Johan Bornman

I'm sorry.

Thanks for the link. It seems like it uses Patrick's suspension design, which answers some of my questions. The snake picture also changes the way I pronounce Vipa.

I don't see Pat Morewood's name mentioned anywhere in the post to which I'm responding. But you seem to have insider knowledge. Who designed the Vipa and other Momsen bikes? Were these designed from scratch? Is the suspension system unique or under license from someone else? I'm trying to get behind the term "design" as used in this thread.

With respect to Victor, with whom I have no beef. I don't know him and it seems like he has a successful business going. I wish him all the best and I find joy in seeing ZA entrepreneurs doing well. Designing a bike is not as easy as it seems. In the old days where bikes were brazed from tubesets and cast-iron lugs, lots of people called themselves designers, including a few successful ZA frame makers, I would imagine. Reality is, all the design was in the lugs, where the angles, offsets, stresses and strains, were all built into the meccano set pieces which were commercially available from several lug manufactuers, including the likes of Cinelli, Ceeway and others. All the builder had to do was select the appropriate lugs, cut the tubes to the customer's size, assemble it all on a jig and braze. I also made myself a bike like that, one that I still ride today. This is not bike design. Modern bike design would require actual design and engineering skills. This is particularly true for carbon bikes or aluminium bikes with hydroformed tubes. Keep in mind that the creator of a bike has an obligation to the end user in terms of safety and will understand the materials he or she is working with well enough, to ensure that the end product will not fail catastrophically. Only engineers are trained to do this. This obligation becomes particularly difficult to manage with the market forces that dictate minimum weight. This effectively leaves no margin for error. A particularly critical component is the fork. Very few bike companies design their own forks and usually outsource this to specialist like Reynolds, Dedaccia (SP?) and the likes. I have no idea how one goes about getting a Taiwanese company to make a bike for you but I would imagine that you either give them a CAD drawing and very specific parameters or, you leave the design work to them and make cosmetic decisions such as the curve of the top tube, the profile of the chainstays or whatever. This is the engineering equivalent to colouring in by numbers. I have seen some Taiwanese catalogue frames and have come to recognise many design artifcats in some of the bikes available in ZA under various brands. These frames are all the work of one designer or one master engineering organization that does work on behalf of others. One way of working around the "Designed in South Africa" problem (if you want to be perfectly honest) is to fly a bike designer over to South Africa, put him up in a hotel in Sandton and tell him to not emerge until his has finished the design. That would technically be a "designed in South Africa bike." Personally, I don't care where something was invented, designed or manufactured. I attach no value to these designations but I do see the marketing value in playing the patriotism card or the "Made in Western Germany" ace. I own some excellent goods made in China. If Mr Momsen indeed designs his bikes himself, I have to assume that he is either an engineer or has an engineer checking his work. The liability otherwise is huge, not to even think about the cost of a recall.

Glad to hear they're getting with the program.

I like your optimism but I doubt much design happened in ZA. Bike design is best done by mechanical or structural engineers with a good working knowledge of a) the industry and b) the material in question. Then, you would need access to a facility that can make a prototype so that it can be tested. I doubt any of this happened here and that local sales can justify such an upfront cost. At most, the frame was chosen from a catalogue of available designs, perhaps even with some options such as cable routing, BB type etc. It's a little bit like that little Swiss flag on a Volcan. The closest thing Swiss to that design was the cheese on the sandwich eaten by the owner whilst browsing the catalogue. All this doesn't make these bikes bad, or good for that matter, it just says something cynical about patriotism.

I've repaired cage damage before by laminating a piece of aluminium to the carbon with epoxy. I shaped the alu to exactly the same outline as the cage and glued it on. However, that was for a broken cage. It would depend on what sort of damage you have.

Hmmmm. The old "CO2 freezes Stan's into balls" myth all over again. It's a chemical reaction that causes the latex to crash from the solution, not a thermic reaction.

