# Pacenti rim cracks



## jmorgan (Apr 13, 2012)

Just looked over my wheel to check everything and make sure it was all good and found some cracks. Here is the worst one. Notes from when I built the wheel have this one at 15 (131Kgf) on a park meter. Cracks are on the DS. Rim has a couple thousand miles maybe 4kish. These were some of the first rims released and got them from Fairwheelbikes. 

Anyone else have this happen?


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## valleycyclist (Nov 1, 2009)

I had one rear wheel that I have built with an SL23 rim come back after 6 months with similar cracks on some rear DS spoke holes. I didn't exceed 120kg-f spoke tension. That was a 24 spoke wheel with a 160lb rider.

I rebuilt it with Sapim small oval nipple washers and hope it will last this time.


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## jmorgan (Apr 13, 2012)

valleycyclist said:


> I had one rear wheel that I have built with an SL23 rim come back after 6 months with similar cracks on some rear DS spoke holes. I didn't exceed 120kg-f spoke tension. That was a 24 spoke wheel with a 160lb rider.
> 
> I rebuilt it with Sapim small oval nipple washers and hope it will last this time.


This is also 24 hole DS spokes and im 160 now, was maybe 180 when they were first built. 

I notice looking on FWB that in the comments they recommend 110Kgf now. I know when I built it everyone was saying 130 was fine. 110 sounds a bit low bit low especially if I was using a crappy hub (I'm using CK).


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## dcgriz (Feb 13, 2011)

jmorgan said:


> 110 sounds a bit low bit low especially if I was using a crappy hub (I'm using CK).


I agree. If the hub geometry results to a tension ratio of 0.45 or below, the expected NDS tension will be below 50 kgf and, IMO, it's not enough to reliably keep nipples in check unless you Loctite them although doing so would give you another set of problems.
Furthermore, if the rim consistently cracks at 120 kgf I would not trust it at 110 kgf simply because I consider such a small reduction in tension logistically very difficult to reliably measure with the commonly available tension meters and their margin of error. I would want to have a greater safety margin, more like around 20 kgf, to allow for variances in tension measurement accuracy. Note that even the highest quality meter is subject to a 10% error.

Edit to add: 28 and 32 spoke rims may fare better since more spokes carry the load.


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## Mackers (Dec 29, 2009)

I had the same thing happen, 24h rear, 7801 hub, built to ~115 DS tension, 130 pound rider. After about 2000 miles the first cracks appeared. I rebuilt with an XR-279. She didn't like the Kinlin's extra weight, but the rim holds up just fine.


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## ergott (Feb 26, 2006)

I've sent out a few hundred rims and got one back. I take that to my fault because the tension was cranked too high (one of the first wheels out). Since then I've kept the tension at about 125kgf and haven't had any other rims back. I think at that tension all is well.


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## Bog (Feb 2, 2005)

One thing I don't understand about ultimate wheel tension and is not often mentioned in these discussions is that when you put a tyre on a rim and pump it up to 100 psi say, the spoke tensions in the wheel drop by about 10 kgf. Surely this will tend to reduce the build tensions down to below rim manufacturers recommended levels. 

If you build a wheel at the lower end of recommended rim tensions because you may be worried about eyelet cracking, then isn't there a danger that the NDS spoke tension could be dangerously low?


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## dcgriz (Feb 13, 2011)

It appears that accurately determining the applied spoke tension to this rim is paramount because the threshold seems to hover around the 120-125 kgf mark. 

Calibrating the tension meter and particularly a meter like the Park for the exact load and specific spoke in use seems to be critical if the maximum allowable tension is to be applied and long term rim durability is also desired.

These are the challenges bestowed by the seemingly continuous market push to reduce component weight and our understanding on when and how to best use these components when choosing wheels for racing, training or racing/training.


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## bikerjulio (Jan 19, 2010)

Just a question, because I have a set of Pacentis that still seem OK but I know I built them to a fairly high tension...............

As well as static tension, is not dynamic tension just as, if not more important, when thinking about this issue? And wouldn't dynamic tension at the rim be also a function of the elasticity of the spoke? So would using a skinny spoke like a Laser be less stressful over the bumps than a straight gauge spoke?

