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PostPosted: Mon Jun 17, 2013 4:06 pm 
Dirt Disciple

Joined: Thu May 16, 2013 9:42 am
Posts: 38
I have some 5 hole and different teeth chainrings. One of them (Sugino) is in the picture below. Distance between holes (as on the picture) is the same (between 43,2 - 43,4mm - can not measure better) on each of the rings, so I want to build a single speed crankset, where I can switch chainring.
I would like to know, what cranks should I look for? I prefer Shimano, since there are many arround. I think diameter of holes is arround 8,3mm, can check it up if needed.


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PostPosted: Mon Jun 17, 2013 4:18 pm 
Old School Grand Master

Joined: Tue Oct 09, 2007 1:55 pm
Posts: 8212
Location: New Forest, UK
That looks like a 74mm pcd ring, the inner of a 110/74 set.

You'll need something before 1993. However, as it fits in the inner you will need to chop off the mounting lugs for the outer two rings.

It's a VERY small chainring for anything other than trials. Chain tension will be high and you'll get through chainrings and sprockets fairly fast. Most people go for a ring in the 32-36T range, which also puts them on the shared outer lugs of the crank.

Trials bikes typically run 20-24T rings to gain ground clearance.


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PostPosted: Mon Jun 17, 2013 7:26 pm 
Gold Trader / MacRetro rider
Gold Trader / MacRetro rider

Joined: Thu May 06, 2010 10:05 pm
Posts: 5650
Location: Aberdeen
I use a Shimano 400LX chainset, nice and retro, and also cheap to buy.
On the road I run a single 46T SR Sakae chainring (in the place of the outer ring) held on by singlespeed chainrings, although I have previously used regular double-chainrings and fitted some washers to fill them out.
Off-road I use a couple of old Shimano Biopace rings (38T, 28T) and a 300LX rear mech just to tension the chain, it mean I can manually change to the smaller/bigger chainring when I want (best done at a standstill though if you value your fingetips!!).

The chainring in your pic looks like a 28T inner chainring (Granny ring), it will be ok for going uphill, but not much else....
What size sprocket do you intend to run on the rear?
I run an 18T rear sprocket, so with the 38T up front it's just over the 2:1 ratio that is suggested as a good starting point for off-road singlespeeding.


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PostPosted: Tue Jun 18, 2013 8:12 am 
Dirt Disciple

Joined: Thu May 16, 2013 9:42 am
Posts: 38
Great info Jimo. Will look for an old LX or something like that. I am just experimenting at this moment and trying to find best ratio for me. On the MTB I mostly use ratios between 0,8 - 2,5. I live in the place where anywhere I go, I have to face uphill. So uphill ratio suits me.


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PostPosted: Tue Jun 18, 2013 1:20 pm 
Devout Dirtbag

Joined: Tue Apr 09, 2013 5:38 pm
Posts: 116
Location: Nottingham
Hi,
I run a 34 front ring mounted in the middle and a Shimano 15 tooth rear.
Great offroad, a bit spinny on road but it gives you plenty of flexibility.
Excellent gearing for tracks and trails.
Also good for just running around to the shops etc...
Make sure you use a 1/8th single speed chain and get the chain alignment spot on.
If the alignment is out, or the chain tension is less than perfect the chain will skip and jump, especially with a 15tooth on the back....not good.
Not all chain tensioners work that well....choose wisely.
jr


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PostPosted: Tue Jun 18, 2013 7:56 pm 
Gold Trader / MacRetro rider
Gold Trader / MacRetro rider

Joined: Thu May 06, 2010 10:05 pm
Posts: 5650
Location: Aberdeen
Just to add, I use a regular 3/32 chain on my singlespeed with no issues, the rear sprocket is a Shimano DX.

Normally I use no chain tensioner, instead I have filed a few mm out of the dropouts to allow a bit of front/rear adjustability of the rear wheel, which seems to work well (not always possible though depending on your frame), just ensure your rear wheel is secured properly,I use Halo hex key skewers.
For a cheap chain tensioner just use an old rear mech, adjust the High/Low stop screws to suit the position of the rear sprocket.
I also use the Velosolo cassette spacer kit, which allows you to fine-tune the chainline at the rear, better than some other kits which simply place the rear sprocket in the middle of the "cassette".


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PostPosted: Sun Jun 23, 2013 6:15 pm 
retrobike rider
retrobike rider
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Joined: Sat Nov 06, 2010 11:40 am
Posts: 1691
Location: Exeter
rbike wrote:
Great info Jimo. Will look for an old LX or something like that. I am just experimenting at this moment and trying to find best ratio for me. On the MTB I mostly use ratios between 0,8 - 2,5. I live in the place where anywhere I go, I have to face uphill. So uphill ratio suits me.


So when you get to the top of these hills, are you just gonna freewheel down the other side?


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PostPosted: Sun Jun 23, 2013 7:35 pm 
Gold Trader / MacRetro rider
Gold Trader / MacRetro rider

Joined: Thu May 06, 2010 10:05 pm
Posts: 5650
Location: Aberdeen
hydorah wrote:
rbike wrote:
Great info Jimo. Will look for an old LX or something like that. I am just experimenting at this moment and trying to find best ratio for me. On the MTB I mostly use ratios between 0,8 - 2,5. I live in the place where anywhere I go, I have to face uphill. So uphill ratio suits me.


So when you get to the top of these hills, are you just gonna freewheel down the other side?



No, I think he's going fixed gear, so at least he can pedal down the hills as well.... at 350rpm... :lol:


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PostPosted: Sun Jun 23, 2013 7:38 pm 
retrobike rider
retrobike rider
User avatar

Joined: Sat Nov 06, 2010 11:40 am
Posts: 1691
Location: Exeter
jimo746 wrote:
hydorah wrote:
rbike wrote:
Great info Jimo. Will look for an old LX or something like that. I am just experimenting at this moment and trying to find best ratio for me. On the MTB I mostly use ratios between 0,8 - 2,5. I live in the place where anywhere I go, I have to face uphill. So uphill ratio suits me.


So when you get to the top of these hills, are you just gonna freewheel down the other side?



No, I think he's going fixed gear, so at least he can pedal down the hills as well.... at 350rpm... :lol:


haha more like 3500rpm:-)


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PostPosted: Mon Jun 24, 2013 9:34 pm 
Dirt Disciple

Joined: Thu May 16, 2013 9:42 am
Posts: 38
I confess - down the hill the only thing that I do - I whistle. ;-) So 0rpm.


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