Thursday, August 07, 2008

Why Fixed Gear Bikes Are Better On Ice

We're in the midst of what passes for a heatwave here in the Pacific Northwest and somehow I find myself involved in an email discussion about setting up a bike for riding in icy conditions. I'm reminded that I heard once that Jack London wrote one at least some of his famous Yukon stories on a sweltering passage through the tropics and in that spirit I've extracted (with the permission of the other emailers) bits of our discussion of how Nate should build up his winter bike.

Nate wrote:

Fixed or SS?
Any benefit to either in inclement weather?

Michael replies:

You don't get that dérailleur thingy all covered in the omnipresent road grime.

If you go SS you can't join the Sunday morning rides out of River City Bikes.

Real suggestion: get a flip wheel and find out for yourself.

Kent adds:

Fixed definitely has the edge in dicey conditions. You know exactly how much traction you have. I blogged about that phenomena here:

http://kentsbike.blogspot.com/2006/02/icy-commute.html


Note, this post predates my days of studded tire ownership. But the ultimate winter commuter would be a fixie with studded tires.

Michael then asks:

That would be because you're never not pedaling on a fixed. You don't think you'd get the same effect by never coasting? ie, is the fixed benefit because it's already there by default.

Nate adds:

I can see benefits to both ss and fixed in the ice. When approaching a known trouble spot, I like being able to approach it in a confident position and coast through it without changing position or momentum on the bike. Just passing silently like a ship through the fog.

But I can see the benefit of fixed for the overall trip. More instant feedback of what you are riding over.

The rear wheel I'll be using is a flip flop, so I'll try it both ways and see how it goes.

I'm taking my frame/fork in for a fresh powder coat this week and will begin building it back up, hopefully finishing before the weather gets cold. Because of clearance concerns, I'll probably go with the Nokian A10 700x32. Even though this is the smallest available 700c studded tire, fender clearance is still going to be tight, so I may be ashioning my first ever set of custom coroplast fenders.


Kent clarifies the fixed advantage thusly:

Michael, here's why the fixed on ice is NOT THE SAME as a single speed. First off let's assume that you actually never do coast your single speed. That makes you absolutely unique on the planet, BTW and leads to the question of why you bother lugging a freewheel mechanism along in the first place. But let's say you do that. Now let's take the case of deceleration, also known as slowing down. You can only slow by applying your rim or disk brakes. In both cases, the mechanism is the same, pads that interface with a rotating surface. Since brakes don't just stop you instantly (you wouldn't want them too!), the brake pads slide along the rotating surface. You increase and decrease pressure to control your velocity.

But (and this is the important thing) you have no way of knowing what slip you are getting comes from the pad/rim interface or the tire/road interface. So you think "hmm, I'm not slowing fast enough, maybe I'll squeeze the brakes more. If the slip is in the pad/rim interface, that will slow you more but if the slip is in the tire/road interface, you worsen your skid.

On the fixed, much of your velocity modulation is via your legs. Even when you use your other brakes, you get the feedback of your legs together with the action of the other brakes. This lets you do the same kind of calculation a modern automobile does when applying its anti-lock brakes, comparing the rotating speed of the wheel with the braking inputs to determine if a wheel is skidding. On a fixed gear bicycle, your brain can do this automatically, in real time. On a coasting bike, you don't have the data to do this calculation.

While slips and skids are most common in deceleration, they can also occur on acceleration. Wouldn't a freewheel and fixed be equal there? Nope. Even a very tightly engaging freewheel mechanism (say a Chris King) will have a bit of slop before it engages. Fixed gear bikes also are never perfect and have a bit of slop but it's almost always less than the slop in a freewheel. And when pulling out from a stop, it's hard to tell if the slip you are getting is from slop in the drivetrain or the tire slipping on the road. Minimizing drivetrain slip makes road slip more noticeable.

Finally, in sub-freezing conditions, freewheels sometimes become sluggish in having their pawls engage. Back in Minnesota every winter I'd see freewheel pawls freeze, making the freewheel spin freely in both directions. Running light lube in the mechanism and keeping water out usually prevents this, as does warming the freewheel/freehub above freezing but fixed gear drive-trains are immune to this particular problem. Various riders on rides like the Ididasport and the Arrowhead 135 have kept a fixed cog in reserve for extremely cold conditions.


13 comments:

Anthony said...

The jury is still out on this one for me. I ride year round in the Yukon, which is very cold but not really a lot of ice -- mostly snow.

I've ridden both and both have their pros and cons. I think I'll be trying fixed again to start this winter and see how it goes.

I think moisture is the key to stuff freezing up. I've ridden below -30 C without anything freezing up, but it's a very dry climate here.

Now, the tires at that temperature are a whole other issue... Feels like you're riding uphill all the time.

Anonymous said...

I've had the freeze-up on a single-speed in Boston.
It's not very nice when you need to accelerate out of an intersection.

The control you get from your legs on a fixed-gear rear wheel is really remarkable.
When it does get dicey, you don't want to touch the front brake but you can modulate the rear better than rim braking.

I've also found that riding fixed gear teaches you good balancing technique wherever your foot position happens to be on a bump or a turn.

Coasting over a trouble spot is nice, but only if you see that trouble spot before you're in it.
You develop a reflexive response to bumps or slipping after some time riding fixed.

