Messages

106

Gear Talk / Re: Gear Chainring

« on: May 15, 2011, 03:42:25 pm »

I have a Co-Motion Mocha Tandem with 26” wheels.  How does this effect gearing?  Assuming the same gear combination how would it differ from a 700 wheel while climbing up hill? BTW mine has 52-39-30 front and 11-28 rear.

Co-Motion's site says that bike comes with Continental Sport Contact 26x1.6" tires, so I went to Continental's website to see just what that is, and there's no such thing.  Guessing it's a mountain-bike 26 though, meaning 559mm bead seat diameter as opposed to 571 which is the road 26" (650c), I can guess the difference is a little under 5% (when you consider that the bigger tire partly makes up for the smaller rim diameter), meaning that a 23-tooth cog on yours would be approximately like a 24-tooth on a bike with 700c, and 700c with a 23-tooth would give a gear that's just a hair higher.  A cog of that size generally has you in the climbing area, so the difference between 23 and 24 teeth there would not be enough to feel.

107

Gear Talk / Re: Bike selection for use with trailer

« on: May 11, 2011, 12:49:21 pm »

I started with a Bob trailer, and then migrated to panniers.  I would go with a longer wheel base bike to tow your trailer.  I only used my short wheel base racing road bike one time with a Bob trailer, it was that scary.  The trailer will subject the bike frame to some stress, so a super light weight bike is not going to work out.

I would be interested to know what was scary about it.  I suspect it had more to do with the geometry which was not oriented toward stability under load.  The stiffest frames are carbon fiber and are used by professional racers who leg press over a thousand pounds in the weight room, and I've read of quite a few 350-pounders on the forums on carbon-fiber bikes with no frame problems, just wheel problems; so these frames are anything but weak.  I believe they've gotten even stiffer since the linked report, although most of us don't have any need for that kind of stiffness.

108

Gear Talk / Re: Gear Chainring

« on: May 09, 2011, 02:29:48 pm »

Not sure how this problem would ever occur if you size the chain correctly.  Wrap the chain around the big ring and big cog and through the rear derailleur.  Just long enough to make this circle with a tiny tiny amound of extra play.  Then the chain is the right length.  If you are in the small chainring and small cog, the rear derailleur may not have enough length to take up all of the slack.  No problem.  Having the chain hang loose on the bottom does not cause any concern.  And using the small chainring and smallest 1-2-3 cogs is not something you should ever do anyway.

In the small-small combination, the chaing may rub on itself behind the upper derailleur pulley, which can't be good.  But our tandem has 24-42-52 with a 13-34 cassette and it works fine because the smallest ring only gets used with the cogs on the large half of the cassette.

109

Gear Talk / Re: Tandem Brakes

« on: May 05, 2011, 04:24:43 pm »

I have a Santana Sovereign SE with the old style drum brake that threads on to the hub.  I want to upgrade to a disc.  Is there a disc brake that threads on to the hub like the old drum does or will I have to buy a new hub set up for a disc?

When I was on the T@H tandem forum (when we were riding the tandem all the time), Bill McReady (sp?-- can't remember), president of Santana, told about his tandem braking tests down a certain road near Santana.  I'm not familiar with the exact road, but it's in an area we'ver ridden countless times.  None of the discs could handle the load like the drum could.  The extreme heat would warp the disc, melt caipler parts, or, in the case of the hydraulics, boil the fluid and make the brake useless.  It was rather steep (16% IIRC), but we've been down even steeper ones.  We have rim brakes (which can make even the front tire skid, wet or dry, with one finger on the lever, and I've never noticed any fade) and I added the drum brake for drag down those steep, curvy descents.  It is really nice to have the third control there for it as a bar-end shift lever, as I can set it to the appropriate amount and not have to keep holding it.  I would not consider a disc an "upgrade."  If you really must do it, get the 8" rotors (or maybe there's something bigger now-- I haven't been keeping up), and get the mechanical ones.  I think Aavid BB ones were what some of the tandem teams were liking.  They were still saying however that the pads didn't last anywhere near as long as rim-brake pads, or the shoes in the drum brake.

Someone on that forum said his motorcycle had discs and they were great, and he thought bike technology was lagging.  Then another member who knew a lot about motorcycles jumped in and said the disc brake system on the motorcycle weighed 40 pounds and that's even though the motorcycle can use the engine for braking, meaning it would have to weigh even a lot more otherwise.  Disc brakes also change the way stresses are put on the bike's frame, requiring it to be stiffer and heavier in the chain stays and fork blades.  If you're riding a lot in ice and snow, it might be worth it.

110

Gear Talk / Re: Best Brake pads

« on: May 04, 2011, 03:36:49 pm »

Are you sure they're not old stock?  Scott-Mathouser became Kool Stop AFAIK.

111

Temporary ACA Route Road Closures / Re: Pacific Coast Route - section 4, map 49 road closure - April 2011

« on: May 02, 2011, 04:39:39 pm »

Seems like if the slide is stable enough to put 10 ton excavation rigs on it

I don't know how this is handled, but I'm sure they don't put the rigs on the slide, but rather whittle it away from the ends while the weight of the rigs is on something solid.

112

Gear Talk / Re: Tandem crank legth

« on: May 01, 2011, 03:32:18 pm »

He studied riders of a wide range of heights using cranks of a great range of arm lengths (IIRC, 130 to 220 mm) and found no relationship between them for power output, comfort or anything that would justify a custom crank.

