Results 1 to 9 of 9
  1. #1
    mtbr member
    Reputation:
    Join Date
    Jan 2011
    Posts
    737

    Ideal EBB starting position?

    Guys,

    My next frame will be custom built specifically for use with a BEER PF30 EBB with a target gear.

    I have never used an EBB, the throw is limited to around 15mm so I want to make sure I optimize my start position. Am I correct in thinking that the ideal start is top and back with movement over and then down the clock? Adjustment on the top or bottom of the clock is the most linear with diminished effectiveness when moving along the sides of the clock.

    For a brand new chain where is the ideal start position? My favorite gear is (36x22) and as such I will be building around getting the best start position for that specific gear.

    Name:  Analog_clock_base.png
Views: 320
Size:  39.0 KB

    I am currently planning on using a target start point at "1" on the clock with the idea that as the chain wears the EBB will be moved to "11"?

    What do you guys think? Is "1" the ideal start point or is it better to start at "2", "12", "3", "4", or "5" and if so, why?

    -Mark
    Last edited by febikes; 02-28-2013 at 02:39 PM.
    Mark Farnsworth, Raleigh, NC
    http://farnsworthbikes.com

  2. #2
    mtbr member
    Reputation: Shalom's Avatar
    Join Date
    Nov 2008
    Posts
    1,998
    Personally, I start around 1, with the idea being that if the EBB slips (which it has not so far), then it will slip forwards, increasing tension on the chain (thereby minimising any potential slippage) and hopefully save my testicles.

    I could be wrong.

  3. #3
    more skier than biker
    Reputation:
    Join Date
    Nov 2006
    Posts
    1,699
    For me, I'd like to get my pedals as low to the ground as possible, so when I used a bike with an EBB (sliders now), I would shoot for the 6 o'clock position.

    This worked fine for me, but when I changed gears, and if I had to move the EBB significantly, i'd always forget to change my saddle height correspondingly.

    YMMV

  4. #4
    meatier showers
    Reputation: Sparticus's Avatar
    Join Date
    Dec 1999
    Posts
    7,330

    Ideal EBB starting position?

    Quote Originally Posted by febikes View Post
    Guys,

    My next frame will be custom built specifically for use with a BEER PF30 EBB with a target gear.

    I have never used an EBB, the throw is limited to around 15mm so I want to make sure I optimize my start position. Am I correct in thinking that the ideal start is top and back with movement over and then down the clock? Adjustment on the top or bottom of the clock is the most linear with diminished effectiveness when moving along the sides of the clock.

    For a brand new chain where is the ideal start position? My favorite gear is (36x22) and as such I will be building around getting the best start position for that specific gear.

    Name:  Analog_clock_base.png
Views: 320
Size:  39.0 KB

    I am currently planning on using a target start point at "1" on the clock with the idea that as the chain wears the EBB will be moved to "11"?

    What do you guys think? Is "1" the ideal start point or is it better to start at "2", "12", "3", "4", or "5" and if so, why?

    -Mark
    I run an EBB on my custom Vulture. Personally I'd start with the EBB in the lower half of the shell. First, a point of explanation that you doubtless already know but I'll mention it anyway since this is a public forum. If your framebuilder knows what height you want your spindle and you tell him that you intend to run the crank close to 6 o'clock, he will position the BB shell a little higher. On the other hand, if you tell him you're going to run the crank close to 12 o'clock, he'll position the shell a little lower. There is no "right on" shell position since the spindle will never occupy dead center in the shell, so the center of the shell must reside either a little higher or a little lower than the spot you want your spindle.

    Now the reason I'd personally want to start with the spindle in the lower half is because I'd likely never want my pedals any closer to the ground, but the possibility that I'd want them higher from the ground in the future is real. At some point in the future I may decide to run longer cranks or I might move to a locale that demanded more ground clearance to negotiate features, etc.

    As for positioning the spindle in the forward or rearward half of the BB shell, personally I don't think it matters.

    =S
    disciplesofdirt.org
    Remember who
    you wanted to be.

    Quote Originally Posted by riverrat
    Jaybo... quit *****ing and move to Texas

  5. #5
    meatier showers
    Reputation: Sparticus's Avatar
    Join Date
    Dec 1999
    Posts
    7,330

    Ideal EBB starting position?

    BTW as the chain stretches, you'll be rotating the eccentric forward (clockwise if high, counter-clockwise if low in the BB shell) so maybe consider starting at "7" or "11."

    Therefore "7" is where I'd start.

