jur

I have done 2 commutes with the HRM... not enough to get some averages, but enough to get an idea.

I felt very similar the 2 days, and the weather was very similar as well. I only clock time in to work, then the wind is very low.

I also pumped both the Swift and the Birdy to 100psi. The Swift has a Conti GP at the front, and a Primo Comet Kevlar with a Slime liner on the back.

The Birdy, weighed this morning sans luggage, is 12.6kg. I must guess the Swift at 9.5kg sans luggage (both cases luggage is a backpack).

So, the times were 56min for the Swift, 57min for the Birdy. Both cases the HRav was 129bpm. In the Birdy run, the HRmax was 213 so it picked up some interference somewhere, which might alter the average a bit, if anything it might then be lower without the interference. the Swift max was 167bpm, that is probably real.

I think the 1 minute difference can easily be explained by the extra mass for the Birdy, since there is a not insignificant amount of uphill. There was also 1kg extra luggage on the Birdy in the backpack. Plus the Swift gearing is more suitable, and the derailer runs slightly more efficiently. Plus on the Swift run, there was another roadie cyclist in front of me for a few minutes which often has the effect of putting in more effort, although I tried not to. That may have made a few seconds difference.

The Birdy sure is a whole lot more comfortable. The Swift sure feels a whole lot faster.

Seems to me that tiny difference in speed (less than 2%!) is not worth it on the Swift.

On the plus side, the Birdy is a whole lot faster now that I have the tires sorted. I doubt that the Marathon Racer will have a significant impact over the Plus.

jur

The Pletscher rack will add unsprung weight to the rear wheel, that is the only drawback I can see besides folding.

It may be possible to attach the stays for the Pletscher rack to to same point as where the Birdy stays go, and so minimise unsprung weight. I'd say the luggage capacity would go down a bit but not by much. You'll need to see how much pulling back the top swiveling attachment point can handle.

yangmusa

I should have specified I was considering the Pletscher Orion (though people who have used the suspension pannier rack claim it does actually work...) I'm not sure I need panniers on the back - R&M themselves recommend carrying most of the weight on the front, and also I don't know if rear panniers would fit with my big feet

I hadn't actually considered mounting the Pletscher suspension rack to the Birdy mounting point... hmm, that's an interesting idea. I'd have to say I think the suspension rack looks a bit.. <cough> dorky.. but maybe the ability to fit panniers, should I have to, is worth it?

jur

The Pletscher Quickrack Suspension might actually allow you to fold if mounted on the Birdy points. I'm just not too sure about the pannier hanging ability, but it looks a whole lot better than the Orion to me. If you did hang a pannier, you always have the option to take the stays down to the axle points, or you would need the rear mudguard stays for the pannier support.

energyandair

You may want to look at the North American Schwalbe Site https://www.schwalbetires.com/bike_tires/road_tires

The Marathon Racer and the Kojak are each rated at 6 bars for speed whereas the Marathon Plus is rated at 3. (The rating system is: 6 is outstanding for class and 3 is average. I'm not sure what that translates to in rolling resistance)

If you open "Comments" on the Marathon Racer, The most recent comment is from someone who reports noticing a big difference when they changed from Plus to Racer on their recumbent.

The weights are:
Marathon Plus 510gm
Marathon Racer 260gm (250gm less)
Kojak 185gm (325gm less)

David

jur

Yes, I have read those; I suppose what I mean is, that "other factors" are beginning to dominate the commuting time, in this case, weight, wind resistance and such-like.

I am thinking along the lines that while the racer will be faster than the Plus, I suspect the difference is now likely obscured by those "other factors." For one thing, I will need to be more accurate with the time keeping - I have been rounding to the nearest minute since stopping for lights slows me down a bit and that is unpredictable. So the commute won't cut it for accuracy.

jur

Of course I got a puncture on the way home in the "puncture-proof" Marathon Plus. Ordinary small piece of glass. I was completely unsuccessful in finding the puncture, so gave up in the end and walked to the train station and caught a train home.

yangmusa

I fitted Stelvios last night, can't wait to go for a ride! I would have taken the Birdy to work today, but the forecast was for rain. They were quite challenging to fit, very tight on the rim - and I really shouldn't have been a cheapskate and reused my original 18x1.5 tubes, they're bigger than the tires! My only concern with the Stelvios is that they'll lower the already low top gear still further... I haven't measured, but they're visibly much smaller than the Maxxis.

On an unrelated note: my chain keeps falling off at the rear when I fold. That happened every time at first, but then I seemed to solve it by folding fast. I don't think I'm doing anything different now, but the last few times the chain has come off every single time. Could the chain be too long? This may well be my lack of practice, rather than a technical problem, but any advice much appreciated.

jur

I wouldn't have thought falling off at the rear was possible... is it falling off the smallest cog to between the cog and frame?

Is the derailer pulling properly to the back?

Looking at chain length is not a bad idea. Put it on the biggest sprocket and make the chain as short as possible.

bhkyte

"I fitted Stelvios last night, can't wait to go for a ride! I would have taken the Birdy to work today, but the forecast was for rain. They were quite challenging to fit, very tight on the rim - and I really shouldn't have been a cheapskate and reused "my original 18x1.5 tubes"

I doubt that will work, not recomended from my experience as the tyres get pulled of the rim with oversized tubes.but is you got them to work OK with 1.5 , then fine.

yangmusa

It is apparently possible, sadly...

