Bird Aeris owners thread

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flag R-M-R
Posted: Mar 5, 2020 at 21:19 Quote
bikefuturist wrote:
just my personal preference of finding it more fun with relatively smaller frame size.

Different bikes for different riders and different trails.


bikefuturist wrote:
also the "pro fit" seems to favour small'ish bikes

The difference between pro riders and normal folks is vast, so it may not be appropriate to use their set-ups as references for ours. Pros tend to have outstanding mobility on the bike - picture a BMX rider - compared to a more static position from typical riders. If you have the strength and skill to control a smaller bike, it may offer a greater range of motion.


colourofsound wrote:
In my humble and inexperienced opinion, all increased bike sizing has done is allow people to find the right size for them.

It's nice to have a variety of options available. We can now choose anything from a compact, traditional fit to super long. The one area that hasn't been explored is a very long reach with a steeper head-tube angle. I think this could work for certain applications.
flag drwavey
Posted: Mar 6, 2020 at 4:54 Quote
colourofsound wrote:
I’m the same height as you and Bird’s larges are too big for me. 5’11” is a cursed height though - forever on the fence!

I'm 5'10.5" and the ML AM9 with 475mm reach is good for me (all Bird ML's work for me, as did the M in the Aeris Mk 1).

Personally I like being between sizes because I get to choose between chuck-ability and plough-ability depending on the type of bike and the typical riding I'll do on it. I have a Ragley Mmmbop (hardtail) for the winter mud. Toyed around with M or L for a while and chose M with 440mm reach for chuck-ability. The effective seat tube angle on the AM9 is 76deg, while on the Mmmbop it's 74deg, making the effective top tube length 630mm on the ML AM9 (and on all Bird's) and 620mm on the M Mmmbop, so the cockpit 'fit' works on both. Totally different bikes for different purposes and both work fine.
flag Arierep
Posted: Mar 6, 2020 at 5:56 Quote
I believe we can objectively consider that bikes 3 or so years ago were too short relative to their seat tube lengths.
The current trend created not only a longer base line across sizes, which I think is good, but also opened up one's options. Look at Specialized with their "S" size system, you can pretty much select any reach you want, even if you're on the shorter side.

Personally, my last bikes had, in chronological order, reaches of 450mm, 510mm (hardtail), 500mm and now 480mm. I'm 184cm tall, 195cm arm span (I know, right?).
The 510mm one worked because, being a hardtail, it took weight off your legs, but was very tiresome. The 500mm felt fantastic on a straight line and climbing, but was not as great riding blind and fast on rough natural trails. It was also hard to ride on flat pedals.
After much experimentation I think 475-490 seems to be my sweet spot
flag R-M-R
Posted: Mar 6, 2020 at 10:55 Quote
Arierep wrote:
I believe we can objectively consider that bikes 3 or so years ago were too short relative to their seat tube lengths.

Depends how you look at it. We could say bikes from a few years ago (and earlier, obviously) had overly long seat-tubes, which prevented us from sizing up to get the reach we wanted, but we should've have needed to size up. One of the variables I track is the ratio of reach to recommended rider height, which has been steadily increasing. Combine that with longer dropper posts and the ratio of reach to seat-tube length had to increase considerably.


Arierep wrote:
The current trend created not only a longer base line across sizes, which I think is good, but also opened up one's options. Look at Specialized with their "S" size system, you can pretty much select any reach you want, even if you're on the shorter side.

Totally agree. Story / brag time: I came up with a sizing system I called "Gravity Sizing" in early 2017; the sizes were G1, G2, G3. Created the marketing materials and infographics for it with analogies to the ski industry, i.e. ski length is selected by how you want the ski to handle, not your height. Told the company I was working for to trademark it and presented it at Crankworx 2017. Chatted about it with product managers from Specialized, among others. Turns out my employer didn't create the trademarks. In 2018, Specialized comes out with "Style-Specific Sizing" (though perhaps this wouldn't have infringed on any intellectual property). I also did the same with my "Size-Specific Kinematics", where I changed every parameter of the kinematics for every frame size to create a constant experience for riders of different sizes. In 2018, Marin came out with ... "Size-Specific Kinematics". Pretty sure that one would've infringed!

