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 Post subject: Bottom Bracket Drag
PostPosted: Thu Mar 16, 2017 9:14 pm 
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Joined: Wed Feb 20, 2013 7:37 pm
Posts: 136
While putting on a new chain I noticed the stock bottom bracket in my '16 Evo HiMod had a lot of drag. Preload looked good on the wave washer but when I spun the crank with no chain it would only go around 2 times max! So I installed a BBInfinite unit and now the crank spins almost as good as a wheel. I didn't think it'd be noticeable when riding but it definitely was.

My question is what impact does excessive BB drag have on a crank based power meter (power2max)? It seems like it wouldn't have an effect on the readings (meaning for a certain effort the reading would be the same as before), you'd just get more speed for a given power. Is that correct? Thanks!


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 Post subject: Re: Bottom Bracket Drag
PostPosted: Fri Mar 17, 2017 12:10 am 
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Joined: Thu Jul 19, 2012 6:09 pm
Posts: 1109
Location: Loveland, CO
Your thinking is correct. It doesn't increase your power output but less friction should equal to more speed, albeit the difference is probably too small to measure outside of a laboratory.

I recently had a BB go bad on me due to water intrusion. I suspect the dust seals are the culprit. I posted a comment in another BB friction thread. I'm now using another brand of BB that has higher friction. I'm hoping that more friction would equal to higher degree of durability.

I'm curious as to how the BB Infinite would hold up over time.


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 Post subject: Re: Bottom Bracket Drag
Posted: Fri Mar 17, 2017 12:10 am 


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 Post subject: Re: Bottom Bracket Drag
PostPosted: Fri Mar 17, 2017 12:13 am 
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Joined: Thu Nov 24, 2016 10:32 pm
Posts: 78
Hawk Racing bearings are phenomenal. Spin with very little drag and are maintainence free.


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 Post subject: Re: Bottom Bracket Drag
PostPosted: Fri Mar 17, 2017 1:27 am 
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Joined: Sat May 26, 2012 11:26 pm
Posts: 981
I have a s works tarmac with the OSBB bearings with Wheels MF BB30 bearings which spin forever without a chain and has lasted for well over 10,00k so far. Whereas my SRAM PF30 on my evo spins a few revolutions and stops. I similarly wonder about the benefits of a different BB but its quiet and not crunchy and hasn't changed from new so i wonder wether it is worth the bother - I think it is not.

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Evo 5.02kg SL3 6.77 Slice RS 8.89 viewtopic.php?f=10&t=110579" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;


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 Post subject: Re: Bottom Bracket Drag
PostPosted: Fri Mar 17, 2017 2:37 am 
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Joined: Fri Sep 25, 2015 3:12 pm
Posts: 136
Ltoddokc wrote:
While putting on a new chain I noticed the stock bottom bracket in my '16 Evo HiMod had a lot of drag. Preload looked good on the wave washer but when I spun the crank with no chain it would only go around 2 times max! So I installed a BBInfinite unit and now the crank spins almost as good as a wheel. I didn't think it'd be noticeable when riding but it definitely was.

My question is what impact does excessive BB drag have on a crank based power meter (power2max)? It seems like it wouldn't have an effect on the readings (meaning for a certain effort the reading would be the same as before), you'd just get more speed for a given power. Is that correct? Thanks!


drag doesnt grow. if it takes - say , a fraction of a newton / the gentlest of fingertip pressure to get the cranks spinning , then thats all thats required to overcome. the difference between an unloaded (no chain) smooth setup and your draggy setup is that... its not going to multiply when connected to the drivetrain and going down the road at speeds.

thats why ceramic bearings, or ooing and aahing over freely spinning hubs is silly. it doesnt really matter.

your crank registers torque when it starts to deform from resistance of the chain pulling it back. the draggy bb adds negligible resistance to the system.

its effect on measured power and speed is virtually 0.


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 Post subject: Re: Bottom Bracket Drag
PostPosted: Fri Mar 17, 2017 3:03 am 
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Joined: Thu Jul 19, 2012 6:09 pm
Posts: 1109
Location: Loveland, CO
NiFTY wrote:
I have a s works tarmac with the OSBB bearings with Wheels MF BB30 bearings which spin forever without a chain and has lasted for well over 10,00k so far. Whereas my SRAM PF30 on my evo spins a few revolutions and stops. I similarly wonder about the benefits of a different BB but its quiet and not crunchy and hasn't changed from new so i wonder wether it is worth the bother - I think it is not.


With no offense but 10,000km is nothing. I rode 18,000km last year. I expect my BB to last 100,000km or more. The wheel bearings on my car could last 300,000km.


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 Post subject: Re: Bottom Bracket Drag
PostPosted: Fri Mar 17, 2017 10:32 am 
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Joined: Sat May 26, 2012 11:26 pm
Posts: 981
No offense taken. Never said it was exemplary. Merely meant it had decent seals, and that lack of seals were not the reason it spun well. An unsealed Bb would have shat itself by now.

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 Post subject: Re: Bottom Bracket Drag
PostPosted: Fri Mar 17, 2017 10:23 pm 
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Joined: Thu Sep 05, 2013 3:29 pm
Posts: 419
Ltoddokc wrote:
\So I installed a BBInfinite unit and now the crank spins almost as good as a wheel.\


You can find some good info from Friction Facts reports on BB efficiency. From memory, the swapping from worst to best would save you somewhere in the 3-5ish watt neighborhood, but again that would be an extreme exambple.

