700x23 v 700x25

happy_73

Looking at getting new tyres, have 700x23 at the moment but thinking of 700x25 for a little extra comfort. Much of a a trade off in terms of rolling resistance with going to 700x25?

ford2600

happy_73 wrote: »

Looking at getting new tyres, have 700x23 at the moment but thinking of 700x25 for a little extra comfort. Much of a a trade off in terms of rolling resistance with going to 700x25?

According to some studies rolling resistance can be less.

I have 28 on front with 25 on back, more comfort doesn't seem slower. Definitely helps in dealng with rough tar and chip surfaces, you can run lower pressures

godtabh

I've 25s for ride quality and stability. I like more contact with the road

alexanderomahon

Switched to 25 this year and am more than happy with the change and since change I have not had a speed wobble or grip issues.

outfox

I get the impression that increased rolling resistance associated with wider tyres has as much to do with tread knobbiness as width. I suspect that slick 25s or 28s wouldn't give much more resistance than 23s, and would definitely be a lot more comfy.

ford2600

outfox wrote: »

I get the impression that increased rolling resistance associated with wider tyres has as much to do with tread knobbiness as width. I suspect that slick 25s or 28s wouldn't give much more resistance than 23s, and would definitely be a lot more comfy.

Dermot Illogical I think posted an article before on tyre width. From memory the contact patch isno bigger with large tyres.
Slightly more aero drag but insignificant compared to drag from rider on hoods!

petethedrummer

Another in the 25 camp. Much nicer on dead Irish roads.

aFlabbyPanda

I switched from 23 to 25 recently and felt zero difference in terms of comfort. Rolling seems a little faster but I think that might be the tyres anyway regardless of size.

kumate_champ07

BrianjG wrote: »

I switched from 23 to 25 recently and felt zero difference in terms of comfort. Rolling seems a little faster but I think that might be the tyres anyway regardless of size.

are you inflating the 25mm tyres to the same pressure you previously inflated the 23mm tyres? if so that would explain that, use less pressure and the higher air volume of the 25's will give noticeable comfort

niceonetom

I can understand how wider tyre can yield lower cRR at the same pressure - you would have a contact patch of identical size but of a more circular shape which is more efficient than the sausage shaped contact patch of a narrow tyre.

What I don't understand is the claim that you can run lower pressures and still end up with a faster roll - is that just a question of giving back some of the gains gotten from going wider? ie allowing a larger contact patch (due to less PSI) but not do large that it rolls slower than a smaller, oblong shaped patch? Or is there another factor at play?

Anyway, the biggest change in road feel and comfort I've gotten this year was switching a from 19mm *rims* to 23mm, both with 23mm veloflexes and latex tubes - lush. I've just switched to 25mm GP4000Ss on the same 23mm rims and they're transformative. Magic carpet stuff though they are about 28mm wide so some might not have the clearance.

Now I just need to be convinced that they're not slower so I don't have to go back to 23mm tyres in the spring.

happy_73

Thanks lads, got the 25s. Changing from 23 schwable blizzard sports to 25 Gatorskins. Must change them over today so they're good to go for tomorrows spin.

alexanderomahon

Switching to Gatorskins!!!!! Now that is a different thread altogether.

happy_73

alexanderomahon wrote: »

Switching to Gatorskins!!!!! Now that is a different thread altogether.

Yeah kinda guessed that

Idleater

niceonetom wrote: »

Anyway, the biggest change in road feel and comfort I've gotten this year was switching a from 19mm *rims* to 23mm, both with 23mm veloflexes and latex tubes - lush

Agreed, I made this switch when I bought my climbing wheels 2 seasons ago and never looked back.
iirc, the argument posted above about wide (25) tyres being more aerodynamic is when in conjunction with wide rims. The airflow being wing shaped as opposed to bulbous.
Mavic even now fill in the gap between the tyre and rim on their to wheel tyre combo.

AstraMonti

niceonetom wrote: »

Now I just need to be convinced that they're not slower so I don't have to go back to 23mm tyres in the spring.

I don't think you need to worry about it, a 25mm makes more sense on our heavily uneven roads, especially on lower psi as the tire doesn't jump around and especially on a wider rim. On the other hand on a perfect track like mondello for example a 21mm tyre pumped on 130 might be faster, but that's just a logical (to me) assumption, but again how often do you race on a perfect road?

Bloch

I switched to 25s.

I'm 90kg and a pressure calculator told me my back tyre should be 145psi -- which was greater than the max. recommended pressure of my tyres!!