Anyway, it was a good idea whose time had come. When I froze the designs for my geometry, it was the highest ratio of reach to seat-tube length on the market and I started losing sleep, worried I'd gone too far. A few days later, Ibis introduced the Ripmo with almost the same seat-tube lengths ... and I could sleep. A month or two later, Santa Cruz released the Nomad with almost the same numbers and all was well. It felt like a risky move at the time, even if several of us in the industry knew it was the right move.


Arierep wrote:
Personally, my last bikes had, in chronological order, reaches of 450mm, 510mm (hardtail), 500mm and now 480mm. I'm 184cm tall, 195cm arm span (I know, right?).
The 510mm one worked because, being a hardtail, it took weight off your legs, but was very tiresome. The 500mm felt fantastic on a straight line and climbing, but was not as great riding blind and fast on rough natural trails. It was also hard to ride on flat pedals.
After much experimentation I think 475-490 seems to be my sweet spot

Have you considered a longer stem? Broadly speaking, reach is linked to torso length and stem length is linked to arm length.
flag MTBRemco
Posted: Mar 7, 2020 at 2:56 Quote
Edit: post was not bird related and R-M-R helped me by answering some questions.
flag R-M-R
Posted: Mar 7, 2020 at 5:44 Quote
MTBRemco,

It's difficult to make that recommendation due to personal preference, terrain, etc. The steering geometry of any of these bikes is quite different from your hardtail and Bird and you'll probably be on different terrain, so there are a lot of variables.

Consider the front-centre, not just reach. If a bike has a steeper head-tube angle, such as the Swoop, you'll probably prefer a longer reach and vice-versa for the slacker DH bikes.

You mention a preference for a more "playful" bike. Some factors that will improve this:

• Short chainstays
• Less progressive leverage curve
• Not too long front-centre
• Less damping, especially low-speed rebound
flag R-M-R
Posted: Mar 7, 2020 at 8:25 Quote
Very nice. Is that a Shimano Di2 battery mount with a spacer under the rear boss?
flag m4k1
Posted: Mar 7, 2020 at 8:37 Quote
yes...very crude, but i works
flag R-M-R
Posted: Mar 7, 2020 at 9:05 Quote
Doesn't seem that crude, really, and it appears to work very well. Can you fit a large (ex. 700+ mL) bottle?
flag m4k1
Posted: Mar 7, 2020 at 9:12 Quote
i have no idea...i only have a 500ml bottle here. which fits fine
flag RichBowman
Posted: Mar 16, 2020 at 9:02 Quote
Has anyone mulletted (or considered) a 120? Was wondering about a 120mm 29er fork up front (as it would pretty much be the same A2C as the 130m 27.5).
flag vapidoscar
Posted: Mar 16, 2020 at 10:13 Quote
A2C is not as close as you think. You are adding about 10mm to go from 27.5 at 130mm to 29 fork at 120mm. And if you use a 29 wheel, you are adding more space between the ground and the axle.

I suggest modeling your geometry here: https://www.bike-stats.de/en/geometry_calculator

I did it for my build, which is using a 29 fork but sticking with 27.5 wheel.
flag TLa
Posted: Mar 16, 2020 at 12:59 Quote
I stumbled across a topic on the STFU chain damper. I'll share my thoughts on it here also (copypaste):

I have a set on a Bird AM9. I preordered a set way back in ~october and had completely forgotten about it until delivery confirmation dropped in my email. I've been running it for a about a month now and I'm really happy with it. I didn't have any chain slap issue that I knew of, but damn! Now that the chain is in check, it's a such a bliss riding and hearing nothing but tire thuds and braaps. Fitting was really easy too with the provided instructions. For the price I really recommend the gizmo. Whether it'll be "necessary" or fit your bike you'll have to figure out yourself.
flag R-M-R
Posted: Mar 16, 2020 at 13:42 Quote
vapidoscar wrote:
A2C is not as close as you think. You are adding about 10mm to go from 27.5 at 130mm to 29 fork at 120mm. And if you use a 29 wheel, you are adding more space between the ground and the axle.

I suggest modeling your geometry here: https://www.bike-stats.de/en/geometry_calculator

Great information. People always look at the axle-to-crown and forget to add the additional wheel radius below the axle!

 


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