I also like it's lightness, and the simple foolproof lock. However, modern stainless steels make nicer blades. Carbon steel rusts like crazy. I took my Opinel with me on my kayak when I went to gather mussels the other day and even though I didn't use it and it remained in my life jacket's pocket, the next day it looked like an old shipwreck. Carbon steel got some good PR when Hannibal Lecter claimed he only uses carbon steel blades when he cuts up his victims and cooks their brains...or whatever it was he did with his pursuers. I bought mine in France a couple of years ago when I was stationed in a town (can't remember its name now) where I was doing a technical course with Marzocchi. The town's one claim to fame was its Opinel factory and every shop, hotel, café, canteen and magazine shop sold Opinels. There is a post here about Okapi, I didn't read the entire thread but I hope no-one confuses an Okapi with an Opinel. An Okapi is a bit of a fokapi if you ask me. Absolute rubbish but in my childhood, every boy wanted, and eventually owned, an Okapi. Our special trick was to grind down the cam on the blade so that with some skill, you could flick it open.

Your biggest problem with sandblasting is not the rough surface problem as mentioned. Modern aluminium frames, especially super lightweight frames like basically all of them above R10k, are shot peened or laser peened. This is like sand blasting but with special beads, probably glass, that finely peens the metal giving it some surface tension and thus crack resistance. Peening is done in addition to heat treatment because the metal is drawn so thin that it needs every bit of help it can get. The beads they use are small, 0.3mm in dia or so. Peening would leave the surface looking like some of that fake antique silver or pewter ware, if you were to look at it under a low power microscope. By sandblasting the aluminium, you remove the peening and weaken the frame. Peening is one of the reasons frame manufacturers will void the guarantee if you were to repaint it. It isn't the paint job that does the damage but the surface preparation over which they have no control. I suggest you use paint remover and very little sanding. That said, if it is an el-cheapo frame with welds that look like chicken poop and toothpaste, blast away.

Opinel is all lore and no substance. It is made from very hard steel, carbon steel, and the entire blade is uniformly hardened, which means the tip breaks off easily. It is very difficult to get an edge on these and in my experience an edge doesn't keep on it either. It's a bit of a French thing, either you like their stuff and put up with the quirks, or you hate it. Me, I'll rather not have a Citroen, thank you.

You can say that again. Truck rims are two-part affairs and it is quite common for them to separate upon inflation. Considering the high pressure these things require, it is a bomb in a workshop. Tyre workshops are supposed to inflate those tyres inside a cage of sorts. In the video I though the cage in the background was one and I wondered why he wasn't using it, until I noticed that it was a liquid container cage, not a tyre cage. People die from such accidents.

Don't put too much money on it since contaminated brake fluid is still incompressible.

Disclaimers like "probably" doesn't get you off the hook. A contaminated brake will have exactly the same feel as a properly working one and there was no need to throw in solutions to other brake-related problems. The OP stated clearly what the symptoms are and deserves either a sensible answer or silence. Throwing a bunch of red herrings on the trail doesn't help him solve the problem nor does it help the understanding of hydraulic brakes.

It is perfectly possible but there is an easy way to check for frame alignment. Remove the wheels and suspend the frame in a bike workstand of sorts. Improvise if you don't have a stand i.e. put it upside down for instance. Now take a ball of string and tie it somewhere, say the rear dropout. Wrap the string around the frame in a symmetrical way. Through the dropouts, over the headtube, around the seatpost etc etc. Like a bicycle macramé. Now look at the gaps on the left and right between string and frame. It is very, very easy to spot a misalignment like that.

I don't see how improperly bedded pads can affect the take-up position of the brakes.

That's a pretty unusual length for a 26" wheel. It is either a hub with a very small flange or a rim with shallow profile or both. Are you sure of the length?

Roller bearings don't perform as well as ball bearings when they cannot run in oil. Unlike ball bearings they don't recycle the grease but tend to displace it and eventually run dry even though there is grease in the bearing cavity somewhere. Ball bearings are the best we have for now. Although cartridge bearings are a poor choice for wheels since they can't be preloaded laterally, they are easy to install and maintain by inexperience and unskilled mechanics. But to answer your question, no. I don't know of a hub that uses roller bearings.

