Singlespeed & Fixed Gear - Bent a chainring on a fixed gear?

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Eire Mick
01-20-09, 10:08 PM
I had a big ride last Sunday. Before hand, I noticed that my chain was not as tight as I'd like, but figured I'd get through it and deal later. But, after the ride (some big declines that required lots of skids) I noticed that my chain was REAL tight. So I went to my LBS today to see what's up with that. I thought the force on my slowing was pulling my rear wheel back on the drop outs that resulted in tightening the chain, but my boy at the shop said I may have bent my chain ring making it slightly oval, and not round anymore. Is that possible? I run brake-less, and only stop via skip/skids. I'm 6'1 190lbs. Just wondering.....now I need a new chain ring cause it's totally noticeable. All good tho, cause I found a sick anodized Pake 46t 170mm for $60 on ebay, but do I need a better/stronger chain ring?
I doubt that your chainring actually is bent... probably shifted a bit.
http://sheldonbrown.com/fixed.html#tension
Try Sheldon's method out before buying a 60 dollar ring.
1fluffhead
01-21-09, 10:02 AM
I had a big ride last Sunday. Before hand, I noticed that my chain was not as tight as I'd like, but figured I'd get through it and deal later. But, after the ride (some big declines that required lots of skids) I noticed that my chain was REAL tight. So I went to my LBS today to see what's up with that. I thought the force on my slowing was pulling my rear wheel back on the drop outs that resulted in tightening the chain, but my boy at the shop said I may have bent my chain ring making it slightly oval, and not round anymore. Is that possible? I run brake-less, and only stop via skip/skids. I'm 6'1 190lbs. Just wondering.....now I need a new chain ring cause it's totally noticeable. All good tho, cause I found a sick anodized Pake 46t 170mm for $60 on ebay, but do I need a better/stronger chain ring?
You talk about needing a chainring then give a quote on a cranks......So which is it? If you have bent your chainring buy a new one. Just match up the bcd with your current cranks.
Eire Mick
01-21-09, 03:50 PM
I doubt that your chainring actually is bent... probably shifted a bit.
shifted? I'm sorry, but what do you mean shifted? Like the bolts weren't tight enough and they moved on the bolts?
Eire Mick
01-21-09, 03:58 PM
You talk about needing a chainring then give a quote on a cranks......So which is it? If you have bent your chainring buy a new one. Just match up the bcd with your current cranks.
Right, but I was actually in the market for a whole new crankset anyways, so we'll see.
I doubt that your chainring actually is bent... probably shifted a bit.
shifted? I'm sorry, but what do you mean shifted? Like the bolts weren't tight enough and they moved on the bolts?
What I think he means, or what i mean now, is that it moved on the bolts. St. Sheldon recommends to loosen and re-tighten the bolts for a centered fit. Chainrings don't (usually, in my experience) bend like that. When a circle is, even loosely, affixed at 5 points, it dosen't ovalize.
when you pedal, does the chain kind of have a "heartbeat" where it bounces at even intervals? If so, you might have a bent chainring.
Eire Mick
01-21-09, 04:43 PM
when you pedal, does the chain kind of have a "heartbeat" where it bounces at even intervals? If so, you might have a bent chainring.
A heartbeat is almost not enough to explain it. Say I run the cranks real quick to get the wheel going, it slows down fast and when it stops, it almost comes to a hault. It's like if I had a brake pad that wasn't centered on the wall and it would rub on only one part of the wheel. Once it slowed down enough, it would finally come to a hault. Previously, when I would run the cranks the same way, the wheel would run smoothly until finally it came to a slow stop.
Eire Mick
01-21-09, 04:45 PM
A heartbeat is almost not enough to explain it. Say I run the cranks real quick to get the wheel going, it slows down fast and when it stops, it almost comes to a hault. It's like if I had a brake pad that wasn't centered on the wall and it would rub on only one part of the wheel. Once it slowed down enough, it would finally come to a hault. Previously, when I would run the cranks the same way, the wheel would run smoothly until finally it came to a slow stop.
I meant when I run the cranks while off the bike. There is noticeable friction at one point when I pedal on the bike.
so did the LBS guy see your chainring, and tell you it was bent? It could be the BB as well, slowing you up like that. Is the chain now correctly tensioned, or still super tight? If it's tight, loosen and see if this still occurs.
I meant when I run the cranks while off the bike. There is noticeable friction at one point when I pedal on the bike.
Couldn't a sticky link also cause this?
A heartbeat is almost not enough to explain it. Say I run the cranks real quick to get the wheel going, it slows down fast and when it stops, it almost comes to a hault. It's like if I had a brake pad that wasn't centered on the wall and it would rub on only one part of the wheel. Once it slowed down enough, it would finally come to a hault. Previously, when I would run the cranks the same way, the wheel would run smoothly until finally it came to a slow stop.
If it comes to a halt, it is binding due to too much tension. Do what Sheldon says in the link that I posted above.
Eire Mick
01-22-09, 01:18 AM
Allright, so basically adjust the chain ring bolts to get it centered, which, according to sheldon and ya'll, it should give me some answers. I just think it's weird that they (whomever makes the chain rings and cranks) would make their product with this possibility. Maybe I'm wrong, but if I'm making these products, I would make the bold diameters and the chain ring bolt cavity diameters match, so "shifting" would be impossible. Then again, if I'm running a typical 5 star system, and a certain amount or pressure is put on a given section of the star, then that could actually bend. You know what?, fk it, I'll go get that sick pake crank set I've wanted anyways and go for a ride.
Eire Mick
01-22-09, 01:23 AM
so did the LBS guy see your chainring, and tell you it was bent? It could be the BB as well, slowing you up like that. Is the chain now correctly tensioned, or still super tight? If it's tight, loosen and see if this still occurs.
He just offered an opinion and I took it as he's supposed to be the expert. I just ride. Do you really think there could be a BB prob? If that's the case, then I'm really starting to realize the reason some equip costs 200% more than others. Typically, I ride hard with a pretty cheap bike. I"ve been upgrading as I go, but honestly, I've been ignoring the BB.
Eire Mick
01-22-09, 01:25 AM
I doubt that your chainring actually is bent... probably shifted a bit.
http://sheldonbrown.com/fixed.html#tension
Try Sheldon's method out before buying a 60 dollar ring.
Ok, gonna work on this tonight and ride about 20 mi tomorrow. This makes the most sense. I mean darn, I ride hard, but not hard enough to bend.
He just offered an opinion and I took it as he's supposed to be the expert. I just ride. Do you really think there could be a BB prob? If that's the case, then I'm really starting to realize the reason some equip costs 200% more than others. Typically, I ride hard with a pretty cheap bike. I"ve been upgrading as I go, but honestly, I've been ignoring the BB.
potentially, yes it could be the BB. That'll slow the drivetrain like you described. but i don't follow about what you're saing about how some equipment costs 200% more than others.
bbattle
01-22-09, 05:23 PM
I'd take the bolts off, rotate the chainring one bolt hole, then retighten the bolts back on. Be sure to do the bolt #1, then bolt #3, then #5, then #2, etc. Just get them snug at first, then tighten a bit as you go, to get an even tension on all the bolts. Just like tightening a drum head.
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