How much faster will I be on an Aero road bike compared to my Gravel bike

I own one bike, two sets of wheels. Considering getting an aero road bike. I can maintain 17-18 mph average speed on the gravel with 42mm slick road tyres on 50 mile rides.
As I have never owned or ridden a pure road bike just curious as I love riding fast on the very quiet lanes of cheshire.
Will I notice a big difference.
Anywhere do demo hi end road bikes I can hire?.

Probably a mph or 2, but only at higher speeds, I doubt aero comes into much below 15-20mph.

Don’t forget to shave your legs for that 0.5% aero increase.

For the same course and power, my top of the range tcr with 42 mm wheels is roughly 0.5 mph faster than my giant defy. That’s on a 30 mile route with 3000 ft of climbing. I expect it would be more on a flat route

Appreciate a defy isn’t a gravel bike, but when I compare speeds between the defy and my other gravel bike with slicks its usually 1 mph faster..although probably not for similar power.

So in conclusion, gravel bike to top end roadie, id say between 1-2 mph difference.

It’ll be a little quicker, but 1mph 2mph its impossible to say without exact back to back testing. But it deffinetly will feel faster, lighter and more responsive. If you think that adds up to more fun and you can afford a new bike then go for it.

The aero element of a bike is well into the marginal gains world – you are talking a handful of seconds every hour kind of gains. Way way too small to ‘feel’ as you ride along.

The road bike vs repurposed gravel bike – that’ll be more about the weight and the position it puts you in. Are you prepared to adopted a more aero riding position? Is your current position more sat upright at the moment. No offence to mtbers but a lot of them when they buy a road bike plonk themselves on it like a sack of spuds. Have you considered playing with your position on your current bike a bit to see what that does – a slightly longer stem or swap a spacer from below to on top of your step for example.

Other ways that road bikes feel faster (and are I guess) is the rolling resistance of the tyres and the weight of the wheels/tyres combo. The weight helps with a acceleration out of corners. The rolling resistance helps maintaining a speed once up and running. There is also a perceived element to this – a narrower tyre blow up to a higher psi gives you a more harsh ride that can ‘feel’ faster but is maybe not as much as you think.

For context comparing my old school ti CX bike fully guarded up with 35mm tyres then flipping to my lighter summer road bike with a super stiff carbon frame with 25mm rubber it feels a load faster but Strava says my average speed only goes up by about 2mph and that is on average with faster, dryer roads too.

Unless you’re time trialling, the useful question is not “how much faster will I be?” so much as “how much faster will I feel?”

If you ask me, 42mm is way too wide to feel fast on tarmac. Get some nice supple 28s on there and you’ll feel a lot faster. And IME when you feel faster you tend to rag yourself a bit more, and that means you turn out to be faster. Much more so than shaving a wee bit off with some aero tube profiles.

Well going off Strava my CX rides tend to average about 14-15mph and my road rides about 17-18mph.

But as much of that is about terrain – on the gravel bike I do off road trails, more hills, tiny backcountry lanes with gravel/grass up the middle so it’s automatically slower. Also the road bike is quite racey and tends to encourage faster riding, pushing it on the hills.

I’d have to do comparable road loops on both bikes to get a feel for it.

And IME when you feel faster you tend to rag yourself a bit more, and that means you turn out to be faster.

+1

It depends. The aero frame and forks in themselves will make a very slight difference, but if you set it up with aero wheels and more importantly a more aggressive positions, and have a cleaner drivetrain etc., it will all add up.

1-2mph I would guess based on my commuter vs road bike (I reckon I’d only be looking at upgrading the road bike to something more aero if I was doing some serious racing, and getting near but not quite at the pointy end, and had the money to walk away from a crash writing off £5k of frame, forks and wheels with a smile on my face. Not that I object to anyone else getting a fast bike and not racing it of course! I don’t race my road bike really.).

