MrCharlie
11-26-12, 10:08 AM
Does anyone know how far the spoke bed is offset on the DT rr440? I've scoured the web and the forum, even emailed DT, but they were little help.
Bicycle Mechanics - DT Swiss rr440 asymmetric OSB
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FBinNY
11-26-12, 10:22 AM
I don't have an exact answer, but given the shape of the rim, it has to be in the 1-2mm range (from center, 2-4mm TIR). That should be enough for your needs, since center-to-flange distance, and rim offset differences, affect spoke length by about 1/10th, ie. 0.1mm spoke length change for each 1mm of CTF change.
MrCharlie
11-26-12, 01:39 PM
I don't have an exact answer, but given the shape of the rim, it has to be in the 1-2mm range (from center, 2-4mm TIR). That should be enough for your needs, since center-to-flange distance, and rim offset differences, affect spoke length by about 1/10th, ie. 0.1mm spoke length change for each 1mm of CTF change.
I know that velocity lists the aerohead oc offset as 4mm. Is this just more offset than the rr 440, or are they using this TIR measurement? Follow up question...what is TIR? I' dealing with the new WI T11 hub, which seems to have horrible flange spacing, so I am trying to get as much offset as possible (albeit without loosing eyelets if possible, hence the DT as opposed to the velocity.)
I know that velocity lists the aerohead oc offset as 4mm. Is this just more offset than the rr 440, or are they using this TIR measurement? Follow up question...what is TIR? I' dealing with the new WI T11 hub, which seems to have horrible flange spacing, so I am trying to get as much offset as possible (albeit without loosing eyelets if possible, hence the DT as opposed to the velocity.)
FBinNY
11-26-12, 04:42 PM
TIR stands for "total indicator readout". When things are on either side of a center line, you can express the difference as the distance to center, or the the total distance from one side to the other - TIR. It's analogous to the difference between a radius and diameter.
TIR is typically used, for example, when talking about a wheel out of true, or when something is turning off center. I mentioned it with reference to offset spoke holes to clarify the answer so we'd both be speaking about the same measurement.
TIR is typically used, for example, when talking about a wheel out of true, or when something is turning off center. I mentioned it with reference to offset spoke holes to clarify the answer so we'd both be speaking about the same measurement.
mrrabbit
11-26-12, 07:14 PM
Tried to figure out the OSB the backdoor way using DTSwiss spoke length calculator. When selecting both version of the RR 440 - not adjustments are made.
Just another "?" mark on their tool...
*sigh*
Anyhow most road version of OCR rims tend to have an offset of 3-6mm. +/- 4mm to/from the hub offsets should get it pretty close.
=8-)
Just another "?" mark on their tool...
*sigh*
Anyhow most road version of OCR rims tend to have an offset of 3-6mm. +/- 4mm to/from the hub offsets should get it pretty close.
=8-)
Firetngguy
11-26-12, 09:06 PM
Mr Charlie,
I recently ordered this rim and struggled to calculate correct spoke length using the 240s hub. I sent an email to DT tech support, here's their answer:
Hello Curtis,
Sorry, but the head office has not yet updated the spoke calculator with the RR440 rim. But you can do it manually like I did bellow, showing a 32 hole with 3X lacing.
The calc shows left/right 292/291mm for a 599 ERD rim (440), but then we need to consider the asymmetric design. To do that, just subtract 1mm from the left, and add 1mm to the right and you will have 291/292mm (it happens to reverse the original non asymmetrical lengths).
I recently ordered this rim and struggled to calculate correct spoke length using the 240s hub. I sent an email to DT tech support, here's their answer:
Hello Curtis,
Sorry, but the head office has not yet updated the spoke calculator with the RR440 rim. But you can do it manually like I did bellow, showing a 32 hole with 3X lacing.
