Charbon

I live in San Francisco, which has streets that are probably similar to a lot of other relatively dense road networks.
This is my bike:
https://www.gtbicycles.com/usa/eng/Bi...anseo-3.0-Disc
As you can see from the link, it has 700 x 35c WTB AllTerainasaurus wheels. The bike and the wheels are more off-road than street. They have pretty hard protrusions.

My apartment has a multi-level parking structure at the bottom. I was riding down the structure and took a spill at a right turn. I really felt like I had the turn under control. But my bike slipped from other me and I landed on my back. I think I'm okay but my confidence in my bike and skills is damaged. The concrete in the garage doesn't seem that slippery to me.

I went to the local bike store and I was told that I might need slicker tires that would grip the road better. I'm a little peeved by this advice. (When I bought my bike I made it clear I wanted to commute and be able to do some light mountain biking.)

Are my tires why I fell? I am mostly doing commuting at this point and haven't had much chance to mountain bike. Are my wheels inappropriate? What is best to grip pavement on sharp turns? I thought fatter tires would be better at this.

rumrunn6

nice bike

the fall could be a combination of things: inexperience; speed; angle of turn, etc. I wouldn't blame the tires. plenty of people commute on MTB tires. not great but it works. MTB tires aren't best for commuting, but not because they will make you fall, because they will suck up power and speed. I like marathons and armadillos. lots of people change the tires that came with their bike, so don't feel bad.

MNBiker

Charbon,
First off, it's hard to know exactly what caused you to fall from what you told us. Factors include things like:
- was it clean, dry concrete you slid on or something else (wet conditions, sand on top of the concrete, etc.)?
- is the concrete quite smooth or is it rough?
- you were going downhill. Is it quite steep, did you turn sharply, were you going quite fast?
- were you using good braking technique? Do you tend to brake more with the front or back brakes? Did you fishtail and have the back wheel slide out from under you?

Talking about tires rather than biking/braking technique, here's a quote from www.ehow.com about bike tires:
Perhaps squirm is what you experienced.

Unfortunately, unless you have more than one set of tires or more than one bike, if you are going to bike on more than one kind of terrain you have to make some kind of compromise in tire selection.

For me, I primarily bike and commute on paved roads. I use fairly smooth road tires which grip the road pretty well and also lessen the amount of rolling resistance. Knobby tires make for more work when peddling on pavement -- the knobs work against easy rolling.

xtrajack

First thing I did after I bought my bike, was to buy slicks. Last year I changed to Marathon Plus tires, I don't like flats. In the winter, I run Nokian Mount and Ground tires.

Loose Chain

Slicks are better for road, knobbies for off-road. You bought one bike to do the job of two and now you have to decide which it is, a mtb or a road commuter and purchase tires to suit that mission. Get another set of wheels also or another bike.

irclean

My experience has been that slick tires grip pavement (both wet and dry) better than tires with any sort of raised tread. I was a little hesitant to switch at first, but then someone pointed out to me that many motor racing vehicles use slicks (think Nascar, Indy, Formula One, drag racing, etc.) and they all need great traction to remain competitive. I now use Michelin Pilot City tires on my primary commuter and I love them. They have sipes to channel away water on rainy days plus puncture protection, which IMHO is invaluable for commuting.

Of course no tire is going to grip on oily, slick surfaces, and if your parking structure is subject to oil and lube spills from vehicular traffic then that could very well have led to your crash. I'm glad to hear you're OK and I believe that you need to get right back on the horse (so to speak) and keep riding.

PS. Having another set of wheels mounted with knobbies for off-roading is cheaper than having another bike, but another bike is nice!

colleen c

Most garage I know of are slippery. Have you ever listen to cars as they turn their wheel while in motion in a garage? The one thing you will notice is that rubber to concrete sqealing spound indicating a slippery surface. Also keep in mind that in an garage, their is always the chance that there are some oil in the surface although you may not notice it. The oil does not get wash away in a rain storm like road outside.

Now add that along with some knobby and you might lose traction unexpected. You also mention that you are mostly commuting. Did you have a load that were heavy on the back of the bike which will make the front end lighter? Your odds of slipping increases when the steering is lighter while riding over slippery surface with knobby tires.

Charbon

Thanks for all the great responses.

