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Discussion Starter · #1 ·
Hello!

I'm new to the forums, however, would consider myself a bike enthusiast that unfortunately doesn't have all the answers, nor a deep pocket. :p And all input is greatly appreciated!

My second purchase of a road bike is upon me, and I have had great success from BD.com, and I plan on going to them again for the big purchase. This steel bike has been jumping out at me, but, unfortunately the sizes listed are a little in-between the sizes of my last bike that was 54cm. Pro Level Steel Road Bikes | Commuting | Commuter Bikes | Motobecane Gran Premio PRO

After looking at the geometry chart, the 53cm looks the closest to my previous, however, with the slanted seat tube, and my larger torso than legs (I'm 5'9 with a 31' inseam) I was wondering if it is wise to go with the 56cm.

Suggestions?
 

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Cycling induced anoesis
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Since you're asking a question relating to the geo of your previous bike, it would be helpful if you posted the year, make and model of that bike (or the geo chart) for comparison purposes.
 

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I'll go ahead and shoot from the hip.

Get the smaller one.

More seriously, though, I think you can learn a lot by looking at the fit of your previous bike. Are the seat tubes angled a lot differently? That messes with the relationship of reach and top tube length. Actually, these guys address it well in proposing a new system for sizing bikes...
Tech Center

There's also always the question of why a bike enthusiast who already has a road bike and doesn't have deep pockets is buying a road bike. In a sense, it's not my business. But I think if you're trying to get good value, buying the same thing twice is a questionable choice... What are you looking for from another road bike that will be different from the first? No judgement here, I have two road bikes myself, and was still at three about a month ago.

EDIT: Oh, also the stem length that it took for you to nail the fit on your current bike is pretty informative. If you have a 140 mm stem on there, for example, erring to a bigger bike would be better... if it took you a 90 mm or shorter, going to a smaller bike will work better. Just understanding that my "bigger" and "smaller" are mostly referring to reach as definited by the Slow Twitch site, which it sounds like may not be the same as looking at effective top tube length in your case.
 

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Discussion Starter · #6 ·
@andrwswitch

Well, my previous bike was the Motobecane Cafe Noir, and it is my first fun real road bike. Immediately, I made it mine by removing the flatbar, putting drop bars on it, and keeping the quick-shifters on it. She has about 5,000 miles on it from several Ragbrai's and my nonstop commuting. However, I made the mistake of taking it to the Caribbean with me for 6 months where I lived and the salty-mist and weather down there was not nice to her steel frame. So, I figured, it's time to get another bike since I moved back to the midwest. I just been accepted into nursing school and feel like celebrating.

As for my previous bikes stem goes. The cafe noir came with an adjustable angle stem that when measured is 100mm. However, I kept it at about a 30 degree angle up from the horizon that seemed to be really comfortable.
 

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I hate to ask, but are you worrying about the seat tube angle or the top tube angle?

Also, the top tube length you're accustomed to matches the top tube length on the 53 cm Gran Premio. Seat tube angles are a match. All this is what Bikes Direct is reporting, so it's as true as their charts are, however correct that is...

When you say you tipped your stem up 30 degrees, do you mean in relation to the ground or in relation to perpendicular to the steer tube? They're quite different... Check out this stem calculator.

Bike Stem Calculator - Brightspoke

EDIT: Oops, another option (though one I didn't take last time it came up) is to buy a bare frame and migrate the components from your old bike to it. This can make sense if both bikes are from the same period and the components on the donor bike aren't too chewed or bizarre.
 

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Discussion Starter · #9 ·
To be honest, I wasn't sure about the stem angle and the top tube length if the positioning of the bike was going to be too aggressive. I don't mind getting low and aerodynamic, but I'm foreseeing a brooks b17 on this bike in preparation for when I do my longer 50+ rides.
 

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The tricky thing with regard to positioning is head tube length. There's actually quite a lot of adjustability there. Forks are typically rated for no fewer than 30 mm of spacers below the stem clamp, and they can sometimes have more. You could email BD and ask about that, and about how the steer tube is cut. Anyway, it takes a relatively odd setup or odd proportions from a rider to have real problems with this.

Do you still have the old bike? Post a picture.

Come to think of it, that Moto is listed as having a 1" headset. I wouldn't want to buy a new bike with that size. It's less and less common lately, and very few enthusiast-level bikes ship with it. One of the things I look for in choosing components is ease of maintenance - having something unique is annoying.

There are a couple of brands that have a bit more interest in giving you more head tube, facilitating a more upright position, if a relatively typical geometry won't work for you. In particular, I'm thinking of Rivendell and Velo-Orange. Riv's crazy-expensive, but they carry a Soma frame that's a bit more reasonable. I think there are some Salsas with a geometry to facilitate a more upright position. Salsa has a pretty good dealer network, so you could take your old bike, if intact, to a dealer and have a much better conversation about it than here on the 'net. This may not even be something you need - just because a lot of people insist on setting up their bikes as on slamthatstem.com doesn't mean you have to.
 

