Is it worth it to purchase a carbon bike for commuting daily 50km. I'm thinking I would be faster and also be able to train on weekends for my first iron man this year. I don't have the funds to purchase two bikes and wondering whether it's better to have just one good bike?

Located in Vancouver Canada

  • 1
    Carbon is always better for everything, no questions asked. The bigger questions are, are you planning to commute on time trial bike or race ironman on commuter bike, and if you're commuting 50 km daily and training on weekends, when do you recover?
    – ojs
    Jan 22, 2020 at 6:05
  • 1
    you'll be able to train just as well with an aluminum frame (assuming the geometry is similar) Jan 22, 2020 at 6:51
  • 4
    what is your budget? It is said that cheap carbon bikes (lower end carbon frame) are often heavier than expensive (high end aluminum frame) aluminum bikes (both bikes being the same price. If your budget is relatively low you can buy an 'entry level' carbon frame which might not be better than the 'high end' alu frame you can buy for the same price. Jan 22, 2020 at 7:04
  • 4
    The presumption that carbon is faster is flawed. Bike fit and rider skill (aerodynamics) makes infinitely more of a difference than weight. If you competing (in a hill climb) and seconds an hour mean a podium or not, then carbon might have a meaningful speed advantage. Other reasons for (and against) carbon are more important in the decision which way to go. Latest trends, with improvements in aluminum frame manufacture are heading towards higher end aluminum bikes as the cost saving in the frame can be put into components.
    – mattnz
    Jan 22, 2020 at 8:19
  • 1
    @DanK to me it sounds like the OP has no idea at all about what they are doing. It's easy to be confident about starting with ironman when you don't know how difficult it is. Yes, I was being sarcastic about the overall bestness of carbon fiber.
    – ojs
    Jan 22, 2020 at 8:56

5 Answers 5


I have a pretty decent alu frame / carbon fork bike, a Scott Speedster Gravel 20. They have a higher-end version with better components and a carbon frame, the Addict Gravel 20.

The price is 3x higher, for a weight saving of about 1.3 kilograms. Probably no more than half of that is the frame, the rest is from the higher spec components.

Plugging some numbers into a calculator gives a saving of several seconds over 50 km of flat ground. Even if the 50 km were a constant 5% gradient up hill, you’d save only a couple of minutes by reducing your bike weight by a kilogram. Keep in mind that at 150 watts average, we’re talking a few minutes shaved off a four hour ride. This is a big deal if you’re a pro — you literally can’t afford not to. But for commuting? I’m not convinced.

Going carbon for the weight savings is only worth it if

  1. Your ride to work is really hilly,
  2. You’ve made sure you have no excess fat left to lose,
  3. You’re willing to optimise all the other components as well, and
  4. You have a lot of money to spend.

Find a bike you like within your budget and don’t worry whether it’s carbon or alloy. Also, make sure to get disc brakes. Rim brakes are shit in a rainy urban environment (I should know; we usually get more than 800 mm/year of rain here).


It depends on your budget and circumstances. A relatively cheap bike for commuting can have a few advantages compared to an expensive time trial bike:

  • Lower maintenance and replacement costs, especially in winter.
  • Less fragile (especially if you compare steel to some high-end carbon components). [Per Weiwen Ng’s comment]
  • Ability to fit wider tires for bad roads, light off-road use, winter etc.
  • Wheels with shallow rims for better cross wind performance.
  • (Hub dynamo powered) lights.
  • Luggage rack in case you want to go shopping or bring stuff to/from work.
  • Less likely to get stolen (and if it gets stolen the financial damage is lower).
  • More relaxed seating position, better for riding in traffic.
  • Better brakes (less true with hydraulic disc brakes on modern time trial bikes).

Of course if your budget is barely large enough for a decent road bike it makes more sense to get that instead of two cheap bikes where neither will be great to race or commute with.

I commute on a 1200€ aluminium cyclocross bike with good, street-legal lights and mostly use the 3000€ carbon road bike with power meter for fun&training only.

  • 3
    I’d add a concern about using a carbon bike as a commuter bike. Carbon is a great material for bike frames (and also for aircraft), but it is sensitive to mishandling. Lock a bike up outdoors, and it is going to get knocked about at some point. This could create a crack in the frame that will eventually propagate and cause a failure. While the same is true of an alloy performance bike, at least that frame is probably cheaper to replace. Come to think of it, this is probably another rationale for a dedicated commuter bike, unless the bike will always be locked indoors.
    – Weiwen Ng
    Jan 22, 2020 at 17:23

It's better to have one good bike, and in your case you'll want to optimize that bike for the Ironman or any triathlon events you'll be doing on your way there. A 'race' bike might not be optimum for commuting but it's doable. Using a commuter bike in an Ironman is going to suck. Just commute on the race bike - you'll be doing lots of miles on it anyway if you are serious about doing the Ironman.

