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How to know when to change chainrings

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How to know when to change chainrings

Old 03-26-20, 08:56 AM
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masi61
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How to know when to change chainrings

I learned last season that the middle ring on my Ultegra 6603 triple crank was completely worn out. It would totally drop a new chain at the most inopportune time. When standing to start out in traffic (when the light turns green) the chain would catastrophically disengage potentially causing a crash or further component damage. So call that a learning moment. Visually the valley at the base of each chainring tooth was flattened, a lot. I guess you could say I rode that 39 tooth chainwheel to death.

But now I’m wondering about those high mileage chainrings that haven’t yet failed in such spectacular fashion. I purchased a used Dura Ace 7803 triple crank for not much money. The mileage is unknown. I swapped it in place of the above mentioned Ultegra 6603 since I needed to keep riding and I had not located the 39 tooth chainring yet.

So I have been riding the unknown mileage used Dura Ace 7803 triple. What I notice is that no matter what chain I run the chain is noisier than it should be compared to my double chainring bike. The phenomenon is more noticeable in the 39 and 30 tooth rings. Now, I do wax my chains and I have experienced that waxed chains are in general noisier than wet lubed chains. But I have also gotten lucky and occasionally had a silent waxed chain for more than a couple rides.

Which leads me back to the discussion of chainring wear. In your experience, do you consider increase in noise a warning sign that the chainrings are at the end of their service life?

BTW: It appears that finding replacement chainring sets for Shimano road triples (which have been all but discontinued) is about to become one of these “white unicorn” scarcities. I emailed Wickworks an aftermarket chainring maker to inquire about road triple chainring sets and they were polite but said that they discontinued them for lack of demand. Maybe I will message Wolf Tooth and pitch the idea to them.

I have built up double cranks with Salsa chainrings and found them to be smooth running but maybe a bit slow shifting due to having no ramps or pins. Triple cranks need ramps and pins more than doubles I think which is why I believe there should be an aftermarket for a nice triple ring set for Shimano road triples. KCNC makes a really nice “Cobweb” MTB triple chainring set with a trekking friendly tooth count of 48-36-24. Unfortunately the BCD is 104/104/64, 4 bolt. I’m not sure what crank arms these fit but just wish I could run some for the road somehow.
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Old 03-26-20, 09:19 AM
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I was able to locate a Cannondale Hollowgram crank adapter in the 104/104/64 bcd spider. This would permit the use of the nifty KCNC Cobweb triple cranks. I only have one frame that takes the 30 mm Hollowgram crank - a CAAD9 Cannondale with BB-30 bottom bracket. I have all the parts to build this frameset up. Since my knowledge of these Cannondale Hollowgram crank/BB30 bottom bracket is confined only to what I have read on-line, I may ask my Cannondale dealer/LBS help me get a creak free build.
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Old 03-26-20, 10:35 AM
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Yes, I know by ear.
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Old 03-26-20, 11:52 AM
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New chainrings are square or slightly radiuses across the top of the teeth. Worn chainrings get real pointy looking.
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Old 03-26-20, 12:13 PM
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The way I knew is the same way you knew, by doing standing starts on a chainring and it slips. In my case though it was a standard BCD, I forget if it was 110 or 130. I replaced it and no more problem. Why they went away from the old standard is beyond me, except of course to lock everyone in.
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Old 03-26-20, 01:33 PM
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Originally Posted by andrewclaus View Post
Yes, I know by ear.
Can you describe what you hear? What let’s you know it is almost time to replace?
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Old 03-26-20, 01:44 PM
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Originally Posted by zacster View Post
The way I knew is the same way you knew, by doing standing starts on a chainring and it slips. In my case though it was a standard BCD, I forget if it was 110 or 130. I replaced it and no more problem. Why they went away from the old standard is beyond me, except of course to lock everyone in.
SKU reduction for greater profits, which also drove the move to threadless stems and more cogs.

Add a cog, shrink the double small ring to 34T, you have the same range as triple cranks with the defacto standard 30 small ring, and get rid of triple shifters/front derailleurs.

Unfortunately, you can't fit a ring smaller than 38T on a standard 130mm Road BCD so you end up with a 110mm BCD crank which isn't as stiff.

Switch to 4 arm crank spiders, put the crank arms for pedals between a pair, move the spider arms on either side closer together, and you match 5 arm 130mm BCD road crank stiffness so you can discontinue them.

Now you have one set of crank arms per length per level, not three when triple cranks and compacts overlapped in the mid 2000s.

With threadless stems, bike companies could stock one fork size for all frame head tube lengths or maybe two if they used different trail for larger and smaller frames.

With With 8 speed Exadrive Campagnolo sold 11-18, 11-21, 11-23, 11-26, 12-19, 12-21, 12-23, 13-21, 13-23, 13-26, and 14-26 cassettes so people could compromise as desired between range and spacing.

Now 11-23 11 cogs gives you the spacing, high-gear, and low-gear of 11-18, 11-21, 11-23, 12-23, 13-21, and 13-23. 12-25 covers 12-19, 12-21, 12-23, 13-23, 13-26, and 14-26 (apart from the junior roll-out restriction). That's 2 combinations not 11 although a few more are available including none with 13 or 14 starting cogs.

With 12 cogs they only offer 3 combinations:

11-29: 11-12-13-14-15-16-17-19-21-23-26-29
11-32: 11-12-13-14-15-16-17-19-22-25-28-32
11-34: 11-12-13-14-15-16-17-19-22-25-29-34

With so little wrap difference, that eliminated the market's call for
derailleurs in both small and medium sizes (long went out with the triple).

Last edited by Drew Eckhardt; 03-26-20 at 01:49 PM.
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Old 03-29-20, 02:23 PM
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Drew, that does make some sense. I did rent a Roubaix with a 50/34 up front and an 11sp 11-34 in the back and having that 34/34 combo was eye-opening, especially in hilly SanFran. That was a very wide range on a bike that otherwise felt like a normal roadie. There was hardly an old standard sized component on the bike. If I had needed to make even a simple repair, like fixing a flat, I'd have had trouble since I wouldn't even know how to take off a thru-axle wheel.
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