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Old 02-25-06, 12:00 PM   #1
dnlpnd
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7-Speed to 9-Speed Conversion

I am in the process of converting a 7-Speed crank arm over to a 9-Speed crank arm. I am being told two things by my LBS that I am wondering if they are true.

1.) I need new 9-Speed compatible chainrings.
2.) I need to replace the chainring bolts with 9-Speed compatible/spaced bolts

Does anyone foresee any problems with finding 9-Speed compatible chainrings with 110mm, five bolt hole pattern?

Hyper-links to 9-Speed chainrings and 9-Speed bolts would be appreciated.

Thanks,

dnlpond
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Old 02-25-06, 12:05 PM   #2
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1. You don't NEED 9-speed compatible chainrings. Your current crank should work fine. Specific 9-speed chainrings are slightly closer together than 7 or 8-speed cranks but the difference is minimal and most users report no problems using the older style cranks.

2. 9-speed spaced chainring bolts???? I think your LBS is either kidding you are trying to pick your pocket. AFAIK, there are no such things. The only thing I can imagine is if your 7-speed crank is one of the odd triples that use one set of bolts to hold all three chainrings together. Otherwise bolts is bolts.
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Old 02-25-06, 03:15 PM   #3
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Quote:
Originally Posted by dnlpnd
I need to replace the chainring bolts with 9-Speed compatible/spaced bolts
. Are you sure you got that right? Like HR says, bolts is bolts to me.
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Old 02-25-06, 03:23 PM   #4
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The chainring bolt thing was the issue I was most skeptical about. That would explain why I have been unable to find 9-Speed specific bolts.

However, I am hearing arguments both ways on the 9-Speed specific chainrings. I am running a non-ramped and pinned triple that was mated to a seven speed cassette.

Are you guys sure this things is ever going to shift right without 9-speed specific chainrings? If I can find something ramped and pinned would probably help too.

Thanks,

dnlpnd
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Old 02-25-06, 03:35 PM   #5
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I would suggest you read this page and this page by Sheldon Brown.

Unless you have an old Dura Ace derailleur (which doesn't use the same amount of cable pull as the others), the only things you need for you 7- to 9-speed conversion are:
– a 9-speed cassette;
– a 9-speed (right) shifter;
– a 9-speed chain.

In theory, 9-speed chainrings are slightly closer to eachother than were 7 or 8-speed chainrings, but in practice, unless you race and shift the front while standing, you won't see any difference.

As for 9-speed bolts... I checked my calendar, but we aren't on April 1st yet.
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Old 02-25-06, 04:07 PM   #6
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Your current non-ramped, non-pinned chainrings are going to shift a bit more sluggishly and more poorly under high loads than more modern designs. And yes, the improvements are real. However, your old crank will shift as well as it does now and if that's been satisfactory then stay with it.

Finding 9-speed chainrings for a 110 mm BCD crank is a bit more problematic as most new road cranks are 130 or 135 mm BCD and mountain bikes are 96 mm. The only current road cranks in that bolt circle come with "compact" (50/34 or thereabouts) chainrings. Sheldon Brown offers TA chainrings in a huge range of tooth counts in 110 BCD but they aren't "9-speed spaced" and don't appear to have the current shape enhancements
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Old 02-25-06, 04:42 PM   #7
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Yeah, the only reason it would be worth updating your chainrings is for quicker shifting with pins specially profiled teeth. The "7-speed" chainrings will work fine with a 9-speed chain, though.

Actually, 9-speed chainrings should be easy enough to find for a 110mm BCD crank, since compact-double cranksets are getting increasingly popular. I got an FSA 50t chainring with 110mm bolt circle for my good road bike - see this picture:
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Old 02-25-06, 09:37 PM   #8
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Quote:
Originally Posted by HillRider
Your current non-ramped, non-pinned chainrings are going to shift a bit more sluggishly and more poorly under high loads than more modern designs. And yes, the improvements are real. However, your old crank will shift as well as it does now and if that's been satisfactory then stay with it.

Finding 9-speed chainrings for a 110 mm BCD crank is a bit more problematic as most new road cranks are 130 or 135 mm BCD and mountain bikes are 96 mm. The only current road cranks in that bolt circle come with "compact" (50/34 or thereabouts) chainrings. Sheldon Brown offers TA chainrings in a huge range of tooth counts in 110 BCD but they aren't "9-speed spaced" and don't appear to have the current shape enhancements
Actually, there's a better selection in 110 BCD than any other bolt circle, it is the most versatile BCD in existence.