    That said, to me chainstay length trumps eccentric position so I'd ask my builder to make the stays as short as possible and accept whichever position this puts my crank spindle in. But in any case I'd start low so I'd have the option to raise my effective BB height later.

    =S
    disciplesofdirt.org
    Remember who
    you wanted to be.

    Quote Originally Posted by riverrat
    Jaybo... quit *****ing and move to Texas

  6. #6
    mtbr member
    Reputation:
    Join Date
    Jan 2009
    Posts
    607
    My 2cents....I have an EBB in my pimped RIG, I guessed at low a back when I first put everything together...liked it. But then thought I could get a better 'race' fit if the crank was higher and I was over the front end more, so switched it to high and back...tried it and like it - but the higher centre of gravity was noticeable and the single abilities seemed less, or my single track abilities seemed less.

    Changed it back to low BB and back (short chain stay)....this feels great. I watch my pedal strokes, and all is good.

    EBB allows for this amateur (me) to experiment and pretend that I have some ideal BB height and chain stay length in mind, but really I just know what I like. So you might have similar results, or totally different results - but at least you have choices.

    One last thing - the custom frame builder will tell you what to try first :-)

  7. #7
    .44
    Reputation: stremf's Avatar
    Join Date
    Dec 2012
    Posts
    406
    I think you should specify if the clock refers to the drive or non-drive side. I believe you were picturing the clock on the non-drive side, or with the bike facing the left. Some other members were picturing the drive side, or the bike facing right.

    My chain didn't seem like it would stretch that much. I'd try to get it to almost where you want to run it. I started mine in the lower hemisphere, but started getting too much pedal strikes, so moved it up top. I prefer the up and forward position.

    Another thing to consider is what other gearing you would like to use. If going to bigger cogs, obviously leave the chain longer, which means running the EBB far forward. Smaller, of course, is opposite.

  8. #8
    mtbr member
    Reputation:
    Join Date
    Jan 2011
    Posts
    737

    Thanks guys!

    Quote Originally Posted by Sparticus View Post
    If your framebuilder knows what height you want your spindle
    Ya, my framebuilder knows me pretty well

    Quote Originally Posted by Sparticus View Post
    Now the reason I'd personally want to start with the spindle in the lower half is because I'd likely never want my pedals any closer to the ground, but the possibility that I'd want them higher from the ground in the future is real.
    Good point! In my case I tend to have a preference for high BB and that is what my current bike is built for. I really like my current bike so the high side of the EBB will be based on my current geo. The low side will allow me to try the idea of a lower BB as an option but also let me return to the high BB if as I suspect I continue to prefer the 315mm BB height that I have on my current bike.

    Quote Originally Posted by Sparticus View Post
    As for positioning the spindle in the forward or rearward half of the BB shell, personally I don't think it matters.
    I am planning that with a new chain the EBB will start slightly reward of the apex of the shell and as the chain wears I will rotate forward (when using my ideal gear). If I hit the target chain stay length then typical wear should keep the EBB in a narrow range.

    Quote Originally Posted by twenty6black View Post
    EBB allows for this amateur (me) to experiment and pretend that I have some ideal BB height and chain stay length in mind, but really I just know what I like. So you might have similar results, or totally different results - but at least you have choices.
    Yes, experimentation is part of the attraction of EBB. My current bike has sliders and really short chainstays. My chain is setup for a shortest possible position and wears *very* slow so I don't really adjust the chainstay length often. The EBB will give me a chance to try various BB heights on the next bike.

    Quote Originally Posted by stremf View Post
    I think you should specify if the clock refers to the drive or non-drive side. I believe you were picturing the clock on the non-drive side, or with the bike facing the left. Some other members were picturing the drive side, or the bike facing right.
    Yes, good point, that is how I was thinking about the clock.
    Mark Farnsworth, Raleigh, NC
    http://farnsworthbikes.com

  9. #9
    meatier showers
    Reputation: Sparticus's Avatar
    Join Date
    Dec 1999
    Posts
    7,330

    Ideal EBB starting position?

    Quote Originally Posted by febikes View Post
    Ya, my framebuilder knows me pretty well
    ...
    No ****! lol

    Quote Originally Posted by febikes View Post
    ...
    Yes, good point, that is how I was thinking about the clock.
    Oops, I was assuming the clock represented driveside. Sorry!

    =S
    disciplesofdirt.org
    Remember who
    you wanted to be.

    Quote Originally Posted by riverrat
    Jaybo... quit *****ing and move to Texas

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •