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I am hoping to buy one of these in the next few weeks:

Specialized Roubaix SL4 Expert Disc Di2 2014 Road Bike

But I will be using it for commuting and need some luggage so I need to fit a pannier rack (I'm going to ignore all the shouts of horror about using this bike for commuting or putting a rack on it).

Initially I thought that this was not possible and I was looking at getting a custom Titanium frame made with the same components. I have now found a couple of options though.

There is the Tubus set of pannier racks. I have used a Tubus rack before on a bike with no eyelets and it seemed to work very well. If I use the Tubus Clamp Set For Seat Stay Mounting and the Tubus Adapter Set For QR-Axle Mounting I think that'll work won't it? I am unsure if the rack will clear the disc brakes though...

There is also the Axiom set of racks as shown in the video. They specifically make a rack for road bikes with disc brakes which sounds very promising. I can't see how the rack will attach to the frame at the top with no eyelets and no caliper brakes. I could use the Tubus Clamp set though (which I have on my current bike)

So, Will mounting this to my bike damage the carbon frame? Any recommendations about which rack / mounting system I should go for?

Thanks

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I think you have to be careful when mounting extra onto carbon frames - they're often designed with very specific loads in mind, and might not be very strong in other directions. On the other hand, it might work fine. – 7thGalaxy Feb 26 '14 at 10:13
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Carbon is especially problematic with clamping forces, so be careful if you need any clamps on frame tubes. – arne Feb 26 '14 at 11:08
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A Carbon Fiber Roubaix Di2 for commuting is insane, unless by commuting you mean participating in the Paris-Roubaix. Generally, race bikes don't take well to racks, either due to geometry or just not having the proper mounts and strength in the right places (especially with carbon). – Batman Feb 26 '14 at 13:24
    
This is an old question but in the end I went for a titanium frame Enigma Etape with Di2 and Hydro Disc brakes. Has all the mounts for a rack but great on 100 mile rides as well when I strip it down. – Roaders Mar 16 at 9:52
up vote 8 down vote accepted

I would recommend getting a second bike for commuting. The Specialized Roubaix is a racing machine. It would also be foolish to leave it locked outside a shop (in case you considered doing that).

Most likely you will void the warranty by using clamps on seat stays. To get that low weight, carbon frames are strong only in certain directions and may be relatively weak in others.

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Why not use a Roubaix for commuting? Seriously I am wondering why people are so against this. I never leave the bike locked up outside, it is locked up in the underground car park in my building. Over the year I commute around 6,000 miles. I probably do less than 500 weekend miles so there is no point having a nice bike for the weekend. If I have a nice bike I want to use it and enjoy it. The main impetus for change was getting disc brakes, I am fed up with mini cabs pulling out in front in the wet and my brakes not working! – Roaders Feb 26 '14 at 16:20
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I would just like to point out that you could have a "nice bike" that also has a steel/aluminum/titanium frame. Those two criteria are not mutually exclusive. Buy a nice frame that's designed to accomodate racks, and go crazy on the rest of the components if you want. Surly makes a few quality frames that support racks, disc brakes, and basic road bike geometry. There are plenty of other manufacturers as well. – Kibbee Feb 26 '14 at 16:39
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Another option that I am considering is a custom made Titanium frame with the same component set on. I want the hydraulic brakes and the electronic gears. This is pretty much the only bike off the shelf that has them. If I can't get a good pannier rack solution for the Carbon bike then I will go with the Titanium. At the moment I am weighing up the options. – Roaders Feb 26 '14 at 16:57
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The geometry isn't suited for using panniers or a rack period. Commuting destroys bikes with road salt, water, snow, stuff kicked up from cars, etc. along with the occasional get hit by a car (which a carbon fiber Roubaix will likely not survive), so you don't want to run expensive components unless you're Bill Gates. The theft issue is also a (very) big one which people don't really realize until they've had a bike or two stolen. And I can almost guarantee in London, a Roubaix (especially a high end one) will get stolen pretty quickly. – Batman Feb 26 '14 at 21:24
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This is the most important part of this answer: "Carbon frames are strong only in certain directions and may be relatively weak in others." Theft is a secondary concern, albeit a real one. The lateral forces generated by a rack with panniers will likely fatigue the carbon leading to catastrophic failure. Don't put racks on this bike. It'd be easier and less disappointing to just pull money out of your wallet and tear it in half. – jimirings Feb 27 '14 at 1:53

Cool bike but that is a race bike. Consider a bike that is designed for a load.

