Author Topic: The REAL Weight Difference Between Derailleur and Pinion/Rohloff Bikes?  (Read 4669 times)

Andre Jute

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Following a link from Danneaux in a different thread, I came across this very interesting comparison, fully populated with real-world numbers, between the all-up weight of modern derailleur transmissions and the Rohloff/Pinion hub gearboxes. You're in for a few surprises, here:
https://www.cyclingabout.com/weight-difference-between-derailleur-pinion-rohloff-bikes/

Matt2matt2002

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Re: The REAL Weight Difference Between Derailleur and Pinion/Rohloff Bikes?
« Reply #1 on: December 28, 2019, 11:58:57 am »
Thanks Andre. Lots to take in here.
A good read to work off the turkey and stuffing.
All the best for 2020
Never drink and drive. You may hit a bump  and spill your drink

Andre Jute

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Re: The REAL Weight Difference Between Derailleur and Pinion/Rohloff Bikes?
« Reply #2 on: December 28, 2019, 11:51:40 pm »
That table certainly kills the "But a Rohloff is so much heavier" shibboleth.

I look forward to your 2020 tour reports, Matt.

Pavel

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Re: The REAL Weight Difference Between Derailleur and Pinion/Rohloff Bikes?
« Reply #3 on: December 29, 2019, 01:39:54 am »
My major was "Process Piping design".  Lots of metallurgy and mechanics ( mechanical physics, not auto mechanics :) ) The last project we did was designing a chain driven hoist.  I don't actually remember all that much about it, but one thing that does stand out in my mind from that was how unbelievably important the losses were from friction and how much of a wear difference it could make.  The chain deflection of a regular drive train is chain efficiency suicide.  My guess would be that everything else being equal (though it kind of can't be) the straight run on the Rohloff is probably worth four or five pounds worth of weight in the center of a wheel.  A chain deflecting as much as 10 and 11speed chain have to deflect is terrible for driveline efficiency, but somehow all these folks never seem to take that into account. 

Andre Jute

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Re: The REAL Weight Difference Between Derailleur and Pinion/Rohloff Bikes?
« Reply #4 on: December 29, 2019, 05:10:58 am »
...how unbelievably important the losses were from friction and how much of a wear difference it could make.  The chain deflection of a regular drive train is chain efficiency suicide.  My guess would be that everything else being equal (though it kind of can't be) the straight run on the Rohloff is probably worth four or five pounds worth of weight in the center of a wheel.  A chain deflecting as much as 10 and 11speed chain have to deflect is terrible for driveline efficiency, but somehow all these folks never seem to take that into account.

That's the cat among the pigeons! I wouldn't be surprised at all to discover Herr Rohloff knew this, and that the advantage of a non-deflecting chainline influenced the specification in the manual (and to OEMs) of a chainline straight to within 1mm max.

That article also claims, near the bottom, that the Pinion's greater friction losses than the Rohloff would be responsible for creating a disadvantage of several minutes over a derailleur bike on a mildly hilly course of 100km, compared to about a minute for the Rohloff.

All of that I consider theoretical, because the Rohloff either is, or can easily be made with say a Chainglider (or the lighter, zero friction, Country chaincase), as clean and therefore as efficient at any point during the "race" as at the beginning, whereas the derailleur efficiency falls off from the beginning and cumulatively over the course because it is impossible to keep it clean.

There was a point in my cycling history where I went from a Shimano Nexus in a Gazelle Toulouse to a very similar Trek stadsportief (city sports, basically a vacation bike for comfortable Dutch commuters) with the same gearbox but with fully automatic electronic shifting, which cut several minutes off a 45m ride I took every day at a time when there was very little traffic. The Rohloff cut that again. I have since then viewed the Rohloff as "suspiciously efficient" -- but I'm starting to understand why it is so efficient.

Thanks, Pavel; you're a Big Bang of illumination in the murk of bicycle lore.

