why??

i recently acquired a 2011 specialized langster. the bike had very few miles on it when i got it.  i have a terrible habit of riding with no hands.  the first time i let go of the handlebars on this bike, it immediately started to lean left and i had to grab the bars to regain control.  ive had a bike to this to me in the past, but it was an old crappy bike, unlike this new one.

what could be causing it?  everything - the wheels, the bars, the seat - appear to be sstraight and flush. there is nothing else in there that would make it obvious.  i have been able to ride it no hands since, but i do have to counter balance a bit.

help me understand...

Views: 1893

▶ Reply to This

Replies to This Discussion

Permalink Reply by Gerry G on March 20, 2012 at 6:37am

Shamelessly cut from here: http://sheldonbrown.com/brandt/pull-side.html


Subject: Bike pulls to one side 
From: Jobst Brandt

For less than million dollar bikes this is easy to fix, whether it corrects the cause or not. If a bike veers to one side when ridden no-hands, it can be corrected by bending the forks to the same side as you must lean to ride straight. This is done by bending the fork blades one at a time, about 3 mm. If more correction is needed, repeat the exercise.

The problem is usually in the forks although it is possible for frame misalignment to cause this effect. The kind of frame alignment error that causes this is a head and seat tube not in the same plane. This is not easily measured other than by sighting or on a plane table. The trouble with forks is that they are more difficult to measure even though shops will not admit it. It takes good fixturing to align a fork because a short fork blade can escape detection by most measurement methods. Meanwhile lateral and in-line corrections may seem to produce a straight fork that still pulls to one side. However, the crude guy who uses the method I outlined above will make the bike ride straight without measurement. The only problem with this is that the bike may pull to one side when braking because the fork really isn't straight but is compensated for lateral balance.

This problem has mystified more bike shops because they did not recognize the problem. Sequentially brazing or welding fork blades often causes unequal length blades and bike shops usually don't question this dimension. However, in your case I assume the bike once rode straight so something is crooked.

More stolen from here: http://sheldonbrown.com/frame-spacing.html

Spreading a Front Fork

A front fork can't be spread the same way as the rear of a frame, because you can't lever against the seat tube. Generally, the front fork is spread by pulling the blades apart from one another. Better-equipped bike shops have jigs to align fork blades. This can be done with a hub axle, placing axle nuts in between the fork blades. Fine adjustments may be made with a rubber mallet.

Checking a front fork

A bike shop checks symmetry of a front fork with its special jig, but symmetry can also be checked roughly by installing a wheel into the fork and testing whether the rim centers between the fork blades. To be sure that the wheel itself is centered, turn it over and try it the other way. The rim should be the same distance from each fork blade after being turned over. Minor adjustments for symmetry can be made with a rubber mallet. Testing for symmetry of a front fork is more difficult than with the rear of a frame.

Get'her straight Iggy.  I too luv no hands some times.  Gives your back a stretch.  

Permalink Reply by Far'arned Retrogrumpalunkus #63 on March 20, 2012 at 7:59am

You can make a bike ride close to straight with this procedure but I bet the wheel will not stay centered in the fork when it is done.  It'll look noticably off-center and the brake will probably have to be canted to the side to compensate.

Of course the wheel could be re-dished and re-centered (to the fork, not itself) but that will only make the problem come back again -maybe worse.

Sometimes the only way to fix a a bent fork without an expensive jig on a road bike is to buy a new fork.    I have a home-made jig that works fairly well on a 3-speed like a Raleigh with conservative rake angles and generous and stable steering.  I've never been successful bending a fork back to straight on a road bike with a more quick-steering steering geometry.  I can get it to steer straight or I can get the wheel centered -I just can't do both.  Sun Lite replacement forks are under $20 and are fairly light and well-made all-chromed forks.  It's the easiest  way that I've found...

Permalink Reply by Liz on March 20, 2012 at 10:15am

The fork on this bike is Carbon fiber DO NOT BEND THE FORK!!!!!!

Permalink Reply by Gerry G on March 20, 2012 at 10:31am

Tech specs reporting steel fork here:

http://www.specialized.com/ja/en/bc/SBCBkModel.jsp?sid=11Langster&a...

If it were carbon you would consider using a bigger hammer.  ; )

Liz said:

The fork on this bike is Carbon fiber DO NOT BEND THE FORK!!!!!!

Permalink Reply by Far'arned Retrogrumpalunkus #63 on March 20, 2012 at 10:50am

Oiy, if it is a carbon fork either it is straight or it is garbage...

Permalink Reply by Liz on March 20, 2012 at 10:50am

This one says carbon, Iggy doesn't say which model he has. I think the one you linked to is a japanese model.

http://www.specialized.com/us/en/bc/SBCBkModel.jsp?spid=38444

http://www.specialized.com/us/en/bc/SBCProduct.jsp?spid=62142&s...
"Specialized FACT carbon, carbon fiber legs, aluminum crown and steerer"



Steel Driver said:

Tech specs reporting steel fork here:

http://www.specialized.com/ja/en/bc/SBCBkModel.jsp?sid=11Langster&a...

If it were carbon you would consider using a bigger hammer.  ; )

Liz said:

The fork on this bike is Carbon fiber DO NOT BEND THE FORK!!!!!!

Permalink Reply by Far'arned Retrogrumpalunkus #63 on March 20, 2012 at 10:58am

Possible the alloy crown or steer tube could be bent.  That should be pretty obvious just from looking at it after pulling it out of the frame -plus it would most likely bind if that were the case. 

Permalink Reply by Gerry G on March 20, 2012 at 11:20am

Liz nice catch!  See I went looking for steel and found steel.  How subjective of me.

HEYYY IGGY DON'T PERSUADE ANYTHING JUST YET!  ; )

Liz said:

This one says carbon, Iggy doesn't say which model he has. I think the one you linked to is a japanese model.

Liz said:

The fork on this bike is Carbon fiber DO NOT BEND THE FORK!!!!!!

Permalink Reply by Far'arned Retrogrumpalunkus #63 on March 20, 2012 at 11:30am

Steel is Real.

Permalink Reply by Gerry G on March 25, 2012 at 2:58pm

Hi iggi,

How's the bike?  

bump

Permalink Reply by igz on July 17, 2012 at 5:46am

so, my leanings continued for a while still without explanation. i messed with the wheels, i messed with the seat.  two weekends ago, i rode the bike to starved rock.  as my hands got a bit tired, i sat upright into a no hands dance. bike rode perfectly straight. i even took a video of it while riding.  i thought it might have been the weight of the pack on back.  but i took it off and tried without it.  bike still rode straight.

bike is now sold, and this will forever be a mystery.

Permalink Reply by Julie Aberman (Hochstadter) on July 17, 2012 at 5:52am

can you at least share the video with us? It can be embedded via youtube or vimeo I know. 

RSS

Groups

© 2008-2016   The Chainlink Community, L.L.C.   Powered by

Disclaimer  |  Report an Issue  |  Terms of Service