# 23mm tire on 25mm mm rim or 25mm tires on 20.5 rims - questions



## littlepitboy (May 26, 2013)

I currently have a Caad10 size 48
Current wheeelset Fulcrum Racing 5 with Conti GP4000s2 25mm tires

Last week I borrowed a friends 25mm wide carbon wheelset and another 23mm wide carbon wheelset - using my 25mm tires there were clearance issues. Tires hitting the rear brake caliper bec of thh added height

with 23mm tires both rim widths fit very well with generous clearance. 

i still want to get a set of carbon wheels. dilemna is if I should get 25mm width rim the get a set of 23mm tires... or just get a standard 20.5wide rims and use my current 25mm tires which has no issue...

Opinions pleae -

To add 1 more question would using 23mm tires on 25mm tires be better than 23mm on 23mm wide rims?

Appreciate the advice


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## robt57 (Jul 23, 2011)

What is your weight? And what tire pressures do you usually run on 23s, and what you looking to run in 25s.


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## littlepitboy (May 26, 2013)

robt57 said:


> What is your weight? And what tire pressures do you usually run on 23s, and what you looking to run in 25s.


I'm at 165lbs.. Tire pressure I use is 100psi on 25mm was the same when I was on 23mm


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## robt57 (Jul 23, 2011)

littlepitboy said:


> I'm at 165lbs.. Tire pressure I use is 100psi on 25mm was the same when I was on 23mm


Try 85 in the 23s and 75/50 [frnt/rear] with 25s. 

I am 210 and run 85/90 in 25-28s with no bad an all good.

That will allow the tire to be wider and lower and probably flat less IMO.
The lower pressures may just allow the height to clear the caliper. It will sure make for a nicer ride and no loss otherwise.


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## redondoaveb (Jan 16, 2011)

robt57 said:


> Try 85 in the 23s and 75/50 [frnt/rear] with 25s.
> 
> I am 210 and run 85/90 in 25-28s with no bad an all good.
> 
> ...


I'm sure you must have meant 75/80 on 25's not 75/50.


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## robt57 (Jul 23, 2011)

oops, yes...


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## littlepitboy (May 26, 2013)

thanks - actually 80psi on the rear allows the rear tires to fit the rear calipers with no clearance issues - 80 though felt soft...

is there a. chart where I can view weight/tire pressure recommendations?
also can anyone else answer my inquiry? about the rim/tire combinations?


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## rm -rf (Feb 27, 2006)

I now have *25mm rims*, HED Ardennes Plus, with 23c GP4000S tires. I use the same pressures that I did on my old rims with 25c tires, since they have comparable air volumes. 

I tried 25c on the 25mm wide rims, and it was a very plush ride. But the 23c tires on those rims is a smooth ride, too. And the 23c tires are a little lighter and a little more aero. The 23c setup seemed to have a little quicker response on sharp turns.

My first reaction was that wider rims would lower the tire profile. But measurements from HED don't support that idea. The only reason I can think of is that the wider base makes the sidewalls more vertical.

The diagram from HED:


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## rm -rf (Feb 27, 2006)

Air Pressures

At 170 lbs, I use front 80-85 psi, back 95-105. (Old rims with 23c tires: about 90-95 front, 105-110 back.)

I've seen different charts and formulas. They often don't agree, recommending quite a range of pressures for a given weight.

On my new rims, I ended up raising the back pressure a little compared to my old rims with 25c. It was still smooth enough and the handling was still good. So experiment a little and note the handling and comfort.

*Too high a pressure:* the ride is rough. I've seen comments that some riders do this because it seems faster. 

And for a tire+rim combination, higher pressures can have less rolling resistance, but roads need to be smooth. The theory is that the tiny bumps on rough roads make the bike+rider bounce a little, requiring energy. Absorbing the bumps in the tire itself is better.

But the tests also show that a wider tire at lower pressures has even lower rolling resistance, in most cases. 

*In a good range:* rough roads, like gravel over tar (chipseal) aren't as bad. Handling is still good. Cornering is better than at high pressure, since the tires don't bounce as much.

*Too low:* more likely to get pinch flats on potholes or RR tracks, etc. Steering seems slower / mushy. Rough roads are even smoother.


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## robt57 (Jul 23, 2011)

littlepitboy said:


> thanks - actually 80psi on the rear allows the rear tires to fit the rear calipers with no clearance issues - 80 though felt soft...


I am a sprinter, not that this happens much anymore. But I can say that is the only neg I have found with below 85 in the back. A lot of out of the saddle pedals turns in anger I feel tire mush.

Also, your bike/frame can make a difference where in the pressure window a given tire/rim combo works.

Example; SL4 Roubaix VS 2005 Roubaix [have both] The SL4 is so stiff I find the lower side of the window is preferred. The 2005 on the other hand I tend to go like 10 more. same tires, just what i find.


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## littlepitboy (May 26, 2013)

Thanks for the inputs but can someone answer question below?

23mm wide tire on 25mm rim or 25mm or 20.5mm wide rims?

Which would be a better option.. 
Or what would you run?


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## ziscwg (Apr 19, 2010)

littlepitboy said:


> Thanks for the inputs but can someone answer question below?
> 
> 23mm wide tire on 25mm rim or 25mm or 20.5mm wide rims?
> 
> ...


23 tire on a 25 rim

The wider rim makes for a better contact patch. It will be more aero, but unless you are doing TT or centuries, would not worry about that too much.


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## mikerp (Jul 24, 2011)

littlepitboy said:


> Thanks for the inputs but can someone answer question below?
> 
> 23mm wide tire on 25mm rim or 25mm or 20.5mm wide rims?
> 
> ...


My quick analysis and suggestion based on your info I'd go with the 23's.
No sense in going with the 20.5, you can make the 25's work but you aren't really using them as intended, some marginal issues with using them. 23's work all the way around for you.


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## bubba117 (Aug 20, 2012)

littlepitboy said:


> Thanks for the inputs but can someone answer question below?
> 
> 23mm wide tire on 25mm rim or 25mm or 20.5mm wide rims?
> 
> ...


I would do the 23mm tire with a 25mm rim. the wider rim promotes a large contact patch while cornering and will allow you to run lower pressures with less pinch flats.


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## littlepitboy (May 26, 2013)

bubba117 said:


> I would do the 23mm tire with a 25mm rim. the wider rim promotes a large contact patch while cornering and will allow you to run lower pressures with less pinch flats.


great thanks!!!


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## Reacto (Jan 8, 2017)

Hi!

I have a 23mm width tubular rim, wich tyre faster with my rim 23mm or 25mm?

Thanks!


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