abdon 

My google-fu is failing me! What's the formula to calculate the amount of dish? Say you got a hypothetical high flange campty Gran Sport nuovo typo, 120mm axle, 54.5mm flange to flange, what would the amount of dish be?

I went to Sheldon Brown and while the article kept talking about dishing this and that, it never bothered to mention the formula.

Bill Kapaun

Why worry about it?
You center the rim between the lock nuts.

FBinNY 

I suspect the magic number you're looking for it the Center-to-flange or CTF distance. It's easy enough to measure by sdtting the hub with the locknut against a flat reference, (like the edge of a table) then measuring to the flange. That's the flange to end distance, which when subtracted from half the axle width will give you the CTF.

If both flanges have the same CTF, as do front hubs, the wheel is symmetrical, or not dished, or have zero dish depending on who's talking. If the two flanges have different CTFs, you're building a dished wheel, and the spoke lengths will be different (roughly 1mm/10mm of difference), and the tensions will be different and roughly proportional to the CTF distances (reversed).

Jeff Wills

Download the Spocalc spreadsheet: https://sheldonbrown.com/rinard/spocalc.htm . It contains measurements for many, many, many hubs. It also calculates the correct spoke length for whatever whackdoodle wheelbuild you're planning.

I have a 24-spoke Campy Record hub laced to a 17" Sun/Moulton rim. Spocalc spat out the correct spoke length for 2-cross lacing and yawned.

Reynolds 

+1. You don't need any numbers, just check both sides with a dishing tool, that's all.

fietsbob

Rim is to be in the center of the axle ends,
to make room for the sprockets on the right ,
the hub is not in the middle . dish is the compensation ..

FBinNY 

Yes, you always dish the wheel to the center of the axle. But you also want to know how far from the center between the flanges this will be, so you can make decisions like spoke length, whether offset rims might make sense, and whether you want to use different gauge spokes left and right, all of which depend on knowing in advance how much dish you're looking at.

CTF differential is the first thing I consider when someone hands me a pair of hubs to build a wheel around.

Reynolds 

I was assuming the calculator gave the values, and the wheel was already built.

FBinNY 

That's possible, but if the OP is asking about how to dish a built wheel then he needs to go back and review the primer.

abdon 

I'm talking rear wheel, a front wheel is not dished. You check to see if it is dished but I wouldn't be trying to calculate anything for that.

I feel stupid, I should have been able to figure it out: Measuring front the outside of the nut to the near flange, the different between the long side minus the short side divided by 2.

Looigi

I generally don't think about it at all. I just bring the drive side up to tension, make sure it's radially true and the DS spokes have even tension, then tension the NDS to laterally center and true the rim. This is possible because the cone angle on the drive side is so small that moving the rim toward the NDS to center it doesn't affect the DS spoke tension significantly. I find a front symmetric wheel is more difficult in that I need to tension left and right spokes as the same time.

FBinNY 

You got it. (see post 3). But on a finished wheel, why would you care?.

abdon 

I never said this was a finished wheel, I'm lacing an old campy hub to a new rim. I haven't laced wheels in a while, a rear one in even longer, and couldn't remember the darn offset.

cny-bikeman

Then some of the earlier posts apply - you don't need to know it ahead of time. Knowing the amount of offset does give you any info you can use in building the wheel. Just turn the DS spokes a couple extra turns as you tension, check the dish, and then adjust as necessary. Most experienced builders combine tensioning and dishing, so that if you need more tension and dish you tension drive side only for a round.

FBinNY 

OK, but the only reason to worry about dish, is to plan things like spoke length. Otherwise, as all here have pointed out, it's a moot point because wheels are centered between the axle ends using a comparison tool like a dishing gauge.

In case you don't have a dishing gauge here's an alternative.

Raid the pantry and find three identical cans, such as soup cans. Arrange them on a table in a triangle supporting the rim like a tri-pod. With the near finished wheel (must be reasonably aligned to dish accurately) supported on the cans, stack quarters (or whatever you have) up to the face of the locknut (not the end of the axle). Note the gap if any, and flip the wheel. A correctly dished wheel will match with the gap being the same.

If checking dish before completion, and the wheel isn't aligned spot on, rotate the rim & test at multiple places to allow for alignment errors. In this case you want a rough dish, and will confirm when the wheel is finished.

abdon 

FBinNY, before I forget thanks for the answer. It got me on the right track from the get go.


Why does people keep guessing what is not being said?

I have a wheel on my lap, I just finished lacing the spokes on the wheel. It is a rear wheel, that needs to be dished. Single walled rim construction. Once everything is tensioned I'll hit the sticking spokes with a file to stop them from poking the inner tube. The file is an American pattern, single cut. All I needed was the formula so I could figure out that I needed to dish it 6.4mm.

cny-bikeman

Not guessing at all. You asked a question and several members who have extensive experienced answered, and then further clarified when the intent behind the question was more clear.

If you need to dish 6.4 mm how do you intend to use that information? It's just silly to try to measure that amount - there's no need to do so, and it would be very difficult compared to using a dishing tool or FB's method, both of which tell you whether the locknut face to rim distance is the same on both sides. I don't see what relevance the file has, unless that's an attempt at humor.

FBinNY 

You're welcome. the reason folks keep guessing at what isn't said, is because what isn't said is often the key to the problem or correct answer. Givong a complete picture early on spares everybody the guessing game.

If you read the posts, mine and others. You don't dish by the numbers, you dish to the result --- symmetry over the lock nut faces. Put away the ruler, don't measure and calculate. Borrow the requisite soup cans, build the dishing gauge I described, and dish the wheel the same way all the experienced folks are telling you.

abdon 

Folks, the question was simple, how to figure out dish dish offset. My dishing tool and digital caliper worked just fine. Stop over thinking, life is often this easy.

cny-bikeman

It is common on this forum for persons to ask a question that entails within it an incorrect assumption or assumptions. When it's unclear what the purpose of the information requested would be it is perfectly natural, and in some cases critically important, to clarify the purpose behind the question, so that an answer can be given that is both accurate and relevent.

If you have decided you have the information you need then that's great - horse delivered to water.

Zef

This thread should probably be locked as it seems like it has potential to get unnecessarily ugly and the initial request for information has been satisfied.



-j

FBinNY 

No need. The OP has his answer, and there's little likelihood of any ugliness. Every poster is sincerely interested in helping, and I suspect the OP knows that too.

This forum is nothing like the A&S forum, and not as prone to the types of interpersonal fights we routinely see there.

nhluhr

Please, since you're apparently the expert, tell us exactly how you used this value once you calculated it. I'd love to know more.

FBinNY 

Guys, please don't make Greenfieldja right by showing that we can't be considerate even if we disagree with something.

The OP asked a question, we answered, and though we may disagree with the OPs approach, it's his life and there's nothing to get worked up over.

BTW- it's almost Thanksgiving, how about we try to enjoy a season of peace on BF and goodwill to fellow members. We can get back to our normal snide attitudes in January.

Jeff Wills

Aww, gee... do we have to?