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Message started by FlyingLaZBoy on Mar 8^th, 2012, 9:37am

Title: Bikes and Gearing
Post by FlyingLaZBoy on Mar 8^th, 2012, 9:37am

There's been some discussion of gearing, gear-inches, doubles, and triple cranks, etc. associated with going on hillier rides... Thought it might be a good thread to create.

Here is a good article on gearing needs when doing climbing, although it's from a "DF" point of view... it starts out from a layman's understanding, and gets into the math later...

http://www.kenkifer.com/bikepages/touring/gears.htm

The page also has some VERY nice links on the right side to follow to other pages about gearing...

Paul

Title: Re: Bikes and Gearing
Post by shellbear on Mar 8^th, 2012, 10:52am

This made the engineer in me happy. ;) Now I MUST become a gearing nerd so I can figure out what I need on my MUsashi! Ha ha. Thanks for the resource!

Title: Re: Bikes and Gearing
Post by jayg on Mar 8^th, 2012, 11:30am

FlyingLaZBoy wrote:

Thanks, Paul. Interesting article. Article recommends pedaling downhill to help remove toxins from legs, before attacking next hill. Now, if those pesky roadies would just get out of the way......... :)

Title: Re: Bikes and Gearing
Post by rmillay on Mar 8^th, 2012, 12:14pm

I don't know if we have many hills of a size to worry about pedaling downhill (spoils a perfectly good coast,) but coming down from the mountains in Colorado, I can attest to my legs seeming to go 'dead' after just a few minutes of coasting.

Title: Re: Bikes and Gearing
Post by jayg on Mar 8^th, 2012, 1:07pm

rmillay wrote:

I almost always pedal downhill, particularly on rollers. I used that technique effectively on hilly rides when my Musashi had the stock compact crankset and 11/32 cassette.

Title: Re: Bikes and Gearing
Post by Bud_Bent on Mar 8^th, 2012, 11:07pm

I have to pedal on the downhills to catch up with everyone who dropped me on the uphill...

Title: Re: Bikes and Gearing
Post by LightningPilot on Mar 9^th, 2012, 6:12am

jayg wrote:

[quote author=rmillay link=1331221072/0#3 date=1331230458]I don't know if we have many hills of a size to worry about pedaling downhill (spoils a perfectly good coast,) but coming down from the mountains in Colorado, I can attest to my legs seeming to go 'dead' after just a few minutes of coasting.

I almost always pedal downhill, particularly on rollers. I used that technique effectively on hilly rides when my Musashi had the stock compact crankset and 11/32 cassette.
[/quote]

I always work the downhills on rollers because, in most cases, you top the next crest with very little loss of speed. Rollers are our (bents) friends [smiley=pepper.gif]

Title: Re: Bikes and Gearing
Post by FlyingLaZBoy on Mar 9^th, 2012, 3:17pm

Good ol' Sheldon Brown's gear calculator page has always been a favorite of mine - it'll give you gear inches, meters development, or speed at RPM for a wide range of conditions... http://sheldonbrown.com/gears/

If I use a 1" tire for a 559, a 650, and a 700 wheel, it gives the following speeds at either 100 or 120 RPM

100 RPM 120 RPM

559 wheel 33.7 40.5

650 wheel 34.4 41.3

700 wheel 37.1 44.5

Of course, I would imagine that even Sheldon's calculator has to use "theoretical diameter" numbers for wheel/tire figures, not taking into effect the fact that you compress a tire a few tenths of an inch when you apply rider weight.

The southbound part of the HOT Hwy130 ride allowed me to crank up to max speed (i.e., 'spinout'), given the slight downhill grade and the tailwind... My Xstream26 has 559 wheels with 1.1" Duranos, and a 52:11 high gear combo. I topped out at 38mph... 650 wheels would have added another ~1 mph to that, and 700s would have been zoom-zoom!!!

Title: Re: Bikes and Gearing
Post by FlyingLaZBoy on Mar 15^th, 2012, 8:06am

And as Opus pointed out in the Lancaster Rally thread, I've been thinking 'Gear-inch" and "Development" were the same thing all these years... Alas, no! [smiley=notworthy.gif]

Title: Re: Bikes and Gearing
Post by FlyingLaZBoy on Mar 15^th, 2012, 8:13am

LightningPilot wrote:

I always work the downhills on rollers because, in most cases, you top the next crest with very little loss of speed. Rollers are our (bents) friends [smiley=pepper.gif]

That was one aspect of the old TTTT course -- while the climbing on the front half was long and gradual, the back-half hills were often ones that you could carry some speed up if you wanted to. Not so much, on the new TTTT course! And of course, the last ~5 miles were a semi-pleasant mostly-downhill run -- i.e., "When you reach The Retreat, you've got it beat!"