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trying to dump weight... carbon or alum. crank?

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trying to dump weight... carbon or alum. crank?

Old 12-15-20, 03:26 AM
  #1  
rajbcpa
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trying to dump weight... carbon or alum. crank?

ok - purchased a kinda heavy mountain bike - bridgestone. ....considering [1] carbon crank, [2] carbon fork, [3] carbon wheels and carbon handelbars to save weight...


looking at cranks, a shimano [ultegra] weighs 3 pounds. the campy aluminum alloy crank [centaur] is 1.8 pounds...

I thought this was a misprint. the carbon crank should weigh less; right?
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Old 12-15-20, 03:47 AM
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The difference in weight between carbon and alloy isn't that great. I think carbon has more benefits than just weight which has lead to its widespread adoption. However, you realise that Ultegra and Centaur cranks are not going to fit on a mountain bike? What do you call 'kinda heavy'. Mountain bikes are generally heavier than road bikes and it probably isn't a such a great issue if it's a good bike. For example, a friend of mine has just bought a Voodoo mountain bike (Aizan, I think) which weighs over 15kg but gets very good reviews. You could spend a small fortune on carbon bits and pieces and make very little difference to the overall weight.

Last edited by jgwilliams; 12-15-20 at 03:54 AM. Reason: Fix bike name
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Old 12-15-20, 04:23 AM
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Putting issues with installing road cranks on a mountain bike aside, the heaviest Ultegra R8000 crankset weighs 690grams. That is just over 1.5 pounds, so the 3 pound weight was certainly a misprint..
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Old 12-15-20, 05:22 AM
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If you want light, you purchased the wrong bike. Carbon components will not make enough difference for the money spent. Just my opinion.

Last edited by delbiker1; 12-15-20 at 05:23 AM. Reason: add more info
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Old 12-15-20, 05:32 AM
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Aren’t all Shimano cranksets forged aluminum alloy?
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Old 12-15-20, 06:19 AM
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Carbon wheels on a 26" rim brake will be difficult to find. What's the weight of the bike now and what weight do you want to hit?
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Old 12-15-20, 06:52 AM
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If you really want to save weight, see if you can work in a 1x system. That'll remove a shifter, a derailleur and one or two chainrings. It sounds like you're approaching this problem from the backward direction, which will usually result in lower performance and more cost. That's not the smart way to go. Ride your current bike and begin to save your pennies. Skip beer once in a while and throw the money into a jar. You'll be surprised how much you can save in no time.

There are many videos of how entire full squish carbon MTBs can be built from AliExpress frames and parts carefully specified and purchased over time. All for well under $2000. Start saving.
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Old 12-15-20, 07:07 AM
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If you have got one of Grant Petersen's MB-0, XO-1, or other lower number models you may have something worth attempting but if not I would agree with the above cautions.
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Old 12-15-20, 07:09 AM
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Originally Posted by rajbcpa View Post
ok - purchased a kinda heavy mountain bike - bridgestone. ....considering [1] carbon crank, [2] carbon fork, [3] carbon wheels and carbon handelbars to save weight...


looking at cranks, a shimano [ultegra] weighs 3 pounds. the campy aluminum alloy crank [centaur] is 1.8 pounds...

I thought this was a misprint. the carbon crank should weigh less; right?

You can throw a whole lot of money at that bike and still not get it appreciably lighter. Tires are a place where weight can easily and inexpensively be saved. Rims are another, but don't just assume that carbon will weigh less than aluminum. As someone else mentioned finding a good carbon 26" wheel with rim brakes may be a challenge. I'll bet there are some bargains on good quality 26 inch rim brake wheels to be had. The weight difference between good quality carbon bars and high quality aluminum bars is generally negligible. Road cranks on a mountain bike may not work. With a threaded English bottom bracket, you can adjust the chainline, but the with the wider MTB stays, your inner ring may not clear it. Bottom line in my opinion is that you can do a build with top quality aluminum components and be in a better place than you would by going with carbon.
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Old 12-15-20, 08:29 AM
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My greatest weight savings on both mountain bikes and road bikes has been belly fat. Now we’re talking kilos, not grams.
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Old 12-15-20, 08:35 AM
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Originally Posted by jgwilliams View Post
The difference in weight between carbon and alloy isn't that great. I think carbon has more benefits than just weight which has lead to its widespread adoption. However, you realise that Ultegra and Centaur cranks are not going to fit on a mountain bike? What do you call 'kinda heavy'. Mountain bikes are generally heavier than road bikes and it probably isn't a such a great issue if it's a good bike. For example, a friend of mine has just bought a Voodoo mountain bike (Aizan, I think) which weighs over 15kg but gets very good reviews. You could spend a small fortune on carbon bits and pieces and make very little difference to the overall weight.
Bicycle weight and carbon fiber are overrated.
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Old 12-15-20, 08:38 AM
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So how did those carbon wheels on your wife’s e-bike work out?

John
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Old 12-15-20, 09:58 AM
  #13  
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You can't really boil it down to simply carbon, aluminum, titanium or other. Nor can you say this component over the other component. You have to know the weight of what you are replacing and compare it to the weight of what you are getting.

