Go Back  Bike Forums > Bike Forums > Bicycle Mechanics
Reload this Page >

Correct way to measure a fork

Notices
Bicycle Mechanics Broken bottom bracket? Tacoed wheel? If you're having problems with your bicycle, or just need help fixing a flat, drop in here for the latest on bicycle mechanics & bicycle maintenance.

Correct way to measure a fork

Old 02-12-18, 09:31 PM
  #26  
Senior Member
 
Join Date: Apr 2009
Location: New Rochelle, NY
Posts: 38,544

Bikes: too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter

Mentioned: 139 Post(s)
Tagged: 1 Thread(s)
Quoted: 5703 Post(s)
Liked 2,432 Times in 1,345 Posts
Originally Posted by Kontact
Sorry, I just re-read, and I misunderstood what you were measuring at each part, even if I got the overall idea.

BUT, it still suffers what CNY and I pointed out - that you are trying to get accurate hypotenuses from very acute triangles measured with crude tools. With angles of just a few degrees, the amount of error even a slight inaccuracy in length measuring or angle measuring produces is giant. Too much to get a useful rake out of.
I guess that you still haven't figured out that I never bothered with the angle. Just two very simple linear measurements, so simple that anyone who can't do them has no business worrying about fork rake.

Can you measure 15-20mm along a length of string?
Can you measure from a string to a tube?
can you do some simple, very basic arithmetic?

If you answered yes, you can measure fork rake. If you answered no to any of those, there's no reason to bother.

BTW - I invite anybody reading this who has a fork, axle (or chopstick,or knitting needle), string, a ruler and/or tape measure, to give it a try and report back. My money's on you.
__________________
FB
Chain-L site

An ounce of diagnosis is worth a pound of cure.

Just because I'm tired of arguing, doesn't mean you're right.

“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN

WARNING, I'm from New York. Thin skinned people should maintain safe distance.
FBinNY is offline  
Old 02-12-18, 10:50 PM
  #27  
Mechanic/Tourist
 
Join Date: Apr 2007
Location: Syracuse, NY
Posts: 7,522

Bikes: 2008 Novara Randonee - love it. Previous bikes:Motobecane Mirage, 1972 Moto Grand Jubilee (my fave), Jackson Rake 16, 1983 C'dale ST500.

Mentioned: 10 Post(s)
Tagged: 0 Thread(s)
Quoted: 486 Post(s)
Liked 11 Times in 11 Posts
Well, I not about to argue with my own original statement that there are multiple ways to accomplish the goal. I had to sketch out FB's method to understand it (I think). I've done a rough representation below. The advantage is that it requires no special tools. The disadvantage is that it relies on multiple measurements that are difficult to make accurately, one of which is multiplied significantly. I ran some rough figures, and a mere 1mm difference in measurement B alone makes for over a 2.5 mm difference in calculated rake.
Attached Images
File Type: png
Calculate fork rake.png (11.0 KB, 63 views)

Last edited by cny-bikeman; 02-16-18 at 06:14 PM. Reason: Corrected to add 1/2 of fork column diameter
cny-bikeman is offline  
Old 02-12-18, 11:07 PM
  #28  
Senior Member
 
Join Date: Apr 2009
Location: New Rochelle, NY
Posts: 38,544

Bikes: too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter

Mentioned: 139 Post(s)
Tagged: 1 Thread(s)
Quoted: 5703 Post(s)
Liked 2,432 Times in 1,345 Posts
Yes, you're sketch is wrong, but you did clarify that A & C are along the string, so you have it.

BTW - the triangles aren't congruent, they're similar.

Note- this is my method for measuring with the fork off the bike, but I wouldn't take the fork off to do it this way. On the bike, any variation of the flip the fork and average is faster and comparably accurate (if done right).

So, how about a bet.

We'll need a fork of known rake and a volunteer who doesn't know the rake. Let him measure the rake by the various methods proposed. I'll bet a night's beer supply that he comes closest to the right answer by my method.

Any takers?
__________________
FB
Chain-L site

An ounce of diagnosis is worth a pound of cure.

