Hi

I'm looking at a Specialized Roubaix to complement my cross-country riding.

My Giant Anthem is a size Large (20) and I have a 34.5" inseam (I'm 6'1") and not terribly flexible!

Would that place me in the 56 or 58 sizing on a Roubaix?

Thanks
Mike

58cm

Another vote for 58cm.

I would lean towards the 58cm, but I think either would work. I am 5'10" and was between a 54cm and 56. I went with the 56, but you can see from the pic that the saddle is a bit low and the stem is a little short. I preferred the feel of the 56cm, but I think my upcoming Tarmac will be a 54cm.

My son is 6'2" and thinks my 56 is way too small for him. He is really confortable on his 58cm.

60cm would be perfect for you.

I'd say 56cm. Specialized runs big so a 58cm Roubaix is more like a 60cm conventional frame with a stretched head tube.

i assume you mention the anthem because you feel you have a fit you like. so i would measure the only measurements that really count. the BB to top of saddle, and tip of saddle to handlebar clamp. then, again, assuming you have access to the roubaix adjust to the same dimensions and evaluate the aesthetics. which are really the only thing that matters once acceptable dimensions have proven to be practicable.

Yes, you're right, I ride almost back-pain free with my Giant Anthem. Hoping to find the same comfort in a road bike. I like your logic.

Thanks everyone for your input. Never thought I would receive so many varied answers. I guess I'm being educated, which is a good thing!

I agree with your second sentence. I ride a 61cm Litespeed M1. If I were on a Roubaix I would be riding a 58.

Hard to say about your first sentence since we don't have his measurements. Based on what the OP said, however, I still think the 58 is the right bike for him.

The larger frame with a short stem will put you in a more upright position.

I'm 5'11" with the same inseam. My size on the Roubaix would be 54cm. I based it on that comparison.

I'd look at a 58cm (582mm ETTL). And, if the LBS has a 61cm (600mm ETTL), I'd look at that, too. The 61cm is 18mm longer in the toptube, but, picks up 20mm in headtube length. Both sizes use the same stem. Your LBS should be able to order in a 61cm with no obligation to purchase. Without knowing your body dimensions/proportions, it's hard to be accurate with this.

I'm 5'10" (shorter torso/longer legged) and was fitted to a 58cm Specialized. But, with my own thoughts on fitment, I later bought a 54cm and feel much better. I went from struggling with various pains on the 58cm to easy 100+ mile days on a 54cm. YMMV.

You need to realize that the OP is not flexable, and a bit larger frame will allow him a more upright postion providing him with more comfort. This is a long distance bike so comfort is most important not an aggressive position.

He's riding a bike now with a TT about 1 1/2" longer than what the 58cm specialized will be, and a 60cm might be even better.

I thought a smaller frame would provide a more aggressive position seeing that the seat stem would need to be raised to compensate, therefore creating a steeper angle to towards the handlebar area.
Maybe I have the wrong understanding?

You described it a bit awkwardly, but no, you are not wrong. That is exactly what happens in terms of saddle-to-bar drop (or rise).

The top tube also gets longer on bigger frames, though, which can stretch you out.

Two exceptions:

The shorter frame will allow a more upright riding position, despite the (generally) shorter headtube, because your arms will be angled more downward versus being stretched out by a longer toptube. If the headtube length/height is an issue, it's easy to swap the stem to something with more upward angle.

The second is that you're comparing MTB geometry to roadbike geometry. The riding positions are totally different. Furthermore, we don't know which Anthem he has. Giant's geometries and position ideals have changed, over the years. My '08 Giant Anthem 1 had way more toptube than what I ride on the road.

Yes, but his other bike is a mountain bike...... At any rate he needs a 58cm minimum.

Sorry, i should have specified it is a 2010 model.

https://www.giant-bicycles.com/en-ca/...x4/5417/39302/

As fate would have it...we are the same size...and a good size to be. 58 on the button. Reach will be right...I have a 110mm stem turned down...correct amount of post showing...not too much...not too little. Toupe is set just a hint aft of center in the rails. I could ride a 120mm stem...and probably will in the summer. Hey guys that seek Roubaixs aren't terribly flexible so you didn't even have to mention that.
You will really enjoy the riding position.
I just built mine up with Campy...you don't see a lot of Campy Roubaixs...or Tarmacs for that matter...and just got it out on the road for a 40 deg shake down run. Got a late start and did a quick 20 miles. This bike lives up to its reputation...very comfortable and fast. I ordered the frameset from Specialized. Robaix Pro...threaded BB....10r FACT carbon, hidden cable routing. Let me know if you have any questions about fit or specs. Below is pic of my bike...have red tires on order.
What I can tell you is the bike doesn't feel plush...but bumps are very muted. This is achieved with a stiff frame laterally with relaxed angles. The long wheelbase, pronounced fork rake and rear triangle geometry give the bike a good ride and yet the frame is stiff for energy transfer. The bike isn't nervous or quick handling...just goes where you point it. I wanted the bars close to my saddle level which is easy to achieve with this geometry even with our long legs. If I want a bit of drop, I can slam the stem to the steerer.
Hard to go wrong with a Roubaix for distance riding.

