# Rear light for aero seatpost?



## koherston (Jan 19, 2011)

I am having a difficult time finding a rear light that will fit the aero seatpost on my Cervelo S3. I even tried the DiNotte 300R but their aero clamp is just a tad too small (the screw rubs/gouges the carbon post). Has anyone found a good solution (that doesn't involve putting it on a helmet or seatbag--I'm specifically looking for a seatpost solution)?


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## giantdefy2 (Dec 2, 2010)

Why does it have to be on the seatpost? Put it on the left seatstay.


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## autoxr.mike (Dec 7, 2009)

Modify the regular seatpost mount to use zip ties. I cut mine in about 1/2 (basically so it stopped where it started to curve back to a circle) to leave some reinforcement, drilled a hole in it near where my screw attached it to the light, and then zip tied it to the seatmast. I've got a Portland Design Works Radbot attached to it and it hasn't moved or slipped in the 5 or 6 rides I've had it on.


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## aengbretson (Sep 17, 2009)

A guy I ride with puts it on the wishbone-like structure of the seat stays, the part that branches off of the main triangle before the seat stays split off into separate entities.


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## koherston (Jan 19, 2011)

giantdefy2 said:


> Why does it have to be on the seatpost? Put it on the left seatstay.


The seatstays on the S3 are (1) tiny and (2) aero. As mentioned in the original post, I'm looking for a seatpost solution.

Why doesn't everyone make a seatpost mount that fits aero seatposts? Or at least offer it as an optional accessory?


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## koherston (Jan 19, 2011)

aengbretson said:


> A guy I ride with puts it on the wishbone-like structure of the seat stays, the part that branches off of the main triangle before the seat stays split off into separate entities.


On mine at least, there is no room whatsoever. The rear brake takes up that very small space.


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## aengbretson (Sep 17, 2009)

you mean this whole area is taken up? This is what I was referring to and at the very least there is room to run two Knog Frog lights or one Gecko (which is pretty good for visibility I might add)


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## backinthesaddle (Nov 22, 2006)

I run a Knog on my Ridley in the exact spot shown in the above picture. The LEDs are angled, so you must run it upside down, but it works very well!
And you can get it in black, so it's not terribly noticeable.
http://www.knog.com.au/gear-lights/skink.phps


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## wim (Feb 28, 2005)

koherston said:


> Why doesn't everyone make a seatpost mount that fits aero seatposts? Or at least offer it as an optional accessory?


Perhaps someone did, but found out it didn't sell well. Could be that people looking for every possible aero advantage on their bike don't want to put a light back there, ever. But perhaps not—lots of them put bottles back there. Which makes me wonder if you couldn't just modify a seat-rail mounted bottle cage or even smaller cage holder to put your light exactly where you want it.


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## aengbretson (Sep 17, 2009)

You could try rigging up a mount underneath your saddle - there has to be a way to mount the light to the rails. This would also put the light up higher and may be more visible to motorists.


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## koherston (Jan 19, 2011)

aengbretson said:


> you mean this whole area is taken up? This is what I was referring to and at the very least there is room to run two Knog Frog lights or one Gecko (which is pretty good for visibility I might add)


Yes. Here's a pic of my bike, which is a smaller size than the one you pictured.


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## koherston (Jan 19, 2011)

wim said:


> Perhaps someone did, but found out it didn't sell well. Could be that people looking for every possible aero advantage on their bike don't want to put a light back there, ever. But perhaps not—lots of them put bottles back there. Which makes me wonder if you couldn't just modify a seat-rail mounted bottle cage or even smaller cage holder to put your light exactly where you want it.


I have bottles behind the seat on my tri bike but not on my road bike. I agree about the aero advantage during a race but I'm looking for a light for everyday training rides that force me to deal with idiot drivers who are probably texting instead of looking for cyclists. I'm trying to find a superbright light that cannot be missed, even in daytime. I was hopeful with the DiNotte 300R but the aero clamp is too small for the S3 seatpost. :mad2:


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## wim (Feb 28, 2005)

The PDW Radbot 500 or 1000 is very bright and comes with a seat post _and_ a seat stay clamp. The seat stay clamp also has a (removable) rubber insert, which reduces its inside diameter even more. I've got the 500 and it's plenty bright; the 1000 is even brighter, but at the expense of run time. Obviously, you'd have to give up the seat post idea.


