# 25 vs. 28 tires for Roubaix



## msg98 (Oct 27, 2011)

Hi,
i have roubaix sly and am considering going to wider tires. can you guys advise on whether to go all the way to 28 (do 28's even fit the roubaix sl3 frame/frork)? i don't care much about weight but would like to optimize comfort and puncture resistance. 
thanks

Mike


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## George M (Sep 25, 2008)

I have continental 4/ seasons 28 on my 2012 and I've also had them on my 2007 Roubaix.


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## msg98 (Oct 27, 2011)

does anyone have any good quantification on how much slower the wider tires are due to weight and (more importantly?) rolling resistance? 
Also, how does the specialized roubaix pro 25/28 tire work? -- what determines whether it's 25 or 28? 

thx


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## NealH (May 2, 2004)

The overall width, when inflated, is generally what determines the width.

On a 40km time trial, the 28 will probably be about a minute or so slower than a 25 - all else being equal. If you're not riding time trials, you're likely not notice any difference. In fact at lower speeds the 28 might even show less RR. But if you spend a lot of time at the front pulling your group, then its probably better to reduce the front time width. A good compromise is 25 front, 28 rear. 

At 70# the 28 will give you a nice ride on the greenway, and for general winter riding. But a 25 will too.


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## darwinosx (Oct 12, 2010)

Conti 28's work fine but Conti's tires are all narrower than they say they are. Google around and you can probably find the actually width of any tire you are looking for.
Also wider tires are NOT slower. This is old school thinking that's has been finally debunked once and for all recently and it's why so many wider rims and tires are being produced. Google that too.
I did get a good laugh out of the idea that they will be a minute slower in a 40 k time trial though because that is just ridiculous.


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## shanabit (Jul 16, 2007)

Specialized Armadillos will serve you well. Grab a set of 25's. If you flat Ill be shocked


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## George M (Sep 25, 2008)

The width of the 28s are 26mm.


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## aclinjury (Sep 12, 2011)

darwinosx said:


> Conti 28's work fine but Conti's tires are all narrower than they say they are. Google around and you can probably find the actually width of any tire you are looking for.
> Also wider tires are NOT slower. This is old school thinking that's has been finally debunked once and for all recently and it's why so many wider rims and tires are being produced. Google that too.
> I did get a good laugh out of the idea that they will be a minute slower in a 40 k time trial though because that is just ridiculous.


Zipp's TT wheels are just a tad under 25mm wide, but their own tires the Tangente which are designed to work with these wheel are either 21mm or 23mm wide, and they came to this conclusion based on their wind tunnel data. They do not make them in 25mm nor 28mm. The reason is because at high speed, rolling resistance is negligable compared to wind resistance. So unless the OP plans to roll along at 15 mph all day long on gravels or bad pavement, the 28mm will definitely be slower than the 25mm and 23mm, because at higher speed, wind resistance trumps rolling resistance by orders of magnitude.

Zipp - Speed Weaponry | Accessories | Tires | Tangente Clincher Tires


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## Stumpjumper FSR (Aug 6, 2006)

msg98 said:


> Hi,
> i have roubaix sly and am considering going to wider tires. can you guys advise on whether to go all the way to 28 (do 28's even fit the roubaix sl3 frame/frork)? i don't care much about weight but would like to optimize comfort and puncture resistance.
> thanks
> 
> Mike


How much do you weigh?


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## Stumpjumper FSR (Aug 6, 2006)

> The width of the 28s are 26mm.


Tire width will change depending on the internal width of the rims they are mounted on, my 25mm Vittoria's measure 28mm on SL23 rims.


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## Dunbar (Aug 8, 2010)

msg98 said:


> does anyone have any good quantification on how much slower the wider tires are due to weight and (more importantly?) rolling resistance?


If we're talking about the same tire rolling resistance goes down on the wider tires at the same pressure. Now most people drop the pressure on a wider tire so it's probably more of a wash. Wider tires have more aero drag but the difference between a 23 and 25mm tire at 30mph is 1-4 watts depending on the wheel and yaw angle. Realize that most of us would be putting out 500-600 watts to do 30mph and you can see how small the difference is. My suggestion would be to run a 25mm up front and a 28mm tire in the back. The rear wheel only has about 1/3 as much aero drag as the front wheel so the aero penalty is much smaller in the rear. My plan is to run the 25/28 combo on my Roubaix whenever Continental releases the 28mm GP4000S II.


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## msg98 (Oct 27, 2011)

Stumpjumper FSR said:


> How much do you weigh?



215 (6'6'')
thx


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## Stumpjumper FSR (Aug 6, 2006)

msg98 said:


> 215 (6'6'')
> thx


At your weight you could use either a 25mm or a 28mm tire, if you have stock wheels the tires should be close to the advertised width depending upon the brand of tire you use. A 25mm Michelin PRO 4 mounted on a Roval SL25 rim measures 25mm, the same tire mounted on a 24mm wide rim measured 28mm. I've mounted 30mm tires on my SL3 frame with no clearance issues. I would spend some time in the Wheels and Tires Forum Wheels and Tires and learn about tire widths / pressures and decide for yourself. I switched to wider tires a few years ago and would never go back to a 23mm tire, a wider tire at lower pressure (85f / 95r for my weight) is more comfortable and faster because the tire conforms to imperfections of the road surface, a narrower tire at higher pressure tends to bounce which actually slows you down. (unless of course you ride on a track or have perfectly smooth roads) Good Luck!


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## robt57 (Jul 23, 2011)

I put 27mm Pave Vit CGs on my 2005 Roubaix on wider rims, then soon after got a SL4 Roubaix and moved them over. Major Like!

Bigger than a Conti 28 All season, as are the GP4 in a 25 frankly. Not by much, but the All Seasons do run small where I find the GP4Ks do not. The Paves are a little weighty, but only time I really notice is riding with frisky guys and lots of accelerations. But after 3 hours how nice they ride has a good return on fatigue being less for me [maybe]. 

I am 210 and 6'1"ish and run the 27 paves at 80/85 or a little more when the frisky guys are around. If the frisk gets too frisky or I expect it to, I take my Scott with the 23/25 GP4k Chilies. A little less fatiguing after 2-3 hours of quicker riding to me. More about rotational weight I am thinking and lots of cumulative spin ups. Same pressures I run on the 23/25 GP4Ks ride almost as nice.. 

I also have some 25C Axial Pros laying about that fill out bigger than all these above on the wider rims, and ride as good as the Paves it seems like. Although I would say if you want to run higher pressures you may find the Pave the best up near/above 100 lb.

But as to 25 VS 28, if you have wide rims, most 25s seem to run out near 28 anyway. The GP4 AllSeasons are really a 24-6 it seems like.

I want to get some 25 Paves to run as fronts with the 27 as rears.
I started doing the 23/25 gp4ks on my Scott this year and like it a lot. And I run ultra light tubes in the front and reg tubes rear FWIW.


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