Tires vs. Terrain Question

[Longhorn]

I have the stock Bontrager 700x35 tires that came with my Trek 7200 hybrid. I found a shortcut on my commute that cuts out about half a mile and a good-sized hill but it's a gravel road (maybe a quarter to third of a mile) that is pretty rough in places (I'm not sure I could even take my Mustang over it!) I haven't seen any glass. Some of it is just gravel but one section is embedded and loose rock.

Is this something my tires should be able to handle? I've been over it four times so far with no problems. I go very slowly and try to aim for the smoothest part. I'm more worried about falling than a flat, but I wouldn't want a flat, of course, especially on the return trip when it is approaching dusk.

I've never had a flat and I'm just wondering how much risk I'm taking. Thanks!

[BiggJawn]

1. They should be able to handle it.

Being wide 35's, they have enough cushion to take it.
I'm not sure what passes for "gravel" in your part of the world, but up here in Hoosierland, it's just plain old chrushed Limestone.

There's a road near me that is a mile of crushed stone, and I hate it on skinny tyres, but can ride my big Paselas down it at 13-14 MPH.

[Longhorn]

8. Ours is mostly crushed limestone, too.

Thought some of this is not so crushed. The gravel part is actually the easiest to cross so far -- it's the bigger stuff that had me worried but so far so good.

Thanks again, BiggJawn! :)

[happyslug]

2. The Real issue is braking

I have NEVER had a problem on Gravel when it came to Pedaling. The problem is when you have to brake. Gentle braking is NOT a problem but when you have to hit the brakes hard, that is when I have lost control. Now what I mean by losing control I slid when I was NOT planning to slide. I have never fell off a bicycle (I did lose control of a Motorcycle do to gravel on the side of the road that I turned the motorcycle on which gave way which caused me to fall, I just picked myself up afterward and continued riding I was wearing a helmet).

[happyslug]

3. More on Braking and bad road conditions

First you must understand how your bike STOPS when you hit the brakes. As the brakes are applied your wheels starts to slow down, thus providing less tire on the road (With 2/3 of your stopping power being provided by the FRONT Wheel and Brake).

Once the brakes are applied, the wheel transfer that braking power to the tire via the ability of the Tire to apply stopping power to the road surface. This stopping power is a product of the traction of the tire. Traction is a product of how much tire is contacting to the road surface (tire pressure is also a factor which I am ignoring here). The more tire surface on the road surface the greater the traction you have. Please note tire surface includes the surface of the tire as its rotates over the road. If you lock up your tire the only part of the tire coming into contact with the road surface is that part directly against the road surface. If the tire is rotating the traction of the tire includes that part of the tire just leaving the road surface AND that part of the Tire about to come in contact with the road surface. Thus often the faster you go the more traction you have.

Do to this characteristics of Tire, in snow conditions Driver Instructors tell Drivers to drive slow and if they start to slip to touch the GAS and Accelerate. You get more traction as you accelerate do to more tire on the road. The reason you go slow in snow is to be able to speed up if you have to.

Hitting the Brakes restricts your tire on the road to that part of the tire on that slick part of the road. This reduction is tire surface on road surface minimize the traction of the tire (Yes I have had many a person pass me driving in icy condition and later see them in the ditch, for they were going the max speed they could handle in the weather conditions and thus when they started to slide they could only hit their brakes which caused them to lose control of their vehicle and send it into the ditch).

Gravel is the same as snow, it is only a problem if you need to brake (Or is excessive and loose i.e. never driven on by a car or a Roller, but such gravel is rare for it is even difficult to walk on. I just put some gravel on a Drive way and it is lose where the cars had not riven on it and push into the ground, where cars have travel on the Gravel it is solid).

If you go slow Gravel is NOT a problem. You will NOT slide unless you start to slow up for some other reason. If you keep up a steady pace you just will NOT slide (Or if you do slide it will be do to excess gravel that would have caused you to slide anyway). Remember your tires maximum traction is when you are going at a steady pace. If you start to slide pedal a little faster and you will get out of most situations. On the other hand you should be going slow enough that you do not need to BRAKE if you start to slide (Braking is the worse thing to do if you start to slide). Yes, it takes some discipline to drive on loose road surface i.e. going FASTER when you want the car or bike to stop sliding but not a problem ONCE YOU REALIZED TRACTION is what you need and that maximum traction is achieved by NOT BRAKING.

