wheel and gear problems in Cambodia

beaker

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Aug 11, 2018
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Has anyone put a 26" wheel hub motor on a bike with 27.5" ?

When the original bike has 9 gear rear and motor can only have 5-6 or 7 gears how have you handled that ?

Can the stock 9 gear derailer and shifter be adjusted to work with 5-6 or 7 gears?
 
size of wheel is no problem, if it is disc brake,but if rim brake you have a problem,
deralier should be able to be adjusted to accomodate less movement.

On a side note are you beaker from a well known forum in Cambodia who sometimes has travel arranging problems??
 
beaker said:
Can the stock 9 gear derailer and shifter be adjusted to work with 5-6 or 7 gears?

No. The derailleur and chain should work, but you'll need a shifter that matches the number of gears on the wheel you use. (Or a friction shifter.)
 
andy1956 said:
deralier should be able to be adjusted to accomodate less movement.

https://sheldonbrown.com/speeds.html
Within a given brand/style of rear derailer, all "speed numbers" are generally interchangeable.
 
I believe this is what chalo's talking about:
sheldon brown said:
Indexed Shifters These need to have the spacing of detents ("clicks") to match the system they'll be used with. This usually goes along with the correct number of clicks -- though a shifter with an extra click also can work, as long as the spacing is OK. (Friction shifters have no compatibility issues, they work with everything.)

My guess is, no way are we talking about "a shifter with an extra click", the spacing is guaranteed to just be wrong. See Sheldon Brown cassette spacing chart. 9 speeds are 4.34 or 4.55 mm. 5 and 6 are mostly 5.5mm, 7 is remarkably standardized at 5mm. So the original 9-speed shifter indexing isn't going to work with a normal 5, 6 or 7 speed cluster, you'd just have to replace it (unless it was friction to start with.) Not the derailleur, the shifter.
 
beaker said:
Can the stock 9 gear derailer and shifter be adjusted to work with 5-6 or 7 gears?

If you want the shifter to work properly with one click = one shift, then no. If you are a bit tolerant and don't mind some gears requiring two clicks, then yes. In other words, it will work (at least mine does), just not quite as designed. My original plan was to change the 9 gear indexer to a friction shifter, but it has been working well enough for me. I'm no longer motivated to make the change. Many people may find imperfect index shifting unacceptable. But I've spent about 99% of my riding time using friction shifters, so the imperfect operation doesn't bug me at all.
 
wturber said:
Many people may find imperfect index shifting unacceptable. But I've spent about 99% of my riding time using friction shifters, so the imperfect operation doesn't bug me at all.

Noisy chain and sprocket operation, stuttering, and skipping are more serious than a mind it/don't mind it issue. It greatly accelerates wear and tear on the components when the derailleur is constantly guiding the chain to an in-between position that doesn't correspond with a sprocket. Lightly engaging the shift-assisting features on the chain and sprockets without actually shifting gradually wears those features away. In a worst case, the chain can skip or drop off when you're standing on the pedals to get up to speed, and a crash results.

Friction shifting allows you to make minor trim adjustments for quiet, smooth operation. Incorrect index shifting doesn't. That's why early index shifters came with a friction mode that could be enabled in case of system damage that misaligned the index positions from the sprockets.
 
It more or less works to run a 26" rear wheel in a 27.5 bike, if you have disc brakes. Put a big fat tire on it to make the diameter of the wheel closer to normal, and maybe a skinny one up front. Too much drop in the rear will make the bike ride funny. Don't put a front motor on that bike, unless its the right size. Drop in front will make you endo the bike too easy.

As for the gears, 9 speed running a 7 speed gear is just too much difference in chain size. You will need to change chain, rear derailleur and shifter. Front derailleur can stay same, though it will be skinny and fussy about adjustment.

8 speed bikes can run 7 gears more or less ok, but far from perfect.
 
Chalo said:
wturber said:
Many people may find imperfect index shifting unacceptable. But I've spent about 99% of my riding time using friction shifters, so the imperfect operation doesn't bug me at all.