It is a 6806 bearing. Ask for a 2RS6806, the oke behind the counter will know what it is. If you are interested in the code meanings, the number denotes the bearing ID, OD and width, as well as the type of rolling element, in this case balls, in a single deep groove. The RS loosely translates to Rubber Seal. The 2 in front of the RS (sometimes put behind) simply means two rubber seals, one either side. Your supplier may use another type of rubber, denoted by say LLB. Don't worry about the rubber type, you just want two rubber seals, one either side of the bearing.PS, I haven't worked with this for a while, so just double check by asking the supplier to see if the ID on a 6806 is indeed 30mm. Alternatively, just go to SKF.com and check the dimensions. These are published. SKF sometimes uses an extra digit somewhere, ignore that, look for the base code. Dimensions remain the same no matter the seal type, rubber, steel or nothing.

Hmmm, infinite loop. Nope, that is still a Hollowtech (II) crank. As I said, Hollowtech is not all that obvious. Hollowtech (subsequently renamed as Hollowtech I) refers to a hollow forged crank and Hollowtech II refers to the 24mm axle. It would be safe to say that the Shimano trademark Hollowtech refers to both the axle dimensions and the method of forging in the crank. It is silly but that's Shimano for you. Have a look at your Shimano manual. In the back they have several pages of glossary with nice icons and diagrams. Over and out.

I don't have a Shimano catalogue anymore, but in the back they explain all their idiosyncrasies. Have a look at this video, where Hollowtech II is all about the axle, not the crank. http://cycle.shimano-eu.com/publish/content/global_cycle/en/nl/index/technologies/hollowtech_ii.html

Not strictly, no. Hollowtech II refers to the 24mm (at both sides) crank shaft diameter and not the fixture method of the BB to the frame, In other words, a Hollowtech II crank can fit into an ISO/BSA BB, a pressfit BB or even Italian thread BB. Speaking of the latter, I just want to add a little detail to your description of Italian thread BB - Italian also uses right-hand threads on both sides of the BB whereas BSA uses left hand thread on the one side and right hand on the other. Then there is that other evil BB Right. What the hell were they thinking?

Greetings. No, the OP is right. Shimano has two Hollowtech "technologies". One is the hollow forged cranks and the other is the hollow crank shaft of the so-called two-piece crank with a hollow 24mm shaft. I can't remember which is which, but one is called Hollowtech and the other Hollowtech II. This is all very confusing, since as you said. Octalink is also hollow and actually if anything, should have been called Hollowtech I. I think however that Shimano is trying to pretend it never perpretrated Octalink, it is such a big flop and ill conceived.

How did you notice the increase in speed and how much of an increase was there?

I agree that it can help - for the first dry stroke. Thereafter the oil is wiped off the stanchion and sits in a ring above. A wiper in good condition will not allow more than a boundary layer of oil to remain after a stroke. If the oil is supplied from the inside, a stroke leaves a layer. If that oil is supplied from the outside, a stroke leaves a layer, Excess is wiped away, Only once the wiper and oil seal starts to wear and it doesn't wipe as efficiently anymore, then the thickness of each layer increases. I therefore maintain that external oiling is a waste of time, especially so if the seal is ageing. I'll try this analogy. Take a rubber blade squeegee and clean a window. Wet the window first, wash it with soap or whatever, and then dry it with the squeegee. Notice how the squeegee leaves behind a boundary layer of water. You have to look quickly, because that layer evaporates quickly after the swipe. Now try and get the window ever wetter. Wipe again. You'll see that the layer remains the same no matter how you wipe. The same happens on the fork, just the boundary layer remains. The only difference is that it doesn't evaporate but says clinging to the stanchion thanks to the stanchion's dimples and the fact that oil doesn't evaporate. Any subsequent applications of oil gets shifted to one side, evident by an oily ring at the highest point of the seal's travel (lowest point of compression). So yes, it doesn't do any harm and it isn't any trouble to apply, but it has no effect whatsoever on stanchion lubricity. My only assumption here is that the fork still has bath oil inside and that the bike is ridden so that the foam ring is wet. It will not work on a bike on a stationery trainer where the fork is not agitated. But, that's not a real application.