No, it falls off the derailleur jocket wheel/chain retainer. I couldn't find any clear pictures of the folded bike, so have used a non-folded pic from Flickr. Don't know if it makes sense?

Not quite sure what you mean, but it seems to shift normally.

pm124

Actually, the chain catcher will only work when it is in the highest gear. This is what I would do: 1) shift it to the highest (hardest to pedal) gear; 2) adjust the chain catcher so that it is riding about 1mm above the chain.

Now, when you fold, it should catch the chain and keep it on the bike. You have front chainguards, right?

pm124

Actually, that should mean that your Birdy is way outperforming your Swift. The Plus should be about 2-3MPH slower at the same wattage as the Stelvio without a liner. I would think that it would still be slower than a Comet with a liner. Of course, this could all just be road quality. I'm sure that your Swift would burn your Birdy badly on an uphill climb on smooth road.

(Also, without a power meter, the error is much greater than the point estimate.)

yangmusa

I do shift to the highest gear before folding. The chain catcher may be quite a bit more than 1 mm above the chain - that's another thing I'll have to check!

I do have front chain guards, yes.

pm124

Yangmusa, yes, try adjusting it. Jur's excellent advice about the chain is good, perhaps taking a link off will help. The only other advice I have is to be Zen and quick when folding it.

jur

Actually looking at the chain length was his own idea.

Now that I know where the chain is falling off, well I have the same. In my case it is caused by me replacing the long cage derailer (Alivio) with a medium cage one (XT), which doesn't gather the same amount of chain, so the chain becomes slack and if I'm not careful about making sure it stays hanging on the catcher, it will fall off.

I'm putting a long cage RD (LX) back on this weekend; I need the medium cage XT for another project.

jur

I also cured a very persistent click on my Birdy... it would go click at the front wheel with every wheel revolution. I looked at the bearings, the speedo magnet, little rubber bits sticking up off the tyre, the magnet again, felt all spokes for a broken one, the valve locknut... nothing.

Then I noticed it gives 2 clicks every revolution, plus it gets worse if I tilt the bike over... OK that's spokes! So I plucked all the spokes and there was one that's lost tension. Comparing mine with my workmate's his spokes are a lot tighter. There is no threadlocker on the nipples; I will have to do the entire wheel to make sure it doesn't happen again. I am speculating it happened during the rough touring, or my wheels are simply more used than his.

BruceMetras

Could there be a Moultonesque air of mystery to that disclosure? ..

trad

Sizing help please... Interested in a birdy, but cannot get sizing info. Searched and found that effective top tube was 58cm but position of bottom bracket made the bike a "medium" size.

On road bikes, I ride 58cm (C-C) seat tube; 57.5 cm top tube, and 110cm or 120 cm stem. I'm 6 ft. Would I be cramped on a Birdy (sit too upright)? Are their options on stem/handbar to stretch out a bit?

Many thanks in advance.

somersetflyer

I am the same height as you and have recently purchased a birdy with a comfort stem, just couldn't get it set up right, felt too cramped and too upright. AVC in Bath swapped the stem for the standard stem and its a different bike, feels very similar to my touring bike now

Hope this helps

jur

You found correct... the Birdy is definitely also a medium ie 55cm top tube bike. You would need the sports stempost and you could quite easily fit a stem to the stempost, putting the bars further forward again. This would increase the tiller effect but I don't see how that is bad, per se. The sports stempost puts it out of knee's way. I'm 5'10 and my body and arms are at 45deg to the horizontal.

jur

Found a broken spoke, back wheel non-drive side today...

kamtsa

Jur,

I was looking at some of your pictures.

https://members.iinet.net.au/~jdekter...sentr2008.html

You are going over some rough surfaces. What kind of tires are you using?

I am avoiding going over surfaces better than that but maybe my Marathons can handle more than I expect.

Kam

jur

These were the cheap original tyres on the Mini.

I think tyres can handle anything that won't actually cut into the tread surface. The question is more one of grip on said surface. Last weekend I took my Moulton out for a bush bash MTB ride over some pretty stony stuff, and I was running high pressure Continental road tyres! They handled it surprisingly well.

In the early years of the Tour de France, much of the race was on badly-surfaced dirt roads, but those chaps raced with their skinny tyres on it.

So you could ride over almost any surface with the Marathon Racers as long as you can maintain balance and the tyres won't get cut. That's really all what tyre tread is for - getting a grip on the surface.

yangmusa

My wife and I have ridden up Mount Tamalpais (Marin County, CA, USA) on a fire road with rough and loose gravel and sand. She on her Moulton with Schwalbe Stelvios and my on my Birdy with the original Maxxis (now Stelvios too).

I think Jur is right - the main problem might be grip. We were both fine going up. My fatter Maxxis tires were more confidence inspiring on the way down - but we were both a lot slower than the MTB folks who were bombing down the path!

If you do lots of offroading, it might be worth getting knobbly tires. But for the occasional jaunt offroad your Marathons will be fine, just take care on any loose surfaces.