Ticking time bomb?
09-03-18, 02:59 PM
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Malliot Juane
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Ticking time bomb?
Cracks around almost every spoke hole and valve stem.
How much life is left in this rim, i have to source a new one obviously but can i keep riding this? What will the failure mode be? Spoke pull through or catastrophic failure? Would like to upgrade from nexus 7c18 coaster to a 8 speed nexus coaster only thing is the spacing is 127 on the frame, is there an 8 speed hub with 127mm spacing or can an wider hub be respaced?
09-03-18, 03:51 PM
#2
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The ticking stopped and the bomb blew up long ago.
Life left in that rim is counted in negative numbers.
You are already looking at failure mode. It is garbage. Don't ride it.
-Tim-
Life left in that rim is counted in negative numbers.
You are already looking at failure mode. It is garbage. Don't ride it.
-Tim-
Last edited by TimothyH; 09-03-18 at 03:54 PM.
09-03-18, 04:00 PM
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Malliot Juane
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Can i re-space a 132mm old nexus 8 to 127mm?
09-03-18, 05:37 PM
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Put 2.5 mm spacers on each axle end of the 127mm wheel, but not sure if optimal solution
09-03-18, 07:14 PM
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Bwa ha ha, rim is waaay beyond toasted - how has this felt riding it? My old rim just had one spoke through and it wasn't going anywhere (32h wheel!). My sympathies, it's hard to stomach a new rear wheel.
What is your frame material? It might be able to stretch a few millimeters to hold new hub.
What is your frame material? It might be able to stretch a few millimeters to hold new hub.
09-03-18, 07:33 PM
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You could ride it if you wish... for a few minutes.
The failure mode will be spokes pulling through, which will act like broken spokes, and the rim will be pulled out of true, giving brake rub, or chainstay rub, or both.
If you continue to ride with chainstay rub, you could toast the whole frame. I.E. New bike time.
Or, you could have a long walk home lifting the rear wheel so it doesn't destroy the frame.
The wheel can be repaired with rim replacement. Neither trivial nor difficult, but tedious, especially if it is your first.
If you can find an identical replacement rim, or one with the same ERD then you may be able to re-use spokes and nipples. Otherwise, tune up the hub, and relace new spokes, nipples, and rim.
The failure mode will be spokes pulling through, which will act like broken spokes, and the rim will be pulled out of true, giving brake rub, or chainstay rub, or both.
If you continue to ride with chainstay rub, you could toast the whole frame. I.E. New bike time.
Or, you could have a long walk home lifting the rear wheel so it doesn't destroy the frame.
The wheel can be repaired with rim replacement. Neither trivial nor difficult, but tedious, especially if it is your first.
If you can find an identical replacement rim, or one with the same ERD then you may be able to re-use spokes and nipples. Otherwise, tune up the hub, and relace new spokes, nipples, and rim.
09-03-18, 07:40 PM
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Somewhat tangentially, I bet we'll start seeing more of these threads as discs continue to take over. Riders whose rims are cracking to all hell, but since braking no longer depends on the rim, the wobbly wheel wasn't caught right away.
09-03-18, 09:09 PM
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+1 Hub brakes do stress the spokes more. So wheel designs that seemed cool with rim brakes are less so (for as long) as those with disks. That the feed back loop is less likely to be paid attention to jut makes this likelihood all the worse. Andy
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09-04-18, 07:31 AM
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They were wrong.
09-04-18, 07:40 AM
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As others have said, you are already looking at failure mode.
If by “failure mode” you mean what happens when the spoke pulls all the way through.... It will be like breaking a spoke. The wheel will go out of true (if by some miracle it is still IN true), and you may be walking home. Needless to say, I would not ride it far or with any extra load or fast.
If by “failure mode” you mean what happens when the spoke pulls all the way through.... It will be like breaking a spoke. The wheel will go out of true (if by some miracle it is still IN true), and you may be walking home. Needless to say, I would not ride it far or with any extra load or fast.
09-04-18, 07:53 AM
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I would get a copy of "The Bicycle Wheel" by Jobst Brandt, and a spoke wrench, and carefully take that wheel completely apart.
Order a new rim with the same profile. Spokes could be re-used if you don't damage any of the nipples, but if they aren't stainless steel, I would measure the old ones and order a new set of stainless steel spokes in the same size, along quality brass nipples.
Use book to rebuild, use a known good wheel to copy and approximate the correct amount of spoke tension. Use your brake pads to dish the wheel and true it. Total cost, under $50.
Order a new rim with the same profile. Spokes could be re-used if you don't damage any of the nipples, but if they aren't stainless steel, I would measure the old ones and order a new set of stainless steel spokes in the same size, along quality brass nipples.
Use book to rebuild, use a known good wheel to copy and approximate the correct amount of spoke tension. Use your brake pads to dish the wheel and true it. Total cost, under $50.
09-04-18, 08:08 AM
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I don't see the problem. Maybe post a pic from a different angle??
09-04-18, 09:27 AM
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Malliot Juane
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Bwa ha ha, rim is waaay beyond toasted - how has this felt riding it? My old rim just had one spoke through and it wasn't going anywhere (32h wheel!). My sympathies, it's hard to stomach a new rear wheel.
What is your frame material? It might be able to stretch a few millimeters to hold new hub.
What is your frame material? It might be able to stretch a few millimeters to hold new hub.
09-04-18, 10:53 AM
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Frame material is aluminum with 127 spacing so i need to take a 132 Nexus 8 down to 127. Surprising the bike felt fine while riding it, didn't even notice it until i got a flat tire and was fixing it on the side of the rode, with a coaster brake there is no brake rub and at high speeds it felt fine (well the high speeds 40kph that i get to). I do weigh 250 lbs and the bike is around 40lbs and i usually carry 20-30 lbs in an pannier. The bike is only 5 years old and probably has 5000-8000k on it so not high mileage.
The Shimano 8-speed hubs have a overlocknut spacing ranging of 132 to 135 mm, as sold: see Shimano's overlocknut spacing chart. It is possible to reduce the spacing of the Nexus Rollerbrake/freewheeling models to as little as 126 mm by leaving off the Rollerbrake and using a narrower locknut. See our Rollerbrake page for instructions. This is not possible with the coaster-brakeor disc-brake models.
It seems like with the right overlocknut you could get an 8 speed to maybe 130? At 130mm maybe it could fit into your drops, spreading them by 3mm...
Seems odd a bike mfg would make an aluminum frame at 127mm in this decade.
09-04-18, 11:37 AM
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I don't think the time bomb has exactly exploded, yet. I think you're looking at the time bomb between the "Ka-" and the "-boom!"
Failure mode details. One spoke pulls out of the rim. Best case, the rim is out of true and rubs the brake, bringing you to a gentle stop or, really best case, you're dragging the brake all the way home. Worst case, a bunch of spokes pull out right after that first one, the bike stops, you go over the bars and hit a telephone pole, or roll under an eighteen wheeler just past the stop sign you just flew through.
Continue riding that wheel as long as you're on first-name friendly relationships with all 12 of your guardian angels.
Failure mode details. One spoke pulls out of the rim. Best case, the rim is out of true and rubs the brake, bringing you to a gentle stop or, really best case, you're dragging the brake all the way home. Worst case, a bunch of spokes pull out right after that first one, the bike stops, you go over the bars and hit a telephone pole, or roll under an eighteen wheeler just past the stop sign you just flew through.
Continue riding that wheel as long as you're on first-name friendly relationships with all 12 of your guardian angels.
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