Just because I'm tired of arguing, doesn't mean you're right.

“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN

WARNING, I'm from New York. Thin skinned people should maintain safe distance.
FBinNY is offline  
Old 02-12-18, 11:22 PM
  #29  
Mechanic/Tourist
 
Join Date: Apr 2007
Location: Syracuse, NY
Posts: 7,522

Bikes: 2008 Novara Randonee - love it. Previous bikes:Motobecane Mirage, 1972 Moto Grand Jubilee (my fave), Jackson Rake 16, 1983 C'dale ST500.

Mentioned: 10 Post(s)
Tagged: 0 Thread(s)
Quoted: 486 Post(s)
Liked 11 Times in 11 Posts
Well, I only have MS Paint and wanted to get to bed, so I did what I could. Of course as soon as my head hit the pillow I realized I had left out the fork column diameter (radius) correction.

Yes, they are similar trianglesl

Well, a night's beer supply for me would cost you nothing, as I'm a wine drinker, but I'll bite anyway, as I'd just like to see the results.
cny-bikeman is offline  
Old 02-12-18, 11:25 PM
  #30  
Senior Member
 
Join Date: Apr 2009
Location: New Rochelle, NY
Posts: 38,544

Bikes: too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter

Mentioned: 139 Post(s)
Tagged: 1 Thread(s)
Quoted: 5703 Post(s)
Liked 2,432 Times in 1,345 Posts
Originally Posted by cny-bikeman
Yes, they are similar trianglesl

Well, a night's beer supply for me would cost you nothing, as I'm a wine drinker, but I'll bite anyway, as I'd just like to see the results.
Beer, wine, fair enough for me (as long as we're talking lower shelf bar wine). I also drink wine, so we can agree on a Merlot or Cabernet and bet that.

I'll trust you; do you have a fork, and someone to use as the test subject? If so, your word is fine with me. If not, we need someone to step up and set it up for us.
__________________
FB
Chain-L site

An ounce of diagnosis is worth a pound of cure.

Just because I'm tired of arguing, doesn't mean you're right.

“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN

WARNING, I'm from New York. Thin skinned people should maintain safe distance.
FBinNY is offline  
Old 02-12-18, 11:38 PM
  #31  
Senior Member
 
Join Date: Apr 2009
Location: New Rochelle, NY
Posts: 38,544

Bikes: too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter

Mentioned: 139 Post(s)
Tagged: 1 Thread(s)
Quoted: 5703 Post(s)
Liked 2,432 Times in 1,345 Posts
One last note.

Here's my easy way to measure rake on an installed fork. You'll need a wheel small enough that it'll clear the downtube when the fork is reversed, a piece of string and a fine tip marker.

Install the wheel and tie the string around the rim (anyplace) with a big loop so it can center nicely when pulled.

Turn the fork forward, and pull the string to a reference mark like the spindle center on the left crank. (let the fork and wheel float to whatever position they want) Pull it taut and mark it. Flip the fork and repeat, marking the new position.

Measure the distance between the dots, divide by two and you have the rake.

The reason I like this method is that it eliminates the need to judge when the fork is truly squared up at 180°.
__________________
FB
Chain-L site

An ounce of diagnosis is worth a pound of cure.

Just because I'm tired of arguing, doesn't mean you're right.

“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN

WARNING, I'm from New York. Thin skinned people should maintain safe distance.
FBinNY is offline  
Old 02-13-18, 01:26 AM
  #32  
Senior Member
 
Kontact's Avatar
 
Join Date: Apr 2011
Posts: 6,825
Mentioned: 41 Post(s)
Tagged: 0 Thread(s)
Quoted: 4260 Post(s)
Liked 1,457 Times in 950 Posts
Originally Posted by FBinNY
Yes, you're sketch is wrong, but you did clarify that A & C are along the string, so you have it.

BTW - the triangles aren't congruent, they're similar.

Note- this is my method for measuring with the fork off the bike, but I wouldn't take the fork off to do it this way. On the bike, any variation of the flip the fork and average is faster and comparably accurate (if done right).

So, how about a bet.

