question on frame size

trevtherev

Can I presume that if I fit a 50cm Defy 1 (described as a medium) and a 50cm orbea then the correct frame size on the Kenesis racelight tk is a 51cm. I know this may seem a silly question but there is nowhere in the Bristol area that I can tryout the racelight ( the closest is near Worcester) and as this is the bike I am really after on Dec 1st is this a fair assumption re frame sizes?

rapid_uphill

were are measuring it from would help c-t or c-c?

trevtherev

measurement from centre of crank spindle to top of top tube

whyamihere

Top tube length is more important.

trevtherev

I have found the measurements for the Kenesis frame on the web site, so to measure the top frame of my present old road bike I presume I take the measurement from the top of the top tube across to the intersection with the head tube....is this correct?

System_1

The most important measurement is effective or horizontal top tube length, this determines your reach to the bars which is the most important measurement for comfort. Leg length is easilly compensated for by moving the seatpost up and down, and standover height is almost redundant on sloping top tube frames unless you're buying something far too big.

The amount of slope to the top tube on different bikes can effect the actual length too much for it to be a useful comparison of reach between models. Instead measure from the centre of the headtube and across horizontally to the point where the seat tube would join if it wasn't sloping (normally the centre of the seatpost).

Looking at the geometry charts for the Defy and the Kinesis though, the 50cm Giant has a 54.5 effective top tube and the 51cm Kinesis a 54.4, so almost identical.

trevtherev

thanks for that system looks like the 51cm for me but to be sure I will take a trip to Epic and check out the 51cm before Dec 1, which is when are CTW scheme starts again