The calc shows left/right 292/291mm for a 599 ERD rim (440), but then we need to consider the asymmetric design. To do that, just subtract 1mm from the left, and add 1mm to the right and you will have 291/292mm (it happens to reverse the original non asymmetrical lengths).
mrrabbit
11-26-12, 09:50 PM
Reverse calculation using the numbers DT Swiss gave you says the OSB = +/- 10.00mm.
To be honest I find that hard to beleive, unless it's a Felt 24 x 4.00 or 26 x 4.00 cruiser rim or a Vicious Cycles "Graceful Fat Sheba 26 x 3.25".
All you really have to do to be honest is measure the outer width of the rim - to determine the center - and then measure how far the center of the holes are from that.
=8-)
To be honest I find that hard to beleive, unless it's a Felt 24 x 4.00 or 26 x 4.00 cruiser rim or a Vicious Cycles "Graceful Fat Sheba 26 x 3.25".
All you really have to do to be honest is measure the outer width of the rim - to determine the center - and then measure how far the center of the holes are from that.
=8-)
FBinNY
11-26-12, 10:06 PM
I can't believe the concern given to this. Look at the rim, and it's obvious that the offset is in the 2-4mm range (TIR). So the total impact on spoke length will be .1-.2mm which is one full order smaller than the amount you're rounding anyway. In short it doesn't matter.
If, however, you're someone who insists on meaningless precision you can measure the offset by measuring the distance of any hole to both sides of the rim. The difference is the TIR difference, so offset is half that.
If, however, you're someone who insists on meaningless precision you can measure the offset by measuring the distance of any hole to both sides of the rim. The difference is the TIR difference, so offset is half that.
davidad
11-27-12, 10:10 AM
I looked at DT's site and the offset must be a corporate secret! :rolleyes:
FBinNY
11-27-12, 10:34 AM
I looked at DT's site and the offset must be a corporate secret! :rolleyes:
I agree that it's strange that a company marketing an offset design as a sales feature wouldn't list the amount of offset as a spec.
My earlier posts on the subject were based on the symmetrical rim since that's the one I found when searching the rr440, and I thought the OP wanted to know the zigzag offset.
.
But the thrust of my posts remain unchanged. While an offset rim will help reduce the R/L tension imbalance, there's never enough offset to affect spoke length enough to factor in a spoke length calculation. If the OP is concerned, he can adjust the CTF measurements by ±5mm respectively and doing a test calculation. That may not be the exact offset, but is plenty close enough for spoke length calculations.
I agree that it's strange that a company marketing an offset design as a sales feature wouldn't list the amount of offset as a spec.
My earlier posts on the subject were based on the symmetrical rim since that's the one I found when searching the rr440, and I thought the OP wanted to know the zigzag offset.
.
But the thrust of my posts remain unchanged. While an offset rim will help reduce the R/L tension imbalance, there's never enough offset to affect spoke length enough to factor in a spoke length calculation. If the OP is concerned, he can adjust the CTF measurements by ±5mm respectively and doing a test calculation. That may not be the exact offset, but is plenty close enough for spoke length calculations.
mrrabbit
11-27-12, 01:48 PM
I agree that it's strange that a company marketing an offset design as a sales feature wouldn't list the amount of offset as a spec.
My earlier posts on the subject were based on the symmetrical rim since that's the one I found when searching the rr440, and I thought the OP wanted to know the zigzag offset.
.
But the thrust of my posts remain unchanged. While an offset rim will help reduce the R/L tension imbalance, there's never enough offset to affect spoke length enough to factor in a spoke length calculation. If the OP is concerned, he can adjust the CTF measurements by ±5mm respectively and doing a test calculation. That may not be the exact offset, but is plenty close enough for spoke length calculations.
I agree for the most part...
What really gest me about his thread now though is the reply supposedly from DT Swiss. Most narrow OSB road rims will be +/- 2-4mm against hub offsets resulting in about .50mm in spoke length change....yet the DT Swiss reply when reverse calculated suggests an offset of 10.00-11.00 millimeters putting leaving the nipples embedded in the CNC work of the sidewall. (It's 21mm wide rim...)
