Is your front chainring Ovalized?- Mtbr.com
Results 1 to 20 of 20
  1. #1
    fc
    fc is offline
    head minion Administrator
    Reputation: fc's Avatar
    Join Date
    Aug 1996
    Posts
    33,276

    Is your front chainring Ovalized?

    Are you riding biopace-like rings? The best way to tell is when your chain is tighter on some parts of pedal range.

    I've been giving this a lot of thought and here's what I've come up with.

    - your chainring didn't come like that. No chainring comes out of the milling machine oval.

    - Over time, you ovalized the chainring with your power! Since you are a singlespeeder and you mash the pedals at the 2 o'clock position, you've molded the chainring into it's new shape

    - you can rotate your chainring, a quarter turn to normalize it.

    - when you're working on your chain tension, check it throughout the whole pedal range. Cause you might think you're fine but you may be too tight or too lose on the oval parts.

    Agree, disagree? Anyone have anything to add to my brain fart theory of the day??

    francois

  2. #2
    Back of the pack fat guy
    Reputation:
    Join Date
    Jan 2004
    Posts
    3,982

    my problem was with the freewheel

    Quote Originally Posted by francois
    Agree, disagree? Anyone have anything to add to my brain fart theory of the day??

    francois
    I noticed significant chain tension variation when I'd spin the crankarms. Recently, I replaced my freewheel (from a 20t to an 18t, both were/are ACS claws freewheels) and the big tension variation went away, almost completely. So, I'd say the chain tension variation, at least for me, was from the freewheel, not the chainring.

  3. #3
    hot like a box of fire
    Reputation: a nice cake's Avatar
    Join Date
    Apr 2004
    Posts
    148
    Quote Originally Posted by francois

    - your chainring didn't come like that. No chainring comes out of the milling machine oval.

    francois

    Actually you'd be suprised. It's more common with BMX parts (spiders, sprockets) but i've seen and setup bikes with all new drivetrain parts, only to experience tight spots in the rotation. It's sort of boggling how that might happen in this day of precision machining. Nonetheless, it does. In frustration I switched over to a a solid chainwheel from a component company I trust with topnotch QC, and haven't had any tight spots since.

  4. #4
    mtbr member
    Reputation:
    Join Date
    May 2004
    Posts
    16
    Quote Originally Posted by francois
    - Over time, you ovalized the chainring with your power! Since you are a singlespeeder and you mash the pedals at the 2 o'clock position, you've molded the chainring into it's new shape
    I'm no physician -- -- but I am not certain that the force applied here would tend to ovalize the chainring since you are really twisting in along the chainline and against the chainring bolts rather than compressing it.

  5. #5
    Medium?
    Reputation: Fast Eddy's Avatar
    Join Date
    Dec 2003
    Posts
    6,723

    I rotate

    my ring once in a while. I've done it once on the ring I'm riding, but I don't remember when, so it's time to do it again. I suppose I'm agreeing with you. Scarey.

  6. #6
    Card Carrying Member
    Reputation: kitchenware's Avatar
    Join Date
    Jan 2004
    Posts
    2,032
    Two weeks on my new Salsa ring and it's custom biopaced. Just noticed it the night before last while lubing my chain. Thought it was a bent spider at first, but nope. Thought I was either crazy or got a bad ring. Gonna rotate it tomorrow so it can bend the other way.

  7. #7
    all hail der Fuhrer Bush
    Reputation:
    Join Date
    Mar 2004
    Posts
    1,635

    yes, it is, thanks for asking

    One one SS, the chainring is a 36t second generation (rounder) Biopace ring. On the other SS, it's a way oval first-generation steel Biopace.
    Biopace works great for high gear, slow cadence SS climbing. It still sucks like it did 2 decades ago for fast spinning, but since most of my SS riding involves willing the cranks to turn over on steep climbs, Biopace is great!

  8. #8
    Not a regular
    Reputation:
    Join Date
    Jan 2004
    Posts
    4,079
    I don't think chainrings necessarily get ovalized from riding (ss or otherwise). I think there are several combinations of factors that make rings look out of round. The tight/loose chain syndrome can be a combination of rings that are not perfectly round (think about it, rings for geared bikes can have a bit of run-out because the derailleur takes up the tension). Sloppy fit on the chainring bolts - an imperceptible amount of slop can translate into a tight/loose spot in the chain tension.

