Shifting gear under load

[Jackware]

Isn't the important moment to lighten the pedal is as the chain moves between the cogs?
As soon as the chain is engaging the teeth on just one cog it's not so critical that the power is increased?

 

[Waynemarlow]

No. Mate. I'm not agreeing with you at all. I'm suggesting you educate yourself in basic engineering principles before talking absolute bobbins

But Gary you won’t even define your definition of load, pity might have been entertaining but then I guess it would be just a Google cut and paste.

Now “Bobbins”, I know even more, can I bore you with the details of CVT gearboxes, As Gary’s knowledgeable reply is based on analogues and he is the only respondent, I think this is going way over most heads, it’s probably better to not bother to continue.

Ah well.

 

[Waynemarlow]

Isn't the important moment to lighten the pedal is as the chain moves between the cogs?
As soon as the chain is engaging the teeth on just one cog it's not so critical that the power is increased?

it’s never just 1 tooth, the point loading created by just the rider would soon see that off. The only difference to the gears is the spread of load over fewer or more teeth. The main reason for backing off is to protect the chain side loading up individual chain pin points.

 

[Zimmerframe]

Going out on a limb here, but this really reads that you're purposefully going out of your way to just talk total bollox just to stir a thread up here @Waynemarlow ??? You've literally taken people's comments and spun them around to completely the opposite of what was clearly said to try to make them fit with what you're saying.

I admire your determination, or humour ? I can't decide ?

it’s never just 1 tooth, the point loading created by just the rider would soon see that off. The only difference to the gears is the spread of load over fewer or more teeth. The main reason for backing off is to protect the chain side loading up individual chain pin points.

Is just total tosh. When you change gear, the speed of the chainring will be forced to change - relating to your earlier comments. As you change gear, the chain will be spread between two different cogs on the cassette as the change happens. Pedalling under load will also be putting extreme load and wear on all the contact teeth of both cogs, not just the chain - which will be going through it's own little world of hell.

You talk about evidence. Just look at the life span of chains and cassettes of the newby's banging through the gears at full load in Turbo and getting 100-300km's out of both.

Have no idea at all why you've brought CVT gearboxes into it. They have absolutely no comparison to cassettes in how they work. If you've got a nuvinci, fine change away under load.

 

[Waynemarlow]

Is just total tosh. When you change gear, the speed of the chainring will be forced to change - relating to your earlier comments. As you change gear, the chain will be spread between two different cogs on the cassette as the change happens. Pedalling under load will also be putting extreme load and wear on all the contact teeth of both cogs, not just the chain - which will be going through it's own little world of hell.

Interesting, lets deal with the larger gears where diameter is not really going to come into play. If the chain is say interconnected with 20 pins touching the gear ( point of contact, the pressure points ) of the 42 tooth rear chain ring, you would agree the load created by the rider + motor is spread across 20 pins ?

Now if we change gears to say the 38T ring, tell me at say the 1/2 way point of shifting ie the chain is sitting half on the 42T and the other half on the 38T gear, how many pins will be in contact with the cassette ( remember the cassette is locked to the rear hub ) ?

Variable bobbins are part of the CVT transmission, sorry it was just a little dig at Gary.

 

[Gary]

Make as many digs as you want. The more you do the more of an idiot you'll seem.

 

[DtEW]

Conventional wisdom (and the predominant view in this thread) remains right. It is good practice to reduce torque as one is shifting (both up and down) because in the process of shifting, the actual load-carrying teeth on the existing ratio is reduced one-by-one until the entire chain goes to the new radius on the loaded side. There is a point in every shift, which is near the end of the shift, in which the entirety of chain tension (and drive load) is borne by only one cog tooth. For all the design and engineering that goes into a modern cassette to smooth shifts, this reality remains because it is inherent to a chain derailment system. People confuse chain engagement with load-carrying. Load-carrying isn't even that straightforward between the engaged teeth on a single speed.

 

[Bearing Man]

 

[Waynemarlow]

There is a point in every shift, which is near the end of the shift, in which the entirety of chain tension (and drive load) is borne by only one cog tooth. For all the design and engineering that goes into a modern cassette to smooth shifts, this reality remains because it is inherent to a chain derailment system. People confuse chain engagement with load-carrying.

Interesting and a big statement, any chance you can link me to a research paper or such like that supports your argument. If indeed it is the case ( and possible ) then it can only be the very last tooth to disengage. We definitely need to support this with proven sources as it has other implications.

But this whole Cassette and tooth contact whilst changing is almost irrelevant to my hypothesis as that will happen with or without a motor. What I’m hypothetically saying is that with a motor involved, all the previous knowledge we knew about chain contact and wear now has another factor, that of the motor adding quite large amounts of power in a quick burst just after we change gear and start to pedal again. If riders are backing off momentarily, changing gear and then reapplying pedalling and power, we are simply talking about just 1 gear, the chain will already have changed fully.

Certainly both the Bafang and Bosch I have ridden ( the TSDZ2 has a facility for the user to alter the engine characteristics to dial it out ) seem to have this overly eagerness to catch up the cadence and give a little surge of power. That extra few seconds of extra power is probably worth the equivalent of 10 full revolutions of pressure friction.

My argument which seems either not well explained by me or that it is falling on deaf ears of those used to analogue bikes, is that to simply change gears at normal loadings will mean the motor does not surge to catch up and in effect it’s just another revolution of the cassette. At no point will there be a high loading for a short period.

