Bicycle Mechanics - Switching rims

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trek330
09-27-10, 08:25 PM
Can I switch a double walled 622-15 rim with a 622-17 single walled rim without changing spokes?The spokes are new.Do I need different nipples?The 622-17 is the presently installed rim and the 622-15 would be an upgrade.Thanks!


HillRider
09-27-10, 08:33 PM
It's unlikely the spoke would be the correct length.

Al1943
09-27-10, 08:36 PM
You need to compare the ERD of the two rims. This information is available at various sites for many rims.


BikeWise1
09-27-10, 08:45 PM
+1. The fact this question is being asked is indicative of someone who probably isn't aware of the relationship between things like ERD (http://lmgtfy.com/?q=effective+rim+diameter) and spoke length.

If that's the case, the OP probably shouldn't be building own wheels just yet. But that's just the opinion of someone who builds lots of wheels.......for a living.......

OP, this question cannot be answered without more information.

trek330
09-28-10, 01:07 AM
It's unlikely the spoke would be the correct length.

I'm going to assume this is the definitive answer.I thought perhaps the "622"would be the workable measure and therefore doable.I just purchased a truing wheel and tensionmeter and am determined to learn truing and eventually wheel building since I'm so dissatisfied with NYC mechanics.Of course I plan on practicing on some old wheels before I doit seriously on a working bike.

dabac
09-28-10, 01:36 AM
Can I switch a double walled 622-15 rim with a 622-17 single walled rim without changing spokes?

Unlikely. 622 refers to the bead seat diameter, basically where the tire meets the rim. There's no fixed relation between the BSD and the requires spoke length. 15/17 refers to rim internal width, which has a so-so relationship to which width of tires you can run on a certain rim.

The value you want to be looking for is (quote from Sheldon Brown) Effective Rim Diameter. This is the rim diameter measured at the nipple seats in the spoke holes, plus the thickness of the two nipple heads. The E.R.D. is needed for calculating the correct spoke length.

A rim with a higher profile will have a lower ERD despite being the same BSD.

Do note that all suppliers measure ERD in the same way, and don't take for granted that values listed on websites are correct.

Sometimes picking another lace pattern can offer possibilities. Going from 3-cross double wall to 2-cross single wall might free up enough spoke length for a successful transplant. Or 3X single-wall to 4X double wall might use up enough spoke for the wheel to tension up properly.

Different nipple lengths can, IME, be used for minor tweaks of spoke lengths. However, not all would agree, and for a first build you want things to line up nicely w/o any extra challenges.

Bezalel
09-28-10, 01:46 AM
I'm with HillRider. Since one of the rims is single walled and the other is double walled, it is extremely unlikely that they have the same ERD.

peripatetic
09-28-10, 09:44 AM
http://www.sheldonbrown.com/wheelbuild.html#length

http://www.wheelpro.co.uk/spokecalc/

Retro Grouch
09-28-10, 04:11 PM
Of course I plan on practicing on some old wheels before I doit seriously on a working bike.

I hear that a lot but I think that it's a bad plan.

You can practice the actual laceing function using an old wheel but I could train a chimpanzee to do that part.

The real wheelbuilding process starts after the wheel has been laced. Getting all of the spokes to equal and even tension is what we're after. If you are practicing with an old wheel, the rim is likely to be egg shaped and out-of-true. I don't think that you can teach yourself to tension and true a wheel properly using a crappy rim. Since you've already spent money on tools, have the confidence to start with decent quality hub, rim and spokes. If you take your time and sweat the details there is no reason why your first wheel shouldn't rival the quality of anything that you can buy.