somersetflyer

I have just recently cycled two 100Km rides on my Birdy fitted with a Rolhoff hub. comfort wise no problems, but despite being reasonably fit, I couldn't keep up especially on the hills with normal road/touring bikes. Is this an inherent problem with 18" wheels and would I be better off on Audax rides using a 'normal' bike.

Andrew

pibach

There are races where people on 16" compete with full size bikes, in particular when climbing (downhills its more difficult). See, for example, Rob English from Bike Friday, https://bicycle-musings.blogspot.com/...ime-trial.html
"Rob English, riding a titanium Bike Friday finished in first among the folders with a time of 1:35:22 (my time was 5:35:99) which was only about 9 seconds behind the race winner on a regular bike. Pretty impressive."

KitN

If your bike is geared properly to compensate for the small wheel circumference then you can hang with the big wheeled boys but accomplishing that seems difficult and often problematic with most folders.

But wait, you have a Rolhoff! That thing has wicked gear ratio/range! You shouldn't have had a problem on those hills. Hmmm... Odd. How many teeth does your chainring have?

KoYak

Uphill or downhill?

I find I am a bit slower in the flats and downhill but faster up hills on my small wheel folders.

alhedges

You have really asked two not-quite-related questions.

Your relative slowness is probably not inherent to your 18" wheels. But it may be inherent to other aspects of your bike.

Note that the Moulton still has a world speed record, and riders using BF pocket rocket pros or Air Glides are able to achieve results that are very very close to those reached by riders using nonfolding road/racing bikes. This wouldn't be possible if there were something inherently slow about the wheels.

However, the bikes mentioned above are both very lightweight, have an aerodynamic cockpit with drop bars, etc., and have gears appropriate for racing.

Rohloff equipped Birdies weigh 28 lbs, IME have a fairly upright riding position, and don't have racing-appropriate gears.

So you may want to consider using a road bike the next time, but the reason to do so would be for the other advantages inherent in the design, not just because they have 700c wheels.

Although what you should *really* do is spend $4,000+ on a dura-ace equipped PR Pro, or maybe more on a Moulton, and ride that.

(It is also possible that you are slower than the other riders for reasons unrelated to your bike :@).

niggle

Interesting.... Where I ride the terrain is full of short sharp hills with practically no flat bits between the ups or downs and I find when riding large wheel bikes that, compared to small wheel bikes, they carry more momentum from the downhill helping you up the first bit of the uphill, but are slower to accelerate down the first bit of the downhill.

Over all it seems to even out but I remember when asking around, before I bought the Pacific, someone was saying they found their Birdy hard up hills due to excessive up and down movement of the front when pushing hard and I had similar issues with my old Moulton APB. The Pacific simply does not seem to do this though what the difference is I am not sure, maybe the suspension design?

joose

If you click on these 2 links (to the Strida website) you will find the speed difference between 16 and 18 inch wheels.

https://www.strida.nl/english/products.php?subpage=50

https://www.strida.nl/english/products.php?subpage=sx

I have a Dahon D3 Curve and a Specialized Crossroads comfort bike (about 9 years old). The SC is easier to pedal and travels faster than the DDC in my opinion.

BruceMetras

That's really nothing to do with comparing inherent speed differences between 16" (305mm) and the 18" (355mm) wheel sizes.. the difference in this particular instance is that the 16" single speed Strida is running a smaller diameter wheel, hence lower gearing.. so the overall speed will be lower for the same cadence..

Note to EvilV... I installed the 355/Kojak combination on the fake.. wow!! practically pedals itself now compared to the old 305/Maxxis combo I was running ... even though I'm going faster for the same cadence it feels like I'm in a lower gear and not putting out near the effort .. those slick Kojaks are fast..I'm actually finding myself using the brakes ..

Note to O/P .. if you're not running Kojaks on your Birdy.. try a pair .. who loves you baby!

niggle

Have a look on here then see what you think: https://www.moultonbicycles.co.uk/her...#recordsracing

yangmusa

Bruce beat me to it. I was going to ask what tires you have on the Birdy. I swapped the stock tires for Schwalbe Stelvios, and there is a very noticeable speed difference. No problems doing long weekend rides with friends on full size bikes. I have a Capreo Birdy though, no internal gears. I don't know if it makes a huge difference - I use to ride my Sturmey-Archer 8-speed equipped Xootr Swift on long (60-70 mile) road bike rides and have no problems hanging with the pack either.

joose

niggle - thanks for the link, I enjoyed reading it again. I wasn't making a point about Strida, just that I noticed it the other day and thought it was worth adding to this discussion.

For the type of cycling I do (minimum effort) I find that larger wheel bikes require less effort to go at the same or slightly faster speed than when I'm on my Curve. This may be because of gearing, I'm not sure? The larger wheel bikes have been more comfortable in basic spec than the Dahon with upgrades. This may be because of different geogmentry or because the larger wheels cushion the ride better? Again not sure but the differences between the larger and smaller wheeled bikes do add up and I feel in my opinion that to travel the same terrain and distance the large bike* is easier and more comfortable.

