climbing
 

How to simulate high gradient.
ie, If I climb an 8% grade in 34-28, what higher gearing is needed to simulate a 16% grade on the same 8% grade?

If you could put out the same watts at a much slower cadence (which you probably can't, but if), then your speed up the 16% grade would be a little more than half your speed up the 8%. Thus in the same gear, your cadence would also be about cut in half. So use half the teeth in the back, or 34-14. But since your watts would be down at a lower cadence, probably more like 34-13? What fun!

Here in flatland SW FL., I never concern myself about what % I'm trying to simulate, I just apply the brakes while pedaling. Can be standing in my 39/28, hands on the hoods barely making forward progress for a distance of 10 feet or a mile. Have been doing this since last Thursday when I registered for Six Gap. Going out shortly to ride my make believe mountains.

"apply the brakes while pedaling?" I'm talking about climbing.

Are you riding the bicycle and pedalling ... or walking?

If we assume:
1) the rider only cares about power output and cadence, and
2) the rider wants to see the same power output and cadence on both the 16% and 8% hills,

Then, the rider should climb the 8% hill at desired power and cadence (given by 34-28 in your case) and is already simulating the 16% hill because he or she will simply change gears on the 16% grade to achieve the same power output and cadence. Otherwise, any change on the 8% hill is either changing power or cadence and would then not be simulating the 16% hill.

EDIT: of course, you may not have the gears to achieve the same power and cadence on the 16% hill (because you are not on a mountain bike). And if 34-28 is your easiest gear, you are likely back to CFB's advice above. If, on the other hand, you have even easier gears (you are riding a hybrid), you would shift to achieve the cadence you would use on a 16% grade while maintaining the same ground speed on the 8% hill that you were getting with the 34-28.

a couple of things going on here, and i haven't thought it all the way through yet...

what you need to do is figure out what ascending an 8% grade at a target speed equates to in power for you.

the power you output on steep climbs (8% and 16% would both qualify), is 100% related to your ascent distance per unit time. so if you wish to simulate double the ascent rate / power (going from 8% to 16%), you would want to halve your mechanical advantage through the transmission and effectively have each pedal stroke cover double the distance/ascent. So a 34-28 to a 34-14 would achieve this, assuming you can hold the cadence. this is going to be freaking tough.

simultaneously, if you wanted to have a target gear that you wished to climb in, you would increase the cadence until you're ascending at the target rate.

If you want to climb a 16% hill you're going to need to be able to climb an 8% hill with higher gearing than 34-28. Accept that you'll be standing and at a lower cadence going up the 16% hill. Figure out the highest gearing you can use to climb the 8% hill and double the size of the rear cog for the 16%.

For example if you can climb the 8% hill @60RPM in your 34-15, you'll need a 34-30 to get up the 16% hill. This assumes the two hills are the same elevation. Your vertical ascent rate in meters per hour should be the same but your speed is going to be half on the steeper hill so you need proportionately lower gears.

if you really need a 34-28 to climb the 8% hill then I'd suggest you probably need to lose some weight before tackling the steeper hills.