Advertise on Bikeforums.net



User Tag List

Page 1 of 3 123 LastLast
Results 1 to 25 of 66
  1. #1
    Calamari to go cc_rider's Avatar
    Join Date
    May 2005
    Location
    Falls Church, VA
    My Bikes
    Trek 750
    Posts
    3,103
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    I was wondering, how you find the % grade of the roads you ride?

    Is it published on a bicycle map?
    Do you calculate an average using distance and elevation on topo maps?
    Do you calculate it using a cyclocomputer and a GPS?
    Do you look at the hill and guess? (my current method)
    Is there some other device, bike mounted or handheld, for finding the slope of a hill?

    I have been wanting to find the grade some of the hills I ride. I have something I use for finding the slope of ramps and roofs on buildings, but I don't want to carry it around, stop, get off the bike mid-climb or mid-descent and measure.

    How do YOU find the % grade.
    Last edited by cc_rider; 06-24-05 at 01:47 PM.

  2. #2
    Specialized Member ChAnMaN's Avatar
    Join Date
    Nov 2003
    Location
    I live in a small town
    My Bikes
    2004 Specialized Allez
    Posts
    973
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    i dont know this to be a fact but if you have a cyclocomputer with altimiter abilities you might be able use the total distence traveled combined with the vertical distence traveled to make a triangle and then calculate the angle.

    just a guess, im sure there are much better ways.
    You can never be too Specialized
    Click here if any of the following apply to you:
    1 You dont like Specialized, 2 You drive a SUV, 3 Your name is George Bush

  3. #3
    RC2
    RC2 is offline
    Senior Member
    Join Date
    Jun 2005
    Location
    Fort Worth
    My Bikes
    Specialized, Moots, Bridgestone
    Posts
    415
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Rise over run... calculate the rise of a hill in ft (or meters, whatever) and divide by it's length. For instance, if you use an altimiter and measure a 100 ft altitude gain over 1000 feet, it's a 10% avg grade. In practice, once you know what 10% looks and feels like, you can subjectively gauge what 5% or 15% are. For reference, I've heard that typical freeway on/off ramps (to an overpass) are graded at 4%...not sure that's true or consistent.

  4. #4
    Ca-na-da? krazyderek's Avatar
    Join Date
    Nov 2004
    Location
    Dartmouth, NS, Canada
    My Bikes
    raleigh grand prix
    Posts
    2,024
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    i've wondered this aswell, i've thought of going to my local hardware store to see if they have any self leveling angel finder that might do the trick, although that would be off the bike.

    Maybe there's some type of gyro built into some computer out there, or i imagine an ALT computer would have the formulas built into it if you read thru the manual
    Cannondale '06 Synapse, Michelin Krylion Carbon's
    Cannondale '05 R1000 , Vittoria Rubino Pro Slick
    CycleOps PowerTap Pro
    Home made Free Motion Rollers

  5. #5
    Focus on the future alison_in_oh's Avatar
    Join Date
    Mar 2005
    Posts
    718
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    The accurate way seems to be getting topographic software and making a plot of the elevation change of your road.

    There's also cyclecomputers that will do the math of altitude vs. distance for you on the fly. But their altitude meters are calibrated by barometric pressure, so they'll vary to a certain extent.

    My method is to pester my most experienced roadie friend who's been on many a road with a marked grade, and to make him estimate the grades of nearby roads.

  6. #6
    Bananaed Brillig's Avatar
    Join Date
    Feb 2003
    Location
    Philly-ish
    My Bikes
    2001 Lemond Nevada City (only the frame remains)
    Posts
    6,426
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by cc_rider
    How do YOU find the % grade.
    Ask that guy in your cycling club who talks about all the grades of all the hills and divide his answer by 2.

    If once a man indulges himself in murder, very soon he comes to think little of robbing; and from robbing he comes next to drinking and Sabbath-breaking, and from that to incivility and procrastination.
    - Thomas De Quincey

  7. #7
    Out of Commission OC Roadie's Avatar
    Join Date
    Mar 2005
    Location
    SoCal
    My Bikes
    Felt FC, S-Works Roubaix, Epic Comp, Cyfac Proxidium
    Posts
    2,272
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    RC2 nailed it. Rise divided by run. Some cyclo computers with altimeters will give you a grade, but their sketchy at best. You can also use topo map or Dolorme software.

