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Our current Featured Build uses HED Belgium+ or Belgium+ Disc rims, Chris King hubs in your color choice (even mango), and CX-Ray/CX-Sprint spokes. Save $85 over the same configuration as a custom build. 

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Friday
May272016

Spoke strength and wheel strength

We have a lot of wheels to get out today, so I'm going to publish this without some charts and graphs that I'll add a little later. The words will convery the point adequately enough for the time being, but charts and graphs always make a nice impression on management - those guy are short attention span theater, what can I say?

Anyhow, spoke strength is generally expressed Newtons/mm2. To get the functional strength of a spoke, you multiply that number and the spoke's cross sectional area. A CX Ray has a strength of 1600 N/mm2, and an approximate cross sectional area of 1.98mm2, for a total strength of 3168. I say approximate because I give the cross sectional area as if a CX Ray was a rectangle, but it's actually an oval so my stated cross sectional area is a bit high. The total strength and weight per spoke of an array of common spokes is as follows:

CX Sprint: 3564/5.2g*

Race: 3306/5.7g

CX Ray: 3168/4.25g

D-Light: 2928/4.8g

Laser: 2650/4.26g

*Sapim hasn't published the strength yet, so this is a very conservative but very educated guess

Given these numbers, you can see that if you build a wheel using exclusively CX Sprint or Race spokes, you'd need fewer of them to have the same overall spoke strength. The dynamics of a wheel, however, allow us to engineer a little more elegantly than that. 

The most loaded spokes by far are the rear drive side. They are loaded to the highest tension (around 20% higher than a front spoke, which is next), and are subject to the most dynamic forces. Without adequate total spoke strength (spoke per strength times number of spokes), a rear's drive side spokes will slightly elongate over time, and won't have adequate strength to cope with the dynamic forces that they see. The front spokes are fairly highly tensioned, but a front wheel is symmetrical and doesn't see near the dynamic loads that a rear wheel sees. A front wheel built with 20 Lasers, depending on the rim and hubs used, will do pretty extraordinary duty without batting an eye. The rear non-drive spokes? They're kind of along for the ride. They get loaded to a maximum of 50% of the drive side tensions, they see less torque than the drive side spokes, and the rear hub's left flange placement means that they don't have very hard work to do to keep things in line. 

Given that, you want a ton of total strength on the drive side rear, and you need somewhat less on a road front (disc fronts act similarly to rim brake rears), and you don't need very much on the non-drive of the rear (or non-disc side of a disc front). Against that, you are going to balance weight. The lowest weight at which you can get adequate total strength is the best.

You also have a couple more things to consider. One is points of control. When you build a wheel, the more spokes you have, the more opportunities you have to correct minute rim issues. If the rim has a hard spot, more spokes allow you to taper that correction by making small corrections to several spokes rather than larger corrections to fewer spokes. This makes a better build, and the points of control also work for you in counteracting stresses that the road puts into the wheel. Many hands make light work.

Another thing is simply redundancy. My dad was an aeronautical engineer for his entire career, and did some pretty neat stuff. A trip to Udvar-Hazy with him makes for a very interesting day (and a lot of "I don't know if that's actually been declassified yet"s). Anyway, one of his cliches is that you strive for infallibility but you always use redundancy. If a spoke breaks on a 20 hole wheel, or a 24h rear, your ride is almost certainly toast - this is not a blanket statement but it's generally accurate. The more spokes you have, the less true that becomes. With 32 spokes, if one breaks you rip out the debris and ride on, maybe you have to open your brakes a little. On a race wheel optimized for lightest weight and absolute best aerodynamics, sure fine. On a wheel that you rely on all the time for all of your riding, or on which you are going to go out into remote places beyond "honey can you come pick me up?" Not so much. 

Okay, so that was long, and miles to go before I sleep and all of that, but with that done you have a very good picture of a lot of what we're thinking about in terms of spokes when we recommend a particular setup. 

Have a great Memorial Day weekend, and please keep in mind the staggering volume of day drinking that America does this weekend - please be careful on the roads. 

Thursday
May262016

Wheel Stability

Wheel vocabulary is a challenging thing. The number one thing that people request in wheels is stiffness, of which there are basically three elements - torsional, radial, and lateral. Coming in almost tied with stiffness is the request for light wheels, and then durable, low maintenance, tubeless, all black, etc. The incidence of "how few spokes can I get away with" (always phrased that way) seems to be in decline. 

Torsional stiffness is a wheel's ability to resist deformation from drive train torque. It would take a really bad wheel to have notably poor torsional stiffness. Radial stiffness is your wheel's ability to resist deformation when the spokes face an inward load. People fear too much radial stiffness because they don't want a harsh ride, but a wheel that deformed by 1mm - which is a HUGE amount for a wheel to deform, as the tightest of spokes would go dead slack with 1mm of deformation - doesn't offer anything like the suspension offered by tires. If your wheels feel harsh, we think the tires are the first place to look. Letting 5 or 8psi out can transform a bike. This whole phenomenon is why we got on the wide tires train a long time ago, and then went deep into wider rims right away.  