I think you would be happier with a 56cm frame. 58cm will require you to stretch and it will be uncomfortable.

56!

believe me i had a roubaix that fitted a bit big.....now i ride the next size down, and the difference is HUGE!

56 to 60 -- any could be right for you. It will depend a lot more on you than us.

I'm a shade over 6'2" and ride a 61cm. A 58 feels cramped to me.

ummm no. 56 for a guy our size defeats the purpose of a Roubaix. Reach will be served one way or another...unless you want to ride like Mary Poppins...bolt upright. Reach can be achieved thru drop...aka a 56...or horizontal reach aka 58. Of course a 6'+ rider can ride a 56. But in that case...with a 190mm head tube, why even buy a Roubaix...buy a Tarmac or a R3 or something else with average head tube.
Since reach will be served one way or another...if riding with handlebar near saddle height...reach is achieved horizontally. I will say again, I could ride a 120mm stem on my 58. I am not stretched out on it. On a 56, I would ride a 130-140mm stem and have more drop. I don't want that and neither do most Roubaix owners.

OP...I too ride flat bar bikes and I ride the same size mtb frame as you with 24.2" top tube and btw a 130mm stem. The beauty of the Roubaix is the riding position will be very close to your Epic which likely has the bar height close to the saddle height. This is why many prefer the seating position of a mtb...it is less aggressive than most road bikes. That is the point of a Roubaix and why it is a wildly popular bike...which is basically a medium to aggressive mtb position on a dropbar bike.

So what is a Roubaix then? Most that know cycling get it but some don't. The Roubaix is basically a fast Rivendell. Its a very sophisticated carbon road bike wrapped in Rivendell fit philosophy.
For those that don't know what Rivendell's fit philosophy is...its basically a fit that served the road bike industry for decades....a time when average recreational riders didn't try to set up their road bike to emulate the .000001% of top racers. This was more readily achievable with quilled stems...which is how Rivendells still come. You don't however have to buy a heavy and retrotech Rivendell to be comfortable on a road bike. Just buy a Roubaix and size it to Rivendell's fit philosophy:

Choosing a Frame Size
(Our bikes, and most non-Italian bikes, are measured from the center of the crank (or bottom bracket) to the top of the seat tube. In the old days this was called the English Method, to distinguish it from the Italian Method, which measures to the center line intersection of the seat and top tube (think, "center of the seat lug".)
In this section, In General is about bike sizing in general, and is good to read if you don't know about it, or just want to read what we have to say. So it's sort of a primer, but it's not one of those primers that has such basic introductory information that everybody already knows it and you're wasting your time reading it. It's a better primer than that.

And then Sizing Rivendells talks about how we size the frames we design and sell--custom Rivendells, Atlantis, Sam Hillborne, Hunqapiller, Betty Foy, Bombadil, and the earth-rattling A. Homer Hilsen.

In General
People ride bikes that are too small. If you go into a bike shop or ask the local fast riders about frame sizing, you'll likely hear comments such as, "Smaller bikes are lighter, stiffer, more maneuverable, and more efficient."

To that we say this:
Small has to be lighter, but we're talking ounces, and let's not talk about ounces until your belly is so ripped that you're regularly mistaken for one of those guys in the Dance Theater of Harlem. A bike shouldn't have any unnecessary weight, but if the weight comes by means of a larger frame that fits you better, or stronger wheels that stay truer, or a safer frame that doesn't fail catastrophically, then we wouldn't consider that "unnecessary" weight. It's weight that carries its own.

Here's the way it works, in any given tube on a bike. In your left hand is a downtube that's 31.8mm in diameter. The butts (tube wall thickness as the ends of the tube) are 0.9mm thick.

Less than a millimeter, about 1/28th of an inch.

To look at it, you'd think it was nothing--that the tube was on the verge of collapse. The _belly_of the tube (mid portion, between the butts) is 0.6mm thick. Fortunately you can't see that, because that's even scarier.

Now, in aluminum or carbon or titanium or anything other than strong CrMo steel, these dimensions would be instantly foolish and dangerous, but it works in good steel, because steel has the right balance of strength, toughness, and rigidity. This tube is 650mm long and weighs 10.6 ounces.

