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

Bicycle Computer Question

Search
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.

Bicycle Computer Question

Thread Tools
 
Search this Thread
 
Old 04-17-04, 08:51 PM
  #1  
Senior Member
Thread Starter
 
mindbogger's Avatar
 
Join Date: Jul 2003
Posts: 933
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Bicycle Computer Question

I just bought a Specialized Team Wireless and have a quesiton that has been bothering me all day. In the manual it does not say where to mount it on the fork.

So basically my question is, if the mount is towards the bottom and the magnet is closer to the hub, won't the speed read a bit faster since it is spinning faster. Where as, if it was mounted at the top, you would get a slower reading?

My theroy on how it works is that since it is wireless, if judges the distance bewteen the computer and the fork and does all these calulations to produce the speed. Correct me if i am wrong and i am sure i am wrong.

I would love to get an accurate reading so if anyone has any experience I would really appreciate it.

Thanks
mindbogger is offline  
Old 04-17-04, 09:00 PM
  #2  
Former Hoarder
 
55/Rad's Avatar
 
Join Date: Jan 2004
Location: Portland & Yachats, OR
Posts: 11,734

Bikes: Seven Axiom, Felt Z1, Dave Moulton Fuso

Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 16 Post(s)
Liked 7 Times in 7 Posts
Originally Posted by mindbogger
So basically my question is, if the mount is towards the bottom and the magnet is closer to the hub, won't the speed read a bit faster since it is spinning faster. Where as, if it was mounted at the top, you would get a slower reading?
The computer measures the time it takes for the magnet to make one revolution, not the distance it travels around, so it reads the same no matter where you put it. Think of it this way - the spoke end at the hub takes the same amount of time to make one revolution as it's opposite end at the rim.

I've got mine mounted near the hub - less distance for the magnet to travel = less likely to fall off.

55/Rad
55/Rad is offline  
Old 04-17-04, 09:03 PM
  #3  
Senior Member
 
Join Date: Dec 2003
Location: Guelph, Canada
Posts: 304

Bikes: Kona Kikapu & Cannondale r400

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
it doesnt matter where you mount it on the fork because the spoke goes through just as fast. the way it calculates speed is by obtaining rpms. it takes your tire size (which you input) and calculates how far/fast etc. you are going.
RobotSonic is offline  
Old 04-17-04, 09:18 PM
  #4  
Senior Member
Thread Starter
 
mindbogger's Avatar
 
Join Date: Jul 2003
Posts: 933
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Originally Posted by 55/Rad
Think of it this way - the spoke end at the hub takes the same amount of time to make one revolution as it's opposite end at the rim.
This is what i am having trouble understanding.


Ohh wait i jsut got it! Ohh man boy and i stupid! This is all starting to make sense! Thanks for the reply!
mindbogger is offline  
Old 04-19-04, 10:37 AM
  #5  
cycles per second
 
Gonzo Bob's Avatar
 
Join Date: Oct 2003
Location: Minnesota
Posts: 1,930

Bikes: Early 1980's Ishiwata 022 steel sport/touring, 1986 Vitus 979, 1988 DiamondBack Apex, 1997 Softride PowerWing 700, 2001 Trek OCLV 110

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 44 Post(s)
Liked 71 Times in 48 Posts
Originally Posted by RobotSonic
it doesnt matter where you mount it on the fork because the spoke goes through just as fast. the way it calculates speed is by obtaining rpms. it takes your tire size (which you input) and calculates how far/fast etc. you are going.
Actually, even though the RPMs are the same, the magnet goes much faster out by the rim. Some sensors have trouble picking up the magnet when it's out by the rim and is going at a much higher linear speed. The solution in this case is to put the sensor and magnet much closer to the hub.
Gonzo Bob is offline  
Old 04-19-04, 02:16 PM
  #6  
Senior Member
Thread Starter
 
mindbogger's Avatar
 
Join Date: Jul 2003
Posts: 933
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Originally Posted by Gonzo Bob
Actually, even though the RPMs are the same, the magnet goes much faster out by the rim. Some sensors have trouble picking up the magnet when it's out by the rim and is going at a much higher linear speed. The solution in this case is to put the sensor and magnet much closer to the hub.
hmm the range from the handle bar to the hub is not within the optimal tranmission range. I was thinking of putting it near the middle of the fork but realized it is very dangerous for the sensor so I went with mounting it near the brake post. In case of a fall, my brakes would be more likely to take the damage.
mindbogger is offline  
Old 04-19-04, 03:35 PM
  #7  
Senior Member
 
Join Date: Oct 2002
Location: Laguna Hills, OC, California
Posts: 265
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Mount the pickup as close to the computer as you can. You will save yourself lot of headache caused by intermitency. The location of the pickup with respect to the calculated speed and distance is immaterial, because the circumference of the wheel doesn't change with the position of the pickup. The computer just uses the pre-programmed wheel circumference and pulses from the pickup to calculate everything else it outputs.
ComPH is offline  
Old 04-19-04, 07:04 PM
  #8  
Just ride.
 
roadbuzz's Avatar
 
Join Date: Oct 2000
Location: C-ville, Va
Posts: 3,259
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 6 Post(s)
Liked 1 Time in 1 Post
To some extent, the location of the magnet is governed by the width of the wheel, i.e. the distance of the spokes from the fork.
roadbuzz is offline  
Old 04-19-04, 07:10 PM
  #9  
The Red Lantern
 
Rev.Chuck's Avatar
 
Join Date: Apr 2003
Location: Raleigh NC
Posts: 5,965
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
I mount the wireless units as close to the computer as the wheel/fork spacing will allow. It gives better transmission.
__________________
Are you a registered member? Why not? click here to register. Its free, and only takes 27 seconds!
Help out the forums, abide by our community guidelines.

I am in the woods and I have gone crazy.
Rev.Chuck is offline  
Old 04-19-04, 07:17 PM
  #10  
DEADBEEF
 
khuon's Avatar
 
Join Date: Aug 2002
Location: Catching his breath alongside a road near Seattle, WA USA
Posts: 12,234

Bikes: 1999 K2 OzM, 2001 Aegis Aro Svelte

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
Likes: 0
Liked 6 Times in 4 Posts
Originally Posted by roadbuzz
To some extent, the location of the magnet is governed by the width of the wheel, i.e. the distance of the spokes from the fork.
Yes, but depending on the sensor band design, you may be able to compensate by rotating the sensor inwards so as to maintain the proper magnet-sensor gap.
__________________
1999 K2 OzM 2001 Aegis Aro Svelte
"Be liberal in what you accept, and conservative in what you send." -- Jon Postel, RFC1122
khuon is offline  
Old 04-19-04, 07:23 PM
  #11  
The Rabbi
 
seely's Avatar
 
Join Date: Apr 2004
Posts: 5,123
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 16 Post(s)
Likes: 0
Liked 3 Times in 3 Posts
On the Team wireless I run the transmitter unit at near the bottom of my fork, the magnet in towards the hub and the computer on my bars without any problems whatsoever in a few hundred miles of abuse.
seely is offline  

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



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.