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Old 04-06-06, 04:48 AM   #1
motorhommmer
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Help - Sirrus singulator hub conversion

Anyone out there any help on this. In outline looking at putting a nexus 8 ideally 32 hole hub on the back of my sirrus and using a singulator to take up chain tension. Fed up of changing chain and derailleur, as i commute about 5k miles a year.

Anyone any comments on this. Would it work, reliable, approx cost etc.

thanks in advance.
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Old 04-06-06, 05:56 AM   #2
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Why are you fed up with changing the chain? Why do you think that going to an internally geared hub is going to keep you from having to change a chain in the future? How about the derailleur, why is it needing changed?

If you have a Sirrus with an 8 speed drivetrain then with proper maint you should be able to get 5k Km out of the chain easy and I think with proper care that isn't out of the question for a 9 speed either...now with the internally geared hub you could use a bit wider chain for more durability.

But that said...you want to go this route and that is you choice...how about a new frame? You could go with the singulator but I wonder if it would last under conditions that are eating chains and derailleurs. By going to a frame with horizontal dropouts you could eliminate the need for the singulator. You could probably drop in a Surly Crosscheck pretty easy.
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Old 04-06-06, 08:12 AM   #3
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Without looking it up, I seem to remember the Nexus hub being spaced something like 127mm. That could be an issue depending on how you feel about coldsetting alluminum stays. I think it is also 36 hole only.
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Old 04-06-06, 10:50 AM   #4
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I'm no mechanic but the shimano website says the nexus 8 speed is 132 over locknut. Seems like I heard that it means it will fit between 130 0r 135 dropout. Maybe Rev Chuck can verify. According to website all 8 speeds are 36 hole. Do you plan on keeping your front derailleur? If you plan on using just one chainring pay attention to chainline, needs to be pretty straight. Might be easier to sell the sirus and buy a bike with a gearhub already in it. There should be a lot of them on your side of the pond. Unlike here in the US where they are somewhat scarce. Best frame for a gearhub is one with horizonal dropouts or an essentric bottom bracket if using vertical drops.
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Old 04-06-06, 10:51 AM   #5
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I just fitted an SRAM S7 on my geared (vertical dropout) On-one Inbred and though I bought a chain tensioner I've been lucky with the chainring/sprocket combination and I don't even need to use it. From my trawling around on the internet it certainly seemed that the S7 is both functionally better than the shimano hubs and just a bit more durable/reliable. The standard S7 is 130mm, the hub with brake is 135mm. So far so good with the S7 - even did a bit of touring round the Yorkshire Dales last week and it worked absolutely faultlessly.

It was pretty expensive to retrofit the hub though. If its the shimano hub you really want why not invest in a Carrera Subway 8 or a Ridgeback Neutron or Nemesis? Or get yourself a lovely On-one Inbred frame with sliding dropouts and build a new bike?
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Old 04-06-06, 01:28 PM   #6
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I looked at the Carrera Subway 8 at lunch time in Halfords. Did a fair bit of seacrching on internet with regard to the Nexus Hub, not sure that it will take the abuse I give it, 120 miles a week, hail rain, snow and left outside the back door, locked of course
Thanks for info.
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Old 04-06-06, 02:01 PM   #7
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The Nexus 8 will use a 36 hole hub. You can use mild double-butted spokes to save weight. 700C size is available pre-built and ready-to-go.

It has such a variety of gear options that you should have no trouble with vertical drop-outs--just add or subtract a gear tooth.

KMC also makes a 3/32 compatible half link for vertical drops. You can find the half link plus a new chain (like a z71 or a SRAM 57, 67), plus the required NEXUS vertical drop washers at any QBP vender such as Harris Cyclery or Airbomb

Harris has on-line gear calculators and some charts that show gear equivilency of the Nexus 8. Figure out your minimum and maximum gearing requirements and adjust accordingly (perhaps need to change a front chainring or purchase an additional $4 Nexus gear). This is all made very easy. Compare the internal gear calculator with the exact same settings on the derailer calculator and you've got it.
*Ignore fictional speed results like 25 mph unless you've rid yourself of the slow hybrid tires and use something like Panaracer T-Serv (weather) or Pasela Tourguard (dry) in a size like 700Cx28mm. These two, I recommend because they're fast, cushy and have traction. You can get the Pasela TG bigger, but keep the T-serv small because it is sticky.
*Work out your desired low gear first and just let the top end fall where it may. 300% is enough range to do both jobs.


