Spoke length compromise - 1mm too long or too short?

buckles

Spoke calculator shows drive side 289.0 and non drive side 290.7 for the rear wheel I'm building (Shimano 105 5700 on a H+Son Archetype) so I would have bought 289mm for DS and 291mm for NDS spokes.

The shop has no 289mm spokes in stock but ideally I'd like to keep 1-2mm difference in spoke length to make dishing easier.

I can think of a few downsides to using spokes that are slightly too short (tension too early), but I'm not sure of any downsides of having spokes slightly too long.

Does it matter whether I get:
290 and 291 (1mm difference, DS 1mm too long) , or
288 and 290 (2mm difference, both sides 1mm too short), or
292 and 290 (2mm difference, both sides 1mm too long)?

jimmybloom

I'd go too short. The nipple will make up the extra length.

ugo.santalucia

I use 288/290 rear for that combination of rims + hubs and 290 front... often use 14 mm nipples too with DT spokes

buckles

You talking 32 spokes, 3 cross for both? The spoke calc I used reckons 291.6 (I round up to 292) for the front...

cycleclinic

Use an ERD of 594 for the archetype with a 3mm off set (Spoc calc seems to suggest there is one and everytime I build a front wheel using any archetype it require's 1/4 turn of the spoc key to correct the dish consistent with a small offset) . The front lengths are best kept to 290mm both sides, that what I do. For the rear I would use 288DS and 289 NDS.
290mm NDS is slightly to long but as the NDS spokes are under less tension you are unlikely to run out of spoke thread. Keeping the spoke length difference to 1mm on the rear reduces the amount of dishing that you need to do.

If you use Sapim spokes like Sapim Race for example then you can have 1mm increments, I stock them for that reason.

ugo.santalucia

Buckles wrote:

You talking 32 spokes, 3 cross for both? The spoke calc I used reckons 291.6 (I round up to 292) for the front...

Of course...

cycleclinic

In general do not round up as spoke will stretch under load and even more during stress relieving. You know if you are stress relieving properly as there will be a measurable tension drop afterwards. You can only round up if your ERD measurements are too short to begin with. An ERD 595mm for a Archetype means rounding down and taking 1mm of spoke lengths. Use 594mm and you only have to round down.

buckles

The last time I rounded down, my spokes became tensioned very early (half way around the wheel while tightening each nipple until the spoke thread disappeared) which meant backing off each spoke a turn. I have made a nipple driver now so maybe won't be a problem this time.