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## Bill2 (Oct 14, 2007)

My Sigma Cuberider 2 is attached with an o-ring, like Garmin mounts.
http://www.sigmasport.com/en/produkte/beleuchtung/standard_lights/cuberider_2/


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## looigi (Nov 24, 2010)

The Princeton Tec Swerve taillight, which is very bright with two 1/2 W LEDs, mounts nicely on a seat stay using a heavy rubber o-ring so is easy to take on and off with no danger of marring the frame. It comes with a shorter o-ring and a grey rubber reducer that fits between the mount and stay to adapt it to the smaller diameter.


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## wim (Feb 28, 2005)

looigi said:


> The Princeton Tec Swerve taillight, which is very bright with two 1/2 W LEDs, mounts nicely on a seat stay


Good suggestion. But I'm guessing the OP is dead set against seat stay mounting. He needs to have his light on his seat post for reasons only he knows.


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## ragnar.jensen (Dec 28, 2008)

On one of my bikes I'm running a Magicshine MJ-818 taillight on the seat-post:










A little bit of DIY is required.


On other bikes I mount a Magicshine or a Dinotte 140 on the saddle rails:

















A plastic pipe with a couple of holes drilled in it, anti-slip tape and zip-ties.


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## looigi (Nov 24, 2010)

ragnar.jensen said:


> A little bit of DIY is required


Nice. A V-shaped notch in that piece of grip shaped to fit the back of the aero seatpost might do the trick.


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## koherston (Jan 19, 2011)

wim said:


> Good suggestion. But I'm guessing the OP is dead set against seat stay mounting. He needs to have his light on his seat post for reasons only he knows.


Have you seen the S3 seatstay? It's aero (i.e., not round, shaped like an airplane wing, etc.) and very, very thin. I could get a tiny, 1 LED Knog on there but not a big, bright light like the DiNotte 300R, which is perfect for brightness but won't fit the post.

I am settling for the 4 LED Knog. It's not nearly as bright as I'd like but it's the only thing (so far) I can fit to the aero post. Hopefully, light manufacturers will fill the void as aero frames become more common.


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## looigi (Nov 24, 2010)

koherston said:


> Have you seen the S3 seatstay? It's aero (i.e., not round, shaped like an airplane wing, etc.) and very, very thin.


It's been a while since I've seen one in person but looking at photos on the web it appears to me that the Princeton Tech Swerve might fit it as it does work on other thin seat stays, such as the BMC SLR01. I have several Swerves and I found the last one on Amazon for ~$15 (with free shipping if your order is >$25), so it might be worth a try. 

As ragnar points out below, with a little DIY, your options broaden considerably.


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## wim (Feb 28, 2005)

koherston said:


> Have you seen the S3 seatstay? It's aero (i.e., not round, shaped like an airplane wing, etc.) and very, very thin..


Seen and felt the R3 seat stays, so I think I understand your S3 seat stay problem. My previous post was a comment about insisting on the seat post mount, what with other attachment alternatives like seat bag, bottle cage or saddle rail. Sorry if I wasn't clear. Agree, an aero post mount does seem overdue.


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## mlinenb (Jul 21, 2008)

koherston said:


> Have you seen the S3 seatstay? It's aero (i.e., not round, shaped like an airplane wing, etc.) and very, very thin. I could get a tiny, 1 LED Knog on there but not a big, bright light like the DiNotte 300R, which is perfect for brightness but won't fit the post.
> 
> I am settling for the 4 LED Knog. It's not nearly as bright as I'd like but it's the only thing (so far) I can fit to the aero post. Hopefully, light manufacturers will fill the void as aero frames become more common.


This light will work fine- mounted on your seatpost or seat-tube, just below your seatpost clamp. My wife has a 48cm S3 and I have a 56cm S3. Light works perfectly. 

get the performance bike light- (it has a great mount for aero framed seat tubes).
ViewPoint Flashpoint Ultra Tail Light

I've now just started using this clamp for the below light. I had to slightly trim the tab on the back of the light and I had to reverse direction the clamp head (b/c the tightening screw came in contact with the size 48cm brake cable- but the end result is flawless).

Portland Design Works Danger Zone Tail Light: Sports & Outdoors- check out reviews at amazon- super bright.


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## foofighter (Dec 19, 2008)

This works great on aero seatpost or chainstays









Serfas 2011


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## brucew (Jun 3, 2006)

The DiNotte 300R taillight comes with an aero seatpost mount right in the box.


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## ClancyO (Mar 20, 2011)

brucew said:


> The DiNotte 300R taillight comes with an aero seatpost mount right in the box.


AND a $200 price tag!! Ouch!