If possible, clip on aero bars, aero helmet and a skin suit would make more difference – but now might not be the time to learn to use clip ons.

Biggest least aerodynamic thing on the bike is you. I see plenty of aero bikes with huge amounts of spacers under the stem and the the stem flipped to give some rise.

Cheers

I doubt aero comes into much below 15-20mph.

Which is dry easily achieved as soon as you through the slightest headwind into the equation.

For the same course and power, my top of the range tcr with 42 mm wheels is roughly 0.5 mph faster than my giant defy.

TBF the TCR is about as aero as a brick

I have riden the same route on a gravel bike with 32mm slicks and then a road bike (not especially aero) with 30mm slicks. The road bike was 3mph avg faster. Its 2.5kg lighter than the gravel bike and the road bike position is less upright. So, in my experience the difference is big. If riding pan flat routes then less of a difference, but who does that?

Some really good answers have been posted and I agree with pretty much all. In a wind tunnel an aero bike will show gains compared to your gravel bike. If I compare me riding my winter bike compared to me being on my Bianchi XR4, speed on my Bianchi is way faster! The bike is lighter, my position is much more aero and let’s be honest I feel encouraged to ride faster. Is this the bike? Kinda, but it’s mostly the way the bike makes me feel when I ride it.
If you want to ride fast, get an aero bike.

One thing to add, aero bikes can be uncomfortable in terms of rider position and harsh ride, unless you’re comfy you probably won’t be going faster for long.
If you’ve not got a bike in mind, I can whole heartedly recommend an Oltre XR4. Ride quality is exceptional.

Thanks so much, really useful advise and comments.
The reason I said Aero bike, tbh is all about the look. I like the deep rims, the clean lines.
I do tend to ride on the drops so quite low.
I have tried 32mm continental Gatorskins but now ride 42mm conti contact speed, the bigger volume has a bigger circumference and more comfort and tbh are faster than the 32 looking at the improved PR’s on strava

Agree with Leeroy, my Aeroad is faster than my Domane. But it’s lower front, has an aero cockpit, a lot lighter, 65mm wheels and fast tyres.
My Domane when set up with wide tyres (32mm) feels very sluggish compared to the Aeroad. I’ve got rid of the power meter on the Aeroad otherwise I’d be able to do a comparison. Strangely the Aeroad climbs really well, it’s not just the flat where there’s a difference.
My Aeroad is comfortable though and so was my Madone. But I’m used to aggressive riding positions so that may help.

Will I notice a big difference.

Do you notice a big difference between riding along at 18mph and riding along at 19mph?

The road bike would feel better to ride to me and would be the bike I would choose, I even ride a bike that is closer to a road bike than a gravel bike for gravel roads. It does feel faster, better to accelerate, better uphill, better to steer and move around but in reality the actually difference in average speed is going to be minimal.

My proper road bike is usually 33-35kph on my local 60k loop and my gravel bike with 40mm tyres and a more upright position is 29-31kph over the same terrain. A proper TT bike or even one a road bike with proper aero wheels and TT bars would probably gain you another 2-3Kph. So in total, I recon 7kph or 5mph is possible on a flattish route.

I have tried 32mm continental Gatorskins but now ride 42mm conti contact speed, the bigger volume has a bigger circumference and more comfort and tbh are faster than the 32 looking at the improved PR’s on strava

Gatorskins are a good, tough tyre. But not the fastest rolling. Plenty of more supple tyres that size and smaller that will roll noticeably faster, before you start worrying about aero. Or particularly if you’re worrying about Aero too. And you don’t have to contort yourself, just accept the odd puncture here or there.

I bought a TT bike for doing triathlons a couple of years ago, believing that full aero would instantly make me faster, and in truth it did…for the 10miles or so I could hold a good position comfortably.

I’d say if you want to go aero you have to work on the whole package – bike and rider.

My CX bike has 38mm Schwalbe G one smooth tiny knobbly tyres and I cruise 16-18 mph Up to miles. Great for training on.

