how do i measure a frame?

[Black Sheep]

my fiancee just sat on my spare (and slightly too small for me) road bike and found it quite a stretch, as such I doubt she'll be happy to ride it any time soon

I'd like to get her a road bike she's happy to ride but don't know how to measure the frame she's tried in order to figure out what size to look for

she was on points (end of toes) in order to touch the floor and her leg was straight when she put a foot on the pedal at its lowest point.

any advice etc?

 

[roadiewill]

Differenet manufacturers measure differently so bare that in mind, but a lot of frame sizes are measured by the toptube length.
To measure this, go from the centre of the seat post to the centre of the headtube -where the bolt runs down into the headtube that holds the fork in place.

 

[mickle]

The size of a frame is traditionally determined by measuring the distance from the centre of the BB axle to the top of the seat tube.

 

[mickle]

.... a lot of frame sizes are measured by the toptube length.

Really?

 

[Steve Austin]

The size of a frame is traditionally determined by measuring the distance from the centre of the BB axle to the top of the seat tube.

yep. What my esteemed colleague said

 

[roadiewill]

Really?

both my bikes are...

 

[Black Sheep]

thought it proberbly was TT to BB same as mountain bikes, although mountain bikes are still in inches

 

[Steve Austin]

Will, specialized measure their bikes by seatpost size, like every other manufacturer. The toptube measure is important, and arguably more important on roadbikes as different companies have differing geometries, but all bikes are measured at the seatpost first.

 

[roadiewill]

Will, specialized measure their bikes by seatpost size, like every other manufacturer. The toptube measure is important, and arguably more important on roadbikes as different companies have differing geometries, but all bikes are measured at the seatpost first.

Strange... then my specialized has a 56 cm seatube and 56.5 centimtre toptube yet by Giant SCR3 has a 58cm seatube and a 56.5 top tube.

why are they different on the giant?

 

[Steve Austin]

Because different companies have different geometries as they have different ideas about how bikes work.

I know what you mean though. On conventional horizontal tubed frames, all bikes were measured by seatube. since Compact frames (and MTB's) seat tubes mean increasingly little as the seatube could be extremely short and mean little as to the accurate size of a bike

 

[roadiewill]

so that doesnt mean that my specialized is too small, as they both have the same toptube lenghth?

 

[Steve Austin]

probably

 

[Steve Austin]

How you getting on with that 3000 miles btw?

 

[roadiewill]

come on serious now!

urm so far its 330miles this year

 

[Gary D]

It would be well worth a trip out to Epic Cycles near Tenbury Wells if you are that side of Brum. http://www.epic-cycles.co.uk/

Great selection of bikes from different manufacturers and they seem very knowledgeable are are prepared to spend a good while talking to you. If you go in the week, I would imagine it would be very quiet as well - they are stuck in the middle of nowhere!!

They have a fitting jig to get you/your fiance sized up and will let you test ride on the local quiet lanes apparently.

Good luck!
Gary.