 

[Jimbo Vills]

Interesting and a big statement, any chance you can link me to a research paper or such like that supports your argument. If indeed it is the case ( and possible ) then it can only be the very last tooth to disengage. We definitely need to support this with proven sources as it has other implications.

But this whole Cassette and tooth contact whilst changing is almost irrelevant to my hypothesis as that will happen with or without a motor. What I’m hypothetically saying is that with a motor involved, all the previous knowledge we knew about chain contact and wear now has another factor, that of the motor adding quite large amounts of power in a quick burst just after we change gear and start to pedal again. If riders are backing off momentarily, changing gear and then reapplying pedalling and power, we are simply talking about just 1 gear, the chain will already have changed fully.

Certainly both the Bafang and Bosch I have ridden ( the TSDZ2 has a facility for the user to alter the engine characteristics to dial it out ) seem to have this overly eagerness to catch up the cadence and give a little surge of power. That extra few seconds of extra power is probably worth the equivalent of 10 full revolutions of pressure friction.

My argument which seems either not well explained by me or that it is falling on deaf ears of those used to analogue bikes, is that to simply change gears at normal loadings will mean the motor does not surge to catch up and in effect it’s just another revolution of the cassette. At no point will there be a high loading for a short period.

I think it’s falling on deaf ears because you completely dismiss others points and demand ‘research papers’ to support someone’s thought process….

Then ironically make a whole case for your thoughts on a Hypothetical basis.



I never knew before buying a eMTB that gear changing could be so technical

 

[Zimmerframe]

all the previous knowledge we knew about chain contact and wear now has another factor, that of the motor adding quite large amounts of power in a quick burst just after we change gear and start to pedal again.

The main issue with a motor compared to a none motored bike, is that for the majority of us lazy b4stards, the motor adds considerably more power/force into the equation than would be there without a motor. Add in that many motors incorporate overrun to get our lazy asses over rocks and such like and it's therefore more difficult to just "ease off the power" as you would with a conventional bike where you have 100% direct control. Instead you have a situation where it's like riding a tandem with a pissed Gorilla whilst it's watching bambam's hairy porn collection on their gorilla phone..

To say that we now have a new factor - that of the motor adding quite a large amount of torque just after we change gear and that this could cause more cassette wear than randomly and carelessly mashing tiny metal parts together at high speed seems a bit bonkers ?? This is only the same as everytime we ease off pedalling and then pedal again - which for me can happen thousands of times on a ride. I don't think anyone rides their bike thinking "oh ohh, can't ease off, mustn't ease off, must maintain constant power for the whole ride or I'll wear my cassette ....". If my ride was like that I think I'd be giving up the bike and booking myself and the Gorilla into a roadside hotel for some form of adrenaline rush...

 

[Waynemarlow]

I think it’s falling on deaf ears because you completely dismiss others points and demand ‘research papers’ to support someone’s thought process….

Not at all, the poster sounds very plausible and indeed may have information that I have been looking for on the internet, but cannot find. I have searched that very topic for another reason.

Fair enough guys, the idea has been outed, dissed by yourselves, lets go riding and not worry about it.

 

[Jimbo Vills]

Not at all, the poster sounds very plausible and indeed may have information that I have been looking for on the internet, but cannot find. I have searched that very topic for another reason.

Fair enough guys, the idea has been outed, dissed by yourselves, lets go riding and not worry about it.

i didn't 'diss' anything. Just made observation on your approach.

Enjoy the ride mate. try not to grind those gears

 

[TEE]

You are going to snap your chain so dont. :'D

 

[lightning]

Let me add something here, it's difficult to back off the power when changing up through the cassette while accelerating on my Ebike.

Reason? The motor power doesn't stop instantly when you back off, well it doesn't on my E8000 anyhow, there's a slight delay.

This works well to make power transmission smooth, but it's next to impossible to change up through the cassette without doing it under power, unless you pretty much stop all pedalling effort, which makes for a bad riding experience.

So far, 600 miles on my new chain/cassette, still shifting up under full power (trail mode, wouldn't do it in turbo) and the chain is still at 0.25 on the chain checker, as in no measurable wear.

l've never snapped a chain. As for the cassette, l don't know, will update when it finally needs a new chain fitting.

l have to add, that l am quite light at under 70kg, and while l am not by any means a slow rider, l am not up there with the kinds of full on shredding l see on YouTube.

l also very rarely use Turbo, and l've got it set at 200% anyhow which is only 2/3 of the maximum.
Trail is set at 125%

So l am not taking the transmission to the limit by any means.

 

[RustyIron]

you're purposefully going out of your way to just talk total bollox

Maybe you just don't understand because you didn't "think it through on an engineering basis," and you didn't support your contention with "a research paper or such like that."

 

[7869hodgy]

I sold my E+1 in the spring. It had done 2400km almost flawlessly and had a new drivetrain fitted 500km before I sold it. Changed it more as preventative maintenance rather than because of wear. I was pretty sympathetic mechanically as had had no failures in my ownership. Always tried not to change under load but occasionally not always possible as you’ll know.

The guy who bought it reported back 24 hours later saying he’d snapped the chain whilst changing gear. He seemed a “gung ho” type of chap and wasn’t overly bothered.

It’s pretty simple. Don’t change under load with <85nm going through.

(Don’t take on an idiot, he’ll beat you with experience )