  8. #8
    Bananaed Brillig's Avatar
    Join Date
    Feb 2003
    Location
    Philly-ish
    My Bikes
    2001 Lemond Nevada City (only the frame remains)
    Posts
    6,426
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    If it's big enough you can go here http://www.topozone.com/ and calculate rise over run and get fairly close on an average grade. It's really tough to get accurate grades at different points without equipment or plotting the route in topographic software (which isn't always accurate either).
    If once a man indulges himself in murder, very soon he comes to think little of robbing; and from robbing he comes next to drinking and Sabbath-breaking, and from that to incivility and procrastination.
    - Thomas De Quincey

  9. #9
    Bananaed Brillig's Avatar
    Join Date
    Feb 2003
    Location
    Philly-ish
    My Bikes
    2001 Lemond Nevada City (only the frame remains)
    Posts
    6,426
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by ChAnMaN
    i dont know this to be a fact but if you have a cyclocomputer with altimiter abilities you might be able use the total distence traveled combined with the vertical distence traveled to make a triangle and then calculate the angle.
    Sort of. From there you'd need pythagorus to figure out the "run" part and then you can calculate the grade.

    Turn out something like:

    gradient = vertical/(Sqrroot(distance^2 - vertical^2))
    If once a man indulges himself in murder, very soon he comes to think little of robbing; and from robbing he comes next to drinking and Sabbath-breaking, and from that to incivility and procrastination.
    - Thomas De Quincey

  10. #10
    Specialized Member ChAnMaN's Avatar
    Join Date
    Nov 2003
    Location
    I live in a small town
    My Bikes
    2004 Specialized Allez
    Posts
    973
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by Brillig
    Sort of. From there you'd need pythagorus to figure out the "run" part and then you can calculate the grade.

    Turn out something like:

    gradient = vertical/(Sqrroot(distance^2 - vertical^2))
    I was thinking more like using Sin where x is the angle.

    Sin(x)=vertical/total....... x= (sin -1) vertical/total

    but the rise over run thing is much easier.
    You can never be too Specialized
    Click here if any of the following apply to you:
    1 You dont like Specialized, 2 You drive a SUV, 3 Your name is George Bush

  11. #11
    Theodore Roosevelt's idol TheKillerPenguin's Avatar
    Join Date
    Sep 2004
    Location
    Vagabond
    My Bikes
    Affirmative
    Posts
    9,160
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    For the major climbs, I take a "profile" picture of the grade at one point, using something that sticks straight up as a guide. I then figure out the grade using bitmap, and the rise/run thing. Obviously this only works on the climbs that have a fairly steady climb. For others, I have some topo maps of the area, but they only go down to 100ft isolines so it's hard to be 100% accurate with those. Some others, I just eyeball and use my past experience to guesstimate.
    Is trick from science!

  12. #12
    Senior Member
    Join Date
    Sep 2004
    Location
    Denver, Colorado
    My Bikes
    Trek 930 mutt (beater) Gary Fisher '98 Paragon
    Posts
    190
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by cc_rider
    I was wondering, how you find the % grade of the roads you ride?

    Is it published on a bicycle map?
    Do you calculate an average using distance and elevation on topo maps?
    Do you calculate it using a cyclocomputer and a GPS?
    Do you look at the hill and guess? (my current method)
    Is there some other device, bike mounted or handheld, for finding the slope of a hill?

    I have been wanting to find the grade some of the hills I ride. I have something I use for finding the slope of ramps and roofs on buildings, but I don't want to carry it around, stop, get off the bike mid-climb or mid-descent and measure.

    How do you find the % grade.
    I'm not a mathematician, so don't recall the elegant language for explaining this, but here is my attempt:

    First off: Percent slope (grade) = change in elevation in feet/ distance in feet (S=DE/L); 50% slope is one foot travelled vertically for two feet travelled horizontally. 100% slope is 1 foot up for 1 foot travelled.

