Chainring rubbing chainstay
06-01-16 | 03:31 PM
#1
Thread Starter
Newbie
Joined: Jun 2016
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Chainring rubbing chainstay
Hey folks,
New to the forum and I'm trying to build up my first SS so cut me some slack. I had an old mtn bike, 2006 Giant Iguana that I am converting to a SS. I purchased a 46t Origin8 P/P crankset and a 107mm Shimano UN55 bb. I went to put the bike together and the chainring is rubbing on the chainstay. I know I have the bb installed in the right direction and its not just touching, full contact. The bb I took off was a 113mm, did I go downsize to far in spindle length? I don't think going to a 44t or a 42t chainring is going to solve my problem. The largest chainring was a 42t originally.
Any help is appreciated.
New to the forum and I'm trying to build up my first SS so cut me some slack. I had an old mtn bike, 2006 Giant Iguana that I am converting to a SS. I purchased a 46t Origin8 P/P crankset and a 107mm Shimano UN55 bb. I went to put the bike together and the chainring is rubbing on the chainstay. I know I have the bb installed in the right direction and its not just touching, full contact. The bb I took off was a 113mm, did I go downsize to far in spindle length? I don't think going to a 44t or a 42t chainring is going to solve my problem. The largest chainring was a 42t originally.
Any help is appreciated.
06-01-16 | 03:51 PM
#3
Calamari Marionette Ph.D
Joined: Dec 2013
Posts: 7,861
Likes: 41
From: Coeur d' Alene
Bikes: 3 Chinese Gas Pipe Nerdcycles and 2 Chicago Electroforged Boat Anchors
Hey folks,
New to the forum and I'm trying to build up my first SS so cut me some slack. I had an old mtn bike, 2006 Giant Iguana that I am converting to a SS. I purchased a 46t Origin8 P/P crankset and a 107mm Shimano UN55 bb. I went to put the bike together and the chainring is rubbing on the chainstay. I know I have the bb installed in the right direction and its not just touching, full contact. The bb I took off was a 113mm, did I go downsize to far in spindle length? I don't think going to a 44t or a 42t chainring is going to solve my problem. The largest chainring was a 42t originally.
Any help is appreciated.
New to the forum and I'm trying to build up my first SS so cut me some slack. I had an old mtn bike, 2006 Giant Iguana that I am converting to a SS. I purchased a 46t Origin8 P/P crankset and a 107mm Shimano UN55 bb. I went to put the bike together and the chainring is rubbing on the chainstay. I know I have the bb installed in the right direction and its not just touching, full contact. The bb I took off was a 113mm, did I go downsize to far in spindle length? I don't think going to a 44t or a 42t chainring is going to solve my problem. The largest chainring was a 42t originally.
Any help is appreciated.
06-01-16 | 04:47 PM
#6
Calamari Marionette Ph.D
Joined: Dec 2013
Posts: 7,861
Likes: 41
From: Coeur d' Alene
Bikes: 3 Chinese Gas Pipe Nerdcycles and 2 Chicago Electroforged Boat Anchors
2. Do NOT use a Shimano UN55 110mm BB. They are asymmetrical and the spindle is a good 3-4mms farther out on the non drive side than they are on the drive side which would make your problem worse, not better. All UN55s are off by varying amounts but the 110 is off the most. I know this because I needed an asymmetrical BB for an oddball frame/build. Someone once posted a chart listing every UN55 length and the amount by which it was off center, but I can't find it.
06-01-16 | 05:49 PM
#7
Agree with [MENTION=362748]SquidPuppet[/MENTION]. Measure your front chainline from the center of the seat tube first and adjust chainring/freewheel ratio to eliminate rubbing. Orrr... Just dimple the chainstay! Iguanas are steel frames, no? Not a big deal to put a small dimple on a steel chainstay. I've done it a few times.
06-01-16 | 07:35 PM
#8
mechanically sound
Joined: Jan 2007
Posts: 1,610
Likes: 87
From: Dover, NH
Bikes: Indy Fab steel deluxe, Aventon cordoba, S-works stumpy fsr, Masi vincere, Dahon mu uno, Outcast 29 commuter
Combination of BB spacers and/or chainring spacers just might do it.
__________________
06-01-16 | 09:10 PM
#9
Senior Member
Joined: May 2013
Posts: 1,682
Likes: 10
From: dEnVeR
Bikes: CENTURION / LOOK / Bianchi
First i've heard of this! I hope you find that chart, i'm curious..
1. What is your front chainline measurement currently?
2. Do NOT use a Shimano UN55 110mm BB. They are asymmetrical and the spindle is a good 3-4mms farther out on the non drive side than they are on the drive side which would make your problem worse, not better. All UN55s are off by varying amounts but the 110 is off the most. I know this because I needed an asymmetrical BB for an oddball frame/build. Someone once posted a chart listing every UN55 length and the amount by which it was off center, but I can't find it.
