parabola

The merida gets my vote, such a good looking bike! How much more is the 1000? Comes with fox shocks back and front as well as full XT drivetrain. The wheels are also better. I saw one at the shop the other day and it looked fantastic, the proportions are spot on.

I came across this in one of my textbooks and though it is not entirely relevant, it proves two interesting points. That heavier wheels do not make you go faster downhill (see the red box) That the fastest way down a hill would be spherical wheels! It has to do with the way the rotating object stores its energy. A sphere converts 71% of its potential energy at the top of the hill into translational energy (the energy which makes it go foward). A hoop, which is the closet approximation to a bicycle wheel and the slowest of them all, converts only half of its energy into translational energy. This explains the point of deep section wheels to me, they convert more energy into translational energy than a normal bicycle wheel. So to answer Woofies initial question about "would heavier rims make you go faster" and the answer is NEVER unless your pedalling stroke was an uneven atrocity. In which case it would be more beneficial having professional training to smooth out your pedalling motion. parabola2009-11-27 12:14:08

Thats the problem. I paid using a cheque card, so this is cash directly out of my current account. Basically they stole the money from me

Well, I got my Engineering degree 15 years ago so I like to think that I do too, but after reading this thread apparently not. Looks like physics has changed a lot since then. Maybe my degree expired? I got my undergrad only two years ago and I am shocked at how quickly I have forgotten some basic principles I learned in first year. A quick flick through the physics textbook reminded me that its still there ... somewhere ... I think

I entered the Argus Cycle Tour in September, paid using my cheque card as I do not have a credit card. Today I check my current account balance and they have charged me again for R650 on the 27th of this month. I called the cycle tour office, and they told me it is a problem with Nedbank. I have phoned Nedbank and they assure me that it will be sorted out. I just wanted to tell everyone so that they are aware of this problem. EDIT : banks sorted me out within a few days. parabola2009-12-02 07:43:01

One place I really do feel the weight difference is in my saddle. Its like a big pendulum up there. A lighter saddle makes the bike feel so much more stable under out of saddle climbing.

be careful in prying open the bare pistons, they can easily be damaged. Rather stick to a large flat "wedge shaped" one, called a mechanics screwdriver. And keep the pads in when you do it, rather damage the pads than the pistons. Also its much easier that way. I've struggled so much with my Juicy 5's, but once you get them setup right they stay that way. parabola2009-11-26 15:38:09

You are forgetting about rotational inertia. Rotating mass stores energy as well as the foward momentum of bike and rider. Edman, you are correct but I suspect you have not correctly calculated the rotational energy, which will increase the deficit between adding non-rotating weight and weight to the wheels. Adding weight to the hub only adds linear momentum correct. Check here : http://en.wikipedia.org/wiki/Flywheel Lets stick to the extreme example of a very lightweight frame, with very lightweight hubs, and two sets of rims, one proportionaly heavy, one very light. The rims will help conserve momentum by storing the rotational energy. But you will lose time in accelerating. Over a long, perfectly flat course, where an average rider can make up the time lost from the initial acceleration, heavier rims will win as they will smooth the power delivery from the average riders uneven pedal stroke. Over a shorter distance, the riders benefit from the smooth power delivery will be lost due to his increased initial acceleration time, so the lighter rims will win. For a professional rider with a trained even power delivery, lighter rims will always win, no question. If you start looking at an uneven course, the time depends so heavily on the extra energy required for climbing that it will most likely outweigh the energy saved from the smoothed power delivery by a margin dependant on the ratio of climbing/descending/flats. So its a compound problem heavily dependant on the riding conditions and the conditioning of the rider. However its late and I needed to dig out my dynamics textbook to check this, so there may be more to it. parabola2009-11-27 07:57:43

YES it will work some of the time NO it wont work well YES you will wear out your cassette and chain faster YES you will have endless shifting problems NO it isn't worth the time and energy involved unless you REALLY enjoy setting your gears on friday night. The money you save, you will spend on a new chain and cassette to replace your now buggered drivetrain, and you will buy 9 speed stuff anyway. Unless you are a masochist, then please buy another 8 speed cassette and repeat process until throughly convinced it was a bad idea from the beginning. parabola2009-11-26 14:11:39

Nice work dude. Like the frame. just keep the big chainring on and use it as a bashguard where did you get the frame?

WOW, very nice Interesting seat tube angle

Sounds great, will definitely check it out. Thank you for your efforts!

Having a dingdong day used to be a good thing.... The guys made himself into a household expression overnight. Don't be a dingdong today! Its pretty catchy.

Its a compound problem. It depends on the riders performance as well as the course. Flywheels in a car even out the power delivery and are selected based on both motor performance as well as the course. So it would depend on how smoothly the rider can pedal. A heavier wheel may actually help a rider with uneven pedalling force for example. If the course was entirely flat I dont think the obvious answer would be 'as light as possible' but rather there would be a wheel weight/design which allows for peak performance. I'm just speculating based on the physics, I've never even ridden a road bike for that matter, so take this with a pinch of salt.

All this debating is spurious really. What works for you depends on so much that there is no single solution which is right for everyone. Its dependant on what type of riding you do, your body size and dimensions, and a fair wad of personal preference. That being said, the 650B standard does seem to make sense for full suspension bikes with regards to rear wheel travel. In end you still have to pedal your way up the mountain, and so the biggest limitation on the bikes performance is actually just yourself.

Morewood really got the proportions spot on with this one. They make me so proud Hopefully this bike is going to be huge for them. http://yuris.up.seesaa.net/image/marathon20Zula20morewood20jp.jpg parabola2009-11-26 05:45:59

http://www.rushsports.co.za/blog/wp-content/uploads/2009/10/zula-kwela-geometry.jpg

http://files.nireblog.com/blogs/ateyavana/files/please-do-not-feed-the-hoboken-trolls.jpg

Those new Deores look really nice. I just got my SLX cranks today, went for the double (22-36) with bashguard. Very impressed by the quality of them. CRC's price was R1100 landed. Also got some SLX shifters, seem identical to XT but without the metal levers. I'm getting one of the new 456 inbreds, chocolate creme , wasnt sure about the colour at first but it grew on me. I did consider the summer season but wasn't too keen on the extra weight, and the flower head badge looks so out of place. http://www.on-one-shop.co.uk/acatalog/456_brown_pers.jpg parabola2009-11-25 15:20:04