Slightly off topic, but relating to the BBInfinite system: What keeps that BB unit from working its way back out of your frame, either due to pedaling loads, or an impact like the bike falling onto its left side? I loved the old shimano one piece cartridge BBs, so I see the appeal of their construction method, but, unlike the Shimanos, the BBInfinite isn't threaded in. From the pics I have seen, it looks like it is solely a bit of loctite, and if people have individual PF30 cups working their way out how is this any better, particularly in the case of a poorly toleranced frame?


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 Post subject: Re: Bottom Bracket Drag
PostPosted: Fri Mar 17, 2017 11:14 pm 
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Joined: Wed Feb 20, 2013 7:37 pm
Posts: 136
TheKaiser wrote:
Ltoddokc wrote:
\So I installed a BBInfinite unit and now the crank spins almost as good as a wheel.\


You can find some good info from Friction Facts reports on BB efficiency. From memory, the swapping from worst to best would save you somewhere in the 3-5ish watt neighborhood, but again that would be an extreme exambple.

Slightly off topic, but relating to the BBInfinite system: What keeps that BB unit from working its way back out of your frame, either due to pedaling loads, or an impact like the bike falling onto its left side? I loved the old shimano one piece cartridge BBs, so I see the appeal of their construction method, but, unlike the Shimanos, the BBInfinite isn't threaded in. From the pics I have seen, it looks like it is solely a bit of loctite, and if people have individual PF30 cups working their way out how is this any better, particularly in the case of a poorly toleranced frame?


You're right, it's just the retaining compound they supply and friction. But the fit was VERY tight. Definitely heard the creaking/popping they mention in the manual. It was oddly reassuring to know it's in there that tight.


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 Post subject: Re: Bottom Bracket Drag
PostPosted: Fri Mar 17, 2017 11:28 pm 
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Joined: Tue Apr 19, 2011 10:07 pm
Posts: 129
I agree, Hawk Racing Bearings are now the only bearings I use!! Spin forever....almost

MyM3Coupe wrote:
Hawk Racing bearings are phenomenal. Spin with very little drag and are maintainence free.

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 Post subject: Re: Bottom Bracket Drag
PostPosted: Wed Oct 18, 2017 12:32 am 
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Joined: Wed Sep 20, 2006 1:03 am
Posts: 507
Location: Madison, WI USA
gewichtweenie wrote:
drag doesnt grow. if it takes - say , a fraction of a newton / the gentlest of fingertip pressure to get the cranks spinning , then thats all thats required to overcome. the difference between an unloaded (no chain) smooth setup and your draggy setup is that... its not going to multiply when connected to the drivetrain and going down the road at speeds.

That's not true, though your overall point is valid. For a given load, bearing drag increases linearly with speed. The bearing drag from your hubs on a 40-mph descent is twice as much as the hub drag when you're rolling along at 20 mph on the flat.

gewichtweenie wrote:
thats why ceramic bearings, or ooing and aahing over freely spinning hubs is silly. it doesnt really matter.

You're right that ceramic bearings and hubs that spin easily on the workbench don't mean much, but it's not for the reason you stated. Bearing drag is a very small percentage of overall drag; it's almost nothing. Two times almost nothing is still almost nothing.

Also--and this is a bigger deal than many realize--bearing drag on the workbench is significantly less than it is on the bike. That's because bearing drag is not just a function of RPM, but also a function of load. Spinning a wheel in a truing stand doesn't tell you very much about the real-world bearing drag because the bearing is unloaded. You can get a feel for the drag of the seals and grease, but not so much the rolling elements of the bearing.

Everyone loves the feel of old Campy cup-and-cone hubs. They feel spinny and low-drag when you turn the axles with your fingers or spin the wheel in your hands, so people think that translates to low drag on the road. It' doesn't. One drawback of cup-and-cone bearings is that the bearings take a load that's primarily radial, but the bearings themselves contact the cups/cones at 45 degrees to the load. If a cartridge-bearing front hub takes 60 pounds of load, each of the two bearings deals with a vertical load of 30 pounds. But on a Campy cup-and-cone front hub, that 45-degree contact angle means that, to support a 60-pound load, each set of bearings takes a load of 42 pounds, which is about 1.4 times as much as the cartridge bearing hub. As a result, the cup-and-cone hub has about 1.4 times the bearing drag of an equivalent cartridge bearing hub.

In reality, it's not quite so simple...cup-and-cone bearings often have lower seal drag than cartridge bearings, so that helps a bit (a tiny bit). But the upshot is that the drag of an unloaded bearing is a pretty terrible predictor of how much drag that bearing creates under load.

gewichtweenie wrote:
your crank registers torque when it starts to deform from resistance of the chain pulling it back. the draggy bb adds negligible resistance to the system.

its effect on measured power and speed is virtually 0.

Well, with a crank-spider-based power meter, the effect of bottom bracket bearing drag on its reading isn't virtually zero; it's exactly zero. The bottom bracket bearings are "downstream" of the strain gages, and they really don't care whether the resistance they measure comes from mass*gravity, wind drag or bearing drag. But you're right: the difference in drag between any two bearings is so small that it's within the margin of error of any power meter on the market. You literally can't measure the difference with a power meter.

Again, your overall point is right: bearing drag is very low, and bearings don't have a measurable effect on power readings whether the meter is upstream or downstream of the BB. But it's not true that "[bearing] drag doesn't grow." It does, but it increases from a really tiny amount to a tiny amount.


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 Post subject: Re: Bottom Bracket Drag
Posted: Wed Oct 18, 2017 12:32 am 


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