We'll need a fork of known rake and a volunteer who doesn't know the rake. Let him measure the rake by the various methods proposed. I'll bet a night's beer supply that he comes closest to the right answer by my method.

Any takers?
I'm your huckleberry.


I started with a 1" carbon threadless road fork from a Bianchi. I put an axle size rod through the dropouts, made a loop in some kite string and pulled the string taught over the top of the steerer and taped it in place on the back side so it would stay. I picked a point above the crown race and just below a sticker on the steerer as my measuring point.

The distance to the measuring point is 6.198", and the inside of the string was at .308" from the steerer on a line perpendicular to the steerer. I took a second measure mid string thickness, which came to .325". The total steerer to axle length was right on 31.5".

To make things easier, I dumped the numbers into this tool, and used the resulting angles to construct the larger triangle with a 31.5" hypotenuse. The resulting lower legs were 1.563" and 1.65" respectively. The steerer was 1", so I added .5" to both for rakes of 2.063" and 2.15" inches. Multiplied by 25.4 to get I got 52.4mm and 54.61mm.

https://www.calculator.net/triangle-c...ts=d&x=74&y=23


Next, I got a stainless small pot from the good folks at Farberware and a rubber tipped clamp. I put the pot on my glass desk top, put the steerer horizontally across the pot with the lip of the crown race against the lip of the pot, and leveled the fork rake down as best I could, then clamped the steerer mid span to the pot and glass. I then took a piece of stiff junk mail and marked the center of the dropout on the vertically held junk mail on both dropouts. I got lucky and they were exactly the same.

Then I did the same thing, but with the rake pointing up. I took the same junk mail and made marks the same way as before. This time right and left were different because I did not get them perfectly level. No matter, I averaged the two rake-up marks and made another mark between them.


Then I took out the calipers and measured between the average upper mark and lower mark. That came to 3.375". Divide that by two is 1.6875", and multiply that by 25.4 gave me 42.8625mm.

During all this screwing around I looked at the sticker for the first time since I pulled it out of bike. It says "Offset____43.0".




As CNY and I made clear earlier, trying to make and use exact measurements from acute triangles has problems. The triangles I measured in the first test were only about 3° on top. Measuring from a round tube to a string took patience and three hands, and the string itself was very hard to judge its real location. A finer string would make it less of question where to measure, but both my bottom and mid string measures produced results that were much larger than the real rake. Working backwards, my measure to the string should have been only .234", not .308". That .075 difference changed the top angle by nearly .7°.

The pot, clamp and cardstock method was faster to set up, was very repeatable, easy to measure and required virtually no math - had I a metric caliper I would have only had to divide the result by two. And I was accurate to the manufacturer's label by .1375mm.


There is no question which one I'd use next time.



Of course, I could have made this all up just to sound smart.

Last edited by Kontact; 02-13-18 at 01:46 AM.
Kontact is offline  
Old 02-13-18, 07:03 AM
  #33  
Mechanic/Tourist
 
Join Date: Apr 2007
Location: Syracuse, NY
Posts: 7,522

Bikes: 2008 Novara Randonee - love it. Previous bikes:Motobecane Mirage, 1972 Moto Grand Jubilee (my fave), Jackson Rake 16, 1983 C'dale ST500.

Mentioned: 10 Post(s)
Tagged: 0 Thread(s)
Quoted: 486 Post(s)
Liked 11 Times in 11 Posts
Originally Posted by FBinNY
Beer, wine, fair enough for me (as long as we're talking lower shelf bar wine). I also drink wine, so we can agree on a Merlot or Cabernet and bet that.

I'll trust you; do you have a fork, and someone to use as the test subject? If so, your word is fine with me. If not, we need someone to step up and set it up for us.
No fork - all I have is a scattering of small, mostly obsolete and obscure parts, as I've been out of the biz for almost longer than I was in it - which is saying something. Maybe Andrew can help. I'm unconcerned about fairness even if he does it himself, and I like the fact that he happens to be about halfway in between us geographically.
cny-bikeman is offline  
Old 02-13-18, 07:12 AM
  #34  
Senior Member
 
Join Date: Apr 2009
Location: New Rochelle, NY
Posts: 38,544

Bikes: too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter

Mentioned: 139 Post(s)
Tagged: 1 Thread(s)
Quoted: 5703 Post(s)
Liked 2,432 Times in 1,345 Posts
No problem with Andrew, if he's willing.
__________________
FB
Chain-L site

An ounce of diagnosis is worth a pound of cure.

