How sharp is too sharp?
#1
Slow Moving Vehicle
Thread Starter
Join Date: Oct 2000
Location: Norwood, MA
Posts: 1,068
Bikes: Felt F-70, Terry Madeleine, Novara Safari fully customized by me
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
How sharp is too sharp?
We all know not to ride big ring-big sprocket or small ring-small sprocket because the chain is at too sharp an angle. Richard Ballantine in Richard's 21st Century bicycle book says that triple chain rings on 7,8, or 9 speed blocks you should avoid 2 cogs on either side of the extreme, and that the middle ring shouldn't be used with the extreme cogs either. Is there a rational way of figuring out which angles are too extreme? Does the chain width effect the acceptable angles? Does anybody really know these things or is it all trial & error? If so, why don't production bikes come with charts of the "right" gear combos and the no-nos?
#2
Chi-Chi Monger
Join Date: Aug 2001
Location: Santa Clarita, California
Posts: 368
Bikes: 08 Cannondale Synapse, 09 Marin Alpine Trail 29er
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
A little trial and error I would say. You can really see when you are cross chaining badly. There really is no need for it. You should be able to find a comfortable gear without going to extremes. Personally, I ride 1-4 on the granny gear, 3-6, maybe 7th on the middle ring and 5-8 on the big ring. Just experiment...
__________________
When it's good it's really good...And when it's bad I go to pieces - David Bowie
When it's good it's really good...And when it's bad I go to pieces - David Bowie
#3
Senior Member
Join Date: Sep 2000
Location: Spokane WA
Posts: 1,148
Bikes: Seven Axiom Ti, Trek 620, Masi cylocross (steel). Masi Souleville 8spd, Fat Chance Mtn. (steel), Schwinn Triple Bar cruiser, Mazi Speciale Fix/single, Schwinn Typhoon
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 7 Post(s)
Likes: 0
Liked 1 Time
in
1 Post
Using the inside to outside small to small etc. combinations are a bad ida on 2 chainring bikes as well. On five, six and 7 speed compact clusters do not use one outer or inner cog with the opposite chianring. On 7,8,9 speed clusters two cogs.
My chain rubs on the outer chainring if I try to use either of my outer two cogs when I'm in my small chainring on my 53/39 X 13-23 set-up and others.
Extreme angles cause-
Uneven pressure, thus quicker wear on the bushings in the chainlinks. ( That's where "chain-stretch" comes from).
The chain plates to rub and erode the chain-ring and cogset teeth and against each other.
Ride that chain-line straight
Pat
My chain rubs on the outer chainring if I try to use either of my outer two cogs when I'm in my small chainring on my 53/39 X 13-23 set-up and others.
Extreme angles cause-
Uneven pressure, thus quicker wear on the bushings in the chainlinks. ( That's where "chain-stretch" comes from).
The chain plates to rub and erode the chain-ring and cogset teeth and against each other.
Ride that chain-line straight
Pat
#4
Banned
Join Date: Aug 2001
Location: upstate New York
Posts: 1,688
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
You should be able to use ALL cogs when you are in the middle ring of a triple ring bike.
__________________
Je vais à vélo, donc je suis!
Je vais à vélo, donc je suis!
#5
Senior Member
Join Date: Dec 1999
Location: Southern California
Posts: 771
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
I was going to post a thread on why I can't adjust my Ultegra triple to quiet down when at the extremes.
Now, I find I shouldn't be there in the first place.
Once again, unexpectantly, I've learned something new.
Thanks all.
Now, I find I shouldn't be there in the first place.
Once again, unexpectantly, I've learned something new.
Thanks all.
#6
feros ferio
Join Date: Jul 2000
Location: www.ci.encinitas.ca.us
Posts: 21,796
Bikes: 1959 Capo Modell Campagnolo; 1960 Capo Sieger (2); 1962 Carlton Franco Suisse; 1970 Peugeot UO-8; 1982 Bianchi Campione d'Italia; 1988 Schwinn Project KOM-10;
Mentioned: 44 Post(s)
Tagged: 0 Thread(s)
Quoted: 1392 Post(s)
Liked 1,324 Times
in
836 Posts
Allowable chain angles are a function of lateral chain flexibility and chainring tooth profile. I agree that one should avoid the large/large and small/small combinations on almost any modern derailleur bicycle, but which (if any) other combinations to avoid depends also on chainstay length, chainring size difference, cogset width, and chainring-to-cog alignment. If you can make the chain run quietly and if it stays on the chainring when you backpedal, you are in a usable gear.
Both of my road bikes, which use 8-tooth chainring drops (50-42 and 52-44) and mid-size 7-speed freewheels (13-26 and 14-28), work well in all combinations except large/large. On my 3/7 mountain bike (48-40-24 / 13-26), I avoid 24/13, 24/15, and 48/26.
Both of my road bikes, which use 8-tooth chainring drops (50-42 and 52-44) and mid-size 7-speed freewheels (13-26 and 14-28), work well in all combinations except large/large. On my 3/7 mountain bike (48-40-24 / 13-26), I avoid 24/13, 24/15, and 48/26.