These days carbon frames are ubiquitous and aluminum frames tend to appear on less expensive bikes. Whether you go for carbon or aluminum is going to depend on your budget. I know plenty of people who do Ironman competitions on aluminum bikes so carbon is not a prerequisite.

Of greater concern is bike geometry. You'll want a bike with low 'stack' (vertical distance from bottom bracket axle to top of top tube) to allow fitting aero bars and a leant forward aerodynamic position.

I'd suggest seeking out some triathletes and getting some specific advice. Also look for bike shops that specialize in triathlon gear.


First of all Vancouver is wet. Very wet. Especially if you ride through the winter. This can make it hard to have a single bike to do everything without some serious maintenance to get it race ready. As such, if you went with one bike, I would make sure to budget some money for maintenance (e.g., chains, cables, brake pads bearings). This would make me incline to suggest a slightly less expensive bike which would be aluminum. If also want to 50 km commute year round you will need fenders. Typically aluminum frames will have fender mounts, but some carbon frames will have them as well. That said, fender mounts typically add cost to a carbon frame as they have to bond in aluminum pieces for the threads raising the cost and making it less likely to be found on an inexpensive bike.

All these caveats aside, I commute about 50 km a day and my daily commute bike is carbon. Why? Because I liked the way it pedalled, the fit was good, and it was possible to mount fenders on it. To me the most critical component for performance is not weight, but how the bike responds when pedalled aggressively. Well made carbon frames can can be tuned a bit more in the layup, but this is typically only done well in higher end frames as the layup process is labour intensive and therefore costly. With lower end carbon frames it is a gamble and aluminum is likely a better bet. Frames that pedal responsively, just make you want to ride harder. Frames that feel "dead" make kilometres feel physically longer and for some reason they always make me feel tired.

In terms of aluminum, Hydroforming has been a bit of a game changer lately for tuning the responsiveness of aluminum frames, which is why we are seeing a bit of a revival. In the past aluminum has had a bit of a bad rap due to older aluminum frames which were often too stiff and could feel "dead" compared to a good carbon or steel bike. Now a well sorted aluminum bike can feel very similar to a more expensive carbon bike.

So where does that leave you? Basically, either could work depending on how it was built. If budget is a consideration, you are likely to get better bang for your buck with aluminum.

In terms of choosing a bike, I suggest the following workflow:

  1. Start with a budget;
  2. Determine what features you need for commuting (I recommend fender eyelets, some like panniers, but I am happy with a frame bag, seat bag, or front roll);
  3. Do you have to lock it up outside (if yes, avoid a carbon bike or any bike that looks expensive);
  4. Form a list of possible bikes;
  5. Got to your local bike shop and test ride; and
  6. Choose the one that gives you the biggest smile.

I would suggest avoiding online sales as these can only work when you know exactly what you want. Even then you are not likely to save much as complete bikes in Canada have a extra duty levied against them in addition to PST/HST taxes. Too many people get lured by a slightly better component spec, but most components work fine now so this is a bit of a false alure. Ironman is a long race (I know, I have done one), as long as your shifting is working, you probably won't notice any real performance difference. You will however notice a bike that doesn't fit right or one that you don't like the feel of... this is why test riding is critical.

  • @MichaelHampton Answer completed now. Not sure why it published early, I thought it was saved as a draft.
    – Rider_X
    Jan 24, 2020 at 7:51
  • I'll blame caching then. Jan 24, 2020 at 7:53

Unless you've got a route remarkably free from stoplights, it's difficult to change your commute time, and a slightly faster bike isn't going to do it.

I understand being tight on funds, but I would also regret my "nice" bike getting beat up through the wear and tear of regular commuting. And as @Weiwen mentions, carbon is more sensitive to rough use.

You're going to spend a lot more time commuting over the next year than you will racing in that triathlon. My advice would be to pick a bike that's better optimized for commuting now, and keep your eye out for deals on used tri bikes (which miraculously pop up on Craigslist after every short-course race), or possibly borrow one for the race.

  • A short term solution is to look for bike hire - see if there are any bike rentals available. That could be a rental bike for the commute, or a rental race bike for the ironmans. Over time it may cost more than owning, but in the short term can get you through a hump.
    – Criggie
    Jan 23, 2020 at 2:25

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