Makes me wonder if the DT Swiss rep was just giving the respondee a quick off the head remark just to get them out of their hair...
=8-)
My earlier posts on the subject were based on the symmetrical rim since that's the one I found when searching the rr440, and I thought the OP wanted to know the zigzag offset.
.
But the thrust of my posts remain unchanged. While an offset rim will help reduce the R/L tension imbalance, there's never enough offset to affect spoke length enough to factor in a spoke length calculation. If the OP is concerned, he can adjust the CTF measurements by ±5mm respectively and doing a test calculation. That may not be the exact offset, but is plenty close enough for spoke length calculations.
I agree for the most part...
What really gest me about his thread now though is the reply supposedly from DT Swiss. Most narrow OSB road rims will be +/- 2-4mm against hub offsets resulting in about .50mm in spoke length change....yet the DT Swiss reply when reverse calculated suggests an offset of 10.00-11.00 millimeters putting leaving the nipples embedded in the CNC work of the sidewall. (It's 21mm wide rim...)
Makes me wonder if the DT Swiss rep was just giving the respondee a quick off the head remark just to get them out of their hair...
=8-)
FBinNY
11-27-12, 02:34 PM
... Most narrow OSB road rims will be +/- 2-4mm against hub offsets resulting in about .50mm in spoke length change....yet the DT Swiss reply when reverse calculated suggests an offset of 10.00-11.00 millimeters putting leaving the nipples embedded in the CNC work of the sidewall. (It's 21mm wide rim...)
Makes me wonder if the DT Swiss rep was just giving the respondee a quick off the head remark just to get them out of their hair...=8-)
It might not be that but rather an example of the dangers of reverse calculations based on rounded numbers. As you point out, the actual difference might result on a change of .5mm in spoke length. Assuming that's right, the DT rep might have correctly rounded it to 1mm. Then when reverse calculating you ended up with double the offset.
=8-)[/QUOTE]
Makes me wonder if the DT Swiss rep was just giving the respondee a quick off the head remark just to get them out of their hair...=8-)
It might not be that but rather an example of the dangers of reverse calculations based on rounded numbers. As you point out, the actual difference might result on a change of .5mm in spoke length. Assuming that's right, the DT rep might have correctly rounded it to 1mm. Then when reverse calculating you ended up with double the offset.
=8-)[/QUOTE]
mrrabbit
11-27-12, 05:26 PM
It might not be that but rather an example of the dangers of reverse calculations based on rounded numbers. As you point out, the actual difference might result on a change of .5mm in spoke length. Assuming that's right, the DT rep might have correctly rounded it to 1mm. Then when reverse calculating you ended up with double the offset.
=8-)[/QUOTE]
Absolutely - as DT Swiss spoke length calculator itself outputs actuall result and rounded result. However the rep in this case really went to the extreme. Assuming you're actually bored and have nothing better to do, go play with a manual DOS level calculator and massage the offset data for the 240s 8/9/10/11 rear until you cross the threshold of an actual change of .50mm that justifies rounding other way...I think you'll see it takes quite a bit - way more than the usual 3-4mm.
(Funny thing is, I just did the manual offset change of +/-3mm in the DTSwiss calculator and the rounded result? 292/291 - no change - just as you stated from the very beginning. ROFL!!!)
=8-)
=8-)[/QUOTE]
Absolutely - as DT Swiss spoke length calculator itself outputs actuall result and rounded result. However the rep in this case really went to the extreme. Assuming you're actually bored and have nothing better to do, go play with a manual DOS level calculator and massage the offset data for the 240s 8/9/10/11 rear until you cross the threshold of an actual change of .50mm that justifies rounding other way...I think you'll see it takes quite a bit - way more than the usual 3-4mm.
(Funny thing is, I just did the manual offset change of +/-3mm in the DTSwiss calculator and the rounded result? 292/291 - no change - just as you stated from the very beginning. ROFL!!!)
=8-)