I am eyeing up a Bird Aeris frame as my new bike. I’ve not ridden a modern geometry bike before- my current bike is a large Stumpjumper Evo Carbon (for sale if there are any 26″ fans out there) in large with a 585ish top tube and a 60mm stem. I am 5’10, though I’d be 5’11 if I ever stood up straight and my arms are unusually long. What size do we reckon I should go for? My first thoughts are to go for a large but the TT would be at lest two inches longer than my current bike.

For reference I ride the peak every week and at least a dozen big mountains a year in the lakes and Scotland. I’d demo one but Swinley seems to be the only place to try one and it’s so far away from The North and so different to my usual trails that it won’t really work.

Also, anyone own a black one and care to share a photo? Yellow would be my second choice and it’s in stock now, but I feel black would look better and not be chronically unfashionable in two years. That’d be a wait until February though (but I’d be waiting til Christmas for all the bits to build it anyway!)

I think it’ll come with a 35mm stem, that makes the reach on a Large almost identical to your current bike with it’s 60mm stem. I reckon you’ll dwarf a medium frame. There’s an XL and a Small (!) in Kendal that you can try for size comparison(PM me).

I have a 40mm stem to go on it. With 780 bars.

Definitely not considering a small! Thanks for the offer though.

I have searched the forum before posting and it seems that most 5’10 people have gone for a medium. Which sounds wrong, hence asking. I’ve not looked at a medium bike for years!

I’m 6’2″ and ride large bikes, but the large Aeris I demoed felt too small, if that helps!

The geometry of the xl better matches that of my large Horsethief.

I’m sure a large stumpy has a ett of around 620mm

The Aeris is one of the biggest bikes out there for its size (as in S/M/L). Theres only a couple bigger in the same class. That said, of course with a 40mm stem that does change things up a bit. Comparably to your old Specialized the cockpit on an Aeris will be 35mm longer running your stem. More than a full size jump… So you need to be sure you want that. That said, I think it sounds like your old bike was too small for you. I should also say though that the ETT on that Stumpy you quote does sound a bit short as mentioned… so maybe its going to be closer after all.

You’re both right, I’d read the medium tt size on their website. It’s actual 617mm. Near enough the same as a medium Bird. I take it then that going for a large Aeris, 20mm longer, will be perfect?

If that’s the case what colour do I pick?

No, no I can’t think for myself…

how does the reach compare? reach can be different on bike with the same ETT depending on the seat angle.

445 on the Stumpy, 449 on the medium Aeris, 467 on the large.

so you’ll be needing a shorter stem on the large Aeris like a 35/40mm

Blick!

Medium with 35mm stem and 760 bars. Not sure why they look so weird. RF Atlas ones they be. Think it’s the angle I took it from.

How tall are you funkweasel?

5 9 and a bit and on a medium as that’s what the chaps at bird recommended , very happy with it . Previous bike was a large stumpy still loving mine after 5 months and apart from tyres have made no changes to the build as it just felt right from the start

One of my riding buddies is the same height as you (ish) and I *think* is on a large, but it could be a medium. It’s DEFINITELY black, and looks ace in that colour.

If he’s out in the Peak any time soon (we were out last weekend so might not be for a bit) I’m sure you’d be welcome to have a sit on it.

How tall are you funkweasel?

5’9 and medium fits me perfectly. Not that I tried any other sizes.
moonsaballoon – if you haven’t already, and you’re running tubeless… top up/replace the sealant. Mine had gone off after 4-5 and a bit months. Oh you changed the tyres… you might be ok.

5’10” on a medium with 40mm stem here. What’s surprising, is that the longer I’ve owned it, the more glad I am that I went medium, and the more relieved I am that I didn’t go large.

It’s not exactly a tight-turning bike anyway, even in a medium (it is noticeably longer and slower turning that my mate’s cube stereo in Large). The figures for the medium Aeris still equate to masses of straight line stability and roomy reach. I just can’t foresee a situation (in my riding) where I’d crave more stability or room. What I do know though, is that if I had a Large I would crave more manoeuvrability in turns. Even on the medium I do sometimes!

There’s not much in it, but the Medium frame is also going to be slightly stiffer and lighter, with a shorter seat tube for fitting in a 150mm dropper.

But it’s a personal thing. Either bike would fit you.