Amerikuracana

Hello all. First post on these forums, I wish you all good health and good biking.

I am thinking about buying a road bike. I will use it for exercise, testing myself, and possibly for some commuting. How much can road bike take? With their quickness on the road, are they pretty unable to take riding over dirt or grass? I would obviously be more careful when commuting on a road bike than a mountain bike, which I currently use. But are road bikes apt to break real easy if not on flat concrete 100% of the time? Again, the non-road would be minimal, but even sidewalks, there is about 2 miles where sidewalks would come into play, am I over judging the ruggedness of a road -bike for wishes of faster commute times? I appreciate any feedback from anybody who knows, or who commutes on a road bike. Thanks.

rpenmanparker 

It's not about breaking the bike, it is about breaking the rider. Seriously, the bike can hold up with exception perhaps of very lightweight wheels and tires. The problem is the rider's comfort and ease of pedaling, balancing, and bike handling on surfaces rougher than normal roads. Not everyone has trouble with it, but riding a full bore road bike on gravel, sand, mud, or grass can be challenging for some.

See the similar thread established over the last few days. The posts there may help you.

ThermionicScott 

My road bikes are fine away from the pavement. Can't speak for anyone else's:

Sprocket Man

It depends how heavy you are. It depends how fast you'll be riding on dirt and grass. It depends on the ruggedness of the surface you're riding on. It depends how frequently you'll be riding on it. It depends on the structural integrity of your particular frame and wheels. It depends on how much pressure you put in your tires. So in summary, it depends.

Road bikes are pretty tough, though. I've been riding for over 20 years and although I've broken a few wheels over that time, I've never broken a frame.

Amerikuracana

Thanks first three posters. Handsome fella in the second pic there. I checked the other thread, and I got a little of what I was looking for, although I don't know if watching those "bike party" videos will improve my realistic view of what a road bike can handle lol.. I'm 220-230lbs, and although I am technical crap on a bike, I ride fairly fast on flat surfaces from what I have been told. I have big natural legs, and I always go as fast as I can tbh. My budget is also an issue, the bike I am looking at is a $16-1700 bike, so probably lower end in terms of road bikes. I would think you would lose more lightness than durability, but that may be wishful thinking.

big chainring 

Things that I have messed up riding a road bike off road. Snapped a Campy NR crank arm. Stripped the threads(freewheel)on rear hub, Campy Record. Bent top and down tubes on my Somec. Flat spotted many rims, on and off road. Best to use a bike for its intended purpose.

StanSeven

Road bikes won't break but they aren't ideal. For example that's why cyclocross bikes y are made - to ride/race a road type frame with wider knobby tires and brakes for mud and dirt. If you do some riding in dirt and gravel but want the speed of a road bike, consider a cyclocross.

kc0bbq

They're fine as long as you don't get to too soft a surface for you to stay rubber side down. Glacied sand in northern the northern US makes it tough, sometimes even on 2"+ mountain bike tires. Otherwise it's all good.

njkayaker

Sidewalks? Why?

I've ridden loose gravel paths on a road bike with 23mm tires. The road in the earlier picture looks fairly easy but loose in spots.

You will likely be happier on rough roads with wider tires. Especially, given your weight.

Note that the only real suspension on a bike is the tires and your legs (the less you sit on the seat, the better the shock absorption will be).

What about a cyclocross bike? That would be nearly as fast as a regular road bike but gives the option of wider tires.

Amerikuracana

If a Cyclocross bike has knobby wider tires, why is it as fast as a road bike? One of my Mountain bike has more road type geo, and it is fast in terms a mountain bike for commuting, but are cyclo tires a bit smoother? There is one CX bike I saw that I like, but it's a 62cm and it might be too big, but I like big bikes. I'll look into it.

Wanderer

Wider tires don't necessarily have to be knobbies ---- they can be slicks, or even semi slick, and still get the job done.

RPK79

Having a CX bike will offer you more options for tires since there is more clearance. You can put slicks or knobby tires on it.

Kopsis

Until you start approaching the UCI weight limit (~15 lbs), road bikes are pretty durable. Wheels are probably the biggest weakness, but until you get really spendy, most road bikes come from the factory with a pretty durable (albeit heavy) wheelset. Avoid featherweight, low spoke-count wheels and you should have no problem. Check out some cyclocross videos for a more realistic idea of the kind of abuse a road bike can endure. CX bike frames are typically about 25% heavier/stronger than pure road bikes, but they're designed to spend close to 100% of their time being thoroughly abused.

When the going gets a little rough, wider tires will dramatically improve the comfort factor. Finding a road bike that can accommodate a 28 or even wider tire might be a wise move. Some of the race-oriented frames struggle to handle more than a 25 width. Cyclocross bikes can typically handle up to a 35 wide tire, and gravel-grinder/touring bikes can often go as wide as 45. My "go to" bike for all but the most intense training rides is my CX bike with a set of 28 slicks. Comfy, bullet-proof, and only a couple MPH slower than my carbon "race" bike.