Danneaux

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Re: The REAL Weight Difference Between Derailleur and Pinion/Rohloff Bikes?
« Reply #5 on: December 29, 2019, 09:26:50 am »
Andre,

For some years, the "Friction Facts" website published a series of reports on the friction levels of various components and lubes based on empirical testing; they were available for individual purchase and I bought most of them. Here is a little background on the former FF site: https://www.cyclingnews.com/features/friction-facts-measuring-drivetrain-efficiency/

The old FF site is still available through the Internet Wayback Machine here:
https://web.archive.org/web/20160307123619/http://www.friction-facts.com:80/test-results/individual-reports

Almost two years ago, the FrictionFacts site was sold to CeramicSpeed, makers of low-drag bearing assemblies and components containing the bearings
https://www.ceramicspeed.com/en/cycling/

The old FF technical reports are still available on the new CS website, now free of charge:
https://www.ceramicspeed.com/en/cycling/inside/test-data-reports/

Per Pavel's observations, I think you will find this report interesting: https://www.ceramicspeed.com/media/3502/cross-chaining-and-ring-size-report.pdf

Some of their observations are surprising on the face of it but make sense on further reflection. For example, in...
https://www.ceramicspeed.com/media/3494/bearing-lube-seals-full-report.pdf
...one of my favorite assembly and wet-weather lubes, Phil Tenacious Oil, was one of the least efficient bearing lubricants, with among the highest average frictional losses in the test group making it seem a poor choice -- except in wet weather, where its relatively high viscosity clings like grim death to my chain. In adverse conditions, an exposed lubed chain has less friction than one whose lubrication has been washed away by road splash and rain...but that is for chains, not bearings and especially not for shielded chains or bearings. As you read the reports, you'll become aware of methodological limitations (a "drop" of lube is not equal across all lubes due to variations in viscosity and may result in comparative under- or overfill of a given bearing set or type resulting in secondary losses due to things like bearing "churn") and that a given lubricant's efficacy is very much a matter of horses for courses and whether or not friction reduction is primary or secondary to other goals like lubrication life or waterproofness. Factors like ball diameter (a Big factor when paired with various viscosities of lubricant), ball count, type and tolerance of seals (if any) and bearing design (i.e. cup-and-cone versus deep-groove Conrad-style cartridge bearings with various seals) all affect friction. As a result the same lubricant can have relatively low efficiency with some bearing combinations and much higher efficiency in others. Hub and bottom brackets have different requirements than chain rollers.
=====
I still have some older cup-and-cone hubs (Campagnolo Record, old Shimano 600, SunTour Superbe non-Pro, Sunshine/Sanshin Pro-Am) with holes factory-drilled in the center of the hub shell, covered by spring-steel clips. The idea being to grease the hubs for road use but to replace the grease with oil applied via the central clip-covered port for occasions where minimum friction was desirable -- things like Keirin racing (a Japanese 2km indoor track cycling event designed particularly for parimutuel betting) and hour-record attempts back in the day. I used such hubs for touring and commuting throughout the late '70s and early '80s. They were unsealed (I would sometimes wrap grease-soaked pipe cleaners in a spiral around the bearing dust caps for a modicum of weather sealing on commutes and wet tours), so I would occasionally use the oil ports to flush the hub with fresh, thick oil midway on particularly wet tours; it flushed any water or contaminants from the inside-out. The oiling ports worked well for that but I never noticed any difference in wheel friction in my touring use as there were too many other factors that muddied those waters -- things like rough roads and potholes.

Another site to view is ZeroFriction Cycling: https://zerofrictioncycling.com.au/ They have a little different take on things geared toward sales but with some interesting FAQs and observations as well.

