I'm at a 2.75 ratio right now and have two problems: starting up hills and spinning fast enough down them.
I am looking at a two or three gear automatic IGH. The three gear I'm not sure I can find, so I looked at parts building off the Archer A2-H and got my weight down to 17 pounds.
It'd be nice to gain another mile or two per hour but I'm not sure how much a difference the weight is going to make. Is four pounds noticeable?
What type of bike are you riding and why are you using an IGH?
4lbs is a difference but won’t change anything on the downhill. Plus your weight will make a larger effect on the total system
Unified Fisso. It's a single speed, no IGH yet. I'm light, maybe 130 pounds.
Having multiple gears will make you a lot faster. An astronomical difference compared to shedding 4 pounds. Unless the conditions you ride in are particularly harsh a derailleur setup is way more bang for buck than any IGH or gearbox.
Realistically, no it won’t matter much. The gearing may change your time going up, but not going down.
gearing will make a huge difference up and down
assuming a 150 lbs rider, going from a 21 pound bike to a 17 lbs one will save you... 9 watts... on an 8% climb... at 12.6 mph (that's 409 watts vs 400 watts). so unless your area is very hilly and you are a very strong rider, you will not notice a significant difference.
How do watts convert to miles? My route is pretty hilly. The pavement is not the best, though I've ridden worse.
there's calculators out there if you want to the exact math. But take it from a math nerd:
basically do it if you have the money, but weight is very very overrated in importance.
A very rough rule of thumb is that 1 kg (2 lbs) of weight saved corresponds to about 1 minute saved for every 1000 meters of elevation gain. 4 lbs of weight savings will not gain you anywhere near a "mile or two per hour".
watts is a measure of strength. it's how hard it is to hold a speed. in the example i gave, it means that the 17 pound bike will be about 2% easier to ride on that steep 8% hill.
People on bikes are like internal combustion engines. We have a sweet range of RPM (pedal turns per minutes). It varies a bit from person to person, but 70-90 is a good starting point for most people. If we try to pedal up a steep hill at 40 RPM, it hurts and it’s inefficient. It can also be unsafe because bike handling is harder when grinding hard and slow.
The point of bike gears, whether IGH or derailleur, is to let us pedal at or near the sweet RPM range, even when the hills get steep. The added uphill efficiency is where you’ll get your added speed. Not spinning out downhill helps too, but not as much.
Weight saving of a couple of pounds does not matter unless you’re racing. You’re not racing. People who race on hills have gearing that goes from a max of about 4:1 to a min of about 1:1.
Yeah I've noticed pain both ways. Pushing too slow/hard and spinning too fast makes my knees hurt.
Have you tried /r/fixedgearbicycle ?
For what? It's a weight question and there's more traffic here lol.
I suppose it's also a hidden gearing question, like what's the ideal three ratios...
...why not get a rear derailleur and pick up a much bigger gear ratio on an even lighter system?
I should and I might but truth be told I think I only need three gears: low, mid, high. That and my frame has no place to mount it.
You're not going to 'gain a mile or two per hour' by buying another bike that's 4 pounds lighter.
If you want to be faster and are worried about weight then go get a DXA scan to determine your body composition and change your eating habits so you lose excess bodyfat.
Also do actual training instead of 'just riding' if performance is important to you.
4 lbs will make you 2.5% faster uphill, 0.4% faster on flats.
Unless your area is flat, 2 speeds is not enough. Additional speeds (up to ~7, depending on hilliness) will make a bigger difference than weight.
A 1x12 derailleur plus flat bar shifter costs about 40 Dollars. You will need some shifter cable hose for like 10 and a basic cassette (HG) for like 30. And you will need a rear wheel with a freehub that can accomodate the cassette (I would go HG as it is very common and parts for it are generally cheaper). Wheelset can be from like 200 (basic alloy) to 5000 (high end carbon).