[Closed] Bird Aeris 145 – help me choose the size!

My son is 6ft exactly, has a long with a 35mm stem 780 bars and he loves it!  He goes really fast too.. its a great bike, particularly downhill, don't over stress, you'll adapt to either.

I rode a couple at Meetup, only very briefly. I'd say large just because ML "Feels like my current bike (large nukeproof mega from 2011"

The 'point' of the new, longer, slacker bikes is that they're longer and slacker and that's meant to be good. The danger when test riding bikes is (and I'm sure you already know this) is that familiar is comfortable and comfortable feels better/faster.

If you want a better new bike than it has to feel different to your current one, and you hope will be better/faster once you're used to it.

Like you (but shorter at 5' 10") I sat on a Medium and it felt good, because it felt just like my medium Tracer, the ML felt a bit long and like I was more of a passenger whilst it did it's thing, the Bird Lad's opinion was absolute though, ML, give it a few rides to get used to it and you'll be faster.

This is the feedback i need to hear 😀

From what you’ve said I’m inclined to say large. I’m 5’9 with a 31 or 32” inside leg (I forget which), but short arms. I went ML on Birds recommendation.

I think if you want poppy and easy to manual go smaller but for everything else larger is probably better.

I still wonder what the medium would have been like - but equally I’m faster on the aeris than my last fs bike basically everywhere - I was fitter in 2015 when I had my old bike and riding more han I do now by miles. Yet I think I’ve only got 2 Strava segmentsnleft on my old bike where hey are quicker than the Aeris - both uk and down. The only segments left are one flat but twisty singletrack section and one steepish downhill with very tight corners that the Aeris is tight to get round due to the length.

Interesting your comment on the AM9 - I’d really like a go on one to see how they compare to the 145. Mines now an LT as I upgraded the linkage. I think it’s a better bike at 160 than 145.

I'm almost identically sized to you (maybe an inch shorter in the leg) and would go ML unless that seatpost is utterly ridiculous, even with a 170mm dropper. I own a L Aeris 1.5 at the mo and spent a long time working out which was better - a M or a L. The L was definitely the better fit, but something a tiny bit shorter would be almost ideal.

^

I'm the exact same height as you. 33" inside leg. Have an ML.

For me, any bigger would be unwieldy. The ML is long enough to be comfortable and small enough to be manouevrable.

I'll admit it's borderline. No matter what make/model, that 6' height is an issue...

I was in the same predicament as you op, 6ft on the nose, coming from a large 2011 devinci Dixon, both ML an L were heaps longer than what I'd been riding! I went for the L after chatting with the Bird boys and have no regrets. It took a few rides to get acquainted with the handling, but then, wow!! so fast and stable, and feels fine in the tight n techy stuff too. The only area I feel it's harder work is manuals, I'm running a 32mm stem and 20mm rise bars and would recommend either 30mm + rise bars or as I've done, chucked a couple of extra spacers in to raise up the front end a bit, made a huge difference. All in, a flipping awesome bike, you'll love it!

I think that is four to two for large at the moment. The brexit of bike size polls!

When i rode the ML, althought it didn't feel long at all but it's actually about 20mm -30mmof so longer than my mega. When i rode it i did notice that when going up the fireroads i was a bit perched on the back of the saddle, whereas on the large i was in a more proper saddle position (but my arms didn't have much of bend in them).

When i say the saddle was silly on the ml, it was really the height of it above the bars - it looks like the bike is too small - my long legs i guess! The higher seat tube on the large makes it look less silly.

So conflicted!

I was in the same predicament, and went for the ML-much against Bens advice, should have gone with the L. The 145 is an enduro gnarrpoon, as such go for the large, when you pick up some speed (which is where this bike shines) you will like that added stability.

I´d have a chat with the guys at the nest, after all they designed, tested and polished those bikes.

I did .They think I could ride either 😁

I’m test riding a L and XL tomorrow but I’m 6’2” with long arms and legs. Intrigued to find out how they size up.

They think I could ride either

That's what they said to my friend, who is the same height as me at 5'7". We demo'd both the M and ML, and it's true both bikes fitted (the seat to bars can easily be made the same between two sizes). She went for the ML for the extra stability at speed and for the steep stuff. I ride a M in the old model Aeris and would equally be torn between a M and ML, though I think I'd go for the ML with a short (30mm) stem, so at 6' I'd definitely be looking at the L. The only thing that would put me off sizing up is the seat tube length, and that's a non issue as the Birds have short seat tubes compared to the reach, I reckon ideally seat tube shorter than reach by at least 30mm.

“When i say the saddle was silly on the ml, it was really the height of it above the bars – it looks like the bike is too small – my long legs i guess! The higher seat tube on the large makes it look less silly.”

You should probably have raised your bars then - these longer bikes seem to work better with higher bars, especially if you have long legs!

I’m 3.5cm shorter than you, same leg length and my full-sus (which is as low, and slacker than the Aeris 145) is about the same reach as a small Aeris. 810mm bars and 50mm stem, never feels cramped, super stable because of the sub 64 deg head angle.

I'm 5'10" and a 32 inside leg. I contacted Bird and explained that I was torn between the ML and the L and was advised to go large, with a super short stem. This was because my bike at the time was a Mondraker Foxy XR large with a long reach so the geometry would be very similar. They were spot on! The L is an absolute dream to ride for me. Its horses for courses however, but I'd say go large.

I’m 6.2/3, so between large and XL. I went XL - tried both and expected the large (which like you was longer reach than the bike I was coming from) to be the one, but for me the XL was hands down better. I also felt more comfortable when hitting (small) jumps on it than the large size.

I’d go for the longer bike - worst case you hate it (unlikely) you can get one of those ultra short stems to take 20/30 mom off the reach

I'm 179.5 cm, and ride an ml am9. I've got short legs and long upper body - opposite to op. It doesn't feel too big in any way.

Ok - definitely erring towards the Large now. In theory I've got longish arms as well - i'm a climber so i know i've got a +3 inch ape index (i.e. my arm span is 3 inches longer than my height).

I'd not really thought about the rise of the bars - all the bikes i have ridden seem to have those on trend almost flat riser bars, whereas my existing bikes have a 20-30mm rise on them. Perhaps 35mm stem + 25mm rise on the bars is the trick?

With those long arms, you should have no problem with reach. Also have in mind with the aeris your bike position has to be quite neutral, if you pull you weight back on something steep your front wheel will wash out.

Also, I'm surprised you didn't get on with the AM9, I haven't tried it since I do not want to lust for another bike, but the more I ride the 145, the more I think 29er wheels would be perfect for that geometry.

I'm currently riding a 26er so the 29er was quite different. It's not that I didn't like the am9, more that i preferred the Aeris. The am9 felt fast and like you could roll over anything, but upon reviewing the strava, it was actually quite a bit slower than the aeris on the same trails - I also ****ted my foot into quite a few tree stumps!

is the BB in the AM9 any lower than the 145? I have a 120 (5'10" & ML for the record) and it took me a few rides to adjust to the low bottom bracket height so maybe you were just unlucky with stumps on the AM9.

Whichever you go for I would be inclined to trust the advice from Bird on sizing and would say go larger if in doubt.

“is the BB in the AM9 any lower than the 145?”

Yes, a whole 4mm! (if the AM9 has a 150 fork and the 145 a 160, and they’re wearing the same profile tyres).

4mm! I've become MBR magazine 😀