A couple addenda:
1) Like my Nomad with Rohloff, my Fixie has a perfectly straight chainline but no gearbox of any kind, no idler or tensioner, nothing but the chain, chainring and fixed sprocket. When properly lubed it is absolutely silent to my ears while riding and I have to be careful to ring my bell as I close on pedestrians who simply don't hear my approach otherwise. The gears last a long time, the chain less so because it has to resist not only forward pedaling forces but also rearward ones as momentum carries my legs through the top- and bottom dead-centers and as I apply rearward force to avoid excessive downhill speeds and to aid rim braking.

 2) My randonneur (long distance day ride) bikes are setup with half-step and granny gearing, the chainlines offset toward the centerlines of the bikes and the most frequently used (cruising) gear combinations chosen to run with minimal deflection and so minimal friction; my favorites run in a straight line like my Fixie. As a result, drivetrain noise is minimal and with deliberately chosen large-diameter gears, component life has proven to be phenomenal compared to my derailleur bikes with crossover gearing that often runs at larger chain-deflection angles. Although the physically larger components are heavier (and being older and mostly non-indexed, also thicker), their reduced friction is noticeable and works nicely to offset the added weight as lifespan is increased. Larger derailleur pulleys help a lot too, minimizing the angles the chain must wrap around the rear derailleur's jockey and tension pulleys. Half-step gearing also means I have more usable gear combinations than I do on my bikes with crossover gearing and the gears are more readily available to me with less complicated shifting (13 usable out of 15 possible combinations for a 3x5 half-step discounting duplicates and excessive cross-chaining, 15/18 for a 3x6, and 18/21 for a 3x7 versus "only" 15/27 for my 3x9 crossover setup). For fun, I am currently setting up a go-fast bike with a 1x10, but the chainline deflection looks so scary in all but a couple combos, I am inclined to abandon the project and return to something more favorable.

Best,

Dan.

PH

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Re: The REAL Weight Difference Between Derailleur and Pinion/Rohloff Bikes?
« Reply #6 on: December 29, 2019, 11:44:53 am »
Re weight - I may have posted this before.  last year I converted my Airnimal folder from 3X9 with a decent level of touring components, to a Rohloff that needed a tensioner but not the long torque arm.  I meticulously weighed everything that cam off and everything that was added, also the complete bike before and after as a back up.  Depending on whether you trust my kitchen scales for the components or my bathroom scales for the complete bike, the Rohloff added either 420 or 460g. 
Re everything else - I like riding it and nothing else matters.

Andre Jute

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Re: The REAL Weight Difference Between Derailleur and Pinion/Rohloff Bikes?
« Reply #7 on: December 30, 2019, 12:42:55 am »
Depending on whether you trust my kitchen scales for the components or my bathroom scales for the complete bike, the Rohloff added either 420 or 460g.

Who cares about 40gr, or 440gr for that matter, on a component with so many advantages?

Thanks for posting the confirmatory details again, PH.

Re everything else - I like riding it and nothing else matters.

+1
« Last Edit: December 30, 2019, 12:45:03 am by Andre Jute »

Andre Jute

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Re: The REAL Weight Difference Between Derailleur and Pinion/Rohloff Bikes?
« Reply #8 on: December 30, 2019, 12:51:30 am »
As we've come to expect from you, Dan, that's a fabulously rich resource on friction you have on tap there. I've saved all of it for reading on my treadmill, where I will have an uninterrupted hour twice a day to think about what I read. But my first impression is:

I will not be buying an 11-speed group! Nor 10-speed, nor even 9-speed. See "Effects of Lateral Chain Misalignment (Cross-Chaining) on Drivetrain Efficiency & Effects of Chainring Size on Drivetrain Efficiency" at:
https://www.ceramicspeed.com/media/3502/cross-chaining-and-ring-size-report.pdf

energyman

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Re: The REAL Weight Difference Between Derailleur and Pinion/Rohloff Bikes?
« Reply #9 on: December 30, 2019, 02:11:37 pm »
As far as I'm concerned Rohloff Rules !
No other gearing system comes anywhere near it.