Advice on sizing Principia Rex

[cflock]

I have my rex e up for sale on eBay and have it advertised as 58cm.

This is from the top of the seat tube to the centre of the bottom bracket. However, looking at the stand-over height of the bike (80cm) it matches up with a 55cm model.

Should I be measuring to top of top tube instead?

 

[cflock]

Re:

Excuse the laundry drying in the background haha

 

[klunkrider]

Re:

“Should I be measuring to top of top tube instead?”

Doubt it.

Centre of bb to top of seattube or to the centre of toptube are the ways I’ve seen frames measured never to the top of the toptube.

 

[mattr]

Remove the confusion use dimension b which is the effective top tube length center to center

 

[cflock]

Thanks chaps makes sense

 

[Fatal Swan]

You can use the listed geometry you're using to find out what size frame it is straightforwardly enough, you just need to be sure exactly what measurement what each letter corresponds to:

A is the seat tube measurement from centre of BB to top of seat tube, so your 58cm measurement matches the size 55 REXe. Then since J is the standover height, the 801mm of the size 55 again matches your measurement of 80cm. An easy way of confirming would be to take the head tube measurement (H) since that differs from each frame size to the next plus it's easy to get an accurate measure of that.

That said, the most useful measurement to a future buyer will be the top tube length as the other posters have said, but then once you know the size you can take that from the geometry specs.