making cranks lighter?
 

Hey so I have found this compact double that weighs 750grams with steel rings.

Currently i have an old crankset with rusty rings so need to replace.

Would I be better off buying some alluminium chainrings or swapling the crankset out.

I dont have the weight for my cranks but they are alluminium.

So in essense will I save more weight with the rings or the crank arms?

How much does a 52/42 double normally weigh?

You would save more in the arms than the chainrings. Are you getting ready for the Tour? Roger

i have a job as a cycle delivery and wanna get my bike as light as possible as i ride 4 hours a day.

Without knowing what specific crankset models you're talking about, it's impossible to give you a weight comparison. Sheldon Brown's web site has a page that lists weights for various components, including cranksets and chainrings, so you can make some comparisons yourself:

https://www.sheldonbrown.com/rinard/weights.htm

Moving past the comparison of one unknown crankset to another... Swapping your steel chainrings for aluminum ones would save you a few grams.

If you swap cranksets, be aware that you may also have to swap out the bottom bracket because the 'new' crankset might be designed for a different spindle length than your previous one.

Because the bike is in commercial duty, I'd keep the steel chain rings and avoid becoming too weight weenish.

Brad

<Nothing weighs Less , than a part not installed>



:rolleyes:

If you are riding everyday for work, you may need a more durable chainring. The Aluminum Chanirings wear out sooner. The teeth will get hooks on them. You might wear out the steel ones too. But, it will take longer.

Add more weight of a very good lock so it has less of a chance of being stolen ..

If your current crank has steel chainrings there is a very good possibility they are riveted on, not bolted. In that case you can't replace them and would need a complete new crank.

+1

There is not as much difference in mass between aluminum and steel rings as the material density would indicate, because there is more aluminum by volume in the aluminum rings than there is steel in the steel rings.

One word: drillium.

Like this?

https://www.bttbike.com/foto/o/14/98...3-img_3959.jpg

There was a crank made in Europe, aluminum , bored lengthways to have it like a double barreled shotgun..

Expensive, yes, but lighter...


now the thing is make it out of carbon fiber.. but still not cheap.





.....

But consider its 1 expensive, like what whole bikes cost,

And 2 may not be rugged enough for utility bike use daily.

Light, cheap, durable, you can only have 2 ..




:rolleyes:

I'm not sure if that is true.

I've seen plenty of worn steel chainrings. I think many of the steel rings are made with very cheap steel.

Not all aluminum is the same. 7xxx series rings will last longer than 6061 rings.

Anyway, get a good 7xxx series ring, perhaps with ceramic coating, and it will last a good long time. TAKE CARE OF YOUR CHAINS.

As far as cranks, Shimano has gone to "Hollowtech", essentially making them as big tubes. Other companies have made greater use of Carbon Fiber. Anyway, there are lighter cranksets and bottom brackets available. :)

just for fun, i weighed a STEEL chain ring, 50 tooth, 110 BCD... 228 grams, and it's a fairly light one...

weighed an aluminum chain ring, 52 tooth, 110 bcd... 69 grams.

your weight savings if you swap out both chain rings? in the neighborhood of 1/2 lb. of ROTATING MASS, that must be accelerated EVERY TIME YOU PEDAL YOUR BIKE...

get the lighter chain rings....

and look into getting lighter pedals, wheels, and tires when you are able... rotating mass, you know... you will be glad you did.... unless you like working harder than you need to.

upgrading to a hollowtech II crank set will shed even more weight from your bike, btw... up to a POUND or more... the steel bottom bracket assemblies are HEAVY... Hollowtech II uses a hollow aluminum spindle, and aluminum cups... light, inexpensive, and easy to replace when worn.... no special puller needed, just the HT II type wrench.... the shimano chain rings are of high quality, and will last quite a while if you keep your chain cleaned, and use decent chain lube regularly.

as to crank ARMS... if your crank set has aluminum arms already, the weight savings will be minimal when swapping to another aluminum armed crank set with steel chain rings... MOST of the weight is in the steel RINGS.

Tell/show us more about this bike. Aluminum chainrings are a good start (I don't use steel ones on anything), but there are probably even bigger opportunities elsewhere.

How much do YOU weigh? :lol:

Ya know, I am going to have to agree with this. 7xxx series chainrings are harder than some steels. Some stainless steel is soft. Just because they are steel doesn't mean longer life unless you know what they are made from.

7075-T6 aluminum Might offer some durability approaching that of steel, but its expensive.

what is the opening bid.. what is your budget commitment to this?

not a gig that pays big bucks , unless what you are delivering is illicit..

..

6061 vs, 7075... the 7075 will have improved wear characteristics, but will fatigue crack sooner...this makes 7075 better for chain rings, but worse for frames...the extra copper is added to the alloy to reduce cracking.

Compare 6061-T6 aluminum to 7075-T6 aluminum

I put 18,000 miles on a Praxis aluminum chainring before it started to show any signs of actual wear-- that is, a handful of chipped/folded teeth.

Aluminum rings are acceptably cheap, and the OP would benefit from the weight reduction.

While we are talking about cranks, it occurs to me that low end bottom brackets can be very heavy and the bottom bracket is a good place to save significant weight.

Weight is one of the last things you should be concerned about, at least when you are talking about grams or ounces, rather than multiple lbs./kgs. Remember that your bike weight includes you, and that whatever percentage you save of the total affects only rolling resistance and inertia. Check the saddle position and other fit aspects. Make sure your tires are large enough to absorb shock and protect from road hazards (nothing slows you more than a flat) but smooth rolling, and of course properly inflated. Use cleated shoes (walkable/mtb style) or toe clips and shoes with firm soles. Stay hydrated and fueled.

LOLing at posts telling the OP to stay hydrated, lose weight, inflate his tires, use a lock, etc.

He is a courier who rides 4 hours/day. It is safe to assume that he is not overweight, knows to stay hydrated, put air in his tires and knows all about locking his bike. This is completely apart from the fact that he didn't ask about any of that.

Maybe you guys could suggest a camera for his next vacation or some good jazz clubs to chill after he gets off work. :lol:


-Tim-

couriers hang out at coffee shops only