Problems with Zipp Vuka Aero Bar extension loosening

Jun 5, 11 14:15

Post #1 of 18 (9118 views)

I am having constant problems with my aero bar extensions loosening up during rides where there may be rough roads - perhaps from vibration.

I have found that the end of the aero bars inserted into the Vuka base bars have been splintering (or cracking). I have trimmed them (shorted them to clean up these cracked areas) cleaned the collet compression fittings and re assembled per the Zipp website manual found here - http://www.zipp.com/.../vukaaero_manual.pdf . All seems fine until an hour into the weekend ride when one of the extensions always gets loose.

Observations - I noticed that the extensions appear round on the outside but are not round on the inside meaning there is asymmetry in the inside wall thickness of the bars which are weak points and crack - especially on the edges which first get compressed by the collet compression nut. - I do not over tighten the collet screws because I am using the collet tool provided by Zipp which allows only a certain level of tightness.

I am a little surprised to see that there is asymmetry on the wall thickness of my extensions so I went down to the LBS to look at new extensions and also found the same thing on the new bars - Asymmetry in the wall thickness.

Before I forget - yes I have used Carbon Paste with the same results per the recommendation of the LBS.

Any other suggestions welcomed.... is this a common problem? Actually is very dangerous on descents when your on the hoods because you don't really notice the bar flopping around until you go back into the aero position.

Last edited by: scca_ita: Jun 5, 11 14:21

Re: Problems with Zipp Vuka Aero Bar extension loosening [scca_ita] [ In reply to ]

Jun 5, 11 14:34

Post #2 of 18 (9109 views)

I have the exact same problem with my Vuka Clips and extensions. I tried carbon paste per Zipp's recommendation but that didn't make any difference. In my case tightening the collet to the max recommended tightness just didn't grab the extension enough. Almost as if the extension wasn't a large enough diameter. I'm working with my fitter who I purchased them from to get a replacement from Zipp, but in the meantime I wrapped a single layer of electrical tape over the top of the shim type extensions that the collet compresses over the extensions. This was just enough to add a little more thickness and therfore compression and grab the extension properly. It hasn't come loose since and before it was loosening after every single ride no matter how long or short. Not a permanent solution, but I've done 2 3 hour rides on them without any issues now.

Re: Problems with Zipp Vuka Aero Bar extension loosening [Nickwisdom] [ In reply to ]

Jun 5, 11 15:46

Post #3 of 18 (9088 views)

Ok - thanks I was considering the same - adding a little bit of diameter (shim) to the front part of the extension that is in the collet compression fitting. This way the collet can compress down on the front part at the same time as the rear. Having the collet compress first on the rear part of the extension which is the weakest is a very poor design because it will either crack the extension as in my case or if it loosens up, it is the only place that really has a hold of the extension.

Zipp and my LBS said not to push the extension all the way back into the collet but rather insert it about 5mm from the back and this will allow the collet to have more even grip - I did this also but same thing - will loosen up eventually on ride.

Re: Problems with Zipp Vuka Aero Bar extension loosening [scca_ita] [ In reply to ]

Jun 5, 11 17:00

Post #4 of 18 (9072 views)

+1
My Vulka clip-on and extenstion do the same thing. Tighten it up, seams fine and one big bump later the thing is loose again. Kind of piss off about it. Have to keep tightening by hand for the rest of the ride. I will try shiming with some electrical tape.

Re: Problems with Zipp Vuka Aero Bar extension loosening [scca_ita] [ In reply to ]

Jun 5, 11 17:56

Post #5 of 18 (9063 views)

Did you try using some loctite on the collet threads?

"Non est ad astra mollis e terris via." - Seneca | rappstar.com | FB - Rappstar Racing | IG - @jordanrapp

Re: Problems with Zipp Vuka Aero Bar extension loosening [Rappstar] [ In reply to ]

Jun 5, 11 18:04

Post #6 of 18 (9060 views)

Rappstar wrote:

Did you try using some loctite on the collet threads?

Yep... I did. No luck with that either... the problem in my case wasn't so much that the collet wasn't staying tight... it was that when it was screwed down as tight as it should reasonably go, it still didn't grab the extension enough to hold it tightly. Its as if the extension is just a tiny tiny bit too small diameter wise and the collet assembly can't properly hold it.

