Bird Aeris owners thread

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flag hainman
O+
Posted: Aug 20, 2019 at 7:09 Quote
R-M-R wrote:
hainman wrote:
To get to any Decent trails we drive around 1-30 minutes here in Scotland
But that time frame from where I live is a small price to pay for some amazing trails

I can't imagine how much you must hate riding pavement to drive 1 minute to a trail!

(Guessing you meant 10 minutes.)
Na I meant an Hour n 30 minutes
Small price to pay for sick steep techy trails
flag clamps81
Posted: Aug 22, 2019 at 1:04 Quote
Has anyone tried a 29er on the front of the 145lt? Looking at the a2c comparison there is 20mm difference for the same travel, so may need an angleset to bring the headangle a bit steeper? I don't think the change to bb height would be too drastic as the 145lt is so low (though I may be wrong) - just something that occurred to me earlier as an interesting possibility and I know someone who would lend me a fork/front wheel to try it.
flag R-M-R
Posted: Aug 22, 2019 at 5:17 Quote
clamps81 wrote:
Has anyone tried a 29er on the front of the 145lt? Looking at the a2c comparison there is 20mm difference for the same travel, so may need an angleset to bring the headangle a bit steeper? I don't think the change to bb height would be too drastic as the 145lt is so low (though I may be wrong) - just something that occurred to me earlier as an interesting possibility and I know someone who would lend me a fork/front wheel to try it.

If you have access to the necessary components, you should definitely try it.

• The 145 LT is low, but not crazy low. It's a decent candidate for a longer fork.
• The static head angle will become more slack, and it will also be more slack when compressed, unlike simply adding more travel to a 650b fork. A slacker angle when compressed is definitely a good thing.
• There's nothing inherently wrong with changing a head angle. Maybe the stock angle is too steep - Pole and Mojo / Nicolai would argue it is! Only one way to find out what you think about that.

Take advantage of this opportunity and give it a go!
flag clamps81
Posted: Aug 22, 2019 at 5:42 Quote
I'll give bird a ring in case it's warranty voiding, but assuming its not I may well try it. If I've done my sums right then depending on the exact A2C you're looking at 63.9-63.4 degree head angle, which is sort of bonkers pole machine type territory. The other numbers don't look too bad for bb drop etc and plenty of room to play with bar height.

Will keep you folks updated on the progress of this one.
flag ptld
Posted: Aug 22, 2019 at 15:21 Quote
I gave it a go.

27.5 Fox 36 @ 160mm 44mm offset
29 Lyrik @ 160mm 51mm offset

Measured before & after - don't entirely trust the HA measured, but difference is accurate.

27.5
BB 335
HA 64.2
WB 1240

29
BB 345 (+10mm from 29)
HA 62.8 (-1.4 from 29)
WB 1255 (+15)

Front felt good for rollover like all 29ers and higher bottom out (40mm: 20mm wheel + 20mm axle to crown) for steep stuff.
Enjoyed the higher BB for pedal clearance in chunky stuff, I'd like to run 165mm rather than 170mm cranks too.
Had some funky wheel flop initiating turns, would try running bars 2cm lower, apparently 42mm offset on 29er makes a good difference. I've run the 27.5 with -1.5 headset and had the same feeling, so is most likely HA rather than wheel.
flag R-M-R
Posted: Aug 22, 2019 at 16:56 Quote
ptld wrote:
I gave it a go.

Did you try the 29er front end with a negative head angle to keep the head angle fairly constant with your 27.5 set-up? If so, what did you think?
flag ptld
Posted: Aug 22, 2019 at 17:31 Quote
R-M-R wrote:
ptld wrote:
I gave it a go.

Did you try the 29er front end with a negative head angle to keep the head angle fairly constant with your 27.5 set-up? If so, what did you think?

No it was a loan for short term.
My guess is shorter offset + lower bar would weight the front adequate and would be ok, I managed to equal some BPs as it was so it certainly wasn't exploding.
On a longer term test would try +1 degree headset also, might get the BB up a tiny bit, only negative there.
flag R-M-R
Posted: Aug 22, 2019 at 21:25 Quote
ptld wrote:
R-M-R wrote:
ptld wrote:
I gave it a go.

Did you try the 29er front end with a negative head angle to keep the head angle fairly constant with your 27.5 set-up? If so, what did you think?