Generally on a road bike wheels will allow you to shed weight quick. But some carbon wheels are as much weight as good alloy wheels. Also, a complete change of the group set can shed some weight too if you go from mid tier to high tier group.

For your mountain bike I don't know how begin to consider wheels. As if you actually ride it in the conditions it's made for, then you want strong wheels. Alloy or carbon.... I wait to see what other say for wheel choice on a mountain bike for riding mountain bike conditions.

As for those Ultegra cranks, where did you get that number? On Shimano's website the current Ultegra FC-R8000 shows as 690g (1.52 lbs) for the 53/39 ring version.

Also, Ultegra is a road bike group. Might fit your mountain bike, but might not. You should be looking at mountain bike components. Though if this is an old bike, then probably a lot may crossover.

If you are trying to make a mountain bike a road bike. STOP. DON"T. It'll never be light enough. At most just put some slicks on it and ride it till you get in decent shape. Then take the money you saved by not spending on upgrades and get a new and lighter bike. Whether that is a road bike or mountain bike or other type.
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Old 12-15-20, 11:29 AM
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Originally Posted by Amt0571 View Post
Bicycle weight and carbon fiber are overrated.
when dealing with 30 year old Bridgstones it is
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Old 12-15-20, 11:31 AM
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Shimano doesn't make carbon cranks. They are hollow aluminum. A really light carbon crank may weigh around 600 grams and a cheap shimano grx crank just over 800. It takes a lot of money to save less than half a pound.

A modestly priced Campy chorus carbon crank weighs just over 700. I wanted lower gearing than a 48/32, so I sacrificed about 100 grams and bought a $145 grx crank to get a 46/30. I'd rather have the right gearing than a 100 gram lighter bike.
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Old 12-15-20, 11:33 AM
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Originally Posted by rajbcpa View Post
ok - purchased a kinda heavy mountain bike - bridgestone. .
I think we could help you more if you stated what this bike is going to be used for. Road, dirt, commuting, etc. Starting with an old, heavy, probably non-high end frame and pouring lots of money into lightweight parts that will just make a heavy bike less heavy is a good way to throw money away. You may as well just buy a new bike fit for your use. Not a criticism but do you have some good knowledge of what parts will work with your bike? Just give us some idea of what you are trying to create and we could probably give you some better help.
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Old 12-15-20, 11:37 AM
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You could lighten the whole system by about 5 pounds in a couple weeks with a low-carb diet.
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Originally Posted by bragi "However, it's never a good idea to overgeneralize."
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Old 12-15-20, 11:44 AM
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Unless you have steel cranks now, the weight you can save by swapping crankset is pretty minimal.

Easy/effective weight loss items: Tires, tubes, wheels
Less easy/effective: handlebar, stem, seatpost, saddle, pedals
Difficult enough mods for minimal losses such that it's generally not worth the bother: Cranks, frame, fork, derailleurs

There are also functional and safety reasons why you should ignore a bit of extra weight in some cases. For instance, there are/were a few manufacturers making ultra-light caliper brakes for road bikes, but these brakes were almost universally considered to be inferior brakes, even if they did save 50g. ANother example is titanium bottom bracket spindles (not really a thing you can upgrade on modern bikes)... great if you only ever ride your bike to the scale to weigh it, but flexy and fragile under normal use.

One other thing is that your Bridgestone is a few generations old - it is probably a great bike, but it won't be compatible with many modern parts.
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Old 12-15-20, 11:46 AM
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Originally Posted by Germany_chris View Post
when dealing with 30 year old Bridgstones it is
Well, to make it clearer: weight is overrated up to a certain point. Carbon fiber is always overrated.
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Old 12-15-20, 12:47 PM
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Originally Posted by Amt0571 View Post
Well, to make it clearer: weight is overrated up to a certain point. Carbon fiber is always overrated.
Since fat is a hydrocarbon, does burnt fat count as carbon fiber?
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Old 12-15-20, 02:26 PM
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Originally Posted by reconnaissance View Post
Since fat is a hydrocarbon, does burnt fat count as carbon fiber?
No. IT's more similar to carrying a water bottle full of melted butter as an energy drink.
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Old 12-15-20, 03:00 PM
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Get a THM Clavicula SE:


Only 293 grams! For only $1300.
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Old 12-15-20, 03:24 PM
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Originally Posted by Doohickie View Post
You could lighten the whole system by about 5 pounds in a couple weeks with a low-carb diet.
Yeah, but that comes back
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Old 12-15-20, 05:28 PM
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Originally Posted by Amt0571 View Post
Bicycle weight and carbon fiber are overrated.
On first read I thought you said, "Body weight and soluble fiber" are overrated! lol

For the OP, the best place to lose weight is in the wheels. Not only static weight but rotating weight. A pound or more saved in the wheels will be really noticeable. (Or you could try drillium).

Last edited by bikemeister; 12-15-20 at 05:32 PM.
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Old 12-16-20, 07:56 AM
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Originally Posted by Darth Lefty View Post
Yeah, but that comes back
Hush.
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Originally Posted by bragi "However, it's never a good idea to overgeneralize."
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