Just asking.


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## dcgriz (Feb 13, 2011)

Bog said:


> One thing I don't understand about ultimate wheel tension and is not often mentioned in these discussions is that when you put a tyre on a rim and pump it up to 100 psi say, the spoke tensions in the wheel drop by about 10 kgf. Surely this will tend to reduce the build tensions down to below rim manufacturers recommended levels.
> 
> If you build a wheel at the lower end of recommended rim tensions because you may be worried about eyelet cracking, then isn't there a danger that the NDS spoke tension could be dangerously low?


The 120 kgf tension limit has been the rim manufacturer's max safe allowable limit for a very long time and before the lightweight rims earned such popularity. DT Swiss, for instance, is listing 120 kgf for all of their rims including the double eyeleted, the 585, the 540, the e-trek and everything else in between. I think it had been derived with a lot of inherited safety, in a similar fashion as the max allowable pressure stamped on the side of the tires, for rims that were constructed for higher tension thresholds.
Nowadays we are pushing more and more for lesser weight but thinner extrusions with taller rims for harnessing aero benefits are taxing this convention.

IMO, the user needs to decide and pick the best rim for the application. If the rim is designed to be part of a racing wheel then immediate performance is the primary concern and long term durability should be of secondary importance. Similarly, a do it all combination racing/training wheel should not use a lightweight rim with the lowest number of spokes possible, if long term durability is in focus.


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## dcgriz (Feb 13, 2011)

bikerjulio said:


> Just a question, because I have a set of Pacentis that still seem OK but I know I built them to a fairly high tension...............
> 
> As well as static tension, is not dynamic tension just as, if not more important, when thinking about this issue? And wouldn't dynamic tension at the rim be also a function of the elasticity of the spoke? So would using a skinny spoke like a Laser be less stressful over the bumps than a straight gauge spoke?
> 
> Just asking.


It seems to me, the number of spokes would play a greater role rather than the type of spokes because the fewer the spokes the higher the load each sees when they go through the loading/unloading cycles when the wheel is in use.


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## Heuston (May 23, 2013)

I'm about to build up a set of wheels with the SL23 and wasn't sure if I should worry about nipple washers - ended up contacting Pacenti for advice. I received an email from Kirk Pacenti himself advising me to use nipple washers. I expect this will reduce the likelihood of cracking. 

(FYI He also advised me (180 lbs) to go with a 24/28 spoke count instead of the 20/24 I had planned).


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## bikerjulio (Jan 19, 2010)

This thread is making me think of going back and rebuilding my rear wheel with DS washers.


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## Mike T. (Feb 3, 2004)

bikerjulio said:


> This thread is making me think of going back and rebuilding my rear wheel with DS washers.


Maybe  that's not  a  bad idea.


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## Kirk Pacenti (Mar 18, 2006)

jmorgan said:


> Just looked over my wheel to check everything and make sure it was all good and found some cracks. Here is the worst one. Notes from when I built the wheel have this one at 15 (131Kgf) on a park meter. Cracks are on the DS. Rim has a couple thousand miles maybe 4kish. These were some of the first rims released and got them from Fairwheelbikes.
> 
> Anyone else have this happen?
> 
> View attachment 293746


jmorgan,

Sorry to see your rim has cracked. We will (through your point of purchase) get you taken care of. 

Fwiw, we have been keeping track of failures, and to date, of the 10,000+ SL23 rims we've sold, exactly 26 have failed. The trend in all of these failures have been low spoke count rear wheels (24h) with over tensioned spokes under heavier riders. I am not saying that is the issue with your wheel, and it's certainly not true in all cases, but so far that's been the norm in most instances. 

Nipple washers are never a bad idea, and as always, max spoke tension should be 125kgf. 

Cheers, 
KP


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## Bridgestone (Sep 6, 2007)

Wh


Kirk Pacenti said:


> jmorgan,
> 
> Sorry to see your rim has cracked. We will (through your point of purchase) get you taken care of.
> 
> ...


Recommended washers-link please.


