Why do people get bikes too big?

Cube do size small alright - a 56 in their range is more like a 54 when you look at the geometry charts. Having had a loan of a Propel a few years ago I would say M/L is too big for someone at 177cms. Unless you like a comically short seat post that will annoy you every time you look at the bike, and given the horizontal top tube on a Propel that's a reality.

M in Giant road bikes all the way up to 180cms. 'Stretch' the bike by adjusting the finishing kit by all means, but never ride a bike too big for you - it's instantly visible on the road and you'll never be truly comfy.

I'm currently trying to figure out the best bike size for me and feel like I'm in between medium/large and large. Out of curiosity I googled bike fitting and see that it can cost about €220! Seems like crazy money to me. Is that right? Maybe it's only intended for professional cyclists...

The same size could have different geometry so that would normally be the case. Also, different brands measure 'size' in different ways - very annoying.

Can't speak for the Giant - but I'm exactly the same height and inside leg as you. I have a 56cm Cube Attain. No way is a 53m big enough, assuming the Atain fits the same way as whatever Cube you are looking at the 53cm would be too small, so reckon the bike shop is right in this case.

Well I'm an M/L (and have been fitted) on Giant Defy Disc. My TCR Advanced is also M/L, but LBS fitted a shorter stem to match the fitting sheet from the Defy. fwiw, my Topstone is a medium.

All brands and then models are different, but when looking at bikes I tend to start with the stack and reach figures I got from my bike fit (open to be corrected whether that is the correct approach though).

At different points I've owned a Cube Attain, Nuroad and Peleton and all had a very comfortable geometry

Pre-bike fitting can be expensive but not as expensive as the bike you are buying. It's nearly a one off purchase too (based on flixibility), once you do it once you get your stack and reach numbers, can then compare to what ever bike you are looking at buying. Means you buy a bike that will fit and probably be more comfortable and perform better than one that looks cool but doesn't really fit. I used to always be on small frames, done a pre bike fit and now on a M TCR, have bought few bikes since based on the numbers provided and they all fit really well. Much better than the small bikes before. The numbers you get at the pre bike fit also means you can set up the new bike to them, so it's really a pre bike fit and a bike fit.

Stack and reach are the best measurements to use really. Consistent across all bikes, not individual to manufacturer. Take into account stem length, spacer height, bar reach and drop and you should be able to get pretty close to your ideal fit.

Pre bike fit would be one of the things I'd recommend the most.

Personally I went with bikefit studio in North county Dublin. He has a jig bike so the changes can be made very quickly. I found the whole process very good. He doesn't sell any bikes so will just give you info on what bike will fit best based on your numbers. When I went I had an idea of the bike and size I was looking at it so he set it up similar to that and we went through it.

If your a CI member I think there's a voucher in the membership pack for him too. I've never done one with anyone else so can't really compare him to others.

Don't forget seat tube angle. At my height (184 cm) a 1 degree difference in seat tube angle makes a 14 mm difference in the position of the saddle, all other things being equal.

I have a 56cm Attain and have had 2 bike fits, one with Aidan Hammond and one with BikeFit studio. I'm 178cm and they had no issue with my frame size. Lately I have noticed that I am a bit more comfortable with my hands further back on the bars so thinking I could probably use a shorter stem, or that a smaller frame would have suited me, I think I'm right on the cube cutover.

I'm currently looking around at what bikes are out there and trying to figure out what size I should get. I've flipped my stem and there are no spacers left under it so I can't go any lower but if I was to move to a bike with a less endurance based geometry how am I to know if I can fit a lower stack etc?

thanks for the info, I'm 173 and Cube's website says I should go with 53 but the shop are saying 56 (current bike is an M but quite different geometry and I've always felt a bit stretched out on it).

Very good question OP. I don't know why manufacturers recommend such big frames. I just don't get it. I have 2 road bikes. First I bought a few years ago and was totally clueless. 58cm Sensa. I'm 182cm tall. Inside leg is 88cm.

So, ultimately the bike fits. But it's huge. So when I was buying a CAAD12 in 2019 I asked a bike fitter (he fitted me on the Sensa after I bought it) what size to go for. He recommended a 54cm CAAD12. Best recommendation ever. It's perfect. I've a 120mm stem on and it fits perfectly.

Smaller frame is lighter, stiffer, looks better, nice seat post extension. I just don't understand this push for a big frame.

I think Cannondale size big. So I reckon a 54cm Cannondale is equivalent to a 56 Sensa (just a hunch - haven't compared geometry). I should really have been sold a 56cm Sensa,but it doesn't seem to be the done thing

I mean I'm 172cm so simular to you.