Nexus 8 premium version has double-bearings for longer life and extra speed.
Available pre-built to 700c at Harris Cyclery. QBP catalog also lists a pre-built if you prefer a different rim.

All internal gear hubs go slow for the first 300 miles (maybe not that much) until the very tight bearings get some wear, and then you're good to go.

SRAM S7 is an identical option, but is far lower geared, --useful if you live in the mountains or San Francisco. While the insides are slightly more durable in hilly areas, the $40 outboard shifter is an annoyance when you crunch it.

Use an SRAM or Campy chain if you intend to put more than 1000 miles per chain.
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Old 04-06-06, 02:04 PM   #8
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Quote:
Originally Posted by Grasschopper
Why are you fed up with changing the chain? Why do you think that going to an internally geared hub is going to keep you from having to change a chain in the future? How about the derailleur, why is it needing changed?

If you have a Sirrus with an 8 speed drivetrain then with proper maint you should be able to get 5k Km out of the chain easy and I think with proper care that isn't out of the question for a 9 speed either...now with the internally geared hub you could use a bit wider chain for more durability.

But that said...you want to go this route and that is you choice...how about a new frame? You could go with the singulator but I wonder if it would last under conditions that are eating chains and derailleurs. By going to a frame with horizontal dropouts you could eliminate the need for the singulator. You could probably drop in a Surly Crosscheck pretty easy.
9 speed, 4 chains per year, 5k miles commute. Reasonably good at minding drive train, but welcome to wet Ireland. Only getting 1200 miles per chain. Not sure I believe that the Nexus hub can take the wear and tear.
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Old 04-06-06, 02:05 PM   #9
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The Nexus 8 will use a 36 hole hub. You can use mild double-butted spokes to save weight. 700C size is available pre-built and ready-to-go.

It has such a variety of gear options that you should have no trouble with vertical drop-outs--just add or subtract a gear tooth.

KMC also makes a 3/32 compatible half link for vertical drops. You can find the half link plus a new chain (like a z71 or a SRAM 57, 67), plus the required NEXUS vertical drop washers at any QBP vender such as Harris Cyclery or Airbomb

Harris has on-line gear calculators and some charts that show gear equivilency of the Nexus 8. Figure out your minimum and maximum gearing requirements and adjust accordingly (perhaps need to change a front chainring or purchase an additional $4 Nexus gear). This is all made very easy. Compare the internal gear calculator with the exact same settings on the derailer calculator and you've got it.
*Ignore fictional speed results like 25 mph unless you've rid yourself of the slow hybrid tires and use something like Panaracer T-Serv (weather) or Pasela Tourguard (dry) in a size like 700Cx28mm. These two, I recommend because they're fast, cushy and have traction. You can get the Pasela TG bigger, but keep the T-serv small because it is sticky.
*Work out your desired low gear first and just let the top end fall where it may. 300% is enough range to do both jobs.


Nexus 8 premium version has double-bearings for longer life and extra speed.
Available pre-built to 700c at Harris Cyclery. QBP catalog also lists a pre-built if you prefer a different rim.

All internal gear hubs go slow for the first 300 miles (maybe not that much) until the very tight bearings get some wear, and then you're good to go.

SRAM S7 is an identical option, but is far lower geared, --useful if you live in the mountains or San Francisco. While the insides are slightly more durable in hilly areas, the $40 outboard shifter is an annoyance when you crunch it.

Use an SRAM or Campy chain if you intend to put more than 1000 miles per chain.
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Old 04-06-06, 02:09 PM   #10
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you should have no trouble with vertical drop-outs--just add or subtract a gear tooth.

