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OP: Only one way to find out: Have at It!
Be sure to have a camera crew w/ a high frame rate available to document the experiment. Enjoy! -Bandera |
I did used to do the descent of Juaquim Miller Road from Skyline Blvd over Oakland, CA on a 42-17 with brakes but not using them. I was in my 20s, had raced two years before and had around 15,000 fix gear miles on my legs. I was also doing work that I knew had long term health issues I would eventually see. My post head-injury crazy years. To keep my sanity, I would ride up Juaquim Miller, turned around at Skyline and ride down. Fully crazy. Juaquim Miller is a parkway, two lanes either side of a planted meridian. Speed limit 50. I never got passed. (I doubt I hit 50 but I was close.)
42-17 has the nice feature that at 20 mph, one's cadence is 100 rpm. Easy math. 50 mph is 250 rpm. Been very close. But as a very experienced fix gear rider with recent race legs. Young and crazy. On a very funky Peugeot UO-8 that had been crashed many times and was as straight as a soggy noodle! (But newish Binda toestraps pulled tight! I wasn't all nuts.) Ben |
Originally Posted by ThermionicScott
(Post 21085671)
I might also be accused of dancing around the actual question, but I think it depends on the rider and their bike fit. Assuming the feet don't detach from the pedals, it's a matter of what happens when the cadence goes above what they have experienced before*. I used to run my saddles higher, and noticed more bouncing then. When your knees are always slightly bent, I think they are better able to move with the pedals. I think this has also saved my bacon on a few occasions when I spaced out and tried to coast -- I might have been in trouble if my legs had been straight enough to lock my knees. ;)
* I think your question speaks to the importance of practicing high cadences so that you are physically and mentally prepared when they happen. Whether that's deliberately riding around on a really low gear, or seeing how fast you can take a spin bike at the gym. :thumb: |
Originally Posted by seau grateau
(Post 21085848)
Bad bike fit definitely messes up your pedaling. Saddle too high leads to legs overextending and hips rocking back and forth to compensate, and the mechanics of it all are going to be really hard to control at high cadences.
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if you have brakes, just unclip and keep your feet out of the way of the pedals. then you can go as fast as you like and won't have to worry about your legs getting ripped off
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Not a exactly a consequence of his legs not keeping up, but at 20:00 we see a possible outcome of riding down a mountain fixed, with no brakes:
youtube.com/watch?v=RsVfoKxlz5M Not a shill for State Bikes; yeah the series is an advertisement, but I thought this episode was esp. fun. Sorry, I can't hyperlink yet. Almost there. |
If you're riding brakeless you should always have a backup plan.
i.e. remove both of your legs from the pedals and learn how to put them on your frame and rear wheel. This way, unless you're literally not rolling, you will be able to stop yourself. Some riders prefer a chainstay foot position, personally, I like to huck my entire foot on top of the seat stays so I can actually skid the tire and stop. I've had a few situations where my chain skipped off, but I don't think I've ever hit too fast of a cadence. There was one situation where I came close... I've hit about 36-37 mph (I had a gps speed thingy) on 45/16 gearing (I think that's near 190 rpm at the crank) and I was practically rubber legging it, but I was still (barely) able to keep up with the bike. It felt like my legs were not really attached to my body anymore and were just spinning on their own (with my input though). I was still able to positively apply forward motion with my leg muscles and feel them respond but it was getting to the point where I was feeling the cranks push back more than I wanted them too. I could feel my legs getting kind of numbish and they felt "liquid" and "heavy" , more like masses of gelatin than bones and muscle. Even 1 mph faster and I think that I would not have been able to push my legs anymore and the cranks would be pushing them instead. But instead of being nice and controllable, it felt like my legs would have just been wild spaghetti noodles flopping around. Luckily, this was when I wasn't riding brakeless and had a front brake. I tepidly tapped the brake out of fear of flipping over and there was almost no response, so I started to squeeze a little harder. Normally the front brake will send you over the bars if you hold them but I eventually squeezed them as hard as I could because I wasn't slowing down. It felt like my face was melting into my head and I had to use literally all of my strength to push against the bars to keep myself on the bike. I finally slowed and when I touched my rim it was incredibly hot. Needless to say I never tried that again. I don't know what motivated me to do that in the first place. I think I was just on a really long hill and I just let go. My intention was to keep it around 30 mph and just coast because I didn't think that my body could go that fast becuase i'm not a trained cyclist. I thought that I would just know that I am going fast and be able to press the brakes and stop. Anyways, that's' the best description I can give of what going too fast (for my physical limitations) on a fixed feels like. For future reference for people that haven't done this yet, it's not a linear predictable progression as far as what/where or how fast your legs are going. It just starts happening and it doesn't feel like you're going much faster at a certain point. If you're on a long hill, either mount a speedometer on the bars and find your physical limit on the flats, or just be very careful. OH, I was riding shimano 105 pads and brakes at that time with the proper 105 lever too. BEST brakes i've ever ridden to this day. I have yet to try discs though. |
Originally Posted by BicycleBicycle
(Post 21094126)
If you're riding brakeless you should always have a backup plan.
