I’m looking at a new bike – probably a 29inch full bouncer Whyte. I’m 6foot tall. The Medium is sized roughly at 5foot8 – 6 foot and the large at 6foot +.
I’m rubbish at telling if a bike is any good in the shop or even with a couple of rides. Any thoughts on which one to go for?

What’s your inside leg in cms and what’s your reach shoulder to hand.
Then compare to that of the geometry figures on Whyte’s site for that model.

Personally I would say a large.
Having owned a Whyte hardtail, they come up a bit small, even a large but not sure on the newer full suss range of theirs.

To start with I tend to look at Seat tube length and Horizontal TT for sit down pedalling. And then Stack and Reach for stand up riding. I get out the tape measure and compare it to my bike and friend’s bikes. And then adjust my saddle to the same height as the new bike would be and then using a longer or shorter stem I set the bars to the length they’d be with the new bikes reach. Not to ride like that, just to see if it would be too tall/short or long/short as a reference.

This helps to start with as I find it hard to picture the new geometry in my head.
Do you want a bike the same as yours or longer /shorter/taller/lower? Decide what you think you’d like to change (or not) and then try to get a spin on them (or a demo if you can).

Then decide if you want shorter stays (easier to manual) vs slightly longer/more stable at speed – usually there’s only about 10-15mm in it. Slacker HA, etc.

I’m 5’10 , 31 inside leg and +4 on the ape index . Rode the t-129 2015 model and the large was spot on , the medium felt cramped .

height, arms, torso etc all important. A good bike shop with the bike should be able to advise better than the internet…

I’m rubbish at telling if a bike is any good in the shop or even with a couple of rides.

Surely it doesn’t matter then. Just get the one that looks best 😀

I’m 99.9% sure you’ll prefer the large.

I’m bang on 6ft (183cm) and had a go on a large Whyte T-129 recently (the 2015 model) and if anything found it a little small compared to current sizing trends.

No way would you be on a medium Whyte at 6ft. I think their size chart recommends medium up to 5ft 10″.