Cycling and bicycle discussion forums. 
   Click here to join our community Log in to access your Control Panel  


Go Back   > >

Singlespeed & Fixed Gear "I still feel that variable gears are only for people over forty-five. Isn't it better to triumph by the strength of your muscles than by the artifice of a derailer? We are getting soft...As for me, give me a fixed gear!"-- Henri Desgrange (31 January 1865 - 16 August 1940)

User Tag List

Reply
 
Thread Tools Search this Thread
Old 11-17-10, 12:46 PM   #1
illdthedj
Senior Member
Thread Starter
 
illdthedj's Avatar
 
Join Date: Mar 2010
Location: Modesto, Ca
Bikes: klein quantum, litespeed tuscany, bianchi pista concept, centurion comp ta, centurion super le mans, traitor ringleader
Posts: 2,280
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Does longer rake change top tube angle?

was just thinking about forks and their relationship to the frame....

now obviously, if you take two forks of same rake but one is longer than the other, the longer will result in making the top tube of the frame a bit more sloped.

however, what im wondering is this:
if two forks of the same length (i guess axle to crown) but of different rake were on the same frame, would the top tube stay the same on both, or would the one with bigger rake slope the top tube forward? like say, you had a fork with a 30mm rake. the top tube is perfectly level with this fork. you then replace fork with an exactly same length fork but has a 45mm rake. would the top tube then dip slightly forward? i guess opposite of sloping, like pursuit esque...

i guess im thinking since the front axle is farther forward, the frame would dip down a bit....
illdthedj is offline   Reply With Quote
Old 11-17-10, 12:59 PM   #2
ianjk
:)
 
Join Date: Nov 2006
Location: duluth
Bikes: '07 Pista, '09 Fantom Cross Uno, '8? Miyata, '67 Stingray, '0? Zoo mod trials, Tallbike, Chopper, '73 Schwinn Collegiate, '67 Triumph Chopper, '69 CB350, '58 BSA Spitfire, '73 CB450
Posts: 3,392
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Top tube angle is a frame measurement. The angle of your top tube relative to the ground changes.
ianjk is offline   Reply With Quote
Old 11-17-10, 01:00 PM   #3
illdthedj
Senior Member
Thread Starter
 
illdthedj's Avatar
 
Join Date: Mar 2010
Location: Modesto, Ca
Bikes: klein quantum, litespeed tuscany, bianchi pista concept, centurion comp ta, centurion super le mans, traitor ringleader
Posts: 2,280
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by ianjk View Post
Top tube angle is a frame measurement. The angle of your top tube relative to the ground changes.
so are you saying longer rake changes the top tube angle?
illdthedj is offline   Reply With Quote
Old 11-17-10, 01:02 PM   #4
Scrodzilla
There goes Tokyo
 
Scrodzilla's Avatar
 
Join Date: May 2009
Location: San Diego, CA
Bikes: EAI Bare Knuckle, 1975 Raleigh Pro Track
Posts: 26,476
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 39 Post(s)
Pretty sure that's what he meant. Yes, it will change the angle at which your entire frame sits in relation to the ground. Very, very slightly.
__________________
__________________________________
Scrodzilla is offline   Reply With Quote
Old 11-17-10, 01:02 PM   #5
Scrodzilla
There goes Tokyo
 
Scrodzilla's Avatar
 
Join Date: May 2009
Location: San Diego, CA
Bikes: EAI Bare Knuckle, 1975 Raleigh Pro Track
Posts: 26,476
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 39 Post(s)
Quote:
Originally Posted by ianjk View Post
Top tube angle is a frame measurement. The angle of your top tube relative to the ground changes.
Pretty sure that's what he meant. Yes, it will change the angle at which your frame sits in relation to the ground. Very, very slightly.