No it was a loan for short term.
My guess is shorter offset + lower bar would weight the front adequate and would be ok, I managed to equal some BPs as it was so it certainly wasn't exploding.
On a longer term test would try +1 degree headset also, might get the BB up a tiny bit, only negative there.

The difference in BB height will be 1.7 mm. Tiny indeed.
flag clamps81
Posted: Aug 22, 2019 at 23:59 Quote
That's some excellent info - thanks.
flag colourofsound
Posted: Aug 25, 2019 at 4:43 Quote
@r-m-r you clearly know your suspension and geometry; maybe you can help.

I run a Zero AM hardtail; and whilst the backend will always feel harsh, the front also feels like a lot of work. I’ve set up my Yari to Rockshox recommended settings but it really tires me out. I’ve recently installed a 140mm debonair to the bike (in prep for moving to an LT120 eventually); but I don’t feel like the improved air cart has made much difference.

Is there much I can do in terms of settings/tokens, or is it a case of man up/buy the better charger damper? It’s the standard RC damper from the cheaper Yaris currently. 2016 no less.

Thanks in advance!
flag HardingTrail
Posted: Aug 25, 2019 at 10:45 Quote
Thorjensen wrote:
120LT in the Alps
photo

I think that’s the best looking 120 LT I’ve seen.

How did it cope in the alps?

Hopefully getting mine in orange later this week.
flag R-M-R
Posted: Aug 25, 2019 at 13:03 Quote
colourofsound wrote:
@r-m-r you clearly know your suspension and geometry; maybe you can help.

I run a Zero AM hardtail; and whilst the backend will always feel harsh, the front also feels like a lot of work. I’ve set up my Yari to Rockshox recommended settings but it really tires me out. I’ve recently installed a 140mm debonair to the bike (in prep for moving to an LT120 eventually); but I don’t feel like the improved air cart has made much difference.

Is there much I can do in terms of settings/tokens, or is it a case of man up/buy the better charger damper? It’s the standard RC damper from the cheaper Yaris currently. 2016 no less.

Thanks in advance!

The Motion Control damper will never be as good a Charger 1 / 2 / 2.1, but it's not bad and shouldn't be so tiring that it feels like a burden on a hardtail.

My first step is always to ensure the internals are all clean and lubed. Harsh forks are usually due to the bath oil being long gone and the seals needing some grease. Start with a basic overhaul: everything other than the damper, unless you're feeling ambitious; you can probably reuse the seals.

The next step would be to experiment beyond the recommended settings. Are you using full travel on substantial impacts? If not, then you may have too much of the following, or order of likelihood:

1. Ramp (i.e. too many volume spacers)
2. Air spring pressure
3. Compression damping

Or you may have too little compression damping, causing the fork to be initially supple, then hitting a wall of spring force. That's more of a problem with extremely adjustable forks and shocks; yours probably doesn't allow you to reduce the damping to that level.

For most people, I recommend starting with zero volume spacers and a touch less compression damping than recommended. Adjust as necessary from there. I can help you work through the tuning process if you still struggle.

Oh, and consider a super wide rim and super wide front tire. I'm running a true 2.6" tire (that's 2.8" if you're Specialized Wink ) on a 36 mm (internal) rim at 16 - 19 psi. It's wonderful. You need the wide rim, though, or the tire will be prone to lateral collapse.
flag colourofsound
Posted: Aug 25, 2019 at 15:35 Quote
R-M-R wrote:

The Motion Control damper will never be as good a Charger 1 / 2 / 2.1, but it's not bad and shouldn't be so tiring that it feels like a burden on a hardtail.

My first step is always to ensure the internals are all clean and lubed. Harsh forks are usually due to the bath oil being long gone and the seals needing some grease. Start with a basic overhaul: everything other than the damper, unless you're feeling ambitious; you can probably reuse the seals.

The next step would be to experiment beyond the recommended settings. Are you using full travel on substantial impacts? If not, then you may have too much of the following, or order of likelihood:

1. Ramp (i.e. too many volume spacers)
2. Air spring pressure
3. Compression damping

Or you may have too little compression damping, causing the fork to be initially supple, then hitting a wall of spring force. That's more of a problem with extremely adjustable forks and shocks; yours probably doesn't allow you to reduce the damping to that level.

For most people, I recommend starting with zero volume spacers and a touch less compression damping than recommended. Adjust as necessary from there. I can help you work through the tuning process if you still struggle.