FrenchFit 

+1. That pretty much says it all.

njkayaker

You are misunderstanding.

You can put regular 23mm tires on a cyclocross bike and it won't really be slower than a regular road bike.

Wider tires are much better (faster) for rougher roads.

The cyclocross gives you the option of using wider tires.

A regular road bike doesn't (you are stuck using narrow tires).

Get a bike that fits you properly. If you are an inexperienced cyclist, don't assume that a size you like is better than what an expert says would be better.

Amerikuracana

Although you make my decision more complicated now, I definitely appreciate the knowledge. I am going to be honest, what ever bike I buy, I will probably be leaving the tires on for a year. I change tires in a couple minutes like everybody else, but when I buy a new bike I just have this thing that I ride it the way it came for a while before I start changing stuff. I have bikes that are 5-6 years old that are very different from when I got them, but I usually leave bikes the way they were intended for a while. So I just wonder how much faster a CX bike would be (than a good geo MB) without slicks on it, or with standard CX tires.

Looigi

Yeah. I've ridden my CF road bike on dirt, gravel and even many miles of single track. The limit is the tires and possibility of pinch flatting more than anything else. Next is damaging the wheels by hitting a sharp edge. The last thing I'd be worried about is the frame.

Cue a Marty Ashton's Road Bike Party vid....

njkayaker

Using the wrong tires because you are lazy (?) doesn't make much sense. You'd be more comfortable, faster, safer with wider tires on rough/unpaved roads.

Since you are saying that you won't follow advice that you agree with, it doesn't really make much sense to ask for advice (or for people to give it)1
It's not clear why you aren't just using what you have.

If you are riding short distances (a few miles), it doesn't really matter.

If you look at the bikes that people ride in centuries (organized 100 mile rides), most of them are using road bikes. Some of them are using cyclocross bikes. Very, very few are using mountain bikes.

A cyclocross bike is (basically) a road bike that you can put wider tires on.

A bike that is not too heavy is a bit faster and more pleasant to ride. If you are riding on really rough/rocky roads, you should use a mountain bike. If the roads are just unpaved and relatively smooth, a mountain bike is overkill.

Mountain bikes tend to be heavy and put the rider in a less aerodynamic position (which is slower).

coasting 

it might handle more than i give it a chance to., but i get scared when i hit a bit of gravel. i once nearly wiped out on a downhill twisty road where some repair had been done and fresh gravel was laid down. since then if i see gravel i go really slowly.

Kopsis

Your question can't be answered the way you asked it. I think what you want to ask is "what's the difference in power needed to ride a MTB and road bike at a given speed" and "what's the power loss due to rolling resistance between CX tires and slicks."

A typical MTB CdA is about 0.4 m^2, a typical road bike CdA with rider in the drops is about 0.32 m^2. So at a given speed, the MTB will need about 25% more power to overcome aerodynamic drag.

Rolling resistance coefficient (on pavement) for a typical MTB is 0.006, for a road bike it's 0.003, so MTB knobbies eat about double the power in rolling resistance that road bike slicks do (plus a little more because the MTB is typically heavier). I'd guess CX tires are somewhere around 0.004, so 33% more loss that road slicks.

Now, in terms of power percentages, it's pretty complex, but it suffices to say that at 22 MPH a road bike rider needs on the order of 170W to overcome aerodynamic drag and another 20W for rolling resistance (there are drivetrain losses and other stuff, but it's not really a differentiator). The MTB at 22 MPH would need +20W for the tires and +40W for drag (+60W total to keep up with the road bike at 22 MPH). Pretty significant, but not as bad as some people think.

A CX bike with all-around cross tires is going to need about 7W more to maintain 22 MPH than it would with slicks. File treads would be better, mud tires worse. How much that's going to slow you down depends on how fast you want to ride.

The main reason not to use CX tires for road is that they wear really fast and they're not very puncture resistant (not a lot of broken glass to deal with on the CX course -- hopefully). If you think the "OEM" tires a bike comes with are carefully selected to produce a certain "feel", you're being idealistic. I think the industry insiders will confirm that OEM tire selection is all about availability and meeting a certain price-point.

Disclaimers: calculations make massive generalizations and are based on pretty old data (road bikes were less aero and MTBs all rode 26" tires). Data from Bicycling Science 3rd ed., Wilson, David G., and Jim Papadopoulos, MIT Press.

Myosmith

There are so many variables, but there are plenty of road bikes that will handle the rigors of commuting on less than ideal surfaces. Before the advent of cyclocross specific bikes, many riders just put on the largest tires their road bikes would handle and hit the challenging multi-surface events. I wouldn't do a lot of curb jumping or blasting through potholes, but a road bike will work just fine for you.