Building carbon wheels vs alloy... things to consider?

[hoj]

Hey all,

So I have a decent amount of experience building alloy wheels for various commuter/cx/road bikes over the years, but for whatever reason I've never actually had the need and/or opportunity to lace up a set of carbon rims.

I've got the itch to build something and want to try my hand at building up a set of carbon hoops (from btlos, lightbicycle, etc.). Is there anything I need to be aware of when building up a set of carbon rims compared to alloy rims? I would assume the general process is largely the same, but wasn't sure if carbon rims were in any way more finicky, fragile, or less forgiving to work with.

Any tips or advice for things I should consider would be greatly appreciated. Thanks!

[jc031699]

Two things I can think of-
1) carbon rims sometimes require spoke nipple washers, depending on the manufacturer
2) brass nipples in general less troublesome than alloy due to corrosion between the carbon fiber and aluminum. From what I recall, quality and type of aluminum nipple anodization matters, grease helps as an insulator. I just avoid all this and use silver or black brass nipples.

[carpediemracing]

Another thing is you can drop spoke nipples into the rim. Although I can build an eyelet rim quickly, building a non-eyelet rim (where the nipples can drop into the rim) is much slower. I use either a DT spoke nipple holder or, if building somewhere not with my wheel building bin, I'll use another spoke to hold the spoke nipple. It's a pain but it's less of a pain than trying to fish out a spoke nipples amongst the carbon whatever stuff inside the rim.

[carpediemracing]

Also, carbon rims tend to be strong enough by themselves. You're not really going to adjust roundness. It's really lateral and spoke tension. The roundness is more "centering the hub" rather than "pulling in that section of rim".

[oldpotatoe]

Originally Posted by hoj

Hey all,

So I have a decent amount of experience building alloy wheels for various commuter/cx/road bikes over the years, but for whatever reason I've never actually had the need and/or opportunity to lace up a set of carbon rims.

I've got the itch to build something and want to try my hand at building up a set of carbon hoops (from btlos, lightbicycle, etc.). Is there anything I need to be aware of when building up a set of carbon rims compared to alloy rims? I would assume the general process is largely the same, but wasn't sure if carbon rims were in any way more finicky, fragile, or less forgiving to work with.

Any tips or advice for things I should consider would be greatly appreciated. Thanks!

Rims are rims, whether they be carbon or alloy.
Couple of things
-Decent lube between nipple and rim. Some carbon rim nipple holes can get 'draggy' as the tension goes up.
-'Some' carbon rims, particularly disc brake type, may not be particularly flat and round when new. Like any wheel, even tension is key..and 'proper' tension, whatever you can find as the tension range. Tension meter is key.
-In spite of carbon reported burliness vs low weight, pick spoke type and spoke number conservatively. No such thing as a free lunch.

[robt57]

I'd add stress relieve and bend/press [if J bend] flat at the hub before you get to full tension. Early mistake I made on 1st few sets. And I have big gorilla mitts. You can go way beyond max tension stress relieving with hulk hands spokes already at full tension.

[Applesauce]

Originally Posted by hoj

I would assume the general process is largely the same, but wasn't sure if carbon rims were in any way more finicky, fragile, or less forgiving to work with.

None of the above. The best anecdote I’ve heard is that with aluminum rims you centre the rim around the hub; with carbon, you centre the hub within the rim. Carbon rims are generally stiffer in most directions, and are almost universally stronger. As others have said, lube, thread treatment, etc., is all the same.

The only thing I might caution is that with some crazy burly MTB rims, the rim is so strong and stiff that it will mask tension imbalances. For instance, I crashed my MTB early this season and pulled a spoke through the bed on a WR1 rim; I tied the spoke off to the next one and continued to ride the wheel until a new rim arrived three weeks later. This was a 28h front wheel, and I did literally nothing to accommodate the missing spoke for at least a dozen rides. This would never have been possible on any aluminum rim.

[foo_fighter]

All of the carbon rimmed wheels I've built were easier to true both radially and laterally. The rims started out truer in both directions(No welded/pinned/sleeved joint) and were stiffer than Al so changes in spoke tension had a greater and more noticeable effect.

[deluz]

Originally Posted by robt57

I'd add stress relieve and bend/press [if J bend] flat at the hub before you get to full tension. Early mistake I made on 1st few sets. And I have big gorilla mitts. You can go way beyond max tension stress relieving with hulk hands spokes already at full tension.

Did stress relieving beyond max tension damage the rims?. I routinely stress relieve by pulling pairs of spokes together and its never been a problem on alloy rims. With carbon rims being stiffer maybe the tension would go higher doing this.

[robt57]

Originally Posted by deluz

Did stress relieving beyond max tension damage the rims?. I routinely stress relieve by pulling pairs of spokes together and its never been a problem on alloy rims. With carbon rims being stiffer maybe the tension would go higher doing this.