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## Enoch562 (May 13, 2010)

Bridgestone said:


> Wh
> Recommended washers-link please.



Round PolyAx (HM) Washers (20 pieces)


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## Fignon's Barber (Mar 2, 2004)

I had the exact issue on a 24 spoke rear pacenti sl23 built by the infamous Trot Watson at Ligero Wheels. Hub is a White Ind T11. Figured I was SOL in dealing with Ligero, so I called Pacenti directly. They quickly sent me a replacement free of charge, no questions asked. Had the wheel rebuilt locally and have had no further problems so far.


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## Kirk Pacenti (Mar 18, 2006)

Fignon's Barber said:


> View attachment 293800
> 
> 
> I had the exact issue on a 24 spoke rear pacenti sl23 built by the infamous Trot Watson at Ligero Wheels. Hub is a White Ind T11. Figured I was SOL in dealing with Ligero, so I called Pacenti directly. They quickly sent me a replacement free of charge, no questions asked. Had the wheel rebuilt locally and have had no further problems so far.


FB,

Glad you're up an rolling again. We aim for 100% customer satisfaction, and will do everything we can to keep our customers happy and riding Pacenti products.

Cheers, 
KP


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## dcgriz (Feb 13, 2011)

Kirk Pacenti said:


> Fwiw, we have been keeping track of failures, and to date, of the 10,000+ SL23 rims we've sold, exactly 26 have failed. The trend in all of these failures have been low spoke count rear wheels (24h) with over tensioned spokes under heavier riders.
> 
> Nipple washers are never a bad idea, and as always, max spoke tension should be 125kgf.
> 
> ...


Kudos to you for acknowledging the issue, offer a solution and stand behind your product.


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## valleycyclist (Nov 1, 2009)

Enoch562 said:


> Round PolyAx (HM) Washers (20 pieces)


These fit too:

Small Oval Nipple Washers (20 pieces)


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## cdhbrad (Feb 18, 2003)

KP: What would be Pacenti's recommended maximum rider weight when using the 24 hole SL23 rim for a rear wheel? Besides high spoke tension being a factor, does the lacing pattern used seem to make any differences in the failures that have been noted?


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## Andreas_Illesch (Jul 9, 2002)

Kirk Pacenti said:


> Sorry to see your rim has cracked. We will (through your point of purchase) get you taken care of.


I guess the thickness of the sl23's bottom is 2mm or lower like many other of todays light aluminium clincher rims.
So why you guys don't go up to 2.5mm or even 3mm? 
Is it for manufacturing reasons?
Personally I wouldn't mind the weight increase of maybe 10-20 grams if I can avoid tinkering with washers.
The SL23 would still be a nice rim with an outstanding cross section and less than 500 grams.


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## Kirk Pacenti (Mar 18, 2006)

cdhbrad said:


> KP: What would be Pacenti's recommended maximum rider weight when using the 24 hole SL23 rim for a rear wheel? Besides high spoke tension being a factor, does the lacing pattern used seem to make any differences in the failures that have been noted?


In my opinion, 175-180 is the limit for any 24h rear wheel. 

We have had too few failures to draw any meaningful conclusions about lacing patterns as they might relate to rim failures. 

Cheers, 
KP


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## Kirk Pacenti (Mar 18, 2006)

double post.


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## Kirk Pacenti (Mar 18, 2006)

Andreas_Illesch said:


> I guess the thickness of the sl23's bottom is 2mm or lower like many other of todays light aluminium clincher rims.
> So why you guys don't go up to 2.5mm or even 3mm?
> Is it for manufacturing reasons?
> Personally I wouldn't mind the weight increase of maybe 10-20 grams if I can avoid tinkering with washers.
> The SL23 would still be a nice rim with an outstanding cross section and less than 500 grams.


Washers aren't very difficult to use, and they really do increase the durability of the rim, imo. [Whereas] a 2.5mm - 3.0mm spoke bed thickness would result in much more than a 10-20g weight increase.

Once you break 450g, you're talking about a different "class" of rim. I have nothing against heavier rims, but that's not the market we are pursuing at the moment. Maybe next year....

