CEBEP

Jipe couod you reconfirm how many spokes stock rim is on R&M Birdy Touring? Is it 32 spokes?

CEBEP

I just discussed with my mechanic, what he proposed is Shimano Deore XT Hub and 11-36 cassette. I’m not going to race it so 11 sprocket should be OK with 52 chainring and 36 will provide good ration for hill climb. Here are photos. Do you guys think this will do OK?
I assume Shifting system Shimano Deore Trekking, 10-speed derailleur coming stock on my Birdy will be a perfect fit.

glye

My original Touring rear wheel is 32 spokes.

The shifter and derailer should be fine. If anything, it should shift better with that Shimano 11-36 cassette than with the original Sunrace. It's made for that kind of cassette size.

That hub uses centerlock brake disks, so you will need either a new centerlock brake disk, or a centerlock to 6 bolt adapter. The disk size is the very common 160 mm. Or get a hub that is made for 6 bolt disks. Shimano also makes those.

CEBEP

Thanks. I’ll change a disk to centerlock model as there are more choices. Could you advise what Sahimano brake code for hydraulic brakes? I know there are Deore but don’t know exact model code. Also front brake disk is 6 screws 160mm, right?

Also will it make any sense to change the chain to Shimano XTR 10?

Jipe

Yes, front and rear wheels have 32 spokes.

The shifting with the Sunrace cassette is really excellent, it cannot be better with the Shimano cassette.

As said, for me 52x11 is too short, its what I had from factory on my Titanium Birdy. R&M always mounted cassettes with 9t smallest cog on the Birdy. I wouldn't invest in a new hub and spokes for a hub that cannot accept cogs smaller than 11t for the Birdy.

For the chain, KMC chain X10SL or X11SL Gold TiN are much better than any Shimano chain, weight less, last longer, excellent factory lubrication.

To fit the Birdy in a big Samsonite case, I think you will have to dismount the front wheel and probably the rear mudguard.

About the disc, since my rear hub is also centerlock, I mounted a centerlock Shimano XT RT-MT800 Ice technology disc and its makes much more noise than the original SM-RT56 disc !

For the front wheel, the Birdy has its disc on the right side what is very unusual.

Most discs are designed to turn in one direction, i.e. counterclockwise. When mounting the disc on the right side, if the disc isn't flipped, it will turn clockwise which will cause problems. Only one piece steel discs like the original SM-RT56 can be flipped. Discs with a center aluminum star cannot be flipped and will turn in the wrong direction.

CEBEP

Mechanic recommended RT86 ice tech 6 bolt for front. I informed him that disk is on the right side and rotor will have to turn in the opposite side but he said it’s fine. Will it be a problem for this rotor to rotate the other way and if yes why? Thanks.

glye

My brakes are Deore BL-T6000, but the bike is 4 years old. You might have a different model. Front disk is 6 bolt 160 mm, yes. Jipe has a good point: The front disk must be a simple flat one piece design like the original. It should be mounted in the correct rotation direction, with the logo facing inwards/left.

Since you're switching to a bigger cassette, the original chain may be a little too short, so it might be wise to have another 10-speed chain ready.

(I agree with Jipe that 52/11 is a short high gear. I get something like 33 km/h at 80 cadence with a calculator, vs. 40 km/h with the original 52/9. If I wanted a cassette solution I probably would have gone for an XD(R) hub and a 9t or 10t cassette. But I prefer the Alfine. Anyway, your call of course.)

glye

Looks like a problem to me, for the reason Jipe mentioned. It's not designed to be mounted backwards, and may end up not aligned with the caliper. If you can try it in the shop before you buy, it may be ok. Personally I wouldn't replace the original, it's fine.

CEBEP

Thanks glye
I have to consider only what I have available here in Turkey. Due to latest customs regulations only packages below EUR 150 in value can be imported as personal items (you still pay taxes) anything above it requires full customs clearance procedure. So I can’t even order XDR hub from Germany which Jipe referred to, even if I wanted to.

Also these are expensive toys and I need warranty coverage, not really possible when ordered from abroad.

Regarding brakes, did you consider upgrading to Deore XT? Regarding front rotor, do you think using RT86 with opposite rotation (front) be an issue?

glye

Right, given that customs situation it's understandable. And if you can't find any domestic bike parts company that imports these things, you're limited indeed. Too bad.

Brake upgrade: I see no need. The original works very well. Brake power depends on both disk size and wheel size. With the tiny 355-size Birdy wheels and relatively big 160 mm rotors, you get good braking. It corresponds to something like a 260 mm disk on a 29er wheel, but they are often happy with "only" 200 mm.

RT86 with opposite rotation: Yes, potential problem. Should not be run backwards, and may not fit when flipped. Try before you buy

jackyharuhiko

the backwards situation of the front brake disc is very interesting. I never thought of that. Is this installed backwards? Anyway, I see no difference in braking power.