Re: Problems with Zipp Vuka Aero Bar extension loosening [Nickwisdom] [ In reply to ]

Jun 5, 11 18:16

Post #7 of 18 (9050 views)

Nickwisdom wrote:

Rappstar wrote:

Did you try using some loctite on the collet threads?

Yep... I did. No luck with that either... the problem in my case wasn't so much that the collet wasn't staying tight... it was that when it was screwed down as tight as it should reasonably go, it still didn't grab the extension enough to hold it tightly. Its as if the extension is just a tiny tiny bit too small diameter wise and the collet assembly can't properly hold it.

It *might* be that you have some older Zipp extensions. Zipp's extensions were originally 22.0mm - instead of 22.2, the industry standard. The collet's were designed - appropriately - around 22.2 extensions. but that 0.2mm might be enough. I'd suggest, unfortunately, trying some other extensions - HED, Oval, etc. I think that's a very real possible source of the problem. Unfortunately, I don't think that helps as much as I'd like. But it's the only thing I can think of that would cause the problem as you describe it...

"Non est ad astra mollis e terris via." - Seneca | rappstar.com | FB - Rappstar Racing | IG - @jordanrapp

Re: Problems with Zipp Vuka Aero Bar extension loosening [Nickwisdom] [ In reply to ]

Jun 5, 11 18:18

Post #8 of 18 (9044 views)

My vuka base bar had "some" cracks in in it. Two IMLP later with a piece of a redbull can as a shim it started slipping again.
Thankfully a replacement from Zipp came in and so far so good. No slip at Rev3 today.

Re: Problems with Zipp Vuka Aero Bar extension loosening [triathmd] [ In reply to ]

Jun 5, 11 18:41

Post #9 of 18 (9037 views)

I put a piece of electrical tap around the extension at the point where the extension comes out of the collet. About 2mm of the tape is showing outside the collet (or just in front of the collet) so the "fingers are clamping on the tape. It feels tighter and there is no "Creaking" noise when you pull up on the extensions.

Jordan - The 0.2mm may be the difference and I am willing to give this a try after IMF..... My bars are still under warranty (2 years) on my FELT DA so perhaps I can get them replaced..... ?

Re: Problems with Zipp Vuka Aero Bar extension loosening [scca_ita] [ In reply to ]

Jun 5, 11 18:55

Post #10 of 18 (9031 views)

scca_ita wrote:

Jordan - The 0.2mm may be the difference and I am willing to give this a try after IMF..... My bars are still under warranty (2 years) on my FELT DA so perhaps I can get them replaced..... ?

You should certainly ask. CS is gnerally outside my area of expertise; but I'd be surprised if the product is still under warranty and Zipp didn't do what they can to rectify a problem.

"Non est ad astra mollis e terris via." - Seneca | rappstar.com | FB - Rappstar Racing | IG - @jordanrapp

Re: Problems with Zipp Vuka Aero Bar extension loosening [Rappstar] [ In reply to ]

Jun 5, 11 19:40

Post #11 of 18 (9023 views)

I'm fairly certain that these are the newer extensions as they were purchased new a couple of months ago from a Zipp dealer who had to order them (so not older stock I'd presume) I'll check the box though. Odd though that one is narrower than the other.. especially considering mine are the Vuka Shift extensions which come as a set. I really like these extensions so Im hopeful I will get this sorted. Having the shifter that much closer to the s bend makes them really comfy for me. More so than the similar shaped extensions they replaced.

Re: Problems with Zipp Vuka Aero Bar extension loosening [Nickwisdom] [ In reply to ]

Jun 6, 11 7:08

Post #12 of 18 (8986 views)

You would think that if you spent a grand on aerobars they would tighten properly?

