spoke length question

[Kamil]

Hi there

I'm getting some parts and going to try to make those into something resembling a wheel
I wanted to ask about the spoke length as I'm sure I screwed something up in the calculations; see the screenshots

Specs:
Rims: Knight Composites 35 clinchers, front 20h, rear 24h
Hubs: Tune - measurements below

Mag 170 rear hub
Dimensions with axle type 130mm
Flange distance left: 35,5mm
Flange distance right: 17mm
Pitch circle left: 40,9mm
Pitch circle right: 55,5mm
Diameter spoke holes: 2,4mm

Mig 70 front hub
Dimensions with axle type 100mm
Flange distance left: 35mm
Flange distance right: 35mm
Pitch circle left: 37,5mm
Pitch circle right: 37,5mm
Diameter spoke holes: 2,4mm

Will probably go for Sapim CX Ray

I'd appreciate any help, thanks!

[alcatraz]

Spoke diameter is 2.0 at the elbows.

Are the holes really 2.4mm? Sounds small.

Is this the spokecalculator.net calculator?

Did you measure ERD yourself? Does it include nipples? What kind of nipples?

I use spokecalculator.net and I measure ERD myself with the nipples. When I use spokes such as cx-ray or equivalent I need to reduce the high tensioned DS spokes with 3mm and the lower tensioned front wheel spokes and rear NDS spokes with 2mm to get them just right.

It's possible that you don't need to do the same if you use the rim manufacturers ERD. It's very possible a result of the measuring technique. But also the rim compresses a bit, and the spokes stretch a little so you might want to reduce a bit (if you use the same calculator).

[pdlpsher1]

I took up Alcatraz's advice on reducing the length (1-2mm) to account for spoke stretch and it worked beautifully. I'm using a lighweight spoke (Pillar Wing 20) so the advice is very sound when using lightweight spokes. I also measure ERD myself including the nipple head height. Also when measuring ERD yourself check several holes and take an average, in case not every hole has the same ERD.

[Kamil]

Thanks for the answers guys, the plans have changed a bit and I'm getting 2 pairs of wheels instead of one.
The clinchers are sorted, I opted for dt swiss 240s and did the calculation on dt swiss website.

The second pair are Knight composites 35 tubulars, ERD is 574 per manufacturer's website.
I got a pair of straight pull Carbon Ti x-hubs and got the numbers from their user manual;
https://www.carbon-ti.com/products/hubs ... sp-rear-24
https://www.carbon-ti.com/products/hubs ... p-front-20

I'm quite unsure about straight pull lengths, would anyone be able to have a look and let me know if the numbers seem right?
They say spoke offset is 2mm, I assume that's on both sides, isn't it?

also sapim cx ray spokes, they sell them in 2mm length intervals, would that be;
Front: 274mm
Rear: 286 & 282?

[alcatraz]

Straightpull and generic calculators can be bit of a gamble. How about throwing carbon-ti an email and ask them for a little calculating advice about the numbers that are unique to straightpull like offsets and such. Maybe they can offer you a print screen of an example geometry input with their calculator of choice.

I hear carbonti support is quite good.

Once again ensure those ERD numbers comply with the requirements of the calculators. Some include nipples, some don't. The calculator needs to take your nipple dimensions into account. There are many kinds of non-standard nipples. Sometimes those dimensions are in the ERD value, sometimes not. There is a standard ERD but for the sake of avoiding issues further down, better check.

I can't say for sure that the spoke length reduction that I apply is a result of my measurements or if it's a result of the calculator. I only know that thinner/tighter spokes and shallower rims need a greater reduction. So I'm afraid I can't say for sure what value to use for a perfect result.

It can be worth comparing results from two calculators.

The dtswiss calculator can be used with custom hubs I believe. (if memory serves)

One tip is to use semi-internal nipples like Pillar DSN or Squorx because they're a little bit less sensitive to spoke lengths that come out lets say 2-3mm too short. They provide no advantage for too long spokes though. This style nipple needs to be accounted for in the calculations.

[Kamil]

Good point, I'll drop Carbon Ti and email, thanks.

[Kamil]

Interestingly Carbon Ti gave me those measurements:
Front wheel: left (radial) 274 mm, right (radial) 274 mm
Rear wheel: left (radial) 274 mm, right (2X crossed) 282 mm

Hope these will be ok.