too big?

i just got cannondale six 13 Dura-Ace given to me it is 56cm im 5ft 8-9in inseem 30-31 is it too big and if so what will be the effects?

First can you straddle the bike with both feet on the ground and not have to sit on the top tube? If not you could have trouble stopping safely at traffic lights and such. But assuming you have enough standover height the real question is whether the bike is too long for you. Can you comfortably reach the bars when riding on the tops, the brake hoods and in the drops. If not can you get the fit you need with a shorter stem and or shallow drop short reach bars?

56cm isn't extremely tall for your height and inseam, but I personally prefer smaller frames for the way they feel. I'm 5'10" with a 32" inseam and I ride a 54cm bike with a 135mm stem. I could definitely ride and have ridden 56cm and even 57cm bikes but I like them smaller.

If you can safely clear the top tube then the bike will probably work for you with a shorter stem and lower saddle height.

Good luck,
-Dave

I can reach the handlebars fairly comfortably. but think it may be the seat position, do you know how to position the seat forwards-backwards.

Thank You

Only way to really tell is have a fit person take a look at you on the bike, in a stationary trainer. Inseam means little with regards to bike size, femur length means lots since it determines proper seat tube angle and proper fore-aft position. If the seattube angle and top tube length is proper, the standover generally takes care of itself but have a fit person take a look, if possible.

First question, are you a racer or a casual rider?

If a casual rider, you are fine unless something hurts when you ride.

Im a racer, when i ride it my legs get that tight feeling more easily like wheyour going really hard but im not going hard and my knees get a little soar.

I should have read the initial message... obviously with your style of bike you are more likely to be a racer, but now that is crystal clear.

If you hurt, racer or casual, you definitely need to adjust something. Whether or not the bike is the wrong size is still not answered.

Do you still have access to your old bike?

If so, you should try to get all appropriate measurements to see if you can get the new bike adjusted to be the same as the old bike. This should get you into the right ballpark.

Seat height is obvious (seat to pedal at bottom of stroke).

Is the crank the same length? The crank length difference could lead to a knee issue. Are you using your same pedals? Also, using too high a gear could increase knee pressure.

Amount of seat set back. Depending on seat tube angle, you may have to slide the seat forward or backward to get it right.

Now for the cockpit. Nose of saddle to handlebar (where it meets the stem). If this isn't right, how far off is it?

Saddle to bar drop. Is it more or less? How much?

The above two elements if you need to tweak them might be able to be adjusted by switching stems. If they are too far off, then your bike may be the wrong size.

Differences in bar? Reach/drop?

If any of these things can not be adjusted to get you into the same ballpark as your old bike, or you haven't grown enough that you need this bike to be bigger, then the frame may be the wrong size. Don't give up without at least trying to adjust.

Do you have a coach, a shop or team mates that can help you with fitting issues?

Discomfort can mean an adjustment is needed. Only if the adjustment is beyond the scope for the bike's geometry is it an issue of bike size.

Thank you, i will try thoes adjustments

i'm the same height and inseam as you and i just bought a 52cm frame and it fits like a dream. i was first riding a 55cm and was too large (had the top bar in my man parts). lbs lbs lbs

Since you got it for free, I have an old rusty steel bike (54cm) with crappy ancient modolo and simplex parts that'll fit you much better, how about we swap?

I agree if you are saying you are 5'8" or 5'9" something with a 53 -54 top tube will be better. Everyone is built differently but I would venture to say this bike is too big.
This will show up on longer ride when you are out of position. Most stems are 90mm and up but there are a few companies that make a 70mm stem.
Changing the stem and adjusting the seat may help if you are determined to keep the bike. Also check the crank length. I would guess you need a 170. The drop bar width can also be an issue.
If all this seems a bit much disregard and go see someone you trust at a bike shop.
They should be able to help you more easily and accurately

__________________
Dope,when training and talent just aren't enough.

I'm 5'10", when I went to the BS they took some measurements and basically the bike I need is a 54 by 56(top tube) I got a standard 55 by 55 frame and installed a longer stem and the bike fits fine. I had a 52 frame that felt small.