Noisy chain and sprocket operation, stuttering, and skipping are more serious than a mind it/don't mind it issue. It greatly accelerates wear and tear on the components when the derailleur is constantly guiding the chain to an in-between position that doesn't correspond with a sprocket. Lightly engaging the shift-assisting features on the chain and sprockets without actually shifting gradually wears those features away. In a worst case, the chain can skip or drop off when you're standing on the pedals to get up to speed, and a crash results.

Friction shifting allows you to make minor trim adjustments for quiet, smooth operation. Incorrect index shifting doesn't. That's why early index shifters came with a friction mode that could be enabled in case of system damage that misaligned the index positions from the sprockets.

Here's the problem. My system wasn't noisy, didn't stutter, and only skipped in two middle to low gears - which was the "imperfection" that I was dealing with. And that skipping had always gone away with one click up or down. After that, no noise, stutter or skip. The system ran as quietly as I could have ever managed to make it run with a manual friction shifter. I switched to a new 7 speed chain way back when I changed chainring and added the motor.

I'm posting at this later time because I wanted to observe for a few days to make sure I wasn't the "frog in the pot" and hadn't just tuned a noisy and problematic drive train out over time after having gotten used to it. Nope. I could shift so that the system was quiet and reliable in six of the seven gears (I had locked out the lowest gear). That begs the question of how things could run quietly given the spacing differences. My best guess is that there's enough slop in my old derailer and its jockey wheels to allow the chain to shift side to side a bit and fine a smooth "slot" in which to run.

Nonetheless, I had intended to replace the shifter way back when and this got me looking at shifter options again. I found that for less than $20 I could buy a 7 speed Shimano Rapid Fire shifter from Performance Bike in Scottsdale. So that's what I did a couple days ago. I installed it this morning and have eliminated the middle shift sequence ambiguity. And as a minor bonus it turns out, the little gear indication window is placed differently (low side rather than high side)and I can now actually see it and confirm the gear I'm in. That might be handy now and then at stops.

Anyway, for the OP, the shifter was the Shimano Acera SL-M310 Rapid Fire Shifter that you can pick up at probably any local bike shop (not sure about Cambodia - maybe you'd need to order it?), and the freewheel I'm using is the 7 speed DNP Epoch with 11 tooth high gear that I got from Grin. While that may not be a great freewheel, it is head and shoulders better than the piece of garbage that came with my kit. It has the guide ramps that make shifting smoother and more accurate.
 
999zip999 said:
Dnp has a 9speed 11t freewheel . I would use a friction shifters old school.

The 9 speed has a 4 mm higher stack height (42mm). Depending on your frame and motor, that may or may not matter. I know on my bike it would create a problem. The 38mm 7 speed I have just barely fits. Making both the freewheel and disc brakes both fit came down to a millimeter or so of spacing adjustments.

Now that I'm full time PAS, I'm using lower gears off the line since it takes almost half a crank for the motor to kick in. This only really matters when I'm in a car lane at moderately busy intersection where I want to clear the intersection and get up to speed quickly. In that situation, that first partial pedal stroke can seem like it takes "forever" if you are in a tall gear with an SUV breathing down your back. So I start in a very short (low) gear. Given that,I now have to zip up through the gears quickly as I accelerate through the intersection and get up to speed in an attempt to make it easier for cars to comfortably pass me with good side-to-bike clearance. This is a situation where Class 2 & 3 PAS requirements are fundamentally less effective and slightly less safe IMO. Anyway, I've grown to really like clicking through gears in this kind of situation. If it weren't for that, I'd probably go along with using friction shifters.
 
wturber said:
My system wasn't noisy, didn't stutter, and only skipped in two middle to low gears - which was the "imperfection" that I was dealing with. And that skipping had always gone away with one click up or down. After that, no noise, stutter or skip.
[...]
That begs the question of how things could run quietly given the spacing differences.

The key component that made index shifting practical was the "wobble pulley", which is to say a jockey pulley with a well-defined amount of free side play. So the pulley can float within its side limits to center over the sprocket, but when you shift, it runs out of free play and pushes the chain to the next gear.

One of the factors that distinguishes between 7, 8, 9, 10, 11 speed derailleurs is the specific amount of float in the jockey pulley. Evidently yours has enough to reconcile the spacing difference between 7sp and 9sp across a number of gears (but not all of them).
 
I ended up getting a bike to convert with 7 speed rear freewheel no problem
 
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