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Old 07-18-08, 11:02 AM   #1
quester
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Need *strong* ATB crankset for LHT

After about 3000 miles (carrying my extremely large butt), my LHT complete is a chorus of sounds when going up hill: creaks, squeaks, etc. As I'm embarking on a long tour in September, it's going in the shop next week.

The mechanic said that the bottom bracket might need to be replaced. Also, the large chainring visibly wobbles even when not under load. So the chainrings might need to be replaced as well.

So, I'm thinking of using this as an opportunity to get below the 19.2-inch lowest gear I currently have, by going to a mountain crankset w/ a 22-tooth granny.

However, the chainrings need to be strong. Chainrings visibly bend when I put pressure on them and, as described above, this seems to be a problem.

Any suggestions? I use only friction shifters, so I assume that they can stay, but what about the rear derailleur? It's currently the stock Shimano XT RD-M761 SGS long cage.

Cheers,
pete
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Old 07-18-08, 11:12 AM   #2
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http://www.surlybikes.com/new/crank_pop.html

(they say the mtn triple has aluminum large rings but I'm sure it's not too hard to get steel ones instead)
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Old 07-18-08, 12:53 PM   #3
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Are your chain-rings actually bent? or is it simply the staggering in the tooth profile? Most modern rings have some variance in the size and position of the teeth in order to improve shifting performance. Unless you have bashed the rings on something I have trouble believing that you bent them under normal riding conditions, even if you are very large. I could believe that your cranks aren't on straight, or that you have some gunk in the joint that is causing noise, but bent chain rings are pretty rare unless they have been smashed into something.
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Old 07-18-08, 01:02 PM   #4
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I'm guessing you mean that the crank bends, and not the chainring? I can't imagine hoe you'd see the ring itself bending while you're standing on the crank. Anyway - I'd go for either a RaceFace forged crankset, or Shimano Saint (you'd probably have to buy a new BB with the Saint set, but it sounds like yours is goosed anyway).

Have a look at MTBR Reviews.
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Old 07-18-08, 01:56 PM   #5
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I'm guessing you mean that the crank bends, and not the chainring?
Nope, on pretty much every bike I have, if I have it on the biggest chainring and am seriously pushing, the top of the chainring visibly bends out. This seems to imply that the top of the chainring is providing most of the contact w/ the chain, which really shouldn't happen, but nonethless it does. This definitely happens on my Jamis Quest as well, and I've certainly seen it before.

Noone else does this? Maybe I should post in the Clydes.... Not only am I a very big guy, but I have quads to match, so I can generate some power.
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Old 07-18-08, 02:13 PM   #6
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Blimey! Another (expensive) suggestion is to get a Rohloff set-up, so that you can install a super-heavyweight single front chainring, a super-heavyweight single-speed chain, and a set of gear ratios low enough that you don't have to apply herculean force to the cranks!
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Old 07-18-08, 02:19 PM   #7
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"Nope, on pretty much every bike I have, if I have it on the biggest chainring and am seriously pushing, the top of the chainring visibly bends out."

I think that would be from frame flex at the bottom bracket. Same reason why there is chain rub on poorly adjusted front derailleurs when cranking hard in a sprint or uphill but not in normal usage.
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Old 07-18-08, 03:57 PM   #8
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Blimey! Another (expensive) suggestion is to get a Rohloff set-up, so that you can install a super-heavyweight single front chainring, a super-heavyweight single-speed chain, and a set of gear ratios low enough that you don't have to apply herculean force to the cranks!
I could always shift down, but just don't want to! Low gears are not a problem.

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I think that would be from frame flex at the bottom bracket. Same reason why there is chain rub on poorly adjusted front derailleurs when cranking hard in a sprint or uphill but not in normal usage.
Well, first I'm glad that I'm not unique. However, this doesn't explain why the big chainring wobbles when not under load. I'll take it off tomorrow just to make sure I'm not imagining things.

At any rate, what ATB cranksets do people put on LHTs?
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Old 07-18-08, 04:20 PM   #9
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Go with a shimano crankset that uses outboard bearings. You can use an LX, Hone, SLX or XT. The SLX uses the same carbon/stainless steel middle ring as the XT but costs less. I plan on using an SLX crankset with an Action Tec titanium 20 tooth granny, the stock 32t carbon/stainless ring and then one of the 46T shimano chanrings.

On my LHT I used the Hone crankset with no problems, I was also running friction gears on the front, no problems.
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Old 07-18-08, 06:30 PM   #10
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Go with a shimano crankset that uses outboard bearings. You can use an LX, Hone, SLX or XT. The SLX uses the same carbon/stainless steel middle ring as the XT but costs less. I plan on using an SLX crankset with an Action Tec titanium 20 tooth granny, the stock 32t carbon/stainless ring and then one of the 46T shimano chanrings.

On my LHT I used the Hone crankset with no problems, I was also running friction gears on the front, no problems.
Outboard bearings will make it stiffer, and hopefully longer lived?

So something like this would be a drop-in replacement? What about the front derailleur?
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Old 07-18-08, 06:38 PM   #11
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Go with a shimano crankset that uses outboard bearings. You can use an LX, Hone, SLX or XT. The SLX uses the same carbon/stainless steel middle ring as the XT but costs less. I plan on using an SLX crankset with an Action Tec titanium 20 tooth granny, the stock 32t carbon/stainless ring and then one of the 46T shimano chanrings.
I think the SLX uses a 64mm BCD inner ring. According to sheldon, the minimum-size ring would be 22-tooth. ??
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Old 07-19-08, 02:10 AM   #12
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Action-tec makes it, check out their prices page. The heat treated ti chainring is 75, and the non heat treated one is 52.

