Bicycle Mechanics - 13T vs 11T Pulleys
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12-05-01, 09:09 PM
Steve's reply to my 39T chainring question reminded me of a question I wanted to ask. In reading about the new triples that are out (Dura Ace and Record) and their accompanying components, I noted that one of the new rear ders has 13T pulleys. I assume that more teeth allow the pulleys to turn slightly slower, presumably reducing wear, etc., etc.. Any other thoughts on using 13T pulleys? Is it possible to retro fit other ders with them? I assume the diameter would have to be greater. Is there any reason to do such a retro fit?
Regarding sealed bearing pulleys, whether 11T or 13T, is there a brand that is considered better?
13 tooth pulleys? Are you sure? Derailleur pulleys always used to be 6 or 7 teeth (if my memory serves me right). Of course, Huret used to make pulleys which had no teeth, but that's ancient history, now. 13 teeth will be larger than the high gear cogs on most road bikes today (something like 1 1/2" diameter!!)
12-06-01, 06:50 AM
D*Alex, that's what I was thinking. Yet in a half page write up in the latest Velo News on the new DA and Record triples and associated ders they specifically mention that one of the rear ders has 13T pulleys. Can't remember which one off the top of my head.
I would think that because the diameter is larger one probably cannot retro fit other ders with the larger pulleys.
On a possibly related note, I had asked in another thread about the pulley noise when in the big ring. The answer was increased chain tension. I checked this morning and, sure enough, when I shifted to smaller cogs the noise lessened. Unfortunately, I seldom get past 52-18 so I don't get to hear the silence. :(
Perhaps 11T pulleys do not have 11 teeth (and therefore 5.5"/pi = 1.75" diameter!) , but are designed specifically for 11T high-gear cogs.
12-06-01, 10:12 AM
You are correct John E, the diameter looks like about 1.75"; I'd have to take one off to get a more exact measurement. So a 13 would be about 6.5/pi=2" approx. Hard to tell if there is enough clearance for that. The question still remains on the table - do the extra teeth have a significant advantage or is it marketing hype?
Also any suggestions on brand of sealed bearing pulleys?
12-06-01, 10:52 AM
The 13's would have a larger dia. and possibly might not be compatible with some der.'s.
I still have a pair of old sun tours that have only 10 and I noticed the jockey --- or the pully that's nearest the free wheel is pretty badly worn.
The larger the dia. the slower the wear would be. If I were going to buy some new ones I think in general I would go with the 11 tooth, unless someone had experience with the 13's on a like derailuer to mine, and knew they would work.
On brand, there are so many out there that would be hard.
I think again I would go with an alloy type rather than the resin like my old sun tours, as I recall the ones I have dont have a lot of miles on them and they are worn pretty badly, but then they probably came off my old MT.bike.
I know I had a pair on the Bianchi several years old when I sold it, they had a lot of miles on them but were still in good condition.
Anyway try a pair you will be suprised at the diffrence, not just the noise, but the reduced friction, gives you a free 1 - 2 miles an hour, I allways noticed it the most on the hills, where every little bit helps.
Now that I have talked myself into it, doggone it, im going to have to buy a new pair, mine are to worn to use. #@***
12-06-01, 12:30 PM
According to Shimano's site, DA is still coming with 11T pulleys. However, it would not surprise me in the least if they introduced their "innovative" 13T pulleys and encouraged everyone to replace their "out of date" derailleurs with the newer ones. The only other reason I can think of for using larger pulleys is to use a little more chain w/o increasing cage length. This would be more suitable for MTBs as they typically run a wider range of gears. Who knows what the big S will dream up next to get us to replace gear that doesn't need replacing.
Is it really possible to wear a DA rr. der out? Other than pulleys, I would think they would last damn near forever.
12-06-01, 01:18 PM
Just for grins I went to Performance Bike and looked up the DA Triple rear der. Sure enough, the description says 13T pulleys.
Changing the jockey wheel size could be a legitimate way to match a given derailleur to a particular cogset. A 13-26 cogset with an 11T jockey pulley would have about the same cog-to-jockey distance as an 11-24 with a 13T jockey. As others have mentioned, a larger pulley implies not only the closer chain coupling mentioned above, but also longer pulley and bearing life and more chain.
12-06-01, 04:30 PM
After doing some digging, here is the scoop per Shimano's Euro website (which I find to be far superior to the US one) The 13 tooth pulleys are to shorten the cage length on the GS capacity derailleur "for better looks as a road component forum." The larger pulleys and slightly longer cage allow for a total capacity of 38T instead of 29T for the standard SGS length. Looks like the 13T pulleys are not retrofittable but are also not a required element for non-triple users.
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