    A hub not bored and threaded exactly on center can be one cause. A freewheel that is not perfectly centered around the axle center can be another. Chainrings fitting sloppily on the c/r bolts is another.

    I was QC'ing some BMX mini bikes years ago and the stock drive train had a big tight/loose spot. To push my point that the maker's tolerance was off, I took a set of XT cranks (the first gen compact drive with the skinny arms), stripped off the outer and inner rings, installed it and lo and behold, the XT was more out of round than the Taiwan made cheap crank! Go figger.

    But that's not to say your power (not mine) could ovalize a ring. It'd be interesting to get 2 rings made from the same production batch, make sure they are exactly the same; run one for 6 months to a year and then lay the unused ring on top of the used ring to compare roundness. Could happen. Who's going to volunteer?

  9. #9
    mtbr member
    Reputation: pswann's Avatar
    Join Date
    Feb 2004
    Posts
    132
    But can't it also be where, on the spider, you've tightened up your chainring bolts? On my T-vativ Stylo crankset I have plenty of slop in the spider/chainring interface. I just used the Sheldon Brown trick of finger-tightening the chainring bolts, turning the pedals, and when I find a tight spot I tap the chain on the chainring and just barely slide the ring back toward whatever the true center may be. After a few turns you find a good happy medium, then tighten everything down. If you're really patient you can get it spot-on perfect.

  10. #10
    Submit to your ride!
    Reputation:
    Join Date
    Jan 2004
    Posts
    486
    Pswann hit the proverbial nail on the head. This fact of chain tension is known by those who own tandems and have installed the timing chain between the captain and the stoker...

    SS Slave

  11. #11
    mtbr member
    Reputation: pacman's Avatar
    Join Date
    Jan 2004
    Posts
    3,931
    If the chain binding occurs with every 180 degree rotation of the crank then you have an ovalized ring and no centering will cure it.

    (If you have 2:1 gearing you can eliminate the freewheel as the problem by changing the relative position of crank and freewheel - rotation wise - and see if the binding occurs at the same crank position)

  12. #12
    mtbr member
    Reputation:
    Join Date
    Jan 2004
    Posts
    504

    Biopace ok

    Quote Originally Posted by francois
    Are you riding biopace-like rings? The best way to tell is when your chain is tighter on some parts of pedal range.
    francois
    Sounds wierd, but biopace chanirings can be used on a SS / fixed gear as the rings have a constant average diameter. As long as they are centered on the spider this won't happen.

    Pswann is on the money, if your chain has tight spots it's because the chainring is not centred on the spider. I would even postulate that if it were possible (and I think it's highly unlikely) to ovalise your rings over time, the effect would be as for Biopace rings. What do others think?

    Sam

  13. #13
    mtbr member
    Reputation: dodjy's Avatar
    Join Date
    Mar 2004
    Posts
    478

    Idea! The problem and solution.

    From: http://www.sheldonbrown.com/fixed.html

    Chain Tension

    he chain tension on a fixed gear is quite critical, and is regulated by moving the rear axle back and forth in the fork ends. If the chain is too tight, the drive train will bind, perhaps only at one angle of the pedals (chainwheels are not usually perfectly concentric). It should be tight as it can be without binding. If the chain is too loose, it can fall off, which is quite dangerous on a fixed gear.

    Set the rear axle so that the chain pulls taut at the tightest part of the cranks' rotation. One at a time, loosen up each of the stack bolts, and tighten it back just finger tight. Spin the crank slowly and watch for the chain to get to its tightest point. Strike the taut chain lightly with a convenient tool to make the chain ring move a bit on its spider. Then rotate the crank some more, finding the new tightest spot, and repeat as necessary.

    This takes a little bit of your hands learning how hard to hit the chain, and how loose to set the stack bolts, but it is really quite easy to learn.

    Tighten up the stack bolts a bit and re-check. Tighten the stack bolts in a regular pattern, like the lug nuts on a car wheel. My standard pattern is to start by tightening the bolt opposite the crank, then move clockwise 2 bolts (144 degrees), tighten that one, clockwise 2 more, and so on. Never tighten two neighboring bolts in a row. You may prefer to go counterclockwise, but try to get in the habit of always starting at the same place and always going the same way. This reduces the chances of accidentally missing a bolt.

    Once you have the chainrings centered and secured, adjust the position of the rear axle to make the chain as nearly tight as possible without binding. Notice how freely the drive train turns when the chain is too loose. That is how freely it should turn when you are done, but with as little chain droop as possible.