i.e. remove both of your legs from the pedals and learn how to put them on your frame and rear wheel. This way, unless you're literally not rolling, you will be able to stop yourself. Some riders prefer a chainstay foot position, personally, I like to huck my entire foot on top of the seat stays so I can actually skid the tire and stop. I've had a few situations where my chain skipped off, but I don't think I've ever hit too fast of a cadence. There was one situation where I came close... I've hit about 36-37 mph (I had a gps speed thingy) on 45/16 gearing (I think that's near 190 rpm at the crank) and I was practically rubber legging it, but I was still (barely) able to keep up with the bike. It felt like my legs were not really attached to my body anymore and were just spinning on their own (with my input though). I was still able to positively apply forward motion with my leg muscles and feel them respond but it was getting to the point where I was feeling the cranks push back more than I wanted them too. I could feel my legs getting kind of numbish and they felt "liquid" and "heavy" , more like masses of gelatin than bones and muscle. Even 1 mph faster and I think that I would not have been able to push my legs anymore and the cranks would be pushing them instead. But instead of being nice and controllable, it felt like my legs would have just been wild spaghetti noodles flopping around. Luckily, this was when I wasn't riding brakeless and had a front brake. I tepidly tapped the brake out of fear of flipping over and there was almost no response, so I started to squeeze a little harder. Normally the front brake will send you over the bars if you hold them but I eventually squeezed them as hard as I could because I wasn't slowing down. It felt like my face was melting into my head and I had to use literally all of my strength to push against the bars to keep myself on the bike. I finally slowed and when I touched my rim it was incredibly hot. Needless to say I never tried that again. I don't know what motivated me to do that in the first place. I think I was just on a really long hill and I just let go. My intention was to keep it around 30 mph and just coast because I didn't think that my body could go that fast becuase i'm not a trained cyclist. I thought that I would just know that I am going fast and be able to press the brakes and stop. Anyways, that's' the best description I can give of what going too fast (for my physical limitations) on a fixed feels like. For future reference for people that haven't done this yet, it's not a linear predictable progression as far as what/where or how fast your legs are going. It just starts happening and it doesn't feel like you're going much faster at a certain point. If you're on a long hill, either mount a speedometer on the bars and find your physical limit on the flats, or just be very careful. OH, I was riding shimano 105 pads and brakes at that time with the proper 105 lever too. BEST brakes i've ever ridden to this day. I have yet to try discs though. |
Originally Posted by ryan_rides
(Post 21094156)
Going almost 40mph with that small gearing I would be literally breathless. I feel like I'm spinning out getting up to 35mph on 48/15.
I only used to bmx, so maybe I just have loose hips or something? I don't train, I just ride without thinking about how fast i'm getting somewhere or what i'm doing other than riding. People go faster and maybe I was being kind of dramatic, but I really wanted to emphasize what it felt like to properly scare/warn other riders into not trying it without knowing their limits lol. I was only trying to go like 30 mph and coast/go kind of fast/blast a hill in a fun way but ended up going a lot faster without noticing. Crashes can get scary dangerous when you're going fast. Did it take you a long time to train to hit 35mph? |
Answering the OP's question directly, to avoid being chided by the self-appointed thread police:
I was always still in control at the fastest speed my track bike was capable of on steep descents. Riding with a 51/19 setup (42-inch gear, approximately), I hit around 225 rpm on descents many times over the decades. Scary but tolerable. The limiter with that gear ratio seemed to be wind resistance and not cadence. (Past tense because, at 68, I'm unwilling to test the limits the way I used to.) The trick seems to be to flick your feet forward with each pedal stroke and to let the pedals drag them around the rest of the way. Trying to pedal in circles at high cadences is a mug's game. |
Originally Posted by BicycleBicycle
(Post 21094126)
There was one situation where I came close...