At the shop I work at the SLX crankset sells for 189, ask your lbs if they can get them.
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Old 07-19-08, 02:16 AM   #13
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Outboard bearings will make it stiffer, and hopefully longer lived?

So something like this would be a drop-in replacement? What about the front derailleur?
It'll be much stiffer because of the outboard bearings and also the stiff hollow arms and the integrated spindle. Another nice benefit of these cranks is that you dont need a crank puller to take off the crank arms.

The front derailleur you have now will work fine.
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Old 07-19-08, 02:39 AM   #14
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I could always shift down, but just don't want to! Low gears are not a problem.



Well, first I'm glad that I'm not unique. However, this doesn't explain why the big chainring wobbles when not under load. I'll take it off tomorrow just to make sure I'm not imagining things.

At any rate, what ATB cranksets do people put on LHTs?
I've got a slightly older version of this 48-36-26T LX trekking crank on mine. I quite like it.

http://bike.shimano.com/publish/cont..._mountain.html

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Old 07-19-08, 02:42 AM   #15
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spin spin spin

Any time you are using the big chainring you should be spinning, not mashing. Work on your technique before the surgeon has to work on your knees.
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Old 07-19-08, 05:23 AM   #16
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Any time you are using the big chainring you should be spinning, not mashing. Work on your technique before the surgeon has to work on your knees.
One size doesn't fit all....
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Old 07-19-08, 05:40 AM   #17
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One size doesn't fit all....
It sounds like you're a born single-speeder! No gears - just try harder!!! AND... singlespeed kit doesn't have to be delicate to suit 9-speed cassettes, so you can buy super-beefy rings/chains/sprockets. AND... you can strip all the faffy 'adjustable' bits off your bike. Cheap, low maintenance, no XTR-shifter-snobbery, but super-light and loads of street points.

You could start your own 'single-speed touring' forum, where normal cyclists would be scared to tread!
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Old 07-19-08, 12:23 PM   #18
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To actually respond to your request, here are some strong chainrings: Surly.

They're made of stainless steel and they'll most likely outlast you. I use them on a couple of my bikes and they work great.
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Old 07-20-08, 10:57 AM   #19
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One size doesn't fit all....
I agree. When the "pros" talk about spin they are thinking 90rpm and greater. I can probably count on my fingers the times I've hit 90 in the last year. Very often on the flat with a tailwind I enjoy pedaling in the leisure mode. Still it is amazing how comfortable it is on my body and easy on my gear, to downshift on the hills or headwinds and bring the spin up to 70-80. There are always those steep grades that show up at the end of a climb that catch me off guard and I stand and mash, but by that time I'm in the smallest chainring. The smallest ring can take those stresses because it has a compact structure compared to the bigger ones.
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Old 07-22-08, 08:05 PM   #20
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I think that would be from frame flex at the bottom bracket. Same reason why there is chain rub on poorly adjusted front derailleurs when cranking hard in a sprint or uphill but not in normal usage.
I actually watched this the other day on a climb, and sure enough, the frame was flexing quite a bit. It was actually a bit alarming.

Also, though, the big chainring is definitely a bit bent. Between the bent chainring, a pitted bottom bracket, and my fear of the hills on the pacific coast, I think I will take other advice on this thread and put in a mountain crankset. Ummm.....22 tooth granny......
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Old 07-23-08, 09:31 AM   #21
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If you bend your large chainring back w/ pliers, will it stay put or bend again? I had a huge dent in my chainring once and I just pulled it back into flattishness. But I am not really the size to get it to rebend again just through pedalling.
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Old 07-23-08, 10:26 AM   #22
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Any time you are using the big chainring you should be spinning, not mashing. Work on your technique before the surgeon has to work on your knees.
+1, but it isn't just the number of rpms, it also has to do with having a smooth stroke. Pedal circles and it will reduce the flexing greatly. That said higher rpms is the easiest way to learn to pedal circles rather than just stomping up and down.

I also think that before you bend the crank with normal pedaling that the frame would be flexing a LOT. In fact I would have thought it difficult or impossible to bend the crank by pedaling without breaking the frame.

The appearance that the chainring is bent or the crank flexing can be that the bottom bracket is worn or loose. It can also be that the crank arms are not properly installed or tightened on the BB.
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Old 07-23-08, 11:18 AM   #23
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i would not advise bending metal back to its original shape. some how you applied a stress to cause it to yeild. next time you apply a simiar or greater stress it will fail, not yeild.
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Old 08-06-08, 07:56 PM   #24
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I actually watched this the other day on a climb, and sure enough, the frame was flexing quite a bit. It was actually a bit alarming.

Also, though, the big chainring is definitely a bit bent.
To wrap this up, I went ahead and got a new mountain crankset, installed it (not a single local LBS sold the right BB tools!), and now am very happy. The bike is quiet, presumably stronger, and I'm sure I will be happy to have 10% lower gearing on my upcoming tour.

One other note: I think the way my big chainring got bent was that I tend to coast resting most of my weight on the right side. Hopefully the SLX won't be as pliable, but I'm also trying to be more symmetric in my coasting.

Thanks for all the help!
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Old 08-11-08, 08:45 AM   #25
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my fix

Creaking is about always loose crank arms. I use Deore LX crankset with Deore front derailer on my 520 with barend shifter. Ultegra STI for shifting rear Deore Lx derailer. Shift in back much more than front and want to keep hands on levers.
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