Hard to know. But I had a few Pacenti V1 SL23 crack at the bed/spoke holes very fast. Like 200 miles. I know the V2 came out pretty fast and these had this issue.

I got stuck with a bunch, so I just change in another when a rear cracked. The 3rd one on initial build [in fairly short time] was going to be the last, but that 3rd one has been fine. I did add and change up washers deployment each rebuild. Rear wheels, drive side, front fine from start.

I am not a pro wheel builder, but SL23 builds 15 year since my first. And 30+ wheelset build to that date.

To stay a little on topic, the few carbon builds I found faster to build, mainly due to not dealing with hops because the rims were so perfectly round. 3 wheelsets and a front garage smash R&R.

My friend is using that SL23 set for a long while. I look at the rear rim every time I see the wheel.

We have 3 left and If his rear cracks I'll keep using up the stash. For $50.00 a rim originally, and how fast a rim swap is, not more than an annoying thing.

But several Disc sets with CL25 and SL25 are perfect day one to date. But I honestly avoided selling any wheels with Pacenti rims as a result. Even if only that one model really. #badTasteMouth

[deluz]

Originally Posted by robt57

Hard to know. But I had a few Pacenti V1 SL23 crack at the bed/spoke holes very fast. Like 200 miles. I know the V2 came out pretty fast and these had this issue.

I got stuck with a bunch, so I just change in another when a rear cracked. The 3rd one on initial build [in fairly short time] was going to be the last, but that 3rd one has been fine. I did add and change up washers deployment each rebuild. Rear wheels, drive side, front fine from start.

I am not a pro wheel builder, but SL23 builds 15 year since my first. And 30+ wheelset build to that date.

To stay a little on topic, the few carbon builds I found faster to build, mainly due to not dealing with hops because the rims were so perfectly round. 3 wheelsets and a front garage smash R&R.

My friend is using that SL23 set for a long while. I look at the rear rim every time I see the wheel.

We have 3 left and If his rear cracks I'll keep using up the stash. For $50.00 a rim originally, and how fast a rim swap is, not more than an annoying thing.

But several Disc sets with CL25 and SL25 are perfect day one to date. But I honestly avoided selling any wheels with Pacenti rims as a result. Even if only that one model really. #badTasteMouth

I also had SL23's that cracked. I think it was a common problem with those rims. On my last build I was considering Pacenti Forza but the SL23 experience made me go with Kinlin.

[foo_fighter]

Slightly off topic but Pacenti does have a rim "amnesty" program where you can get a discount on a wheelset or 25% off parts. It was a pretty decent way to get a set of bitex hubs.

[robt57]

Originally Posted by foo_fighter

Slightly off topic but Pacenti does have a rim "amnesty" program where you can get a discount on a wheelset or 25% off parts. It was a pretty decent way to get a set of bitex hubs.

I was already in dealer/wholesale status. But the guy that bought Pacenti [or was in charge for the conglomerate that did] offered me heavy discounts for a period. But I got more busy doing non wheel building stuff.

And I guess I held a grudge in truth. But every other mostly disc rim wheelset I built with CL and SL25s are stellar. But I see the decal and it reminds me of something I shoulda moved on from a long while ago. But here I sit tying about it.

There is a Sicilian joke in there someplace..


I'd add that the machining on the SL23 Brake surface I felt was great for fantastic braking performance. And I was pretty disappoint the rims were sub standard given the nice weight and braking. But never sold any thankfully. Just traded out to my bud after he bought my Addict LTD and put on terrible wheels having not taken wheels with it. Narrow rim heavy yada, That bike deserves super duper wheels.

[hoj]

Thanks all for the replies! Encouraging to hear that in some respects the building process is easier with carbon rims.

BTLOS happens to have a free shipping promotion going on currently... what coincidental timing lol.

[Mark McM]

I agree with Peter - when it comes to building/truing wheels, carbon and aluminum rims are far more alike then they are different. The same principles and practices apply to both, regarding lacing, tensioning and truing. About the only things to watch for with carbon rims are: The manufacturers recommended maximum spoke tensions tend to be a little bit lower for carbon rims (I'm not sure why this is - maybe because carbon has much less ductility); as noted above, galvanic corrosion is always a concern with aluminum nipples, but it may be a little more of a concern with carbon/aluminum interfaces; carbon rim spoke beds tend to be little thicker, so nipples tend to be able to rotate less in the spoke holes, so you may want to pay a little more attention to correcting the spoke line (i.e pre-bending the spokes) where they emerge from the nipple and bend toward the flanges.

As far as stress-relieving (as by squeezing pairs of spokes together to momentarily over-load the spokes): I always do this, and this has never caused a problem with carbon rims.