- It was indoor. Later on I inspected the area and I could not find any oil or other issues.
- On close up the concrete looks fairly rough but I do suspect it is smooth compare to public streets.
- I was going downhill (not good at estimating grade and didn't brake). I was going quite fast. I just assumed sufficient leaning would counteract speed (sort of like motorcycles do). Is this a dumb assumption?
- I'm not sure I was braking, the bike pretty much slipped out evenly under me, but I might be forgetting something as the wind was knocked out of me.

I was definitely pushing it for my level of skill and experience. But it does sound like squirm could have been the failure and in any case at this point I think I'll feel safer if I have better grip. I would have liked LBS to go over these risks with me when I first bought bike but oh well. I incorrectly assumed an off-road tire would have better grip although I understood the trade-off in performance.

So I assume you buy an entire set of wheels, not just the tires? About how much should this set me back? Anything else I want to be aware of this time?

alr

You may just change the tires, too. It is not that big a deal. Keep the slicks for commuting and switch to the mountain tires when you go to off road-- that assumes that the off road is a weekend infrequent kind of thing.

Kimmitt 

No, but it isn't a good one. Bicycle tires have a big tradeoff between efficiency and traction, because of the far less powerful engine.

tjspiel

This is like Deja Vu. I swear there was a topic just like this about a year ago. I think the general advice was to go slower while spirling down parking garages. ;-)

Sounds like you were the victim of centrifugal force. Leaning keeps you from flopping over one way but doesn't deter the bike's desire to head in a straight line. You exceeded the ability of your tires to keep that from happening. Different tires might help. Slowing down whilst cornering will too.

I ride all winter in ice and snow and I've had my confidence bruised a couple of times. Consider it a learning experience. The confidence will come back.

BarracksSi

"Dumb" is a harsh word, but since you're the one who said it...

You simply tried to scrub speed by sliding the bike. It works for 4-wheeled vehicles, but not for bicycles, and neither for motorcycles.

No, the failure (again, not meaning to sound harsh) was your attempt to turn too hard for your equipment and the surface conditions. You can ride safely on knobbies as long as you don't try to lean like you're riding a MotoGP superbike. You really have nobody to blame but yourself, honestly -- not the tires, and not the LBS, either.

whitecat

May I suggest that if you wish to ride fast on slick surfaces such as a garage and similar, you should get quality slick or semi-slick tires. Such surfaces are not the frendliest as you noticed, I had similar expiriences too. You have more choiches; you can ride slower - which is higly recommended, since you said by your own words you were pushing it, you can avoid such surfaces, or you can get better quality, softer, stickier slick tires. I've had good expeiriences with CST and Panaracer tires in such applications, with their more expensive top-of-the-line, dual compound tires. They cost from 30 to 50$ per tire, but they seems to hold much better on slippery surfaces then ordinary tires. Ofc, everything has it's limit and those tires are not magical, you can also take a spill when riding on them if you're not careful. But overall, better tires help quite a bit. And please, don't ride knobbies on the pavement if you wish maximum traction and stability - it's simply not a good idea.

kevingoorijan

THe bike looks fine to me. Infact, it looks great! Regarding the tires, i recommend knobbies tires. By the way, if you don't mind me asking, what brand of socks do you use when biking?

ekincam

The roadways in SF are typically asphalt not concrete. If this was a garage or parking structure, the concrete may be smoother or sealed to prevent oil from seeping into the material.

PaulRivers

Weird, it's like someone wrote a madlib! Bike looks good...I recommend knobby tires for no reason...what brand of socks do you wear...what's a good pizza place...have you heard about the latest ufo sighting?

One question I haven't seen asked is - was there any paint where you slipped? Street paint is notorious for being slippier than the pavement around it.

I guess the first advice would be to not going hard and fast on parking ramps, not that that's not obvious. :-) Sounds like you pushed the bike past it's limits.

The bike shops guys are somewhat right though - on pavement a knobby tire has less grip than a slick. Whereas on dirt the knobby part digs into the dirt, on pavement the knobby part just keeps the inner part of the knobs from ever touching and gripping the pavement. And since the knobs flex, that add additional instability into the ride.

I followed your link, and the bike appears to cost $600. For that price, you probably aren't getting great tires either.

fadi

Soft and slick tires will have the best grip until a water layer of a wet surface gets thick enough and manages to separate the tire from the ground... at that stage you start aquaplaning and you are gone!

