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Discussion Starter · #1 ·
Hey guys and gals,

I am new to the road biking scene, currently I commute to work using my mountain bike, but i'd like to start doing races and long rides and a mountain bike would kill me going for a 40+ mile ride..

Now the question I have is about sizing I have gone to so many shops and tried various bikes.. I am trying to make sense of the knowledge I've been given.

Specialized Roubaix - 56cm = too big
Specialized Roubaix - 54cm =just right
Cannondale Synapse 5 - 51 cm = Just right
Felt Z100 - 52cm = too small.

I am looking at a cannondale 2008 Supersix 54cm.. But I am worried about sizing as multiple people have said various things..

I am 5'7" 31-32 inseam on pants 31.5 Leg length..
My Arm Span is 67.5 inches or 171.45 Cm


Thanks,
RR
 

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Since you seem to prefer a 51 from Cannondale (Synapse...Just right), then the 54 might literally be a stretch.

The only way to know for sure is to test ride it. There is no magic formula that we can give you over the internet, no matter how many measurements you take. Bikes are real, physical objects that you need to interact with over thousands of miles. If you're looking at a killer deal on the last Supersix in the shop, and it's the wrong size, just buy a new CAAD10 in the right size, for what will likely be the same price.
 

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Cycling induced anoesis
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When trying to pin down sizing requirements, you have to keep in mind that there are no industry standards for measuring to determine a bikes frame size. So comparing brands (and sometimes even models within brands) is going to get you little in the way of reliable info.

The other variable here is that you're comparing relaxed geo bikes like the Felt 'Z' series and Roubaix, with a race bike - the SuperSix. Even if you compared a race bike with an endurance bike of similar geo, they're likely to fit and feel different.

As an example, a 54cm Roubaix and 54cm SuperSix are within 4mm's in reach, but stack height varies by 2cm's. The shop could equalize that difference with stem angle/ spacer adjustments, but on initial test rides, the bikes would fit and feel different. I suspect this is what you're experiencing.

If you're shopping new, you should have enough confidence in the LBS to let them handle sizing, then fit. If you don't, then consider a shop that you do trust.

OTOH, if you're starting to look at used offerings like the '08 C'dale, you either trust your gut during test rides, or, if the bikes feels good on the test ride, ask the seller to bring it to the LBS of your choice for assessment.

This being your first road bike, you'll likely tap them as a resource after the sale (for fit), so may as well get them involved prior to making this purchase. Might prevent you from making an expensive mistake.
 

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Cranky Old Bastard
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2,337 Posts
The best way to decide on bike fit is to download the geometry charts and compare the models that you're interested in.

Find the one that fits you best and look at the numbers; especially the Effective Seat Tube length and Effective Top Tube length as those two have the biggest influence on what size frame will fit your body.

As you learn more about it you will understand the differences between "racing" geometry and "comfort" geometry by looking at angles and rake and trail figures.
You have to consider what type of riding you want to do to determine which frame fits your needs.

We can't just throw a leg over a bike and buy that size anymore. The better that you understand the numbers the better the choice you'll make.

Good Luck!
 

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Discussion Starter · #6 · (Edited)
Sorry maybe I was unclear. The issue is i've gone to several Bike shops and tested a few bikes as well as friends bikes.. I have two shops saying they put me on a 54, and the cannondale dealer who put me on a 51 and partially fit it to me. Which also could influence my decision as no other shop has done that yet.. I've tried to do the research, but i'm not finding anything of substantial value to help un cloud the water so to speak.

The 54 Roubaix felt just as comfortable as the 51cm Synapse, HOWEVER I liked the way the synapse felt in regards to pep and handling. Nothing over in regards to fitting but everything in regards to performance.

The Supersix and the bikes i've been on are similar in geo, and actually may even fit me better than others, I will test ride it and see how it feels. I've learned a lot through test riding and climbing on the bike as I intend to do some serious riding as the years go on. The Supersix is an 08, that I found locally it's a pretty sweet bike, but if it doesn't fit i'm going to let it walk.. No point in injuring myself if it's not right.

I guess what I'm waiting for is the answers to hit me like a bus, however that's not occurring even when I'm sitting here for hours trying to compare all these measurements and geometry's..


Once Again I appreciate everyone and their help they've offered.

Thanks,
RR
 
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