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Clydesdales/Athenas (200+ lb / 91+ kg) Looking to lose that spare tire? Ideal weight 200+? Frustrated being a large cyclist in a sport geared for the ultra-light? Learn about the bikes and parts that can take the abuse of a heavier cyclist, how to keep your body going while losing the weight, and get support from others who've been successful.

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Old 03-31-07, 07:55 AM   #1
Chris in WCVA
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Chainring crankset swapout, anybody try it?

As you may know, I recently purchased a KHS MTB replacing the walmartorama clunker. Its got a 24,34,42 Shimano crankset which works like a dream (Who knew you could change gears without throwing the chain off! ), but its pretty obvious that, as I get into shape, If I keep riding this as a daily commuter i'm going to be spinning it out a lot. Assuming I don't go to a road bike and keep the KHS for trail riding, how hard is it to switch to a 50 or 52 chainring or a road crankset?
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Old 03-31-07, 09:04 AM   #2
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My bike was 28-38-48 with a 14-34 cassette. I changed to a 11-34 cassette and really made a difference. I almost never get off the 38 ring because 38/11 is almost the same as 48/14, the previous highest gear. This was a quick fix and nothing else needed to be changed.
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Old 03-31-07, 02:52 PM   #3
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I would definitely say look at changing your rear cassete. You could probably also increase the front chainring somewhat but after 48t on the big ring problems can begin because the curve of the derailer is designed for the curve of smaller rings. And unfortunatley if your front shifting is indexed shifting to a road derailer isn't really an option as shimano mountain and road indexing are not compatible

Paul
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Old 04-03-07, 08:50 AM   #4
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I would agree with the cassette change being the way to go as a first step if this is possible. If you go to one of the on line gear calculators you will see that going down one tooth in the rear has the same impact going up somewhere around 2.5 teeth. However, if your cassette starts with an 11 tooth cog then this is not an option as they do not come in a stock size with a smaller cog and even if they did it would be hard on your chain to wrap around a cog that small.

You can go to a larger ring(s) in the front but you will potentially need to change more parts than you expect. I have gone through this excercise several times in order to make old mountain bikes into winter commuters so I have encountered most of the issues.
The first thing to look at is whether you have an E type front derailleur or whether it clamps to the frame. The E type are mounted to the bottom bracket and have little or no height adjustment so you can not go to a larger ring with an E type.
Next issue is that the front derailleur will have a limit for the maximum gear range between the granny and the large ring, this is commonly 22 teeth on a triple so if you go with a large outer ring you may have to change the middle and granny as well in order to stay in this range. (I run 48, 38, 28 on my commuter bikes)
Then you have a maximum ring size the derailleur will accomodate, newer mountain bike derailleurs are commonly 44 or 46, older ones are often 48. You can run a larger ring than this max but you will find when the curvature of the derailleur cage does not match the outer ring you will need to run the derailleur higher up than the recommended 1 - 2 mm and your shifting will suffer.
A less obvious side effect is that your chain will no longer be long enough so if you are goofy enough to run on the largest ring in the front and the largest cog in the back you will likely jam your chain.

It is all completely reasonable but you need to plan the whole thing out carefully. What I did to get around all the derailleur issues was buy some a couple new old stock Deore XT front derailleurs from the late 90's when it was common for mountain bikes to have a 48 tooth large ring. (the cassettes back then were usually 13 - 32)
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Old 04-03-07, 09:26 AM   #5
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+1 on switching the cassette first. I'm not sure whether you can put road size rings on a MTB crankset.
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Old 04-03-07, 09:39 AM   #6
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If you want to change the chainring you have to look at the clearance on the frame - my mtb had an issue with that. My lbs didn't want to put anything significantly larger on because they said it would be too big of a difference (even though I'm constantly on the big ring on that bike and just get fustrated!).
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Old 04-03-07, 09:44 AM   #7
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cassette swap is the way to go.
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Old 04-03-07, 10:06 AM   #8
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In most cases on an MTB you can get the old style 26/36/48 to work with the front derailleur. This is still one of the Hybred gear choices in the Shimano Deore and LX lineup. Do some research, but it may even fit your current bottom bracket. The road crankset will require a road front derailleur which will probably not work with your present shifters.
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Old 04-03-07, 10:08 AM   #9
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Quote:
Originally Posted by superslomo
+1 on switching the cassette first. I'm not sure whether you can put road size rings on a MTB crankset.
You can't, the road big and middle rings have a 130mm bolt circle and the MTB is either 104 or 110.
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Old 04-03-07, 02:26 PM   #10
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Just what cassette/FW is currently on the bike? If it's already an 11-xx, going to another 11-xx won't help!

