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Discussion Starter · #1 ·
on his book, tales from the toolbox, scott parr says stem size is proportional to bike size. as in proportional to wheelbase, i believe. due to my long, looong torso and arms x short femur, i'm on a 130 stem/ 54 c-c/ 54.5 tt bike. i've laso raised the bar.
any thoughts on parr's idea?
 

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Yes and no. Different frames of the same size have different top tube lengths. If you had a 54 cm frame with a 55.5 cm top tube, you'd only need a 120 cm stem.
 

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A big rider on a 39-40 inch wheel base racing bike needs tube angles and a stem to accomodate his upper body length. The seat tube is usually shallower, 73-72 degrees, to make room for the longer femur and keep weight on the rear wheel. So to keep the wheel base within 39-40 inches so the bike corners well, the head tube has to be steeper, 74-75 degrees.

Longer stems come on larger bikes to balance fore-aft weight distribution, but should be fine tuned to fit the upper body, which varies with riders who have the same leg length. You're running a long stem on a relatively small bike. As Mr. Grumpy suggests, you might be better off with a larger frame with a longer top tube. It would allow you to raise the stem more, and would take a little weight off the front wheel, which makes the bike squirrely on descents unless you scoot way back in the saddle.
 

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Discussion Starter · #4 ·
then, i need a custom...

As Mr. Grumpy suggests, you might be better off with a larger frame with a longer top tube. It would allow you to raise the stem more, and would take a little weight off the front wheel, which makes the bike squirrely on descents unless you scoot way back in the saddle.[/QUOTE]

my inseam says i should be on a 53! happens most of 53s have 54/54.5 tt.
i asked cause these days everybody seems happy to put the longest possible stem on bikes... 130, 140 are common. parr's book describes the late 80's scene.
he says 54 to 56 bikes should have 110 - 125 stems and 57 to bigger sizes should have the longer stems.
sometime a go there was a thread on colnago sizing and a feature with phtos of a 53c-t colnago with 130 stem on it. but then... colnagos have slack head angles, longer fron center therefore allowing longer stems.
 

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Maybe not a custom

Maybe, just a different manufacturer. Some manufacturers make their bike with shorter top tubes, some with longer. Some manufacturers make their bike with shorter head tubes, some with longer. (This may force you too many spacers or a "riser" stem).
I think that most riders should use somewhere between a 120 and a 130mm stem. The top tube is the most important tube in the frame. If your seat tube is too short or too long, you can compensate with less or more seatpost showing. If your top tube is wrong, you may have to get a 100 or 140 mm stem, which will throw off your handeling.
Depending on the manufacturer, you could probably fit on a 53 to a 57, depending on the top tube they use.
 

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Discussion Starter · #6 ·
maybe

i feel like i need to stretch more over the bike than before. my back can't stand myself being cramped with 3in diff between seat and bar.
i will ride with the 130 stem before buuying a new biike.
ciocc gives 1-2 cm more top tube than other italian bikes. american frames tend to be longer too/ problem is: if tt grows only and it's not done right, wheelbase grows too much and bike becomes slow, lethargic (i'm exagerating but classic italian geometry gives you very crisp handling).
 

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i asked cause these days everybody seems happy to put the longest possible stem on bikes... 130, 140 are common. parr's book describes the late 80's scene.
he says 54 to 56 bikes should have 110 - 125 stems and 57 to bigger sizes should have the longer stems.
The reason for the larger stems today is that many people are buying undersized frames. The result is the running gag of people posting pics of bikes on EBay with absurd stem and spacer setups along with more seatpost showing than your average mountain bike. Manufacturers have added to the problem by promoting compact frames, which are usually made in very few sizes. Hey if it doesn't fit, just hike the seatpost and use a larger stem. Huh huh.

In my experience using a 140mm stem leads to funky handling, and so does a 90mm. With stems no longer being made in 5mm increments, like quill stems used to be, this leaves you with the choice of 100mm 110mm 120mm and 130mm. The 110mm and 120mm will give good handling on a mid-sized frame. I think you should aim for 110mm. This allows you to get a 120mm if you want to be further stretched out, or even a 130mm.

Buying something right in the middle of what will fit is much smarter than buying something at the extreme ends. If you start with a 130mm or 140mm stem and you find you would like to get even further stretched out, then you are screwed or, at the very least, you end up with an odd handling machine.

The nice thing about using a bike that is the right size rather than something that would fit a twelve year old is that your stem will look normal with minimal spacers and zero rise. If you ever want a higher position for the bars it's easy to achieve without looking like you are riding a clown bike.
 

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"54 to 56 bikes should have 110 - 125 stems and 57 to bigger sizes" ( 58-62) "should have the longer stems" (125-140).

I think Parr is right about those stem measurements.

If the saddle is 3 inches above the bars on this 53 cm frame, that's jacked up pretty high to get optimum leg extention. If a 130 mm stem is needed to get enough room to pivot the upper body forward onto the bars, there's already alot of weight over the front wheel.

The shallower seatpost angle of the small frame, probably 74 degrees, aggravates the problem by placing the seat forward, not back to balance out the weight in front.

Plus, you're forced into an aerodynamic tuck all the time. If the bar height was within an inch or two of the saddle height, you could sit up on the tops, putting most of your weight on the saddle, taking weight off the arms, neck and shoulders. On the hoods, you could stretch your back, and drape your arms, elbows bent, over the bars. And in the drops you could still make your back horizontal and flat, and be as aero as possible.

It might be fun to go to a bike shop and test ride one or two larger frames, just to see how they feel.
 

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Discussion Starter · #9 ·
thanks..

Fredrico said:
"54 to 56 bikes should have 110 - 125 stems and 57 to bigger sizes" ( 58-62) "should have the longer stems" (125-140).

I think Parr is right about those stem measurements.

If the saddle is 3 inches above the bars on this 53 cm frame, that's jacked up pretty high to get optimum leg extention. If a 130 mm stem is needed to get enough room to pivot the upper body forward onto the bars, there's already alot of weight over the front wheel.

The shallower seatpost angle of the small frame, probably 74 degrees, aggravates the problem by placing the seat forward, not back to balance out the weight in front.

Plus, you're forced into an aerodynamic tuck all the time. If the bar height was within an inch or two of the saddle height, you could sit up on the tops, putting most of your weight on the saddle, taking weight off the arms, neck and shoulders. On the hoods, you could stretch your back, and drape your arms, elbows bent, over the bars. And in the drops you could still make your back horizontal and flat, and be as aero as possible.

It might be fun to go to a bike shop and test ride one or two larger frames, just to see how they feel.
i'm on 54. i had a 120 stem dropped(top of bars) 3in below saddle. i want a more relaxed laid back position and moved the bars up 1 in.. the bike became small, tight. i've instalelled a 130 stem then. i will move it even higher.
my fork is threaded so the stems are 70 degr. neg. the higher they go, i get back from the front axle. the idea of being catapulted forward in a crash doesn't attract me.
i COULD ride a 55 but my inseam dictates a 53 and i'm already on a 54. i should be riding a different brand. something like a CIOCC would give me a 56 ttt on a 54 c-c frame. i could have a 115 stem on such frame.
 

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Now that you know how big the cockpit needs to be, you can superimposed those measurements over the geometries of different size frames, and contemplate the implications in terms of handling and comfort.

Some bikeshops used to have a stationary bike with all geometries adjustable, so a rider could change everything right then and try out different set-ups. None of the serious riders had any patience with this device. I don't remember anyone using it.

It took over two years of riding and three bikes to get it right for me. But it was all great fun and well worth it. Good luck!
 
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