Hello
I am 5’8 but with long legs (34inch inseam) and proportionally shorter torso
Today I have been and sized up a defy (looking to buy an advanced sl1 defy -which seems insanely light and well specced)
Sat on both medium and small
Immediate feeling was the small suited me better but required a lot of seatpost up whereas the medium felt just a little more in reach (both bikes had 90mm stems on)
My gut feeling is to size down to the small

As always any thoughts would be welcome

(Of note went and tried a specialised roubaix expert as well.i felt happier on a 52 frame but the seatpost wouldn’t extend far enough – the 54 felt too long in the reach again)

Small I’d say. I’m the same height as you and got a medium and it was too long for me. I’ve 31″ leg.

Also it’s easier to make a shorter bike longer than the other way round.

Great bikes imo.

Have you had a look at the Giant road bike sizing chart on their website ?

My son is 5ft 5 with a 29 inside leg and fits well on a small. I am 5ft 10 with a 30 inside leg and fit a medium, with a 10mm longer than standard stem

When I looked around for a road bike I looked at the Defy and had a similar dilemma (I’m only 5″ 7″ with a 29″ inseam) and I would have gone for the medium if I had purchased the Giant

I preferred the more stretched out position as I found the small a bit cramped and hunched over

In the end I went for a Cannondale Synapse as it had disc’s and had a bit more flexibilty with tyre sizes – Again, I went on the larger side a chose the 54 frame

I think the general advice is go with what’s closest and the you can then mess around with the final fine tuning with stems – saddle position etc

The alternative would be to have a proper bike fit where they can set you up on the jig and then get the measurements for stack etc You can use this as a shopping list for any potential purchase

Best of luck with making a decision……. I know it’s difficult as when spending proper money you don’t want to buy the wrong thing

I’m about your height, but with a 30in inside leg.

The medium was absolutely spot-on for me, so maybe you should go with your gut instinct on the small?

It’s not a super-sharp handling bike, so getting one a bit long for you might result in a bit of a bargey feeling.

I have a medium, it just felt right straight away and I like a short reach.
Same height as you but a 31″ inside leg.

5ft 9 here and I’ve got a medium, I couldn’t imagine being on a small.

5ft 9.. 29inch leg..

I went for a small defy..

Medium felt too long for me..

Also.. For me.. Extra seatpost poking out.. Bit More flex.. Bit More comfort..

Did they swap stems? I’m 179cm and average proportions and ride a medium with 120 mm stem. I spent a winter riding a Small with a 130 stem, but really needed a 140. For you, I’d definitely go for small and select stem appropriately. You’ll need longer than stock. Giant shops swap them for free.

Great bikes

Looking at the sizing on the geometry chart the difference in reach between med and small is only 4 mm however stack is 21mm. (Toptube lengths differ by 15mm)
If i run a small with a large seatpost length i guess i will incur a significant saddle to stem drop on the small which would be less on the medium?
I’m thinking maybe medium with a shorter stem of 90mm may give me a similar position to that of the small?
My riding is mainly endurance riding with rides 75-100 miles. Currently doing this on a cross bike which has been working out ok but now after some nicer wheels to do this on.

Why is it so tricky!

FWIW my old medium Defy (2014) came with a good amount of steerer and I had to almost fully slam the stem to get the front end grip it needed.

5’51/2″ here with 29″ trouser length inseam, small advanced Pro 2 2016 fits perfectly.

You are between sizes. I would definitely size down. A longer stem puts more weight over the front wheel and the bike will handle better. I don’t think you will have aan issue with saddle to bar drop, the headtube is long enough.

I’m just under 5’8″, 30″ inseam, and I’ve got a medium. I’d be better off with a small, but it was an impulse purchase based on it being in the shop with a big discount on it when I went in to buy a bike for my daughter.