Sixty Fiver

Dude... I'm 45 and should be trading in my fixed gear bikes for gearies too.

Have re-geared a few of them but this stems from a back injury that affects my ability to mash up hills and not because I am "old".

Could still hand a few people their asses on a ride as long as I can spin like a gerbil on crack.

Sixty Fiver

Have you noticed any more "how many gear inches ?" threads since this was posted ?

I think Scrod closes them and puts a link to this thread in when he does it... or should.

Sixty Fiver

Not really... I am small and light (built like Contador) and despite having some really good power I can't lay it down to the max because it puts way too much stress on my back.

But I have always been able to spin like a mo'fo so work hard at that... old school time trialists rocked a gearing in the mid to high 70's to knock down sub hour 40's and the lesson here is that to go fast you don't need a big gear if you can spin those cranks a little faster.

My business partner is a big guy (275 pounds) and an ex racer who has amazing cardio and the ability to mash some pretty big gears as well... even in his 70's he was running a 54 tooth crank on his touring bike and could climb in gears that would destroy most people's knees and lungs.

Said that when he got tested for cardio and pulmonary function his numbers were unheard of... he was having dizzy spells after working out that were caused by a state much like hyperoxia or hyper ventilating.

He has been a test subject at one of our hospitals for a few decades because of this... doctors thought that a really big 70 year old guy with a resting pulse of <50 must have had a heart problem but it is just that his VO2 max is so incredibly high his heart does not have to work very hard and when it does he suffers from a little O2 overload that causes dizziness.

We can only wish to have this problem.

markaitch

jeez...i would have thought this thread would do more business, but maybe since it is titled a primer for noobs, the veterans here have their gearing down & don't really have much use for it. or perhaps i am the only dunce that just is never 100% satisfied with any gear ratio/inches i run

anyway, heres my latest dilemma...

i am this close to ordering a new bike that offers lots of chainring & cog options in the build.

my problem is that i just do not care for the usual gear ratio suspects due the local terrain & my riding style. it is as flat here as my 1st girlfriend was. i have to purposely go out of my way to ride on the few bridges over the inter-coastal waterway to get any incline at all & only 1 of those is even slightly challenging.

the upshot is that right now i am runnning a 14t cog with a 46t chainring. i have no problem keeping up a pretty good cadence or riding over any of the previously mentioned bridges & outside of the occasional stiff headwind i still sometimes wish i had even more gear-inches. not to mention that while I don’t think of myself as a participant in silly commuter racing, it does still gripe me a bit when I am chugging along pretty good & a roadie blows by me pedaling lazily along in the biggest ratio on his 20 or 30-something speed & i know i can not keep up no matter how much I spin.

so tell me…am I crazy to be considering ordering the new bike with a 48t chainring & a 13t or even 12t cog? those small cogs are bad on chain-wear right? i know I would be better off with a bigger ring & a bigger cog but the 48t is the largest they offer.

thanx for any suggestions…

Squirrelli

Here's your answer to everything:

caloso

48x12 = 105 g.i. = 28mph @ 90rpm

Is that crazy? It would be for me, but maybe not for you.

Sixty Fiver

It works if your name is Boonen or Merckx or you ride in a vacuum.

Running the numbers is one thing, pushing those numbers is another... have experimented with a 100 gear inch drive and found that I go faster when I can spin at 120 rpm and not destroy my knees at 90... and it does not allow for any snappy acceleration, hills, or wind.

Worked with a messenger who insisted that his nearly 100 gear inches made him faster except he was probably the slowest messenger I ever saw... had no jump and by the time he got up to speed you'd be a mile down the road dropping off your next package.

Highest day to day gear I ever ran was 82 and was out for a ride working on my TT speed and found myself riding parallel to a course that had been set up for one of our many triathlons which I don't pay much attention to.

Ended up pacing a bunch of these guys for a few miles and got a few thumbs up from the riders as I wasn't dressed like a superhero and was riding a 30 year old steel conversion... and was not having any trouble keeping up.

Have been passed in the same way too... have been out there killing it and had a few people on fixed and geared bikes blow by me like I was parked.

They must have been on crack.

markaitch

ok...
so you guys are telling me i am really better off spinning more @ lower ratio/inches? makes sense.
hope you didn't get me wrong earlier, i do keep up a purty damn quick cadence most of the time with my current set-up, but it is nice to sort of "lope" along & rest sometimes, especially on the long rides.
btw, i have cogs from 14t-19t, can't seem to keep myself from experimenting constantly & bigger g.i. just feels better to me.
well then, waddaya think about my 46x14, is it so turrible?

caloso

FWIW, we have a flat 10 mile TT series here, and when I've done it Merckx-style, I've run 52x15 (94 g.i.) on my FG. It's still pretty heavy if you get any kind of headwind, but that's the challenge of doing a fixed TT, right?

markaitch

52x15...ummmm....i like that

macnab

There was an epic post around gearing and stopping without skiddnig that Ken Cox posted (recently?) I can't find it, but it belongs in this thread.

iBgearLess

I was running 46x17 for a long time and then went to 46x18 and am very happy with it. I don't race, not in much of hurry to get anywhere so it works perfect for me. If I do trail riding on my FG I switch to a 19 tooth cog.

