Is there a perfect bike for commuting?

General cycling advice ( NOT technical ! )
thelawnet
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Re: Is there a perfect bike for commuting?

Postby thelawnet » 4 Feb 2019, 11:54pm

The utility cyclist wrote:Stating the extra weight doesn't make any difference is your opinion, it makes a difference, it makes a difference when cycling, when lifting, ordinary folk that don't cycle much DO notice the difference between a heavy Dutch bike and one that isn't, it's noticeable especially when you add in the draggy dynamo wheel and heavy duty tyres which pinch even more of your effort.
15 Watts of differential in energy absorbed by heavy duty tyres alone is a significant factor when your average joe/people that only ride short distances are maybe producing 100Watts.


It doesn't work like that though....

I'm not sure precisely what tyres you are proposing for your lightweight hybrid - presumably NOT Continental GPs or whatever.

At any rate when it comes to tyres it is a compromise between puncture resistance, longevity and speed.

Let's say you have 37-622 Schwalbe Marathon Greenguards on your Dutch bike.

The coefficient of rolling resistance at 60psi is 0.00638

https://www.bicyclerollingresistance.co ... athon-2015

And then you have some sort of lightweight hybrid with Grand Prix 4000s II, to use a fairly extreme example (the Marathon treads are 3x thicker, and the sidewalls twice as thick). The CRR at 95psi is around 0.00365. https://www.bicyclerollingresistance.co ... i-23-25-28

In terms of the efficiency of hubs vs. derailleurs, for lower power outputs (80W), they are similar. http://www.ihpva.org/HParchive/PDF/hp52-2001.pdf

In real conditions, a hub gear system will be more efficient than a typical rusty poorly maintained derailleur system.

An efficient dynamo hub costs almost nothing when switched off, and 5W @ 100W, switched on.

So let's plug in these numbers:

60kg rider, 11kg lightweight hybrid

CdA = 0.5 m^2 (fairly upright)

CRR = 0.00365

Drivetrain loss: 10% (best case, with well maintained system)

https://www.gribble.org/cycling/power_v_speed.html

80W = 12.9mph, on a flat road

80W goes to:

15W = rolling resistance (GP4000s)
8W= drivetrain (derailleur)
58W = wind resistance

And then:

60kg rider, 17kg Dutch bike

CdA = 0.6 m^2 (very upright)

CRR = 0.00638 (Marathons)

Drivetrain loss: 15% (worst case, with light on)

80W = 11.0mph

Where does the 80W go?:

24W= rolling resistance (Marathons)
13W = hub gear drivetrain + dynamo
43W = wind resistance

Firstly, very heavy weight tyres are not absorbing an extra 15W at low speeds. Rolling resistance is proportional to speed; the numbers from bicyclerollingresistance are measured at 18mph. At lower speeds, rolling resistance is less. At 11mph, 43W is spent on fighting wind resistance. If we were to switch to short-lived, puncture-prone racing tyres on the same bike we'd gain just 0.7mph.

Obviously, then NOT fitting heavy duty tyres on a bike for someone producing only 80 or 100 watts is very stupid, because there's a good chance they'll struggle with mending a puncture and, well, the extra 9W you can buy them by reducing the practicality of their bicycle is eaten up by a 1 kph speed increase, which nobody would notice.

When going DOWN a hill, heavy tyres aren't significant either - here it's air resistance versus gravity. A very upright and draggy bike (and I have one) will not accelerate very much, while a crouched aero bike will accelerate quickly.

Going UP hill, heavy tyres are less of an issue than on the flat - at 100W/60kg/5% hill, you will do 4.3mph on a upright heavy (17kg) Dutch bike with Marathons + lights on, and 5.2mph on a lightweight 11kg hybrid with GP4000's. Faster, but hardly supersonic in comparison.

On a short journey, speeds aren't in any case particularly relevant.

Over some longer journey they become slightly more so, but as per the above:

(a) weight isn't as significant as it seems, because even in the rather generous case towards the lightweight bike, of a 60kg rider and a 11kg vs. 17kg bike, the heavy bike only adds 10% more weight to the system, which means a loss of speed of less than 10%, which really is not a big deal.
(b) wind resistance is significant in cycling, except when cycling uphill very slowly, but it isn't all that relevant to our 80W cyclist, since they don't produce enough power to get up to significant speeds and hence have to battle significant wind resistance, so an upright stance is not an impediment to their progress because at slow speeds not much power is required in the first place.
(c) high-quality heavy-weight tyres are better than lightweight puncture-prone ones unless you want to eek out the maximum performance from your bike. For example, for an racing bike (CdA 0.39m^2) with 95% efficiency drivetrain, the Marathons would be at 19.1mph at 200W on the flat, and the GP4000s 19.8mph. Not a huge difference, but if you are racing then why not. Plainly for more practical applications, lightweight tyres are not a good choice.
(d) derailleur systems are VERY efficient at athletic outputs of say 300W with well-chosen gears: a 44/16 derailleur gear (with a 44/32/22 crankset & 12-34 cassette) is given as 97.2% efficient at 300W. The 32/16 at 80W, however, is only 90.9% efficient, and worse again in typical conditions.

