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Monday
Nov112013

Trek World Racing Expands Downhill Roster, Now Racing Junior World Cup

Trek World Racing is excited to announce that for 2014 it will be expanding to 5 Downhill riders being led by World Cup race winner Brook MacDonald (NZL) and his compatriot George Brannigan. Also returning are riders who both hit the top 10 in World Racing for the first time this past season, Neko Mulally (USA) back for his 5th season with the team, and Greg Williamson (SCO) whose promising season was unfortunately cut short by injury at the World Championships. Joining these 4 talented elite men come January will be emerging phenom Laurie Greenland from Bristol in the UK, who’ll be contesting the Junior World Cup in both 2014 and 2015. All riders will be aboard the Trek Session 9.9.

Brook MacDonald says: “I’m stoked to be heading into 2014 on TWR with a new shoulder and new beginnings. I am already itching for the 2014 season to start and getting things underway with such great support and people behind me. Everything is pointing towards a strong season and I can’t wait.”

Neko says: “I’m really excited to be returning for my 5th season with Trek World Racing. I've got good people around me; it feels like family to me! Next year I want to be a consistent top 10 rider and push towards the podium. Can't wait to get out there and make it happen!”

George says: “Next year I’m determined to get back to where I left off before knee surgery in 2012. I finished 2013 strong and finally I know where I need to be. With a good off-season not having to focus on recovery I know I’ll be well prepared for 2014, so I’m already impatient for the season to start.”

Greg says: “After an up-and-down season, I'm really looking forward to getting back to racing in 2014 with a different approach. I'm seeking a very successful second year with Trek World Racing. To have another British rider on the team is exciting. Laurie reminds me of my younger self so it’ll be cool to have that youth as a reminder of what it's all about, and to be able to help him reach his goals."

Laurie says: “I’m extremely excited about signing with Trek World Racing. To be on a big team like this has been a dream of mine since I was 8, so for it to actually happen is unbelievable! All the riders on the team are big names and to be given the opportunity to ride and be on the same team as them is pretty mad. The team will strongly support me to achieve my goals which include making a mark on the World Cup circuit, aiming for podiums and a medal at World Champs, as well as always being sure to have fun!”

Team Owner Martin Whiteley says: “It’s great to be able to announce our roster so early and to have all the preparations for 2014 well advanced. Being able to keep this elite group of 4 men together was really important as I believe both on and off the bike, they are one of the best groups of riders I’ve ever assembled for any team. Of course I’m delighted that we’re entering the Junior World Cup next year. The series was a great success in 2013 and to have Laurie representing us is huge, we’re excited about having the opportunity to help develop him into a fine World Cup racer.”

The team will also receive the guidance and assistance from experienced World Cup racer Justin Leov who takes up the role of Skills Coach and will be on hand working with the riders at various key events around the world.

The team is proud to confirm the following co-sponsors: Shimano (Brakes and Drive Train), Fox Racing Shox (Suspension), Bontrager (Tires and Wheels), Royal Racing (Competition and Casual Clothing), Seven IDP (Body Protection), FUNN (Handlebars/Stems), MRP (Chain Guides), DT Swiss (Hubs), SDG Components (Seats and Seat Posts), SRM (Power Measurement), Motorex (Lubricants and Cleaning Products), ODI (Grips), Cane Creek (Headsets) and Alpinestars (Team Baggage).

The team website www.trekworldracing.com will be updated in January with profiles of all 5 riders.

Thursday
Nov072013

ArtsCyclery Now U.S. Importer of MarshGuard Products

ArtsCyclery.com is proud to announce its new partnership with MarshGuard to serve as the U.S. importer of MarshGuard products. Followers of UCI World Cup Downhill racing or the Enduro World Series are already very familiar with MarshGuard’s outstanding fork mounted mudguards. Designed by Greg Minnaar’s World Cup DH race mechanic, Jason Marsh, this simple and effective fender is lightweight at 32 grams and inexpensive at $14 USD. Any mountain bike that sees action in wet conditions deserves a MashGuard, available for purchase now at ArtsCyclery.com/MarshGuard.

•       Actual weight 32 grams (without zip ties)

•       Zip ties included with fender

•       Designed by World Cup DH mechanic Jason Marsh

•       The choice of World Cup racers

•       $14 USD

MARSH GUARD

Saturday
Nov022013

Wheel Size Facts Part 2.... Rollover Factors

Part 2 from the boys at Banshee Bikes.....

Here is some more independant wheel info to help you decide which wheel size is for you. I will be taking the same dimensions as discussed in Part 1 to perform these calculations. These theoretical calculations do NOT take into account tire deformation... which I will talk a bit about later. This week, get ready to deal with everyone's school subject fav - some trigonometry! So belt up, and let's rollover some wheel-based maths (oh dear....!)

'Rollover':

You'll almost definitely have heard 29er riders saying just how much better their bikes roll over obstacles on the trail. "I carried so much more speed through that rough section!", or something similar. This is probably the key reason that riders and manfacturers give for having a bigger wheel size... But what does this mean, and just how much better do they perform this action?

