tyres 23's or 25

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  • Ginjafro
    Ginjafro Posts: 572
    Nickel wrote:
    slowondefy2 wrote:
    Ginjafro wrote:
    Right, I've checked this article out and worked out that the optimal tire pressures form my 23mm set up is 105psi/65psi Rear/Front. I've always had about 105psi in the back and 95 to 100psi in the front. I'll give 65psi a go and see how that performs.

    This!

    It surprised me how different the pressures need to be between the tyres, and how low the front tyre should be in comparison to the rear. It's made all the difference to my comfort.

    65 Psi?! Hello pinch flat!

    Today I dropped the front end to 65psi and went for a two hour spin around some crappy back lanes of Cornwall, which are more suited to a CX bike. No punctures or pinch flats, though in the last 3 years I have never had a flat on the road or on my commutes! I was quite sceptical about such a "low" pressure. However, the reality in today's experience was it definitely more comfortable. I did not notice any increase in rolling resistance and I was not any slower. It did have any detrimental effect on handling, braking or conering. I think the worry about "pinch flats" is unfounded. Lets face it if you give a 23c inflated to 65psi a good push or squeeze does it really feel much different to when its inflated to 95 or 100psi? Its still pretty hard. I detected a slight give which when my body weight (or at least 40% over the front end) is taken into account allows a bit of give. So, for the moment I am happy to continue keeping the front pressure down and comfort up.
    Giant XTC Pro-Carbon
    Cove Hustler
    Planet X Pro-Carbon
  • Sprool
    Sprool Posts: 1,022
    Bordersroadie wrote:
    Has the search function gone completely out of fashion? Or most people just want everything handed to them on a plate, more like.
    instead of throwing a little hissy, why not just post up the link to the other recent discussion on tyre size? really there is no need for this sarcasm on a helpful constructive forum like this.
  • Bordersroadie
    Bordersroadie Posts: 1,052
    Oops, slight overreaction, there. . .

    There've been plenty of good recent threads on this subject, and so many repeated threads could be avoided by a quick search, that was my point (which felt qute calmly made at the time, so no hissiness intended :0) ).

    Back on topic, I've been riding my winter bike for the last month and despite its higher weight by a kilo, it feels much more comfy and faster, due to its 25c vs the 23c of my summer bike. Strava times certainly haven't suffered. If I could fit 25c on the summer bike I'd make the switch, definitely.
  • declan1
    declan1 Posts: 2,470
    T.M.H.N.E.T wrote:
    Hoopdriver wrote:
    T.M.H.N.E.T wrote:
    Hoopdriver wrote:
    T.M.H.N.E.T wrote:
    Hoopdriver wrote:
    T.M.H.N.E.T wrote:
    Hoopdriver wrote:
    I would definitely go for the 25s. Better comfort and less rolling resistance in one package.
    Um. The 23's would be the lower resistance :lol:
    Um...no
    Go on. Please explain
    There has been a lot of scientific study into the rolling resistence of tyres by the big manufacturers, as well as a lot of recent and authoritative articles on the subject lately - notably in the Bicycle Quarterly in the US. There was also a long thread on this very topic on Bike Radar not too long ago. I am writing on an iPad and not inclined to write a long post on a touch screen, but if you look into it you'll find that is has been well establshed that rolling resistance is less for wider tyres (25mm tyres vs 23mm)
    Who would have thought that 2mm width difference was such a factor.Maybe we'd all be faster on tractor tyres then?
    Who knows? I weary of this. You could always use Google or try the BR search engine if you seriously would like to know more about the topic. There is plenty of stuff out there.
    I could and did. Nothing managed to quantify the difference 2mm makes to a tyres width.

    25s are faster because at the same pressure as a 23mm, the part of the tyre in contact with the road deforms less due to the wider tyre. This actually causes slightly less tyre to touch the road, reducing rolling resistance.

    Road - Dolan Preffisio
    MTB - On-One Inbred

    I have no idea what's going on here.
  • slowondefy2
    slowondefy2 Posts: 348
    declan1 wrote:
    T.M.H.N.E.T wrote:
    Hoopdriver wrote:
    T.M.H.N.E.T wrote:
    Hoopdriver wrote:
    T.M.H.N.E.T wrote:
    Hoopdriver wrote:
    T.M.H.N.E.T wrote:
    Hoopdriver wrote:
    I would definitely go for the 25s. Better comfort and less rolling resistance in one package.
    Um. The 23's would be the lower resistance :lol:
    Um...no
    Go on. Please explain
    There has been a lot of scientific study into the rolling resistence of tyres by the big manufacturers, as well as a lot of recent and authoritative articles on the subject lately - notably in the Bicycle Quarterly in the US. There was also a long thread on this very topic on Bike Radar not too long ago. I am writing on an iPad and not inclined to write a long post on a touch screen, but if you look into it you'll find that is has been well establshed that rolling resistance is less for wider tyres (25mm tyres vs 23mm)
    Who would have thought that 2mm width difference was such a factor.Maybe we'd all be faster on tractor tyres then?
    Who knows? I weary of this. You could always use Google or try the BR search engine if you seriously would like to know more about the topic. There is plenty of stuff out there.
    I could and did. Nothing managed to quantify the difference 2mm makes to a tyres width.

    25s are faster because at the same pressure as a 23mm, the part of the tyre in contact with the road deforms less due to the wider tyre. This actually causes slightly less tyre to touch the road, reducing rolling resistance.

    If you're running 23s and 25s at the same pressure, then at at least one of tyres is at the wrong pressure, which makes the comparison invalid.

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