Giant Defy - Size

[Glasgow44]

Hi there
I’ve made a few postings about getting my first road bike Anyway, I have narrowed it down to this bike:
http://www.giant-bicycles.com/en-gb/bikes/model/defy.2/24964/90519/#geometry
I have put down a deposit and ordered this in a small frame size. The bike shop I went to in Glasgow has said that a small frame with this bike would be the correct size.
I’m a bit confused because, according to the chart, a small size frame on this bike is only 46.5cm – see below:
http://www.giant-bicycles.com/en-gb/bikes/model/defy.2/24964/90519/#geometry
On other road bikes I have tried for size, it has been a 51cm but I was told that this particular bike has different geometry and that a small (46.5cm) size is correct. I do know that different manufacturers size their bikes differently (cm, inches, S, M, etc).
I’m 5’6 with a 29 in inside leg if that helps.

 

[Milkfloat]

Check out this thread.

https://www.cyclechat.net/threads/giant-defy-sizing-q.176705/

BTW - I vote Small frame.

 

[vickster]

Small has 53cm top tube according to the geometry chart in your link. It certainly won't be too small given your dimensions

Go sit on the bike and preferably ride it before parting with any money

 

[youngoldbloke]

The size chart is useless if they don't tell you what the 46.5 measurement actually measures. Or give a diagram. Is it centre of bottom bracket to top edge of top tube? To centre of top tube? To top of seat tube at saddle clamp? What is the measurement to the point where a virtual horizontal top tube intersects with a virtual extension of the seat tube? (I bet it's around 50/51 cm). Is the top tube measurement the actual or the virtual? It would be wonderful if there was some sort of standard format agreed by bike manufacturers, but for the moment it would be really helpful if they would specify what they are actually measuring.

 

[screenman]

5ft 7in with a 29 inch, I ride a small in that make. I also have a 51cm made to measure steelie.

 

[Dirk]

Giant sizing seems to bear little relationship to convention.
However their frames do seem to have quite a lot of overlap between adjacent sizes.
I'm just under 6'0" and I'm comfortable on my Defy 5 which is a medium size, even though I really should be on a M/L.

 

[bonsaibilly]

All it is is their published sizes are the seat tube measurement whereas most brands published size is the horizontal top tube length. Thus quite explicable that their 46.5 has (roughly) the same geometry/proportions as someone else's 53.

If you are 5.6 then a 53 cm horizontal top tube length sounds like it ought to be about right. Go try outs, though!

BB

 

[screenman]

All it is is their published sizes are the seat tube measurement whereas most brands published size is the horizontal top tube length. Thus quite explicable that their 46.5 has (roughly) the same geometry/proportions as someone else's 53.

If you are 5.6 then a 53 cm horizontal top tube length sounds like it ought to be about right. Go try outs, though!

BB

That is a new one on me, in my history it has always been the seat tube length that was measured.

 

[bonsaibilly]

That is a new one on me, in my history it has always been the seat tube length that was measured.

Not sure how they have their frame stickers this year but they used to have the size eg "L" followed by the "size" in cm which on an L was 55, which is the seat tube length.

You may well be right historically but in my limited experience on modern frames most brands size in cm is effective top tube. BB

 

[Citius]

t whereas most brands published size is the horizontal top tube length

Not sure that's correct. I think most brands still measure seat tube C-T or C-C as their stated size.

 

[screenman]

Not sure how they have their frame stickers this year but they used to have the size eg "L" followed by the "size" in cm which on an L was 55, which is the seat tube length.

You may well be right historically but in my limited experience on modern frames most brands size in cm is effective top tube. BB

I think I may be correct on this one, not sure where your information came from, perhaps you could give us the source so I can do some research, as everything I am finding says seat tube.

 

[bonsaibilly]

Specialized allez. 58 cm. top tube horizontal 582 mm, seat tube 550 mm.

Cube litening. 58 cm. top tube horizontal 58 cm. seat tube 54 cm.

Cannondale synapse. 58 cm. top tube horizontal 58.1. Seat tube 54.5.

Trek emonda. 58 cm. top tube horizontal 57.3. Seat tube 55.3.

Cinelli experience. L. Top tube effective 560 mm. Seat tube 540.

Felt F. 58. Top tube effective 58 cm. seat tube 57.


I'm sure it just varies from brand to brand though. BB

 

[bpsmith]

Giant use their Compact Frame Sizing. Dimensions don't trace across to other bikes at all.

http://www.giant-bicycles.com/en-gb/technology/compactroad/57/

 

[bonsaibilly]

Giant use their Compact Frame Sizing. Dimensions don't trace across to other bikes at all.

http://www.giant-bicycles.com/en-gb/technology/compactroad/57/

That is largely marketing bs now as so many other brands use sloping top tubes too. Giants don't slope significantly more than the other slopists.

The dimensions are way transferable, I don't really get what you mean. Simple cross referencing of the different geometry charts shows which have dimensions similar to a giant defy of a given size, regardless of the number or capital letter on the frame. BB

 

[youngoldbloke]

Giant use their Compact Frame Sizing. Dimensions don't trace across to other bikes at all.

http://www.giant-bicycles.com/en-gb/technology/compactroad/57/

I still have no idea what they are actually measuring - centre to centre or centre to top?