The diagram below (Fig. 1) shows the height of a square-edge obstacle, and the angle of attack vis-à-vis the wheel:

Fig. 1 When a wheel makes contact with a square-edge obstacle (for example, the curb of a pavement - that's British speak for 'sidewalk'), the angle of attack = the angle of the tangent of the wheel at point of contact with the square edge obsticle and the horizontal as shown above.

Fig. 2 how each wheel size's angle of attack varies with obstacle height across a range of square-edge obstacle heights. Of course these values are all perfect and theoretical (not taking into account tire deformation, tire pressure or bike lean angles etc.)

The angle of attack itself doesn't really tell you much without applying basic trigonometrical functions to to break it down into horizontal and vertical force vectors. In a simplified form without friction or deformation, if a wheel runs into a vertical obstacle higher than the axle height, it will stop you instantly (horizontal force / vertical force = infinity). Conversely, if an obstacle has zero height it will not slow you down at all (horizontal force / vertical force = 0). On Fig. 3, you can see how the force vector varies as obstacle height increases for each wheel size (the higher the Tan (Angle of Attack), the more it will slow you down):

Fig. 4 shows how the force vectors vary as a % relative to the 650b wheel. A positive number represents a higher horizontal resistance (effectively, this means it slows you down more). So, you can see that 26" wheels will slow down more than 650b wheels which in turn will slow down more than 29".

This graph clearly shows that the relative efficiency is not consistent across all obstacle heights. The larger the obstacle, the larger the effect the wheel size will have. So it is impossible to say that one wheel is x% more efficient over square-edged hits than any other size without saying the size of obstacle, tire size, and tire pressure etc etc.

It should also be said that not only are big wheels more efficient at rolling over square-edge hits, but they also result in a smoother ride. This is because, for any given speed, the larger the diameter of the wheel the longer it is in contact with the obstacle (i.e. it hits it sooner and leaves it later). Therefore it has longer to react to the obstacle. Plus, the bigger the wheel the less of it is going to drop into holes (think braking bumps), hence 29ers feel like they smooth the trail out.

Once again I want to make it very clear that these numbers are based on wheels that do not deform at all, and that are rolling over perfectly square-edged obstacles, which is obviously not realistic. So let's have a quick look at some real world factors that significantly complicate the situation.

Tire deformation helps to absorb the impact of hitting a square-edge obsticle. This not only reduces the shock that is transferred to the frame and rider, but also makes the wheel roll more efficiently over an obstacle by effectively reducing the angle of attack when it absorbs it. The more the tire absorbs the obstacle the better, so actually lower pressure tires roll over obstacles like this more efficiently (unless you get a snake bite!).

Tire size is an important factor... for example you could realistically have a larger outside diameter running a very high volume tire on 26" wheels than a small volume tire on a 650b wheel. In this situation the 26" wheel would roll over things better than 650b, so tire height should be considered if analysing options.

We have indeed confirmed that big wheels roll over obstacles better than small wheels, and help maintain momentum as a result. But frame geometry and axle path also play a factor if the frame has suspension, as the suspension can help absorption of obstacles and make the bike roll over them better. The slacker the head angle or more rearward the axle path, the better a bike will roll over an obstacle if all other factors are equal.

Plus there is one very very significant factor that none of these numbers take into account...We can bunny hop over things! This is why you should never listen to arguments taken from automotive industry as the car can't be thrown around independently of the driver.


If this second installment of wheel physics hasn't boggled you even more than the first part, the third blog post will tackle contact area and grip. Woop!

Saturday
Nov022013

Wheel size facts Part 3... Contact Patch and Tire Factors

Banshee sent along part 3 of their tire/wheel series today check it out below....

In this post, I'm continuing with the wheel size theme, but looking at tire related factors such as contact patch, tire pressure and tread. Check out Part 1 and Part 2 of this mini series for some other wheel/tire things to consider. In Part 1, small wheels beat big wheels, but in Part 2 big wheels fought back... so which, if either, is going to come out top for you?

Here, I  discuss contact patch and related factors across the 3 common wheel sizes. Once again I will be taking the wheels and tires from Part 1 for consistency.

Contact patch:

What is the contact patch, and how does it effect grip and rolling resistance?

The contact patch (shown in fig.1 in blue) is essentially the footprint of the tire that is making contact with the ground at any instant in time. For any given tire, it will change with tire pressure, as Pressure=Force/Area. So the lower the pressure, the more your tire will deform to the contours you are riding over.

A larger tire contact patch area represents more rubber on the ground, which increases friction and therefore grip (good). However, the larger the contact patch area the greater the rolling resistance (bad). So, as with most things, there is always a compromise, and you just have to pick the right balance between grip and rolling resistance to suit your needs.

