Elbeinlaw

This is specifically a 20" tire question, not specific to any gearing or brand. The other week I had two experiences in a few days of starting up a very short but extremely steep slope (it felt and looked like it was way above 30 degrees, maybe truly 45 degrees) in the wrong gear. I died on the slope both times. Then I backed up and tried it again both times, but found that even in my lowest gear, my back wheel was spinning on the pavement and I died all over again.

It seems to me that my strategy must be wrong. Should I instead of starting on the lowest gear start a few gears up? In neither case could I rely on getting a running start up the slopes.

For physical reasons I have a hard time standing on the pedals, but if I did (and I'm trying to build up to it), starting up one of these slopes, would my standing posture require higher gears or lower than if I was just sitting and trying to power up?

2_i 

No matter what gear changing arrangement you have, it will most likely be impossible to change the gear on a very steep slope up, so you have to prepare yourself dropping as much down as you need ahead of time. A rear wheel slipping might be tied to a too smooth tread, but most often means that your gear was not low enough and maybe you lack a low enough gear on the bike. Could a lower gear have saved you? That is not clear. At some point you find yourself in a situation where you begin to roll back when the pedals are in the up and down positions. There had been propositions, I think, of some ratcheting mechanisms for bike in such situations, but at this point you would be on your own in trying to construct something like this for your bike. With the available drivetrains, the lowest gears can be useful for temporary use like for sharp turns when moving up a zigzag. No matter what, from some point on walking up becomes more effective. It becomes smoother, more energy efficient and prevents you from flipping backwards.

billridesbikes

If you could spin the back wheel, I think it means you don't have not enough traction for the gear that you're in, too much torque. A much lower gear could help, but if you're already in the lowest, standing won't help, it will make the rear wheel traction problem worse. Try to slide your butt as far back in the saddle as you can and lower your body as much as possible over the front axle to prevent the front wheel from popping up and throwing you backward. If your rear wheel is still spinning then its time to get off and walk.

If it's really really super steep and gravelly you'll have to push your bike forward a couple feet and then squeeze the brakes ad then use the bike to hold on to as you climb up a little bit behind and repeat (fun times).

Jipe

Indeed, if the wheel is slipping, its because there is too much torque, the gear is too low. A slightly higher gear could help.

But if the road is slippery, like some wet cobbles (or worse dead wet leaves on the ground).and really steep, the rear wheel will be slipping whatever you do, its hopeless.

2_i 

My bread and butter problem in winter is to get out of a ditch in the snow. My lowest gears are primarily for this purpose and they allow to apply the torque very precisely without losing grip. If your gear is high and you need a torque, you apply a jerk, stand up, etc., and the torque is very imprecise and you end up slipping. The similarity with going steep uphill is that the normal to the ground decreases and the grip worsens. In addition you struggle and waver in various ways, including in keeping your gravity center before the contact point of the rear wheel with the ground. This wavering requires from you to precisely readjust the torque, to stay close to but without transitioning to the slipping. All this extends the reach of controlled riding, but eventually all breaks loose if it gets steep enough.

Tourist in MSN

A change in gear won't help, if the wheel spins when you are trying to pedal up a steep hill, you have to walk and push the bike up the hill. Different rear tire might help if it lacks grip on pavement. I have had wheel spin on gravel but never on pavement, was there loose dirt or gravel on the pavement?

Elbeinlaw

No, it was perfectly dry. I need to go back out there and measure that slope. This was a portion of the Silver Comet trial heading west from Rockmart, GA--the trail wound along a river and then hopped up to the level of a bridge across the river. So that slope was the equivalent of a short, steep freeway entrance ramp. It was probably 10 yards of slope, and it sure looked like close to 45 degrees (which probably means it was 30!)

The bike and gearing are new to me, so if this illustrated a limitation of the bike, I need to know. If it's my limitation either in technique or strength, I need to train. And if sometimes you just need to get off and walk, despite all of the years of absorbing the cyclists creed (never, ever walk your bike up a hill) I'll do that.

Geepig

At 45 degrees I would be traversing it crosswise, at speed, and hoping I could hold it all together

If the slope is steep then sitting becomes no longer an option as the front of the bike will begin to lift. The trick is finding that point where most of your load is in front of the rear wheel contact point with the ground - not to far forward as otherwise the rear wheel may spin and not to far back you lose control at the front. Well, unless you are experienced enough to ride solely on the rear wheel...

The bestest thing to do is find a similar slope near home, and practice. I have a slope near me where I try out my (single speed) gear and tire combinations.