Side note on Tire Pressure. Most Bicycles have high pressure tires to minimize roll Resistance. While this is fine but low roll Resistance also means low traction. One way to increase traction is to drop your tire pressure. The lower pressure will permit the tire to "Grab" the road better. In Cars this is important. Once when I was in the National Guard my 2 1/2 ton truck was struck in the mud, so I deflated the Tires to 15 psi and re-started the truck, had no problem pulling out. Took me another 1/2 hour to get the tire pressure back up but I was back on the Road without having to wait for a tow truck.

While Lowing tire pressure would increase traction given the low speed you will be traveling on a bicycle I just do NOT think dropping your tire pressure is a good option, but I do mention it in that it is one way to increase traction of a tire.

Tire treads are also a factor when it comes to gravel, with Knobby tires about to drib around a small amount of Gravel, but given the nature of most gravel Roads I have travel on really not a problem and I would stay with slicks. The knobs are even less of a factor in traction than tire pressure, the key to traction is to minimize braking.

[Longhorn]

9. Snow isn't something we ever have to worry about here

but I appreciate the information about how braking works and snow makes a good example. And I agree about the tire pressure, especially since this little stretch is maybe 1/24 of the entire commute so I need that pressure on the road.

Thanks for the information! :)

[happyslug]

10. Yes, Snow and Gravel are rarely a problem

On the other hand I hate ice. The last two winters have been bad in my area, a lot ice, packed snow and loose snow. The Loose snow is Never a problem, your tires cuts right through it. Ice and packed snow are a problem. Your tire just rides on the ice and I have slipped and fell on ice. To prevent that I use studded tires once the ice starts to lay. Generally around Christmas and by the end of February they are off the bike (and during any warm period the tires come off). These tires give a lot of traction at the price of a lot of roll Resistance. I do not use them on long trips but the short trip to work they permit me to bike during winter.

Just a word on studded tires if anyone wanted to know about them. Studded tires are sold at the following cite:
http://sheldonbrown.com/harris/tires/index.html

[Kolesar]

11. Brake with the front brake levers

Sheldon Brown wrote this in one of his essays at his Harris Cyclery site.

When you brake, the weight distribution shifts to the front wheel. The reduced weight (force, actually) on the rear wheel means that the total amount of friction on the back wheel is less and it is likely to lock up and skid. A skidding rear wheel may sway out left or right like a car doing "fishtails" on a snowy road. The cyclist may lose control!

This all seems counter-intuitive, because none of us want to lock up the front wheel, which would seem catastrophic. However, Brown claims that he did experiments and determined that he could brake as hard as possible with the front, and still never lock up the front wheel.

Sheldon Brown instructs cyclists to only brake with the front levers. He says that there are situations under which a "highly skilled" cyclist should brake with both levers, but does not detail what those situations are.

[wtmusic]

4. You should be fine

The size of the tread shouldn't be too much smaller than the size of the stones you're riding on.

Do you feel your wheel "sideslipping" when you try to steer?

[Longhorn]

6. So far, I haven't felt any slipping at all.

I pretty much let gravity pull me through and try not to force the steering. Thanks for your help! :hi:

[welshTerrier2]

5. i ride on 28's ...

i find them a fair bit faster than the 35's and they can handle almost all "road" conditions ... i think they're a great "compromise" width ... with 35's, you shouldn't have any problems on the road you described ... it's a fairly short distance, so, if you stay under control, you should be fine ...

one tip though ... you talked about never having gotten a flat ... the only one i ever got was in my very first century ride ... i road with a thumbtack in my front tire from about mile 15 to about mile 85 ... the tire wasn't losing pressure but it was very slippery going around corners ... finally, at mile 85, the tire gave out ... i was so damned tired i couldn't get the tire off the rim ... a "good samaritan" riding in the same race stopped to help me ... the guy was great ... had the tire changed in less than two minutes ...

and the tip? practice changing both your front and rear tires while you're at home ... get it down to a science so that you have confidence in your ability to do it ... changing a tire on the road is no fun if you're having trouble ...

btw, Longhorn, thanks for the Google Earth tips ... i love that mapping tool ...

[Longhorn]

7. I know you're right about practicing.

So far, I've only done it once in the Road I course I took and then the men in the class kept "taking over." ;) Guess I should get better at it just in case!

Google Earth is addictive, huh? :)