# 4-minute mile on a uni

This morning I finally cracked the 4-minute mile (not by much!).

Not surprisingly, I was on the Coker. I have 5" (125mm) cranks. This was
towards the end of a long, fast ride.

I would bet that Rodger Davies has done this many times on his 110s.
Anyone ever pull this off with the 125s?

Here are some #s to help those of us who can’t read the cycle computer
while riding:

I have found that a tenth of a mile requires 57-58 revolutions on the
Coker. Some basic math tells us that this comes out to a bit over a mile,
but there is 1-3% inefficiency due to wiggle and possibly to
under-inflation.

Assuming you can measure a tenth of a mile, here are some more #s:

Tenth time Mile Time Approx mph 30 sec 5 mins 12mph 27 sec 4:30 13.5 mph
24 sec 4 mins 15mph

Do these calcluations seem right (esp. the 57-58 revs)?

David

> I have found that a tenth of a mile requires 57-58 revolutions on the
> Coker. Some basic math tells us that this comes out to a bit over a
> mile, but there is 1-3% inefficiency due to wiggle and possibly to
> under-inflation.

David, Congrats on your fast mile. Here are some other points to consider.
You talk of a “1-3% inefficiency”. If you know the true diameter of the
wheel & can count revs, why does it matter how much distance is actually
traveled? Give yourself a break & count a “crooked mile” as a
mile…unless we are actually talking about a mile long course for the
sake of competition. Otherwise, we get into an argument about how
much variance there is between different riders,etc. After all, a
Coker is not a proper surveyor’s wheel. It’s much easier to just
“attempt” to properly calibrate the computer & take it’s word for
speed & distance or use a stop watch over a “known” mile.

> Assuming you can measure a tenth of a mile, here are some more #s:
>
> Tenth time Mile Time Approx mph 30 sec 5 mins 12mph 27 sec 4:30 13.5 mph
> 24 sec 4 mins 15mph
>
> Do these calcluations seem right (esp. the 57-58 revs)?
>
> David

These calculations might be correct for you & incorrect for others. I’ve
found that the Coker tire (with my calculations) rolls out to under 112"
or less than 36" diameter for the tire…did you do a roll out or
just the math based on a 36" wheel?

Anyway, I’ll try to go as fast as I can for a “mile” on my Coker(w/125
cranks & a stopwatch) & get back to you.

-Mark

>> I have found that a tenth of a mile requires 57-58 revolutions on the
>> Coker. Some basic math tells us that this comes out to a bit over a
>> mile, but there is 1-3% inefficiency due to wiggle and possibly to
>> under-inflation.
>
>David, Congrats on your fast mile. Here are some other points to
>consider. You talk of a “1-3% inefficiency”. If you know the true
>diameter of the wheel & can count revs, why does it matter how much
>distance is actually traveled? Give yourself a break & count a "crooked
>mile" as a
>mile…unless we are actually talking about a mile long course for the
> sake of competition. Otherwise, we get into an argument about how
> much variance there is between different riders,etc. After all, a
> Coker is not a proper surveyor’s wheel. It’s much easier to just
> “attempt” to properly calibrate the computer & take it’s word for
> speed & distance or use a stop watch over a “known” mile.
Yeah, I don’t feel like counting to 580 everytime I decide to clock
myself. Luckily there are a few spots where I can use marked miles to
assist. As you noted, these distances don’t totally square with the size
of the Coker tire (no, I didn’t actually measure it – just used 36" to
get a rough estimate), due to wiggle and other inefficiency, but I’m ok
with just using marked miles in order to assess distance. I set the cycle
computer to reflect a true mile rather than going by the size of the tire.
I can’t recall the exact #s but can get them if you want.
>
>
>> Assuming you can measure a tenth of a mile, here are some more #s:
>>
>> Tenth time Mile Time Approx mph 30 sec 5 mins 12mph 27 sec 4:30 13.5
>> mph 24 sec 4 mins 15mph
>>
>> Do these calcluations seem right (esp. the 57-58 revs)?
>>
>> David
>
>These calculations might be correct for you & incorrect for others. I’ve
>found that the Coker tire (with my calculations) rolls out to under 112"
>or less than 36" diameter for the tire…did you do a roll out or
>just the math based on a 36" wheel?
Well, whatever method, if a person can reliably measure a tenth of a mile,
then the chart above works. The question is whether 57 or 58 revs per
tenth is accurate. I would bet it’s pretty close.
>
>
>Anyway, I’ll try to go as fast as I can for a “mile” on my Coker(w/125
>cranks & a stopwatch) & get back to you.
>
>-Mark
Great. Good luck, and be safe. David

