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chainring teeth design for smoother shifting

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chainring teeth design for smoother shifting

Old 05-16-16, 11:23 AM
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spectastic
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chainring teeth design for smoother shifting

shimano's front shifting is pretty top notch, especially the 11 speed stuff. flip the lever and it just goes. however, my 3x8 bar end setup shifts like crap on the front, like I have to be spinning fast, and really ease off on the load in order to have it shift smoothly, otherwise, it just rubs. I'm running origin 8 3/32" chainrings (110 or 130, it can do both), which I assume was designed for tracks or fixies.

I'm trying to figure out why it shifts so poorly:
- is it the teeth design on the chainrings?
- the inflexibility of the 8 speed chain?
- the triple setup?
x the teeths are 46/40/30, so I know it's not the teeth gaps.
x I don't think it's the shifter, because it's a bar end, and has infinite trim... or is it?
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Old 05-16-16, 11:27 AM
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You've gotten too used to the sculpted teeth and pins on those fancy chainrings.
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Old 05-16-16, 11:32 AM
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I've been fine with friction shifting and full height chainring teeth, for 30 years, you may need work on your Technique.

When to shift , anticipating by reading the terrain ahead of You..

derailleur chains are all using bushingless construction now, the full bushing 3/32 chains are rare, so I doubt that is what you bought.
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Old 05-16-16, 11:44 AM
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Originally Posted by fietsbob View Post
I've been fine with friction shifting and full height chainring teeth, for 30 years, you may need work on your Technique.

When to shift , anticipating by reading the terrain ahead of You..

derailleur chains are all using bushingless construction now, the full bushing 3/32 chains are rare, so I doubt that is what you bought.
Origin8 Chainring 10H 44T 110/130 Silver 3/32 - Walmart.com
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Old 05-16-16, 11:51 AM
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I recently had similar trouble with FD on an old MTB(3x7)... have you tried the whole tuning process over from scratch?? Assuming all RD limits and indexing set... Release cable tension and turn in adjuster, set low limit, then properly set high limit, and finally moving up and down from middle ring and adjusting barrel adjuster as needed. Also, check FD cable/housing condition and possibly lube??
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Old 05-16-16, 12:02 PM
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File off some tooth tips ..

the companies started doing that at the bottom and top of the rotation, 6:00 & 12:00,
since that is where the power input is less , Bottom center for each pedal stroke.
and so the chain can make it up, off the chainring with less pedal force resisting it because the chain is under power .

old people do that by learning over the decades of riding older components. 'C&V'.

Last edited by fietsbob; 05-16-16 at 02:03 PM.
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Old 05-16-16, 12:04 PM
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Origin 8 chainrings are old school with no ramps, pins or cutouts. (I believe; I have only used their 1/8" ring, likewise a 110/130 BCD but I assume your 3/32" is similar.)

On the old-school rings, you have to usually move the front derailleur too far to initiate the shift, then bring it back to eliminate rub. Index shifters could not do that, so Shimano did a lot of work researching and designing teeth to not require that overshift. Drawback is that it is far easier for the chain to come off unintended from the modern chainrings. Origin 8 figures you are doing single chainring and doesn't provide the ramps for that reason.

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Old 05-16-16, 12:35 PM
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What front derailleur are you using?

Here is an analysis I did a while ago of an old Alivio triple derailleur.



The problem with the derailleur cage shape was that it was bent outward, and tended to trap the chain preventing it from climbing to the upper sprocket, rather than pushing it over onto the sprocket.

Shifting was improved by moving the derailleur so that it was mounted very high, and avoided using that slanted section of the cage.

A bent derailleur cage could have the same effect.

Everything was fairly worn on that bike. A new chain might have helped.

I do have one bike that shifts poorly to the outer ring (flat). The derailleur barely has enough throw, so adjusting it a bit wider would help. Maybe a different derailleur sometime.

On another bike with flat rings, I think the shifting was worse years ago, but the rings are now so worn that they look like they have natural shift ramps, plus a few rounded teeth. There is also a slight bend behind the crank arms which may also help with shifting (or over-shifting).
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Old 05-16-16, 01:41 PM
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Originally Posted by spectastic View Post
shimano's front shifting is pretty top notch, especially the 11 speed stuff. flip the lever and it just goes. however, my 3x8 bar end setup shifts like crap on the front, like I have to be spinning fast, and really ease off on the load in order to have it shift smoothly, otherwise, it just rubs. I'm running origin 8 3/32" chainrings (110 or 130, it can do both), which I assume was designed for tracks or fixies.

I'm trying to figure out why it shifts so poorly:
- is it the teeth design on the chainrings?
It's probably the pins and ramps. Shimano and Campagnolo do a better job than other manufacturers. I'd expect a similar engineering effort from SRAM but have no direct experience with their products.

- the inflexibility of the 8 speed chain?
Less flexible chains (within reason) shift better. I replace mine around 4500 miles due to degraded front shifting from side plate wear causing increased flexibility although they've yet to reach 1/32" of elongation.

- the triple setup?
My Campagnolo triple crank shifted faster than the 52-42 double I rode before it with friction shifting, faster than my FSA Carbon Pro Compact which followed, and faster than the FSA SLK-Light that replaced that.

x the teeths are 46/40/30, so I know it's not the teeth gaps.
Could be the teeth counts. Shimano designs their derailleurs around a certain big to middle ring drop.

At a minimum you'll need to adjust height and make sure the right derailleur bumps are hitting at the right times.

Last edited by Drew Eckhardt; 05-16-16 at 01:52 PM.
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Old 05-16-16, 02:22 PM
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Some chainrings that are designed for single crankset use have deeper valleys than derailleur chainrings. If it was my bike, and I wasn't satisfied with it's current performance, I'd acquire a matched set of chainrings that have all the fancy shifting aids.
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