Look at the seat stay on the Roubaix. That bike is not designed to take a load behind the seat. Putting a rack on Roubaix is like putting a trailer hitch on a Ferrari - it has the horsepower but it was not designed for the load.
enter image description here

If you are set on a race bike for commuting then consider a front rack. Front fork is more beefy and can be replaced. This is carbon fork with eyelets.
enter image description here
With panniers. I know you are looking for a faster bike but I have carried a case of wine on that bike many times and up front and it rides fine. A benefit of up front is you don't have the weight swinging behind you when you accelerate. Down side is with bags attached it is hard to ride no hands. SpecializedBasicCyclocross

It is hard to find a bike with eyelets that is not a full touring bike. I also have a full touring bike (Vaya) and loaded it is great but with a light load it is stiff. But you can find some faster bikes that are designed for light racks. This is a titanium La Cruz. Notice there are 4 eyelets. LaCruz

Four points of contact makes a world of difference. Not only is the Roubaix not designed for it but even with a light load the rack will swing.

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Not editing the question as one of the moderators feels I edit too much. Off road you see bags attached directly to the bike and as much weight in the middle as possible. Part of that is clearance but it is also more stable. salsacycles.com/culture/… – Paparazzi Oct 29 '14 at 14:03
    
Moot has options such as DI2 routing and rack eyelets. And it is a bike designed to take a load. moots.com/our-bike/cross/psychlo-x/options – Paparazzi Nov 14 '14 at 14:16

You could change out the carbon seat post for an alloy seat post, to negate the issues of clamping on carbon and use a beam rack + bag such as a Topeak RX Beam Rack with various compatible Topeak bags.

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If you've the cash to buy a nice bike and you get to ride it on the weekdays then good on you... no reason not to.

For racks, look for the ones that are attached to the wheel axle dropouts and brake bridge if exist, else get one of those seat clamps with rack mounting holes, like these:

enter image description here from http://www.charliethebikemonger.com/ekmps/shops/bikemonger/images/salsa-post-lock-rack-mount-for-seatposts-3818-p.jpg

Carbon structures are never designed to be "just enough". Like any engineered objects they're designed for the worst case (i.e. check you don't exceed weight limit body weight + luggage) and then have a margin built in (e.g. 50% for airplanes). I wouldn't assume you'll carry a lot on a commute and if you go for a rear rack attached to the drop out (bulk of the weight transferred straight to the rear wheel) and the seat clamp (load negligible compared to your body weight) then I can't imagine you'll have any problem (other than people looking at you funny).

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Nice to know that I'm not the only one considering using a Specialized Roubaix Pro (ultra) for commuting. I just ordered a set of SL-R780 rapid-fire shifters, brake leavers and a flat handlebar.

Granted mine has caliper brakes, so I'm going to be using the Axiom Streamliner. It goes through the rear skewer where most of the load is held.

Here's a link: Axiom Streamliner DLX: http://www.amazon.com/gp/product/B0025UCXEO/ref=ox_sc_mini_detail?ie=UTF8&psc=1&smid=

From an engineering perspective, the caliper does in fact put load on the frame each time you hit the rear brake. So having we're not talking about exerting a huge amount of weight. In my mind, the trick is to ensure that the rack is level so that the weight distribution is even.

I tried a rack that simply attaches to the seat post and the problem with it is that it tends to have a bounce in it. I need a pannier to stow away my laptop and work clothes.

Good luck with your commutes. I'll post a picture as soon as my Streamliner arrives. :)

Cheers!

Imran.

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Hello Imran. Having read your answer, the only part that seems to directly answer the question is "In my mind, the trick is to ensure that the rack is level so that the weight distribution is even.". Could you please expand on that and clean up some of the irrelevent details. – Vorac Mar 16 at 11:20
    
Welcome to Bicycles SE. We're looking for answers with specific details. Please edit your post so it answers the primary question which is "Will a rack damage my carbon frame/how do I mount a rack on a carbon frame? A rambling answer like this is likely to get downvoted, flagged for moderator intervention, and possibly deleted. – Gary.Ray Mar 16 at 17:15

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