richas

Hi,
In another thread I talk about replacing a damaged hub on my rear rim brake Zipp 404 wheel. I am having a hard time finding a suitable 20h hub. I have found a Taiwanese hub but the flange offsets are different. Other than affecting spoke length how critical are the flange offsets to wheel performance or safety? This is on a Giant Propel that will be raced.

Thank you

Rich

Iride01 

Critical for safety? Probably not going to make the bike so unsafe that you'll come to a terrible demise.

I'd think they'd have more to do with what number of speeds you could have on the bike for any particular desired OLD.

Certainly a wheel builder will be along soon to answer.

Bill Kapaun

Since you want to keep the numbers a secret, run them through SpoCalc.

richas

No secrets! But I will do that when I have time. More background:

Original hub Zipp 188 V8

From a quick measure of the old hub it looks like the White Industries T11 has the same offsets. (Can't find one though)

Center to left flange 35mm Center to right flange 18mm
Then there is this:
https://www.cycletaiwan.com/circus-m...-rear-hub.html

Not a confidence inspiring name. But it is cheap, 20H, rim brake, and light. I can't seem to figure out the offsets from this drawing.

Also, I am 6'+ and 155 lbs. Not a sprinter.

Thanks all!

icemilkcoffee 

In general a rim does not care about the hub's flange offset.
The rare exceptions would be like HED, Mavic Cosmic carbon, Aeolus, or Flo wheels with soft carbon fairings, where the spoke must go through the hole in the carbon fairing at a particular angle. In that case you need to find a hub that has similar flange diameter and offset as the original.

richas

interesting! Do these count as “soft fairings”

icemilkcoffee 

No- the ZIPP wheels all use hard, structural carbon fairings. The nipples are anchored in the carbon.
In the soft fairing wheels the nipples anchor in the aluminum rim. The carbon is purely non-structural. There are holes in the carbon for the spoke to go through.

maddog34

posted to your previous thread... rosefarts
With a mighty wind

Join Date: May 2015
Posts: 2,336
Mentioned: 12 Post(s)
Tagged: 0 Thread(s)
Quoted: 937 Post(s)
Likes: 620
Liked 715 Times in 416 Posts

https://www.bikehubstore.com/RAR12-p/rar12.htm

20h in Black, competitive weight, competitive price. I’ve used a few other Bitex hubs and I’ve always been pleased with the quality.

KCT1986

Based on the drawing the hub is 48.22mm between the flanges (inside to inside) and the offset is 9.3mm (sometimes referred to as dish). Seems that the drawings uses a " , " in place of a decimal point, see this in some number listings in non-USA applications.

Based on the 48.22mm & 9.3mm figures, center to flange distance is: DS 14.81mm (48.22mm divided by 2 minus 9.3mm) and NDS 33.41mm (48.22mm / 2 +9.3mm), inside of flange to center point between the OLD.

Adding half of the flange thickness (3mm / 2), we get: DS 16.31mm and NDS 34.91mm, center of flange to center point between the OLD. This should result in a relative tension of 46.72 NDS to DS (16.31mm/34.91mm).

For comparison to Shimano's method of measuring, (outside of flange to outside of flange), we add full flange thickness of 3mm to each side: DS 17.81mm & NDS 36.41mm. This should result in a relative tension of 48.92 NDS to DS. Shimano 11 speed road hubs are about the same with regards to relative tension. Shimano's hubs are slightly wider between the flanges, (about 3mm), so the bracing angle is slightly better.

Don't know how the measurement of the various other hubs mentioned were taken (inside/inside, center/center, outside/outside).

Not sure about where the NDS/DS relative tension reaches a point where it becomes a problem with regards to wheel strength or stability. Believe that 'hoop strength' and maximum tension that the components can withstand would play a part.

richas

Thank you, that makes sense. The original Giant wheels were as you describe, composite fairings but the spokes seated in the aluminum rim.

Rich

richas

Ordered! I am still looking for other options like the T11 but at least this is on the way.

Thank you

richas

Thank you for working through this. It seems like they didn't make much effort in making that drawing clear. I don't understand relative tension, that is new to me. I have ordered a hub with the same offsets as the original to avoid deviating from the original.

Thanks

Rich

KCT1986

The relative tension (also known as tension ratio) is an estimate of the left side tension in relation to the right side.
For example, if the hub has flange spacing that gives a relative tension of 50%, the left side will have half the tension of the right side. So, if the wheel is tensioned to 120 Kgf on the right side, the left will be about 60 Kgf,

richas

That makes sense, thank you for the explanation.

Rich

richas

I have ordered the hub mentioned above. It has 2.3mm spoke holes, can I use 2mm diameter spokes with that hole diameter? The current plan is to buy CX-RAY spokes and reuse the existing nipples. The original spokes are 2mm diameter.

Also I am using SpokeCalc, it asks for "width between holes" and "offset spoke bed" for rim parameters. I am assuming these are both zero for these Zipp wheels, is that correct?

Rich

KCT1986

This rim seems to have spoke holes in the center and possible just aligned for L/R spoke path. So no adjustment needed for spoke hole.

Andrew R Stewart 

Yes, 2.0mm spokes fit into 2.3mm holes nicely. I would not reuse the nipples myself, and I would get brass ones too. Andy

grumpus

Offset simply dictates the wheel's dish - a single speed wheel has equal dishing, all spokes have the same tension, but when we add multiple sprockets the drive side flange gets moved inboard; that means the drive side spokes need higher tension than the non drive side to balance the structure laterally, as the rim isn't equidistant between the flanges. As the tension in the non drive side is determined by the tension in the drive side a wheel with more dish has to be built with slacker NDS spokes. Spokes are subject to cyclic stress as the wheel rotates with vertical load, wind-up from transmission and hub brakes, and lateral lean - if the stress cycles too deeply, so the spokes become unloaded, then they will suffer early fatigue failure. On the other hand if you tighten the drive side just a little too much to allow increased NDS tension you risk exceeding the limit for pulling a spoke through the rim, or the wheel's ability to stay radially flat so a pothole or crash can cause it to try to collapse in on itself.

.

richas

Thanks Andy, I will get new nipples.

Rich

richas

I was wrong, the flange holes are 2.6mm in diameter. Still ok for 2mm spokes?

I disassembled the wheel (Older Zipp Speed Weaponry 404) and there are no spoke washers. Is it normal to not use them on these older Zipps?

Andrew R Stewart 

Spoke washers, for the elbow/flange fit, are about elbow length WRT flange thickness far more than hole diameter. One wants the spoke "body" (the main shaft) to be snug against the flange if at all possible. Spoke washers are placed between the spoke head and the flange as needed. 2.6mm holes will work fine with 2mm spokes assuming the elbow length and flange thickness are also good.

Or are you asking about nipple/rim washers? These are rim driven, not hub dependent. Andy

richas

All back together and ready to Rip!

Thanks all for the help.

If I wanted to make a living as a wheel builder I would have to charge by the hour.

Rich