Having no experience of CX bikes at all, and contemplating getting one, how fast will a CX bike be on the road in comparison to a normal road bike… I’m talking a like for like here… Spend £1k on either road bike, or CX bike, same gearing, frame material etc… I accept the CX bike is likely to be 2-3lb heavier, given a stronger frame, fork, wheels and brakes, but what sort of difference would I notice?

Obviously, I know knobbly tyres would slow it down, but I’m talking even putting a set of 25c slicks on a CX bike for road use… How much slower would it actually be than the road bike for a given effort?

A bit.

Too many variables to quantify it but a heavier bike will always be harder to get to the top of a climb. On a long ride, that can add up.

Cheers druidh, the weight was about the only thing I was thinking would make the difference at my sort of level anyway. Though I also accept that a CX bike would probably be slightly less compliant also, and the geometry a touch lazier.

I know there’s a lot of variables, but remove as many as you possibly can think of that can be neutralised. Same brand bike, same running gear, same contact points etc…

The tires will make the most difference surely. Aren’t most CX bikes slightly less stretched out in terms of geometry than road bikes – meaning you won’t be able to get as low down/aero which might make a reasonable difference especially if it’s windy.

Impossible to quantify though really unless you’ve tested it with every variable the same apart from the frame.

Even wheels will make a slight difference. Then you’ve got aerodynamics. Seriously, you’re never going to come up with an accurate number. I’d say 5-10% more effort, maybe???

The tires will make the most difference surely.

A given, but forget the tyres for now… If I got a CX bike (to ride a bit of winter CX, commute, and some road rides) I would stick 25c slicks on it for road use negating any tyre differences.

Calculations I’ve seen say on the flat the difference is neglible for amounts under 10% of rider plus bike weight.

For climbing you would roughly be talking about an equivalent % of energy loss (more watts required) as the % extra weight. So a fat 100kg rider and bike = 1% extra energy for a kg.

[back_of_fag_packet]So 1 kg = 16 meters or 3.6 seconds every mile of climbing? [/back_of_fag_packet]

Sounds about right? Oh and rotating weight i.e. rims & tyres are most important cos they travel furthest.

Compare that to a slight headwind for perspective.

Not scientific but I comute now on a cx bike with light road wheels and rims( I have a different set for off road) and I am getting to work the same time as I was on a full fledge road bike. I don’t feel any slower than I was on my road bike and I use the cx bike for the ocasional bunch ride without any issues.

If I got a CX bike (to ride a bit of winter CX, commute, and some road rides) I would stick 25c slicks on it for road use negating any tyre differences

I did just that.In non scientific research, I can conclude that a CX bike can go like the clappers!
(only ridden mtb for years) 😀

It will feel slower if you have a decent road bike to compare it against. Just the same a cheap road bike will be and feel slower than a very top end one.
You can ride them with groups no problem, you’ll probably not notice the little extra effort you are putting in

Cross bikes aren’t heavy, they’re not reinforced road bikes! and some of the components are lighter.

They usually have slacker angles and longer chainstays so climbing feels slower. If I jump from my TCR Advanced SL to my race cross bike the difference is immense.

6.2%

From the same scientists that make Make Yourself Younger/Thinner/Bigger/Longer adverts

Had a demo on a Tricross a couple of years ago when the “fad” was at it’s height and decided to stick to old bike+mtb. I had no intention of racing, no events near enough.

If you want to ride on the road get a road bike.

If you want somethign a bit more versatile that you could put racks on, have kicked around in the bike shed at work and have a slightly more upright position in traffic on then get a cross bike or a tourign bike.

tbh, round me the biggest time ‘loss’ when road riding is probably other traffic/my fitness rather than a couple of pounds bike weight.

I know the answer you’re looking for.
It’s “YES! you should buy a CX bike”.