates firm, but not heel raising pressure in the crotch, when standing over the bike. Once you know your inseam, 2-4cm of standover clearance is a good range to shoot for. More than 4cm standover clearance will increase the saddle to bar distance, and require a high rise stem or too many steering tube spacers.

When testing these different bikes, I doubt you go to all the trouble to set the saddle to the optimum fore-aft position, and probably don't know the stem length. These two adjustments can make a world of difference in a bike's fit. If you know what you need in terms of seat tube angle, effective top tube length, stem length, head tube length and standover, it's pretty easy to read the geometry chart (or measure the bike) and figure out if it's going to fit.
how can we help without inseam and height????Thierry
Jul 15, 2001 6:20 PM
Thanks so much for your help. Actually I measure 5'8" (1m75) and I believe my inseam is 82cm (32.2"). So I understand the rule for the inseam and the tube length but what about the torso length. I don't own a road bike yet and that's why it is so difficukt for me to decide. I have an hybrid bike 56cm that suits me well in terms of size but the stem and the posture on the bike are way different than on a road bike. For the Lemond 53 the top tube length is 54.5 and the standover is 77.2 cm or 30.4 inch. For the seat angle I would like something relax as I would like to use the bike for both long training rides and triathlons. So far most of the road bikes I have tested have 73,73.5 seat angles. I didn't find any that would get closer to the 78 seat angle that most tri bikes have and I don't want to buy a tri bike (too much exclusive of regular riding).
the 55 Lemond sounds close...C-40
Jul 15, 2001 6:50 PM
The 53 lemond is too small. You would regret buying a frame this small.

The 55 should be OK if your stated inseam is correct. I get a good fit on a frame with a 73 degree STA, a 55.5cm top tube, and a 110mm stem.

The 56.5 top tube is a little long, but you've got an extra inch of height and you may want the saddle positioned a bit forward, since the frame has a 73 degree STA. You may need a 100mm stem to offset the extra TT length, which is OK.

Don't understand your desire for a 78 degree STA. Nobody makes a stock road frame with that geometry. It's strictly a tri bike thing for runners.
the 55 Lemond sounds close...Thierry
Jul 16, 2001 7:21 PM
I verified my inseam and it looks like I was a bit optimistic before (probably the measure I took wasn't accurate enough). Now I am more on the 80 cm side or 31.5" which probably puts me closer to a 53. Although on the Lemond the standover for the 53 is 77.2cm and 79cm on the 55. How important is the standover and clearance? is it more important than the top tube length? or than the actual size based on inseam?
now the 53 sounds better...C-40
Jul 17, 2001 2:03 PM
That's why I stress accurate inseam measurements, preferably done using a bike as the measurement tool. As you've restated your measurements, you fall into the slightly long torsoed or short legged category.

If your inseam is 80cm the 53 would give you the proper standover clearance of around 3cm. The standover clearance really isn't critical, but it directly correlates to the head tube length, which affects the saddle to bar height difference. That's why I also stress measurement of the head tube. Manufacturers like Litespeed finally wised up last year and increased the length of their head tubes by about 1cm across the entire size range, to help get the bars up, without the use of too many head tube spacers.

The 54.5cm top tube on the 53cm frame is none too long, but probably within an acceptable range. 55.5cm would be better for someone that's 5'-8" (in bare feet - are you sure?). I would expect that you will require a 110 or 120mm stem with this frame.

The 55cm would be vertically too large for an 80cm inseam, and a little long horizontally for someone 5'-8" tall.
Apply some experienceKerry Irons
Jul 15, 2001 4:28 PM
These size calculators should help

http://www.bsn.com/cycling/ergobike.html
http://www.coloradocyclist.com/BikeFit/index.cfm
http://www.sheldonbrown.com/harart-frames.html
http://www.electriciti.com/~bikelane/sizing.html
http://www.rivendellbicycles.com/frameinfo/Frame_Sizing.htm
http://www.peterwhitecycles.com/fitting.htm
I am guessing "53"Doll Face
Jul 15, 2001 8:54 PM
55 seems huge for a rider just 5-8. Make sure your inseam measurement is correct. The LeMond will probably provide you with a better fit than most other brands, as your legs seem relatively long. I doubt if you will have to move the saddle forward to get the proper position over the pedals.

Do not be afraid to have alot of seat post showing. As long as you get reach the bars with correct positioning, and the stem is not raised too high, the frame fits. The 55 with its 56.5 toptube will not be as fun to ride as the smaller size.
I am guessing "53"spindry
Jul 16, 2001 5:52 AM
I'm 5'5" and ride a 53 C-T, 51 C-C. If LeMond frames are C-T then a 55 is probably about right.
Hold on a second...PsyDoc
Jul 16, 2001 6:50 AM
All LeMond frames are measured C-C.