Lateral stiffness is really two issues. A stiff rim in an underspoked build will stay in plane, but will move off axis relative to the hub. Most "my rear wheel rubs my brake pads" issues are this. A soft rim without enough spokes will come out of plane at the rim, which doesn't evidence itself with brake pad rub, but they'll feel mushy, handle poorly in turns, have poor durability, and other things. Neither is a good situation. This article does a great job with it if you want to go deeper.

English Cycles narrow TT front hub, photo by Bikeradar.com

Recommending a particular build for a particular use has to take in a lot of elements. Rider weight is often the flagship variable, but how a rider rides is at least as significant. If you stand and hammer up every little incline, you place more demands on your wheels than a heavier rider who sits and pedals smoothly. Time trial and endurance event track riders can use front hubs with really close flange placement, which reduce frontal areaand improve aerodynamics. Ride that hub in a crit, though, and you're just not going to make the turns - you'd have crazy understeer. Durability is increased by increasing spoke count, but one size doesn't fit all - for some riders a 20/24 build can be super durable, depending on the components and how they ride. Redundancy is always increased with more spokes - if a spoke breaks in a 32 spoke wheel, your wheel might not even come out of true very noticeably, and that's nice for touring or heavy training in crappy weather or remote locales.

One of the more interesting questions we've been asked recently is why we offer 24/24 and 28/28 in disc, but not in rim brake builds. We didn't know that people didn't know that. The simple answer is that a disc front wheel is dished (the hub flanges are not equidistant from the hub's center), and it transmits torque from hub to rim (because the brakes stop the hub, not the rim). The dish makes the wheel less strong and stable, spoke for spoke, than a rim brake front, while the brake torque transmittal increases the need for strength in the wheel. In a rim brake build, if your front and rear have the same number of spokes, either your front is overbuilt or your rear is underbuilt. In a disc build that's not the case. 

The point here is that no single element exists in isolation; two riders of the same weight could be best off with the exact same build or very different builds, depending on the other criteria. Next we'll look more into spoke type and strength, and balancing spoke, rim, and hub characteristics. 

 

Wednesday
May252016

CX Sprint Spokes

Sapim recently made CX Sprint spokes available to wheel builders. The CX Sprint is a very slightly wider version of a CX Ray. A CX Sprint is to a CX Ray roughly as a D-Light is to a Laser. And that becomes an important comparison for us.

Previously, they'd been an OEM-only spoke for builders of massive scale. We're an OEM too, I know, but we don't have anything like massive scale. The most notable use of CX Sprints is by Zipp in their Firecrest series. As they introduced the Firestrike and NSW lines, they switched to CX Sprints all around in Firecrest. So this isn't some Johnny-come-lately spoke that's got some freak use profile. 

This blog started out quite differently from how it's going now, and as I got into it I realized that it would have to be cut up into probably 3 posts. So there's a bunch of sort of technical stuff and links to previous blogs to show once again that yes we test all this stuff, and that will all be included in subsequent posts. Think of this post as the liberal arts segment of the topic.

The hydrangeas on the porch are about to bloom, and are much nicer than boring spoke photos

As Mike has eloquently pointed out in recent posts about feature builds (and the current one is a good one), people continuously ask us for bladed spokes. Objectively, they do some very nice things, but subjectively we've always considered that as a value play, what they do wasn't really worth the price of entry for most applications. The message from the market in general is "yeah, screw that, I want them anyway." So we're making some streamlines to the product mix that will emphasize bladed spokes. And the majority of those setups will include CX Sprint spokes on the drive side of the rear and the disc side of disc front wheels. 

We've become big fans of differentiated spoke selection on the load and off side of many wheels. We've been doing it for almost a year and there's no question it works. We did a few test builds with CX Sprints and we like what they do there as well. So as we align more with customer request, we'll integrate CX Sprints into the mix there. And there will be instances where we'll be able to make slightly lower spoke count wheels work for more of you (what do you people have against spokes, anyway?!?!?!? - just kidding).

Some pundit among you will point out the cost difference and raise that as our hidden agenda. Retail on a CX Sprint is $.50 less than for a CX Ray. As you can imagine, our cost difference as a large-ish buyer of spokes is just a portion of that. We're using them for at most half the spokes in a wheel set, our pricing to you reflects that pricing, and if we weren't convinced that there is a benefit we wouldn't do it anyhow. Rails aren't going to use CX Sprints because quite simply, they don't need them. The shorter spokes and greater bracing angles of deeper rims mitigate the benefit. 

This concludes the liberal arts portion of this discussion.

Friday
May202016

Matchmaker matchmaker

Selling wheels is actually hard work. The differences that do exist between wheels are reasonably contained (let's face it there are some bad wheels out there, and there are also wheels designed around divergent purposes), so when you're earnestly trying to help someone make their best choice, rather than a just a good choice, it's kind of a full contact process, mentally speaking. It's also time consuming. 

