23mm on front, 25mm on rear

[robjh]

I went into a bike shop while staying with friends, to pick up a new 23-622 tyre for my back wheel, but accidentally came out with a 25-622.
I was going to take it back, BUT don't live anywhere near this shop, and started toying with the idea of using the wider tyre on my back wheel while keeping a 23-622 one on the front. Thinking of it especially as I plan to be doing some short, lightweight audax-style touring this summer on this bike and carrying the extra weight over the back axle.

So the question(s) :
are there any handling or performance issues with having a 23mm tyre on the front and a 25mm one on the back?
Is it just a crazy idea?

For info the tyres are all Continental Grand Prix 3000 or 4000s.

 

[potsy]

No trouble at all to run that combo, they even sell them in a package like that 24's and 22's usually.

 

[Smokin Joe]

I had that setup on one bike for a few years, no problems.

 

[GrasB]

So the question(s) :
are there any handling or performance issues with having a 23mm tyre on the front and a 25mm one on the back?
Is it just a crazy idea?

Simple answer: Not really & no.

Not so simple answer: This gives you most of aero the advantages of narrower tyre while still taking advantage of the faster rolling that the 25c tyres give - given identical construction wider tyres roll faster (note that tyres which have a wide size range like the Schwalbe Durano have different construction once over a certain size, for this reason a 700x23c Durano rolls better than a 700x32c Durano!) however they aren't as aerodynamic, at a certain point the aero advantage of narrow tyres win over the rolling advantage of the wider tyres. The exact speed that this happens is dependent on all kinds of things not even to do with the tyre (eg. running say a 60mm deep aero rim will reduce the speed that a 700x23c wins on aero advantage)

 

[biggs682]

i regular ride bikes with no issue on differant width tyres so cant see a problem myself , but each to there own

 

[frank9755]

No problem mixing, but to maximise the relative benefits of each tyre you might want to consider putting them the other way round.
On my commuting bike I have a 25 on the front, to give a softer ride, and a 23 on the back, which carries most of the weight and hence accounts for most of the rolling resistance.

 

[frank9755]

Simple answer: Not really & no.

Not so simple answer: This gives you most of aero the advantages of narrower tyre while still taking advantage of the faster rolling that the 25c tyres give - given identical construction wider tyres roll faster (note that tyres which have a wide size range like the Schwalbe Durano have different construction once over a certain size, for this reason a 700x23c Durano rolls better than a 700x32c Durano!) however they aren't as aerodynamic, at a certain point the aero advantage of narrow tyres win over the rolling advantage of the wider tyres. The exact speed that this happens is dependent on all kinds of things not even to do with the tyre (eg. running say a 60mm deep aero rim will reduce the speed that a 700x23c wins on aero advantage)

You miss out tyre pressure! Narrower tyres are run at higher pressures which makes them deform less and run faster.

 

[GrasB]

You miss out tyre pressure! Narrower tyres are run at higher pressures which makes them deform less and run faster.

Bzz... wrong. I'm 170lbs on 23c/25c tyres (Durano plus) the optimal pressure is 85psi front & rear. If I take in a 1/2 mile stretch of slightly rough tarmac & do a run at a constant 190w I average 21.4mph on the optimal pressures above. at +10psi on that I average 20.8mph & at -15psi I average 21.0mph.

Oh running 700x25c tyres front & rear v's 700x23c equates to about 2w extra power saved at 15mph & about the same power used at 25mph on my road bike.

 

[HLaB]

As said rob, its perfectly reasonable I used to run that combo (23 front 25 rear) no problem until recently when the 23front became a rear and I got a new 23 front. I found the combo made no difference to speed but was slightly better for comfort.

 

[Smokin Joe]

Re the aero advantage of a 23mm tyre over a 25 -

Unless you are really, really fast and chasing a couple of seconds advantage in a time trial the difference will be bugger all.

 

[GrasB]

Unless you are really, really fast and chasing a couple of seconds advantage in a time trial the difference will be bugger all.

It was a club TT, not important in anyway except 2 middle of the pack riders wanted to prove something to each other & at the end of the 10 miles the difference was less than 1s between them. For both riders anything to find that extra 1s was important on that day.

 

[frank9755]

Bzz... wrong.

I don't think so...!
But off-topic and covered at length elsewhere, so let's not re-hash here

 

[GrasB]

I don't think so...!
But off-topic and covered at length elsewhere, so let's not re-hash here

Did anyone in the discussion actually look properly at what factors affect Crr? Because if you say that you have to believe that lifting the entire weight of a person up uses less energy than deforming a tyre.

 

[brockers]

Is it just a crazy idea?

The sky will fall in and the world will end.

Seriously though, Conti do their Attack/Force racing tyres as 22/24mm (pretty much a similar compound to GP4000?), so you wouldn't be the first person to have come up with this idea.

 

[robjh]

OK, thanks for all the responses. I'll give the 23-25 combo a try, and maybe swap them over front/back too and see if I notice a difference.