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Since your last bike is a BD bike, and your next one will be, I'd email and ask them. They should have a pretty good feel for their bikes.

I am a long torso, short let person. I ride a 56 in my Specialized Allez and my Motobecane Fantom. I am also over 6' tall. To be honest, I cannot imagine someone about 3" shorter than I fitting the same basic size bike as me and not feeling stretched out. Added to that the 53 seems to match closest to your current ride it seems like the 53 would be the way to go for me.

Again I would ask BD their thoughts. The 53 comes with a 100mm stem, so you could lengthen it by up to to 3cm before it starts going crazy. The 56 has a 110mm so you only have about 2cm before the stems are getting very short. As was mentioned, it has a 1" steerer, so swapping stems gets hinky as it is not standard stuff anymore. But if your heart is set on that model, go with it and enjoy.
 

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I'm inclined to say that at 5'9" with a 31" inseam that the 56cm frame will fit better. A 53cm would fit your inseam better but would be too short for your torso/arm combination and would result in a ridiculously long stem. You should still have plenty of standover clearance with the 56cm frame.
Just to muddy things up, at just over 5'8", I'm finding my favorite size is a nominal 52, or around a 53 cm top tube. The height/bike size thing would blow it for me...
 

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Considering the info you've provided, with one important caveat, I'd suggest the 53cm Gran Premio. The caveat being, your current bikes head tube length and spacer set up are unknowns, so I suggest measuring them and estimating what the new bike will require to match your drop - assuming you want to match it.

That said, considering you converted a flat bar bike to drop bar and are using an adjustable stem and (Rapidfire) shifters, I doubt you'll be too concerned with aesthetics like flipped up stems.

Just remember that reach will (respectively) increase/ decrease as you lower/ raise the bars.
 

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53cm and 56cm bike difference is not just 3cm, the real difference really much more because usually not only one dimension is bigger.
If you feel very comfortable on 53 let me guess you will be very uncomfortable on 56cm.

This was just my case by the way. I own two bikes - one 53cm and other 56cm.
On 53 one I feel like riding a mule but very confident and comfortable while buttocks are always going considerably behind the saddle which is not very comfortable.

On the second one I constantly felt pain in palms and was unable to do very sharp turns so shortened the stem from 13.5 to 11 cm. Now it feels just so much better.

The bottom line - you can always make bigger bike smaller but making small bike bigger will be more challenging and not too efficient. My recommendation is to do some longer test ride on the desired 56 cm bike and if you feel uncomfortable (somehow I am sure you will) just change one size down. DO NOT buy without test ride if you are not confident about the size.

Another note - if you are considering new bike with different bar type please note flat bars usually require bigger size while drop ones can be on a smaller bike.
 

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The bottom line - you can always make bigger bike smaller but making small bike bigger will be more challenging and not too efficient.
It depends on just how far 'off' sizing is for a given rider, but based on my experiences, I tend to disagree with this because it ignores the importance of maintaining proper f/r weight distribution. There's more to proper positioning than simply getting the contact points right, thus the front-center references in geo charts. Where a rider is positioned is as important as getting reach/ drop right.

Re: the park tools website, the one measurement that I disagree with is determining reach by measuring saddle tip to bars. That only works if someone is duplicating a bike fit. Once any relevant component changes, the reference is flawed and can mislead. Better to calculate reach by measuring (or referencing) ETT, STA, HTA and HTL.
 

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I was suggesting it for Kumachan. I think Park actually notes that using different saddles can mess with it. The thing I like about that work sheet is that I don't own an angle finder or even a decent-sized level, but their worksheet can be filled out entirely with a tape measure and a plumb bob.

Well, I guess I had to skip saddle angle and can't use stem angle as they define it. But I still have found it a very useful approach. It certainly lands the target bike a lot closer than other ways I've tried to rough them in.
 

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Discussion Starter · #19 ·
Considering the geometry of the 53cm Gran Premio is closer to my 54cm Cafe Noir. I'm leaning towards the 53cm. My biggest concern was the length of the top tube causing me to be as to aggressive of a position for long distance rides. My average commute is 32mi to work and back.
 

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Considering the geometry of the 53cm Gran Premio is closer to my 54cm Cafe Noir. I'm leaning towards the 53cm. My biggest concern was the length of the top tube causing me to be as to aggressive of a position for long distance rides. My average commute is 32mi to work and back.
I wouldn't fret over reach. The ETT and ST/ HT angles are so close as to be a wash on both bikes, so reach should be relatively easy to duplicate.

As I mentioned earlier, the unknown is HTL and stem/ spacer set up (drop) on your current bike. But considering the HTL on the 53cm Gran Premio is 150mm's, and your inseam is ~31 inches, I think you'll have room to experiment.
 
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