The way it works out, selling the wheels is the only way to monetize that consultative process, and that's the way it works out in most retail-ish things. I'd actually love a business model whereby we just took a fee for consulting wheel purchases for people. The sales/service side and the operations are both hungry beasts, and HAH! if you think you can multi-task them. And please - sales isn't a dirty word - in your life as a consumer, good salesmen/women are some of the most valuable people in your world. They help you spend your life using things that add value to your life instead of things that suck. But the operations are how you get paid for the sales/service part, that's just how it is. And the price of the goods has to reflect the cost and value of the sales and service, otherwise the supplier is screwing himself. 

We actually steer most people towards our lowest margin wheel set, which is the opposite of what most sales organizations do, and is actually pretty dumb from a business perspective. We'd supposed that the benefits of that set would be so self-evident that it would involve about as much of a sales process as someone buying a Coke in a gas station. What's happened as often as not is that said product is a better fit and value for the customer's needs than some higher margin thing they'd originally asked about, and we wind up spending a lot of our very finite time explaining that. So that's something we have to look at, but we aren't going to shut down the sales process side. To do so just wouldn't be us, and we enjoy it anyway. But it's worked out that we're kind of punishing ourselves for doing a good, so we have to look at it. 

We've always been, but seem to have become more so recently, a high touch supplier. Pretty substantial pre-sales contact is the norm, as are post-delivery follow ups. And we like this, it's a natural fit for us. There are instances when it gets a bit excessive, and we struggle with those. We have a weakness for trying to make sure people feel well served. We're also small, so when you contact us, you're going to hear from one of the guys who's stood there in the wind tunnel, or done the brake heat testing, or measured all the tires, or burped the tubeless cross tire that didn't work as well as it was supposed to. The flip side of this is that we're small, so as we're trying to give you perfect info, there are also things that aren't happening then. It's part of running a small business. 

 

Friday
May132016

Superstition, the Mosaic Theory, and Sheldon Brown

It's Friday the 13th. Make of that what you will. This ends the superstition portion of today's blog. 

Mosaic Theory generally applies to investment management. The nickel tour of the concept is that an investment manager takes a huge array of information, directly-, indirectly-, and seemingly unrelated to a specific company, and fits those pieces together to form an overall picture - a mosaic, if you will - of the company's (and thus its stock's) prospects. The negative connotation is that it's used to cover insider trading, which it undoubtedly does. We live in the real world, people - the truth is stanger than Bud Fox, Gordon Gekko, and Bluestar Airlines. But the Mosaic Theory does have an accepted positive connotation, and there's no denying that some investment managers have a spidey sense that's no doubt attributable to some form of "mosaic" principle. Peter Lynch, Bejamin Graham, Warren (no relation to Jimmy) Buffett - they've all written extensively about their stock picking methods, but they also definitely picked up on a lot of things other people missed, and were able to make better cohesive wholes out of disparate pieces.

What does this have to do with bicycles - a question we've caused you to ask innumerable times on this here venerated web log, or "blog" as the kids call it. Well, I'm about to tell you.

When bikes are your job, and you're generally a pretty obsessive sort, you're constantly tuned into things. We must have spoken before about the way we triangulate things - piece of information A relates to piece of information B in such a way, and they both relate to piece of information C, that piece of information C obviously either does or doesn't make sense. We do this constantly, continuously even. 

You who are reading this are probably generally inclined to believe that we have general truth as well as your best interests at heart, hopefully mostly because we've given you good reason to over the last gazillion posts and other actions (and Mike is currently prepping a big site shift so we have recently counted the blog posts - gazillion it is). Sometimes we wade into forum topics and provide a perspective, and people assuming we've got an agenda that we just don't poke their virtual finger into our virtual chest and say "show me the proof." Well, we might have ready links to two or three things that could begin to give an impression of the overall picture. But the real and honest answer is "pay withering attention to this topic for ten years, read thousands of pages of background info, with senses that are tuned not only to what information is presented, but also to who is presenting it and how their presentations are generally shaded, within the context of the overall zeitgeist surrounding the topic, and bring to bear all of your disparate experiences and seemingly unrelated knowlege, and have your professional life depend on your ability to make an accurate picture out of that, and you will see my point better." I've never actually written that in a forum, but I might someday, because it's the truth. 

I say this as reverently as is possible to do - a TRUE bike dork

As part of this, we've probably reached a point where many people are unfamiliar with Sheldon Brown. He died getting on toward about a decade ago, and a lot of people riding bikes now probably weren't riding bikes then. Since the info on his site is getting a bit dated these days, it's not quite the constant reference it had once been for me, but it sure is always there as a background. The number of hours I've spent poring (and that's the right way to spell that, btw) over the info he accumulated, developed, and shared provide a HUGE amount of my personal "bike knowledge mosaic." Compared to Sheldon's, our interest in bikes is quite narrow, but sometimes you read something about a Sturmey-Archer 3 speed hub from 1970 and it helps you figure something out about today's hubs. Even though he was as good as anyone was at early internet cataloging (I have no idea if that's the right way to spell that, btw) and linking, at some point all the freaking absolute imperial tons of info he shared just sort of coagulate into "mosaic."

I don't have any idea if Sheldon would take any joy in my remembering him on a Friday the 13th, but I specifically, along with cycling in general, owe a huge debt to the guy. He was one of a kind.