    Degree of slope is often confused with percent of slope. Degree of slope is the measure of the number of degrees in the included angle, measured from level to the top of the hill (90 degrees is the angle when looking straight up, 0 degrees is dead level, 45 degrees is 1 foot up over 1 foot horizontal, or 100% slope). It is not at all uncommon to hear someone say something like "I was on a section of road that was 15 degrees up," which is 26.8 percent slope. Very Steep.

    For personal purposes, I take my data from one of a number of mapping programs that give elevation data. These days, I also use readings off a GPS unit (ETrex Legend). Elevation data taken from USGS maps is often not accurate enough to give a good read for specific hill grades- it's very hard to get a good starting and ending elevation from a map that only gives elevation in 20' intervals, as are USGA maps, typically. If your hill is short, accuracy sucks, as your potential for elevation error (as much as 40' off) has a more profound effect on your computation than when the error is incorporated into a big distance. So, accuracy of percent slope estimated from USGA gets better as distance increases.

    A clinometer (a hand held device, often integrated into a hand compass, but also available as a stand-alone unit) measures slope, and if used properly (measure from eye height to eye height- not eye height to ground) can be reasonable accurate (for bicylists), and is often used by foresters who need reliable estiation of grade values.

    Guessing is rarely accurate for most folks- 2% on pavement looks flat to many. On the other extreme, people often guess a steep section of road as being steeper than it is (a BF poster from a while back was guessing that the slope they were riding up was 30 degrees, or 33% slope- This will never happen on any engineered, paved road in the US, except on the inside of very tight hairpin turns- this is an impossibly steep grade for a road). If you're really good at estimation (because you're a surveyor, civil engineer, landscape architect, or someone else who deals with grade change on a regular basis) you've probably developed a good sense of grade, but this is a skill that takes considerable practice to develop.

    Is this any help?

  13. #13
    Senior Member
    Join Date
    Sep 2004
    Location
    Denver, Colorado
    My Bikes
    Trek 930 mutt (beater) Gary Fisher '98 Paragon
    Posts
    190
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    It took me so long to complete my answer that several others beat me to it. Whew boy.

  14. #14
    Overacting because I can SpongeDad's Avatar
    Join Date
    Jan 2005
    Location
    The Mean Streets of Bethesda, MD
    My Bikes
    Merlin Agilis, Trek 1500
    Posts
    4,552
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by ChAnMaN
    I was thinking more like using Sin where x is the angle.

    Sin(x)=vertical/total....... x= (sin -1) vertical/total

    but the rise over run thing is much easier.
    While I'm enough of a geek to have set up an Excel spreadsheet to calculate these things, just dividing the rise by the distance ridden (the hypotenuse) is pretty close to dividing the rise by the calculated horizontal run for most ridable grades.

  15. #15
    Senior Member
    Join Date
    Feb 2005
    Location
    Oklahoma
    My Bikes
    Trek 5500, Colnago C-50
    Posts
    9,201
    Mentioned
    2 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by ChAnMaN
    I was thinking more like using Sin where x is the angle.

    Sin(x)=vertical/total....... x= (sin -1) vertical/total

    but the rise over run thing is much easier.
    Your trig equation will give you degrees. Road grades are in % not degrees. A 45 degree angle is equal to 100% grade.

  16. #16
    Theodore Roosevelt's idol TheKillerPenguin's Avatar
    Join Date
    Sep 2004
    Location
    Vagabond
    My Bikes
    Affirmative
    Posts
    9,160
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    you can find the sides by working backwards through the problem.

    sin = O/H Therefore, Hsin = O, or H = O/sin

    Edit: with the lengths, you can find the %grade using rise/run.
    Last edited by TheKillerPenguin; 06-24-05 at 04:23 PM.
    Is trick from science!

