cyclesick

hi all, i'm trying to find the e.r.d of a couple of sets of older rims. normally i would just measure them,but they're still in use and i don't want to break them down pre-maturely just to measure them. when i'm ready, i will re-build the wheels. but, currently they're still in heavy use. if any one can point me to some sort of "master list" i would greatly appreciate it. thanks

cavernmech

Maybe if you told us what make and model we could help.

JiveTurkey

For a master list, see: https://sheldonbrown.com/tire-sizing.html

Since the wheels are currently in use, I assume they still have tires on them, which should help you find the ISO BSD (bead seat diameter) in the list.

cyclesick

Cavernmech, Sorry about the lack of info. I really thought I listed it. Anyway, here goes: the first set are "Matrix Titan Tour's", 700c, double walled, single eyelets,off a Trek 520. I'm not sure of the year but I'm guessing early 1990's because the bike originally had "bio-pace" cranks. The second set are "Araya 700c WO VX-300's",no eyelet's, single walled off a Fuji Touring Series. I checked Damon Rinard's "spocal" list but they're not listed. Other than maybe e-mailing him personaly, that's about the extent of my resources. Any help you can offer would be great. thanks

madman451

You can get a good estimate by taking off the tire, measuring the circumference around the inside of the rim where the spoke nipples sit and dividing that answer by 3.1415. Use a string or soft tape measure to do the measuring. Multiple inches by 25.4 to get millimeters.

mtnbiker4791

Erd on the matrix rims is 607mm and the arayas are 614mm

cyclesick

Mtnbiker, thanks for the info. Can you tell me where you found it? I'd like to have a source for future reference. If it's C.I.A. stuff, 'ya know, like "need to Know only", that's fine. I can be satisfied with what I've got. But it would be nice to be able to access some sort of "list" now and again. Thanks again.

mtnbiker4791

Gor the numbers off bike alogs sutherlands spoke calc.

cyclesick

Mtnbiker, thanks

cyclesick

mtnbiker, i just downloaded the most recent version of daman rinard's spocal exel page. both of the rims are now listed and the matrix titan tour rims are listed as having a 614mm erd. the same as the araya's. i don't mean to offend you or question your knowledge and experience, but could you double check your source. i just don't want to make any mistakes and this new info seems to add a level of confusion. thanks

JiveTurkey

Can you define what you mean by "effective rim diameter"? Are you talking about the overall outer diameter from edge to edge or just where the tire bead seats (which is the bead seat diameter-BSD).

It's the BSD that determines tire size. The outer diameter may vary slightly from model to model for the same BSD.

Maybe you're talking about the inner diameter or radius of the rims (this--or some derivation of it--is important for spoke length, but not much else)?

cyclesick

jive turkey, yes, the E.R.D. is the inner demension. the diameter of the spoke nipple bed. see Sheldon Brown's instruction sheet on wheel building.

JiveTurkey

Thanks, I should have looked at Sheldon's glossary first; just never seen that term in all the time I've poured through that site. Then again, I'm no wheel builder.

mtnbiker4791

The profiles of the rims should be different shapes. The araya looks to be a shallow rim compared to the Matrix which seems to be a deeper rim. with a tape measure to make sure, measure from the bottom of the rim (nipple side) to the front axle on both a see if they differ. the matrix should be a smaller measurment. As far as the Program I have its been right almost all the time if its been off its ussually by a mm or 2 only. There is a titan t which is a single wall rim which rinard is calling a titan t (touring), but there is also a titan touring that is double wall that rinard doesnt have on his sheets.

Scooper

If you have the rims, measure the ERD yourself.

From Wheelbuilding, 4th ed. by Roger Musson:

cyclesick

mtnbiker, that's exactly the explanation i was hoping for. i could see that they appeared to be different, but i had'nt gotten around to measuring them. 2 different rims with confusingly similar names sounds exactly like the kind of thing trek was doing in 1990. thanks again for the clarification.

cyclesick

scooper, thanks for the info, but i already know how to measure a rim that's not built. the problem is, these wheels are still in use. they're on nos bikes that are in perfect condition except for the rims have some deep pitting. since neither rim is available, i'm trying to find rims with e.r.d's as close to original as possible. in order to do that i need to know the e.r.d of the stock rims. but i did'nt want to ground these rides in the process. but, thanks for your willingness to help.

gonogo

I measure the out side diameter of rim. I put a nipple in one hole. I measure from the slot to the top of rim X 2, then subtract from the total diameter.