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I am currently running Continental Grand Prix S 4000 in 23-622 / 700x23C front and rear. I am about to buy a new set of tires for my road bike and am fancying a smaller tire for the front and a wider tire for the rear. Actually Continental offers such tires as a set (GP attack and GP Force). Also note, that Motorcycles usually have a wider rear tire to support quick acceleration but still have dual disk brakes in the front to maximize brake force.

I tend to ride fast in a traffic situation where the majority of bikes travels slower. So I am often underestimated and have to brake sharply. While panic braking my bike tends to pulling, which I have learned to manage. I suspect a wider tire to reduce pulling, by developing more grip in low load situations. The weight balance gets shifted to the front, when breaking sharply and therefore the front tire does not skid even with much break pressure. The back tire on the other hand does only carry little weight and skid with the same brake pressure applied.

I am also facing periodical flat tires with a frequency of 1 per 10 weeks or so on the rear tire. I suspect a wider tire to pick up fewer glass splinters, by reducing the pressure. The rear tire carries the main load while non-braked riding and a wider one distributes the force to a bigger surface area thus reducing the pressure.

Update

Thanks for all the input. Your answers have helped me a lot in finding my decision.

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    Some of what you say has validity. However, remember that the front brakes have about 75% of your overall braking power, due to weight distribution. And to prevent flats use Kevlar belted tires.
    – Daniel R Hicks
    Commented May 19, 2012 at 1:24
  • The front tire has higher contact pressure, while breaking, why I suspect a narrower tire to be able to carry the developing forces as well. I think, I will get a 20-622 Continental Grand Prix for the front. For the rear tire I could get the Grand Prix 24mm, which has two layers of polyester and was tested to be very puncture proof, staying with Continental, as the Grand Prix 4000 are already Kevlar belted.
    – Bengt
    Commented May 20, 2012 at 20:34
  • I'd also recommend you work on your braking technique. "Move arse backward" is pretty much all you have to do, to put your center of mass backwards. Don't catch your lower torso with the rear edge of the saddle through - that's too far down and will do you mischief in an accident.
    – Criggie ♦
    Commented May 2, 2016 at 10:22

4 Answers 4

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I'm currently running the Conti Attack/Force combo on my road bike. I have previously run both the GP 4000, and the Schwalbe Ultremo ZX on the same bike.

The concept behind the Attack/Force is that the slightly wider (24mm) rear tire will allow just a bit more comfort, and the slightly narrower front tire (22mm) will be a touch lighter with more reactive handling.

I feel a difference in comfort, but I can't say the handling was noticeably different. Of course, the GP 4000 was pretty stable to begin with, so maybe that's a good thing that I don't notice a change.

They do feel a bit more stable in a corner, and I feel like the rubber compound is a bit stickier. They say it's the same Black Chili compound used on the current GP 4000, so maybe that's psychological.

I can say that the comfort aspect is worthwhile, and there is nothing I have bad to say, so why not try them. A set (here, at least) is the same price as a set of GP 4000's. No loss, at least, and a bit of gain on the comfort side.

@DanielRHicks commented that you might need to worry about braking power or traction. I've had no issues with braking performance, and these are a pro peleton tire. I don't see any issue there. I've also had no issues with flats on the tires, but then, I didn't have with the GP 4000 either.

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    I wasn't saying "worry about it", I was just saying that the wider rear tire will not improve braking.
    – Daniel R Hicks
    Commented May 19, 2012 at 11:13
  • @DanielRHicks: Sorry, I didn't mean that to sound negative. I apologize if it did. I just meant that you brought it up as a possible issue/thing to be aware of, etc....
    – zenbike
    Commented May 19, 2012 at 11:26
  • Thanks for your impressions on the Attack/Force. For the rear at least they are not puncture proof enough for me, as they are pure racing tires. For the front I will reconsider the Attack, because a Grand Prix in 20-622 might be overkill.
    – Bengt
    Commented May 20, 2012 at 21:11
  • @zenbike You basically say "yes" based on your experience with the Attack/Force combo, so I will accept your answer.
    – Bengt
    Commented May 20, 2012 at 21:16
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Motorbikes have larger rear tyres in order to allow the 189bhp (in the case of an R1) which is significantly more than most cars (twice mine infact) the twin brake calipers on the front is about the weight distribution under breaking (it all goes forward) and cooling, and pull (to one side) It common on MTB to run a larger front tyre than rear, better front grip, and no way are you going to spin wheels due to lack of grip