Cheers,
KP


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## Mike T. (Feb 3, 2004)

Kirk Pacenti said:


> Washers - a 10-20g weight increase.


My nipple washers weighed 9 grams total - for 52. 4g front, 5g rear.


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## Kirk Pacenti (Mar 18, 2006)

Mike T. said:


> My nipple washers weighed 9 grams total - for 52. 4g front, 5g rear.


Mike, I think you misread my post...

Cheers, 
KP


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## Mike T. (Feb 3, 2004)

Kirk Pacenti said:


> Mike, I think you misread my post...
> Cheers,
> KP


I think one would have to read both Andreas' post and your post to get the proper context of what you meant. I didn't read both of them.


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## cdhbrad (Feb 18, 2003)

KP: Appreciate the reply. Consistent with what a wheelbuilder for whom I have considerable respect also indicated. 

With less than 25 failures in 10K rims, I can see how you may not have enough data to know what lacing might impact failures.


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## rruff (Feb 28, 2006)

dcgriz said:


> It appears that accurately determining the applied spoke tension to this rim is paramount because the threshold seems to hover around the 120-125 kgf mark.


I doubt it. Probably a much wider range depending on how the wheel is built and used. These rims are quite light for their size, so they are not going to be forgiving. 

When you stress-relieve a wheel, the rim gets it as well as the spokes, hub, and nipples. 

Plus, a big part of the cyclic loading on the DS can be torque... mostly from climbing hard in low gears. 

Also, I always chamfer the nipple seats. Can't prove it helps, but couldn't hurt.


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## jmorgan (Apr 13, 2012)

rruff said:


> I doubt it. Probably a much wider range depending on how the wheel is built and used. These rims are quite light for their size, so they are not going to be forgiving.
> 
> When you stress-relieve a wheel, the rim gets it as well as the spokes, hub, and nipples.
> 
> ...


You are taking away some rim material when are chamfer them correct? I understand it helps the nipple seat better but I would think washers would be better and add more durability to the rim.


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## rruff (Feb 28, 2006)

It is a tiny bit of material... definitely not enough to hurt the strength, and it reduces the stress riser where the nipple meets the rim.

When I tried washers on a Stan's 340, they made the sidewalls bulge around the hole... there wasn't enough room for the nipple and two thicknesses of washer. That probably isn't an issue with the Pacenti rim though.


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## Enoch562 (May 13, 2010)

I get a little bit of bulging from the nipples now, might be a tight fit with the washers.


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## rruff (Feb 28, 2006)

Which washers do you use?


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## Enoch562 (May 13, 2010)

rruff said:


> Which washers do you use?


I haven't used any with the Pacenti rims, but if I do, I would be trying these...


Round PolyAx (HM) Washers (20 pieces)


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## jmorgan (Apr 13, 2012)

Just got my replacement rim from FWB (great customer service). I bought both the round and oval washers and will see how both sit in the rim. After I rebuild it I will try to update this with my impressions of both.


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## rruff (Feb 28, 2006)

Please do.


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## zucchiniboy (Apr 10, 2014)

May be a simpleton question, but if you use nipple washers on these, do you have to change the spoke length to compensate?


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## Mike T. (Feb 3, 2004)

zucchiniboy said:


> May be a simpleton question, but if you use nipple washers on these, do you have to change the spoke length to compensate?


Maybe. If spokes are being ordered I think the thickness of the washer should be accounted for (I added washers to my two dummy ERD measuring spokes). If the spokes are existing, then it depends on whether there is sufficient extra length. The thickness of my washers is in one of my earlier posts I think.


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## jmorgan (Apr 13, 2012)

Rebuilt the wheel today. The oval washers had a hard time trying to fit through the hole. Probably could of forced them in but didn't want them to get stuck in there. You could enlarge the hole just a little and they would fit. I went with the circular washers on the DS. Tensioning the DS was easier with them also, less spoke windup. They add a little bit more surface area, the oval ones would add a lot more surface area though but would require more work and be careful not to lose a washer in the rim it would suck trying to fish it out. Tensioned DS up to ~120. We will see if the washers and less tension help.


