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converting 3x9 to a single speed


Grunder
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Hi

 

While keeping busy during the lockdown I am browsing bike sites.

 

Found Rook Cycles  :D

https://rookcycles.com/

 

My wife fell in love with the colors and what not.

 

 

So...I am planning on converting her bike to a single speed.

 

Now, I have ZERO experience in building and speccing bikes.

Thus assistance will go a looong way in assisting me with the project.

 

Info on her current bike.

She has an Avalanche Prima Donna (year unknown).  As I was upgrading my bike she got my old parts to upgrade her bike also.(the Prima Dona is a VERY basic bike!!)  So far I have upgraded her gearset (my old 3x9 from my big nine 500) and she has a upgraded fork and hydraulic disk brakes.  With the gearset change I also had to replace her rear hub as her old hub was not compatible.  It's a Shimano 36 spoke hub.

 

Ok so the idea is simple.  I want to put a freewheel cog on the rear. and the front setup needs to change to a single chainring.  

 

1st question.  Can The cassette just be taken off and the freewheel be added? Or will I need to replace the rear hub also?

 

2nd question.  The front (3 chainrings); I see people are mentioning that mtb cogs have 4 bolts and standard cogs have 5 bolts.  Does that mean that I will have to replace the entire crank system for the conversion?  OR, can 2 of the chainrings be removed to only leave the big one? (this might be a dumb question shedding further light on my ignorance on bike upgrading)    **Note to self, I am too reliant on bike shops**

 

3rd. question (if I need to replace the crank).  Will I need to replace the bottom bracket as well or will the new cogs work on the current one (assuming its a square bb)?

https://rookcycles.com/collections/parts-and-components/products/crank-set-chain-ring

 

I can't find decent specc info on the Prima Donna to know the ins and outs.  What I can tell you is that the complete groupset came off my Merida big nine 500 (2014) if that helps.

 

 

I think that's about it.    Fire away!  ;)

Edited by Grunder
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Hi

 

While keeping busy during the lockdown I am browsing bike sites.

 

Found Rook Cycles  :D

https://rookcycles.com/

 

My wife fell in love with the colors and what not.

 

 

So...I am planning on converting her bike to a single speed.

 

Now, I have ZERO experience in building and speccing bikes.

Thus assistance will go a looong way in assisting me with the project.

 

Info on her current bike.

She has an Avalanche Prima Donna (year unknown).  As I was upgrading my bike she got my old parts to upgrade her bike also.(the Prima Dona is a VERY basic bike!!)  So far I have upgraded her gearset (my old 3x9 from my big nine 500) and she has a upgraded fork and hydraulic disk brakes.  With the gearset change I also had to replace her rear hub as her old hub was not compatible.  It's a Shimano 36 spoke hub.

 

Ok so the idea is simple.  I want to put a freewheel cog on the rear. and the front setup needs to change to a single chainring.  

 

1st question.  Can The cassette just be taken off and the freewheel be added? Or will I need to replace the rear hub also?

 

2nd question.  The front (3 chainrings); I see people are mentioning that mtb cogs have 4 bolts and standard cogs have 5 bolts.  Does that mean that I will have to replace the entire crank system for the conversion?  OR, can 2 of the chainrings be removed to only leave the big one? (this might be a dumb question shedding further light on my ignorance on bike upgrading)    **Note to self, I am too reliant on bike shops**

 

3rd. question (if I need to replace the crank).  Will I need to replace the bottom bracket as well or will the new cogs work on the current one?

https://rookcycles.com/collections/parts-and-components/products/crank-set-chain-ring

 

I can't find decent specc info on the Prima Donna to know the ins and outs.  What I can tell you is that the complete groupset came off my Merida big nine 500 (2014) if that helps.

 

 

I think that's about it.    Fire away!  ;)

 

Yes you can. 

 

Try www.rapide.co.za Wayne has some nice Single speed specific goodies. 

you remove the current cassette off the back wheel, and then add some spacers and the wide base cog you bought from wayne. Also add a chain tensioner, as this will keep the chain from jumping off.

 

I'm not 100% sure on what crank you have. you can remove the chainrings, and only have 1 x chainring (i did this with my shimano crank, but using a narrow/wide chainring.)

 

You need to ascertain what kind of terrain you will be riding, to determine what size chainring/cog combination you will need.

 

Hope this helps. There is a specific forum board for singlespeed bikes here on the forum.

Edited by RocknRolla
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What he said but I can add some additional info from my side: 

 

  • Count the number of bolts holding the chain rings in place - either 4 or 5 or even direct mount.
  • Now that you know which it is you can then measure the BCD of the chain ring (This basically only applies to 4 bolt chain rings) - the way you do this is by measuring the distance between two diagonal bolts. Now I can guess with probably a 99% certainty that the 3x has a 104 BCD. If however you have a SRAM crank then it will be direct mount and everything I mentioned in this bullet point does not apply  :whistling:  :D
  • Get your wife a 32T oval: https://www.rapide.co.za/product/rapide-ovl-ring-104bcd/ and remember to get the 4 bolts that go with that as your 3 x bolts will not work: https://www.rapide.co.za/product/rapide-single-chainring-bolt-set-of-4/
  • Then get yourself a SS kit, that will be the least painful, trying to get the correct spacers on the rear hub and then the tensioner is just going to confuse you. In fact, I see you can order everything including the bolts and chain ring on this page: https://www.rapide.co.za/product/rapide-tension-r-single-speed-kit/

Now depending on the amount of climbing you have in Bloem, the wheel size of her bike (26er, 27,5er or 29er) as well as the power she can generate I will go with the following: 

 

32T oval in the front

18T in the rear

 

All the best with the build, SS is the most fun you can have on a bike - you will not go wrong! The next step will be to get a single speed specific frame. You then get rid of the tensioner  :)  

  

 

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Thanks RW

 

Look the riding she will be doing is mostly urban with the kids either following her or with a kid on a bike seat (current setup).