If you come across a fork capable of changing your frame's actual geometry, please let us know.
__________________
__________________________________
Scrodzilla is offline   Reply With Quote
Old 11-17-10, 01:08 PM   #6
Kayce
Senior Member
 
Kayce's Avatar
 
Join Date: Aug 2010
Location: St Louis
Bikes:
Posts: 1,846
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
The entire bike will be at a different angle relitive to the ground. The seat tube and headtubes will be less steep, the top tube will slope back, as will the chainstays. None of those things would effect the performance of the frame outright, but it will be a totally different handling bike due to the change in trail, and the movement of the bottom bracket.
Kayce is offline   Reply With Quote
Old 11-17-10, 01:11 PM   #7
illdthedj
Senior Member
Thread Starter
 
illdthedj's Avatar
 
Join Date: Mar 2010
Location: Modesto, Ca
Bikes: klein quantum, litespeed tuscany, bianchi pista concept, centurion comp ta, centurion super le mans, traitor ringleader
Posts: 2,280
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
oh haha yes thats what i meant, relative to the ground.

basically, i got a traitor ringleader frame only for a super good deal. however no fork. the fork the frame usually comes with results in level top tube. a fork i am looking at is very slightly longer, but has slightly more rake.
was told by traitor dude longer fork would mean slightly sloped top tube on the complete bike, but i was thinking the longer rake would subtract some of that slope.
illdthedj is offline   Reply With Quote
Old 11-17-10, 01:12 PM   #8
illdthedj
Senior Member
Thread Starter
 
illdthedj's Avatar
 
Join Date: Mar 2010
Location: Modesto, Ca
Bikes: klein quantum, litespeed tuscany, bianchi pista concept, centurion comp ta, centurion super le mans, traitor ringleader
Posts: 2,280
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by Kayce View Post
The entire bike will be at a different angle relitive to the ground. The seat tube and headtubes will be less steep, the top tube will slope back, as will the chainstays. None of those things would effect the performance of the frame outright, but it will be a totally different handling bike due to the change in trail, and the movement of the bottom bracket.
wait you are saying the top tube would slope BACK with longer rake? wouldn't it slope FORWARD? me confuse.
illdthedj is offline   Reply With Quote
Old 11-17-10, 01:17 PM   #9
Leukybear
THE STUFFED
 
Leukybear's Avatar
 
Join Date: Oct 2009
Location: Sandy Eggo, CA
Bikes: Sworks Venge; Rock Lobster; EAI Bareknuckle
Posts: 12,119
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 27 Post(s)
Quote:
Originally Posted by Scrodzilla View Post
If you come across a fork capable of changing your frame's actual geometry, please let us know.
Low rider bike fork.
Leukybear is offline   Reply With Quote
Old 11-17-10, 01:31 PM   #10
Scrodzilla
There goes Tokyo
 
Scrodzilla's Avatar
 
Join Date: May 2009
Location: San Diego, CA
Bikes: EAI Bare Knuckle, 1975 Raleigh Pro Track
Posts: 26,476
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 39 Post(s)
That would still only change the angle of the frame relative to the ground.
__________________
__________________________________
Scrodzilla is offline   Reply With Quote
Old 11-17-10, 09:02 PM   #11
osiris419
Senior Member
 
osiris419's Avatar
 
Join Date: Nov 2009
Location: Tewksbury MA
Bikes: Giant OCR (SRAM Equipped), Trek 1100 (Ultegra), Cannondale R600, Cannondale Super V800 Raven, Univega Cross/gravel Grinder, SE Draft, Jamis Dakota Elite hardtail, BSD TrailOrPark BMX
Posts: 306
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
when the front wheel is more forward of the head tube it will lower the front end of the bike but if you have longer fork legs the drop is not as much. It's like motorcycle building, a chopper has extreme rake and really long fork legs but the front of the bike is actually higher, if you shorten up the forks you will lower the front end.
osiris419 is offline   Reply With Quote
Old 11-17-10, 09:17 PM   #12
Squirrelli
GONE~
 
Join Date: Apr 2010
Bikes:
Posts: 6,757
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
David Moulton did a pretty good job at explaining how fork rake/trail works with the frame.

Also, a change in axle to crown length will affect the head tube angle too. It's not necessary a change in geometry, but more or less, change in handling as Kayce have stated.
Squirrelli is offline   Reply With Quote
Old 11-17-10, 09:32 PM   #13
AEO
Senior Member
 
AEO's Avatar
 
Join Date: Jun 2007
Location: A Coffin Called Earth. or Toronto, ON
Bikes: Bianchi, Miyata, Dahon, Rossin
Posts: 12,258
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
if you use different sized tires on the front and back, it'll change the top tube angle.
__________________
Food for thought: if you aren't dead by 2050, you and your entire family will be within a few years from starvation. Now that is a cruel gift to leave for your offspring. ;)
http://sanfrancisco.ibtimes.com/arti...ger-photos.htm
AEO is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

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



All times are GMT -6. The time now is 09:36 PM.