KMC also makes a 3/32 compatible half link for vertical drops. You can find the half link plus a new chain (like a z71 or a SRAM 57, 67), plus the required NEXUS vertical drop washers at any QBP vender such as Harris Cyclery or Airbomb

Don't understand this bit.
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Old 04-06-06, 02:25 PM   #11
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Quote:
Originally Posted by danielhaden
SRAM S7 is an identical option, but is far lower geared, --useful if you live in the mountains or San Francisco. While the insides are slightly more durable in hilly areas, the $40 outboard shifter is an annoyance when you crunch it.
The SRAM S7 and the Shimano hub have roughly the same range (303% for the SRAM, 307% for the nexus 8) so the S7 certainly isn't "far lower geared"! Obviously the gears you get depend on the chainring/sprocket combination.
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Old 04-06-06, 04:19 PM   #12
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Quote:
Originally Posted by motorhommmer
you should have no trouble with vertical drop-outs--just add or subtract a gear tooth.

KMC also makes a 3/32 compatible half link for vertical drops. You can find the half link plus a new chain (like a z71 or a SRAM 57, 67), plus the required NEXUS vertical drop washers at any QBP vender such as Harris Cyclery or Airbomb

Don't understand this bit.
He is saying to use chain lenght to adjust chain tension. If you can't get it just right by cutting off full links try using a half link. Adjust lenght so the chain is tight just as it bottoms out in the vertical dropouts. Chain used on gearhubs is beefier than 9 speed chain. Combined with a constant straight chainline it should last much longer. A chainguard and fenders would certainly help keep the rain and spray off the chain thus extending life. Either scram or shimano hubs would make a good choice. If you use the shimano get the premium version. It has ultagra quaility berrings and is more duable. It has a red stripe painted around it. The others do not.
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Old 04-10-06, 12:41 AM   #13
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Bravo! Hip! Hip! Hooray!


Chain tension? There is no tension. That's one of the three ways that the gear hubs defeat derailers in races. The chain goes only tight enough that you can't pull it off (tight enough not to skip when you stand on the pedals, but not clothesline tight).
I forgot to mention that. Sorry.
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Old 04-10-06, 12:45 AM   #14
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Quote:
Originally Posted by amaferanga
The SRAM S7 and the Shimano hub have roughly the same range (303% for the SRAM, 307% for the nexus 8) so the S7 certainly isn't "far lower geared"! Obviously the gears you get depend on the chainring/sprocket combination.
All true. However, the sprocket that ships with the S7 causes it to be far lower geared. These sprockets are very inexpensive and very easy to change. As shipped, the S7 is suitable for mountain bikes and hills; however the free sprocket that ships with the Nexus 8 provides an instantly-usable mainstream gear range.
Sure, it is only about a $3 sprocket. That little sprocket is entirely responsible for this difference.
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Old 04-10-06, 11:22 PM   #15
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Quote:
Originally Posted by motorhommmer
...and using a singulator to take up chain tension...
I use one on my mountain bike, and I very rarely throw a chain. Although it's kinda like kissing your sister, there's still some whacky gizmo keeping the chain tight. Nevertheless, it works.
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Old 04-11-06, 03:57 AM   #16
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Quote:
Originally Posted by danielhaden
Bravo! Hip! Hip! Hooray!


Chain tension? There is no tension. That's one of the three ways that the gear hubs defeat derailers in races. The chain goes only tight enough that you can't pull it off (tight enough not to skip when you stand on the pedals, but not clothesline tight).
I forgot to mention that. Sorry.
So, if I go this route and match chain length with gears, I do not need a derailleur or a singulator. This sounds very obvious to some but just double checking.
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Old 04-11-06, 02:00 PM   #17
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So, if I go this route and match chain length with gears, I do not need a derailleur or a singulator. This sounds very obvious to some but just double checking.
None needed if you can find the magic chain length. Good luck.
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