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Bike fit question. 53 or 55 PLEASE help.(8 posts)

Bike fit question. 53 or 55 PLEASE help.Ryan
May 13, 2002 5:20 AM
I am about to purchase a new LS Tuscany and would like some reassurance that I am buying to correct size. I am having a hard time determining between a 53 and a 55. The 53 is a closer match to my old bike a 54 CAAD 2. Most of the frame dimensions are the same. The only fit difference is the seat tube (53 Tuscany vs. 54 CAAD 2) and the stand over height (77.6 Tuscany vs. 79.2 CAAD2). I have test rode both sizes and by varying the setups (basically adjusting seat height and stem length) can get both bikes to feel pretty much the same.

I am 5’10.5”. My inseam is 80cm, so using the standard formula of inseam times .67, I get a seat tube of 53.6. Making the 53 Tuscany appear to be the correct size. The guy at the shop also said my upper arms/torso appear to be at/around 90 degrees on the 53.

When I rode the 53 Tuscany (with 10cm stem, 3TTT Forma SL bar) I could reach the hoods and the drops a lot easier than on my Cannondale. When I rode the 55 Tuscany (with a 9cm stem) I felt a touch stretched out.

I guess the only reason I am questioning the 53 is that I usually ride my Cannondale (85% of the time) with my hands on the corners of the bar (space between top and the hoods) and I think I would be in the hoods a lot more on the 53 Tuscany.

Note: After about an hour and a half on my Cannaondale my lower back usually starts to hurt. I am unsure if it is a fit issue or the stiffness of the aluminum.

Thank you very much for any help/input you may have.

Ryan
Almost identical situationAFred
May 13, 2002 5:50 AM
I am fairly close to you in size, and had the same issue two years ago when I bought my LS Classic, i.e. no 54 cm c-c. After a fitting session with the Size Cycle, I went with the 55 c-t, which on the Classic has a 55.5 top tube and a 9cm stem. I recall my LBS crew working over the top-tube and stem lengths measurements quite a bit.

Like you, on my old 54 c-c aluminum Trek I used to ride on the tops and not on the hoods for feeling too stretched out, but with my "new" set-up I have been perfectly comfortable and have shed the lower back problems. Bottom line: before shelling out $$ you should consider investing a little time and money in a proper fitting session. Some core strength exercises didn't hurt me either. Good luck.
Listen to yourself, man. Get the 53. You basically saybill
May 13, 2002 6:04 AM
over and over in different ways that the 53 is a better fit. You ride the C-dale perched on the corners of your bars because you're too stretched out on the hoods. Get the 53. If it makes you feel any better, I've got an 81 cm inseam, I'm about 5'8", and my LS, measured c-c, is a 53, and it's certainly not small (for whatever reason, your measurements are garbled in your message, but I think that I see 5'8" there).
The most important dimension is probably the top tube, so that you feel comfortable in the cockpit with a 100 to 120 stem (I think that 90 is a little short and 130 is a little long according to what I've read about the way the stem length can change handling and to some extent have experienced, although both are certainly doable). Seat height over the top tube is largely irrelevant, within the rather generous limitations of seatpost length and standover height. You basically just need to have enough seatpost exposed so that you can set your bars down low enough in relation for an aero position.
Usually I don't get involved in these "right-size" threads because the information is never good enough and fit is, well, if not exactly subjective, individual, anyway, but you seem to want corroboration of what you already know.
Sounds right to me.dzrider
May 13, 2002 7:35 AM
Nothing wrong with a little corroboration! Most of us can choose between two sizes without being completely misfit. If the seat is not all the way back and the post and stem don't flirt with the limit line on the 53 get it.
what's the problem, then?elviento
May 13, 2002 6:10 AM
"I guess the only reason I am questioning the 53 is that I usually ride my Cannondale (85% of the time) with my hands on the corners of the bar (space between top and the hoods) and I think I would be in the hoods a lot more on the 53 Tuscany. "

Hands in the hoods is a more normal position, isn't it? If you are worried the bars may be too low, it's easy to raise it with proper stem/spacers setup.

If you feel stretched out on a 55 LS even with a short stem of 9cm, then definitely avoid it. Way too big for you.
53 is small, recheck inseam...C-40
May 13, 2002 8:30 AM
If I read your message correctly, you're 5'-10.5" tall with a short 80cm inseam. I'm 5'-7" tall with an 83cm inseam and I fit properly on a 54cm Cannondale. I've also fit quite well on a 55cm Litespeed, both with a 110mm stem. I can't imagine someone of your height needing a small frame and a short stem.

Check your inseam by blocking up the wheels on your bike until you get saddle-like pressure in the crotch when you stand over it in bare feet wearing cycling shorts. The distance from the floor to the top of the top tube is an accurate cycling inseam.

If your legs are really that short, a 55cm might be too large, vertically, but it has the virtually the same effective top tube length as your C'dale. To compare top tube length of the C'dale with it's 74 degree STA to the Litespeed with it's 73 degree STA, you have to add 1.2cm to the C'dale's 54.5 dimension, which makes it effectively 55.7cm, compared to the 55cm Litespeed's 55.5cm. The 53cm Litespeed would have a 1.5cm shorter top tube than your C'dale.

If you have at leaast 2cm standover clearance, I'd go with the 55cm.

The only other factor you have not taken into account is the head tube length, which affects handlebar height. Comparing the two can be tricky if one has an integrated headset, and the other one doesn't. A 53cm frame will have a lot shorter head tube, requiring more steering tube spacers and/or a higher rise stem.
53 is small, recheck inseam...Ryan
May 13, 2002 9:17 AM
Re-checked measurements with a friend at lunch.
Inseam 31.5" (80.01cm)
Torso 26.5" (67.31cm)
Arm 23.0" (58.42cm)

By my calculations that is a 53.6cm seat tube and a reach of 66.87cm.

The 53 LS speed has a 54 TT (just like 54 Caad2). Since my flexability is not that great the "ideal" 66.87 is likly too long for me. If my flexabilty improved a 120 stem would bring me very close to ideal.
top tubes are not the same...C-40
May 13, 2002 12:22 PM
You didn't read my posting carefully. Top tube lengths cannot be compared directly, if the seat tube angles are not the same. The top tube of the 53cm LS is effectively 1.7cm shorter than the top tube on your C'dale.

Your C'dale's TT is 54.5cm PLUS another 1.2cm to account for the difference in seat tube angles, for a total of 55.7cm.

Remember that you will have to move the saddle 1.2cm further forward on the LS to get the same position with respect to the bottom bracket that you have on the C'dale.

Seriously consider the LS Sienna. The sloping top tube will give you the additional standover clearance you need, and the same TT length that you now have.