700x23c or 700x25c

Discussion in 'Bicycle Mechanics and Repairs' started by Jacomus-rides-Gen, 10 Oct 2007.

  1. Jacomus-rides-Gen

    Jacomus-rides-Gen New Member

    Guildford / London
    Currently I am running 700x23c Michelin Pro2 Race tyres front and rear on my roadbike, I love the tyres but recently (after lots and lots of practicing) I am finding that I am getting the feeling that I want a 700x25c on the rear at least, or even run front and rear as 700x25c.

    The feeling that is causing this is that I can feel the rear tyre wanting more grip in corners. I have been practicing and practicing recently, and have taken a lot of kindly provided tuition from a couple of very experienced racers in my club. I have definitely reached the edge of my tyres performance in terms of how hard I can corner.

    I can feel the rear wheel scrabbling at the edge of traction quite often when I am really hammering, and have crashed one in practice when it slid from under me. Luckily my bodyarmour stopped me getting seriously hurt and I walked away with some road rash on my thigh and the need for a new torso+arms rig. and new knee pads. But I can't wear it on a long ride, because of the heat I generate inside it, so I want to stabilise the rear wheel if I can, by getting more grip.

    I weigh approx 73kgs in summer cycle kit.

    I have a few questions:

    1) Would putting a 700x25c on the rear (as one of the guys at the club who is VERY good suggests) help me wring an extra little bit out of the bike. I *feel* as though it would, but has anyone any experience? My gut feeling is usually very accurate, but I'm hoping someone has some experience before I lay down the cash!!

    2) If I fitted both wheels with 700x25c's would I notice an increase in rolling resistence. Or would this option allow me to get that little bit extra with virtually no ill effects to my rolling resistence?

    3) Should I just accept that I have reached the limit, I am now faster (when I want to be) through corners than nearly everyone I know, to the point where I have been asked how the hell I am doing it. Should I stop trying to push the envelope before I seriously hurt myself and be happy with what I've got?
  2. Membrane

    Membrane New Member

    I would question your belief that tyre width has an effect on traction (assuming correct inflation pressures), Sheldon Brown doesn't seem to think so: http://www.sheldonbrown.com/tyres.html#traction

    I'd say be happy that you are already amongst the best at taking bends.
  3. gkerr4

    gkerr4 New Member

    agree with above - you won't get any extra traction, comfort yes, but not traction. I have a train of thought that says you might actually get less as the taller profile of the 25 might lead to more distortion of the sidewall leading to the tyre squirming around under cornering.

    be careful too..
  4. John the Monkey

    John the Monkey Frivolous Cyclist

    Would it be worth picking up some cheap-ish 25c tyres and giving it a whirl?

    I ride 25C (Bontrager RaceLite XL) but I'm neither good, nor fast, and haven't ridden 23s, so can't really offer much other than that I, personally, like my tyres...
  5. Membrane

    Membrane New Member

    For a comparison to be valid the tyres would have to be the same make and model. For example a different rubber compound can have a very noticable effect on traction.
  6. alecstilleyedye

    alecstilleyedye nothing in moderation Moderator

    i'm thinking of putting 20c on the front of my winter bike, to give the front guard a bit more clearance. or should i stick to 23c at no more that 80psi?
  7. bonj2

    bonj2 Guest

    depends what roads you want to ride on. If it's mainly bendy, then probably good idea to switch. But realise that you'll go slightly slower (albeit not much) on the straights.
  8. Consider purchasing some dual compound tyres perhaps. The difference in rolling resistance between 23mm and 25 mm is so tiny that it would be impossible to measure.

    Each of the other factors unvolved, tyre construction, thread count, type of rubber, pressure etc are more relevant.

    Get some talc in your tyres BTW, it reduces friction between the tyre and tube allowing the tyre to better conform to the road surface, reducing rolling resistance and improving grip.
  9. Fab Foodie

    Fab Foodie hanging-on in quiet desperation ...

    I'd go with the latter,a 20c for winter bike doesn't sound nice to me.

    J-r-G, PR2's are more like 24mm than 23mm anyhow. If you are at the limits of adhesion with them, then you're going plenty fast enough! Good 25c's should not offer much greater rolling resistance, but it will depend on the tyre. PR2's are about as fast as a clincher gets, however a 25c will offer more air resistance at higher speeds and some extra weight to accelerate also, so you may find a 25c very very slightly slower at pace.
    I don't think grip will be greatly enhanced. Tyre pressure experimentation may help as will weight distribution on the bike.
    Some tyres might offer a softer grippier compound which may help.

    Hurtling down Ventoux at an average 40mph and some fairly hairy bends to brake into, I was pretty amazed at how grippy a PR2 is on a dry road...far greater than my bottle!
  10. domtyler

    domtyler Über Member

    Agree with Mickle, either dual compound or a stickier, softer single compound tyre, the trade off being less durability of course. OTOH, the new Conti GP4000S tyres have a new technology that they call Black Chili, this is basically the use of far finer carbon particles that they say increases grip by quite a large percentage while decreasing rolling resistance so maybe you could have the best of both worlds?

    I have these and they are certainly grippy although I haven't performed any quantitative testing.
  11. Blonde

    Blonde New Member

    Bury, Lancashire
    Agree with Dom Tyler - you might find there's hardly any diffrence in comfort between 23s and 25s, depending on which tyre you are swapping to. I stopped using Panaracer Pasalas in 25mm in favour of GP4000s 4 season in 23mm and because they are a more flexible (softer feeling) tyre - due to the greater number of threads per sq inch, I actually find them more comfy than my old 25s despite them being narrower. If you get good quality (ok, more expensive) tyres with a higher thread per sq inch count you'll notice more difference in comfort (and possibly lower rolling resistance) anyway and wont necessarily need a wider tyre. I find them just as P*nctur* resistant as the cheaper Panaracers and and easier to fit to my open pro rims. They actually seem to grip better too - I assume because of the greater flexibility in them
  12. OP

    Jacomus-rides-Gen New Member

    Guildford / London
    Thanks for all the replys everyone, you've definitely given me food for thought.

    As part of this practicing I have played with tyre pressures and have come to 100psi front, 110psi rear as my optimal pressures on these tyres.

    I tried GP4000-S tyres specifically because of the Black Chilli Compound that they were talking about, though I found them dissapointing and that they wore into a shoulder very quickly. So I moved back to tried and trusted P2R's.

    I think I will leave my tyres as they are and focus on being happy with my current pace.

    Thanks guys
  13. John the Monkey

    John the Monkey Frivolous Cyclist

    Makes sense, sorry for the red herring.
  14. domtyler

    domtyler Über Member

    Have you considered changing to tubs Jacomus? They are reputed to corner 'better' although I haven't ever ridden tubs so couldn't comment personally.
  15. OP

    Jacomus-rides-Gen New Member

    Guildford / London
    I have toyed with the idea, but unfortunately I'm back at uni for my final year at the mo. I was doing a years internship last year so all that lovely disposable income I lavished on my bikes all of last year has entirely dried up!

    I have come to the opinion that if I can get my hands on a 700x25 P2R for around £10-15 I will fit it to the rear and see what happens.
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