Bicycle Mechanics - Changing the chainring on a Trek 5200
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09-21-05, 03:33 PM
Does anyone know what is needed to change a double 52/39 chainring to something like a 52/42/30 triple on a stock Trek 5200? All components are Shimano Ultegra 9 speed. Do I need to only change the front ring? Will this index properly, or do I need to change the whole drive train - deraillers, brackets, rear cassette, chain? What about the shifters?
09-21-05, 03:55 PM
OK... Your current levers, chain, and rear cassette will work. Everything else should change. The double rear derailer won't wrap enough for a triple, the bottom bracket will have to be changed along with the crankset to go to a triple. Also the front derailer will not handle the step to the smallest ring.
A better option might be a compact double. Change the crankset and you're done.
Also, before you get the requisit crap posts about getting stronger or not needing a triple. JUST IGNORE THEM... You're the ultimate judge for what you want/need. Don't give in to the racer mentality that seems to be pretty widespread around here. There is no bigger waste than having a bike you don't enjoy riding.
Many cyclist post questions about converting triple drivetrains to double. Maybe you can find someone to trade components with.
09-21-05, 09:27 PM
Why? It adds weight and may overly complicate a careful balance of this machine. Adding a grannie to a light 5200 seems to defeat its purpose.
How old is your bike? I am currently changing out a triple for a double. I will have a 105 FD (my Lemond Buenos Aires was mostly Ultegra except for the BB and FD), 105 BB and Ultegra Crank. I was planning on keeping my rear, but I don't need the longer cage. I have purchased all the equipment needed for the change except the RD. I have about 4500 miles on my bike, how about yours? The problem I foresee is can you do without your bike while we exchange parts? I can't. If we agree on a price, I could send you everything except for the RD, you could send me the RD, I could change out the RD and then send you my RD. What do you think?
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Why? It adds weight and may overly complicate a careful balance of this machine. Adding a grannie to a light 5200 seems to defeat its purpose.Not if it gets ya up the friggin hill and prevents it from becoming a garage ornament... :rolleyes: Trek even marketed them as triples,so what's the real beef?
09-22-05, 11:05 AM
No beef ... just a comment
09-22-05, 04:06 PM
Thanks to all for the input. I don't actually own this bike yet but am shopping. I also like the Giant TCR limited but if I put a triple on this I'd probably geat beat up by some racer. I toyed with going with the double, but I live in Colorado and my 46 year old knees need the lower gears. I'm looking into the compact double option. Can someone give me a quick explanation of this? Is it more teeth on a smaller diameter ring?
Thanks to all for the input. I don't actually own this bike yet but am shopping. I also like the Giant TCR limited but if I put a triple on this I'd probably geat beat up by some racer. I toyed with going with the double, but I live in Colorado and my 46 year old knees need the lower gears. I'm looking into the compact double option. Can someone give me a quick explanation of this? Is it more teeth on a smaller diameter ring? I don't think that is possible. Short story is the 'compact' crank uses a 110BCD so the small ring can be as small as a 33t,but they usually come with a 34/50t set.
09-22-05, 05:19 PM
if I put a triple on this I'd probably get beat up by some racer.
Well, Roberto Heras used a triple on his way to winning the Vuelta a couple of year ago and I don't remember any reports of the other racers beating him up.
Why the reluctance to add a triple? The weight penalty is negligible and the complexity issue is absurd. If you don't need the granny, don't shift into it. It's that simple.
If I lived in the Rocky Mountains I'd definitely want a triple on one bike and probably a compact double on another. What kind of gearing you need depends mostly on where you ride.
09-23-05, 07:55 AM
A compact double chainring is usually 50/34. If you combine that with a 12/25 rear cassette, you lose one gear of the hill climbing range of a 52/42/30 triple with a 12/25 rear cassette. On the upper end, the compact is a little shorter than a 52/12 combo but are you really going to be "sitting in" a 40 mph peloton anyway? The only place you'll notice is on some screaming descents.
Bottom line is, using the same cassette, you lose one low gear and one high gear that you would have with the triple*. Otherwise, you can go from 12/25 rear to 12/27 and guess what? You don't lose any low gears. You are still just a little shorter on your top gear but you won't miss it. *This is an over simplification but close.
Compacts aren't perfect. You'll still have fewer gear ratios to work with so you sometimes wish for a gear that's just a little more or less that you won't have. Also, some compacts benefit from having a chain watcher on the downtube because they are more prone to dropping the chain inside than standard doubles.
Play around with the gear calculator on Sheldon Browns site and you can see exactly what the differences are. www.sheldonbrown.com
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