From the web.... Letter to Sram Hi: I have been a user of your chains for some time on a variety of bikes equipped with Shimano and Campag and 7, 8 or 9 speed, and in the interests of extending the life of cassettes/sprockets and chains I have recently begun to study a little more closely the various models of chains you produce. I note from your website that a number of models are described as "step riveted" whilst others are "cross-step riveted" or "cylindrical". I can see that the latter pertains to the new hollow pin chains, but I wonder if there is any difference in strength/longevity between these various joining methods? What are the relative merits of say the PC-48 and the PC-58 and PC-68? As you go up this product ladder there is an increasing amount of nickel plating, but I assume this applies only to the side plates and that the pins and rollers of these three chains are identical - is this correct? If so, is it reasonable to argue that, so long as the chain is kept lubricated against corrosion, the PC-48 will perform as well as the PC-58/68? When it comes to the degree to which a chain can be used before it becomes dangerously weak (and leaving aside any issues of accelerating sprocket wear) what would you say the maximum amount of acceptable wear, measured in lengthening of the chain pitch, would be? Also, although you suggest in your FAQ using de-greasers/cleaning solvents, you advise against removing the chain and leaving it to sit in such degreasers - why is this? I ask this because I am interested in learning how best to clean and lubricate the chain for long life. It seems to me that many de-greasers do a good job of cleaning off the external parts of the chain, but I wonder whether when it comes to the internals, all they do is dilute the mixture of oil and metal that gets inside the rollers? I hope you can educate me on these questions. Peter Faulks Reply Dear Peter, My name is Mark Pippin. I am the product manager for chains at SRAM Corp. I was forward your e-mail a couple of weeks ago. Sorry for not getting back to you earlier, I have been on the road. Let's see if we can answer some of your questions. Re: Riveting Process The goal of a riveting process is to deform the metal rivet to prevent the opening of the chains side plates under load. The ways that you increase the strength of the chain riveting process is by A) increasing the displaced amount of metal of the rivets and B)the thickness of the outer plate. Re: Rivet Types: At SRAM we use 5 different levels of riveting. 1)Standard Rolled Rivet: The fastest, cheapest, and least strong riveting. What happens here is that the chain is pulled thru a set of round dies that deform the rivets. This is used on single speed non-derailleur bikes. It also has the tallest rivets, and receives the least amount of side loading. So it's weaker, but in it's usage pretty darn strong. 2)Step Rolled Rivets: This is also a rolled rivet, but much more precision and slightly slower in processing speed. This type of rivet is shorter/flatter and is used on our basic derailleur chains. It's has about 50% more Push Pin Power than the Standard Rolled Rivet process. It's about 1500NM's (sic). The step riveting is moving more material than the standard roll riveting. 3)Cross Step Rolled/Stamped Rivets: Is a double riveting process that rolls the step rivet, then hits it again to displace more material. It's one of our strongest types of riveting at over 2000NM's. With all the above methods of riveting, the hole in the side of the plate is straight with no draft/radius. So the deformation of the rivet flows over the outside of the link itself. 4)Cylindrical Riveting (Hollow Pin type): With this type of riveting, the material is displaced into a chamfered/tapered hole and the thickness of the plate plays an important roll of the Push Pin Power. For example, our PC89R Hollow Pin has a PP Power of 1500NM's, while our PC99 Hollow Pin has one of 2000NM's. The difference is that the 89R uses .90mm plates, while our 99 uses 1.0mm plates. Cylindrical riveting is much slower since it must strike every rivet individually. 5 Round/Orbital Riveting: This is our strongest rivet, but is only used for Power Links. It is pretty tall and displaces a lot of material, but is not really a good method for the complete chain. Chains must be cut a couple times in their lives, once to obtain the correct length and a second time to be adjusted to the bike. This rivet is almost un-open able and would cause problems for both us on the production side and also for the consumer. We use it on our Powerlink since this rivet will never be opened. Re: Durability of a rivet. In general, there is no major difference in the rivet method vs. longevity. Yes, you could argue that a larger displacement of materials would offer more longevity, but only slightly. Durability of a chain comes from the hardness of the pins and of the inner links that ride on them. We are doing a research project with the University of Coimbra on what causes chain stretch. Chains really don't stretch, they are just wearing out. Yes, in extreme cases the material of the outer and inner link could deform and stretch, but this is rare. What is happening is that the rivet pins and the inner links are wearing. Re: Differences in Models. In many cases, what is changing is the plating, but the underlying materials are the same. So, you are correct. The only caveat to that is the all the materials thickness and process (heat treatments) are [not] the same. Please note that we do not use the same links and then just change the color at will. If we are going to do a nickel outer link, we would have to change the hole size for the rivets to compensate for the nickel plating. Yes a chain is that precise. Re: Replacement. This is a tricky one. You could argue that any change in length above 12.7mm pitch, you should change [the chain]. You need to remember that there are 114-116 links times x amount of wear. It does not take much to cause a chain to get too long and start to effect the rest of your drive train. I would say that most of the chain length testers are pretty correct to use for a guide. Sorry that I cannot offer a more precise answer on that one. Re: Cleaning of chains. The reason why we do not suggest leaving chains in a solvent tank is because it takes out all the lube between the pin and the inner plates. If we could make sure that people would then use a liquefied grease, then let it cool, we might suggest that people clean chains in a solvent tank. This is how we do it at our factory. We recommend that the user use cleaners that only attack the outer surfaces of the chain to take away the dirt and grime then re-lube. I personally have only used a rag to clean my chains for years and stay away from solvent tanks and jet washers. It's cheaper to replace a 10-15 dollar chain than it is to replace a Ti cog set and an XTR chainring set! I hope that this helps you better understand chains and SRAM chains in particular. If you have any more questions, feel free to ask. Best Regards, Mark Pippin SRAM Product Management
