Tire talk 23 vs 25

[Greatestalltime]

I do have really good roads here in Ky. Most of my routes have been very recently paved. I weigh 183 and the wheels are c-40 on one bike and c-24 on the other.

I guess I just got used to it, but I can’t stand when my pressure goes drops. I keep them at 120+. Maybe I’m losing something I don’t know about. When the pressure drops I feel like I’m bouncing around and losing power. Almost like I’m on a bike that’s flexing. I’m sure that’s not right, but that’s what I feel. So comfort isn’t a factor as I don’t like when the pressure drops.

I thought the c-40 were somewhat aero? Guess not.

I think I’ll do the 23 in front and 25 in rear.





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[Greatestalltime]

Im using 25mm tubulars on Bora wheelset, but on my Shamals (15C), definetely prefer 23mm Conti 4000 over 25mm.. I even ride sometimes attack/force tires (22mm fron/24 rear), and not finding them uncomfortable or something (on 4000 23mm and Shamals i rode few >200km rides in last two months).

Dont like 25mm because of bulbous shape, and instability feeling.. And dont need more comfort then 23mm provide me (i use Latex Inner tubes if that change something).. Those wheelset i ride on Alloy Frame (CAAD12), using Alloy Handlebar)....

Now that you mention it I think I do notice the instability much more so on the 4000s than the 5000s. Maybe because the 5000 are more true to size? I was thinking it was the grip. Maybe it was the tire width?




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[petromyzon]

I wouldn't worry at all about aero for the c24, forget it.
For the c40, the rim mould is 10 years old without an update. It's clear that Shimano are not interested in aero rim brake clinches. I'm sure it's better than the c24, but I've only seen one set of data that is very old now which compared the c24 tubular.
Technology has moved on a lot. The only alloy rimmed aero clincher I would buy is the Hed Jet with the non structural fairing.

Tyre pressure choice is very personal but there is good evidence to suggest that feeling fast is not the same as being fast, and unless you are 200 pounds 120 psi belongs on the velodrome

[3Pio]

Im using 25mm tubulars on Bora wheelset, but on my Shamals (15C), definetely prefer 23mm Conti 4000 over 25mm.. I even ride sometimes attack/force tires (22mm fron/24 rear), and not finding them uncomfortable or something (on 4000 23mm and Shamals i rode few >200km rides in last two months).

Dont like 25mm because of bulbous shape, and instability feeling.. And dont need more comfort then 23mm provide me (i use Latex Inner tubes if that change something).. Those wheelset i ride on Alloy Frame (CAAD12), using Alloy Handlebar)....

Now that you mention it I think I do notice the instability much more so on the 4000s than the 5000s. Maybe because the 5000 are more true to size? I was thinking it was the grip. Maybe it was the tire width?




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Possible.. I dont feel any instability (but oposite feeling), on my 23mm 4000 SII.. Never tried 5000 for now (i have another spare pair of 4000 in 23), but seem that 5000 are a bit narrower vs 4000, so maybe that bulb shape is less pronounced in 25mm

[CrankyCarbon]

I do have really good roads here in Ky. Most of my routes have been very recently paved. I weigh 183 and the wheels are c-40 on one bike and c-24 on the other.

I guess I just got used to it, but I can’t stand when my pressure goes drops. I keep them at 120+. Maybe I’m losing something I don’t know about. When the pressure drops I feel like I’m bouncing around and losing power. Almost like I’m on a bike that’s flexing. I’m sure that’s not right, but that’s what I feel. So comfort isn’t a factor as I don’t like when the pressure drops.

I thought the c-40 were somewhat aero? Guess not.

I think I’ll do the 23 in front and 25 in rear.

On long rides my tubular Vittoria Corsas / latex loose a bit of air. I noticed when it would "bounce" or "oscillate" in a way, so I know what you are talking about.

I've had to use about 3-5lbs more initial air in my front or give it a squirt of air halfway. I use 290tpi/butyl tubular in the back because I feel it provides a better platform for power than something about latex. Of course the rear butyl keeps air all the time. On my clinchers I use ultralite butyl tubes all the time and haven't ever had the same type of problem.

