wheel and gear problems in Cambodia

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beaker   1 µW

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wheel and gear problems in Cambodia

Post by beaker » Aug 18 2018 5:57am

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?

andy1956   10 mW

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Re: wheel and gear problems in Cambodia

Post by andy1956 » Aug 18 2018 10:17am

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??

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Chalo   100 GW

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Re: wheel and gear problems in Cambodia

Post by Chalo » Aug 18 2018 10:42am

beaker wrote:
Aug 18 2018 5:57am
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.)
This is to express my gratitude to Justin of Grin Technologies for his extraordinary measures to save this forum for the benefit of all.

markz   100 GW

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Re: wheel and gear problems in Cambodia

Post by markz » Aug 18 2018 11:25am

andy1956 wrote:
Aug 18 2018 10:17am
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.

donn   100 W

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Re: wheel and gear problems in Cambodia

Post by donn » Aug 18 2018 12:40pm

I believe this is what chalo's talking about:
sheldon brown wrote: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.

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wturber   100 kW

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Re: wheel and gear problems in Cambodia

Post by wturber » Aug 18 2018 10:05pm

beaker wrote:
Aug 18 2018 5:57am

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.
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viewtopic.php?f=2&t=90369

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Chalo   100 GW

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Re: wheel and gear problems in Cambodia

Post by Chalo » Aug 19 2018 11:51am

wturber wrote:
Aug 18 2018 10:05pm
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.
This is to express my gratitude to Justin of Grin Technologies for his extraordinary measures to save this forum for the benefit of all.

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Re: wheel and gear problems in Cambodia

Post by dogman dan » Aug 20 2018 7:25am

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.

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wturber   100 kW

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Re: wheel and gear problems in Cambodia

Post by wturber » Aug 25 2018 2:42pm

Chalo wrote:
Aug 19 2018 11:51am
wturber wrote:
Aug 18 2018 10:05pm
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.
"Commuter - DC Booster"
Iron Horse 3.0 hardtail - 48V / 1000W / 470rpm generic Chinese DD Hub motor (ebay)
8 x 36v 4.3ah 10s 2P battery packs - 1500W 30A DC Boost Converter delivers 54v and about 1000 watts peak
53T/42T Sakae Road cranks - 30mph+ on flats
viewtopic.php?f=2&t=90369

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Re: wheel and gear problems in Cambodia

Post by 999zip999 » Aug 25 2018 3:16pm

Dnp has a 9speed 11t freewheel . I would use a friction shifters old school.

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wturber   100 kW

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Re: wheel and gear problems in Cambodia

Post by wturber » Aug 25 2018 4:11pm

999zip999 wrote:
Aug 25 2018 3:16pm
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.
"Commuter - DC Booster"
Iron Horse 3.0 hardtail - 48V / 1000W / 470rpm generic Chinese DD Hub motor (ebay)
8 x 36v 4.3ah 10s 2P battery packs - 1500W 30A DC Boost Converter delivers 54v and about 1000 watts peak
53T/42T Sakae Road cranks - 30mph+ on flats
viewtopic.php?f=2&t=90369

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Chalo   100 GW

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Re: wheel and gear problems in Cambodia

Post by Chalo » Aug 25 2018 6:07pm

wturber wrote:
Aug 25 2018 2:42pm
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).
This is to express my gratitude to Justin of Grin Technologies for his extraordinary measures to save this forum for the benefit of all.

beaker   1 µW

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Re: wheel and gear problems in Cambodia

Post by beaker » Sep 05 2018 3:32am

I ended up getting a bike to convert with 7 speed rear freewheel no problem

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