Need Sizing Help

[ac137]

I went and put a deposit on a Supersix 5, im about 5'8 1/2" - 5'9" and have an inseam of approximately 32" the guy at the shop got a 54 set up on the trainer and though it was a bit big for me. He then got me on a 52 and said it was a better fit although if I wanted I could get a longer stem.

When I was on the 54 I could feel me self rocking in the saddle a little and having to stretch a bit when I got the the bottom of my peddle stroke.

Main reason im posting is to ask others opinions on the size as most of the research I have done made me think I was a 54 and I was also thinking would dropping the saddle a little help with the peddling?

Cheers

 

[redbruce]

I went and put a deposit on a Supersix 5, im about 5'8 1/2" - 5'9" and have an inseam of approximately 32" the guy at the shop got a 54 set up on the trainer and though it was a bit big for me. He then got me on a 52 and said it was a better fit although if I wanted I could get a longer stem.

When I was on the 54 I could feel me self rocking in the saddle a little and having to stretch a bit when I got the the bottom of my peddle stroke.

Main reason im posting is to ask others opinions on the size as most of the research I have done made me think I was a 54 and I was also thinking would dropping the saddle a little help with the peddling?

Cheers

Rocking is because the seat is too high. Not sure why the bike shop didn't adjust it for you (which would make me question their advice somewhat).

Focus on the correct top tube length rather than seat tube length (which the "size" refers to).

So you are 175cm, same as my son.

He rides a 55.5cm top tube, with a 100mm stem, pretty normal for that height (but would probably be a 53-54 if racing).

From the Cannondale site:

http://www.cannondale.com/aus/2013/...persix/super-six-sm-3-ultegra-double-crankset

With a 53.4 cm TT unless racing, the 52 is definitely on the small side for you. The stem length required to fit you properly would be over 120mm.

The 54 looks better at 54.5 with maybe a 110 stem.

Torso and arm length are significant components that influence sizing. The type of riding you do (in addition to personal fit preference) also influences sizing.

This Giant site shows some examples (TCR is their competition series, OCR their endurance (more upright position) series):

http://www.giant-road-bike.com/index.php/bike-fitting-issues/

 

[0psi]

Horses for courses, I personally think you'd be fine on either. The 52 with a 120ish stem or the 54 with a 100-110 stem.

I'm 176 and ride a 540 top tube with a 100m stem. However, have a lot of reach on the bars I'm using and an enormous saddle to handle bar drop.

Just for shits and giggles here are Mark Cavnedish's measurements as he's the only guy I know that's close to our height. Keep in mind he's a pro rider and what works for the pros doesn't always work for us.

Rider's height: 1.75m/ 5ft 9in
•Saddle height, from BB (c-t): 680mm
•Saddle setback: 30mm
•Seat tube length, c-t: 485mm
•Tip of saddle nose to C of bars (next to stem): 545mm
•Saddle-to-bar drop (vertical): 90mm
•Head tube length: 120mm
•Top tube length: 535mm

Edit: Tommy Voeckler is also 1.75cm and rides a 530 Top Tube.

 

[The Duckmeister]

Rider's height: 1.75m/ 5ft 9in
•Saddle height, from BB (c-t): 680mm

Not digging specifically at you, but that is a stupid & pointless measurement. Nobody pedals from the BB centre, but from the pedal, funnily enough, and measuring from the BB centre completely fails to account for leg & crank lengths.

 

[RB 24]

Not digging specifically at you, but that is a stupid & pointless measurement. Nobody pedals from the BB centre, but from the pedal, funnily enough, and measuring from the BB centre completely fails to account for leg & crank lengths.

but wouldnt that be the same if I had similar length cranks and same pedals if I was to ride another bike? I have used the c/o bb to sadlle height before and it has been fine..

back to the post..

I have a long leg sizing and short torso and the 54caad was just too cramped. Went for a large boardman with a 570tt and a 110 stem. Was more closely matched to the M/L giant I was moving off that felt more comfortable.

but in all things fair and equal we wont be riding the bike, you will. Go to other dealers etc and try a few more. I would be sad to see you spend some coin on something not right. Ebay loves people like that.

