Explanation of fork thickness measurement?

[veryredbike]

So, I look at the measurements on fork wall thickness and I see things like 1.0/.5. 1.0 is the big end... but .5 is waaay too thin to be the small end. Is that the measurement of the tube before they draw it down to the smaller size?

What's a "thick" fork blade? What's a "thin" one?

I asked in a forum a couple weeks ago if a .9/.6 would work on a road setup for someone around 195 and got a yes without disent... but now I'm looking at these guys and since I don't have an understanding of exactly what's being measured and what's standard, I can't decide.

EB713 - 1.2/0.7, 395mm length, rake 15x45mm (touring. 45mm offset, sharper bend)
EB716B - 1.0/0.5, 370mm length, rake 15x45mm (touring. 45mm offset, sharper bend, but road weight)

Help? ;-)

[Curt Goodrich]

As fork blades are tapered the wall thickness increases. To have a constant wall thickness the blades starts out thinner on the end that will be tapered. As the blade is drawn through the mandrels to create the taper the thinner section increases in wall thickness. In theory, a blade that's dubbed .9/.6 should be .9 wall throughout the length of the finished blade. A blade that's dubbed .9 is only .9 at the non-tapered section and increases in wall thickness in the taper. That's the theory. In practice it's not always the case. The example of the Nova blades in the earlier thread is a prime example. They are billed as .9/.6 but in fact the wall thickness does increase at the tip. I don't think Nova is attempting to mislead anyone. They probably ordered them one way and received them another. I believe all tubing manufacturers struggle with this. The current Columbus blades that are marketed as .9/.6 come a little closer to .9 wall thickness throughout the entire length but even that can vary from blade to blade and production run to production run. As far as what's a thick blade vs. thin blade here's my take on that (others are free to have differing opinions)-
1.2 blades are the thickest blades that I know of and I only use then on things like tandems and real rough stuff.
.9 blades are currently the thinnest blades on the market. This wall thickness has a long history of being reliable in the road bike world.
Then there are blades in between that (1.0 & 1.1) and it's up to the builder to decide what blade is appropriate for what application. Regarding the earlier mentioned Nova blades, I've used them and like them. They're quite light and bend nicely. I've also built a lot of forks using blades from Reynolds, Columbus, Deda, True Temper, Tange and a few others. All of them have varied from the advertised spec.

[veryredbike]

GAH! This forum keeps eating my replies!
The quick version:

Thanks! That information really helps! While I know the decision is up to me based on my riding, brazing, etc, having the general facts about the blades in general makes it more of a decision and less of a guess.

If you have a moment, a quick clarification would be really useful:
It looks like you focus mainly on the measurement for the big end. When looking at the reynolds pre-raked blades I mention above (1.0/.5) vs the nova's (.9/.6) do you assume:

1) The .5 is probably just how they get it to be 1.0 straight gauge or .9, so it's overall stronger.
2) It's going to be stronger at the 1.0 end, but because it's .5 and not .6 on the small end it'll probably be a bit weaker down there.
3) No way to tell exactly what's going on without playing with it, bug ceeway with your questions.
4) ________________

I like the idea of using a little thicker than normal without going overkill, but if that .5 means it's going to be weak near the drops, that's obviously going to change my thought process.

Thanks again!
Jim

[Curt Goodrich]

1. Yes.
2. Not necessarily.
3. Yes, play with it and don't pester Peter.
4. When in doubt, err on the side of caution. Especially in these early stages. There's never a good time for a fork failure.

[veryredbike]

Awesome. Thanks!

I'm afraid I already pestered peter a little bit... but mostly to find out if it'd work with my dropouts. As it turns out, because it tapers slowly, I wouldn't be able to get the rake I need, so I'm going to go with the nova blades. I already have a couple, and that way if I mess up, I'll have backups. Still have an order for ceeway though, maybe I'll throw them a little tip for his time.

Again, I really appreciate your help. Having the background to make my decision really helps.