[Bigger Gear]

As others have said, the inner rim width is the real difference. The C24 and C35 are 15mm internal, whereas something like a modern Enve or HED Belgium Plus is 19.5-20.5mm. This changes how the tire feels as on the wider rim the tire will have a less rounded sidewall.

I have a set of Shimano C35 that I have used quite a bit since 2013. They are backup wheels at this point but I stil ride them from time to time. With a Conti GP4000 in 25mm I did not like the feeling in hard cornering or steep out of saddle climbing, but that tire is a very oversized 25mm and even on a 15C rim measures almost 27mm. For me I found the best tires on those wheels were Vittoria Open CX or now Corsa G in a 25mm. These are a more true 25mm and I liked the feeling in the corners much more. A Conti GP4000 in 23mm is OK on the C35 as well, but given that the ride of those wheels is already a bit on the harsh side compared to say a HED Belgium or Belgium+ rim wheelset, I found the plus ride of the Vittorias a better match.

If you are going to try a Conti GP5000 be aware that the sizing is much more accurate, that is a 25mm is much closer to a true 25 than the GP4000.

[Greatestalltime]

As others have said, the inner rim width is the real difference. The C24 and C35 are 15mm internal, whereas something like a modern Enve or HED Belgium Plus is 19.5-20.5mm. This changes how the tire feels as on the wider rim the tire will have a less rounded sidewall.

I have a set of Shimano C35 that I have used quite a bit since 2013. They are backup wheels at this point but I stil ride them from time to time. With a Conti GP4000 in 25mm I did not like the feeling in hard cornering or steep out of saddle climbing, but that tire is a very oversized 25mm and even on a 15C rim measures almost 27mm. For me I found the best tires on those wheels were Vittoria Open CX or now Corsa G in a 25mm. These are a more true 25mm and I liked the feeling in the corners much more. A Conti GP4000 in 23mm is OK on the C35 as well, but given that the ride of those wheels is already a bit on the harsh side compared to say a HED Belgium or Belgium+ rim wheelset, I found the plus ride of the Vittorias a better match.

If you are going to try a Conti GP5000 be aware that the sizing is much more accurate, that is a 25mm is much closer to a true 25 than the GP4000.

I’m currently on the 5000 on my 35(in 25mm) and 4000s on my 24s(25mm). It’s been a long time since 23’s and they were on 6700. I don’t think I noticed much handling when I switched, but I’m more In tune and experienced on my bikes.

I don’t like the bulbous effect, yet feel I do like the added air and possibly the contact patch. Though, as I said, my comparison to each was a long time ago.

I guess I’m going to switch both bikes to 23mm and see what I think at this point. And yeah I know I should’ve upgraded to a wider wheel, but really wanted the Dura ace reliability in the hub etc. I’ve had the 24s a couple of years and I will upgrade when I think the wife won’t notice.

The bottom line is I’m guessing and wanted opinions on if 25 are just too big for these 20.8 width wheels.






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[Bigger Gear]

I’m currently on the 5000 on my 35(in 25mm) and 4000s on my 24s(25mm). It’s been a long time since 23’s and they were on 6700. I don’t think I noticed much handling when I switched, but I’m more In tune and experienced on my bikes.

I don’t like the bulbous effect, yet feel I do like the added air and possibly the contact patch. Though, as I said, my comparison to each was a long time ago.

I guess I’m going to switch both bikes to 23mm and see what I think at this point. And yeah I know I should’ve upgraded to a wider wheel, but really wanted the Dura ace reliability in the hub etc. I’ve had the 24s a couple of years and I will upgrade when I think the wife won’t notice.

The bottom line is I’m guessing and wanted opinions on if 25 are just too big for these 20.8 width wheels.

Just one data point to add here, if/when you want to change wheelsets have a good look at something like DA9000 hubs laced to HED Belgium+ rims with Sapim CX-Ray spokes. Wide rims, relatively light, great handling and surprisingly aero for a low profile alloy wheel. Gram for gram, dollar for dollar my HED Belgium+ wheelsets are easily the best value of all the wheelsets I have in my collection.

[posaunemeister]

I'd stick with the 25mm tires and experiment with tire pressure to find the perfect feel.