I would note also the numbers for efficiency for the small cog: 22/12 is 91.8% efficient at 150W, 32/12 is 91.0% efficient, and 44/12 is 93.3% efficient. I assume modern 11t cogs are even worse.

The point at which these considerations change is when you need to cover relatively long distances, in which case significant speed improvements are possible IF you produce more power than these numbers AND can get into a more aero position.

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SimonCelsa
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Re: Is there a perfect bike for commuting?

Postby SimonCelsa » 5 Feb 2019, 5:49am

a) weight isn't as significant as it seems, because even in the rather generous case towards the lightweight bike, of a 60kg rider and a 11kg vs. 17kg bike, the heavy bike only adds 10% more weight to the system, which means a loss of speed of less than 10%, which really is not a big deal.


I am not a weight weenie & a couple of my rides are well over 15kg. However I would say that 12.9mph vs 11.0mph is a considerable difference (in a cycling context) & one which would make a huge difference to someone riding a long audax or the 2019 Paris Brest Paris (say). It is the difference between a luxurious deep sleep in a roadside inn or a quick 40 winks in a wee stained bus shelter!!

I realise you allude to this in your final sentence
The point at which these considerations change is when you need to cover relatively long distances,


but the speed differential in your example is more in the region of 17%, & if I could get that on my bank account then it would definitely not be insignificant!

Otherwise an interesting post

thelawnet
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Re: Is there a perfect bike for commuting?

Postby thelawnet » 5 Feb 2019, 11:03am

SimonCelsa wrote:but the speed differential in your example is more in the region of 17%, & if I could get that on my bank account then it would definitely not be insignificant!



Ah but your bank account doesn't make you mend punctures on your impractical tyres. :wink:

simonhill
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Re: Is there a perfect bike for commuting?

Postby simonhill » 6 Feb 2019, 2:31pm

No one has mentioned Japanese commuter bikes. Probably the most numerous in the developed world. The top of the range ones have a lightweight steel frame, hub gears, brakes and dynamos. Lesser models only rear hub brake and bottle dynamo.

I think the Japanese regularly replace these as I often see old ones in the poorer countries of SE Asia. Here in Burma, most of the locals are riding them and yesterday I saw a storeroom full of old ones awaiting sprucing up.

As we sink into a developing country, maybe someone could import a few container fulls and start selling them to the populace.

Ontherivet77
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Re: Is there a perfect bike for commuting?

Postby Ontherivet77 » 8 Feb 2019, 9:51am

I currently use a stripped down Touring bike, which has advantages of having full mudguards, is the style of bike I'm most used to and is fairly low in weight whilst having decent puncture proof and grippy tyres. I have used quite a few different styles in the past so here's my tuppence.

Regards, Dutch Bikes my wife has a Pashley, which although extremely heavy, rides like a Rolls Royce, is very stable to ride and so may suit a novice rider and comes set up with full guards, rack, lights etc. I wouldn't fancy it on a long hilly commute, but for something short and flat it would be okay. It also would not fit in a upright bike locker, if that is an option at work.

Mountain Bikes (ATB). I found this to be easily the worst bike to commute on. Awful on the road without a change of tyres and a pig to fit decent mudguards on. This was a 26 inch wheel bike though and the modern bigger wheel bikes roll a lot more smoothly I'm told. The big wheel ones don't fit in upright bike lockers though.

Lightweight hybrid bike. Probably the best bike I've used, once I stuck a set of mudguards on it. It had very powerful v brakes was nippy and the short flat bar gave me a lot of control in traffic. Second to this was a standard drop bar road/race bike with a set of race guards fitted, very light, nippy and good for use in traffic.

Scunnered
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Re: Is there a perfect bike for commuting?

Postby Scunnered » 8 Feb 2019, 12:00pm

thelawnet wrote:
CRR = 0.00365 (GP4000s)

CRR = 0.00638 (Marathons)

Firstly, very heavy weight tyres are not absorbing an extra 15W at low speeds. Rolling resistance is proportional to speed; the numbers from bicyclerollingresistance are measured at 18mph. At lower speeds, rolling resistance is less. If we were to switch to short-lived, puncture-prone racing tyres on the same bike we'd gain just 0.7mph.


There is a simple way to assess rolling resistance at different speeds: the energy required to overcome rolling resistance for a given distance is proportional to the rolling resistance coefficient.

Now the coefficient of rolling resistance does increase a little with speed, but to a first approximation:

Cycling 1 mile on Marathons will require 0.00638/0.00365 = 1.75 times as much energy as the GP4000s (to overcome the rolling resistance).