As discussed earlier my Pacific Cycles Birdy came with the Avid BB5 brakes… so I had to upgrade it to the XT hydraulics.

jackyharuhiko

I just compared the front and back disc and it really seems that the front disc is backwards, the cutouts looks like an aerodynamic design at the back but the front one doesn’t look very aerodynamic. Lol. But I don’t think it will have any perceivable real life effect. Changing your riding position has more influence on it.

This peculiar design should be for folding since the front brake disc will collide with the back derailleur and cassette if it’s on the left.

jackyharuhiko

I can confirm that mine was also 32 spokes. I actually counted them because they were a nightmare for me when I used my electric pump to pump the tires.

CEBEP

Could you advise which other popular brand would do XDR hubs? I searched 135mm XDR HUB and had no prices in local google shopping. Every bicycle shop I came across had Shimano products all over them.

Regarding flipped disk, I’ll definitely try before I buy as my mechanic who will rebuild the wheel and install all parts is the one I’m buying parts from. He will definitely check the alignment first. If alignment is fine is there any other issues to use it flipped? The reason why I’m thinking about RT86 in the front is the front brakes get the most load while breaking and better cooling properties of the rotor can’t hurt.

glye

Interesting, yes! Your disk seems to be rotating the wrong way. The logo/print is facing right, it should be facing left, as it is on bikes with the disk on the left side. There usually is a rotation indicator arrow printed on the disk, if you find that you can confirm.

I expect no difference in braking power, and I also think the aerodynamics difference, if any at all, will be very very tiny. The concern here is that the disk is designed to take force in one direction. We do very little braking while rolling backwards, after all. If you load it in the wrong direction, you increase the chance of disk collapse, which at best would mean loosing all brake power, and at worst would lock up the front wheel instantly - hard crash.

The risk for this depends on the design. Your disk looks quite strong to me. It has not many holes in the surface and the black carrier makes it stiff. And it is not as extremely spiral shaped as some other designs are. Compare to this light weight one piece design. Loading this in the wrong direction would be more dangerous than with yours, I think. Still, it's a risk I would not take, personally.


Light weight disk

Simple one piece designs are fine to flip over because they are flat. The surface doesn't change sideways position when you flip it. But with multi piece designs that can happen. The black carrier material may be thicker than the brake surface. If so, when you flip it the surface now has moved outwards, and doesn't fit the position of the brake caliper anymore. Maybe it's an insignificant effect, maybe not. Regardless, for safety I will use a reputable brand rotor mounted in the correct rotational direction. I don't see any benefit with fancy multi piece designs that outweigh the risk. If you can flip a multi piece design like yours without caliper alignment trouble, it should be fine.

You must be right about the folding as the reason why the Birdy disk is set up this way. It seems an unintended consequence of a bike originally designed for rim brakes. The other peculiarity, that the disk is mounted closer to the center of the wheel and requiring special hubs, must be for the same reason. Likely the fork swingarm would have to be made wider if they where going to use standard hubs. It could also be that the hubs are also designed to take brake force in one direction, so they would need special hubs anyway. Dynamo hubs could also be most efficient in the correct rotation direction, I don't know.

CEBEP

I discussed this with my mechanic. He said that there should be no issues with alignment simply because it’s a standard Shimano brake caliper using standard rotor. So using another Shimano rotor should make no difference in alignment. Makes sense to me.

In terms of cooling as he explained it’s not due to aerodynamic properties but the internal sandwich structure steel and aluminum. Aluminum dissipate heat better.

In terms of disk structure it’s an interesting point glye made. RT86 rotor also looks much stiffer to me compared to ultra light design. However there will be much less rotational forces for same braking effort considering 18 inch wheels and it should probably be fine. At least my mechanic said it will be and warranty on the rotor will hold.

jackyharuhiko

Thanks so much for the detailed analysis. Just had a chat with the bike shop mechanic and he said both Birdy and the new Dahon K3 Plus have the same situation with the front brake disc on the right side. He said that the Shimano Ice Tech disc can only be installed in one direction and cannot be flipped over. But he emphasised that for Shimano’s disc (the one that I am using is exactly RT86), it’s fine for it to be rotated ‘backwards’, however, for Hope’s brake disc, he would recommend to flip it over (and it can be flipped over) to retain the direction of rotation.

Hope’s brake disc

glye

Yeah, it seems very limited. For the combination of 135 mm quick release, disk brake, and XD, I find only 2 hubs in a big online shop like Bike24: https://www.bike24.com/cycling/parts...rchTerm=&sort=
For XDR, I find none at all.

You could ask a local shop if they would be willing to import a hub for you, of course. If that doesn't work out, it seems the only cassette options are keeping the Sunrace (until it breaks) or going with Shimano HG like you're planning.

If alignment is fine in the correct rotation direction, there should be no other issues.

