DT Swiss Spoke Calculator WRONG?

[Formulasaab]

Has anyone else had a problem with the DT Swiss spoke calculator?

I was calculating the spoke lengths for a set of wheels I'm building (H+Son Archetypes to White Industries T11, 28 hole, 2X) and it is just wrong on the drive-side spokes on the rear. Every other calculator I've tried agrees it is wrong.

I quintuple checked it using the spocalc spreadsheet, Sapim calculator, Pro Wheelbuilder, wheelpro.uk, and leonard.io/edd.

In addition to being wrong, DT Swiss gave me two different numbers, with the same inputs, on different days.

The other calculators tell me ~286/280 L/R.
DT Swiss insists on 285.9/284.1 (day 1) and 285.6/283.8 (day 2) L/R.

I've actually noticed this before, but thought it was a fluke of the day. Months later and it still happens?

[unterhausen]

I think my lbs has stopped using it

[oldpotatoe]

Has anyone else had a problem with the DT Swiss spoke calculator?

I was calculating the spoke lengths for a set of wheels I'm building (H+Son Archetypes to White Industries T11, 28 hole, 2X) and it is just wrong on the drive-side spokes on the rear. Every other calculator I've tried agrees it is wrong.

I quintuple checked it using the spocalc spreadsheet, Sapim calculator, Pro Wheelbuilder, wheelpro.uk, and leonard.io/edd.

In addition to being wrong, DT Swiss gave me two different numbers, with the same inputs, on different days.

The other calculators tell me ~286/280 L/R.
DT Swiss insists on 285.9/284.1 (day 1) and 285.6/283.8 (day 2) L/R.

I've actually noticed this before, but thought it was a fluke of the day. Months later and it still happens?

I don't use the DT spoc-calc but I do know some of their ERD measurements are wrong also. So I use UBI calculator on my desk top and a different one on my phone(don't have my phone)..but I prefer using ones where you measure the ERD/hub dimensions and put that in.

[ergott]

spocalc user since the beginning. All I've done is modernize mine to Google Sheet and added a bunch of stuff that helps me with the rest of the wheel biz. Otherwise it's the same calculator.

[Formulasaab]

The DT Swiss calculator has stored info for DT Swiss rims and hubs, but allow you to input your own measurements as "user defined" data.

Since I'm confident that I got the right calculations in the end, I wanted this thread to be a warning to others (assuming that it is consistently wrong).


Sent from my iPhone using Tapatalk

[oldpotatoe]

The DT Swiss calculator has stored info for DT Swiss rims and hubs, but allow you to input your own measurements as "user defined" data.

Since I'm confident that I got the right calculations in the end, I wanted this thread to be a warning to others (assuming that it is consistently wrong).


Sent from my iPhone using Tapatalk

I used it once for a straight pull spoke calculation using DT stuff but found it cumbersome.

[11.4]

I'm not sure the DT calculator is actually a calculator and not just a look-up database. Certainly as DT has changed rim models and hub models, they have accumulated some defects in the calculator, and I also don't trust it. Spocalc for me. I wish Damon would take another crack at it as a public service, but for now I update it with new measurements and have a series of worksheets set up and tested extensively for each of the hubs I ever run across. Then all I do is insert the rim ERD in the right worksheet and I'm good to go. That's unnecessarily cautious, but it never fails. There are a variety of other spreadsheets out there as well and I haven't had problems with them, but I also have one that works and that I've personalized to my needs so I don't really need to look anywhere else.

The math of a spoke calculator is not at all difficult. I grew up with celestial navigation and was probably one of the last kids to actually study spherical trigonometry. You also learn how to create your own sine table from scratch without a calculator and convert to cosines and tangents and their inverses and hyperbolics. Talk about a dead science today. It makes a spoke calculator very accurate and very easy. And it's great for showing off on a slow day at Interbike.

[bicycletricycle]

I have used the DT calculator for a long time, always input my own measurements. Never had a problem.

strange, that 6mm difference between sides seems a bit much, I guess the flanges are kinda hi/lo on the T11. I have not built a set of T11s yet.

I guess double checking the measures is all you can do. hard to believe it could have a glitch.

Maybe the flange hole diameter field could be mis-entered? that might explain the slight difference day to day.

[A1CKot]

Maybe the flange hole diameter field could be mis-entered? that might explain the slight difference day to day.

I did this and order spokes based on those inputs. I forgot the decimal... I only caught it because of this thread. I cross checked the DT calc with another on and found my error. Both calculators no give me the same numbers.

[bicycletricycle]

I just did your calc on DT calculator and got 286.3 and 280.6

used 595 erd

55/40.5 flange size
35/18 flange distance
28 hole
2x

[Hermes_Alex]

Echoing a recommendation for Spocalc - It's been a long time since I used DT Spoke Calculator (2009ish), but it did lead me astray a couple times. No such trouble with Spocalc :).

[ryker]

The DT calculator is a direct implementation of the formulas in the Brandt book. I know this because I also implemented the formulas from the book and my calculator agrees with DT to the tenth of a mm. That said I wouldn't trust the rim ERD database they offer because of variation in mfg. Always measure.

[11.4]

The DT calculator is a direct implementation of the formulas in the Brandt book. I know this because I also implemented the formulas from the book and my calculator agrees with DT to the tenth of a mm. That said I wouldn't trust the rim ERD database they offer because of variation in mfg. Always measure.

This doesn't explain why calculated spoke lengths for a given ERD differ, sometimes meaningfully, between DT and Spocalc or others. And the DT is the one that's usually off. Any ideas?

[bicycletricycle]

Well, I think some manufacturers measure spoke lengths slightly differently. Also some calculators don't ask spoke hole diameter so that value can also be different. Also the value for the nipple could be slightly different.

[bikinchris]

I just did your calc on DT calculator and got 286.3 and 280.6

used 595 erd

55/40.5 flange size
35/18 flange distance
28 hole
2x

Gotta love the internet. It gives anyone with a beef a soapbox. I have used many different spoke calculators and none have given me any problem. Including the DT calculator.

[oldpotatoe]

i just did your calc on dt calculator and got 286.3 and 280.6

used 595 erd

55/40.5 flange size
35/18 flange distance
28 hole
2x

ubi-282.1, 284.6

[Formulasaab]

Gotta love the internet. It gives anyone with a beef a soapbox. I have used many different spoke calculators and none have given me any problem. Including the DT calculator.

Chris,
Did I say I had a beef? No. I had a question. An honest one.

[Formulasaab]

I just did your calc on DT calculator and got 286.3 and 280.6

used 595 erd

55/40.5 flange size
35/18 flange distance
28 hole
2x

THANKS. You helped me find my mistake. :hello:
I was mis-reading their diagram of how to measure the flange distance (different calculators use different measurements, so I had a lot going on in my head at the time).

This is the DT Swiss way (most common).

https://spokes-calculator.dtswiss.com/assets/images/infoboxes/EN/classic/flangedistance_right_rear.png

I totally mis-read it, and was entering the measurement as if I was using the Sapim calculator (which asks for the distance from the axle locknut, not the hub center).

This is Sapim's way (uncommon) of doing it.
http://img11.hostingpics.net/pics/893105Spokecalculcoteutiliseesapi.jpg

Sapim also calculates ERD using rim thickness and ID instead of simply inputting the standard ERD (much easier to measure), but that is immaterial, if weird.

So, my bad. Seems OK now and after changing my inputs I got the same output as BicycleTricycle.

[bicycletricycle]

Ya, I screwed that up the first time I used it as well.