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My used bike came with a 700x28 tire in front and a 700x23 tire in back. Should I leave the wider tire in front, or should I switch the tires? What benefits or drawbacks are there one way or the other? Is there any particular reason why the previous owner might have chosen non-matching tires? Is there any reason I should go out of my way to buy a new tire to make them match?

The found a little bit of information about tire sizing, but I still don't feel like I know what to do.

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Generally on a road bike it is considered better to run tires of equal size.

There are a few newer tires which are designed to run different sizes front and rear, but they are usually within 2 mm of each other. (Like the Continental Attack/Force combination)

I would consider a jump from 28c to 23c somewhat large.

That said, run the larger on the rear. The higher air volume will make for a more comfortable ride, and the narrower front tire will steer quicker, which makes for more reactive handling, and has a better aero profile, (which may or may not matter to you).

The comfort part will matter though, and I'd say that's a trump card.

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    I'd be lying if I said I noticed a huge improvement, but it's definitely not any worse. Thanks for the answer.
    – amcnabb
    May 8, 2012 at 16:11
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    You can run the 28 at a lower pressure than you had in the 23 when it was on the back wheel -- that will improve comfort.
    – tgdavies
    Jan 13, 2016 at 10:32
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    I disagree. You want more grip at the front so that at the limit it's the rear that starts to move first. "If the front slides you're probably crashing, if the rear slides you're probably not". You want a bigger volume at the front for coping with bumps, as the front is being pushed into them, where the rear is being pulled over (you can examine the difference this makes using a kerb and wheel-barrow).
    – Grimm The Opiner
    Sep 26, 2016 at 15:11
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    @zenbike I get that, but it means that at the limit - wherever that is - it's the front that will tuck first. Bad.
    – Grimm The Opiner
    Sep 28, 2016 at 10:17
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    Your argument assumes that there is an issue caused by the rear tire being larger than the front. In fact, if the front has sufficient traction, it will not let go, regardless of whether the rear is larger or smaller. In other words, if a 22c tire has sufficient traction for the front with a 21c on the rear, then putting a 24c tire on the rear does not change the amount traction for the front tire.
    – zenbike
    Sep 29, 2016 at 13:49
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If you have to make a choice, put the wider tire on the back. Generally there's more weight on the back, plus having the wider tire in front will make make steering more difficult.

(Most likely the previous owner had to replace one of the tires and just used what was available.)

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  • +1 for the rationale. That'd be my guess as well. LBS available stock makes for some strange bedfellows.
    – RoboKaren
    Jan 13, 2016 at 16:23
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Larger front tire for the win, its a trick messengers use. Increase braking power w/ out increasing as much weight as running both tires large.

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    Well if it works for them all good. I'd say the grippiest tyre should be on the front because its harder to recover from a front wheel slide, and the larger should be on the rear for weight support. Bike messengers won't be as heavy on the rear as the average rider.
    – Criggie ♦
    Nov 18, 2015 at 22:25
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    @Criggie For a road bike, the kind of friction (grip) we want from bike tires is static friction, which is independent of the contact area. Wider tires give more grip when we're on a loose surface, or sliding, and so are more use for MTBs. On a road bike, 99% of the time sliding the front tire is road rash time.
    – andy256
    Nov 19, 2015 at 3:25
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There are reasons to go with mismatched tires, but the previous owner may or may not have known these reasons. It could just be what was available as someone said.

That said, having the bigger front tire has some benefits and drawbacks:

Pro: A wider tire will have more grip, and this could make a difference in the wet under hard braking. Rubber pneumatic tires work more on adhesion than friction, and the rubber squeezes into the small voids in the pavement. If the surface were perfectly flat, it wouldn't matter what size your tire was, but a tire at lower PSI will engage more of these peaks and valleys and you can run a larger tire at lower PSI giving better grip.

Pro/con: A larger front tire will make your trail larger, and steering will feel more stable. "stable" could be replaced with "slow" or "sluggish" here, depending on how you like your bike to feel.

Con: A wider front tire has more of an aerodynamic impact than a wider rear tire. If your rims aren't pretty new, there's also little chance that their aerodynamics are optimized for a 28c tire so the impact would be significant, as far as wheels do impact your overall aerodynamics.

Pros/cons of a wider rear tire:

Pro: More comfort. Even at the same pressures a wider tire will usually absorb bumps better due to the increased air volume, but you can (and should) lower the pressure relative to what you'd run in the smaller tire. The rear tire, in my experience, has more impact on comfort than the front.

Pro: A rear tire is shielded somewhat aerodynamically, so its impact isn't as significant as the front, and it won't slow you down as much.

Pro: A rear tire will usually wear out faster than a front tire because of the force from the pedals going through it and the extra weight on the tire. A wider tire will have a longer wearing lifespan.

Con: Technically, your rear tire will have more grip possible than your front in cornering. Most crashes without a motorist involved have more to do with braking, however. Under braking, your front tire will always have more grip than your front, unless your tire is very big and your weight distribution is unrealistically low. This isn't likely to happen.

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I am running a 32c up front and a 23c in the rear in my single speed road bike. I commute a lot on rough roads and it rides a lot smoother.

So far it works great for me. I also remember in the old days we would run a fat tire up front and a skinny tire in the rear on our BMX bikes.

All I can say is the best thing to do is borrow a different sized tire or find an old one and experiment and if it feels right for you and go out and buy what works

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    Welcome to bicycles.stackexchange. It's great to hear about your experience,. but we really prefer to have reasons rather than only anecdotes. If you can edit your answer to say why that arrangement works and ideally what the pro's and con's of that rather than same-size of fat-rear setups are that would be great.
    – Móż
    Jan 13, 2016 at 10:11
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A wider wheel = more traction

Traction is important for torque and braking. Torque is driven through back-wheel and braking on both, and braking too much in the front relative to the back can result in the rider flipping over the handle-bar.

Therefore, put the wheel where it matters most, i.e. the back.

Edited in agreement with comment.

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    Most of your braking should be with your front wheel: bicycles.stackexchange.com/questions/6616/…
    – amcnabb
    May 14, 2012 at 17:11
  • Not sure if that is correct, but essentially, there is a ratio / tipping point at which any more front braking will result in a flip over. Having more traction in the front than the back will result in the rider being closer to that tipping point.
    – Yusufk
    May 15, 2012 at 9:37
  • Reading this ( stoptech.com/technical-support/technical-white-papers/… ), does support your point, because a riders weight is mostly on the back wheel. However, there is a tipping point, and having more traction in the front will result in a rider being closer to that tipping point.
    – Yusufk
    May 15, 2012 at 9:42
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    There's no way to avoid having the front wheel being apt to lock up and flip you. The width of the tire will make only a miniscule difference, since a front wheel basically never skids (except on very slippery surfaces) -- it either rolls or locks up. (The only logical "fix" for this is my "power brake" invention that no one has ever seen fit to build. ;))
    – Daniel R Hicks
    May 15, 2012 at 11:27
  • Yusufk, as you slow down, you automatically lose traction on your front wheel as your weight shifts forward. Most braking power comes from the front wheel. Until @DanielRHicks' invention takes off, the best way to brake is to primarily use the front brake but to be careful not to make it lock up.
    – amcnabb
    May 15, 2012 at 15:25

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