[CrankyCarbon]

There's been a lot written about this.
23mm seems best for speed/comfort on 15C rims (the inside diameter).
25mm seems improves the comfort on 17C rims
but 25 on 15c is improved comfort but worse speed/handling as you are mentioning.

this excludes aero, pressures, etc.
I run 23mm Vittoria Corsa on Mavic Open Pros, which are 15C. I also only run 23mm on my older rims/wheels.
and I run 25mm Vittoria Corsa G+ on Fulcrum Competizione 17C

So those tests don’t have 25mm on 15c rims? Thanks I guess I missed that.

So I’m thinking I will go back to 23 until I upgrade wheels. I never thought the 23 were uncomfortable as actually like high pressure on either tires size-like 120psi plus


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there are articles / tests out there that do 25mm on 15C
this short article, near the bottom gives a brief description of the pluses/minus of each tire/rim setup
https://intheknowcycling.com/2016/04/03 ... eel-sizes/

A couple of my "normal" wheels are 23mm on 15C, though my newer wheels are 25mm on 17C
A lot of your selection is dependent upon variables not really "tested". If you ride on roads that are "smooth" then a "comfy" setup may provide no benefit on a larger tire/shallow rim; conversely if you ride on rough roads then the wider the tire the better for "comfort" ... that is, if you value "comfort" which can also depend on your weight, riding style and bike frame, etc.

[BigPoser]

People still ride on 23's?

[AJS914]

Tyre pressure choice is very personal but there is good evidence to suggest that feeling fast is not the same as being fast, and unless you are 200 pounds 120 psi belongs on the velodrome

Even if you are 200 pounds you don't need 120psi. I'm a 200 pounder and I ride 80psi on 25mm GP4000 (really a 27mm tire). If I were on smoother roads I'd go to 90psi.

OP, try 90-100psi if you are on smooth roads. OP consult this this blog post. You want your pressure below the breakpoint. 120psi is never faster on the road.

https://blog.silca.cc/part-4b-rolling-r ... -impedance

[Greatestalltime]

There's been a lot written about this.
23mm seems best for speed/comfort on 15C rims (the inside diameter).
25mm seems improves the comfort on 17C rims
but 25 on 15c is improved comfort but worse speed/handling as you are mentioning.

this excludes aero, pressures, etc.
I run 23mm Vittoria Corsa on Mavic Open Pros, which are 15C. I also only run 23mm on my older rims/wheels.
and I run 25mm Vittoria Corsa G+ on Fulcrum Competizione 17C

So those tests don’t have 25mm on 15c rims? Thanks I guess I missed that.

So I’m thinking I will go back to 23 until I upgrade wheels. I never thought the 23 were uncomfortable as actually like high pressure on either tires size-like 120psi plus


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there are articles / tests out there that do 25mm on 15C
this short article, near the bottom gives a brief description of the pluses/minus of each tire/rim setup
https://intheknowcycling.com/2016/04/03 ... eel-sizes/

A couple of my "normal" wheels are 23mm on 15C, though my newer wheels are 25mm on 17C
A lot of your selection is dependent upon variables not really "tested". If you ride on roads that are "smooth" then a "comfy" setup may provide no benefit on a larger tire/shallow rim; conversely if you ride on rough roads then the wider the tire the better for "comfort" ... that is, if you value "comfort" which can also depend on your weight, riding style and bike frame, etc.

That was a good article. I’ve read many articles with differing conclusions and opinions and countless forums/blogs on the subject.

What I’m taking from that is that 23c is faster(thought I read that which contradicts a lot of what I’ve read) and if comfort isn’t one of your factors go with 23c.

It also made it seem like 23c on a 15c wheel(which is what I have) is, by far, the best choice if, again, comfort isn’t your goal.

I know I’m oversimplifying, but my conclusion is I’m going back to 23mm(c) until I widen my wheels.

Thanks for the article


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[kgt]

My experience also agrees with the conclusions of this test-article.

[TobinHatesYou]

What I’m taking from that is that 23c is faster(thought I read that which contradicts a lot of what I’ve read) and if comfort isn’t one of your factors go with 23c.

...pinch-flat protection, cornering grip, etc. I can't imagine riding/racing on 23s. I've flatted out of two road races on 25s after hitting potholes and have yet to flat on my 28s and now 30s.