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Old 07-09-05, 05:31 PM   #1
phantomcow2
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would a narrower slick make a big difference?

Well currently I am using 1.4" RItchey tom slicks for my XC rig when it is on the road. The shop has this tire in 1 and 1.4, well im wondering if there would be a noticable difference (positive and/or negative) by buying a 1 when my current tires wear out
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Old 07-09-05, 06:01 PM   #2
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I think it would make a difference in aero, plus more if they take a higher psi.
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Old 07-09-05, 06:29 PM   #3
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I'd look to inflation pressure rather than just size. I'm running a 1.5 inch tire on the rear of my recumbent that inflates to 85 pounds.
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Old 07-09-05, 06:49 PM   #4
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Well the 1.4's that I have now recommend 55-85 so i have them at 85 now
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Old 07-09-05, 06:50 PM   #5
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Quote:
Originally Posted by phantomcow2
Well currently I am using 1.4" RItchey tom slicks for my XC rig when it is on the road. The shop has this tire in 1 and 1.4, well im wondering if there would be a noticable difference (positive and/or negative) by buying a 1 when my current tires wear out
Unless you have laboratory grade instrumentation I doubt you'll be able to measure much difference.
1. At equal air pressures the 1.4's will have slightly less rolling resistance.
2. The 1.0's will have slightly less aero resistance.
3. You'll probably run the 1.0's at higher air pressure if, for no other reason to minimize pinch flats. The higher air pressure will probably neutralize the rolling resistance penalty.
4. If you ride on crushed limestone rail-trail conversions, the 1.4's will feel much more secure.

In real life the differences mentioned above will fade into the background when compared with the effort required to push your torso through the air. The higher air pressure will probably "feel" a little faster because it bounces around more but actual measureable speed will probably be about the same. Higher air pressure will make your bike feel subjectively bumpier.

My advice is to buy whichever size you think looks cooler.
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Old 07-09-05, 06:54 PM   #6
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Quote:
Originally Posted by Retro Grouch
Unless you have laboratory grade instrumentation I doubt you'll be able to measure much difference.
1. At equal air pressures the 1.4's will have slightly less rolling resistance.
2. The 1.0's will have slightly less aero resistance.
3. You'll probably run the 1.0's at higher air pressure if, for no other reason to minimize pinch flats. The higher air pressure will probably neutralize the rolling resistance penalty.
4. If you ride on crushed limestone rail-trail conversions, the 1.4's will feel much more secure.

In real life the differences mentioned above will fade into the background when compared with the effort required to push your torso through the air. The higher air pressure will probably "feel" a little faster because it bounces around more but actual measureable speed will probably be about the same. Higher air pressure will make your bike feel subjectively bumpier.

My advice is to buy whichever size you think looks cooler.
Thanks for the comprehensive response.
I think next time I will get the 1's just to try it
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Old 07-09-05, 06:55 PM   #7
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Or maybe a 1 for the rear and 1.4 for front?
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Old 07-09-05, 07:04 PM   #8
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The 1-in tire will weigh a lot less, you could probably feel that difference when accelerating.
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Old 07-09-05, 07:33 PM   #9
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I think according to Ritchey there is a 100gram difference between 1 and 1.4"m which I know makes a difference (i could feel it when i changed my wheels)
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Old 07-09-05, 07:40 PM   #10
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Don't do it,
I tried going from a 1.4 Tom Slick to a one incher, and the ride quality went straight to Hell. It didn't feel much faster, either.
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Old 07-09-05, 07:53 PM   #11
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I just put the original touring rear tire back on my recumbent after trying one of Continental's training slicks. I'm always looking for less rolling resistance. I thought that going from a 35mm clunker at 80psi to a 28mm light weight slick at 120psi would make a huge difference. I figured that I would have to ride the brakes going uphill to avoid speeding tickets. As it turns out, it was only barely faster, and after only 2 days, the sidewalls were already starting to prove their reputation for being fragile. It was on sale so I'm not crying about it. It'll make a good back-up tire.
I'm not saying not to try the tires. I'm just beginning to think that for a given bike, rider, terrain, etc., there's a point of diminishing returns in changing things. Those tires may well turn your bike into a screamer, but don't be disappointed if they don't.

