jyl

Not sure where to ask this. So here it is.

Suppose you are already pushing kind of hard, like 7/10, and then you need more speed. Maybe you are trying to catch the green light, chasing silly commuter racing points, trying to match acceleration on a group ride, or maybe the blasted wind just started blowing.

Is your instinct to
- Gear down and spin up
- Hold gear and pedal faster
- Gear up and push harder

Is it the right instinct?. Why or why not?. Does it depend on terrain, bike, fitness?

Bandera

Since this is C&V and my experience is in Old School racing one does what one must, and one must be able to produce both spin & grunt on demand.
One goes with what the pace changes and terrain demands, as fitness allows.

The emphasis "back when" was to get the most out of the gear, fitness and technique were/are required.
Fixed gear base miles developed a smooth supple high cadence pedaling style with sheer dogged power to get over hills and a supple relaxed spin downhill and on the flats.

The machine, if of a reasonable quality and a proper fit, matters little. Lots of seat time and good technique does.
In season it's all about the program: Endurance, power & speed.

-Bandera

Velognome 

I find it depends on the machine, with a fixed gear both grunting and spinning, friction or IGH it's grunt before spin......with indexing and brifters it's shift and spin.

As a point of reference, most of my milage is on fixed gear bikes, long rides tend to be indexed- for whatever reason, I don't ride my friction or IGH bikes that often.

intransit1217

fwiw, I don't own a fixie yet. So if I find myself slogging for any reason, I usually drop down and spin up. I also tend to vary rpms to keep the legs fresh. Or maybe that's just crappy technique.

rhm

When in doubt, spin. Pedal faster, not harder. High gears are fine for relaxing, but if you want your maximum speed right now, spin.

John E

For your knees, spinning is also better than slogging.

ThermionicScott 

"Hold gear and pedal faster" is what tends to work best for me. Shifting takes a little time, and if I shift up first, I run the risk of getting into too high of a gear and bogging down. Perhaps brifters would solve those problems, I dunno...

RobbieTunes

Runner's instinct is to mash, and I've been one for years.
Wasting energy.

Recently, a friend and I were on the last 8-9 miles of a 45'er.
His FD decided not to shift to the big ring. We swapped bikes.

Forced to run the small ring, I decided to see how it went, on 39t up front, at speed.
Off I went, 22-24-26mph, and held it, and was able to relax.
A young guy caught me (running a 55t front)
We stayed at 26, hit 27.2, and carried on, dropped to 22mph in the last mile.
When we dropped to 20, the pack caught us.

It was amazing. I've never run that fast, consistently, with my masher mode.
Maybe it was just a good day, I dunno.

At the end, we swapped bikes back, and I rode the 2.5 miles home.
The young guy was with me, and I spun back up, intentionally this time.
Yep, must be something to it. Completely different power band.

So, since about 2 weeks ago, I say "spin up."

Prowler 

Think about a horsepower curve. Lots of torque at low RPMs but more power at higher RPMs (to the top of the curve then falls off). Basic mechanics says higher RPM gets you more power. I don't know if a human can spin fast enough to get over the top of the curve.

OldsCOOL

I answer this question parallel to the driver of a vehicle with a manual trans. The reason I have that feature is to shift when I want. If the rpms are slow relative to the gear, downshift. If it's too high, upshift. When it comes to a breakaway/chase/attack, wind out the gear and shift, repeat as necessary.

jimmuller 

Well, from a physics standpoint the math is pretty simple. As your rpm (or cadence) changes you shift when the power in the other gear is equal to what you have now. On both a car and a bike there are limits to how fast you can spin, such as valve float, con rod tensile strength, crank strength, etc.

But that physics similarity is a moot point. A car doesn't fatigue or recover. Other than heat build-up it doesn't care how long or hard it's been running.

On a bike it depends on how long and steep the hill or chase sequence will be, how hard you've been running and how fatigued you are at that time.

Most of the time I'll spin. If I'm pushing over a 100yd hill I may mash. If I'm pushing up a 1/2 mile hill, I'll spin. In many cases the limit is my aerobic capacity, and I can't go anaerobic for but so long. If I can catch the light/commuter/competitor/hilltop in a short distance or time, I may mash. I rarely do that, either chase or catch. It ain't worth the aggravation to chase stoplights, and I'll likely lose time by shifting anyway. If I'm already near my lactic acid or aerobic limit, I'll spin.

Translation: Spin. Definitely.

OldsCOOL

W***rrrrRRRRRR na-nah-na-nah-na-nah BANG!!***

rhm

And remember, of course, that it's easier to spin with shorter crank arms.

Velognome 

Classic!

pastorbobnlnh 

Rudi, I have a nice set of 165mm Stronglight cranks I need to use. Can you elborate further on what might be the best way to use these? I've been considering using them with a SA-AW, but maybe I should mount them on my '71 Paramount for my hill climb races?

