Mountain Bike Reviews Forum banner
1 - 18 of 18 Posts

·
Registered
Joined
·
3,931 Posts
Discussion Starter · #1 ·
To minimize the torque on the EBB you want to have the line connecting the BB and the EBB axes to be as horizontal as possible. The position is determined by the length of the chain so you may have to use a half-link (ironic) to get to the ideal position. The ideal position for the BB, when looking from the drive side, is at 3 o'clock or 9 o'clock. At those points the torque on the EBB is zero regardless of the crank force. So stomp away.
 

·
Out spokin'
In cog? Neato!
Joined
·
16,365 Posts
pacman said:
To minimize the torque on the EBB you want to have the line connecting the BB and the EBB axes to be as horizontal as possible. The position is determined by the length of the chain so you may have to use a half-link (ironic) to get to the ideal position. The ideal position for the BB, when looking from the drive side, is at 3 o'clock or 9 o'clock. At those points the torque on the EBB is zero regardless of the crank force. So stomp away.
Shouldn't have to do that. If you do, that's too bad, but with a properly designed and constructed EBB frame, you shouldn't have to. That's one of the main reasons for utilizing an EBB in my opinion -- to allow chain tension adjustment anywhere within the EBB's range without headaches, creaking, slipping, half-links, etc.

When I change gears (for example between a 17t cog and a 20t cog or vice versa), I may have to add or remove a link, but I don't want to have to worry about the point to which my EBB is rotated. And thankfully with my frame I don't have to worry about it.

IMO all EBBs should be designed so that no one has to worry about this.

--Sparty
 

·
King Pin
Joined
·
1,247 Posts
EBB woes

I posted a coupla weeks ago concerning possible slippage with my EBB running fixie.

Andy Armstrong suggested I mark the EBB/BB. What a thought! I did it.

Despite a looser than previously adjusted chain after several rides...again and again, I'm having NO EBB slippage! Perhaps a bit of chain "stretch" (parenthesis on purpose!), but the marks I made concerning the EBB/BB have not changed, not one bit.

Maybe the parts just CONTINUE to "break in"? More noticeably whilst running fixed?

I dunno.....but it's not MY bb/EBB. Haven't noticed so much "chain loosening" on my SS.

Comments?

(My EBB is running at approx. one o'clock, to give me maximum ground clearance...)
 

·
Registered
Joined
·
1,163 Posts
xrmattaz said:
I
I dunno.....but it's not MY bb/EBB. Haven't noticed so much "chain loosening" on my SS.

Comments?

(My EBB is running at approx. one o'clock, to give me maximum ground clearance...)
I've had some chains that keep "stretching" all along, and others that break-in then hold for a long time. The KMC chains I ran were more prone to the continuous stretch while the SRAM PC-7x seem to break in then hold for a long time.
 

·
King Pin
Joined
·
1,247 Posts
I'm currently running the SRAM PC-7X on all my rigs.

"Stretch" has lessened.....yet several hundred miles later....on my fixie, still having to adjust the EBB. To a lesser agree, now.

Maybe them good chains "stretch" for many hundreds of miles??

I'm no longer worried.

Brandon said:
I've had some chains that keep "stretching" all along, and others that break-in then hold for a long time. The KMC chains I ran were more prone to the continuous stretch while the SRAM PC-7x seem to break in then hold for a long time.
 

·
Registered
Joined
·
2,842 Posts
pacman said:
The ideal position for the BB, when looking from the drive side, is at 3 o'clock or 9 o'clock. At those points the torque on the EBB is zero regardless of the crank force. So stomp away.
What about your weight acting down on the BB? Surely at these points, your weight acting downwards is greatest, and so by your theory, the EBB could rotate due to shock loads coming through your legs.
 

·
Registered
Joined
·
3,931 Posts
Discussion Starter · #7 ·
yes, but ..

What about your weight acting down on the BB? Surely at these points, your weight acting downwards is greatest, and so by your theory, the EBB could rotate due to shock loads coming through your legs.
When the cranks are vertical and the cyclist stands on the pedals there is a dead weight acting to turn the EBB, but with the small lever arm (1/4") the torque is small. My advice addresses the forces of cranking, especially relevant to the extremes of an all-out effort of body weight impulse applied to an ~180mm arm on a ~60mm ring, etc.
 

·
WAWE
Joined
·
1,437 Posts
xrmattaz said:
Andy Armstrong suggested I mark the EBB/BB. What a thought! I did it.

Despite a looser than previously adjusted chain after several rides...again and again, I'm having NO EBB slippage! Perhaps a bit of chain "stretch" (parenthesis on purpose!), but the marks I made concerning the EBB/BB have not changed, not one bit.
Good point - I have a feeling many people are mistaking wear for slipping EBB... the chain does get slacker as the miles go by!

Maybe the parts just CONTINUE to "break in"? More noticeably whilst running fixed?
Continued break-in == wear. :)
 

·
King Pin
Joined
·
1,247 Posts
Chain gets slacker....

And then stops.

I guess. After my last three rides, I have noticed no further slackage in the chain.

