dstrong 

I pulled this off my Garmin from my ride earlier today. How do I figure out my wattage?



Oh...this was on my RockHopper, spinning out my 42/11....probably at about 180 rpm.

tallmantim

Worked out on 20" wheels - but I doubled the 20" as the radius rather than the diameter - so the gearing much be much taller...

If it was a 55 -> 11 -> 33 -> 11 that would give 23m per stroke and a required cadence of 167.

I think. LOL

darkadious

47 mph.

then again I'm just guessing.

Pedaleur

Is this with a drag chute, or not?

Metzinger

Another guy came along and went 167 using a similar strategy.
70 / 13 teeth connected to- 60 / 15 teeth, covering 114,2 ft distance with one pedal system rotation

But that was like, 15 years ago. I'm sure lots of the BF superstars could beat that today.

stevegreer

Personally, I doubt I will be able to get much over 30mph, if even that, on my current setup. I just bought a computer and installed it the other day, but haven't had a chance to ride since. So hopefully today or tomorrow I will be able to get out there and get some numbers.
I have a 23 year old steel frame Trek 400 which is set up more for touring than racing. It originally had a 46t big chainring when I got it, but I upgraded to a 50t my dad gave me. It also has a Maillard Helicomatic freehub, and the smallest cog that came on those is 14t.
So, 50t up front + 14t in the back= doubt I will get much over 30mph.

mattm

I think until you can hit 40 it's not worth bragging about..

That said, my best is in the 32-ish range (5-sec peak of ~1000w, 68 kg)... pretty weak.

1nsane

I managed to hit 142,7 mph. And I have proof!

https://ridewithgps.com/trips/47746

carpediemracing 

John Howard's bike gave him about 1 mph per rpm. He was towed to 40 mph. He did about 160 rpm at top speed. Fixed gear (!!).

He also went fast enough that the shraeder valve (car valve) depressed due to centrifugal force. He basically flatted at 100+ mph.

I didn't know about the 167 attempt. Cool. I think he used the same builder as Howard (?).

That would be awesome to try.

cdr

gsteinb

That's like making **** up to do just because you can. He got towed to 40 and then motopaced? The other guys go 80 in something that won't turn and you can't breath in? Brilliant. **** like this is why kids think math and science are stupid.

Metzinger

^Bah. Kids need heros. And who hasn't heard of Fred Rompelberg?

gsteinb

^if my kid's hero was a recumbent rider I'd send him to a reeducation camp.

Dheorl

I'm not convinced by this. How come it doesn't happen in cars?

I seriously hope your joking. Some kids will always think science is stupid because they are stupid and can't do it. For those that can are you saying the propect of making their bike go that fast won't get them interested? For most of the kids I know it would.

gsteinb

I am saying, for example, getting towed to speed and then moto pacing a dragster is stupid. I equate it with Sri Chimnoy's (sp?) absurd feats.

gsteinb

Yep

carpediemracing 

Not sure - smaller diameter? They checked the tires etc after the flat and found nothing wrong. They put some kind of locking nut (?) on the valve, maybe as simple as a valve cap (the articles never specified exactly what it was, or had any pictures). No more problems. I think they were basically relearning motorcycle technology, geometry, tires, etc.

Here is a mention in an SI article - apparently it was just a valve cap.
https://sportsillustrated.cnn.com/vau...04/2/index.htm

Bicycling Magazine did a big spread on the record ride. They also rode the bike, with much lower gears, at about 55 mph (they had/have a Cat 2 editor in those days), drafting behind a big truck (RV? UPS truck?). Said it was really, really hard, the bike wasn't easy to ride. Maybe at 150 it's different.

thump55

That's why I like Garmin...so easy to read. (Oh, and to figure out your wattage, simply take MPH x seconds)

wens

Most likely in cars/motorcycles the valve is at an angle relative to the centrifugal force, whereas on a bicycle it's typically parallel.

jefferee

Smaller diameter would actually create more force on the valve. (Centripetal acceleration: a=v^2/r)

Automotive valve stems usually point out at an angle, rather than right toward the hub. The rotation of the wheel would cause some friction between the valve core and the valve body. That friction would probably help hold the valve closed as well.

I'm a little surprised that a Schraeder valve spring isn't designed to be strong enough to hold the valve shut, but I guess the spring has to be weak enough to allow air to flow into the tire with a relatively small (~20-30 PSI?) pressure difference.

kensuf

It wasn't a sprint, but it was just under 27mph (26.9) for 55 minutes and 48 seconds.

Proof: https://www.floridacycling.com/result...2&eVclass=2086

A 29mph sprint seems pretty slow to me...

merlinextraligh

Which points out the BS of some people in the various sprint speed threads. You've won so much you're looking at a forced upgrade to Cat 3. Yet your sprint is pathetic by BF standards.

Grumpy McTrumpy

even mine is pathetic at 37.7, and I have exactly one upgrade point to his 26 or something. I must be much more aero though at 800w. 32 is leadout speed.

carpediemracing 

I might have missed something. If r was bigger, then you'd be dividing by a bigger number. The resulting a would be lower.

I'm not good at calculating stuff but I have a decent instinctive understanding of some things.

It was just a valve cap though.

The whole scene reminded me of another "relearning" scene, where experts in one field are novices in another. A guy came into the bike shop asking about gearing. He had an idea for an infinitely variable transmission for a bike (this was about 25 years ago, and I know it's been done, but back then it was novel). He had no idea what a freewheel was, nor a freehub or a cassette. He spent a good month of visits just learning the basics of how a bike worked. Then he started working on the transmission. Unfortunately it wasn't durable enough and they eventually canned it.

cdr

bmxsykes

I also heard it is common with the front wheels of the long dragsters with bicycle style front wheels. The stuff you learn from a cycling podcast.

StumpJumperFSR

Seems slow to me too since sprint runners can get up to 30mph. Just a guess though. I went like 45 mph down this really steep hill and that seemed fast. I just don't see me being able to sprint 45mph on the stumpy. A lot of the power is going to be lossed in the suspension too...especially when I have to stand up and mash down....