I've hit about 36-37 mph (I had a gps speed thingy) on 45/16 gearing (I think that's near 190 rpm at the crank) and I was practically rubber legging it, but I was still (barely) able to keep up with the bike. It felt like my legs were not really attached to my body anymore and were just spinning on their own (with my input though). I was still able to positively apply forward motion with my leg muscles and feel them respond but it was getting to the point where I was feeling the cranks push back more than I wanted them too. I could feel my legs getting kind of numbish and they felt "liquid" and "heavy" , more like masses of gelatin than bones and muscle. Even 1 mph faster and I think that I would not have been able to push my legs anymore and the cranks would be pushing them instead. But instead of being nice and controllable, it felt like my legs would have just been wild spaghetti noodles flopping around. Luckily, this was when I wasn't riding brakeless and had a front brake. I tepidly tapped the brake out of fear of flipping over and there was almost no response, so I started to squeeze a little harder. Normally the front brake will send you over the bars if you hold them but I eventually squeezed them as hard as I could because I wasn't slowing down. It felt like my face was melting into my head and I had to use literally all of my strength to push against the bars to keep myself on the bike. I finally slowed and when I touched my rim it was incredibly hot. Needless to say I never tried that again. For future reference for people that haven't done this yet, it's not a linear predictable progression as far as what/where or how fast your legs are going. It just starts happening and it doesn't feel like you're going much faster at a certain point. If you're on a long hill, either mount a speedometer on the bars and find your physical limit on the flats, or just be very careful. In regards to this: Even 1 mph faster and I think that I would not have been able to push my legs anymore and the cranks would be pushing them instead.
Originally Posted by Trakhak
(Post 21094317)
Answering the OP's question directly, to avoid being chided by the self-appointed thread police:
The trick seems to be to flick your feet forward with each pedal stroke and to let the pedals drag them around the rest of the way. Trying to pedal in circles at high cadences is a mug's game. One technique I've read that helped me build up pedal speed is to think small circles. |
Originally Posted by Trakhak
(Post 21094317)
Answering the OP's question directly, to avoid being chided by the self-appointed thread police:
I was always still in control at the fastest speed my track bike was capable of on steep descents. Riding with a 51/19 setup (42-inch gear, approximately), I hit around 225 rpm on descents many times over the decades. Scary but tolerable. The limiter with that gear ratio seemed to be wind resistance and not cadence. (Past tense because, at 68, I'm unwilling to test the limits the way I used to.) The trick seems to be to flick your feet forward with each pedal stroke and to let the pedals drag them around the rest of the way. Trying to pedal in circles at high cadences is a mug's game. On that hill I needed to keep some level of control as there was a stop sign at the bottom. Ben |
I suppose you may eventually asplode or something. I just learned to spin, but also don't have any mountain descents to test the real limits on.
I've hit mid/upper 30's (mph) on descents here. Never had to use the brakes (of which my bike wisely has two) because drag was enough to keep my speed where I was. At the crank it came up 160-180 cadence, but at those speeds I really can't add so much power so just the air drag kept things in check. If I could have spun faster though I would have gone faster because I like going fast... |
I've ridden a few bigger descents brakeless ( i now ride with a front brake ) and It's not a fun time, I like to think I have a high tolerance for scary sh+t but I wouldn't do it again. But if the hills not too steep even a little resistance from the legs goes a long way.
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As previously stated, you will get bucked over the bars. I have also had my shoes ripped from my feet. Must have been quite the sight in both cases...
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Your hips will start bouncing and maybe you can't keep your arms straight, so you will turn your bars little to much and eat asphalt, if you pass the point of no return you can always jam your foot on your back tyre.
I don't think your pedals would rip, unless they are in bad condition, check out SF Mash video from 2007 , they are bombing hills with single leader straps. |
MY DUMB STORY :i have a WABI special ... 42x17 ... nitto urban bull horn ... front Brake ... my hands were close to the stem ...i came over a rise and began a a 2 tier descent 150 yds fairly shallow with 50 more yds of underpass steepness before flattening to a bridge ... i slammed hard trying to max out my down hill speed with no thought of the consequences of spinning way way out ... as i approached the bottom i felt like the frame was flexing but i think it was really my legs losing their ability to keep up with the crank speed ...i felt a wobble & some flex ... i went down fast and hard ... i had no time or skill to react or overreact on my brake ... i never had the sense that i was going to lose the bike ... i must have lost the front cause i landed hard on my right side ... the bike fell right and BENT the horn ... my helmetless head barely missed the bridge railing & curb ... in retrospect what stands out is how quick it happened > i'm an X moto track and have experienced high speed tank slappers hi & lo sides and this fall was more unforeseeable than any event that i had in 40+ yrs of motorcycling >>>> LESSON IS TO STAY WITHIN YOUR LIMITS :giver:
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I've found that I have two fairly discrete "zones" for pedaling smoothness - if I start spinning faster and faster and leave my comfort zone, I'll get a little bouncy as I transition into the fast-spin zone, but once I get to the fast-spin zone and commit to it, I can smooth it back out again. That's maybe a cadence of 140RPM+ or so for me and it involves more effort because I am putting more work into reducing the amount of weight I place on the saddle.
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