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1. A 4 mile race I measured several years ago is changing its distance to 10km by adding an out-and-back leg near the 3 mile point of the original course. Do I have to ride the entire course, or just the new section?

2. I did one ride of a "10K" Saturday and found it was 35m short. For the second ride, should I ride the same route, or go back to where I know the correct start will be?
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Both questions require some judgement to assure the accuracy of your results. Here are my thoughts:

1. It's quite feasible to measure the out and back leg with the same accuracy as any other course, then simply add that distance to the overall course length. If you're comfortable with the exact route of the original course and you account for any distance that may be lost as the runners leave and return to the original course, I don't see a problem. On the other hand, riding a 10K measurement doesn't take that long and could serve to verify your original course.

2. If I could add 35m or more to the course using a steel tape, then I would take the second ride and if it compared within the 0.08%, then I would make the adjustment to the longer of the two course measurements. However, if I didn't have a straight section at the start/finish where I could make the adjustment with a tape, I'd do two more rides from the approximate location where the added 35m would put me.
Question 1: If the same measurer measured the 4 mile course I'd say go ahead and make the addition. I don't like the idea of somebody building a new 10k off somebody else's 4 mile course. A course should have one measurer.

Question 2: Since it appears the start is to be adjusted, begin at the finish line and measure the course in reverse. When the original start line is reached, stop and record a count. Go on to the new start line, mark it and take a count. Ride back to the old start line and take a count.

You now have two measurements of both the original course and the adjusted one.
Question 1: Pete Riegel described a possible procedure under "Addition to measurement" below on Nov 17 04.

Question 2:I notice that you converted your primary measurement unit (counts or revs) to meters. Also, Ron suggests taking measurements with a steel tape. These sort of procedures are described in the official on-line manual, but as I pointed out in MN a few months ago, conversions to standard measurement units are quite unnecessary.
Suppose I measured a an old course from start to finish and found it to be 400 counts too short. If I wished to make a correction at the start, I would turn around and measure back to the old start. I would then note the counts, and if I had more than 400 to go on this measurement, I would make the new start at the completion point. Otherwise, I would ride an addtional 400 counts and make the new start there. I would make an accurate correction without having to know what it is in meters or getting out the steel tape.
Last edited by neville
I always use meters because they are the same for everybody. Counts, revolutions - they change with the measurer and the day.

For clarity I believe that when one speaks of length, one should use solid standards.

I've seen confusion arise when somebody says a course is xxx counts long or short. That information tells me nothing.

If a course is measured on two separate occasions, counts for one occasion will not be the same as counts for the next. Only meters, feet or miles will do.
Last edited by peteriegel
MNF#1200 18May2005


For the first one, just measuring the out/back sounds fine ... but
you'll have to relocate mile marks so you'll be riding over the final 5
km anyway.

Second scenario: either way is fine.

Was thinking about a MNF item y'day while measuring. My measuring
bike is about 22 years old. It's an old Trek road bike. Does anybody
else use a bike that old? I've thought of updating ... maybe spending
around $500-750 but I'm trying to do less measuring so am having a
tough time justifying the cost.

I own a new Trek road bike ... you've heard of night/day differences
... well, this one is more like a black/white tv and plasma screen tv

Cheers, Scott

Q1. Addition to 4-mile course to make it up to 10km:

I would always re-measure the whole thing, but in UK we are only
mandated to do one measurement. In practice I would do one measurement
to get the overall length right, then measure again for splits.

In your case the first measurement could easily be done by cutting and
pasting the new bit. The second measurement would then be a complete
run over the new course, marking splits as you go (or noting landmarks
from which to establish split references).

Would this be allowable practice in US, or would you have to do the
adjustment first, and then two complete rides over the new course? If
your first new ride tallies with what you expect, from the amendments
you make, then isn't that sufficient?

Q2. Where to start for a corrected course:

It makes sense to me that you start where you think the correct start
should be. If you need to have the direct comparison for purposes of
documentation, then just make an additional stop at the old start line
(35m into the new course?)

Hugh Jones

1. I think I would set a couple of arbitrary points on either side of
where the out and back loop will be added. If one of the previously
measured points is one of them, all the better. Do two measurements
between points "A" and "B" on the old route, then calculate what needs
to be done on the out-and-back to extend the course from 4 miles to 10
km. Measure the new section twice. I would calculate the new course
length using the longer of the two measurements of the old course, and
the shorter of the two measurements of the addition. If everything's
within tolerance, calculate the new course length, adjust at the TP to
make it 10 km, and then reset the intermediate splits as necessary.

2. I would ride the course as you measured it last Saturday. If the
two measurements are within 0.08%, you have a legitimate course that
can be adjusted with a tape.

Jay Wight

1. I would recommend any "adjustment" like this be taken with lots of
caution. Are you absolutely certain the course is exactly as certified
several years ago? A call to your certifier to get input on
acceptability and some of the problems that might come up would be a
good idea. Given this scenario, I would ride the entire course to be
certain of the length.