 

Nine out of ten times the bike will not see a 'trail'.  

 

But I will keep the oval chainring in mind when the time comes and she wants to do a bit more adventurous stuff.

 

 you mentioned:

"Now that you know which it is you can then measure the BCD of the chain ring (This basically only applies to 4 bolt chain rings) - the way you do this is by measuring the distance between two diagonal bolts. Now I can guess with probably a 99% certainty that the 3x has a 104 BCD"

 

Educate me why is this needed?

 

The bike is a 650b.

Edited by Grunder
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What Popcorn said. Close ups of the crank and front setup. The rear is a simple issue.

If I were you I would run a 30 front and 17 rear. Make it easier rather than harder to start off with.

 

Ya she also has a kid in a bike seat on. Opt for a lighter gear. 

Look Grunder if you're unsure about what size rear cog to use. 

Replace only the front with a single ring first. A 32 is a good starting point but by no means the only solution. Then let her choose a comfortable single rear gear she can stay in. Especially with the additional weight of a seated child.

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So far the discussion is about the front chainring.  

 

you guys are suggesting 32t or 30t.

 

 

Looking at the Rook Cycles site they are selling 44t and 48t chainrings.

 

Why would they only focus on these big sizes?

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It's only to purchase the correct ring. You don't want to buy a 96 BCD ring and then you end up needing a 104. All it means is that the ring wont fit into the holes: 

 

https://www.wolftoothcomponents.com/pages/how-to-measure-bolt-circle-diameter-bcd

 

Then the only reason I went with an oval 32T is because as Popcorn said: its a good starting point, by placing a peg in the ground you can immediately go into a certain direction. I mean having a kid on the back adds an additional few kilos and if you go too heavy she will struggle. This is info I did not have initially  :)

 

Oval vs round, now that opens a whole new can of worms: https://www.worldwidecyclery.com/blogs/worldwide-cyclery-blog/oval-chainrings-explained-why-you-need-one

 

I have used both before and prefer oval, you will not be able to use one of her current rings the chain will keep dropping. 

 

So with the new info I would like to revise my original suggestion and go with what copper has said. You could even go 32T in the front with a 18 or possibly even a 20 in the rear

 

O and edit: here's a nice link: http://gears.mtbcrosscountry.com/#26I1I1

 

Thanks RW

 

Look the riding she will be doing is mostly urban with the kids either following her or with a kid on a bike seat (current setup).

 

Nine out of ten times the bike will not see a 'trail'.  

 

But I will keep the oval chainring in mind when the time comes and she wants to do a bit more adventurous stuff.

 

 you mentioned:

"Now that you know which it is you can then measure the BCD of the chain ring (This basically only applies to 4 bolt chain rings) - the way you do this is by measuring the distance between two diagonal bolts. Now I can guess with probably a 99% certainty that the 3x has a 104 BCD"

 

Educate me why is this needed?

 

The bike is a 650b.

Edited by RobertWhitehead
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Different frame and or type of bike. 

 

You're looking to make a mtb with a 3x9 config into a ss. The mtb (without the kid and seat) probably weighs in at around 13-15kgs. Everything is heavier on her current steed. The bikes they focus on are fixie type bikes with a rigid fork and road type wheels. That fixie probably weighs in at around 8kgs 

 

So far the discussion is about the front chainring.  

 

you guys are suggesting 32t or 30t.

 

 

Looking at the Rook Cycles site they are selling 44t and 48t chainrings.

 

Why would they only focus on these big sizes?

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you will not be able to use one of her current rings the chain will keep dropping. 

 

 

 

 

Ok cool.

 

Just had a look on Rapide and I see what you mean with the distance.  Thanks for that.

 

 

You mention the chain will keep falling off.  Is that because the derailer is not present anymore? 

 

So I will have to buy a new chainring that can work without a derailer

Edited by Grunder
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Different frame and or type of bike. 

 

You're looking to make a mtb with a 3x9 config into a ss. The mtb (without the kid and seat) probably weighs in at around 13-15kgs. Everything is heavier on her current steed. The bikes they focus on are fixie type bikes with a rigid fork and road type wheels. That fixie probably weighs in at around 8kgs 

Gotcha  :thumbup:

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That is unfortunately correct yes. You will have to purchase a new ring in the front. If you can measure the BCD and decide on the ring you want in the rear then I can possibly help with some parts  :thumbup:

 

 

Ok cool.

 

Just had a look on Rapide and I see what you mean with the distance.  Thanks for that.

 

 

You mention the chain will keep falling off.  Is that because the derailer is not present anymore? 

 

So I will have to buy a new chainring that can work without a derailer

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The reason for dedicated single speed gears is that they don't have pick ups or drop offs. When aligning the chain as well check from the rear that the chain is as straight as you can possibly make it. This make it as quiet as it can be. 

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