Thanks for the review!

Noahman,

Sorry you had issues with the Delta Sonic. I understand if you are looking for a conventional rear setup that mounts to the seat, however we are very interested in figuring out the issue that caused the rod to pop out of the seatpost groove as this is the first I have heard of it happening. I wanted to see if you were able to send pictures of the setup installed?

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Candice Turner
CEO
XLAB - Aerodynamic Triathlon Accessories
Dawn to Dusk - Off-road Specific Storage Accessories
http://www.XLAB-USA.com http://www.dawntodusk.bike

You are inserting the rod actually into the seat post hole and not just screwing it to the channel on the top aren't you? I can't see how it can pop out of anywhere and that post could likely support my weight, let alone the weight of a bottle.

Can you post pics of the setup?

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https://www.pbandjcoaching.com
https://www.thisbigroadtrip.com

Hi Candice ... thanks for being on this forum for support. I am not the original poster but have a problem with the Delta Sonic that damaged my seat post and made the Sonic useless. Using a torque wrench, the small washer went right into the carbon long before reaching the 30lb-in limit. Worse ... it cracked the seat post at two locations (you can also see how the carbon edges are bent to the outside because of pushing the washer down). I talked to an XLAB engineer about using a larger washer last Fri ... which would be intuitive to me unless the thought behind using this small washer is that it is actually supposed to cut into the carbon ... but the engineer insisted that I keep using this washer (and fresh loctite) and go up to 30lb-in ... which I did. The result was that the rod was super tight until I went for my next ride and the washer simply cut further into the carbon and the entire set-up became loose again .... to a point where it is useless to further tighten it because the washer is close to making contact with the rod. The picture below was taken before I went for my final ride. Where did I go wrong?
Stefan
Edit: This is on a NP3

Hi Stefan,

I haven't ignored you :) Just investigating it here. Will sit down with the CEO who is also our primary designer to discuss.

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Candice Turner
CEO
XLAB - Aerodynamic Triathlon Accessories
Dawn to Dusk - Off-road Specific Storage Accessories
http://www.XLAB-USA.com http://www.dawntodusk.bike

Thanks, Candice. Looking forward to the response.

Hi Stefan,

We re-tested a Delta Sonic install and torqued it to 30in-lb. We then torqued it to 40in-lb and pulled down on the cage to simulate rattling. The mark left on the post was just a very slight groove where the washer was, certainly not the extent to how your post is. You can see there is quite a bit of seat post to keep the washer from going into the groove. The other 2 cracks could be that the Delta Sonic wasn't torqued down initially and as the rod moved around it wore the seat post, or if it was torqued, it could be the seat post is defective.

How long have you had the post & the Delta Sonic? There is quite a bit of wear on yours vs ours, so I am curious :)

If you can get a replacement seat post from the store you bought it at or directly from Cervelo, we can help walk you through the install over phone or Skype.

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Candice Turner
CEO
XLAB - Aerodynamic Triathlon Accessories
Dawn to Dusk - Off-road Specific Storage Accessories
http://www.XLAB-USA.com http://www.dawntodusk.bike

Hi Candice ... thanks for doing the test and posting the picture ... which I think convincingly shows why the sidewalls on my post bent outward when the washer was tightened ... ultimately inducing cracks at a torque of much less than what you used. As you noted, the top surface of these sidewalls on my seat post looks nothing like the post that you used. I have used the bike less than 10x (it's brand new) but the the top surface is not as smooth and the edges are not as well defined (compared to yours). Again ... this is a NP3 that I have. I have no doubt that the Sonic Delta works great on a seat post like yours. Do you know whether all new Cervelo posts are supposed to look like the one you show ... or whether the Sonic is potentially incompatible with this generation of seatposts that I have?
Stefan

PS Sorry for late response. I have been traveling with 2 little kids ... but at least I ended up in Hawaii ... so I am not complaining :-)

Mine looks exactly like the one Candice has posted.

To me it looks suspiciously like the delta sonic has taken a sharp impact from below and cracked the seat post through poor handling, rather than any damage the rod could do itself with the weight of a bottle alone. Just saying...

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http://www.twhatley.com

Glad to hear that my post might be an outlier.

Thanks for offering a speculation ... but it does not apply because firstly the crack occurred during tightening the screw the first time around (the outward bent of the flanges happened at this point which allowed the washer to get "swallowed" into the channel) and even if it didn't ... an impact from below could only induce the crack at the end of the channel ... but not the one towards the front of the seatpost ... which, again, is entirely consistent with a failure mechanism based on the flanges being pushed outward.

Anybody else whose NP3 seatpost looks like Candice's?

I highly recommend you look at getting a replacement seat post. As you may be aware we work very closely with Cervelo. We have 2 new P3s here along with a couple other Cervelo models....they all have seat posts like the one I posted.