Oh, and consider a super wide rim and super wide front tire. I'm running a true 2.6" tire (that's 2.8" if you're Specialized Wink ) on a 36 mm (internal) rim at 16 - 19 psi. It's wonderful. You need the wide rim, though, or the tire will be prone to lateral collapse.

As ever; excellent advice. It’s worth knowing that I’ve been only been riding ‘properly’ for 2 years; i.e off piste and trail centres in Wales, UK.

To answer a few of your implied queries:

- Forks recently had a lower leg service as part of the debonair installation. A new seal kit was purchased from TF Tuned so it should be as fresh and tasty as it’s ever been.
- I am not using full travel; however I am not an aggressive/fast/confident rider. I’m certainly not the slowest on the trail but I’m still getting to grips with drops and harsh terrain. So I’m not sure how good a metric that is. I’m getting through 3/4 of the travel currently.
- I don’t know if I have any volume spacers. What ever the default is...?
- Spring pressure and rebound are the recommended settings for my weight. I understand the concepts they control but have yet to attain the awareness on the bike to understand how they effect feel. Air spring is straight forward (less air = more comfort = less support) but comp dampening and rebound still seem like dark arts. It’s worth nothing that rockshox don’t provide a recommended compression dampening settings; just PSI and clicks of rebound.
- Wheels are DT Swiss 1900 Spline with 2.6” DHF. Fork is boost spacing. The whole bike is a second hand job; it’s a Bird Zero AM non-boost rear from 2016. It really kills my calves! But that’s hardtails for you...

Thanks again for your detailed response and gracious offer to help. It’s much appreciated.
flag R-M-R
Posted: Aug 25, 2019 at 18:06 Quote
colourofsound wrote:
As ever; excellent advice. It’s worth knowing that I’ve been only been riding ‘properly’ for 2 years; i.e off piste and trail centres in Wales, UK.

To answer a few of your implied queries:

- Forks recently had a lower leg service as part of the debonair installation. A new seal kit was purchased from TF Tuned so it should be as fresh and tasty as it’s ever been.
- I am not using full travel; however I am not an aggressive/fast/confident rider. I’m certainly not the slowest on the trail but I’m still getting to grips with drops and harsh terrain. So I’m not sure how good a metric that is. I’m getting through 3/4 of the travel currently.
- I don’t know if I have any volume spacers. What ever the default is...?
- Spring pressure and rebound are the recommended settings for my weight. I understand the concepts they control but have yet to attain the awareness on the bike to understand how they effect feel. Air spring is straight forward (less air = more comfort = less support) but comp dampening and rebound still seem like dark arts. It’s worth nothing that rockshox don’t provide a recommended compression dampening settings; just PSI and clicks of rebound.
- Wheels are DT Swiss 1900 Spline with 2.6” DHF. Fork is boost spacing. The whole bike is a second hand job; it’s a Bird Zero AM non-boost rear from 2016. It really kills my calves! But that’s hardtails for you...

Thanks again for your detailed response and gracious offer to help. It’s much appreciated.

Happy to help.

That all sounds reasonable.

This is definitely a case to remove any volume spacers that may be present. The function of spacers, as you may be aware, is to prevent bottoming out for hard-hitting riders who don't want to affect their sagged ride height with more pressure. Since you're not accessing full travel, you want to do the opposite - i.e. remove bottom-out resistance. Here's a good tutorial. It's quite simple, just be careful to not round off the shallow wrench flats on the cap. Some people purchase flat-faced sockets (i.e. without the rounded edge that helps locate the tool) or grind down a normal socket; I use a nicely made adjustable wrench with flat, machined sides and jaws that have nearly zero play. Lots of options, just use care.

If you still aren't using full travel once you've removed all tokens (maybe that's already the case), you can choose to either live with not getting full travel or reduce pressure to use all the travel you paid for, at the cost of lower sagged ride height - which may not be a bad thing, depending on your preferred ride feel.

RockShox doesn't provide compression damping recommendations because there's not much for you to adjust. The top of your right fork leg should have a climb / lockout dial; that's your low-speed compression. You can turn it a little to add support during low shaft-speed events, which may allow you to reduce spring pressure without losing support. This may or may not help your situation; at least it's free to try!

I encourage you to experiment with tire pressure to bridge the gap between small impacts your fork handles poorly and larger hits the fork handles well.

 


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