Better cooling doesn't hurt (apart from the higher cost), but there is no practical benefit either, unless you do a lot of braking. I mean, riding up and down high mountains. I am heavy and I ride only with plain one piece steel brake disks, no special cooling features. I have had disk brake fading only once, on a 406 (20") wheeled bike with 160 mm disks. That was when coming down from 1250 meters altitude to 240 meters (1 km vertical distance) over a 14 km distance. Of this, 800 meters of vertical distance was on the last 8 km of this road. That's a 10% average downhill slope over 8 km, with many tight turns so I couldn't go very fast and get much help from air resistance to slow me down. This was when coming down into Rjukan, Norway, from the south. https://norgeskart.no/#!?project=nor...03.57719052507

Then consider brake disk diameter divided by wheel diameter. The larger the disk, and the smaller the wheel, the higher the ratio is, and the better your brake power. Some approximate examples, assuming roughly 50 mm height tires:

622 (29er) wheel with 200 mm disk: 0.277 ratio
584 (27er) wheel with 220 mm disk: 0.322 ratio
559 (26") wheel with 180 mm disk: 0.273 ratio
406 (20") wheel with 160 mm disk: 0.316 ratio
Birdy 355 (18") wheel with 160 mm disk: 0.352 ratio - the clear winner!

So looking at this ratio alone, the Birdy is better equipped for braking than pretty much any other bike you will find in a store, even some downhill specific bikes. Of course those downhill bikes use specially powerful brake calipers, large pads, and special disks, to compensate for their extreme use. The Birdy doesn't need this.

You will not have any kind of brake heating problem with the Birdy, not unless you do downhill runs that are both steep and very long, like my example from Rjukan. With for example 200 meter hills there is nothing to worry about, in my experience. Anyway, there is nothing wrong with buying expensive high performance disks. There is just no practical need for vast majority of Birdy riders.

CEBEP

glye thanks for your practical suggestion. It’s amazing how much you travel with your birdy!

Most of our ourchases have no practical meaning. I will be upgrading my rear rotor anyway as I’m changing the hub and I thought it would make sense to Ice Freeza rotor and thought it would be a good idea to have same properties in the front too.

Out curiosity how did you apply brakes during long descending? I assume using them in tern makes more sense to manage hearing, front and then rear and then front again?

glye

Right, thanks for the info. Given that this mechanic is experienced with this kind of bikes and the issues with reversing disks, it could be safe to do as he says. The disk will see less extreme forces on the Birdy than on the big wheel bikes it is designed for, anyway. So there could be a good enough safety margin here.

The disk is designed to have the right side contacting the hub. If you flip it, the left side contacts the hub. If the bolt hole part of the disk is thicker than the brake surface, the disk is now misaligned outwards by (bolt hole thickness) - (brake surface thickness). A 2 mm difference means 2 mm misalignment, for example. According to jackyharuhiko's mechanic, this is the case for the ice tech disk. But if the thickness is the same, it's fine, as with the Hope disk example, and with the original disk delivered with the Birdy. Those can be flipped.

This is true, and if they are willing to keep the warranty on it, it could be fine.

Personally I see no good reason for this kind of experimentation, but: Your bike, your decision

CEBEP

I think I’ll go with Shimano Deore XT and 10s 11-36 cassette which is the best choice I have locally. I’m not a racer so speed on 11 should properties be enough for me. In case it isn’t I can upgrade 52t chainring to a bigger diameter. What would be the biggest diameter I can go with without compromising the fold?

CEBEP

Im not going to flip it, it will be connected correctly but rotate to the opposite direction since it will be mounted on the right side. This is what I meant saying there should be no misalignment.

jackyharuhiko

Thanks glye, CEBEP and jipe. I learnt so much about the Birdy in this thread.

glye

Rjukan is close to where I live, easy to get to apart from the climbs. (This was with a different bike.)

Yeah, I'm also sometimes guilty of upgrades that have little or no practical benefit. I admit this

I'm no expert on that kind of extreme downhill. But I had heard the same as you - switch between front and back brakes, and that's what I did on that day.
The brake fade was scary but manageable. It was gradual. As soon as I noticed it happening, I stopped. Then I could smell the cooking brake pads and see the disk metal turned black-ish. So I just waited for it to cool, while moving the bike slightly a few times, so that the part of the disk inside the caliper would also be exposed to the outside air. When things looked normal again I continued carefully downwards, and did a few more stops to be on the safe side (and take pictures of the view). It's good to be aware that fading can happen, so that one recognises the signs quickly and stop while it's still possible.

Electric cars and some ebikes have a benefit here: They can dump a great deal of energy into charging their batteries, instead of braking.

I don't know, maybe Jipe does? One limit is the chain retention device under the chainwheel. It seems to support 60t, as I read the Pacific Cycles info. Then the fold has it's limits, as you say. This needs the input of someone who has tried it, or some careful measurement and calculation.

glye

Oh right, then alignment will be fine, yes.