Project Wide Gravel Wheels v2: Calculating

Scribblins- Gotta measure twice....

 Over the weekend I had a rather unusual opportunity. I was out sitting on the porch Saturday morning, drinking my coffee, watching a pair of House Wrens raise their family in a bird house my son made in middle school, when I saw my neighbor with a load of stuff heading for a trailer he had attached to his work van. I had been contemplating where to go for my ride. It was beautiful, and the day promised to be perfect for cycling. But he looked at me and meekly suggested I could be helping him, so I immediately got dressed for working and proceeded to help move him out. 

He had a ton of stuff accumulated over a span of 25+ years of living there. He had fallen on his luck, his family had pretty much forsaken him, and well..... I decided I needed to help him more than I needed to ride. Anyway....that was Saturday. 

Sunday rained. We needed it, but with Father's Day happening as well, I just had zero opportunities to ride a bike. Either it was raining, or I was with family doing things, and I had little time between either to squeeze in any activities. Besides, I had worked my tail off the day before going up stairs and down in two different houses, carrying heavy objects, for hours. My body was in need of some rest! 

So, what better time than this to do some math! I love math. (sarcasm alert) I also figured that this might be a great opportunity to explain my processes regarding wheel building. So, if you are curious, here's how I go about getting things together before I actually take part in the act of lacing up wheels. Like most things, preparation is key. Get the prep right and the actual act of doing whatever it is you are trying to accomplish will go smoothly and quickly. 

The obvious thing you need up front is compatible parts. Lacing hubs with 28 holes requires rims with 28 holes. I know......but it had to be said! Many times people try to lace things up with non-matching spoke hole counts and for what? It's just not necessary or necessarily the best idea. So, avoid that at all costs. Then the next thing you need to figure out is what sort of spokes you want to use and what lacing pattern is best for your wheels. 

This is all my opinion, so keep in mind that wheel building is something of a religion with some folks. Meaning that they have 'rules' and 'practices' that shall not be broken or you shall be cast to the outer darkness of wheel building! Or something terrible like that. Anyway, I do not buy into that nonsense. I do what I feel are sensible things with a slight twist at times. Read on....this wheel build will be right up that alley. 

Getting the correct measurements off your hubs and rims is critical.

Okay, so I am of the mind that unless the hub manufacturer says you should not lace 3 cross, then you should lace 3 cross. (Rohloff recommends only 2 cross, as an example) I see no great benefits to doing things otherwise and you can end up with issues if you veer off the 3 cross way. But that said, I've done 2 cross, and in some cases 4 cross (tandem), so it is not a hard and fast rule. So, I am doing 3 cross here. Next, the spokes....

I know that people have their favorites. I have mine too. Mine is Wheelsmith. Some folks like DT Swiss. I've used them and I've used Sapim- all good. Stick with the mainstream brands and you'll have success. Nipples? You cannot go wrong with brass nipples. You can go wrong- but not necessarily so - with alloy nipples. If you know what you are doing, alloy is okay. Match the purposes with the material. Run the spokes up past the nipple flange. Okay? Then you are okay with alloy. Otherwise a brass nipple gets the job done well every time. I'll be using brass nipples on this particular wheel set. 

Finally- measure twice! This is critical to getting the math right to determine spoke length. The rim diameter at the point where the nipple seats into the rim is called the 'Effective Rim Diameter'. (ERD) That can be measured in a couple different ways, but I happen to have some old Wheelsmith spoke measuring rods. That's what I use. You can go by manufacturer spec numbers here, but measuring is always best practice. Then you have to measure the hub. 

You'll need three things here- Hub Flange Diameter, Hub Center To Flange on the drive side, and the same for the non-drive side. Sometimes I call it 'non-drive' and sometimes I call it 'disc side' depending upon the hub and whatnot. But the point here is that spoke calculations are made by getting the numbers (distances measured in millimeters) for the flange diameter, (measured from the center of spoke holes across a hub flange) the center line of the hub to the center line of a hub flange, and then that added to what you get for ERD. This- after the calculations-  will determine spoke length. It used to be that hubs were symmetrical, but now days with 'wheel dish' that is not the case, so you have to measure both sides of the hub. Disc brakes also cause 'dish', so make sure you carefully measure front disc hubs as well. 

Once you have all the numbers, you plug them into a spoke calculator. The one I like to use is on United Bicycle Institute's website. It has been really accurate for me over almost 25 years of using it. But there are others. DT Swiss has one a lot of people like as well. Whatever you choose to utilize, just know that the data you input needs to be as accurate as you can get it to help realize best results. Mostly this means that you should be using a digital calipers to get your measurements with. There are other tools, but a decent set of digital calipers for about $25.00 will get you the results you want if you use them correctly. 

Then you buy/order up your parts, (if you can find them) and the next step is to build. I'll get into how I do that for you all in my next update. Stay tuned..........