This bike-handling development is slow but real, and helps a lot in slipping and sliding situations.

Studded tires and fixed gear is the safest and surest method I feel riding to work in winter.
Just ease up the gearing for cold weather and inevitable plowing through snow and slush.


All this to say "Listen to Kent's advice."

PsySal said...

Agreed! I rode a fixed gear bike with studded tires all winter last year in Calgary and I halfway can't wait to do it again this winter. Great on ice, and also great in snow since you can just power through it.

Jill said...

One thing about fixed gear bikes ... if you have to do any hike-a-biking through deep snow, those pedals spinning around and digging into the powder are going to hinder your forward progress that much more. :-)

Living in a wet, semi-cold climate, I've only had a freewheel freeze up once on me, and I got it to engage again by turning the bike over and spinning the crank as fast as I could to "warm" it back up. That was on old hub, too, used a lot in really wet conditions. It was about 0 degrees F.

I can certainly see why a fixed gear would be better on ice, but if you prefer to ride freewheels (as I do), I don't see fixed as being enough of an advantage to bother with (although I do have a fixed hub/SS cog on the front wheel of my Pugsley, just in case)

Larry said...

Hi Kent. Here, just north of Boston, fixed-gear with a good studded front tire and a pretty wide (28 cm at least) rear tire is my winter ride of choice. Mostly, the roads have patches of snow or ice, and the off road trails get too bumpy for an enjoyable ride. I confidently ride over ice that would be a challenge to walk over. It's not the ice and snow that stops me from commuting in the winter -- with fixed-gear and a studded front. But I do get shy about riding when the plowed snow piles up so much that the roads narrow. More so since the advent of the SUV.
Best,
Larry

H said...

There's ice and there's cold.
There are also various flavors of ice.
For that commute home on a zamboni slick glare from a day of freezing rain, I'm finding I want a hub with a drum brake. There are spots I don't want to pedal through and I don't want to spend time chipping ice off the brakes before heading for home. This happens a couple times a year here.
I like the Sturmey 3 speed, as it doesn't seem to freeze with the oil lubed gears.
Have thought about fixed, but don't think I'd want to gear one low enough to allow me to be really really smooth on the extra slick places. Too big of a gear on a slick incline makes me a pedestrian.
A hub gear with drum brakes seems tough to beat for filthy weather.

beanz said...

I haven't thought about fixed gear for a while - although I learned to ride a bike on a fixed gear bike and didn't know any different.
Then lo an behold there was an article about them in the paper yesterday http://www.guardian.co.uk/lifeandstyle/2008/aug/07/healthandwellbeing.ethicalliving
and then i read your blog today :>)

Jason Nunemaker: said...

As a year-round Iowa commuter, I'd say Kent nailed it, at least for our conditions. I went fixed (with studded tires) for winter riding last year, and there's nothing like it. Downhills that terrified me with a freewheel are nothing on fixed... just stay off the front brake and control the speed with your legs.

One thing to keep in mind with studded tires, fixed or free: Your *tires* may have traction, but your *feet* probably don't. I can't count the number of times I've confidently rolled up to a stop, put a foot down, and promptly fallen on my arse. ;-)

Mike C said...

@larry:

a good studded front tire and a pretty wide (28 cm at least) rear tire...

Ay caramba! No wonder you can stay upright on ice.

How much did you have to spread those rear dropouts? :-)

Eric C. said...

I've been thinking about a fixed gear for winter for a long time but there's one thing nobody seems to mention. If your route is hilly you'll have to stand on some sections. It seems to me that going up a hill standing on your bike in ice is pretty much the worst thing to do. Is this only valid for flat areas?

Kent Peterson said...

Eric C.,

My commute route is not flat by any stretch of the imagination (I skirt the northern edge of Cougar Mountain and have a tiny 17% section on Irving Street in Seattle and the switchbacks of Colman park). Climbing out of the saddle isn't a problem. That said, my winter fixie is geared fairly low, so most of my climbing is seated.

I've always found it interesting that some folks reserve their fixies for flat routes, to me the climbs and descents are where the fun is. I guess that's why I live in an area where the mountains are right in my backyard.

Kent

Aytan Luck said...

The main advantage to a fixed gear in winter (in my opinion) is that is will keep you warmer, since it keeps you in constant motion. I do recognize that a direct drive will give you a more immediate sense of your tire's relationship with the road. However, I don't see how that's important if you are riding studded tires. The studs will keep you from slipping.

Also, when going over questionable surface (ice, snow, dirt, gravel) I want to be in a low gear. Gears are awsome. I believe that geared bikes are NOT more expensive to maintain or service that fixed/SS, especially for winter. A winter bike should have cheap components that are easy to replace. Used derailleurs (even cheap ones) often have plenty of life in them, and can generally be gotten for free (even before I owned a bike shop, free bikes would seen to present them selves constantly). Used fixed gear parts (esp. cheap ones) are usually used well and are generally harder to come by.

byron said...

Kent has knees of iron to ride a fixed gear for this long and in the snow. In cross on changing terrain, speed, and conditions it's best to keep pedaling; especially in turns on grass or into the mud. You learn how to pedal and brake at the same time. So you can do this too with gears and spare your knees the backpedal pressure.