I would not expect a change of a few mm to make any difference to your breaking performance, and the contact are, is a fraction of the carcase width, so I don't think puncture resistance would be improved, infact by running lower preasures, i would expect a larger contact area AND snake bites

Bit along with all things like this, try it and see if it works

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    I can not imagine a single disk brake to cause pull to one side, as the axis is stiff and will translate the torsional moment to the other side of the fork, decelerating the tire symmetrically. As one can see from single sided forks, what matters is if the center of decelerating force (the tire center) and the center of kinetic force (mass center of the bike/biker) align.
    – Bengt
    Commented May 20, 2012 at 20:55
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    Are there any examples of motor bikes using single sided forks ? Yes on MTB because the weight and forces are not as great, just didn't think they did it on motor bikes, as for the axel being stiff, even in MTB under lower loads it is a recognised issues hence the move from QR, to 15 and 20 mm bolt throughs which still have not eliminated the issues, Cannondales single sided mountain bike fork eleminates the isses by not being round inside (required to run on bushes) and running on roller bearings, hence the hight price
    – spacemonkeys
    Commented May 22, 2012 at 5:55
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More rubber touching the road means more drag, which will probably help with braking.

Just think if you will want to have that extra drag against you when speeding vs the extra drag for you when braking.

And keep in mind what daniel said in the comments. most of your braking is in the front. so changes in the front wheel will make more difference for panic braking. maybe a wider front and slimmer rear is what you are really looking for.

I'd go for a lighter bike as it will help both cases. Less mass moving, less inertia to break against. Great excuse for an all carbon shenanigans :)

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  • In my case the additional drag when speeding is not as much of an issue, as I do not drive long streaks and reach top speed seldom, only. Also my health is at stake when breaking and my time is at stake when speeding, so the balance is quite clear for me. Perhaps there is no other way of increasing brake performance than to go with a wider front tire and handle the pulling. I think, I will get two tires of different widths and try it out. A lighter and more expensive bike is not possible as I have to park at public places and do not want to increase the potential of my bike getting stolen.
    – Bengt
    Commented May 20, 2012 at 20:26
  • @user906658 please do report back if you do the two tire trials. i'm curious as hell now! :)
    – gcb
    Commented May 20, 2012 at 20:49
  • Thanks for your interest. I will summarize my findings here, when I tested the new tires.
    – Bengt
    Commented May 20, 2012 at 21:22
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Wanting different widths front and rear prevents you from the most effective way of changing tires: when the rear is worn out, move the front one to the rear and put a new one on the front wheel. This way you always have the most reliable tire at the front, and you never have to replace a non-worn-out tire due to ageing.

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    Tyres are wear items - when they're worn out, replace them. Fronts generally wear slower than rears, so you buy them less often. There's nothing to be gained by moving a part worn tyre to the rear wheel.
    – Criggie ♦
    Commented Apr 25, 2019 at 9:07
  • "[Y]ou never have to replace a non-worn-out tire due to ageing." Nor do you if you just replace each tyre when it wears out. Unless the bike is so rarely used that no amount of tyre rotation is going to change that.
    – David Richerby
    Commented Apr 25, 2019 at 11:15
  • My experience disagrees - my front tires show virtually no wear after many thousands of km, while the rear is worn to the canvas. Sheldon sort-of agrees with me (sheldonbrown.com/tire-rotation.html).
    – Marjan
    Commented Apr 26, 2019 at 11:08

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