In your other hand is a lighter version of the same tube. Its butts are 0.8mm, it's belly is 0.5mm, and it weighs 8.8 ounces. The decrease in butt thickness is 12 percent, the decrease in belly thickness is 16.7 percent, and there's a proportional decrease in durability, if we consider resistance to fatigue and denting to be "durability issues." The weight savings is less than 2 ounces.

As a designer/builder, what do you do? If you're building for longterm hard use by heavy men over rough terrain, you reject both of them and pick a tube with 1.2mm butts and an 0.9mm belly, even though that tube weighs 14 ounces. You figure what's five or six ounces? I'm crossing Russia with a load of pigs and canned food and carrying water for a week, and I need this thing to last!
-----
Small also has to be stiffer, but marginally so, and it has not been proven to mean beans in a bike frame. Certainly a frame should be stiff enough to be safe and controllable and to feel halfway normal, but if one frame is so close to another in stiffness (as is likely to be the case when you're talking about two sizes of the same frame), the difference in stiffness is not worth talking about.

"More maneuverable/efficient"? A bike that's more maneuverable sounds good, until you look at the other side of the coin: If you can cut around a dead raccoon that you didn't see until the last millisecond, or dive between two other riders in a race around a tight corner, then it's you, not the bike, that's doing it. In any case, a "highly maneuverable bike" is easily maneuvered by a sudden gust of wind, an unseen pothole, and any other of a dozen or more forces outside your body that act upon it. Or a sneeze. So forget getting a smaller frame because it's "more maneuverable."
Efficiency.
Bikes are already efficient enough. Efficiency is one of those concepts that sounds universally desirable, but in the context of a humble rider wanting to go have fun and get some exercise on a bicycle, is totally overvalued. Once your bicycle has smooth bearings, true wheels, a lubed drivetrain, brakes adjusted so the pads aren't rubbing on the rims, and an efficient engine (that would be you), it is efficient enough.

Too-small bikes are not comfortable
Every day we talk to folks who bought a $5,500 titanium this, or a $6,500 carbon fiber that, and now that the honeymoon is over, they realize it's not comfortable. Sore neck, sore lower back, sore hand---and almost without exceptions it's caused by a frame that's too small and doesn't let them raise the bars high enough to cure these ills. Understandably, they're feeling foolish and bummed out.

Handlebars too low cause 90 percent of the discomfort people suffer. And buying a frame too small guarantees that the bars will be too low.
People often size bikes by the top tube length. It doesn't make sense. Since the reach to the bars is so obviously important, it's OK to be concerned about the top tube length. But don't let it lead you around by the nostrils. If the top tube is in the right ballpark, you do the fine-tuning with stem length. Also, there's a good deal of misunderstanding about the effect of top tube length. Scroll down a bit and you'll see how a shallower seat tube angle and higher handlebars can make a bike with a 59cm top tube feel shorter (in the reach) than one with a 57cm tt. Don't go there yet, though.

Sizing Trends
If you look at old racing photos or drawings, you'll see bikes with "a fistfull of seat post" showing. That was the rule --- a fistfull of post. You bought a frame size that, when the saddle was set at the right height for you, exposed a fistfull of seat post! If in order to get the saddle at the right height, it required much more than a fistfull of seat post, then the frame was too small. These days, "a fistfull of seat post" sounds quaintly stupid, charmingly naive, cute but dumb, stay away from me with your dangerous folk medicines!

And yet, riders back then were a lot more comfortable. We aren't suggesting that you go by "a fistfull of seat post," but that simplistic approach was (and still is) successful because it allowed the handlebar to be close to the height of the saddle. So it resulted in a fit that took weight off your hands, and strain off your neck and lower back. (It also allows sufficient standover clearance. In other words, when you straddle your bike, your genitals may rest on the top tube, but your pubic bone will easily clear it -- as you'll notice if you grab a handful of genitals and pull up. Apologies if this is too graphic for you.)

In those days, most saddles were leather, and most leather saddles (of any vintage) sit higher above the saddle rails than do modern plastic saddles. So, on a modern plastic saddle, the equivalent rule might be "seven fingers of post." Of course, fingers vary in fatness. Fitting and sizing are not sciences.

How to Size any Bike, Including Ours
Want some sort of a concrete recommendation for sizing a road bike? Okay. You have to know your saddle height. If you know your saddle height, read the chart below. If you don't know your saddle height, take off your shoes, stand on a hard surface with your feet 10-inches apart, and measure between your legs (the tape measure should be right in the middle) from the floor to your pubic bone. Not your genitals. Hit the bone. Figure out how to do this using a thin, hardcover book and a metal tape.

Your floor-to-pubic bone measurement is your pubic bone height.

Example: If you are 5 feet 9 1/2, your pubic bone might be 85cm. Your saddle height will be about 75cm.