To solve this issue, manufacturers introduce some threading in the tire so that they would guide and evacuate the water from underneath it, avoiding the aquaplaning effect. The bigger the quantity of water that you need to evacuate and the bigger and deeper the threads. Think of them as pathways for the water to exit (sideways)

This apply to any substance in fact that is getting in the way between your tire and the ground, whether it is water, snow, mud, dirt and so on...
Thus, the difference in design between tires intended for road, wet, snow, mud, gravel and so on.

Manufacturers have R&D units that do these extensive engineering tests and trials to find a balance between grip, rolling resistance, life cycle, weight, price, and so on... And they come up with their own shape of threads, material, construction, etc.

Mother nature and physics makes it impossible to optimize all these factors at the same time; they act against each other most of time


Tire science is of course much more detailed than this; you have also temperature playing a big role, weight and so on... But a casual biker in my opinion would just try the model recommended by his friend or over a forum and see if that works for him or not. I would do the same too

I just wanted to give some insight on the subject for the interested

In the end, and as a very rough guideline, you have to favor slick or very shallow threaded tires if the majority of your pathway is "clean" and dry; increasing the amount and depth of threads according to your level of "pollution" on these pathways.

Cheers
Fadi

PS: Those living in cold regions, can quickly compare the amount and depth of threads on their car'swinter tires compared to the summer ones

BarracksSi

Bike tires don't aquaplane.

Slippery surfaces get slippery, but it's not the same as aquaplaning.

fadi

yeah that's right due to the very small surface of contact opposed to a car's tire, but for explanation purpose that still holds true

PaulRivers

Yeah, everything I've read about your explanation has said that that is completely and totally urban legend. Factors include that your bike doesn't travel at the high speeds that cars do, as well as that car tires are flat, whereas bike tires are rounded so far better designed for cutting through the water that they come into contact with.

Like, see Sheldon Brown -
https://www.sheldonbrown.com/tires.html#hydroplaning

I'm sure you're just trying to be help, but in the interest of being helpful myself I do not believe any of that is true. I've read - repeatedly - that tread on road bike tires (the patterny stuff, not the full on knobs on mountain bike tires) is there purely for decoration and because people are simply accustomed to thinking that tread == grip. Marketing purposes only. The ability of your tire to grip in the wet is only affected by the tires size, inflation, and the compound used to make the tire.

The only affect knobby tread has on performance in water is to detrimentally reduce the surface area of the tire that's in contact with the road. Tread coming into contact with a material it can actually grip, like dirt or snow, is completely different.

Oddly, enough, on the Sheldon Brown site I also ran across a section regarding the OP's original question -
https://www.sheldonbrown.com/tires.html#squirm

Squirm
Combination Treads

2manybikes

Who knows what happened.

But, you can't dive into corners with an all terrain tire, or an off road knobby, like you can with a real road tire. Lots of people learn this the way you did. One can learn to corner slower with knobs on the tires. Road tries will help, but lots of people commute with knobbies, It's up to you.

fadi

You are definitely right about the treads bending under side loads, and that's one part of the story as there are so much more details to have a complete picture of what happens to a tire

Let's look at traction from the point of view of friction if you want; as we have learned about it in physics class: friction = coefficient of friction x normal force.

The friction between two surfaces (or the traction applied by a tire) can be increased in two ways:
1. Increase the coefficient of friction
2. Increase the normal force

The normal force is the force pushing up on the tires.
Caused by the weight of the total bike and rider, it is in fact equal in size (but opposite in direction) to the weight pressing down on the ground.
The greater the weight, the larger the value of the normal force, and as a result, the larger the friction force.

The coefficient of friction is a number that is determined by the nature of the two surfaces in contact. The 'rougher' the two surfaces are relative to each other, the bigger this number will be... and the larger the friction force.
When a tire meets dry pavement, the two surfaces that are in contact... rubber and asphalt... have a high coefficient of friction, so your tires will have good traction.

The amount of area in contact between two discrete surfaces does not affect the force of friction; whether the tire has treads or not is irrelevant. Some tires are completely smooth; tires like this are called 'slicks'. An increase in friction is not provided by the increase in surface area contacting the road; treads are just not used because they are not needed on a dry road.

So why not use slick tires all the time?

The answer is that the roads are not always smooth and dry. If you were riding on slicks, the first time it started to rain you would skid right off the road! And riding in snow or mud? Forget it!