Just because I'm tired of arguing, doesn't mean you're right.

“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN

WARNING, I'm from New York. Thin skinned people should maintain safe distance.
FBinNY is offline  
Old 02-13-18, 08:11 AM
  #35  
Mechanic/Tourist
 
Join Date: Apr 2007
Location: Syracuse, NY
Posts: 7,522

Bikes: 2008 Novara Randonee - love it. Previous bikes:Motobecane Mirage, 1972 Moto Grand Jubilee (my fave), Jackson Rake 16, 1983 C'dale ST500.

Mentioned: 10 Post(s)
Tagged: 0 Thread(s)
Quoted: 486 Post(s)
Liked 11 Times in 11 Posts
Rats - once again I did not refresh my screen, so I missed Kontact's post. I'm a bit hurt that he did not try my method but the fork rotation method he used successfully makes sense to me, and I'm not surprised at the accuracy. We can still try to rope in Andrew if you like - I already sent him a PM.

Last edited by cny-bikeman; 02-13-18 at 08:17 AM.
cny-bikeman is offline  
Old 02-13-18, 09:15 AM
  #36  
Senior Member
 
Join Date: Apr 2009
Location: New Rochelle, NY
Posts: 38,544

Bikes: too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter

Mentioned: 139 Post(s)
Tagged: 1 Thread(s)
Quoted: 5703 Post(s)
Liked 2,432 Times in 1,345 Posts
Originally Posted by cny-bikeman
Rats - once again I did not refresh my screen, so I missed Kontact's post. I'm a bit hurt that he did not try my method but the fork rotation method he used successfully makes sense to me, and I'm not surprised at the accuracy. We can still try to rope in Andrew if you like - I already sent him a PM.
Sure, let's five it a fair shot.

However, I repeat that there's more than one way to do most jobs, including this one. The fact that one method works, doesn't imply that others don't also.

As you know, good mechanics keep more than one arrow in the quiver, and will choose one method or another depending on the tools or materials at hand. In fact, even knowing 5 ways to do something, they may sometimes find themselves having to improvise a sixth.
__________________
FB
Chain-L site

An ounce of diagnosis is worth a pound of cure.

Just because I'm tired of arguing, doesn't mean you're right.

“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN

WARNING, I'm from New York. Thin skinned people should maintain safe distance.
FBinNY is offline  
Old 02-13-18, 12:17 PM
  #37  
Senior Member
 
Kontact's Avatar
 
Join Date: Apr 2011
Posts: 6,825
Mentioned: 41 Post(s)
Tagged: 0 Thread(s)
Quoted: 4260 Post(s)
Liked 1,457 Times in 950 Posts
Originally Posted by FBinNY
One last note.

Here's my easy way to measure rake on an installed fork. You'll need a wheel small enough that it'll clear the downtube when the fork is reversed, a piece of string and a fine tip marker.

Install the wheel and tie the string around the rim (anyplace) with a big loop so it can center nicely when pulled.

Turn the fork forward, and pull the string to a reference mark like the spindle center on the left crank. (let the fork and wheel float to whatever position they want) Pull it taut and mark it. Flip the fork and repeat, marking the new position.

Measure the distance between the dots, divide by two and you have the rake.

The reason I like this method is that it eliminates the need to judge when the fork is truly squared up at 180°.
This isn't going to work because strings stretch, making your measurement inaccurate.

You could use the string to center the wheel and then use a yardstick to actually measure.

