How much faster is a new bike going to be?

I posted earlier about looking into a new bike vs upgrading my current one. That said, I find it very hard to say that I’m not happy with my current bike. It’s a 2018 Giant Defy and it’s my first road bike.

That said, I like going fast and my question is, how much faster would I be on a new bike, say the Giant TCR? I know it’s a weird question that can’t really be quantified, but is there really a measurable difference between a $1,200 bike and a $2,500 bike?

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Personally, I think fitness trumps all. I have an entry level Allez and did a solo century averaging 19mph, which I think is pretty good. I’ve even averaged 18mph for a couple of hours on my CX bike. I’ve never ridden anything higher end, but I have a hard time believing I could get much more speed for myself out of bike or wheel upgrades


GCN did a series of tests on this question, here’s one. Super Bike Vs. Mid-Range Bike | What Really Is The Difference? - YouTube

Not quite scientific research, but interesting.

Depends on the rider for sure though. If you make a lot of power, then a faster, stiffer bike will deliver that to the wheels better. If you’re shifting a lot to maintain smooth cadence and power over terrain, then the better shifting the bike the faster you’ll average.

When I upgraded from a 1985 Miele steel 2x7 road bike to a just 10 year old carbon tri bike, it was worth like 5-7 mph. Difference between a 1,200 bike and a 2,500 bike is less than that, but 2,500 does seem to be where the real performance bikes start.


A brand new $2500 road bike vs a brand new $1200 bike, both with the same tires, is probably at most 5% faster in general, and 10% faster in its specialty (hills if it is light, flats if it’s aero). These percentages are then half as big for the next higher 2x price category and another half again for 4x prices. This is just how I have it simplified in my mind and is not empirical at all. If you race and have already picked the low hanging fruit for fitness and bike fit gains then these marginal gains might matter to you. Everything else is psychological which is not to say that your mental state is not important!


I think the biggest difference is in body position: the Defy is an endurance road bike, the TCR has a racier geometry where you sit lower, which, in turn, causes lower drag. Given that drag increases with the cube of the velocity, this makes an ever larger difference the faster you go. However, you can do anything on a modern endurance geometry road bike, even race.

That being said, I’d rather suggest you update your legs first, i. e. get a power meter and start training. That’ll make a much bigger difference than anything.


Just to add on because I think this is interesting. I rode a loop a few weeks ago on my Allez, avg 212w and got the KOM on a 13ish mile loop. Around the same time, a guy I know rode the same loop on his carbon race bike with aero wheels, also averaged 212w, finished 20 seconds slower than I did, so conditions were roughly the same, maybe NP slightly different but just an example that entry level can be just fine and not a lot worse than higher end


I fly on my giant defy. Don’t blame the bike for your shortcomings. I’m seriously not being a jerk. I’m being serious. I busted my tail on TR this year, with over 130 riding hours. I have no issues flying down the road now. Climbing is enjoyable


I agree that fitness trumps almost all. I have been riding my road bike and typically avg around 18.5 mph with 105 components. I am on vacation at my parents and riding my old cannondale hybrid with sora components and did 18 mph today on an one hour ride. I am really enjoying riding my hybrid while I have been here.


It will definitely help you to improve your overall fitness but I will not make you faster. You need training to push those pedals to your limits.

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About 25% of the aero drag comes from the bike, and 75% of the rider. So a “faster” bike doesn’t really add all that much to your speed.

Some bikes are faster than others for 3 main reasons:

  1. More aggressive positioning. A lower more stretched out position reduces aero drag of the rider. But not everyone can comfortably hold more aggressive positions for long periods of time. And you can probably achieve a similar position on the Defy by slamming the stem.
  2. Wheels. Wheels are an important part of the aero equation, as they are the first part of the bike to hit the wind, and the top of the wheels are moving at double your actual speed. Mid to deep section wheels can save quite a few watts. While the stock wheels with a $2500 bike will probably be lighter than those at $1200, they will still be shallow section wheels. You would probably need to go up another price point again to get aero wheels stock with the bike.
  3. Aerodynamically designed frame. After allowing for the performance of the wheels, an aero frame offers only modest speed gains.

My advice?? Keep the Defy, slam the stem (gradually and progressively), and put $1500 towards a good set of aero wheels to put on the Defy.

And even if you do want to get a new bike (hey, the siren song of N+1 is always strong), start with slamming the stem of your Defy now - it will at least start your body adapting to a new position.


There are 2 questions here.

  1. Will changing my bike make me faster?
  2. Will a more expensive bike be faster than a less expensive bike?

On 1:
The Defy is a good bike, but it’s an endurance bike aimed at long distance comfort over speed. If speed, especially over shorter distances is important to you, then there are many bikes that are more suited to that. they will put you in a more aggressive position, they may be more aero and/or lighter, and they may be more nimble. It’s not all good - they might also be less forgiving, and the aggressive position might actually be difficult for you to sustain without pain.

