Road / Gravel bike sizing.

Interested to hear peoples experience with sizes and recomended size guides.

It seems to vary a lot between manufactures and cant work out why. Maybe a particular part of the geometry or something else.

My current road bike is old geometry with a 530mm top tube (540mm effective top tube). Always found it a bit too long so was looking at geo charts and size guides. Some brands recommend an effective TT of 515 and others up to 560 with similar stack and reach so wondering what else could be affecting the size. Or maybe manufactures just vary a lot with what they recommend. Anoyingly im right between sizes in the bikes I like so need to find some to try.

Generally I complete ignore manuf’s guides and just look at the geo using one of the comparison sites and compare the new bike vs my existing ones.

https://bikeinsights.com/

https://geometrygeeks.bike/

Ive been using geometry geeks a lot but its tricky when my old bike doesnt exist on there. Some measurement are pretty easy to do but angles wont be that acurate.

I’m 5’10” and go with a ML giant tcr road bike, and a large santa cruz mountainbike and trek ebike.

Im 164cm and looking at a Giant Revolt. Acording to their size guide it should be fine but it is longer than most other brands suggested size for me. Unfortunately the local shop doesnt have one in stock for me to try. It comes with a 60mm stem so theres not much room for adjustment if it is too long.

As has already been said, sizing between brands is a bit of a lottery. I’m a M/L on Giant, a 56 on Specialized. Just bought a BMC Roadmachine and I’m on a 56 there. When i was looking for the BMC i looked at some Scott road bikes, and i was more a medium in their sizes. (5’10, 34 leg)