Last edited by Kontact; 02-13-18 at 12:28 PM.
Kontact is offline  
Old 02-13-18, 12:34 PM
  #38  
Mechanic/Tourist
 
Join Date: Apr 2007
Location: Syracuse, NY
Posts: 7,522

Bikes: 2008 Novara Randonee - love it. Previous bikes:Motobecane Mirage, 1972 Moto Grand Jubilee (my fave), Jackson Rake 16, 1983 C'dale ST500.

Mentioned: 10 Post(s)
Tagged: 0 Thread(s)
Quoted: 486 Post(s)
Liked 11 Times in 11 Posts
Well, again I did say from the beginning that there would be several ways to accomplish the goal, and it wasn't my suggestion to determine which would be the best...and a medium quality Merlot is fine with me.

p.s. I wanted to clarify that I never had a question about angles, etc. Once I understood your method it was clear that the 90 degree part of the triangles was simply assumed - no need to layout or measure.
cny-bikeman is offline  
Old 02-13-18, 12:40 PM
  #39  
Senior Member
 
Kontact's Avatar
 
Join Date: Apr 2011
Posts: 6,825
Mentioned: 41 Post(s)
Tagged: 0 Thread(s)
Quoted: 4260 Post(s)
Liked 1,457 Times in 950 Posts
Originally Posted by cny-bikeman
There would be lots of ways to do it, the primary object being to measure the distance between a line drawn down the middle of the fork column and the center of the dropout. Actually, I just thought of a method while typing this which I believe would work.
  1. Place the fork on a level surface, pointing the rake down.
  2. Take a short level that has a groove for placing it on a pipe (common on 9" levels) and place it on the fork column, tape it if you like. If a threaded fork make sure the level is secure against the unthreaded portion.
  3. Lift the fork column up until it is level.
  4. Measure the distance from the bottom of the column where the level is to the table/surface (at the end OK if unthreaded).
  5. Add 1/2 of the fork column O.D. where the level is, subtract distance from the dropout center to the table.
I would think this method would be accurate within 1 mm.

I may be old-school, but my mechanic's brain is still working!
The problem with this method is that it relies on your accurate judgement of the bubble being truly centered, and you have to do that twice - once for table and once for the fork, which doubles your possible error. I'd suggest taking the level part out of it:

It would be better to place an object under the steerer tube that is easy to change the height, and then move it up and down the steerer, measuring the height of the horizontal steerer off the table until that height is the same wherever the object is placed. At that point the steerer and table are parallel to each other, and you can take your measurements, adding for steerer centerline and subtracting for the dropout.

This method also avoids trying to get a 2 foot level to remain firmly in contact with 6 inches of steerer.
Kontact is offline  
Old 02-13-18, 12:57 PM
  #40  
Mechanic/Tourist
 
Join Date: Apr 2007
Location: Syracuse, NY
Posts: 7,522

Bikes: 2008 Novara Randonee - love it. Previous bikes:Motobecane Mirage, 1972 Moto Grand Jubilee (my fave), Jackson Rake 16, 1983 C'dale ST500.

Mentioned: 10 Post(s)
Tagged: 0 Thread(s)
Quoted: 486 Post(s)
Liked 11 Times in 11 Posts
Originally Posted by Kontact
The problem with this method is that it relies on your accurate judgement of the bubble being truly centered, and you have to do that twice - once for table and once for the fork, which doubles your possible error. I'd suggest taking the level part out of it:

It would be better to place an object under the steerer tube that is easy to change the height, and then move it up and down the steerer, measuring the height of the horizontal steerer off the table until that height is the same wherever the object is placed. At that point the steerer and table are parallel to each other, and you can take your measurements, adding for steerer centerline and subtracting for the dropout.