IF you are going to use this as a commuter, you'll probably want some "slick" type tires. These are also smaller dia. then your typical MB tires, which will gear you down even more.
I'm running a 26X1.95" semi-slick on the rear, instead of a smaller tire just for that reason on my 46/13 high gear.
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Old 04-14-07, 09:24 AM   #11
Chris in WCVA
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Thanks for all your advice. I lost track of this thread, so I just got a chance to look at it. I have an 11-30 cassette, is there anything smaller?

I might check to see if a 48 top ring is possible.

I don't know though, I like the grunt of the 24 on huge hills. Hey! Maybe you guys could talk the DW into getting me road bike this Christmas!!!!
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Old 04-14-07, 09:27 AM   #12
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Quote:
Originally Posted by Chris in WCVA
Thanks for all your advice. I lost track of this thread, so I just got a chance to look at it. I have an 11-30 cassette, is there anything smaller?

I might check to see if a 48 top ring is possible.

I don't know though, I like the grunt of the 24 on huge hills. Hey! Maybe you guys could talk the DW into getting me road bike this Christmas!!!!
Actually, you can trash your knees pulling hills in a "Grunt Gear", you're far better off spinning up the hill in a lower gear and keeping the cadence high. It's also better for your circulation in the legs as muscular action assists in pumping the blood back out of your legs, flushing CO2 and Lactic Acid out of the muscles more efficiently.
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Old 04-14-07, 09:54 AM   #13
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Quote:
Originally Posted by Chris in WCVA
Maybe you guys could talk the DW into getting me road bike this Christmas!!!!
There's no hurry, but there's a lot to be gained IMO from adding a road bike, if you can swing it. Personally, I went this route, slightly modified -- bought my wife an MTB, and she let me use her steel road bike which -- after a stem upgrade and a few tweaks -- fits me very well. (She doesn't like to ride in traffic anymore.)

I love the road bike speed and glide as much as I do riding my MTBs in the woods. For a Clyde there's something effortless about riding road bikes on the flats at speed -- the first 11 mph are free -- after that then it's you against as much wind resistance as you want to generate.

Although still plenty of work, hills on a 21-lb road bike go by much more quickly.

You also have the option of swapping in/out slicks if you want to go that route.

I remember that Tom Stormcrowe when he first came here was riding MTBs, until he discovered the joys of road biking as well.

Overall, although hills will still give us Clydes all the challenge our hearts desire, I think road biking has much to offer us.
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Old 04-14-07, 10:03 AM   #14
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It was actually more a rediscovery.....I started out on a roadie many years ago and during the hiatus, got far too big for a road bike. I much prefer roadies though and keep a mountain bike around for the occasional trail ride or bad weather. The Mountain bike I have though will never go anywhere other than my possession, as It was gift from my grandfather after he found out I was resuming riding.
Quote:
Originally Posted by rideorglide
There's no hurry, but there's a lot to be gained IMO from adding a road bike, if you can swing it. Personally, I went this route, slightly modified -- bought my wife an MTB, and she let me use her steel road bike which -- after a stem upgrade and a few tweaks -- fits me very well. (She doesn't like to ride in traffic anymore.)

I love the road bike speed and glide as much as I do riding my MTBs in the woods. For a Clyde there's something effortless about riding road bikes on the flats at speed -- the first 11 mph are free -- after that then it's you against as much wind resistance as you want to generate.

Although still plenty of work, hills on a 21-lb road bike go by much more quickly.

You also have the option of swapping in/out slicks if you want to go that route.

I remember that Tom Stormcrowe when he first came here was riding MTBs, until he discovered the joys of road biking as well.

Overall, although hills will still give us Clydes all the challenge our hearts desire, I think road biking has much to offer us.
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Old 04-15-07, 10:21 AM   #15
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I have a 48-38-28 new if your interested, it will work with minimal fdr adjustment. Then add high pressure slicks and you will be impressed.

PM me
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