My Defy is 2 mph faster and quicker to spin up. I usually knock 34 minutes off my ride time and comfy on century ride loops.

My TCR rim brake is another 2-5 miles faster but a bit stiffer.

My Disc TCR is between the Defy and TCR rim brake.

Aero position is more important to me. Going down hill, the TCR ride position allows me to overtake and get faster. It’s like riding on the drops of my CX. The weight makes a slight difference to me.

Personally I need drop 20 kgs 😫 before any upgrades for a year!

I can maintain 17-18 mph average speed on the gravel with 42mm slick road tyres on 50 mile rides.

That must be a lot smoother gravel than I ride on!

😉

On a 90min ride I can just about maintain 17mph on the gravel bike with a group of roadies and minimal drafting, not none, but I can do most of it on the front effectively solo.

On the (round tubed) road bike it’s harder to say, as I don’t do such short rides on it, and more often in groups. I did 35 miles on Saturday at an average of 17.3mph solo, but can comfortably hold 20-21mph on the flat sections and did one flat group ride at 22.5mph last year, but that was hanging on for dear life whilst others did the work.

So probably about 1.5mph at those sorts of speeds between ~38mm knoblies and box section rims, and a road bike with standard wheels.

Full on aero bikes claim about 0.5mph on top of that.

The biggest difference is downhillthough, the road bike picks up speed quicker, has a higher terminal velocity and slicks corner much quicker thank nobly tyres.

Have a play with a Strava segment or two at https://mywindsock.com/my/ and configure typical power and CdA.

At ~270W on a flat route, you could easily be talking ~3mph.

But you could make some gains on your gravel bike by fitting some nice tyres that merge nicely with the rim walls (especially the leading edge front) such as 25/28mm GP5000 (depends on internal rim width of wheels), lowering and extending the stem/bars if feasible etc.

What are you going to do with the 5% you save? Get home more quickly, travel a bit further, or expend less effort?

I’ve got all sorts of bikes and the only time it matters what I ride is when I’m with others. If I take the gravel bike and everyone else is on 25s then I’m in for 30W more than them.

When I’m alone it doesn’t ‘matter’ beyond aesthetics.. which may be the most important reason of all!

tbh is all about the look

So it doesn’t actually matter how fast you are going, then?

Surely this is just a trailer for some new GCN video?

I can maintain 17-18 mph average speed on the gravel with 42mm slick road tyres on 50 mile rides.

That must be a lot smoother gravel than I ride on!

I was gonna suggest this thread was an excuse for a humblebrag.

Can’t help with the question at hand myself, but do please let us know once you’ve found out OP.

On group rides my gravel bike with 30mm slicks I can keep up with the group easy enough and can still ride at the front on hills but hide at the back on the flat, with 37mm G one allrounds I can keep up but its tough. On my roadbike with 25mm slicks and more aggressive position I can happily ride on the front all/for a lot of the ride.

For fun solo riding I’ve never understood aero, but I understand Strava is king for some.

Some things feel faster and are faster (nice tyres, stiffer aero wheels I would guess), some feel faster but aren’t (stiffness, light weight). I just get the lightest stuff
I can afford that feels nice to ride

For fun solo riding I’ve never understood aero, but I understand Strava is king for some.

That sounds a bit passive-aggressive, as if you think people on aero bikes are seeking to impress others on social media.

I like going fast, and I use Strava, but here’s the thing: I liked going fast BEFORE Strava was invented. I just like going fast in itself. I also like covering long distances, which takes less time if you go faster. Or to put it another way I can go further in the same amount of time.

. I just like going fast in itself.

Me too, but buying speed isn’t the same for me, I just don’t get it (I would if I raced obvs).

If I can get 2m off a known loop through training, that’s satisfying, if it was down to £700 wheels, I’d rather have the £700, plenty better things to spend it on (for me).

And anyways as said above, aero is for most of us about position above all else.

