Why parking lot test rides tell you very little about How a full suspension mountain bike rides

I've been reminded over the last two days at Outdoor Demo at Interbike 2016 as to why just doing a parking lot test ride really tells you very little about how a full suspension bike actually rides on the trail. I'll give you two examples:

Example 1

In terms of climbing performance some high single pivot bikes actually feel quite good in parking lot rides since the slight lock out effect of the high pivot provides an efficient firm pedal feel. But when you actually get this type of bike on a trail, the slight lock out effect now becomes translated into pedal feedback and the bike hanging up on ledgy climbs, rocks and roots. Also over the course of a longer ride on dirt, the relative inefficiency of this type of suspension becomes more obvious.

Example 2

The other way to control suspension movement in active suspension designs that don't control bobbing and sag through the mechanical design of the suspension is to use shock damping. Generally this consists of compression damping to limit unwanted motion and perhaps also fast rebound damping to limit suspension sag when climbing. One bike that I rode in the last two days used this type of setup and felt surprisingly fast climbing on the road to the trailhead given how I knew its specific active suspension design typically reacts. Once I got on dirt, my perceptions changed 180 degrees and I could not WAIT to get off this bike. What happened?

Once this bike hit real-life rocks and other trail obstacles, the heavy compression damping caused the rear suspension to skip over rocks instead of absorbing them while what I thought might have been fast rebound damping was continually pogoing the bike down the trail. The bike was both difficult to control and tiring to ride even for the short amount of time that I was on the bike. From a parking lot test ride alone, you could have easily gotten the impression that this might be a great bike.

At Dirt Merchant Bikes, we stress the importance of actually getting on a bike to test out both fit and ride feel. Currently, we have Medium to X-Large Turner RFX demo bikes in stock and are looking into getting Turner Flux demo bikes as well. We do ride both the Turner bikes as well as competitor bikes to help us recommend the right bike for you, but we still think that getting you personally on a bike is invaluable. If you have any questions about this blog post or how we do demos, you can reach us at jeff@dirtmerchantbikes.com

Measuring Tire Cornering Predictability with Data

In our Summer 2015 XC tire comparison test (to be published tomorrow), we started to record lap times for each tire tested. Though there was a small sample of lap times for each tires (5 test riders riding each of the test tire combos once), I decided to also take the standard deviation of the recorded times to see if I could see any patterns in whether the lap times for each tire were more clustered around an average or were, conversely, more spread out. 

[Definition of Standard Deviation:  The standard deviation is a measure of how spread out the numbers in a data set are. A smaller standard deviation means the data is more closely clustered around the average of the data set, while a larger standard deviation means the data is more spread out.]

What I found was that there indeed was a difference between tires in how spread out their lap times were. Based on a synthesis of the subjective feedback and quantitative performance ratings with the standard deviation of the lap times, my interpretation of the standard deviation of the lap times recorded for each tire is that it is a measure of how forgiving a tire is of less-than-perfect riding.  In this context, tires that are more forgiving will have a lower standard deviation score. I’m defining forgiving as the ability to:

·         Communicate the amount of available traction

·         Quickly regain climbing traction after traction is lost

·         Recover easily and quickly from the front tire sliding

·         Slide the rear tire predictably

The opposite of a forgiving tire will be one that tends to break away quickly and without warning. Forgiving tires will tend to have moderate to high traction limits and tend to lose traction predictably thus allowing riders to more confidently explore their traction limits.

The reason why I think the standard deviation is a measure of how forgiving  or, put in another way, how accessible a tire’s performance limits are is because I believe a more forgiving tire should result in less variance in lap times due to more gradual breakaway characteristics that can be caught and corrected more easily.  Tires that break away more unpredictably might be expected to have a larger time difference between a “good” run and a “bad” run.


Your thoughts?

The cheapest fix to improve your bike's cornering ability and climbing efficiency

After running 9 tires through our recent comparison tests, I have been quite surprised to see how much tires can improve cornering ability and climbing efficiency.

Climbing Efficiency: The best rolling tires made a bike feel several pounds lighter.  Some tires literally would stop rolling without pedaling, while the best rolling tires seemed to continue rolling on their own as if they had an electric motor attached.

Cornering Ability: Finding tires with cornering grip was not a difficult task.  Combining that cornering grip with good steering feel to be able to make the most of that grip was less common.  The best front and rear tires that we found for cornering combined both good levels of cornering traction as well as constant communication of trail conditions and available grip.  Different tires could make the same bike change from handling like a monster truck to feeling like a sports car.

Good tires aren't cheap, but if you've spent good money on your bike, cutting corners on poor tires is penny-wise, pound foolish.  Tires can make more of a difference on how your bike handles than almost any other upgrade you can do to your bike.

