My racing bike..help please?.

Question

I seem to have a problem, I don't know whether it's me or the bike. to be fair, I think it is me...

When I'm riding, I have no weight/downforce on my rear wheel. My weight is all over the front and middle, and regardless of speed, the slightest bump sends my rear wheel flying into the air (no seriously, it does).

Now my riding style itself is perfectly plausible, and everyone I've rode with rides the same, but they never have the back wheel problem,

I was just wondering - is there any way, without shifting my weight or riding style, to increase downforce on the rear end of my bike in order to prevent it coming up as much and to increase traction and therefore acceleration?

Sorry in advance if I don't make any sense.

Thanks in anticipation,

Stevee. x

Answer 1

Clearly, you have too much weight, too far forward.

Unfortunately, as Mr. G says, it is real hard to address this issue without seeing you on the bike.  Personally, I'd strongly recommend you take the bike to your local shop for a fitting.

In any case, my guess is you have too long a handlebar stem.  To compensate for the long stem, you probably have the the seat pulled as far forward as possible.  Thus, your weight is too far forward.

To be comfortable on a bike I like to use the Keith Bontrager fitting method.  As I understand his method, he ignores knee over pedal spindle position and focuses on proper weight distribution.  Peter White, a custom frame maker, advocates a similar method.  Here are some links:

http://www.sheldonbrown.com/kops.html

http://www.peterwhitecycles.com/fitting....

In any case, you should have the saddle nice and flat and positioned in a way that allows the weight of your bottom to be far enough back to largely counterbalance the weight of your torso when your hands are on the handlebars.  This allows you to bend forward to the handlebars without feeling much weight on your hands, arms and shoulders.  With the proper fore/aft saddle position, you should be able to ride somewhat comfortably, in a crouched position, handsfree.  If you feel a lot of strain on your back as you hold yourself up, your saddle is tipped forward or it needs to go further back.

When the saddle is in the correct fore/aft position and is nice and level, stem length should be pretty apparent.  The handlebars just need to be where you can naturally reach them from a crouched position, with your arms comfortably bent.  Generally, this will put the handlebars in a position where they block the view of your front axle.

I think at this point you'll also find you have better weight distribution on your bike.  For optimal power and climbing, you may find you want to have the seat a bit forward of the balance point or have a bit longer stem.  The good news is these slight tweaks should still keep your back wheel firmly planted as you ride.

Hope this helps.

Answer 2

You are going to have to shift your weight and riding style - no two ways about it!

It's hard to be exact without seeing you on your bike, but a few things that immediately spring to mind are:

Frame too big.

Seat too far forward.

Handlebars too low.

Or possibly, you have a very poor tyre!

Address the above first mate.

Short of an aero spoiler Formula 1 style - provided you attain a speed for downforces to occur!! (which you won't!) you have no other option!

Best of luck mate.

EDIT: I currently have my bike in my living room (just polished it - again!) and I have a test for you?

Sit on your bike in your normal riding style and take a look at your front wheel hub, Ideally the hub should be obscured by your handlebars, if your bars are way in front of your hub - Hey Presto!! a shorter stem may help!(not less than 90mm though)

What kind of saddle do you have? Us roadies usually ride with a long thin type and sit on the back of the saddle, if you have one of these humungous gel type things you will have to sit forward to move your legs (a rear saddle position is best)

EDIT: Brilliant!

Here is my best bike (although I have changed the bars for a compact version)

http://i297.photobucket.com/albums/mm236...

.

Answer 3

Racing bikes are typically a bit more twitchy than touring bikes, especially at low speeds.   Triathlon bikes even more so because of the steeper seat tube angles.  

What would make this worse than usual?  As Mr. G says, stem length.   Also, forward seat position.  Is your saddle all the way forward on the rails?  Is the mounting "knuckle" on the post forward instead of back?

It could be the frame itself.   A too small bike, or one that has a short top tube could be forcing more of your weight forward.