Re: Problems with Zipp Vuka Aero Bar extension loosening [scca_ita] [ In reply to ]

Jun 6, 11 7:35

Post #13 of 18 (8978 views)

Same issue here. Same setup. Had the Vuka Extensions on the Vuka Bull base bar for 3+ years now. They're crap on a stick. My method for tightening has been to tighten them down by feel to what I think is right. Put a band of electrical tape right at the end of the collett sleeve on the extension (as a marker) so I can see if/when they loosen or slip. If they loosen during my next ride I re-position, and tighten just a hair further. Go for another ride and repeat the process of just gradually tightening them down. This has worked for me. The hardest lesson I've learned is just to not mess with this stuff too much. I cracked a Vuka Bull base bar a week before IMMOO a couple years ago because I was dicking around with the torque setting for no good reason. This because of the advice of a stupid coach who told me 7 days before a race "Tighten your bolts"- stupid advice...if you've ridden hundreds of miles already in training, over bumps and crap in the road, no race condition is going to suddenly jar a bar or clamp loose unless you hit a monster pot hole or crash your bike.

My rules for carbon parts are:

1. No one, I mean no one, tightens my stuff but me. When I drop off my bike to the LBS for a tune or cable replacement I tell them "I've already tightened my bolts to spec, please don't touch them".
2. Tighten to spec, ride, re-tighten if necessary. If it doesn't move or slip, leave it be. Very small, incremental moves.

Re: Problems with Zipp Vuka Aero Bar extension loosening [Rappstar] [ In reply to ]

Jun 6, 11 7:43

Post #14 of 18 (8971 views)

Quote:

Zipp's extensions were originally 22.0mm - instead of 22.2, the industry standard. The collet's were designed - appropriately - around 22.2 extensions.

Pretty sure that they still are. Per their website:

Diameter22.0mm +0,05mm -0.15mm
I sure hope that they are still 22.0, as the 22.2 do not fit in the USE Tulas, which is why the Zipps are on their way to me now. HED are also 22.0, IIRC. The Felt F-bends I got were 22.2.

Re: Problems with Zipp Vuka Aero Bar extension loosening [scca_ita] [ In reply to ]

Jun 6, 11 9:29

Post #15 of 18 (8958 views)

Checked in with the Zipp folks.

First off, my apologies. Everything at Zipp is still designed around a 22.0 extension diameter. There is, as indicated on the site, some variance in the manufacturing, which is some of what causes problems.

Tips from Zipp:
1) Finishline carbon paste is really chunky/gritty and will add some thickness to undersized extensions. This is the paste of choice at Zipp

2) make sure you have AT LEAST 3cm inside the collet. This is the minimum. Less than this, and the extensions WILL slip. So double check to make sure you didn't cut them too short.

Hope that helps. Sorry for any confusion I added...

"Non est ad astra mollis e terris via." - Seneca | rappstar.com | FB - Rappstar Racing | IG - @jordanrapp

Re: Problems with Zipp Vuka Aero Bar extension loosening [Rappstar] [ In reply to ]

Jun 6, 11 15:02

Post #16 of 18 (8930 views)

Thanks for the info and for checking up on it. Much appreciated.

Re: Problems with Zipp Vuka Aero Bar extension loosening [grnfsh] [ In reply to ]

Jun 6, 11 15:16

Post #17 of 18 (8924 views)

grnfsh wrote:

You would think that if you spent a grand on aerobars they would tighten properly?

You could say something similar about any number of bikes and products in the triathlon industry. It's not about what they cost and whether they had an issue... It's about how they respond when you bring it to their attention. In my case Zipp has been very helpful and extremely easy to get ahold of. I have no complaints.. I'm just looking to fix the problem on my own before I ask to have it replaced.

Plus the molded in shift bosses right after the s bends are awesome for my little T-rex arms!

Re: Problems with Zipp Vuka Aero Bar extension loosening [Rappstar] [ In reply to ]

Jun 7, 11 8:04

Post #18 of 18 (8900 views)

Rappstar wrote:

Checked in with the Zipp folks.

Tips from Zipp:
1) Finishline carbon paste is really chunky/gritty and will add some thickness to undersized extensions. This is the paste of choice at Zipp

2) make sure you have AT LEAST 3cm inside the collet. This is the minimum. Less than this, and the extensions WILL slip. So double check to make sure you didn't cut them too short.

Hi Jordan

Thanks for the feedback. In my experience "Carbon Paste" = Remedy for poor engineering and manufacturing. I have used the Finishline carbon paste with the same result - however it did last longer and the collet loosening was more gradual. I guess I will see what my LBS can do for me - I have lost all confidence in these bars and dont want to be consciously checking them in a race.

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