Tire Cornering Grip: Absolute Traction vs Usable Traction

Dirt Merchant Bikes has recently started our series of tire comparison tests for our Pacific Northwest winter conditions.  One insight that I had from the tests is that Usable Traction (which I will define shortly) is more important than the amount of Absolute Traction that a tire has. I am defining Usable Traction as the amount of traction that is accessible to riders of average skill levels based on how well riders are able to anticipate a tire's traction limits.  One of the tires in the first test has a strong reputation for being a good cornering tire.  However, another tire with perhaps slight lower absolute cornering traction was unaminously preferred by testers for cornering ability.  The key factor driving this perception was how well this tire communicated the limits of its cornering traction and the amount of available traction.  For most riders, I think that how precisely a tire communicates when it is going to break away may be more important than its absolute traction limits.  Your thoughts?

Check out the results of our first tire comparison test at:  http://www.dirtmerchantbikes.com/special-events/2014/11/20/tire-comparison-test-report-2015-nobby-nic-high-roller-ii-neo-moto-hans-dampf

Our upcoming tire comparison test will include the following tire combinations:

1. Hans Dampf 2.25 (front)/Nobby Nic 2.25 (rear) – This combination balances the traction of the Hans Dampf as a front tire with a faster rolling Nobby Nic as the rear tire.
2. Magic Mary 2.35 (front)/Hans Dampf 2.25(rear) – The Magic Mary is the highest traction tire in the Schwalbe lineup short of a full-on downhill tire.
3. WTB Vigilante 2.3 (front)/ WTB Trail Boss 2.3 (rear)
4. Continental Trail King 2.2 Protection Apex - front & rear – The Trail King is similar in concept to the Hans Dampf.
5. Continental Mountain King II 2.2 Protection - front & rear:  The Mountain King is similar in concept to the Nobby Nic.

Like our Facebook page to get notification when our second tire comparison test is published in several weeks:  https://www.facebook.com/dirtmerchantbikes

Seeking Product Testers for Dirt Merchant Bikes

What're the best tires for PNW trails? Help us  find out!

Dirt Merchant Bikes is seeking Product Testers for our upcoming PNW Winter Tire Test!

Dirt Merchant Bikes is looking to develop standard recommendations for tire combinations for winter riding in the Seattle area. Tire testers will ride our fleet of Turner demo bikes. The tires that we are planning to include in our first comparison test are:

Schwalbe Hans Dampf
Schwalbe Nobby Nic
Panaracer Neo-Moto
Vredestein Bobcat
Maxxis High Roller II

If you are interested in participating in this tire comparison test or future product tests, please sign up for Dirt Merchant's e-mail list at:


Carbon or Aluminum for Full Suspension Bikes

The marketers have already won over many of us that carbon fiber must be the better material for bike frames.  But...how many of you have actually tested this assumption.  The benefits of carbon fiber are undeniable in theory.  Carbon fiber offers the same strength as an aluminum bike at less weight.  Carbon fiber offers, at least in theory, more tunable ride characteristics.

I did a subjective test at the Interbike Dirt Demo of how carbon fiber suspension bike frames feel versus aluminum frames.  I rode several bikes that were similar in intent and suspension travel.  The first test subject was the Specialized Stumpjumper EVO in carbon which honestly did not feel great at either climbing or descending.  I also had a chance to ride both the Devinci Troy in both carbon and aluminum back-to-back.  As I expected, the aluminum Troy felt more sluggish than the carbon Troy.  Case closed, right?  Not so fast.  The last bike of the day was the Transition Patrol in aluminum.  Carbon fiber or no carbon fiber, the aluminum Transition Patrol was one of the best riding and best feeling bikes that I rode at Dirt Demo.

Two lessons learned from this year's Dirt Demo:

1. You can't generalize as to how carbon or aluminum will feel.  Geometry and ride tuning are factors that will likely be more important than frame material in affecting how a bike rides.

2. I need to spend two days at Dirt Demo to answer any questions that come up for me on the first day & answer any questions/requests from all of you! 

Thoughts on carbon vs aluminum?

Tips on Shimano Disc Brake Bleeding from the Shimano Tech Pro in charge of Brakes

[From the Shimano Tech Seminar on bleeding brakes]

Syringe Bleed - 

Attach bleed syringe to the bleed valve on the disc brake calipers.

Attach the bleed funnel to the bleed port on the brake lever.

Pull brake lever & open and close bleed valve - shoots air in the valve into the bleed syringe.  

Push in about of a 1/3 of a syringe of brake fluid at a time.  Cycle the brake lever slowly to get bubbles out.  Cycling the brake lever too fast tends to break up air bubbles into many smaller bubbles which are more difficult to get out.

Don't try to back pressure air out of the brake valve by pulling air out with the bleed syringe.  This may actually introduce air into the system.

Don't overfill the system:  

  • Caliper piston seals are permanently flexed and can let dirt in more easily, fluid will come out of the weeping port at the lever.
  • Orient bleed valve at the top to facilitate getting air out.  Move caliper and brake levers around while cycling brake lever to help get air out.