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## fizbey (Apr 25, 2006)

*tail light for aero seatpost*

I have a 32mm deep aero post on a 2012 Orbea Orca. I purchased a Sigma Micro and I'm happy to share it works for my post. It will mount on either side but not on the trailing edge due to the profile of the small mounting bracket. The nice thing is it comes with 2 separate velcro straps. The longer one is 11.5 inches however it stretches to approx 
14". The small strap is just under 6" but does not stretch. It has two light modes and a large button for easy turn on and off.


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## Love Commander (Aug 20, 2009)

Do you still have your 300R? You could try Dinotte's seatpost mount for their older series lights. It would be kinda kludgey, but would be quick to put on/take off.


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## JGengineer (Dec 9, 2013)

koherston said:


> I am having a difficult time finding a rear light that will fit the aero seatpost on my Cervelo S3. I even tried the DiNotte 300R but their aero clamp is just a tad too small (the screw rubs/gouges the carbon post). Has anyone found a good solution (that doesn't involve putting it on a helmet or seatbag--I'm specifically looking for a seatpost solution)?


Just get rectangular magnets from amazon and sugru - works like a dream

Attach anything to anything with sugru + magnets! - YouTube


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## Typetwelve (Jul 1, 2012)

I have a Cateye Rapid 3:

Cateye Rapid 3 Rear LED Cycle Light Sports & Leisure | ProBikeKit.com

It has a funky retention strap that works well but I'm sure you could remove it and use regular tie wraps...I'm pretty confident you could get it to hold on to an aero post just fine. It can also be rotated in either a vertical or horizontal fashion so you don't rub your legs on it.

Little stinker is pretty bright too...

*EDIT*

Just noticed the date on this one...sorry...


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## halien (Dec 8, 2009)

Cycling Victoria is implementing a policy as of June 28 2014 that for races where the road is not closed, a functioning flashing read light must be attached to the seatpost of all bikes.

Given nobody appears to make lights specifically for aero seat posts, it's going to be a big PIA for many without a boring old circular cross section post!

If anyone_ has _found products specifically designed for aero seat posts in the time since this thread began, then I would love to know about them.

If they had said it could be mounted anyhwere rear facing, like helmet, saddle, jersey, or seat stay, then I'd be happy, as it is, I'll be gaffa taping a light to my seatpost.


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## MMsRepBike (Apr 1, 2014)

Serfas Thunderbolt. Fits fine, works great. The eastic bands should stretch around most aero posts, it fits mine just fine.


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## spdntrxi (Jul 25, 2013)

serfas thunderbolt


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## PhillyFan (Jan 30, 2013)

MMsRepBike said:


> Serfas Thunderbolt. Fits fine, works great. The eastic bands should stretch around most aero posts, it fits mine just fine.


Mine too


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## planetrobbi (Dec 21, 2013)

I just cable tied mine to my seat rails , works fine and the curve of the light fits in with the curve of the seat base like its factory

View attachment 295577
View attachment 295578


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## Fireform (Dec 15, 2005)




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## QuiQuaeQuod (Jan 24, 2003)

halien said:


> If they had said it could be mounted anyhwere rear facing, like helmet, saddle, jersey, or seat stay, then I'd be happy, as it is, I'll be gaffa taping a light to my seatpost.
> View attachment 295506


*Years* before someone mentioned duct tape? SHAME! 



Shims can work for such situations as well, to get non-round parts into round(ish) shape. Lay material down on the narrow sides (rubber strips/tire strips/tape, whatever) to build it up to round, then mount as you would normally do. If the light clamp is too small to work on the built up area, zip ties.

I would actually build up the clamp, not the tube, but it's easier to judge how much you need to build things up by laying it out on the tube.


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## merckxman (Jan 23, 2002)

Light & Motion will becoming out with a aero mount solution for their Vis 180, the mount will be available as an option they said.


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## nhluhr (Sep 9, 2010)

Another vote for Serfas Thunderbolt - it works fine on my BH G5 which has a much longer/thinner teardrop shaped post than the S3. It's even narrow so that it doesn't ruin the aesthetic of your bike.


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## AvantDale (Dec 26, 2008)

I have a Thunderbolt for my S2...it'll eventually work itself to one side.

I'm about to give the Giant Numen light a try.


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## Klassikbike (Feb 28, 2014)

I use the Cateye Rapid X one of the most powerfull real lights and at the same time, I heard the lightest rear light on the market.
+ many very cool flashing constant or pulsating options.


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