The current TA chainrings mostly do have pins and ramps, except models designed for the innermost position (the pins and ramps only help with upshifting, and you never upshift to the innermost chainring.)

I believe the current TA 110 chainrings are "9-speed compatible" as much as that actually exists outside of the imagination of the marketeers. Even the marketeers don't claim that this is an issue for the outer rings, but the teeth of the inner rings are s'posed to be displaced slightly to the right.

I get asked about so-called "9-speed" chainrings a lot, so much that I have a boilerplate response I can paste into an email with a couple of mouse clicks. Here it is:

There is a lot of confusion about the compatibility of narrow 9-speed chains with older cranksets. Shimano says you should replace the inner chainring(s) with specially designated 9-speed ones, but then they're all too eager to sell you stuff, whether you need it or not.

Shimano is also concerned about clueless users. The worst-case scenario is that you will be riding along with the bike in its highest gear (large front, small rear) and then for some bizarre reason shift down in front before downshifting in the back. (There is no shift pattern in which it is reasonable to shift in this sequence.) If you _do_ shift this way, there's a small chance that the chain might "skate" over the edges of the teeth for maybe half a turn.

In practice this "problem" almost never materializes. Many, many cyclists are using 9-speed chains with older cranksets and having no problems whatever.

My advice is to go ahead and upgrade your drivetrain, but leave the crankset alone until you've tried it out with the new chain. Most likely, you don't need to do anything to it.
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Old 02-26-06, 09:29 AM   #9
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The current TA chainrings mostly do have pins and ramps, except models designed for the innermost position (the pins and ramps only help with upshifting, and you never upshift to the innermost chainring.)
Nice to know. Your web site didn't make any mention of the tooth shape on the TA rings so I assumed they were not enhanced.

Is it true that the ramps and pins don't help with downshifting? I thought they did. I know on Shimano triple cranks that both the outer and middle chainrings have shaped teeth and ramps while the granny is completely flat. My experience (using the same model front derailleur, shifters and chain) is that the newer chainrings downshift under load much better than their unshaped predecessors.
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Old 02-26-06, 09:38 AM   #10
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FWIT, I have a bike with a 9 speed cassette running to a 7 speed crank. There are some times when the chain "skates" along the top of middle chainring, but these times are very few.

On this bike I have a 49/42/30 chainring combination, and there are no ramps or pins on the middle chainring. It shifts fine. I have a different bike with a 9 speed campy crank where I put a rampless engagement ring into the middle position and it did not shift so well. In fact, I had to file two teeth down to get it to shift at all. The large chainring is TA and has ramps and pins.
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Old 02-26-06, 02:21 PM   #11
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Quote:
Originally Posted by HillRider
Is it true that the ramps and pins don't help with downshifting? I thought they did. I know on Shimano triple cranks that both the outer and middle chainrings have shaped teeth and ramps while the granny is completely flat. My experience (using the same model front derailleur, shifters and chain) is that the newer chainrings downshift under load much better than their unshaped predecessors.
For downshifting in front, all you have to do is make the chain derail from the larger ring, and it will fall onto the next smaller ring. Truncated teeth may help the chain derail easier, but the pins and ramps do nothing for this.

Upshifting is much harder, because the chain has to grab onto something so that it can get lifted up to the larger chainring. That's where the pins and ramps help.

Generally it's a mistake to expect front shifting to work well under serious pedalling load, since the front derailer has to work with the tensioned run of the chain. The rear derailer uses the slack return run for shifting, so rear derailers will always shift better under load than fronts.

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Old 02-27-06, 10:22 AM   #12
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With an old 7sp 110bcd RSX crank (24-36-48), I have occassional problem shifting from 36 to 24 with 9 speed setup/chain - where chain shifts into the gap between the 24 & 36 chainring. Usually happens when shifting and pedaling too slowly - it is a nuisance & hazard if riding with others. I have not resolved the problem yet as I do not ride the bike that often. So I would "try" to have "8/9 speed" front crank vs 6/7 speed.

Good luck.
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Old 02-27-06, 10:59 AM   #13
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6, 7 and 8-speed cranks have the same chainring spacing. The narrower spacing began at 9-speed.

On your RSX, try loosening the front derailleur's inner travel stop screw a quarter of a turn or so at a time to get a more forceful shift. Also, fit a Third Eye Chain Watcher or similar stop to the seat tube to assure the chain won't spill to the inside of the granny ring. These two changes should solve your shifting problems. BTW, did you change the chainrings from stock on the RSX? My son's came geared 26-36-46.
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