Sizing??

[gavin77]

Ive looked at many posts re sizing and i feel more confused than when i started oout!
Im looking to buy my first rad bike for fitness only and have done a lot of reading. I have also popped into independents in Hull (didn't appear that interested) so im here. Ive been scouring toe £750-£1000 market for bikes and have looked at all recommendations. I like the cannondale synapse 105, the focus cayo 1.0 and caad8 105. Id prefer something fairly comfortable. Im only 5ft 6in so would like advice on frame size. do you think 51cm frame will be ok??

any assistance will be greatly appreciated. Like i said, ive been into independents but they havent been much help.

[gavin77]

just bought the caad8 105 (51cm) so will see when it arrives.

[Darth Weasel]

I reckon that sounds about right if your body proportions are 'normal', but the only way to be sure is to try it out. Nice looking bike.

[gavin77]

I reckon that sounds about right if your body proportions are 'normal', but the only way to be sure is to try it out. Nice looking bike.

Cheers Darth

[Fevmeister]

Sounds about right

[gavin77]

thanks. feel relieved now phew

[Bally]

Be careful with sizes and how they are quoted. They are better based on the effective top tube length (ETT) which is the horizontal dimension from the centre of the headtube to the centre of the seattube (and not measured along the actual toptube which may be sloping or horizontal). Generally brands quote and use the dimension from the centre of the bottom bracket, up the seattube to the centre of the toptube and seattube junction and others to the very top of the seattube which may have an extended section (I don't mean integrated seatpost here) so you need to study the geometry chart for the brand.
.
The ETT and seattube size don’t always correlate proportionally. I have a quoted 52cm frame with an ETT of 525mm and one 50cm (called small by Boardman bikes) which has a 540mm ETT. I also had a Giant which have a sloping TT and that was quoted as a 46.5cm and had a 530mm ETT.
.
As the sizes increase the headtube size will usually increase, depending on how high you want your bars and the bar to saddle relationship. You need to consider the suggested spacer limit is 40mm. Some brands offer a ‘Pro’ race fit and an ‘Endurance’ sportive fit where HT sizes vary considerably along with ST and HT angles.
.
The ETT usually changes between 10 to 20mm per size step depending just how many sizes the manufacturer produces, you then combine that with the stem provided and total the reach.
.
The different sizes may have different seattube laybacks and head and seat tube angles which will affect setting the saddle behind the bottom bracket setting and this needs to be within the saddle rail clamping zone.
.
I am 5'-7" and inseam (crotch to floor) of 31¼ inches (1.7m/796mm) and have frames with an ETT of 530mm and a 100mm Stem and ETT of 540mm and a 90mm stem. This is tried and tested with me and I have in the past had a 'Bike-Fit' which backed up what I was riding. I have also ridden a 520 ETT and just used a 110mm Stem to replicate the dimension.
.
The Stem length and angle and shifter type and angle can affect the set up and aesthetic proportions and that is personal choice.

[gavin77]

interesting bally. worried again now haha

cheers for the info