Finally settled in, I reckon.

aosty said:
Good point - I have a feeling many people are mistaking wear for slipping EBB... the chain does get slacker as the miles go by!

Continued break-in == wear. :)
 

·
Premium Member
Joined
·
48,238 Posts
pacman said:
When the cranks are vertical and the cyclist stands on the pedals there is a dead weight acting to turn the EBB, but with the small lever arm (1/4") the torque is small. My advice addresses the forces of cranking, especially relevant to the extremes of an all-out effort of body weight impulse applied to an ~180mm arm on a ~60mm ring, etc.
I don't buy it. Does not make sense at all. If the EBB is going to move it will move in whatever position it is set at.

With a properly designed and adjusted EBB slippage is just not an issue.

Care to test your theory by riding without tightening the EBB?
 

·
Registered
Joined
·
3,931 Posts
Discussion Starter · #11 ·
You can try this too

With a properly designed and adjusted EBB slippage is just not an issue.

OK, but how many EBB's are properly designed and adjusted? Do any of them account for the different direction of forces?

Care to test your theory by riding without tightening the EBB?

When the BB center is above the horizontal, torque pushes the EBB CCW.
When the BB center is below the horizontal, torque pushes the EBB CW.
At the crossover lines - 3 o'clock and 9 o'clock - the torque forces on the EBB are zero.
(9 o'clock is actually self centering) At 6 and 12 the torque peaks.
 

·
Premium Member
Joined
·
48,238 Posts
pacman said:
To minimize the torque on the EBB you want to have the line connecting the BB and the EBB axes to be as horizontal as possible. The position is determined by the length of the chain so you may have to use a half-link (ironic) to get to the ideal position. The ideal position for the BB, when looking from the drive side, is at 3 o'clock or 9 o'clock. At those points the torque on the EBB is zero regardless of the crank force. So stomp away.
OK - I tried it...on my tandem.
Steve Potts tandem with a pinch bolt EBB. Lightly greased EBB insert. Pinch bolts totally loose and insert easy to turn.

Set the EBB in every position and rode it (alone) on pavement out of the saddle with the front brake on. ZERO movement of the EBB insert.
If your EBB is really slipping something is out of spec and/or you are using too much grease.
 

·
Registered
Joined
·
3,931 Posts
Discussion Starter · #13 ·
shiggy©®™ said:
OK - I tried it...on my tandem.
Steve Potts tandem with a pinch bolt EBB. Lightly greased EBB insert. Pinch bolts totally loose and insert easy to turn.

Set the EBB in every position and rode it (alone) on pavement out of the saddle with the front brake on. ZERO movement of the EBB insert.
If your EBB is really slipping something is out of spec and/or you are using too much grease.
Every position = 12-3-6-9 o'clock?
Does not compute, if you turn it easily by hand then ?????. Your EBB or the stoker's? I don't know tandems (stoker has two chain rings?) but your result will be different with a one-person bike - guaranteed. BTW drag the rear brake to simulate a hill.
 

·
Premium Member
Joined
·
48,238 Posts
pacman said:
Every position = 12-3-6-9 o'clock?
Does not compute, if you turn it easily by hand then ?????. Your EBB or the stoker's? I don't know tandems (stoker has two chain rings?) but your result will be different with a one-person bike - guaranteed. BTW drag the rear brake to simulate a hill.
12 - 1:30 - 4:30 - 6 - 7:30 - 9 - 10:30. Could not do 3 without adding to the timing chain.
Tandem EBBs are at the front with a single chain running to the rear BB so it is just like a SS just on the left side.
The chain has slack on the bottom run when I run the EBB towards the back so the chain is not holding the EBB in place under load.
I did drag the rear brake, but it hard to keep from falling over. Jumped on the pedals, too, one and both together.
I need a small wrench to turn the insert and it rotates with little effort. If you can rotate the insert without using tools the tolerances are too loose.

My tandem has been ridden for many trail/dirt miles and the EBB has never slipped or creaked. I have stretched the timing chain and broken a couple, too.
 

·
34N 118W
Joined
·
2,246 Posts
ebb and me

shiggy©®™ said:
If you can rotate the insert without using tools the tolerances are too loose.
I can rotate my pinch-bolt ebb insert by hand when the bolts are loose. I'm using the outboard XTR BB, so I just grab the bearing housing and can usually spin it without a wrench. Or wench.

In other news: my chain recently started dropping off the chainring on bumpy downhills, with the ebb all the way forward, or tight (3:00). I figured I'd take out a link and rotate it slack (9:00) and reinstall the chain. No go! I managed to get the chain back on, but now it's tighter than a you-know-what and not even rideable - it barely freewheels. So I bought a new chain and will start over. It's my first run-in with an ebb limitation.

HW
 

·
Out spokin'
In cog? Neato!
Joined
·
16,365 Posts
Hollywood said:
...No go! I managed to get the chain back on, but now it's tighter than a you-know-what and not even rideable - it barely freewheels. So I bought a new chain and will start over. It's my first run-in with an ebb limitation.

HW
This EBB limitation phenomenon only occurs on pink frames. :p

--Sparty
 
1 - 18 of 18 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top