 

[ac137]

I've decided that It's probably best to go back and test both out again, so I'm going to try and make a trip tomorrow.

What are the main things I should look out for or should I go with the size that feels more comfortable?

Cheers

 

[redbruce]

should I go with the size that feels more comfortable?

Cheers

Yes but that can be achieved a number of ways in a static test. Stem length and weight distribution affects ride characteristics.

If possible see if they will let you ride around the block, or at least in the car park, down the road, anything active.

Aim for a size that is comfortable with around a 100-110mm stem and the seat clamped in the middle of the rails (your back should be around 45degrees with relaxed arm position on the hoods). That gives some scope for fine tuning later.

If you are a recreational rider, particularly if planning on longer endurance rides, a drop of around 50 -60mm from the seat height to the top of the bars is desirable. Older aged, less flexible and/or back/neck/shoulder probs may require less.

Race fitting needs professional advice.

 

[ac137]

Okay so I went back to the shop and spoke with the guy that served me and the owner. They explained to me about why they thought that the 52 was a better fit, the main reason was that when they were doing the fit that my knee was about an inch to an inch and a half behind the pedal spindle with the crank horizontal, when the saddle was in the neutral position and they said that for this reason I should go down a size as it would be harder to make the 54 fit.

Also I did feel comfortable on both bikes, maybe a touch stretched on the 54 (could it be the fact that I have broad shoulders, therefore shorter arms in comparison?) and I don’t mind the racier position of the 52 as I’m young and relatively flexible.

Now just have to finish paying it off then hit the road and get some km’s under the pedals.

 

[The Duckmeister]

but wouldnt that be the same if I had similar length cranks and same pedals if I was to ride another bike? I have used the c/o bb to sadlle height before and it has been fine..

If you're sure the cranks are the same length then it's passable, but it doesn't take away the fact that you're relying on a certain degree of guesswork in judging the BB centre. Working from the pedal top gives you a stable base to measure from. And it's not unheard of for people who should know better to not check for different crank lengths.....

 

[0psi]

but it doesn't take away the fact that you're relying on a certain degree of guesswork in judging the BB centre. Working from the pedal top gives you a stable base to measure from.

All pro mechanics I know only record BB to saddle measurement mainly because this is the easiest, quickest and most accurate way to replicate a setup if you need to change a seatpost, setup a second bike, rebuild bikes etc. Pedals move, BB doesn't. The BB to saddle measurement will never change for a given rider unless they change crank length, shoe or pedal. And for what it's worth I don't know anyone that actually does centre of BB to saddle, it's usually a specific point on the BB like the top of the axle or bottom edge of a bolt etc.

It is a pointless measurement when trying to determine saddle height for another rider but so is any other measurement including pedal to saddle as there are just too many variables including things like pedal and shoe choice. As an example pedal to saddle height will vary massively for the same rider if he or she were to use Speedplays with Speedplay specific Bonts or Look pedals with an entry level plastic soled shoe.

 

[C Dunlop]

It takes more than a rider's height to determine the size frame they will be on. I have a really long torso but short ams and legs. Someone of my height but with long legs and equally short arms could be on a smaller frame size.

It sounds like you are getting good service from your dealer, so I would trust their opinion.

Cannondale CAAD/Supersix/Evos are relatively long and low bikes. I ride a 54 (at 6ft) when I fit better, for example, on a 56cm Trek. FWIW I have sold cannondales for many years and at your height I would sit you on the 54 and 52, but my intuition would tell me that the 52 would be a better fit straight away.

The sizing that professional bike riders use, or any other bike rider for that matter, should have absolutely no bearing on what size bike you ride.

Find a dealer you like and trust. If you are unsure of their advice, ask questions (like you have). If you are unhappy, shop around.

You'll learn more from a good bike shop than you will from the whole of the internet.

 

[ac137]

Yeah I guess it is what they do for a living so they probably know whats best...

The guys at the shop were great and had no problem with me coming back down for a second look, and giving me the explanation as to why the 52 was a better fit, so +1 to them. The guy also gave me that example, that on a Trek I would definitely be a 54, and same with a Specialized.