On 2:
If you stay within the same category of bike, then once you are above a certain point, spending more gets only marginal improvements. A Dura Ace version of a bike is only going to be marginally faster than a 105 version (and probably from the wheels and other components rather than the groupset). It will be lighter though.

To conclude - if you spend 2.5k on the best Defy you can get, you won’t go much faster. If you buy a TCR (or equivalent), then no matter what you spend, you are likely to go a bit faster because of the position.

However, as everyone else has said, the most important thing that determines whether you go fast is the rider. Alaphilippe would still fly on my bike (assuming it would fit him!), I still be quite slow on his.


A new bike alone isn’t going to make you fast. That comes from lots of training, but a good bike can help you enjoy the riding 100x more. One important point is the psychological factor of how much you look at your bike leaning against the wall in your garage and think: “urrgh, piece of crap” or “You look gorgeous, let’s go out and have some fun”. A more expensive bike can be an utter pleasure to ride vs a cheap one. A good frame, decent deep wheels, good groupset all combine to make your riding pleasurable and fun and maybe fast.

Ask yourself some questions about what sort of riding you want to do and be realistic about how good you are. If you’re 100Kg with an FTP of 200W and do 10 mile casual rides on a Sunday afternoon then your needs are different than if you are 75Kg, FTP of 330W and do road racing.

Go buy a new bike for sure, but the right one, with the right expectations.


A lot of the time it won’t make that much difference. I have 2 road bikes, the first is a 2018 Giant propel so deep carbon wheels, 25mm tyres and aero everything. My other bike is a Kinesis titanium with mudguards, 30mm tyres on pretty traditional wheels, round tubes etc, My position on both bikes is nearly identical, both have Pioneer power meters although the Kinesis is only single sided.

My endurance rides are generally around the 210-220W NP, the difference in average speed between the 2 bikes is rarely more than 1kph.


Also the question is how is your position on your defy? Have you got a fit to make sure you are aero? I know when I was doing tris in my road bike I got a fit to get more aero while doing tris with my aero bars but also had an aero position on my road position. I have a trek emonda alr and while it is not real aggressive I am ok with that as I am in a good position and aero for the frame type.

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+1 for this. I just went through a similar thing. I was on a Trek Domane with Tiagra components. Over the course of two years, I slammed the stem, bought some HED Jet 6+ deep section wheels, and then finally caved and bought a full-on aero race bike with Di2. To sum up the three main differences between the new bike and the original Domane:

  1. The deep section wheels make a big, noticeable, quantifiable difference (assuming you don’t live in the alps or something). This applies both to the Domane and the race bike.
  2. The aero frame of the race bike is noticeably faster. It’s hard to say how much of this is the more aggressive position and how much is the aero frame, but either way, the difference between the frames is less than the difference between the wheels. Put another way, putting aero wheels on my endurance bike made a bigger difference than upgrading from endurance bike to aero bike.
  3. Di2 versus Tiagra is a nice luxury item, but doesn’t make you faster.

So having been through this recently, I can say that I love my new bike and I am glad I bought it. However, if I were trying to get faster on a budget I’d recommend buying deep section wheels (highly recommend the HEDs FWIW) and slamming the stem. The mystique of a pro-level aero race bike is super tempting, I know, but it really doesn’t make that much difference.

But new bikes are also very fun :slight_smile:


This reminds me of a story I heard years ago. A guy walked into a bike shop and asked to see the fastest bikes. The owner brought out 2 bikes to the parking lot, and gave them a push. They both rolled a little bit, then fell over. He turned to he customer and said “Its not the bike”.


This largely supports what others have already posted but…

If what you’re really truly chasing is going faster then there are a number of optimizations you should make before you buy a new frame (more aggressive position, aero wheels, aero road helmet, tight fitting kit or skin suit) - all of these things will impact your aerodyanmic drag more than the frame (for the majority of bikes…obviously in some extreme cases this isn’t true)

If you want to buy a new bike because yours is a little banged up and you want the new hotness then by all means do so - there are a lot of great reasons to buy a new bike - including going faster. But until you’ve plucked the low hanging fruit of aerodynamic and weight gains buying a new bike is not your best bet

To answer the question in the title of the thread: It depends on the rider and the bike


If you’ve never had a pro fit, a faster new bike might be slower.


Thanks for all your replies!

Just to be clear, I’m not looking to pay for speed although I don’t think there’s anything wrong with that. If you have the money then use it. Rather, I’m just wondering how much faster a dedicated aero road bike would be compared to an endurance road bike, which was partially answered by the post with the GCN links (watched them, very helpful).

I agree with everyone here, I will probably be faster by getting a more aggressive position than by spending money.


Cost/benefit analysis when it comes to hobbies is a hiding to nothing in my experience, over many years and many hobbies.