I suspect 23mm might be optimal for someone who weighs a lot less - maybe 75kg.

aFlabbyPanda

kumate_champ07 wrote: »

are you inflating the 25mm tyres to the same pressure you previously inflated the 23mm tyres? if so that would explain that, use less pressure and the higher air volume of the 25's will give noticeable comfort

Well I'm running 95 on the front and 110 on the rear which is less than what I used on the 23's but is it safer to go any lower and still avoid pinch flats?

lismuse

I'm on 25mm Continental Gator Skin Tubs .At 64 kgs I run them at 80 psi/front and 90 psi/rear. I have put 5k on them so far on west of Ireland roads without any punctures or any other issues. They are fitted to cheap Chinese carbon wheels (1100g/set) which climb like a goat and give great ride quality on the poor road surfaces around here. 25mm with lower psi is the way to go !

happy_73

BrianjG wrote: »

Well I'm running 95 on the front and 110 on the rear which is less than what I used on the 23's but is it safer to go any lower and still avoid pinch flats?

Was running 100 front and 110 rear on the 23s. Around the 80kg mark, what should I be running for front and rear with the 25s?

Thanks
S

ford2600

Bloch wrote: »

I switched to 25s.

I'm 90kg and a pressure calculator told me my back tyre should be 145psi -- which was greater than the max. recommended pressure of my tyres!!

I suspect 23mm might be optimal for someone who weighs a lot less - maybe 75kg.

You got calculator wrong it would seem.
It's weight per wheel.
For road bike redo calculation split 55%/45% back to front.
Assuming bike and accessories weigh 10kgs that's 55kg load for rear and 45kg for front.
100 psi and 90 at aguess for 25mm

happy_73

Ran the gatorskin 25s, front 95 and rear 105. Found them a bit more comfortable and if anything they rolled faster than the 23 schwable blizzard sports. Glad I made the change. One thing I will say, found them tough enough to get on. Bead not folding.

doozerie

niceonetom wrote: »

What I don't understand is the claim that you can run lower pressures and still end up with a faster roll - is that just a question of giving back some of the gains gotten from going wider? ie allowing a larger contact patch (due to less PSI) but not do large that it rolls slower than a smaller, oblong shaped patch? Or is there another factor at play?

This interview with Zipp's technical director touches on that topic:

The stuff we look at on the road is much harder because there’s real penalty to those high tire pressures in that environment. The human penalty of a rider getting shaken or struggling to maintain control, there’s handling, how much grip do you have how much grip do you need and then you also have the rolling resistance effect. If you’ve got a tyre at say 200 psi on the road you’re having to elevate the entire system over every bump, there’s a lot of energy required. You’re literally lifting the tyre off the road hundreds of thousands of times, so how do you dial that in to a place that’s more efficient. Then at the molecular level the rubber begins failing in ‘shear’, because the tyre has to make the contact patch that it has to make, if the surface is jagged and it only has so much area to make that contact patch, the tyre wants to fill over all the bumps and into the crevices you get these localized shear effects and you start breaking down the cross linking of the rubber and the tyres start getting hot, that energy’s gotta come from somewhere, so that’s a loss. I can tell when we go with the teams which mechanics and which guys have been doing that. You can see it in the tyres, the tyres that have been run at 160psi or 180 psi on the road they look like it, you get a lot of that micro cracking, micro circumferential cracks that start to run around the tyre and it almost looks like an old tyre that’s been in your garage for two years.Yet it’s a month old tyre that’s been used twelve times, that’s all that micro shear.

Zipp used to have something on their website too but I can't seem to find it now. It was basically the same as the above but with less emphasis on tyre longevity. I've seen online info from Zipp, dating from as far back as 2003, which says the same, so it's a long-held belief of theirs.

Separately, and also from Zipp (post #3), adjusting the pressure can be used to compensate for the different handling of a wider tyre:

Of these advantages, the air volume is one that brings added flexibility to your decision making, you can either take the added pinch flat/impact resistance at the prior pressure, or reduce pressure and take advantage of the greater comfort and what will likely be better grip at the same impact resistance...or some combination thereof. The steering/handling related pieces of this are interesting in that tires of different shapes, sizes and rubber compounds all respond differently, so it's hard to set a fixed rule. Generally, the shorter and wider contact patch makes the bike feel more lively under you as there is less resistance to steering inputs, in some cases and for some riders this can feel 'twitchy' or less stable because a shorter/wider contact patch has ability to damp/resist steering inputs than a longer narrower contact patch..in this case a lower tire pressure goes a long way in restoring the feel of the narrower rim. (Milliken and Milliken have written extensively about all of this regarding racecars and if you are into it, I highly recommend their book Racecar Vehicle Dynamics)

biketard

I'm a fairly recent convert to 25 mm tyres (last couple of years). Apart from increased comfort and better grip with no noticable speed penalty, I've also had a LOT fewer punctures.

Inspector Coptoor

I just swapped out the standard Giant Giant 700 x 23mm tyres for Gatorskin Ultras 700 x 25.


I'm 103kg. Have front at 100psi & back at 110psi:
Thoughts?

€40 each, saw them for €38 in halfords but wanted to give some business to LBS.

Put them on myself, bike mechanic I am not, but they were a lot harder to out on than the standard tyres.