Frame Flex

I have been riding my Specialized Sirrus for about a month now. I think overall it's a decent bike. Economics played a role in what I could afford, and I "picked" this bike over Trek for whatever reason.

I generally ride as hard as I can which comes out to 17mph+ on average. One thing I have never noticed on a bike before, or even thought of, was frame flex. Last week coming off a hill going close to 30 and hitting a turn, I swear I felt some flex which felt odd to me.

Is that normal in an aluminum frame. Is it something I should be concerned about? I'm not worried about breakage, but am now wondering if I married my bike purchase to my riding style.

 

A flat bar hybrid going 17 MPH average? You're killin' it! Good job.

What do you weigh?

Can you describe the flex...fork, rear triangle, head tube, bottom bracket sway or bounce? Could it be your wheels? Are the spokes tensioned up or fairly easy to wiggle around? Tires properly inflated (I had to ask)?

I've never ridden a Sirrus and have no clue how they are tuned for ride, but I'm guessing that even for an aluminum frame it's tweaked more to the comfort end of the spectrum. That translates into a frame that may be a bit flexible.

You don't state much about your riding style or the terrain you cover, but a 17 MPH is definitely in the realm of drop bar bike speeds. With a decent amount of and/or weight and with a competitive or even a spirited riding style a rider tuned in to his bike will notice any 'give' or flex in the system.

It is, as you said, probably nothing to concern yourself with and is probably using very little energy. At the same time it may be that are a rider that would enjoy a stiffer drop bar racing style bike.

 

I would not think you would notice the frame "flex" on a sirrus.

What you probably felt was the wheel. The stock wheels on those bikes... or just about any bike for that matter, have the lateral stiffness of a wet noodle. Pushing 30 in a turn... yeah, I'd wager that would be enough to feel the wheel give a bit.

Kudos to pushing that kind of average speed on a hybrid! I see a full on carbon road bike in your future.

 

I ride on paved roads. My riding style is generally go as hard as I can as I tend to ride for exercise and not for leisure - it's just the way I am. My rides average anywhere from 15-30 miles, and I float around that 17mph speed. I'll do standing hill climbs on more steeper grades or drop the gearing down on slighter grades. For the most part I keep the front derailleur on the 3 (max), and use 6-8 (8 being max) on the rear to keep myself at the best speed I can go.

I'm 5'10.5" and weigh around 160.

I had the bike shop set me up. Didn't pay for the fitting because I figured I would only do that on a really expensive bike. I never thought of wheels being the issue, but it did feel strange for that moment in time, and my mind definitely felt something.

 

Perhaps the air pressure in your tires is a bit low. On a high speed turn, an underinflated tire will roll to the laterally.

 

Tires say 75-100. I generally put in 85 to allow for heat.

 

160 pounds...I would try going up to 90-95 PSI, increasing the pressure gradually to see how the tires handle it. Maybe even going to a better tire that will be safe at higher pressure. You may or may not like what it does to the ride quality, but it will take most of the squirm out and may add a little more speed and acceleration to your workouts. I don't know where you are riding, but I would only worry about tire pressure increasing due to heat unless you are riding in a desert/very hot climate with roads that drip tar.

You might also have the local shop go over the wheels and take the spoke tension up a bit. The more flexible wheels I've ridden tend to irritate me under hard climbing and cornering.