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Old 07-09-05, 08:32 PM   #12
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Hal is onto the correct answer. I once again defer to the highly regarded Bill at Torelli, for his explanation of why there is such a thing as too narrow. He's writing about width and pressure, and while this article is about road biek tires, it holds true for skinnies on your MTB:

Tire pressure. In the last decade it has become an article of faith that the more pressure one puts in a tire, the better (that is, faster) the bike will ride. One brand of tires actually requires 140 psi. This kind of tire pressure makes the bike ride like junk. With super high tire pressures the bike bounces, transmits road shock, fatigues the rider, causes the premature failure of bike frames and components and makes the tires more prone to flats. Running the tires at 105 - 115 psi will yield a bike that corners better and gives a far nicer ride. Try it. It will still go fast.

Tire Width. There is a view that a 20 mm width tire is faster than a 23 by virtue of its smaller cross section and lighter weight. Interestingly enough, this is not true. The people making the Torelli tires had noticed that the pro teams that they sponsored asked for 23s because they felt they were faster. When they investigated and did the testing, they found that the riders were correct. Let me explain.

Let's assume a 200 pound rider and bike unit. Let's also assume that the weight is distributed half over each wheel. That means that each wheel is supporting 100 pounds. Now, with a pressure of 100 pounds per square inch, the contact patch is one square inch. This is true no matter how fat the tire.

What changes when the tire gets fatter is the shape of the contact patch. With a 20, the contact patch is a long oval. With the fatter tire, the contact patch gets shorter and wider.

When a rider is using a skinnier tire, the long contact patch means he is flexing a wider arc of the tire casing, flexing more of the tire, causing more wasted energy from the internal friction of the tire and tube. The rider with the fatter tire is flexing fewer cords at a time.

There is clearly an optimum size, and the fact that racing tubulars are around 22 should keep us from getting super wide tires looking for yet more speed. Other losses probably kick in as the tire gets still fatter. For me, the bike feels like it doesn't have any snap or jump when we stray from the optimum which I believe to be in that 22-23 mm range.

Some have suggested that the skinnier tires make up for their losses because of their lower aerodynamic drag. This could be true for the solo time-trialist, I'm not sure. For the pack rider, it clearly is not an important consideration.


Food for thought.
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Old 07-09-05, 09:11 PM   #13
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Quote:
Let's assume a 200 pound rider and bike unit. Let's also assume that the weight is distributed half over each wheel. That means that each wheel is supporting 100 pounds. Now, with a pressure of 100 pounds per square inch, the contact patch is one square inch. This is true no matter how fat the tire.
I dont' think this is true. Just looking at my wheels while off the bike, a lot longer than one inch is touching the ground. That length will be the same for every tire of the same diameter. Multiply that length by the width of the tire actually touching the ground and you get the contact area for an unloaded bike. When you put your weight on it, that area is going to increase a little, but probably not by much. So a wider tire of the same diameter and pressure will have a larger contact area.

The ride quality may be better for the wider tire, and that's really all that matters.
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Old 07-09-05, 09:20 PM   #14
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If wider tires didn't have a larger contact area, then F1 and drag racers would not put those gigantic tires on the back of their car.
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Old 07-09-05, 10:45 PM   #15
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If wider tires didn't have a larger contact area, then F1 and drag racers would not put those gigantic tires on the back of their car.
You're forgetting about profile. A bicycle tire has a tall, round profile. A car tire has a low, wide profile. In the case of F1 cars, they also have suspension, which keeps the tire in contact with the ground while cornering. Comparing car tires to bike tires makes no sense.
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Old 07-10-05, 03:22 AM   #16
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Good point about the suspension.
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Old 07-10-05, 03:46 AM   #17
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If wider tires didn't have a larger contact area, then F1 and drag racers would not put those gigantic tires on the back of their car.
Much of that has to do with heating.
The larger the tyre, the less it will be heated up when driven hard. An over-heating tyre will degrade fast, so the larger the tyre, the better the ride, in those cases.
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Old 07-10-05, 09:41 AM   #18
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You can safely run that "85 psig" rated tire at close to 100 psig. The ratings are conservative, and have a large margin of safety, in my opinion. I ran my Electra Townie's tires 15 psig above rating at the recommendation of the LBS and had no problems. I run my Kona Dew Deluxe's 85 psig rated tires at 95 front and 100 rear with no problems (once I put in a good rim strip instead of the rubber "flat maker" that came in the rim). The higher pressure makes the tire MUCH faster, and seems to resist external puncture just as well or better as the sidewall pressure. Just my experiences...
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