Once you've determined your saddle height, you have a simple subtraction to determine a good frame size. "A good frame size" doesn't mean it's the only size for you. The whole purpose of sizing is too give you a comfortable riding position, and for most people that means getting the bars level with, or within a couple centimeters, of the saddle height. The lower the number you subtract, the higher the bars can be. In France or England in the '40s, you'd subtract about 15cm. In the case above, that would have that 5-foot 9 1/2 inch rider on a 60cm frame.

If that same rider got sized in 10 different bike shops, probably 5 of them would suggest a 54 to 55. One would say a 53, two would say a 56, and one would say a 57. The more expensive the bike, the more likely the size is to be small.

If you're psychologically uncomfortable with a frame so big, instead of subtracting 15 from your saddle height, subtract 16. If you're a tall guy and have long arms, go 17--but be prepared to use a stem with an upslope, or a long quill, because on a typical modern road bike with a level top tube, a small-stack headset, and a short-quilled stem, a 17cm difference between saddle height and frame size will put them bars too low (for comfort).

Sizing Rivendells (the bikes we design) --frame sizes measured center of crank to top of seat tube
When you come to us already owning two or three or half a dozen or more bikes, and I recommend a size two to five centimeters bigger than the bikes you already own and have spent lots of money on, your brain tries to reconcile what you have (and have spent lots of money on) with what I've just recommended.

Sizing chart for Riv-designed frames…see below…by Pubic Bone Height (PBH) & Saddle Height (SH - measured from the center of the crank to the top of the saddle parallel to the seat tube). For 700c, 26" mtn, and 650B wheels. All measurements in metric (cm).

This chart is a guide, and the numbers are based on extensive experience with several thousand riders over the past decade or so. Variances will be minor, but no chart can account for personal preferences or extreme crank lengths, and so forth.

For any given size, the standover heights (height of the top tube) are lower, because the bottom bracket is closer to the ground and the seat tube angle is shallower (less vertical). "Lower top tubes" is not the goal in itself, it is just a result of the frame design. But it is a key reason you can straddle a bigger one-of-our-bikes than one-of-theirs.

Standover clearance, though, is highly overrated.
You need to be able to straddle the bike when waiting for the light to turn, but you don't need oodles of clearance.
And you pay for extra clearance with lower handlebars and less comfort, so at some point you have to ask: "Am I getting this bike so I can stand over it with a fist and a half of air between the top tube and my crotch, or do I want to be comfortable when I ride it?"

The Consumer Products Safety Commission requires an inch between top tube and crotch, but doesn't define "crotch." To us it means pubic bone. Everything we do here, frame-sizing-wise, revolves around pubic bone height (PBH). When you get a Rivendell, you get at least an inch of clearance, and usually more.

Every builder has, or at least ought to have, a bias to his frames. Our bias is comfort. From comfort comes efficiency, strength, endurance, control, and fun. The best way to achieve comfort is with higher handlebars, and the first step toward higher handlebars is a larger frame size.

A Good Position For Many Riders
When you're in your riding position with your hands on the hoods, you should be able to put your hands behind your back without your torso plopping down onto the stem. For most riders, that means a back angle of 50-to-65 degrees.

We're less adamant about the knee position relative to the pedal, but mention our preference here only to get you thinking. We like it behind the center of the pedal, because that way, the downstroke helps you maintain a rearward position on the saddle. If it's directly above it, you tend to scooch forward more. In any case, it is not easy to achieve this position with a normal, off-the-shelf bicycle and conventional sizing methods.

Here are some other things related to fit that 99.999 percent of the experts don't know, haven't considered, and don't talk about:
-- As the handlebar gets higher, your arm becomes more horizontal, effectively getting longer.
-- As the bar gets higher, it also retreats toward you. How much? On a bike with a 73.5-degree head tube, raising it 4cm brings it back 1.5cm.
-- Getting a shorter stem without also raising the bars can have a self-cancelling effect. And if you raise the bars, you may even need a longer stem.
-- Top tubes of a given length tend to feel shorter on bigger frames than on smaller ones, so if you currently ride a 56cm bike with a 55cm top tube, but you know you can fit a 58cm frame, don't be scared off it just because it has a 57cm top tube.

If you aren't sure whether your saddle is set at the right height, or if you just want another opinion, measure your pubic bone height. With your bare feet ten to twelve inches apart, measure from the floor up to your pubic bone. Hook a metal tape through a thin, hardcover book or a record album cover, and push up until you smash into the bone. Have a friend take the reading on the floor. This distance minus an inch (25.4mm) is nominally the highest top tube you should have. Sole thickness affects it, too.

Thanks guys for all of your input.
I'm going to take the basic measurements of my Giant Anthem and see if I can find an lbs that has a 56 and 58 in stock and see how they feel.

Frame sizing (which isn't fitting) is contentious and something as crude as pants size and height is of very little use. You need to try some bikes. There's no other way.