This method also avoids trying to get a 2 foot level to remain firmly in contact with 6 inches of steerer.
Yes, I can see your point, although I suspect the method is still sufficiently accurate. Yes, one could accomplish the goal of parallel by measuring, although multiple measurements introduce error as well. Also, one could simply take whatever position the bubble takes on the table and try for the same position on the fork column. I did suggest a 9" level. As I already noted your method seems effective, and it has the benefit of not having to clamp the fork, as others have suggested.
cny-bikeman is offline  
Old 02-13-18, 01:19 PM
  #41  
Senior Member
 
Kontact's Avatar
 
Join Date: Apr 2011
Posts: 6,825
Mentioned: 41 Post(s)
Tagged: 0 Thread(s)
Quoted: 4260 Post(s)
Liked 1,457 Times in 950 Posts
Originally Posted by cny-bikeman
Yes, I can see your point, although I suspect the method is still sufficiently accurate. Yes, one could accomplish the goal of parallel by measuring, although multiple measurements introduce error as well. Also, one could simply take whatever position the bubble takes on the table and try for the same position on the fork column. I did suggest a 9" level. As I already noted your method seems effective, and it has the benefit of not having to clamp the fork, as others have suggested.
I don't know how much measuring you actually have to do with my latest suggestion. Until you get the adjustable pylon really close to the correct height, you'll be able to see the steerer end bob up and down as you slide the pylon along the steerer. When you have an adjustment that is really close to parallel to the table and the steerer no longer moves, you would break out the calipers to confirm what you're seeing. If it is, that's the measurement you'd use for your calculations. Other that that difference, it is just like your level idea - I'm just saying to use the object you'd need to lift the fork in step 3 as both your parallel confirmation device and measuring tool.

The problem with "whatever the bubble takes" is that this becomes a judgment call, not a measure. A digital clinometer would at least tell you what degree both are off from level. And you still have the problem of measuring level on a short length of round tubing. Especially if there is bulging around the lip of the steerer from a pipe cutter - that will make the level useless.

It is do-able, but if you truly have a mystery fork you aren't going to know whether you have level measuring errors or not - you'll just end up with an rake that you suppose is right.

Last edited by Kontact; 02-13-18 at 02:12 PM.
Kontact is offline  
Old 02-16-18, 05:54 PM
  #42  
Senior Member
 
Kontact's Avatar
 
Join Date: Apr 2011
Posts: 6,825
Mentioned: 41 Post(s)
Tagged: 0 Thread(s)
Quoted: 4260 Post(s)
Liked 1,457 Times in 950 Posts
Originally Posted by FBinNY
Sure, let's five it a fair shot.

However, I repeat that there's more than one way to do most jobs, including this one. The fact that one method works, doesn't imply that others don't also.

As you know, good mechanics keep more than one arrow in the quiver, and will choose one method or another depending on the tools or materials at hand. In fact, even knowing 5 ways to do something, they may sometimes find themselves having to improvise a sixth.
Did either of you ever try your methods?
Kontact is offline  
Old 02-16-18, 05:56 PM
  #43  
Senior Member
 
Join Date: Apr 2009
Location: New Rochelle, NY
Posts: 38,544

Bikes: too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter

Mentioned: 139 Post(s)
Tagged: 1 Thread(s)
Quoted: 5703 Post(s)
Liked 2,432 Times in 1,345 Posts
Originally Posted by Kontact
Did either of you ever try your methods?
Waiting on the results from a neutral party.
__________________
FB
Chain-L site

An ounce of diagnosis is worth a pound of cure.

Just because I'm tired of arguing, doesn't mean you're right.

“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN

WARNING, I'm from New York. Thin skinned people should maintain safe distance.
FBinNY is offline  
Old 02-16-18, 06:42 PM
  #44  
Mechanic/Tourist
 
Join Date: Apr 2007
Location: Syracuse, NY
Posts: 7,522

Bikes: 2008 Novara Randonee - love it. Previous bikes:Motobecane Mirage, 1972 Moto Grand Jubilee (my fave), Jackson Rake 16, 1983 C'dale ST500.

