General Cycling Discussion - Tire width/slickness and size; what's most important in creating stability?

Hello All -- I am buying a new bike. I have chosen a "comfort" (Specialized Expedition Sport) bike b/c I am looking for good stability. My only reservation is the wheel size and width of tires in terms of roll resistance. The guy at the bike shop is looking at some slightly narrower tires which have a "beaded center" (I think that's the term) and are not quite as aggressive as the tires already on the bike. These will give me less roll resistance, which makes sense.

My question -- how much stability am I sacrificing with a narrower tire (40-42mm compared to 49 I think)? Is tire width more important to stability than tire size (circumference)? The bike guy says the important thing is that I have the 26" wheels, not so much the tire width. There isn't much of a cost difference so it doesn't mean more money to them if I switch (probably more trouble to swap tires). Thanks for any advice on this!

Joe

what do you mean by stability?

he/she means stability=grip. by switching to a smooth, narrow tread, you will greatly increase your performance on pavement, but will really hurt anything else. you won't really be able to ride on gravel or loose dirt... even riding on hard pack will get sketchy at times. but if you are riding strictly pavement, then the skinniest smoothest tire you can find will be fine.... well fine as long as the tread isn't made of teflon :)

i just put some 1.25 inch tires on my mountain bike. i've found the traction on dry pavement is the same or better, the steering is more responsive and sometimes is a little "too" responsive. hard pack gravel isn't as scary as i thought, i really haven't noticed much of a change in stability.

I ride 20 & 23 mm tires..no groves in the tires (slick) ..weigh 250#+ (don't go there) with no problem with stability, etc.

On a hybrid...only want you want it to look like counts.

And apparently I get to say it first:D

WELCOME TO THE ADDICTION!! :beer:

For general purpose ridng on roads and good trails/paths, many experienced riders chose a medium width tyre with a slight indented tread (a touring tyre or a so-called slick). For 700c wheels, that would be 28 to 35mm, and for 26" MTB wheels , a 1.25 to 1.75 tyre.
These medium-width tyres hold sufficient pressure (80-100psi) to be efficient, but are wide enough to give a comfortable ride and absorb impact from potholes and bumps. Most leisure style bikes have tyres which are far too fat and low pressure for easy cycling. You dont need a heavy tread, and these slick tyres are quite capable of handling well prepared ie hardpacked trails.

Thanks all -- what I mean by stability is how susceptible the bike is to flipping over (esp on turns) on both pavement and a packed (groomed) trail. I will be pulling a bicycle trailer with my 10-month old and want it to be safe.

It was my impression that wheel width would be more important than wheel size in keeping a bike stable. But, the bike person I'm dealing with says that the 26" wheels, even if you go from 48mm to 40mm on the tire width, will keep the bike pretty stable.

I think my question has been answered, but if anyone has any more thoughts, it is much appreciated.

I always thought stability was a function of the rider, not the width of the tire.

It's a free world..every person can use what ever they need to define what they want to say.;)

and actually after thinking (I know:() about it..... the wheels do provide the gyroscopic action that keeps the bike upright, and the centrifugal weight enhances the gyroscopic action. (now my head hurts:mad:)

Originally posted by 1oldRoadie
. . . and actually after thinking (I know:() about it..... the wheels do provide the gyroscopic action that keeps the bike upright, and the centrifugal weight enhances the gyroscopic action. (now my head hurts:mad:)

A common misconception, but simply not true. Spinning wheels add a small about of "stability." But their effect is insignificant to keeping a bike upright. David G. Wilson (author of Bicycling Science) once built a bike that had counter spinning wheels to offset the primary wheels gyroscopic action and it rode just like any other bike. He did it primarily to discount this old myth.

Dave

soooooo...what keeps the bike upright? if its balance then we should stay upright as easily still as rolling.

Originally posted by 1oldRoadie
soooooo...what keeps the bike upright? if its balance then we should stay upright as easily still as rolling.

To keep a bicycle upright, the cyclist continuously and minutely steers the front wheel to keep the line defined by the road contact points of the tyres under the rider's effective center of mass. Talk about "active stability control"! Counter-rotating wheels did not render a bicycle unrideable, but very long chopper-style forks did come pretty close in one experiment.

As for tyre width, Sheldon tells why narrower is not always better. In practice, I favor 700Cx23mm tyres for sport or club riding on dry, good roads, 700Cx28s for general-purpose on-road transportation and touring, 27x1-3/8" knobbies for cyclecross or for good trails, and 26 x 1.95 knobbies for offroad use. (This is one reason I have five bicycles.)

Exactly.

To illustrate this to yourself, grab your bike by the seat and roll it along beside you as you walk. When it starts to turn, lean the bike in the opposite direction. Note the handlebars then turn to correct. You can wheel your bike along indefinately just by holding the seat and giving it an occasional lean this way or that.

By the way, modern aero brakes and STI sometimes make this a little more difficult since the cables can exert a little push or pull on the bars, particularly if they were not exactly cut to the right length.

Dave

Great point, Dave!

I'm getting a pair of 26x2.5 slicks next week. Hint width.

IM going to buy two new tires this saturday too.
I dont want the narrowest ones , but not mountain tires either...
I want something like this guy hashttp://www.angelfire.com/al2/misha18male4/photosight/80000km.jpg