squirrelly down descents

Daz4ever

So firstly, I'm not a hardcore rider, mostly weekend rides 40-80 miles at an average of 17mph solo. I have a top of the line 14 pound cannondale road bicycle that Ive decided to sell since Im not working at the moment and instead will be using an older model trek madone 4.5 with mid range parts weighing a little under 19 pounds. I don't notice a difference on the flats for the most part, and very little when climbing. I do notice a big difference when descending however. The bicycle doesn't feel as stable at high speed and the braking power is very inferior to the cannondale. The tires are thinner on the trek. The wheels are bontrager race clinchers compared to krysium es anniversary edition clinchers on the cannondale. I'm not exactly sure if its just a mental thing or if the cannondale really is just a more stable bicycle?

HTupolev

Braking power:

Try cleaning the rims and pads. Wipe off the brake track with a cloth with some solvent, even something weak like isopropyl would do the trick. Scrub off the brake pads. See if that makes a difference.

To make sure you're getting the most out of a brake system, replace the cables and housing, and install some grippy pads. I think Shimano has done a pretty good job with their current-gen higher-end ones (i.e. BR-5800 R55C4), and Kool Stop Salmons are effective.

Handling:

What do you mean by "stable"? Are you getting a shimmy on the Trek (i.e. the steering starts oscillating at certain speeds), or does it just feel twitchy?

neeb

It could be any number of things - different geometry affecting steering feel (especially trail, which is a product of the head tube angle and the fork offset), frame stiffness (especially at the front end), different bike setup affecting your weigh distribution on the bike, the different tyres you mention, or even just the poorer braking affecting your confidence. Impossible to say from that information really. But some bikes definitely do feel better descending than others.

Daz4ever

The trek actually is a better fit for me. The stem on the cannondale was a bit long. More of a racing position. I think its wobble when descending, or maybe there was strong cross winds. I'll definitely try replacing the brakes soon to see if that helps.

HTupolev

Daz4ever wrote:

I think its wobble when descending, or maybe there was strong cross winds.

Shimmy and crosswinds are easy to tell apart. Crosswinds cause erratic deflections, almost random. Shimmy is a steady oscillation, just about sinusoidal.

The other thing that people talk about as "squirrelly" on descents is twitchy steering. In particular, the steering on bikes with relatively low trail won't stiffen up much with speed, so the bike will more readily do stuff if you're not smooth and stable on the handlebars while descending.

Daz4ever

What does low-trail mean on a bicycle? I think its the twitchy feeling in the handlebars. Usually I feel most comfortable descending in an aero position on the hoods, but since I didn't feel like I had as much control with braking as before I was in the drops most of the time. I usually feel ok in the drops so it shouldn't have been an issue switching up though.

HTupolev

Daz4ever wrote:

What does low-trail mean on a bicycle?

Visualize a line down the steering axis of your bicycle, and imagine where it touches the ground. The distance between this point and the contact patch of your front tire is your bicycle's "trail." It's a figure that says a lot about how a bicycle handles.

http://davesbikeblog.squarespace.com/bl ... story.html

fat daddy

Daz4ever wrote:

The trek actually is a better fit for me. The stem on the cannondale was a bit long.

Well thats one thing that will make the Cannondale more stable, The longer the stem the more steering input is required to turn the bike .. also the less twitchy it will feel.

every movement of the bike is transferred though your arms if you have them close together and near to the pivot point then a smaller movement will have an effect .... if you were to stick whopping 480mm bars on and a 130mm stem all the little changes in movement wouldnt result in much in your feeling. compared to a 380mm bar and a 60mm

ayjaycee

Have you tried switching the brakes and wheels from Cannondale to Trek. Swap the brakes and test followed by the wheels and see if there is any difference. (Or have I missed something?)

Mikey23

I have had exactly this issue regardless of the make of bike. My roubaix would start speed wobbling on any fast descents regardless of conditions which i found very scary. My tarmac on the other hand is rock solid and very stable and i can descend at speed and in complete confidence. Im a bit of a wuss at downhills so this didnt help!

fenix

Have you used the cannondale more than the trek ? And descents round here now are a lot trickier with wet leaves than they were in the Summer ?

davep1

Is the frame ok? No cracks in it?