Shape and area:

For this section on contact patch shape, let's look at a basic representation of each wheel size (no tread, and no tire stiffness) each with 2.3" width , based on 50kg of weight (assuming 50:50 weight distribution, and bikes + rider = 100kg), and 2Bar (about 29PSI or 200,000 N/m²) of a perfect gas on a flat surface for all wheel sizes. Since the pressure is the same in each tire, the contact patch area will be the same for this scenario as Pressure=Force/Area. This is not very realistic as pressures will change a bit with wheel size (I will go into that later), so this is just to give an idea of patch shape.

 

In Fig .2 you can see the 3 wheel size contact patches overlapped for the same tire pressure and loads: the bigger the wheel size, the longer and narrower the contact patch. But the variation in shape is probably much smaller than you'd expect, or have been made to believe. So let's look at this slightly differently...

One way of measuring optimal tire pressure is actually as 'tire drop', which is a percentage of original tire height (a little like suspension sag) as seen in Fig.3.

pressure, as well as contact patch shape and area for each wheel size.

As you can see in Fig.4, the contact patch area and lengths change as tire pressure changes, but the width remains the same due to same tire carcass width and cross sectional shape. So for the same tire drop of 6% the 29" wheel has a 2.7% bigger contact patch than 650b, which in turn is 1.85% larger than 26". The difference in contact patch area and shape is far less than most marketing would have you believe, but it is present.

This also shows that the larger the diameter wheel, the less tire pressure is required to achieve the same tire drop. Therefore you can get away with running lower tire pressure on bigger wheels if you wish. That said, the volume of the tire is the more significant factor, so the width of the tire will have a more significant impact on required tire pressure than wheel size.

These factors are the reason that mountain bike tires are wider than road bike tires. For road cycling, traction is less important than minimising rolling resistance (and weight) and so they run narrow low volume tires at high pressure. Mountain bikes run lower pressure, larger volume tires to increase traction as well as shock absorption. It's a case of picking the best tool for the job, by optimising what you want, and compromising on factors that are not as important to you.

Tire tread and compound:

 

All this marketing chat about contact patch actually ignores the most important factor. Tread patterns are massively relevant, because in reality, none of us ride around on fully slick tires. So when talking about contact patch, we really should be considering actual contact patch of the top of the treads on the surface, and also considering the extra grip provided by the edge of the treads biting into soft ground. Tread pattern and rubber compounds make a bigger difference than contact patch area.

The tread pattern changes the contact area far more than wheel size will!

So when thinking about grip, rather than think too much about wheel size and exact tire pressures, you'd be better off spending that time and effort picking the best tire tread pattern and compound for the riding conditions and experimenting with different tire pressures.

A softer rubber compound (lower durometer) will not only deform more to 'grip' the ground, but will also help damp the ride by compressing more easily under impacts. If you use a new soft compound tire you will be able to brake later, accelerate faster, and corner harder because the tread will bite into the ground with nice sharp edges, and the soft compound will have a higher coefficient of friction, and absorb the shock to stay in contact with the ground better.

For you to consider:

From all the information above, you can see that a bigger wheel will offer a slightly larger contact patch area due to the fact that you can run a slightly lower tire pressure. Therefore, a larger wheel will offer a bit more grip than a smaller wheel with same tire drop, but the increase in theoretical traction of larger wheels is probably less you were expecting.

With the larger tire contact patch comes more rolling friction, and efficiency is reduced. So smaller wheels are more efficient than larger wheels in this area for same tire drop. On a perfectly flat surface with a slick tire, smaller wheels with equal tire drop will lose less energy when rolling along than bigger wheels.

But let's be real... mountain biking isn't about just rolling along flat surfaces and we certainly don't use slick tires! It's about carrying speed through rough sections, cornering hard on the edges of tires, finding traction when climbing steeps and many, many more fun things. For most of these things, tire tread pattern and tire rubber compound are FAR more important than wheel size when it comes to grip. So my advice to you is not to get too lost in these wheel size numbers, instead pick a good tire choice and just enjoy riding your bike!

 

Tuesday
Oct292013

USGP of Mountain Biking Postponed Indefinitely 

Dear Mountain Bike Friends,
 
After much reflection, I have decided to postpone the US Grand Prix of Mountain Biking until further notice.  I wanted to thank everyone for their continued support through my time with the Pro GRT and into the USGP of Mountain Biking.  Unfortunately, my plans to help rebuild the US race scene by combining downhill, enduro & other disciplines have yet to bear fruit.   Although I do believe that program I developed can be & will be successful, it will have to wait until a further time.

Don’t worry…  I’ll still be around.  You can’t get rid of me that easily!   I will continue to grow my race team - the “ARMA Energy MTB” professional mountain bike team – into one of the premier race teams from the U.S.  In addition to national caliber downhill racing, we will be expanding into Enduro and World Cup racing for the 2014 season.  I will also be focused on my bike shop(s) – the “BIKE VAULT” & “T.RYX Recumbent Trikes” based in Escondido, CA.
 
I urge you to continue to support U.S. racing, as we will be.  Until a true national caliber series can be developed & be sustainable, there are plenty of regional and local events to support.

Thank you all once again for your support.  I will see you at the races!

Best regards,

Jeremiah