When the roads are very wet, you are actually driving on a thin layer of water. Rubber and water have a very low coefficient of friction. You need to increase the coefficient of friction by allowing some of the water to escape, so that the tires are contacting wet pavement instead of just water. The coefficient of friction between rubber and 'wet pavement' is a larger number. So one purpose of treads is to allow water to escape.

Tires also have treads so you can have traction in snow and mud. This works by allowing the snow or mud to get between the treads. You could think of this as increasing the coefficient of friction of the tire as a whole, because it is no longer as smooth.

However, what is really happening is that the tires are now grabbing and pushing snow or mud backwards; this requires more power to be transferred to the tires ;-)
in fact, a greater force is applied, causing a greater 'equal-but-opposite' reaction force, which is what pushes the bike ahead. Better traction comes from more force being applied to the ground in that case, not an increase in friction

Now, it is arguable whether bike tires hydroplane like any other tire or not.

PaulRivers

Look - I'm sorry. Your posts have been very eloquent. But since they're also eloquently wrong and misleading, I don't know what I could say that doesn't make me sound like a jerk.

1. You said that "The amount of area in contact between two discrete surfaces does not affect the force of friction; whether the tire has treads or not is irrelevant".

I have no idea what that means, really.

Physics often uses terms that sound like everyday terms, but mean something completely different. Like "force". In real life, if you slammed yourself against a wall at full speed you applied a lot of force to it. In physics, you applied no force to it because it didn't move. Using physics terms, thus, is often not helpful unless all parties really, really, really understand physics.

In the end what matters is - how do things end up working in the real world. If you ride one bike with big fat tires, and another bike with skinny tires, you will find without a doubt that the one with big fat tires (if they use similar brakes and tire compounds) has a much smaller stopping distance than the one with skinny tires. That's just the way it works - the more contact area the tire has with the ground, the faster it can bring you to a stop.

When you're in the wet and not charging through a puddle (typically wet weather riding), the physics don't change - the more of the tire that's in contact with the road, the sooner you stop if you hit the brakes. I know this, before I have different bikes - and I've done it. The skinny tire bike continues to stop slower and has less grip than the fatter tire bike. Tread reduces the amount of tire that's in contact with the road, thus it has less traction. To be fair, my solid belief in this does not come from theory, but from practice - I've ridden bike with knobby tires, and bikes with slick tires. The knobby tires are less steady, and have worse stopping on pavement.

I've also seen myself that different tire compounds can dramatically affect how the tire works when the road is wet. I know this not because of theory, but because I've used a bunch of different tires. When you go from tire A that's a slick to tire B that's also a slick and the same size, and tire B definitely has more grip, there aren't any other explanations.

I cannot say, if you're biking through a puddle, the exact effects of having tread, but I very very very much doubt that knobbies positively affect traction. In order to "cut" through the water, each bit of knobby tread would have to be pointed, and they're not - each one is usually square and flat. If they're not now, they will be if you ride a while. Also, if 2 knobbies both push water out towards each other, since water doesn't compress wouldn't that energy just cause the displaced water to go down, pushing up on the tire?

I could theorize on, but frankly - I just don't think it's true. In theory I think you're better off with a skinny tire the throws water clearly off to the sides rather than having treads throw them every which way. In practice, I've just never heard of anyone even claiming this was the case before, and with marketing I'd think I would have heard something about it.

Charbon

Thanks for the additional responses.

To answer a couple questions: - I usually ride with men's dress socks the kind one would wear with slacks. :-/ - no noticeable paint on the ground. The only thing I found in the area was a piece of plastic but it wasn't too close to the site of failure when I came back (I only inspected the accident site about two hours later) so I don't think that was the cause.

In case anybody cares I think I'm just going to ride slower. I'm not sure my bike is nice enough to warrant further investments in additional wheels. Switching tires seems like a pain in the butt. Hopefully I can eventually get a different bike that is more street focused.

2manybikes

You can certainly do that and have no problems. However, smooth road tires also roll easier and will reduce the effort or increase your speed a little, without changing wheels or bikes. A couple of tires would not be a big investment. Even high end tires installed at a bike shop might be less than $50.00. You really do have a bike well suited for commuting. With practice it's easy to change two tires in ten minutes. You probably will be getting a flat eventually, it's easier to learn and practice fixing flats at home, when you don't really need to get going in a hurry.