However, this additional energy is pretty small compared to that required to overcome air resistance (which is highly dependent on speed), so the puncture resistant tyres are entirely justified on a commuter.

londoncommuter0000
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Re: Is there a perfect bike for commuting?

Postby londoncommuter0000 » 8 Feb 2019, 12:38pm

Ryan1967 wrote:Is there a perfect bike for commuting? folding/road or just your average normal bike?


I've heard good things from colleagues about the PlanetX 'London Road'

https://www.planetx.co.uk/c/q/bikes/road-bikes/london-road

I commute on a Giant Defy, and (when my legs and lungs allow it) a Genesis single speed. They are both fantastic machines for the commute, although they feel very different.
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London is a cesspit

Mares
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Re: Is there a perfect bike for commuting?

Postby Mares » 8 Feb 2019, 1:27pm

Cyclo-cross or gravel bike.

Suitable for off road commute or sections of commute.
Variety of hand positions.
More suitable than a narrow tyred road bike for 99% of on-road sections.

If you can, run tubeless. I do on 38mm Panaracer Gravelkings (SK in winter, Slicks in summer) and they have been flawless.

londoncommuter0000
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Re: Is there a perfect bike for commuting?

Postby londoncommuter0000 » 8 Feb 2019, 1:36pm

Mares wrote:Cyclo-cross or gravel bike.

Suitable for off road commute or sections of commute.
Variety of hand positions.
More suitable than a narrow tyred road bike for 99% of on-road sections.

If you can, run tubeless. I do on 38mm Panaracer Gravelkings (SK in winter, Slicks in summer) and they have been flawless.


Just sent a message on Signal to my wife.

'I have some bad news for you. I'm buying a new bike'. :D

*fires up PlanetX website*
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Surly LHT | Genesis Flyer | Giant Defy Advanced Pro | CBoardman 29er Pro
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pjclinch
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Re: Is there a perfect bike for commuting?

Postby pjclinch » 8 Feb 2019, 2:04pm

Mares wrote:Cyclo-cross or gravel bike.

Suitable for off road commute or sections of commute.
Variety of hand positions.
More suitable than a narrow tyred road bike for 99% of on-road sections.

If you can, run tubeless. I do on 38mm Panaracer Gravelkings (SK in winter, Slicks in summer) and they have been flawless.


The "variety of hand positions" touted for drops is only relevant if you're riding the sort of rides where being able to get as aero as possible for significant chunks of the ride is important. Commuting is not, typically, such a thing.

My Moulton TSR has 28mm Duranos. It copes with off-road ridden at commute pace with no problems at all. My Brom copes with off-road ridden at commute pace with no trouble at all. My recumbent tourer and freight bikes cope with off-road ridden at commute pace with no trouble at all, None of them would be much good in a 'cross race, but unless you're being fabulously contrived or have a very unusual commute that's no really relevant. And where you really cut time by being on a 'cross bike, you'll lost it all washing and changing at each end unless "mud" is part of your employer's dress code.

Pete.
Often seen riding a bike around Dundee...

Vorpal
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Re: Is there a perfect bike for commuting?

Postby Vorpal » 8 Feb 2019, 2:43pm

The perfect bike for commuting?


One that gets used. 8)
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PT1029
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Re: Is there a perfect bike for commuting?

Postby PT1029 » 8 Feb 2019, 8:07pm

Not read all the posts... but don't commute with dual pivots and no mudguards. At work every winter I (and a few other on this forum I expect) get quite a few seized up front and rear dual pivot calipers (and a few other designs as well). Sometimes they unseize, often they don't. Then it is complete dismantle (usually not economic) or new calipers.

Brucey
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Re: Is there a perfect bike for commuting?

Postby Brucey » 8 Feb 2019, 9:20pm

+1 on that

cheers
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Mares
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Re: Is there a perfect bike for commuting?

Postby Mares » 9 Feb 2019, 10:36am

pjclinch wrote:
Mares wrote:Cyclo-cross or gravel bike.


Pete.



I'm sorry.

I didn't realise this was a right/wrong quiz.

I replied to the OP with my opinion and my 17 years commuting experience.

Needless to say you are wrong. Bars with drops offer a variety of different positions when compared to flat bars.

I believe the OP wanted to know if there was a perfect bike for commuting. Not who owns loads of obscure bike types.

Having used road bikes, hybrid bikes, mountain bikes and cross bikes for commuting I can say without a shadow of a doubt that a cross bike on 38mm tubeless tyres is the perfect bike for commuting.

Even if you are only on road.

I run them at 30psi and they're smooth and roll easily. So much so I have a variety of local KOM's on this setup.

And I did a local 100mike ride averaging 20mph.

And I can ride on gravel/snow/mud/ice with no issues.

All on one bike. As OP asked.

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The utility cyclist
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Re: Is there a perfect bike for commuting?

Postby The utility cyclist » 9 Feb 2019, 2:13pm

I can have 4 hand positions on my flat bar hybrid and that's without bar ends, how many do you have on you drop bar?