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## NJBiker72 (Jul 9, 2011)

jmorgan said:


> Just looked over my wheel to check everything and make sure it was all good and found some cracks. Here is the worst one. Notes from when I built the wheel have this one at 15 (131Kgf) on a park meter. Cracks are on the DS. Rim has a couple thousand miles maybe 4kish. These were some of the first rims released and got them from Fairwheelbikes.
> 
> Anyone else have this happen?
> 
> View attachment 293746


I had this exact thing happen to me last week. 

Got home from a long ride and wheel seemed out of true. Figured I would fix it when I got back from vacation. So got it up on the stand and did a quarter turn tighten on two spokes and on the third, there was that. 

Its Easter so I will ride the beater bike I guess and leave work early to get to the shop tomorrow night. 

Not sure what would have caused this. Wheels are less than a year old and just had them trued and whole bike tuned up about a month ago.


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## Enoch562 (May 13, 2010)

jmorgan said:


> Rebuilt the wheel today. The oval washers had a hard time trying to fit through the hole. Probably could of forced them in but didn't want them to get stuck in there. You could enlarge the hole just a little and they would fit. I went with the circular washers on the DS. Tensioning the DS was easier with them also, less spoke windup. They add a little bit more surface area, the oval ones would add a lot more surface area though but would require more work and be careful not to lose a washer in the rim it would suck trying to fish it out. Tensioned DS up to ~120. We will see if the washers and less tension help.



Did you get any noticable bulging in the spoke bed with the washers?


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## NJBiker72 (Jul 9, 2011)

By the way, what did it take to repair this? Hoping I am still under warranty but.


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## jmorgan (Apr 13, 2012)

NJBiker72 said:


> By the way, what did it take to repair this? Hoping I am still under warranty but.


I took the wheel apart and sent the rim into FWB (where I bought it with the invoice and return for warranty) they sent me a new one. I built the wheel back up with my old spokes, new nipples and washers on DS. 


Tried this trick to rebuild the rear and it worked well.
Wheel Building Tip No. 6 - Build Rears from Right to Left - Wheel Fanatyk


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## jmorgan (Apr 13, 2012)

Enoch562 said:


> Did you get any noticeable bulging in the spoke bed with the washers?


No, no bulging. The round washers are just a little wider than the nipple. I think the washer sits (interface with the rim) a little better in the rim than just the nipple. Also my rim was center drilled so I think It might help provide a wider area that is in contact with the rim. 

No reason not to use washers on the DS.


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## NJBiker72 (Jul 9, 2011)

jmorgan said:


> I took the wheel apart and sent the rim into FWB (where I bought it with the invoice and return for warranty) they sent me a new one. I built the wheel back up with my old spokes, new nipples and washers on DS.
> 
> 
> Tried this trick to rebuild the rear and it worked well.
> Wheel Building Tip No. 6 - Build Rears from Right to Left - Wheel Fanatyk


Thanks. I am hoping it is still under warranty. I think it is just under 1 year. Funny thing is I have not beaten it up much recently. Hit a huge pothole a month after getting it and took it in to get checked. It was fine. Just had the whole bike tuned/trued maybe a month ago too. Plenty of care given but wheels were fine. Not sure what could have caused this.


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## atpjunkie (Mar 23, 2002)

Kirk Pacenti said:


> In my opinion, 175-180 is the limit for any 24h rear wheel.
> 
> We have had too few failures to draw any meaningful conclusions about lacing patterns as they might relate to rim failures.
> 
> ...


I never can understand why heavy riders choose low spoke wheels
I'm well over 200 and don't go below 32.


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## NJBiker72 (Jul 9, 2011)

atpjunkie said:


> I never can understand why heavy riders choose low spoke wheels
> I'm well over 200 and don't go below 32.


I agree but it is really what everyone sells. I am 175 and went with 28.


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## jmorgan (Apr 13, 2012)

Oh yea and the washers made my spoke length right on. Calculated 281.3 (old) +.7 for washers to 282 (new) (which is what I was using anyways, CX-Ray tend to come in even #'s).

