spoke calculation help needed

[Dead Rats]

I am attempting to build up a rear wheel with the following (I have very little experience of wheel building BTW):

Dura-Ace FH7700 freehub

Gipiemme Parade rim

both are 16 hole!

no wheel builder or spoke supplier I have spoken to has this rim on their spoke calculator database, not even a guy with the proper DT Swiss calculator. All I know is that previously, when fitted with the original Gipiemme own brand hub, the wheel used 279mm spokes (I still have 14 of these left), and that the holes directly opposite each other on each side of the each flange are 5mm nearer on the Dura hub than the Gipiemme... basic logic tells me therefore to use a 2.5mm shorter spoke... although this gives me a size that DT don't offer in an Aero spokes (I forgot to say the spokes ideally need to be aero to match my front wheel)

for the time being I have bought a 6 pack of the 288mm DT Swiss Aero spokes to experiment with... but any advice would be greatly appreciated!

 

[Simplex]

16 spokes :shock: I'd give that to a professional if it was me.

Having said that , you need to know the Effective Rim Diameter so you can plug it into the equation ( or calculators on the web ). You can do this with two cut spokes , put the nipples on , poke them through opposite sides and measure the gap. Add this to the spoke lengths and wallah ! you have the ERD.

I made one of these for pennies so I can read it direct off the ruler ( the red heat shrink is so I don't chuck it away ).

 

[PIGEON]

I have built only one wheel so far (with the help of some friendly retrobike forumers) so I wouldn't call myself an expert but it's important to measure the ERD in a couple of places because the unlaced rim probably isn't perfectly round. So measure in 4 sets of opposite spoke holes and average to get a workable ERD.

 

[Dead Rats]

Thanks for all the advice - really appreciated! I will let you know how I get on

Incidentally, I've managed to very carefully re-space the Dura-Ace hub down to (just over) 126mm OLN (from 130mm) due to the fact that the bike's frame (a Vitus 787 with 126mm rear end) is fat enough to previously give the axle 2mm spare in each drop-out... so no worrying 4mm spreading of the bonded frame! now all I have to worry about is dishing, tension

 

[FluffyChicken]

Use this site, been very good and once you have the ERD you can submit it to add to the database.
http://lenni.info/edd/
based on Spocalc (the excel one on sheldon browns site)
Has the hub on there but not the rim though.


Though you just need to measure the ERD as above or on the sites help.



By the way, this
http://www.bikeradar.com/gear/category/ ... lset-21360
seems to say your rear is 20 spokes and only the front 16 ?

 

[Dead Rats]

Use this site, been very good and once you have the ERD you can submit it to add to the database.
http://lenni.info/edd/
based on Spocalc (the excel one on sheldon browns site)
Has the hub on there but not the rim though.


Though you just need to measure the ERD as above or on the sites help.



By the way, this
http://www.bikeradar.com/gear/category/ ... lset-21360
seems to say your rear is 20 spokes and only the front 16 ?

thanks for all the info, I'm still working through this (not constantly since last post but toe-dipping) the rear rim is def 16 spokes - I counted - an older model perhaps? According to the site the fact that I respaced the hub (therefore changing the values of standard Dura Ace 16 hole rear hub) only will have tiny effect on spoke calculation. I think I have an ERD or 586mm but I need to keep checking this