  17. #17
    Specialized Member ChAnMaN's Avatar
    Join Date
    Nov 2003
    Location
    I live in a small town
    My Bikes
    2004 Specialized Allez
    Posts
    973
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by Al1943
    Your trig equation will give you degrees. Road grades are in % not degrees. A 45 degree angle is equal to 100% grade.
    ohh ok, that makes sense now. I guess I learn something new everyday.

    so if you know the angle then can you just divide by 45 to find the grade?
    You can never be too Specialized
    Click here if any of the following apply to you:
    1 You dont like Specialized, 2 You drive a SUV, 3 Your name is George Bush

  18. #18
    Senior Member
    Join Date
    Apr 2005
    Location
    Northern California
    Posts
    10,416
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by ChAnMaN
    ohh ok, that makes sense now. I guess I learn something new everyday.

    so if you know the angle then can you just divide by 45 to find the grade?
    tangent(angle) * 100 = grade
    tangent is not linear

  19. #19
    Specialized Member ChAnMaN's Avatar
    Join Date
    Nov 2003
    Location
    I live in a small town
    My Bikes
    2004 Specialized Allez
    Posts
    973
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by johnny99
    tangent(angle) * 100 = grade
    tangent is not linear
    what am i doing wrong?

    Tan(45)*100=161.977

    i thought a 45 degree angle was 100 % grade
    You can never be too Specialized
    Click here if any of the following apply to you:
    1 You dont like Specialized, 2 You drive a SUV, 3 Your name is George Bush

  20. #20
    Senior Member
    Join Date
    Apr 2005
    Location
    Northern California
    Posts
    10,416
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by ChAnMaN
    what am i doing wrong?
    Tan(45)*100=161.977
    i thought a 45 degree angle was 100 % grade
    tangent(45 degrees) = 1.0
    You probably forgot the difference between degrees and radians.

  21. #21
    Senior Member zonatandem's Avatar
    Join Date
    Dec 2003
    Location
    Tucson, AZ
    My Bikes
    ariZona carbon fiber tandem & single
    Posts
    10,110
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    There is a bicycle device available called and 'inclinometer'.

  22. #22
    Senior Member zonatandem's Avatar
    Join Date
    Dec 2003
    Location
    Tucson, AZ
    My Bikes
    ariZona carbon fiber tandem & single
    Posts
    10,110
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    Inclinometer info:
    Info@Velimpex.com
    Device clamps onto handlebar. Weighs 28 grams (1 ounce) and costs about $25. Will measure gradient -21 % to +21%.

  23. #23
    Senior Member mnutini's Avatar
    Join Date
    Feb 2005
    Posts
    179
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by zonatandem
    There is a bicycle device available called and 'inclinometer'.
    You can build your own.
    http://graphics.stanford.edu/~lucasp/bike-grade.html

    or do it by using a level
    http://www.paloaltobicycles.com/gradeslocal.html
    "If we don't change the direction we are headed, we will end up where we are going." - Chinese proverb

  24. #24
    Senior Member va_cyclist's Avatar
    Join Date
    Jun 2005
    Location
    Ashland, VA
    Posts
    1,345
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Not to be geometrically anal about it, but does measuring road distance give you an accurate rise-over-run? Specifically, the run part? If your hill forms a right triangle, then the short leg of the triangle is your rise, that's straightforward; but in a true slope calculation, the "run" is the bottom leg of the triangle, not the sloped leg (hypotenuse), which is what's being measured if you rely on your cyclocomputer's mileage. The difference is probably trivial, but might cause you to slightly underestimate the slope (too long a run for a given rise). Any math weenies have insight into this?

  25. #25
    Senior Member
    Join Date
    Apr 2005
    Location
    Northern California
    Posts
    10,416
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by va_cyclist
    Not to be geometrically anal about it, but does measuring road distance give you an accurate rise-over-run? Specifically, the run part? If your hill forms a right triangle, then the short leg of the triangle is your rise, that's straightforward; but in a true slope calculation, the "run" is the bottom leg of the triangle, not the sloped leg (hypotenuse), which is what's being measured if you rely on your cyclocomputer's mileage. The difference is probably trivial, but might cause you to slightly underestimate the slope (too long a run for a given rise). Any math weenies have insight into this?
    If the grade is less than 20% or so, the difference between horizontal and hypotenuse is probably significantly less than your measurement error. For very short steep hills, you can convert using trigonometry or pythagoras.

Page 1 of 3 123 LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •