Bike Stiffness. How To Tell?
 

There is much talk about Bike Stiffness. When I am trying a bike, or riding a bike, how can I tell how stiff it is?

you're likely not strong enough for it to matter.

It is a lot like "The Emperor's New Clothes". Those that are worthy of a stiff bike can tell. If you can't tell, you are not worthy. The trick is to never admit it.

You can't. It is subjective, and has no unit of measure.

By the way, the more items that you compare before making a purchase, the more likely you are to be dissatisfied with your eventual choice.

This could explain why my marriages keep getting shorter.

Stiffness is completely irrelevant for most, so ignore the talk and ride the bike you're most comfortable on.
A friend of mine once remarked the thing he liked most about his bike was also the thing he hated the most, something like stiffness is great for races requiring quick accelerations, but it's not so good on those 3+ hour rides.

Find a really big hill and stand up and mash all the way up

Stand on one side of the bike, one hand on the bar and one on the saddle. Lean it away from you a bit and with the pedal in the down position press on it and note how far the BB shell moves off the CL. Maybe run string from axle to axle first as a gauge.

(Bikeshop bros are gonna love me for this.) :)

The responses seem to assume a bike can't be too stiff. Not so. For example, touring bikes often feel dead when not loaded, disproportionate with the weight. Some racing style bikes also feel dead and unresponsive after an hour or so, in spite of light weight.

Super stiff often feels alluring and responsive in the parking lot, but it can really suck out on the open road. Your legs turn to lead and you struggle to stay on top of your gear where another bike may still feel eager to go even when you are dead tired.

On metal bikes (carbon bikes are too small for me), I look for some springiness when twisting between the bars and seat tube, but if it has an exaggerated shivering that stems from my nervous unfamiliarity, it is probably too flexy. I also look for a small amount of frame springiness when pressing on one pedal with the brakes locked (about as hard as I would under hard seated riding), but not to where it feels sloppy. The movement should feel linear in relation to force. If it feels dead stiff in every direction, it won't work for me.

Unfortunately, those tests are subjective and require personal experience.

How do you know of he isn't strong enough? This could be Sagan for all you know

I was waiting for some newb to write something like this. You should have waited for some fool to expose himself.

"Stiffness" in a bike is difficult to quantify, and its benefit, or lack thereof, varies depending on the rider and where you ride. Heavy riders benefit most from a very stiff bike. Light riders suffer on stiff bikes, particularly on rough surfaces. At 145#, I find stiff bikes difficult to control on rough pavement.

So, don't take "stiffness" as the single arbiter of a good bike. Ride what works best for you, and let the marketing department worry about "stiffness."

Or your avatar, it could be your avatar.

Measure the deflection from an applied force

By stiffness do you refer to BB flex? I have noticed that even in my two cheap bikes that the steel bike has a bit more flex when as @rms13 mentions you climb a hill out of the saddle. Particularly so if in a gear which gives you 75+ inches.

Doesn't Park Tools have a stiffometer? Maybe go down to the local co-op and ask to borrow theirs.

To how many watts does one have to dial it up to for it to matter?

Sixteen posts on a thread about frame stiffness and nobody has even mentioned Jan Heine? What has this forum come to!

Ride em. In the case of my now relatively old SL2 Roubaix frame, I did not appreciate how not "stiff" is until I rode my LeMond. As mentioned above, a hill will help you tell the difference.

I wash my bikes in a special Viagra/detergent mix for extra stiffness.

If you pedal hard while standing and your arms want to come off it means you've got a stiffy

I love this thread already :)

One interesting thing I have discovered with very flexy carbon fork I had on my old bike was when using a magnet style speedo sensor the speed would drop when I did out of the saddle sprints due to the bowing of the frame.

I am curious if using a speed and cadence sensor can be used to determine flex by placing it in different locations on seat and chain stays.

Pedal like you are running away from a black hole supernova and then you will tell.

At the risk of making this a useful thread, yes, do this. And listen / feel for brake rub, with the brakes adjusted to the same clearance.

Whether you want a stiffer bike is another question.