Also tried out Rock N Roll nipple cream (was going to use it on the NDS only) but didn't like it overall. I used only motor oil as lube on the wheel the first time and never had issues so I ended up just using motor oil again. If built right there shouldn't be any issues, the CK hubs might help with providing enough tension so depending on the whole setup of the wheel.

Forgot how much a difference wheels and tires can make. 

Went back to stock wheels for 2 weeks, Fulcrum 5 with vittoria rubino tires and butyl tubes. First ride back on the Pacenti, CK, Michelin Pro 4 and latex tubes. Ride is night and day difference and much more pleasant. These wheels ride so much better, I would recommend these to anyone and if you need to save some money, get some WI hubs or BHS hubs.


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## Heuston (May 23, 2013)

Kirk Pacenti said:


> In my opinion, 175-180 is the limit for any 24h rear wheel.
> 
> We have had too few failures to draw any meaningful conclusions about lacing patterns as they might relate to rim failures.
> 
> ...


I'm around 81kgs and been running Pacenti sl23s with 20/24 spokes (radial front two cross rear), Sapim spoke washers, Novatec hubs and CX ray spokes since August last year - including 1300w Max efforts.

I've trued the rear wheel once. Never had to touch a spoke on the front.


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## nealio (Nov 8, 2014)

*Another one to add to the pile*

Hey - found this thread, have had the same issue

It's a 24h rear, and I weight just under 70Kgs (less than 155 pounds), wouldn't have thought that was the problem. Recently had the wheel trued by a mechanic.

I bought the rim April 2014, but had issues getting the hub + spokes, think it was August before it was built - so less than a year on the road.


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## NJBiker72 (Jul 9, 2011)

nealio said:


> Hey - found this thread, have had the same issue
> 
> It's a 24h rear, and I weight just under 70Kgs (less than 155 pounds), wouldn't have thought that was the problem. Recently had the wheel trued by a mechanic.
> 
> ...


My shop warranteed mine.


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## nealio (Nov 8, 2014)

I emailed the shop yesterday - waiting to hear back from them


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## NJBiker72 (Jul 9, 2011)

nealio said:


> I emailed the shop yesterday - waiting to hear back from them


Mine looked very similar. So dogs another friend's.


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## rlb81 (Feb 2, 2010)

Add another to the list. 3 drive side, 2 trailing and one leading (the worst of the bunch).

I bought these wheels second hand so I don't have all of the details of the build. I do know they were built by someone who has a lot of wheel building experience. Not fair for me to try and say what's at fault with so many unknowns, so I guess add this to the list of reasons to make sure the tension is never adjusted beyond the recommendation, especially when someone else is making adjustments after the fact.


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## wrxg33k (Feb 19, 2007)

rlb81 said:


> Add another to the list. 3 drive side, 2 trailing and one leading (the worst of the bunch).
> 
> I bought these wheels second hand so I don't have all of the details of the build. I do know they were built by someone who has a lot of wheel building experience. Not fair for me to try and say what's at fault with so many unknowns, so I guess add this to the list of reasons to make sure the tension is never adjusted beyond the recommendation, especially when someone else is making adjustments after the fact.


I had the same thing happen...twice to a v1 rim. 20/24 Powertap G3 rear hub. First failure no washers, all drive side cracked (scary!), then rebuilt with a warrantied rim with washers, about 1500 miles later it failed again but only 3 spokes. *Kirk has given great service* and now has a v2 rim on it's way to me. I vary 165 - 180lbs and can top out 1600 watts. I used them for both training and racing. 

I have a good chunk of change tied up in my 24h powertap so I'm hoping the v2 rim is good to go now.


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## rruff (Feb 28, 2006)

wrxg33k said:


> I had the same thing happen...twice to a v1 rim.


How many miles on the first one? Is the front a SL23 as well?


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## wrxg33k (Feb 19, 2007)

Front is SL23 with a velocity race hub, 20h. No issues. Stays true.

There was probably 3-5k miles on the first v1 failure, significantly less miles on the second failure, probably around 1500 or so.


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## rruff (Feb 28, 2006)

Interesting that the washers didn't seem to help. 

Who built them?


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## wrxg33k (Feb 19, 2007)

LBS that builds lots of wheels.


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