Affixed

Isn't there an iPhone app that does this all for you?

treefilly

what do you guys think about 49/16? im currently riding 49/17 but wanted a little more challenge and maybe a higher speed. thanks!

Sixty Fiver

How long can you spin that 49:17 @ 90 rpm ?

How often do you spin it at 100... or 120 ?

If you are not regularly spinning out the gear you have now a taller gear is going to slow you down as your cadence will drop... think I have spoken often of riders dropping from an 80 gear inch ratio to one in the mid to high 70's and finding they got faster and could farther at higher speed.

Squirrelli

I think it's stupid and you should learn to spin a lower gear ratio.

Corwings

Recently dropped to 42/17 on my second bike/the one with a brake to accomplish two tasks; 1) Get better at spinning, and 2) climb a little easier.
So far so good

Sixty Fiver

Track season is upon us here and for the next 4 weeks the guys will be riding 74 gear inches to develop their spin before they move up into the low 80's... considering here that the track is smooth and there are no hills and no wind that one has to deal with.

In the old days people started training by doing 1000 miles on a 74-76 inch gear and this is what was often used on the open road to knock down sub hour 40's... you have to spin that at 110 rpm or more for a full hour to knock this down and have to deal with wind and grades.

tristen

for anyone wanting to see the math behind that calculation.

it confused me until i learnt that gi is the diameter of the imaginary "wheel" not the circumference.

so let's see:

105gi x 3.14 x 90rpm = 29700 inches/minute.

29700 inches/minute x 60 (minutes) = 1782000 inches/hour.

1782000 inches an hour divided by 63360 (inches in a mile) = 28.125 miles an hour

there we have it, bang on target.

it's interesting that the 48x12 gearing means you're somehow driving an imaginary wheel 105 inches in diameter. that's a big wheel.

Sixty Fiver

chain ring teeth x wheel diameter in inches / cog teeth = gear inches.

puppypilgrim

Permit me to add to this discussion. Use the formulas referenced in the posts above to calculate what chain rings and cogs you need.

Online calculators are available here:
https://software.bareknucklebrigade.c...it.applet.html (does not work with Google Chrome)
https://www.sheldonbrown.com/gears/

Your preferred gear inch will depend on:
- how fit you are
- how strong you are
- the terrain you do 90% of your riding
- the wind conditions for the majority of your riding
- how many skid patches you want (if that's important to you)


Since most riders cannot perceive a 1 gear inch difference, consider the following gear ranges with soft edges, not binary precision.

60-65 gear inches = good for older riders or weak knees or touring.

66 gear inches = good all round gear for flats and hills. Not too slow on the flats, not too hard on the hills and wind. Touring is even possible. Great acceleration from standstill.

69 gear inches = near ideal for most people and most applications unless you are exceptionally strong. City gear and hills are feasible.

70-73 gear inches = superb range. At 100 rpm, it produces 21.4 mph (34.5 km/h). At 100 rpm, the force required to turn the pedals is still relatively light. Anything is this gear range produces an excellent balance between acceleration, hill climbing, combating winds and flat road speed. Note that at 20 mph (32.2 km/h), approximately 80% of the power being produced by the human body is being used to overcome air resistance. This is why it is so hard to sustain any speed above 20 mph (32.2 km/h) during a daily commute. If you know how to spin, this gear range will not be slowing you down.

76 -81 gear inches = this range maybe useful in places where there are no hills and where riding with a slow cadence is preferred to riding with a rapid cadence. All other things being equal, one will sweat less pushing a larger gear with a slow cadence at low speeds (say up to 15 mph) versus a lower gear with a high cadence. All bets are off if you push a large gear with a high cadence! This range is also harder on the knees due to the pedal force required to turn the cranks. Acceleration from a standstill will be noticeably slower than gears in the high 60s and low 70s. It's a tall gear for city riding and sprinting from traffic to traffic light and intersections. Hills will also slow you down in a big way.

81 and up gear inches = velodrome racing gears in controlled conditions, and short term training applications.

These are my opinions only based on general observation, lots and lots of reading and learning from others who have gone before. I'm sure someone will say, "But I ride 92 gear inches and it takes me everywhere!". My reply would be, "Good for you. I hope you have money for the knee surgeries you're gonna need."

Find a gear low enough that allows you to climb the highest hill you need to ride on a regular basis and use that as a starting point for your singlespeed and fixed gear riding. With FG, you need to ensure the gear you pick is high enough that you can ride DOWN the tallest hill you've just climbed.

Best wishes,
Victor

sulr

Great thread and I enjoyed your post Squirrelli

sillygolem

I am a clyde and I just converted a bike boom 10 speed (29 lbs. with its original freewheel and derailleurs) to SS. I live in a hilly area and I'm running about 73 gear inches (46t chainring, 17t freewheel, 27 1 1/4" tires) and it works fine.

However, this bike has a steep seat tube which lets me stomp hard. I think I would probably want to go with lower gearing if I was riding a more relaxed geometry.

caloso

Great post, puppypilgrim.

fattybikejones

Just ordered my first SS for round town and fun rides.. No big grinder climbs where I am riding.. Stock gearing is 46 / 16.. hafta see how that all works out.. Oh yeah, I'm 48