While I have owned many large wheeled bikes, I've own only one folder so my compasion may not stand true, particuly when compared to a Moulton.

Joako

joose, the Curve D3 has a very noticeable drag that requires more effort from the rider. I recently got a Xootr Swift and I immediately noticed the difference. I will be upgrading the crankset and bottom bracket soon to see if it improves a little bit.

joose

Joako - I wasn't aware of the drag problem before. Are you saying it is caused by the crankset and bottom bracket? My understanding is that the Xootr Swift has 20" wheels compared to 16" on the Dahon. Does this factor at all in the improvement? Ps, I ride the Dahon at max pressure.

Joako

No, it has more to do with the integrated gear hub. I flipped both bikes and the Xootr wheel spinned for longer than the D3 wheel.

niggle

I agree with what you say re. the ride of small wheels and the effect this has on rolling resistance, however factor in suspension (tuned for road use) and things are rather different. With such bikes as the Reach, the Birdys or the Moultons you can run just as high pressures as the big wheelers and get an even better ride into the bargain. Also acceleration is improved by small, light wheels though this does mean they have a reduced flywheel effect.

jur

I have a distinct impression my Birdy (Kojak front, Marathon Plus rear) is a bit slower than my faster bikes (Swift, Moulton APB), but it is very hard to know if this is perception only or real. I have com pared the Birdy against my Swift while commuting, and the difference seemed close to indistinguishable. But I can't shake that feeling that it is a smidge slower. For example just yesterday I rode the Moulton and today the Birdy, and it just seems the Moulton pedals a little easier.

Very hard to make an objective call in the absence of a rigorous Stig test.

pibach

Yes. The Birdy has two critical design points.
1) the rear pivot is not placed such that the chain force is directed onto it (which does eliminate pedal impact on the suspension). You can setup a front chainring to fit this, but mostly it does not (probably with Rohloff it is possible?).

2) the front suspension has the pivot behind the wheel axle. Modern designs are the other way round, e.g., German-A force kilo (Dahon Jestream XP) or Pacific Reach. And dampening is simple elastomere. Overall this design results in some 'dive in' on changes in weight distribution which does consume some energy. Best way to compensate is to remain in the saddle an keep a steady cadence with a round spin.

Also, as the front comes closer on hills, a long bar reach does help. You could try fitting a drop bar or a bullhorn, these bars help.

Going downhills at >60 km/h is not very stable on most folders. You need a stiff front, at least. Folders that feature that are Bike Friday, Swift, or Airnimal. Birdy's front construction is a bit twitchy and folding/telescoping handlepost isn't stiff enough. You can however replace it by some single piece fork plus ahead stem which will make it much lighter and stiffer (but affects folding of course). See Birdy thread.

Furthermore I think the Rohloff isn't very efficient uphills. It cost you ~3% efficiency plus ~1kg extra weight.

feijai

The Xootr's wheel can hold a much larger degree of rotational momentum than the D3 wheel. How did you know you put the same amount of energy into each?

lz4005

If you had two bikes that were exactly the same (geometry, gear inches, weight, tire pressure, etc) in every way except for wheel diameter the difference in speed on smooth pavement would be almost nothing.

It is nearly impossible to have those two bikes.

stevegor

Jur,

If you like...I'll be the Stig and test all your bikes....just send'em up here....you know where I live

Kaito

When I was on my Mu P8 w/more upright positioning, and 8spds, I was able to keep up w/full sized road cyclist, but w/effort. When I switched to my Xootr Swift, I immediately noticed the bike, and set up allowed me to again keep up w/full sized bikes, but now with MUCH less effort.

IMHO, I'd say the difference between my Mu & Swift, that made the Swift more effecient was:
- Less rolling resistince w/Durano's, compared to the wider Marathon's on the Mu.
- More gearing on the Swift to find that perfect gear/cadence. (20spd vs's 8spd)
- More foward/less drag riding position on the Swift, compared to the upright, 'draggy' Mu.
- Just my opinion, but I also felt it much easier to get a more powerful pedal-stroke on the Swift.

I don't own a full size road bike, but last week I borrowed a friends full size bike w/the same exact gearing as my Swift, both front & rear. Only differences were the wheel size. (okay...so the wheel size will change the gearing...but both bikes have 53/39 front & 12-25 rear)

We did the same lunch-course that I ride w/my Swift. Granted the 700cc wheels did up the gearing on the full size bike, I didn't feel much 'faster' on it, nor did it make it easier to keep up w/my friend on his full sized bike.

There's alot more to getting an effecient ride that just wheel size.
just my 2yens worth..

havm66z

Which is worth more than 2 US ¢ (shock horror).

niggle

and totally impossible to find smooth tarmac where I live (hence my obsession with suspension).

jur

Just send me a pic of you in white leather suit with FF helmet under your arm and I'll shoot them over.

LWaB

The Marathon Plus is as slow as a wet week, particularly in small wheel sizes.