Robbie, didn't you notice that 30mph tailwind that day?

SJX426 

I have been focusing on spinning. I know I tend to mash so installing a Cateye wireless II has helped me see what I am doing. My valves float at about 110-115 rpm. I like to shoot for the low 90's and stay above 80 with an target range of 85 to 95. When out of range, I adjust the gearing as needed.

Like @jimmuller states, if it is a short climb I will put more into it or stand up, long hill will require downshifting. Oh yeah, it depends on which cog I am on, some have a big jump and I may or may not want to shift given the conditions.

CV-6 

I do wonder about that. Easier in what respect? Typically we are talking a very small difference in crank length. Is it proven or just "common knowledge" that this is true. I cannot say I notice any difference.

repechage

It makes a difference unless you are really really limber and can touch your toes with ease.
I wish all my bikes had 165's.

On a C&V bike though, I find I must do both, spin (preferred) and crank, there are not enough gears. Gone are the days when I trained on a straightblock with only one bailout gear, a 21. But back then the biggest gear on the bike was a 44x14. Smallest 42 x 21.

jimmuller 

yes, well, fortunately back in my serious sports car days I enver experienced that. But I did see quite a few race engine make that kind of sound.

Addition: As rpm's climb a well designed engine should start losing power before it reaches a destructive speed. But once a tinker starts to tinker then all bets are off.

I have no trouble riding a straightblock with a 21, or even 17, as long as the road is all downhill. Fairly steep downhill.

Salubrious

On my Moto-Guzzi I used to just wind up the engine till the valves floated, then it was time to shift. Worked every time

A short stroke translates to a higher RPM because its easier to do. It works on an engine and works on the human frame. The most important lever in the crank system is actually your knees. Its easier to stand up straight from a partial crouch than a full crouch and that translates to a shorter crank arm allowing a higher spin rate (of course, a shorter crank arm requires that the seat be raised too). If you have knee problems a shorter crank arm is the way to go.

rhm

You are quite right, the differences in available crank arm lengths are so small that it hardly matters. Very few cranks are available in lengths shorter than 165. I have 160's on two of the bikes I ride the most; 165's on most of the others, and 170's on a couple others where I haven't been able to find the right ones in shorter lengths. And I cannot say I notice any difference.

I experimented for a while, and for a couple years did most of my riding on 140's. Not C&V, though. I noticed a difference for a little while; within a week it became perfectly normal. Best thing about it was I really learned to spin! Then I got out my road bike with 175's and profoundly hated it. The longer arms were really hard on my knees. I sold that bike and have been searching out shorter arms ever since.

My conclusion is: even if I can't notice the difference between 165 and 170, my own experiments have shown me that shorter is better.




Incidentally, if anyone who doesn't believe me wants to trade his 165 mm first generation Dura Ace crank for my 170 one, I'm eager. The same goes for a Stronglight 57.

I don't suppose that's a Stronglight model 57, it it?

The thing about shorter crank arms is you have less leverage, so if you ever get yourself into a situation where you actually need that leverage, the shorter arms put you at a disadvantage. So if you have several bikes with 170 mm arms and your MO is to hammer up the hills, the shorter crank arms are not going to help. If you're tempted to try it, first concentrate on spinning up the hills. Once you're comfortable with steady cadences over 100 rpm or so, try the shorter crank arms.

All that said, though, remember that the difference between 165 and 170 is really very small. The shorter crank arms give you a minuscule advantage if you're spinning, and a minuscule disadvantage if you aren't. The advantage you get from spinning, regardless of crank arm length, is much more important.

rumrunn6

sprint? get up out of the saddle ... no?

noglider 

If I'm tooling along aimlessly and I know I'll spin out completely without shifting up, I will shift up. Other than that situation, it's best not to shift up when I want to increase speed.

On @rhm's recommendation a few years ago, I snagged a junior racer crankset. It was a TA Cyclotouriste with 42/32 rings and 155mm arms. Just this morning, I shipped the 42t ring, since I'm not using it. I put the arms on my Viscount fixie. The funny thing is, the arms don't feel strange to me at all. On the other hand, I can tell when I'm riding 172.5 arms without looking. 175's annoy me.
@rhm, I have a pair of 160's I'm not using. You want them? I don't know the BCD, but I think it's a common one.

Salubrious

I am 6 feet tall but I have a long torso- my inseam is about 32 inches. I find that 175s are problematic- I tend to spin more than mash, and I could not make power on the 175s- they would just wear me out. I moved to 165s on the same frame and spinning seemed to get easier. Its not a big difference, only a few percent, but over miles that adds up. From everything I can see in the world of bicycles the 2-5% difference is actually justification to buy a new carbon frame or wheels or the like. This is something that should not cost nearly so much.

rhm

@noglider, no, thanks for the crank offer (looks like 110 mm bcd) but I have more cracks than I can use. I'm sure someone can use it, though!