This is the same outcome I've seen from a few different studies where they used a lot of subjects and tried a wide range of crankarms on them, but I have not seen the one you mention.  If you have a URL, I'd like to add it to my bookmarks.

It is a common misconception that longer crankarms will give you more power, for a couple of reasons.  All it will do is move your shift points down a bit.  The only thing I would comment about 5 or 10mm making a big difference is in knee injury.  One of my knees has had many minor injuries starting in childhood, and even though I'm 6' tall, 165mm is much, much better for avoiding pain and re-injury than 175 or even 170mm.  A nice side benefit with the shorter crankarms is that you don't have to keep the inside crankarm up in turns.  Another one is that you can have a lower torso position on the bike without your legs hitting your chest.  (My wife appreciates that.)

113

Gear Talk / Re: Gear Chainring

« on: April 30, 2011, 03:15:55 pm »

but at the end of the day, when you are tired and climbing

and in a much higher elevation than you're conditioned to (which is a very significant factor!)

114

Gear Talk / Re: Tandem crank legth

« on: April 30, 2011, 03:13:35 pm »

Unfortunately the range of crank lengths available is super narrow, like making shoes only in size 9.5, 10, and 10.5, and dictating that everyone should be fit into those, even if you need a size 8.  Ridiculous.  And it's worse for tandems because look who rides them-- often a husband and wife and she's too short for 170mm, even when she was young, and they often can afford the tandem only after the kinds are grown and gone meaning they're older and knees aren't as good and they need shorter crankarms to avoid re-injury.  Fit systems usually neglect to address age and past injuries, things that affect ideal crankarm length probably more than anything else in bike fitting.

There are a few choices for shorter ones-- very few, and they're expensive, but not as expensive as knee surgery.  da Vinci is one of them, going down to 130mm.  TA is another, going down to 150mm, and known for having the highest quality you'll find anywhere.  Both these companies have them for tandems.

115

Gear Talk / Re: Best Brake pads

« on: April 28, 2011, 03:00:31 pm »

I've run Kool Stop salmon pads for years on my tandem and now our triplet.  Love 'em.  Yes, they do wear faster, but just carry extras with you.

How long do you find that they last?  The pads on our tandem with Tektro mini-V's have 10,000 miles on them and still have plenty of life in them but they're not Kool Stop brand.  The black Kool Stops on my single bike have over 20,000 miles on them and still have a little life left in them.  I have the salmon-colored ones on another single bike with 18,000 miles and they're at about the same stage of wear.

116

Temporary ACA Route Road Closures / Re: Pacific Coast Route - section 4, map 49 road closure - April 2011

« on: April 28, 2011, 02:38:18 pm »

Do people on their bikes ever just walk their bikes across slides like this?

I just took a look at the .pdf linked above.  It has a picture of it that tells me there's no way you'll be able to walk it.  There's about a 40° embankment of unstable, loose, slippery soil.

117

Gear Talk / Re: Best Brake pads

« on: April 27, 2011, 02:31:34 am »

Thank you. Do you recommend a specific Koolstop pad over another?

Obviously you'll start with the ones that fit your brakes, but from there, the usual recommendation is salmon-colored if you do a significant amount of riding in the wet, otherwise black (unless you have carbon rims).  I don't remember why black is supposed to be better for generally dry conditions.

Our Burley road tandem came with cheap Tektro mini-V brakes.  With the stock pads, I could skid even the front tire, wet or dry, with one finger on the lever.  (I found out by accident and will never do it on purpose for demonstration or any other purpose.)  On our single bikes, we have black Kool Stop pads and can stand the bikes on their noses with 105 brakes, although I haven't tried it with a pannier load.

Edit: I should add that we do have the drum brake on the tandem as a third brake for drag on steep descents which not only eliminates the worry about blowing a tire from rim heat but also is much easier on the hands since I don't have to hold the levers the whole way down.  Do resist the temptation to shave down the drum's fins to save weight, as that will dramatically reduce its capability to get rid of the heat.

118

General Discussion / Re: ACA Maps

« on: April 26, 2011, 02:28:19 pm »

They are printed on plastic paper.  It looks like normal paper, but water doesn't affect it, and it's very tough.  There are plenty of other just plain sensible parts of their design too.  They're always getting updated, so I think it's worth it to buy the latest instead of used ones.

119

General Discussion / Re: Camelbak / Water Bladder

« on: April 26, 2011, 12:28:30 am »

You'll probably want as little weight on your body as possible, for reasons of saddle and back comfort.  If you use one of the XLab (or similar) brand gizmos that allow you to put two additional water bottles behind the seat, then use Zefal Magnum water bottles which hold 32 ounces each, you'll get 128 ounces with nothing on your back, and none of the Camelbak-cleaning problems.  I use four of these bottles, two on the frame in the normal places and two more up high behind my seat, above the huge seat bag.

Edit, based on following posts:  Four of the 32-ounce Zefal Magnum bottles (two going behind the seat) holds a lot more than any Camelbak!  Four of the largest of other brands of bottles (28 oz each instead of 32) still comes out to 112 oz which is still more than any Camelbak.

120

Gear Talk / Re: Disc or non-disc brakes

« on: April 22, 2011, 01:10:56 am »

Here are a few of the many discussions on it:
http://www.adventurecycling.org/forums/index.php?topic=4986.0
http://www.adventurecycling.org/forums/index.php?topic=5072.0
http://www.adventurecycling.org/forums/index.php?topic=8696.0