I measured the Coker circumference at 2.776m which converts to 35.345
inches in diameter. This was with a 160lb rider at 40psi, measured over 3
revolutions, I forget how many measurements, but I threw out the high and
low and averaged the rest. I was supported by a friend and pedaling
straight and smooth and slow. As always, YMMV!

—Nathan

nathan@movaris.com writes:
>I measured the Coker circumference at 2.776m which converts to 35.345
>inches in diameter. This was with a 160lb rider at 40psi, measured over 3
>revolutions, I forget how many measurements, but I threw out the high and
>low and averaged the rest. I was supported by a friend and pedaling
>straight and smooth and slow. As always, YMMV!
>
>—Nathan
>

Don’t forget that the circumf of the wheel does not change just from
compression. A rider will compress the wheel, of course, and this affects
height a tad, but the full sheel still has to go around, even if some of
it is compresed…so you should not try to convert diameter to circumf.
It definitely makes a difference, tho, if your wheel is a bit more or
less pumped.

The important info to me is that the circumf was measured at 2.776m –
this can be usued to calculate other data. I just would throw away the
diameter part.

david

Yes, the effective circumference is all that matters. You have to get the
cyclometer setting just right. I seem to remember measuring the diameter
of the wheel unweighted at 35.5", so even that is not a full 36". Right
now my tire is bald with threads showing, so that has a little affect too.

—Nathan

“David Stone” <dstone@packer.edu> wrote in message
news:fc.000f4e6700519311000f4e6700517472.519321@packer.edu
> nathan@movaris.com writes:
> >I measured the Coker circumference at 2.776m which converts to 35.345
> >inches in diameter. This was with a 160lb rider at 40psi, measured over
> >3 revolutions, I forget how many measurements, but I threw out the high
> >and low and averaged the rest. I was supported by a friend and pedaling
> >straight and smooth and slow. As always, YMMV!
> >
> >—Nathan
> >
>
> Don’t forget that the circumf of the wheel does not change just from
> compression. A rider will compress the wheel, of course, and this
> affects height a tad, but the full sheel still has to go around, even if
> some of it is compresed…so you should not try to convert diameter to
> circumf. It definitely makes a difference, tho, if your wheel is a bit
> more or less pumped.
>
> The important info to me is that the circumf was measured at 2.776m –
> this can be usued to calculate other data. I just would throw away the
> diameter part.
>
> david

Yes, the effective circumference is all that matters. You have to get the
cyclometer setting just right. I seem to remember measuring the diameter
of the wheel unweighted at 35.5", so even that is not a full 36". Right
now my tire is bald with threads showing, so that has a little affect too.

—Nathan

“David Stone” <dstone@packer.edu> wrote in message
news:fc.000f4e6700519311000f4e6700517472.519321@packer.edu
> nathan@movaris.com writes:
> >I measured the Coker circumference at 2.776m which converts to 35.345
> >inches in diameter. This was with a 160lb rider at 40psi, measured over
> >3 revolutions, I forget how many measurements, but I threw out the high
> >and low and averaged the rest. I was supported by a friend and pedaling
> >straight and smooth and slow. As always, YMMV!
> >
> >—Nathan
> >
>
> Don’t forget that the circumf of the wheel does not change just from
> compression. A rider will compress the wheel, of course, and this
> affects height a tad, but the full sheel still has to go around, even if
> some of it is compresed…so you should not try to convert diameter to
> circumf. It definitely makes a difference, tho, if your wheel is a bit
> more or less pumped.
>
> The important info to me is that the circumf was measured at 2.776m –
> this can be usued to calculate other data. I just would throw away the
> diameter part.
>
> david