Mentioned: 10 Post(s)
Tagged: 0 Thread(s)
Quoted: 486 Post(s)
Liked 11 Times in 11 Posts
FB:
Well, I thought I PM'd Andrew, but I don't see the message in my Sent box. I'll do it again, but need to clarify which of the "various methods" you were referring to when you bet yours would be the most accurate. We will eliminate Kontact's latest, as that came after your post. What I see before you posted the challenge were two by Kontact (posts #8 and #5) from me (#14), and a link to one by Spoonrobot (#20). I'm looking forward to getting this going, as I'm short on Merlot. I don't even care that mine probably won't be the most accurate, as the only criteria is that yours is not!
cny-bikeman is offline  
Old 02-16-18, 06:51 PM
  #45  
SE Wis
 
dedhed's Avatar
 
Join Date: Apr 2005
Location: Milwaukee, WI
Posts: 10,516

Bikes: '68 Raleigh Sprite, '02 Raleigh C500, '84 Raleigh Gran Prix, '91 Trek 400, 2013 Novara Randonee, 1990 Trek 970

Mentioned: 40 Post(s)
Tagged: 0 Thread(s)
Quoted: 2731 Post(s)
Liked 3,361 Times in 2,034 Posts
Couldn't a guy just take a plumb bob and tilt the bike up on the front wheel until the bob string is parallel with the head tube and measure from the string over to the drop out with a ruler?
dedhed is offline  
Old 02-16-18, 07:15 PM
  #46  
Mechanic/Tourist
 
Join Date: Apr 2007
Location: Syracuse, NY
Posts: 7,522

Bikes: 2008 Novara Randonee - love it. Previous bikes:Motobecane Mirage, 1972 Moto Grand Jubilee (my fave), Jackson Rake 16, 1983 C'dale ST500.

Mentioned: 10 Post(s)
Tagged: 0 Thread(s)
Quoted: 486 Post(s)
Liked 11 Times in 11 Posts
Yes he could. Have to judge parallel, though, and head tube is not very long.
cny-bikeman is offline  
Old 02-16-18, 07:21 PM
  #47  
Advocatus Diaboli
 
Sy Reene's Avatar
 
Join Date: Feb 2015
Location: Wherever I am
Posts: 8,611

Bikes: Merlin Cyrene, Nashbar steel CX

Mentioned: 14 Post(s)
Tagged: 1 Thread(s)
Quoted: 4717 Post(s)
Liked 1,526 Times in 997 Posts
I was thinking something involving 2 laser pointers, a sharpie, and a ruler. However, I don't know what to do with them.
Sy Reene is offline  
Old 02-17-18, 08:08 AM
  #48  
SE Wis
 
dedhed's Avatar
 
Join Date: Apr 2005
Location: Milwaukee, WI
Posts: 10,516

Bikes: '68 Raleigh Sprite, '02 Raleigh C500, '84 Raleigh Gran Prix, '91 Trek 400, 2013 Novara Randonee, 1990 Trek 970

Mentioned: 40 Post(s)
Tagged: 0 Thread(s)
Quoted: 2731 Post(s)
Liked 3,361 Times in 2,034 Posts
Originally Posted by cny-bikeman
Yes he could. Have to judge parallel, though, and head tube is not very long.
You could use the edge and add 1/2 the diameter
dedhed is offline  
Old 02-17-18, 09:52 AM
  #49  
Senior Member
 
Kontact's Avatar
 
Join Date: Apr 2011
Posts: 6,825
Mentioned: 41 Post(s)
Tagged: 0 Thread(s)
Quoted: 4260 Post(s)
Liked 1,457 Times in 950 Posts
Originally Posted by dedhed
You could use the edge and add 1/2 the diameter
All of the methods that rely on getting a very small angle correct over a long span appear to be terribly inaccurate. Why don't you give your's a try and see if you end up with numbers that are off the geometry chart for your bike?
Kontact is offline  
Old 02-17-18, 09:58 AM
  #50  
Advanced Slacker
 
Kapusta's Avatar
 
Join Date: Feb 2017
Posts: 6,187

Bikes: Soma Fog Cutter, Surly Wednesday, Canfielld Tilt

Mentioned: 26 Post(s)
Tagged: 0 Thread(s)
Quoted: 2749 Post(s)
Liked 2,516 Times in 1,422 Posts
Originally Posted by Sy Reene
I was thinking something involving 2 laser pointers, a sharpie, and a ruler. However, I don't know what to do with them.
I was thinking zip-ties, duct tape, and spray paint, but I like your list better. Sounds more brainy.
Kapusta is offline  

Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service -

Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.