  14. #14
    drev-il, not Dr. Evil!
    Reputation: Drevil's Avatar
    Join Date
    Dec 2003
    Posts
    3,906

    My ENO cured my ills

    It hasn't always been severe, but I have always had that problem. My thought has always been along the same line as Pswann. Two Raceface cranks, two XT cranks, Raceface rings, XT rings, and bunches of Salsa rings, the chain has always tightened, loosened, tightened, loosened...

    However, with the ENO and it's spiderless, splined design, it simply doesn't happen. It's awesome. No tightening of the chain during its revolution. I believe it's because you don't have to worry about the chainring's position. Just slap it onto the crankarm, and it's perfectly round and perfectly centered every time.

  15. #15
    mtbr member
    Reputation: dodjy's Avatar
    Join Date
    Mar 2004
    Posts
    478
    How much are the replacement rings for the ENO? I was looking at getting one although I wish it didn't require the square taper BB.

    dd..''

  16. #16
    mtbr member
    Reputation:
    Join Date
    Dec 2003
    Posts
    373

    ......

    I'm with Drevil....... I had a spot spiderless 34t ring on M952 cranks and the the difference between tight and slack was huge....... put an 34T Eno crankset on and voila..... constant tension.

    I know that when the ENO's were first announced there was talk of maching the ring after it was mounted to the cranks, I'm not sure if this is/was proactical, but I do know it seem to be roundest mounted ring I've ever come across.

    Now if I could just stop mt BB creaking I'd have the perfect setup.......

  17. #17
    drev-il, not Dr. Evil!
    Reputation: Drevil's Avatar
    Join Date
    Dec 2003
    Posts
    3,906
    Quote Originally Posted by dodjy
    How much are the replacement rings for the ENO? I was looking at getting one although I wish it didn't require the square taper BB.

    dd..''
    $40 for 32T, 34T, 38T, or 44T, in green or silver. The ones with the integrated guard may be introduced at the trade show in October.

  18. #18
    Penis Goat!
    Reputation: GirchyGirchy's Avatar
    Join Date
    Dec 2003
    Posts
    804
    The only 'ovalizing' type stuff I've noticed is from either an out of round freehub, or I don't have the chainring centered perfectly on the crank arms.

  19. #19
    cut like the fog.
    Reputation: bones's Avatar
    Join Date
    Dec 2003
    Posts
    357

    So what about spline interface chainrings then?

    My suffering has a spider on the chainring which matches to the XTR crank spline, no bolts. There's definitely tight and loose spots as I turn the cranks.

    I always assumed it was because of manufacturing tolerances. Could I really powerful enough to bend metal???


    b. aka Herc


  20. #20
    IMBA Guy
    Reputation:
    Join Date
    Jan 2004
    Posts
    173
    I've never ovalized a ring, but I've had teeth wear out more quickly at around 2-4 o'clock and 8-10 o'clock on the chainring than they did elsewhere on the ring. The difference in wear became so significant that it would cause the chain to alternately stick & slip, it would also cause tight & loose spots in the chain. The ring was ruined. I make sure to rotate my rings on occasion now. I also try to get rings that aren't 6000 series aluminum, that stuff is too soft for me.

    Has anyone else experienced this?
    Powered by Krispy Kreme!

Similar Threads

  1. 2004 SJ FSR Exp. Disc - shuddering front brakes
    By Richie in forum Specialized
    Replies: 34
    Last Post: 01-11-2005, 10:39 AM
  2. new drivetrain weird front chainring skip.what?
    By dang in forum Drivetrain - shifters, derailleurs, cranks
    Replies: 4
    Last Post: 10-20-2004, 01:12 PM
  3. rattling noise from front deraileur
    By jakubc in forum Tooltime
    Replies: 11
    Last Post: 06-08-2004, 06:52 AM
  4. Sorry, I HAD to do it. IF:(F80 RLT --> Sid WC)
    By gatechMTBer in forum Weight Weenies
    Replies: 29
    Last Post: 02-01-2004, 07:39 AM
  5. Front Chainring: Ramp or Not
    By Gearless Dave in forum Singlespeed
    Replies: 7
    Last Post: 01-29-2004, 01:47 PM

Members who have read this thread: 0

Posting Permissions

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

THE SITE

ABOUT MTBR

VISIT US AT

© Copyright 2019 VerticalScope Inc. All rights reserved.