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cadance & large chainring(9 posts)

cadance & large chainringprokop21
Nov 21, 2003 10:03 AM
Hi:
I need an advise. I've been riding for about 5 months this year. I am able to maintain 90 rpm throught 2 hour ride, however I've been using a smaller chainring. When should I start using a larger chainring? I would appreciate your input or directions.
Thanks,
Matthias
depends on speed and gearingDougSloan
Nov 21, 2003 10:11 AM
I'd use the large chainring if, because of your speed and cadence, you are starting to use your small ring with either of your 2 smallest cogs. I'd definitely try to avoid using the small ring / small cog combo.

There is no inherent difference between the small and large ring, if you otherwise acheive the same speed and cadence (gear ratio).

Also, it may very well be that using the large ring with a larger cog could give you an intermediate gear step between two small ring steps. Experiment.

With 53/39 rings and an 11-23 cogs, I generally start to use the big ring around 18 mph, but it depend upon what I'm expecting next in the ride. If it is going to descend next, I'll bias toward the big ring, and vice versa.

Doug
depends on speed and gearingKSC
Nov 21, 2003 12:32 PM
Actually I read an article a long time ago, possible from Gary Fisher (someone famous), saying that if you can achieve the same gear ratio w/ different front back combos (without major stretch of course), it's best to use the combo w/ the larger front and back chainrings because it produces less friction than on the smaller rings. Just something else to consider.
Less friction and wear on the big ringKerry Irons
Nov 21, 2003 5:39 PM
For the same gear ration when using the big ring, the chain engages 36% more teeth on the rear cogs. This reduces chain wear and friction, the latter due to a less-sharp angle. I ride on the big ring for anything smaller than my 23 (any cog smaller than 17 when using the 39).
That's gear RATIO (typo) (nm)Kerry Irons
Nov 21, 2003 6:03 PM
Good qwestion.Chen2
Nov 21, 2003 10:37 AM
I think averaging 90 rpm is a great idea, I like to ride between 85 and 100 rpm whether flat, up hill, or down hill. With 53-39 rings and 13-25 cassette I'll usually stay on the 39 at speeds of 18 mph and below. And I'll go to the big ring if I think I'll be at 20 mph or above for some period of time. At 19 mph I'll go either way depending on what I think is coming up next in the way of hills or wind. So I agree with Doug.
~Al
re: cadence and ringshudsonite
Nov 21, 2003 10:51 AM
Not sure what is best, but this is what I try to do.

I shift from small to big chainring when my speed goes above 28 km/h and I expect to be going faster. I shift back to the small ring when my speed drops below 24km/h or when I coming to a stop sign.

I shift gears when my cadence hits about 95.

My 'rule' keeps me out of the small-small rings and keeps me in the sweet spot of my cassette.
Rules of thumb - switch to the small when approachingbimini
Nov 21, 2003 11:51 AM
a hill. Switch to the large at the top of the hill before you go down. I also tend to stay in the small ring on the flats when going into the wind and stay on the large when going with the wind.

In races I tend to stay on the big ring, except going up the steep hills.

I normally like to keep it over 90.
Rules of thumb - switch to the small when approachingprokop21
Nov 22, 2003 8:36 AM
Thanks for you input. It's been great to hear from so many of you. I will practice some of your suggestions, and see how it goes.
Matthias