A lower torque setting wouldn't do near the damage as a higher torque setting would, thus why we tested it at 10in.lbs more than we recommend to see if we could crack the seat post.

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Candice Turner
CEO
XLAB - Aerodynamic Triathlon Accessories
Dawn to Dusk - Off-road Specific Storage Accessories
http://www.XLAB-USA.com http://www.dawntodusk.bike

Sounds good. I will contact the LBS and give an update hopefully soon.

To follow up ... I finally made it to my bike store and Sunrise Tri gave me a new seat post (thanks, Frank!!!). Perhaps even better, there was a customer who had a somewhat similar problem where the Sonic had broken the flange after something hit the waterbottle holder ... and he had the brilliant idea to use another seatpost head ... instead of the little screw and washer ... for attaching the Sonic (see picture). The posterior 2/3 of the second head will be cut when I find a minute. It feels a lot more solid than the original set-up. I tested it on a ride yesterday and so far so good. What do you think, Candice?
[/img]

Hi all,

I have the same problem. Just purchased the X-Lab Delta Sonic and now have a small hairline crack in the back of the 2014 P2 Cervelo seat post track (Bottom of U section). I was wondering, would a small rubber washer in between the metal washer and the carbon seat post track eliminate any possible damage when torquing down the screw during install.

If your case is similar to mine, then this small crack will become larger and larger because the Sonic will become loose after every ride ... and you will have to tighten the screw further and further ... which will open up the crack. As demonstrated by Candice in a post above, the problem is not the torque per se ... but that some seat posts are simply not manufactured to the precision that accommodate the (kind of flimsy) screw with washer. A rubber washer will not make a difference ... or be counterproductive if it decreases the total force induced in the screw (because the Sonic will more likely to become loose). If my experience holds up ... your best bet (by far) will be to get a new seat post ... and either hope that it will accommodate the torque recommended by X-Lab ... or go my route with the second head which I continue to be extremely happy with. Sorry for the bad news.

Thanks for this review. Had one of these in the basket and just as an afterthought searched for a review...

I'll find another option!

Thanks JerseyBigfoot for the cross-reference to this thread. I just checked my NP3 seat post and it looks like the one pictured in Candice's post. I see no cracks on my rails. The thing that catches my eye is that the OP has a very small amount of Sonic inserted into the seat post. My saddle is adjusted so that it sits on the rear part of its rails and the saddle/post clamp is slammed forward on the seat post, thereby maximizing the amount of Sonic inserted the seat post.

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/Howie Nordström

My seatpost just got cracked at the end like post # 5. There should be caveat that Delta Sonic works only if inserted x mm inside, or should be sold with a better fastener similar to the seatpost head in post # 14.

Does anyone have 1/2 a seatpost head? Or willing to get one and split with me?

Otherwise I'll have to go with a saddle mounted solution like Delta 400 (not giving up on X-Lab yet). Haven't seen the Aero Pouch 300 out on the market though...

I'm thinking of buying an X-lab Delta Sonic so this is very interesting to me.
I have a steel rod of 10mm diameter laying around so I'm also thinking to make one myself.

A couple of thoughts:
I learned already from another post, that an aluminium rod is too weak: it will crack at the bend.
Baliman's idea with the seatpost head is absolutely great and I think X-lab should provide for such parts with their bottleholder.
I think also about making a second hole in the rod, and cut screwthread in it, such that the rod is held by 2 screws on the seatpostrails.

I will bring this up again with our engineering team and perhaps we have a Cervelo seatpost support. Unfortunately we are only seeing a couple here and there, and they are always with Cervelo posts. Will keep everyone updated on the progress. We do recommend a minimum of 1" insertion.

Thanks for not giving up on XLAB! Also for the Aero Pouch 300 expect 1 more month or so on those. I highly recommend if you want one, to get one on order with your local store. We are expecting to sell out of our first batch.

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Candice Turner
CEO
XLAB - Aerodynamic Triathlon Accessories
Dawn to Dusk - Off-road Specific Storage Accessories
http://www.XLAB-USA.com http://www.dawntodusk.bike

Not sure if you thought the Delta Sonic rod was made out of aluminum or you were thinking of making one out of that material, but the rod is actually Stainless Steel.

As far as the seatpost head, will forward this idea to my engineer's and see if we can work something out. Will also mention the idea of bolting the rod down with 2 screws.

Thanks for the feedback everyone!

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Candice Turner
CEO
XLAB - Aerodynamic Triathlon Accessories
Dawn to Dusk - Off-road Specific Storage Accessories
http://www.XLAB-USA.com http://www.dawntodusk.bike

As an update ... the seatpost head as clamp still works like a charm. I would highly recommend it

I know your rod is from steel but I once thought about aluminium and I discovered that someone had already tried that. As I mentioned, it cracked at the bend. So your stainless steel solution is the right one.

Just curious the cost a replacement seat post....?