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You need to use an tubeless bead tyre on Mavic UST rims. These are standard on all UST tubeless tyres, as well as what they call tubeless ready tyres, e.g. Bontrager Revolt Super X TR. These are in essence the same as the folding version (light casing), but with a UST tubeless bead. Normal folding will not seal as well on a UST rim. This quote from a blog: "... but UST has a lot more to do with the standards of rim hook/tire bead interfaces than it does with whether or not you would need sealant to make the tire hold air. Basically it is a standard that indicates the tire with UST approval and a rim with UST approval are safe to use sans tube."

Crossmarks for hardpack, rocky and loose - typical Southern and Eastern Cape conditions. Schwalbe Nobby Nic's for wet roots, soft, forest, etc. - typical KZN, Sani2C stuff. Schwalbe is expensive when bought in RSA - you can buy them from German websites for half the price, shipping included.

The following from the Fat Tracks MTB Club website: Because of the problems CSA have been having, all licenses are valid until the 17th February 2008. So if you don't have your license yet, don't stress, you will be able to use last year's license for the Herald!

What are your views on Hutchinson Bulldog's?

Zuurberg pass near Addo in E-Cape. Not the steepest gradient, but nearly 40km of uphill.

Anybody interested to join me on some training rides in J-Bay from 21 December? PM me, and we can discuss. Otherwise, if somebody just needs training route info, I cycle in the area a lot and know most trainig routes.

Any ideas on safe removal of star nut from suspension fork.

Have a look at http://www.analyticcycling.com/WheelsClimb_Page.html. I played around with the model, and it seems that this model supports Johan Bormann's view. I kept everything the same, but made in the one instance, the bike heavier and the wheels lighter, and the other the wheels heavier and the bike lighter. On a 13 km climb, with a 10% gradient, both riders get to the top at the same time. I think the biggest impact that weight on wheels will have is to overcome inertia, but once at speed, a heavier wheel may have more momentum. Look at time trial bikes - their wheels are heavier, but more aerodynamic. One can take this argument very far, as the question can then be asked what about 29er's vs 26er's in MTB. As the rim and tyre weight on a 29er is further from the center, will it mean a bigger weight effect - probably not, as then we would have seen smaller and smaller wheels. In the end, for practical real world sitaution, I tend to lean towards the weight is weight view.

Its a pity the topic degenerated into this. I introduced it in order to generate some views on science compared to real life. As in all of science, you get the formulas, but then you get real life. With regard to this issue, there are so many variables, and any combination of any of them can result in a different outcome. It is therefore quite simplistic to try and isolate one. I also think that the bike industry has a lot of "urban" legends, which unfortunately very few LBS employees try to understand. One of these is the "loosing weight on the wheels" issue. The answer is probably a bit more complex. Weight at the center of a wheel has exactly the same effect as weight on the bike or person. Weight on the outside of the wheel (tyre, rim, etc.) does have a rotational effect. Remember the experiment holding two weights to your chest on a turning chair. The moment you extend your arms, you go slower, when you bring them in, you go faster again. I am, however, not sure how big effect it really has on performance. My view is that weight lost on a wheel provides such a small benefit over weight lost in other places, that one can ignore it. Furthermore, as I originally indicated, there are so many variables, that in practice, we can not get to accurate calculated numbers. We can, however, say that weight has the biggest effect on an uphill, and little or no effect on flats and downhills. If I look at it practically, I think you will probably not loose more than 1-2 minutes on a 13km climb with 600m ascent, for every 1 kg heavier. Another area that LBS employees are very bad informed about, is full suspension design and the effect of this on pedalling efficiency. People tend to focus on the shock, but suspension is all about how the pivots work. This is maybe a whole new "scientific" topic.

I have seen many debates on the effect of bicycle weight on performance. But just how much can/should you spend on this issue? I found a nice calculator attempting to model power, force and efficiency at http://rjs.org/coeff.html. Although these types of models are highly theoretical, it does help to give broad indications. There are so many variables and any mix of these will give you a different result. I used this model to try and isolate bicycle weight and the effect of this on calories used, with all other factors being kept the same. I modelled three different gradients. The first, an off-road scenario, 13km uphill, climbing 600m (all other factors were kept the same, e.g. tyre type, clothing type, no wind, surface type, etc). The second a perfectly flat scenario and the third, the reverse of the uphill. As expected, weight has the biggest impact on the uphill. The model indicated that for the same amount of work, for every 100g dropped on the bicycle, one will gain about 1-1.25 minutes of time over the 13km (around 1.5-2%). There is, however, a bit of an exponential relationship, with improvements becoming less, the lower you go in weight. Obviously, this is simplistic, as many other factors have an impact, and should there for example be strong wind, the weight benefit is wiped by the effect of wind. Other issues are surface, as these can negate the effect of weight, etc. My suspision is that the real effect is much less, where all factors come together. What the model also shows is that on a flat there is just about no benefit - 0.08% for every 100g dropped. Similar results on the downhill. Would be interested to hear views on this, and where people think the optimum point is if cost and benefit is taken into consideration. As an example, I modelled a high-end full suspension carbon frame bike, coming in at about 11.8kg standard. Swopping out parts for specialist light stuff, it looks like you get to a point of around 11kg where the cost benefit curve shows an optimum.