What I Learned About Traffic Light Sensors

Last week after the City of Houston Town Hall meeting in Kingwood I talked with the representative from Public Works, Joann Clark, about traffic light sensors not tripping the traffic lights when I was on my bike. I gave her three intersections that I frequent and my phone number. She said she would have a traffic engineer call me and we would meet at one of the intersections to see what I was talking about.

Today I got the phone call and agreed to meet the engineer at Woodridge Forest and Northpark Drive with my carbon fiber Stadalli Red Pro 14 to test the traffic light sensors. To reproduce a bie ride experience I put on my cycling apparel and met two traffic engineers. Pictures of the lane where we tested my bike and sensors.

After showing the engineers my bike and all of the carbon fiber they opened the control cabinet to see what the lane sensor was set at. To test the sensor they put an aluminum road sign at the corner of the sensor layout on the street. Next they walked my bike into the sensor area to see if the sensor saw it. It did not. We talked about the amount of metal on my bike which isn’t very much and no magnets at because I use non-magnetic sensors for my Elemnt computer. They adjusted the sensor settings and walked the bike into the area again. Still no pickup by the traffic light sensor. We did this several times with the same result. The engineers were perplexed because they had never tried the sensors with a carbon bike. They tested the sensors with metal bikes and an aluminum bike with a magnet. We moved to another sensor area at the same intersection and still no pickup of my bike. The third sensor area closest to the curb near the east bound Northpark Drive lanes did register the Stradalli this time.

They took the settings from the successful pickup and reset the first sensor. The sensor recognized my bike in the area but not strong enough to trip the sensor to change the light. The sensor could not be adjusted any stronger though to make it trip the light. The engineers were very appreciative to learn about this sensor issue. They are going to advise the City of Houston bike coordinator of what they learned. They are also going to contact the Harris County traffic engineer and TxDOT traffic to see if they have a solution or know about this problem.

What I learned:

  • A magnet could help trip the sensor. I am going to add a magnet from a Garmin cadence/speed sensor to the front wheel and try this at the same spot
  • The “sweet” spot to trip the sensor is at the corner inside the box.
  • Instead of riding on top of the groove where the wires have been buried, ride 6″ inside of the line to the corner.
  • In the City of Houston the cameras mounted above the traffic lights are being phased out because they are not reliable.
  • Some of the grids in the road use pressure (weight) to trip the sensors but those are being replaced because they are not reliable either.
  • If the sensor does not work use the pedestrian button.

I will let them if the magnet works.

29 Inches: Does Your Bicycle Wheel Size Matter?

29 Inches: Does Your Bicycle Wheel Size Matter?

Everyone raves about 29 inch tires and how great they are. But why is that and is your bicycle wheel size really that important?

Here in Texas, it’s pretty conclusive based on bike sales. 29 inches of tire is highly preferred over the old school 26 inch tires.

I took some time to ask the resident experts at Cadence Cyclery this weekend and got the opinion of semi-pro racer and coach Grayson Kepplar who you can find over at the Mudbandit blog.

With any luck, Grayson may become a regular around here.

29 inches = Less rolling resistance

The big difference between a 29 inch tire and a 26 inch tire is how much easier you roll over things.

My wife, who is a new convert to mountain biking, describes riding a 29er as “They’re awesome and you can just roll over stuff.” Well said, and true! Take a look at the below image to see why.

29 inches: 29er angle of attack

The image above shows how the angle of attack for a 29er is much less steep, making it easier to get over the top of and carry your speed through. While that picture does slightly exaggerate the concept, the principle is very well shown.

Gary Fisher, a legend in mountain biking, was the first manufacturer to heavily publicize and push the 29er movement. He describes the benefits of a 29er in this video below.


Think about it, you have 3 additional inches of tire that can give you a huge advantage when rolling over obstacles in the trail. Your bicycle’s wheel size now lets you maintain more momentum and keep moving without losing as much speed.

Is a 29er always better?

As Grayson pointed out, there are times that a bike with a 26 inch wheel would be preferred.

Tight, twisty and winding trails can be better for a 26 inch wheel. 29 inch tires are easier to get up to higher speeds, but can be slower with acceleration. On a twisting trail you will be slowing down more frequently as you round corners and being able to quickly accelerate to get back up to speed is critical. Especially during a race when every precious second counts.

Is a 29er a good beginner bike?

What about for the brand new rider, someone looking for their first or second bike. Is a 29er a good bike to start on?

Yes. It is absolutely a good bike to start on and I highly recommend it as the best kind of bike to start on. Bikes with 29 inch tires have several key benefits that are ideal for a new rider.

Smoother Ride

Because of the large tires these bikes are able to carry their momentum far better than their 26 inch counterparts. For a new rider who may not have the core stability to balance themselves well this helps to even out the way the trail feels underneath them. The large tires also have a higher air volume, meaning there is more room for compression inside of the tire itself. This helps to absorb shock from the trail while riding and when combined with a carbon fiber frame, it can equal the amount of shock absorption you get from a 26 inch bike with a small rear suspension.

Increased Contact Area and Traction

The larger tires of the 29er gives your bike more surface area that is in direct contact with the ground. According to Jim Papadopoulos, the contact patches on a 29 inch tire are 5% longer although narrower. This leads to you having better linear traction on the trails, something that is especially beneficial when riding on loose gravel or sand. There are a lot of the same benefits that switching to a tubeless tire setup does.

More Stability

There are 2 reasons that a 29er is more stable than a 26 inch bike of the same quality and make.

A 29er will be a little bit heavier than it’s smaller counterpart. The frame is larger, the wheels and tires are larger, even the cables have to be slightly longer. This increased weight in the materials means that your bike feels slightly heavier and more solid than the 26 inch bike.

A 29er isn’t affected as much by rocks, roots and obstacles which makes you, the rider, feel more comfortable in the saddle. See the reason above on why the ride is smoother.

The never ending debate

This topic gets debated more than anything else I have ever seen, and there is no definite answer. Every rider will have their preference whether they prefer a 26 or 29 inch tire. Just like every rider will have a preference of either a hardtail or a full suspension bike. My suggestion is that if you are looking at buying a new bike, check out the 29ers thoroughly and be sure to ride on some bumpy terrain or at least over some curbs to get a feel for the different size.

I hope this has helped give you some more information on why you might want to consider a bike with 29 inch tires. Leave your thoughts in the comments below.

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