Yeah yoga, slam that stem and fit narrower bars. I’ve just gone from aero bike to steel bike and I doubt I’ll notice much difference if I analyse speed, but the steel bike is the right shape for me and it’s prettier so it’s obviously faster.

The thing is that a full aero weapon really only benefits you on the flat vs a lighter more ‘standard’ road bike with decent 25-28mm tyres, maybe a ~36mm deep ‘semi-aero’ front rim will give some measure of aero benefit on the flat still. Things might have moved on but last time I looked you generally paid a 2-300g penalty for an aero frame, and depending on the cost, almost as much again for a deeper section aero wheelset.

Getting up climbs say 0.5mph faster on a more efficient, lighter machine will benefit your average speed disproportionately, and you might still sneak an extra 1mph on the flat for the right position/tyres/wheels vs your gravel machine.

All of that aside though you’ll almost always see more benefit from tuning up the engine (time and lifestyle allowing)…

If you’ve not listened in a while or never Cycling Tips podcast has carved out the Nerd Alert bit as a standalone with the obvious title of Nerd Alert….31 Mar Does Bike Weight Really Matter has some interesting input on aero’ gains best bits from a guy working with EF ….worth a listen (no relation)

my experience is just a bit slower but quite a bit more tiring

My commute is a couple of mph average slower on the CX nail than the swish new road bike. CX is on 32mm tyres roadie on 25mm.

@rOcKeTdOg crazy-legs is probably 70kg soaking wet (we met on a Pootle) and he’s damn fast off-road on a gravel/CX bike (from the same Pootle).

Me too, but buying speed isn’t the same for me, I just don’t get it (I would if I raced obvs).

I’m always a bit suspicious of people who say this. If buying speed was a problem, I’d only have one cheap, heavy singlespeed for everything. I’m quite happy to buy speed for fun, and it’s a mental exercise as much as a financial one (i.e. finding effective ways to go faster, getting the right compromise between all the things you’ll want that bike to do), hence this thread.

The thing is that a full aero weapon really only benefits you on the flat vs a lighter more ‘standard’ road bike with decent 25-28mm tyres, maybe a ~36mm deep ‘semi-aero’ front rim will give some measure of aero benefit on the flat still. Things might have moved on but last time I looked you generally paid a 2-300g penalty for an aero frame, and depending on the cost, almost as much again for a deeper section aero wheelset.

Getting up climbs say 0.5mph faster on a more efficient, lighter machine will benefit your average speed disproportionately

The 90’s called, they want their physics-fail back.

Let’s say the average lightweight bike is 16lb (yes you can go lighter, but it probably means spending more than a small hatchback and involves compromises. And lets say a disk braked aero bike weighs about 20lb.

No Peleton magazone likes to geek out on this stuff and put a load of frames through a wind tunnel independently.

That’s about 55W at 30mph (scaling to a more normal 20mph on the flat that’s 25W so 20*20/30*30 * 55 = 25).

Scaling to 12mph (a moderate climb) about 10W (25* 12*12/20*20)

Throwing some numbers into this calculator, 70kg rider, 16lb bike , 12mph, a 200m elevation climb in 10 minutes means doing 252W against gravity, 47 against air and 20 against the tyres and drivechain. Total 319W.

http://www.u.arizona.edu/~sandiway/bike/climb.html

Adding 4lb to make it a 20lb bike adds 6W.

The 4lb heavier disk braked aero bike, at 12mph is still ahead by about 4W.

You would need a seriously heavy aero bike for the lighter bike to offer any improvement. aero really does trump just about everything, even uphill.

Incidentally according to that calculator the difference between hoods and drops is also about 6w, and between the drops and a full on tuck is another 10W at 12mph.

So actually whilst sorting your position is free, a new bike saves about the same. And just like buying lightweight bits it is possible to have a shit before a ride and buy weight weenie parts, it’s possible to adopt a lower position and buy an aero bike.