2. Do NOT use a Shimano UN55 110mm BB. They are asymmetrical and the spindle is a good 3-4mms farther out on the non drive side than they are on the drive side which would make your problem worse, not better. All UN55s are off by varying amounts but the 110 is off the most. I know this because I needed an asymmetrical BB for an oddball frame/build. Someone once posted a chart listing every UN55 length and the amount by which it was off center, but I can't find it.
06-02-16 | 08:53 AM
#10
Calamari Marionette Ph.D
Joined: Dec 2013
Posts: 7,861
Likes: 41
From: Coeur d' Alene
Bikes: 3 Chinese Gas Pipe Nerdcycles and 2 Chicago Electroforged Boat Anchors
I just did a search here, in a bunch of forums and threads. Then I spent way too long googling. Can't find the chart. I can find lots of threads with people who have had the "problem" and are also curious why Shimano does this. But no answers or charts. Ugh!
This is a common post on the subject.
This is a common post on the subject.
I was recently trying to install a crankset, on a single speed bike, that uses a square taper bottom bracket. I was using a Shimano UN-55 BB with 107mm spindle length. As it turned out that spindle length was a bit too short (chainline was off and crank arms were too close to chainstays). So, I decided to try a Shimano UN-55 with 110mm spindle length.
I haven't had a chance to actually install the 110mm BB, however something does look odd to me. I noticed the drive side spindle on the UN-55 is the same length for both the 110 and the 107, while only the non-drive side is longer on the 110. Correct me if I'm wrong but that is still going to leave me with the same issue I was having, only now the non-drive crank arm will be further out.
Am I missing something here?
I haven't had a chance to actually install the 110mm BB, however something does look odd to me. I noticed the drive side spindle on the UN-55 is the same length for both the 110 and the 107, while only the non-drive side is longer on the 110. Correct me if I'm wrong but that is still going to leave me with the same issue I was having, only now the non-drive crank arm will be further out.
Am I missing something here?
06-02-16 | 09:11 AM
#11
Senior Member
Joined: Jun 2013
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From: Bozeman
Bikes: 199? Landshark Roadshark, 198? Mondonico Diamond, 1987 Panasonic DX-5000, 1987 Bianchi Limited, Univega... Chrome..., 1989 Schwinn Woodlands, Motobecane USA Record, Raleigh Tokul 2
Use a longer BB, use spacers, or get a smaller ring.
One of the three will be your answer.
One of the three will be your answer.
06-02-16 | 09:46 AM
#12
Senior Member
Joined: Aug 2011
Posts: 22,676
Likes: 2,643
From: CID
Bikes: 1991 Bianchi Eros, 1964 Armstrong, 1988 Diamondback Ascent, 1988 Bianchi Premio, 1987 Bianchi Sport SX, 1980s Raleigh mixte (hers), All-City Space Horse (hers)
My FG conversion is an old MTB, too, so I ran into similar constraints. It was originally designed to have a 48-38-28 crankset, and 45T is about the biggest chainring I can use without scraping. If you have to use a 42T to make things work out, it won't be the end of the world.
BTW, here's the link to the Sheldon Brown blog post about UN54 bottom brackets: Shimano UN54 Cartridge Bottom Brackets Relative Chainline ? Harris Cyclery Blog
I was bored one afternoon and did the rest of the math to figure out the NDS lengths and by how far some of them were asymmetrical (I figure a difference of 1mm or less is close enough to call symmetrical
):
BTW, here's the link to the Sheldon Brown blog post about UN54 bottom brackets: Shimano UN54 Cartridge Bottom Brackets Relative Chainline ? Harris Cyclery Blog
I was bored one afternoon and did the rest of the math to figure out the NDS lengths and by how far some of them were asymmetrical (I figure a difference of 1mm or less is close enough to call symmetrical
):Code:
Bottom Bracket/Spec Actual NDS DS Symmetrical? Sugino/Tange 68-103 103mm 17mm 18mm Y (+1mm on DS) Shimano UN54 68-107 108 20 20 Y Shimano UN54 68-110 111.5 23.5 20 N (+3.5mm on NDS) Shimano UN54 68-113 114 23.5 22.5 Y (+1mm on NDS) Shimano UN54 68-115 115.5 24 23.5 Y (+0.5mm on NDS) Shimano UN54 68-118 118.5 25.5 25 Y (+0.5mm on NDS) Shimano UN54 68-122 123 27 28 Y (+1mm on DS) Shimano UN54 68-127 128 30 30 Y
