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Replacing 50t chainring on Fuji Touring IVc

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Replacing 50t chainring on Fuji Touring IVc

Old 08-05-21, 09:38 AM
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JVME
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Replacing 50t chainring on Fuji Touring IVc

Hi all. I've tried posting this three times and keep getting booted off.

I would like to replace this 50T chainring with a 44T or 46T. It's a new bike to me, Fuji Touring IV. I think this is a 5arm square taper chain ring? The crank are Sugino (stock?) Can you recommend a new/vintage replacement one? Steel is preferred.

I'll be using a Cyclone FD.

Thanks!
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Old 08-05-21, 10:57 AM
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What model Sugino crank? Is it a triple? That’ll determine the bolt circle diameter (not just one standard, I’m afraid) and what ring to find.
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Old 08-05-21, 11:15 AM
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A Fuji Series IV with a Sugino triple?

it's almost certainly a 110bcd chainring that you're looking for. While I suspect you can find a steel 52t from some lower end cranks of the day, I think all the 46/44 ones you'll find will be aluminum
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Old 08-05-21, 11:23 AM
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Wolf tooth and Surly offer stainless steel chainrings, very expensive.
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Old 08-05-21, 11:24 AM
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Originally Posted by onyerleft View Post
I can't see the pics so I can't give an opinion. Just sayin'.
Unfortunately I canít get the board to let me post images or link to images hosted elsewhere. Iíll try again here.
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Old 08-05-21, 11:25 AM
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Originally Posted by onyerleft View Post
I can't see the pics so I can't give an opinion. Just sayin'.
Unfortunately I canít get the board to let me post images or link to images hosted elsewhere. Iíll try again here.

Last edited by JVME; 08-05-21 at 11:34 AM.
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Old 08-05-21, 11:39 AM
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Why would you want steel? I can see it for a small granny chainring, but aluminum is the way to go for outer chainrings.

You can determine your bolt circle diameter (likely 144mm, 130mm, or 110mm) by measuring the center-to-center distance between two adjacent chainring bolts, and then using Sheldon Brown's conversion equation (see below).

If your crank can take a 40T or smaller ring, that rules out 144mm (minimum 42T or hard-to-find 41T). 36 or smaller rules out 130mm (minimum 38T or hard-to-find 34T).

"Measuring BCD: This 110 mm BCD ring measures 64.7 mm center-to-center
(or, from left side to left side, or right side to right side --easier to measure).

Multiplying this dimension by 1.701 will give you the actual BCD for a 5-bolt chainring. Use 1.155 for 3-bolt chainrings."
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Old 08-05-21, 11:52 AM
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Originally Posted by JVME View Post
Unfortunately I can’t get the board to let me post images or link to images hosted elsewhere. I’ll try again here.
It's to combat spammers. Don't take it personally, just keep hanging out here and chatting about bikes until you have 10+ posts.
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Old 08-05-21, 12:06 PM
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Originally Posted by ThermionicScott View Post
It's to combat spammers. Don't take it personally, just keep hanging out here and chatting about bikes until you have 10+ posts.
Thanks! That makes sense. I will probably too many questions anyway.
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Old 08-05-21, 01:34 PM
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Originally Posted by nlerner View Post
What model Sugino crank? Is it a triple? Thatíll determine the bolt circle diameter (not just one standard, Iím afraid) and what ring to find.
From what I can see on the inside of the crank it says "SUGINO JAPAN 170" There are currently 3 chain rings on here. Biggest is a 50T and smallest is a 28T. I cannot see any writing on the chainrings.

I am trying to fit a Suntour Cyclone FD and the specs I've read say they like a 18T Max capacity. The previous owner had put a Shimano Exage 500 LX RD on it, with what I ASSUME is a matching FD and they had indexing shifters on flat bars.

I got rid of the flats and went back to drops, moved a set of friction shifters to the Downtube braze ons and fit a Cycle GT Long Cage RD. My goal is to use a cyclone FD, so I'd like to be inside the 18T capacity.
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Old 08-05-21, 02:09 PM
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170 is the length of the crank arms.

I think on the sugino ones I've seen the model name is on the outside of the arm. It might say something like Sugino AT or GT or VT? Could have worn off too.

If it is one of those then like others have said it will be a 110BCD chainring you will be looking for.
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Old 08-05-21, 03:23 PM
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Should also say you can only post 5X the first two days. After you hit 10 you can post all you want and add photos
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Old 08-05-21, 08:33 PM
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1983 was the last, if not the only, year for the Touring IV. The crank was a Sugino AT, 110x74 BCD triple, 50/42/28.

If the freewheel is the original 14-15-17-19-21-24, and if you want to keep the 42T middle ring, the only two outer rings that don't give stupid gearing with wonky gaps and a ton of duplicate gears are the 50T the bike was spec'd with, (1.5-step + granny,) and a 45T (half-step + granny.) With a 46T outer, you'd want to drop the middle ring to a 39... very similar gearing, just ~8% lower across the board.

If you haven't got the Cyclone front derailleur in hand, a Cyclone GT would be the one to get. A Suntour Mountech is original spec.

1983 Fuji Catalog

Visual Gear Calculator, so you can play with rings and see what you want.

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