Convert 7 Speed to 8 Speed?
- Thread starter JGcycle
- Start date
fauconnier
Active Member
- Region
- Canada
What are you trying to get with one more speed. Changing the motor chainring is probably a better and simpler option.
JGcycle
Well-Known Member
- Region
- Canada
- City
- Saint John
Just trying to get more even spacing of the gears. The stock freewheel jumps from a first gear of 34t to a second gear of 24t. I like the gear spacing of gears 3 to 7. With an 8 speed, I could keep tighter gear spacing throughout the whole range.
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fauconnier
Active Member
- Region
- Canada
With the right tool, it is possible to replace few gears on your cassette to rearrange it to your taste.
JGcycle
Well-Known Member
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- Canada
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- Saint John
Thanks--I never thought of that.
harryS
Well-Known Member
If the Voltbike Bravo used a cassette, you could redo the gears, but the spec says SunRace M2 Freewheel, One thing about going to an 8 speed freewheel is that it's a few mm wider, so you will likely have to pull the frame a bit everytime to re-install the wheel, and that is a pain-in-the-neck.
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Jeremy McCreary
Well-Known Member
- Region
- USA
- City
- Carlsbad, CA
Don't know about your particular situation, but my mechanic successfully converted my 9-speed hub-drive to a 10-speed as part of a major drivetrain overhaul. Cassette, derailleur, chain, and shifter were all upgraded substantially in the process.
That was 1,100 mi ago. Superb performance ever since.
Be careful about changing individual cassette cogs. Within rounding error, a cassette that feels "evenly spaced" has a fixed ratio of teeth between adjacent cogs. On my current 11-42t 10-speed, that ratio is 1.15. Cassettes generally come that way.
Depending on the state of drivetrain wear at the time, you may well have to change the chainring, too. Take that opportunity to dial in your overall gearing to current riding needs. Is your lowest gear low enough for your terrain? Is your highest gear too high or low? Get those sorted, then let the fixed-ratio cassette spacing noted above set the cogs in between.
I did that, and what a difference! Lots of online gear calculators out there to help you arrive at the right cassette+chainring combo, but I prefer my own spreadsheet.
That was 1,100 mi ago. Superb performance ever since.
Be careful about changing individual cassette cogs. Within rounding error, a cassette that feels "evenly spaced" has a fixed ratio of teeth between adjacent cogs. On my current 11-42t 10-speed, that ratio is 1.15. Cassettes generally come that way.
Depending on the state of drivetrain wear at the time, you may well have to change the chainring, too. Take that opportunity to dial in your overall gearing to current riding needs. Is your lowest gear low enough for your terrain? Is your highest gear too high or low? Get those sorted, then let the fixed-ratio cassette spacing noted above set the cogs in between.
I did that, and what a difference! Lots of online gear calculators out there to help you arrive at the right cassette+chainring combo, but I prefer my own spreadsheet.
fooferdoggie
Well-Known Member
no because you have the wrong hub. a freewheel. 8 speed and up and usually free hubs. Plus you would have to have a new detailer too.
IF you have a HG hub you can even go beyond 8 speed to achieve an even tighter spacing between cogs. But keep in mind, a new cassette (9,10,11 speed, for instance) will, for the most part, require a matching chain and a narrower chainring.
I converted my drivetrain to a 12-speed, 10-45, and love the tightly spaced jumps between cogs.
I converted my drivetrain to a 12-speed, 10-45, and love the tightly spaced jumps between cogs.
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The OP is not having shifting issues…
Possibly
Shimano RD-410 derailleur is 7 or 8 speed compatible so you would need a 8 speed shifter and a 8 speed freewheel, as you noted.
But axle length may not allow for clearance between the highest gear/smallest cog and the right side dropout. You might be able to tell by eyeballing your current setup to see if it appears there would be enough clearance for the additional cog of a 8 speed freewheel, and chain (outboard of your current 7 speed freewheel to the frame dropout).
JGcycle
Well-Known Member
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- Canada
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- Saint John
Not the issue I'm having, but a great instructional video--thanks so much for this.
JGcycle
Well-Known Member
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- Canada
- City
- Saint John
Thanks for this great info. Now I know what to look for.
indianajo
Well-Known Member
It is possible to fit 8 speeds on a freehub without pulling the frame fork spacing more than 135 mm. It is not possible with a freewheel. It is not possible with a hub motor in there too. It is easier to buy a wheel with a free hub and an 8 speed sprocket cluster, but I don't know anybody that sells them that way but bike shops. The parts houses have all the components, but not assembled. Because I hated the 7 sprocket set speed so much, I moved to a front hub motor, with a free hub 8 speed rear wheel and no motor back there. 7 lb in front balances the bike better rolling it out of the garage & over the step, too.
Spreading the fork can work on a steel bike, but aluminum frame tends to fracture if bent.
Going to 9 or more speeds decreases the chain width and chain life. Also the thinner chain might not be compatible with your front sprocket. 6, 7,8 speeds all use the same width chain. I find my original 8 speed sprocket about perfect, and the replacement 11-34 from SRAM had the same tooth counts as my old one. I pedal unpowered a lot, and get about 5000 miles or 2 1/2 years out of my KMC or Sun chain.
Spreading the fork can work on a steel bike, but aluminum frame tends to fracture if bent.
Going to 9 or more speeds decreases the chain width and chain life. Also the thinner chain might not be compatible with your front sprocket. 6, 7,8 speeds all use the same width chain. I find my original 8 speed sprocket about perfect, and the replacement 11-34 from SRAM had the same tooth counts as my old one. I pedal unpowered a lot, and get about 5000 miles or 2 1/2 years out of my KMC or Sun chain.
JGcycle
Well-Known Member
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- Canada
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- Saint John
I checked the clearance--definitely not enough--guess I'll stick with a 7 speed freewheel.
Slaphappygamer
Well-Known Member
- Region
- USA
- City
- Aptos
Oh interesting. I reread the post stating “The stock freewheel jumps from a first gear of 34t to a second gear of 24t.”, I was thinking that the chain would be jumping from one gear to another, but it’s the freewheel that is jumping. I never knew it could do that. That’s why I recommended the video.The OP is not having shifting issues…
The OP was complaining about the huge jump in size between the 34t & 24t cogs.Oh interesting. I reread the post stating “The stock freewheel jumps from a first gear of 34t to a second gear of 24t.”, I was thinking that the chain would be jumping from one gear to another, but it’s the freewheel that is jumping. I never knew it could do that. That’s why I recommended the video.
Stefan Mikes
Gravel e-biker
- Region
- Europe
- City
- Mazovia, PL
Typically, the largest rear cogset* sprocket is called a "granny gear", which is usually applied for very steep climbs only. The OP would be well off if he just didn't use the 1st gear for normal rides, or accept the big gearing jump between the 1st and 2nd gear.
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*) Freewheel and freehub are two completely different technologies; one cannot be replaced with the other for a given bike frame. Technically speaking, the collection of sprockets for the freewheel is called a 'cogset'. The 'casette' if for the freehub. The freewheel cogset and the freehub casette are built totally differently and are not compatible.
Just my two cents.
JGcycle
Well-Known Member
- Region
- Canada
- City
- Saint John
That is pretty much the way I use it, and its not so bad, just being a bit OCD about the gear spacing LOL.
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