1. Don't, don't, don't! measure to two different sets of marks. Ride
the second length the same as the first THEN adjust the course after
both ride lengths are completed. Making an adjustment then riding the
course a second time makes it difficult for the certifier to review the
measurement data and besides it is easier to adjust once and be done
with it.

Mike Wickiser

If you haven't measured this course for several years I would suggest
the entire course. You may choose to just measure the new section but
as a
certifier I would not certify it for 10 years from this years
but apply the 10 years from the older measurement. Riding the entire
twice would means the certified course should be good until 2015.
the race was originally a 4 mile race and you would only have the mile
splits, now that it is a 10 km you would want km splits. (Ya, right. I
won't hold my breath)

The course measurement data sheet requires two sets of data from the
course. If you add 35 m onto the distance for the first measurement
you can ride the second time from that adjusted temporary start. You
then lay out your splits on your second ride if you didn't stop at the
intermediate splits on your first ride. For a 10 km I would be tempted
do a third ride to check the km splits for any transposition errors.
If you
are not marking splits then I wouldn't ride the course the third time
the difference in distances was greater than 0.08%.

Bernie Conway

Question 1 If you are sure the original 4 mile course is unchanged I
think you can, within the rules, use that portion. I would not unless
it is in a heavy traffic area where you need a police escort or similar
problem. I would ride the full course adding the out and back. The
out and back leg's distance should be 1.1+ (half the extra distance) to
the turn-a-round. I would use the original mile marks to the out and
back leg and make new temporary mile marks and then use the original
finish. Made a second ride recording to the marks and then adjust the
turn-a-round and the subsequent mile marks.

Question 2 If you only did one ride, you don't know where the correct
start is, only close. The answer depends on the direction of the
ride. What is fixed, the start or the finish? If the finish is fixed
and you rode from finish to start, I would repeat the first ride.
Standard procedure, no complicating factors. But, it sound like the
start is fixed. If the start is fixed it is a little more work. I
would ride from your first ride's finish (start line), mark new mile
locations and also record the counter reading at the original mile
marks. This will give you reading to compare and close mile marks.
It is best to talk to the race director and explain the nature of
course measurement and that the propose route might not give him the
start and finish lines desired. The measurement should be made from
the fixed location and end at the floating location. If the course has
an out and back leg you can fix both the start and finish. I would
then ride from the start to the start of the out and back and then
return to the start as a second ride. Then I would ride from the
finish to the start of the out and back and return as second ride.
Then do the out and back leg and adjust as necessary.

Bill Grass

1. You just need to ride the new out and back leg and add it to the
previous route. The original route would need to be certified. In the
run it may be easier to ride the entire new route to lay out the
intermediate splits.

2. I prefer to do the second ride from the "correct" start. That way
intermediate marks will be in the "correct" location and will require
adjustment. Just need to keep the math straight when comparing the two
measurements for the allowable difference.

Dave Yaeger

My opinion on your two questions....

1. This raises the question as to how old a measurement can be and how
affects the "expiration date" for the certification. Suppose your 4
race was measured in 1997 and you simply use that measurement data and
measure only the added out/back segment making the distance total 10 km
2005. The certificate is issued in 2005. Is the expiration date the
end of
2015 or is it the end of 2007? This question has never really been

If you want to be on the safe side, then measure then entire 10K and
"ignore" the previous measurement of the 4 mile course. Then, there is
question of when the expiration date should be.

My opinion is that this is a matter of judgement by the
Did you examine the 4 mile course to determine whether or not there has
construction or some other modification of the physical route, i.e.,
can you
attest that the course has not changed since you measured it? If so,
then I
would judge that measuring only the added o/b section to make 10 km
produce a certificate issued in 2005 with an expiration date of 2015.
the 4 mile course has been modified, then obviously that portion should
remeasured (along with the added o/b section).

2. How do you know EXACTLY where the start should be until you make the
second ride? You really don't. Measure between the SAME start and
and THEN make any adjustments that are needed.

Ken Young

my quick answers are:

1. Use the old course and reference points to determine where your out
and back will turn around. Then ride the whole thing just to confirm
that you got it right. The only times when I wouldn't re-ride the
original 3 miles would be where that would be an enormous hassle or
dangerous. Around here, I avoid "excessive" rides in Rock Creek Park
and over a highway bridge, but for most other places, I think the added
confidence that you get from riding the entire thing at least once is
worth it.

2. You should ride the same "wrong" course twice. Compare your results,
then add the distance indicated by your best ride.

Bob Thurston

You did the right thing measuring the whole route rather than just the
addition. You should measure the original course again and make what
adjustments are necessary. "Measure the same marks twice."

Scott -

I had the same dilemma as you. I was tired of riding my old racing-style bike on measurements. Riding all hunched over was uncomfortable, but I had been using the bike for 10 years and was used to it. I was not sure how much longer I would be measuring.

I bit the bullet and bought a bike with twist-grip shifters and an upright riding posture. Spent an extra $25 on a nice cushy seat. That was 15 years ago.

Get the new bike. You will not be sorry.

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