Weight vs efficiency

Discuss light weight issues concerning mountain bikes & parts.

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hubdekkers
Posts: 1
Joined: Thu Apr 19, 2018 5:49 am

by hubdekkers

Hi Everyone!

This is my first post :). Found myself the last months being concious about the weight of my bike, trying to reduce it. The forum has been of use before, so thanks for the helpful information.

Thinking of replacing my bottom bracket. At the moment I'm running a pressfit XTR one at 55 grams. I am looking at a torqtite enduro one with ceramic bearings. That one should be way more efficient and durable, but also weighs in at 102 grams. So, is the efficiency (and potential watt gain) worth 55 grams?

Reason for changing is that I'm thinking about replacing my XTR 9020 cranks (with stages powermeter) with the new Rotor 2inpower dm mtb. These are 30mm instead of the 24mm shimano. Also these come with a weight penalty of about 70 grams. So the debate I have with myself, is the additional insight in power (and change to Q rings) worth the 70 grams weight penalty.

Any advice and thoughts are much appreciated!

mattr
Posts: 3477
Joined: Fri May 25, 2007 6:43 pm
Location: The Grim North.

by mattr

Not really.
The difference between good steel bearings and any ceramic bearings, in real use, is miniscule.

Also, bear in mind that the XTR cranks are pretty much the benchmark as far as all round performance goes. Anything else will have some sort of compromise somewhere. Weight, durability, stiffness, ergonomics, cost and so on..........

by Weenie


pdlpsher1
Posts: 1480
Joined: Thu Jul 19, 2012 6:09 pm
Location: CO

by pdlpsher1

Watch the Hambini videos on bearings. He will teach you a lot and why you should stay away from Enduro and ceramic bearings.


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mattr
Posts: 3477
Joined: Fri May 25, 2007 6:43 pm
Location: The Grim North.

by mattr

And TBH, there are FAR more effective ways to save weight (and watts) than bottom brackets.

drider85
Posts: 183
Joined: Fri Apr 13, 2007 4:53 pm

by drider85

I think to his point would a "1 watt" saving in BB rolling resistance be more beneficial than a 125g weight gain? I think so. However as alluded to above not all bearings that say they are low drag really are. Just because it says ceramic doesn't make it faster. It's more about seals, grease and execution than specific material. Friction Facts had a article to that effect. Real world effect is hard to say as rider useage and conditions ridden in vary widely.

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LeDuke
Posts: 1128
Joined: Sun Oct 07, 2012 2:39 am
Location: Front Range, CO

by LeDuke

So, I have the Enduro TorqTite XD-15 angular contact BB on my Yeti ASRc. I didn't buy it because I wanted to reduce friction, but because I read a review from someone who took the seals off of it and rode it through the winter trying to kill the bearings, and failed. That was what sold me on it for my purposes (MTB).

I'd say that it's the best wear item purchase I've ever made. It's been on my bike since fall 2015. Once upon a time, when I was riding XTR cranks on a 26er Giant Anthem X, I was burning through 3 or more XTR BBs a year.

So, to me, that initial cost has been paid for and then some. I've opened it up and regreased it a couple of times, but it still spins incredibly smoothly.

by Weenie


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