My journey to the darkside is complete… do i really put 100 psi in the tyres?

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  • My journey to the darkside is complete… do i really put 100 psi in the tyres?
  • Premier Icon cloudnine
    Subscriber

    Put some conti GP 4 seasons on my cx bike the other day.
    Have been doing mainly road miles on some cx tyres and decided i could be going a bit faster. Head scratching moment of do i really put that much pressure in the tyres?? It goes against all my tubeless 23 psi instincts.

    Premier Icon wwaswas
    Subscriber

    I tend to stop at about 80 or 90 on my road bike.

    It all gets a bit skittery and my fillings fall out if I go above that. It is faster, mind.

    Depends on your weight. I put 120psi into my conti GPs but then I am a 6ft 2 inch gorilla!

    asterix
    Member

    80 or 90 in the winter but 110 when its dry and time to race

    aP
    Member

    Potentially yes. Dependant upon tire size and your weight.
    You can of course put 25psi in them but you won’t go very far, very fast or make it round corners.

    120 rear and 110 front, slightly less when it’s frosty/cold.

    bencooper
    Member

    140psi in my recumbent – speed 😉

    TiRed
    Member

    Depends on the width of the tyre and your weight. For 23c and a 70 kilo rider you will need 100/110 PSI front/rear. For 25c this falls to 90/95.

    There are lots of formulas for the optimal tyre pressure for load and width, that minimize rolling resistance depending on surface. If you ride on a poor surface, lower pressure wider tyres, correctly inflated, will have lower rolling resistance.

    Premier Icon FuzzyWuzzy
    Subscriber

    Depends on your weight and the tyre size but most people put too much pressure mistakenly believing it’s faster when in fact it’s just less comfortable. At 90kg on 25’s I’m 85ish front 90ish rear (give or take 5psi on both as I’m not overly anal about it).

    80 or 90 in the winter but 110 when its dry and time to race

    ^ Is about right.

    retro83
    Member

    Use this to see what pressures you need:

    http://www.bikequarterly.com/images/TireDrop.pdf

    I run 75 on the front, 110 on the rear. Works a lot better than equal pressure in both IME.

    I can’t remember who linked me to this, but it’s really useful so thanks whoever it was!

    bikebouy
    Member

    I use GP4’s and weigh 78kgs at the mo’, pressures 105 on the front 110-115psi on the rear.
    I don’t change whether its wet or dry but some mates do.

    Premier Icon cloudnine
    Subscriber

    They are 28C and im about 62kg. I put about 80 in them and was expecting an explosion. Amazing the difference between them and cx tyres comfort wise. Thanks for the link 8)

    Premier Icon njee20
    Subscriber

    I can’t remember who linked me to this, but it’s really useful so thanks whoever it was!

    So they reckon 40:60 weight distribution on a road bike, so that’s 28kg on the front wheel for a 70kg rider, so 65psi… no thanks!

    asterix
    Member

    75 on the front

    at such a low pressure doesn’t your front tyre start to “squirm” when cornering fast?

    Premier Icon Yak
    Subscriber

    I’m about 65kg and go 95/105 psi front/rear on 23c.
    Tried higher but it feels skittish. Sometimes go lower for bad weather, but have no proper evidence that it is more grippy. Its just that ” oooh, its a bit frosty, i’ll let a few psi out” habit.

    edit – think I started from some Michelin chart somewhere then adjusted a bit after that.

    MrSmith
    Member

    Most people over inflate thinking it makes them faster, it doesn’t unless the surface is billiard table smooth ( get down and run your hand over Tarmac and feel how rough the surface is) it’s carcass deformation that gives you grip and lowers rolling resistance.
    70kg 23or24c 75psi front 90rear

    asterix
    Member

    have no proper evidence that it is more grippy. Its just that ” oooh, its a bit frosty, i’ll let a few psi out” habit.

    well if its slippy out and the pressures are too high, then you can feel the tyres, erm. slip when cornering or climbing. I have occasionally had to get off on hills because the rear wheel was spinning underneath me

    bigG
    Member

    109 psi all year round in both winter bike and summer bike. Never found that I lack grip on either.

    Premier Icon cloudnine
    Subscriber

    109 sounds like it might loosen my filings!!
    Maybe the idea is that you grit your teeth and pedal faster so they dont rattle loose.

    80/90 but then I run tubeless

    110psi, but I’m 98kg and I think that was a rating on the rims not the tyres!

    Premier Icon Northwind
    Subscriber

    I found mine faster with less, always ran around 80psi- maybe more outright rolling resistance on smooth roads but quicker on lumpier surfaces. Mind you I weigh nothing.

    109 psi all year….Never found that I lack grip on either.

    I’m sure you have but you do have more grip with less psi.

    rusty90
    Member

    The call of the road is obviously strong at the moment – just put 28mm GP 4 seasons and larger chainrings on my Guerciotti at the weekend. At 70kg I’m running them at 95 rear, 90 front, which seems the best compromise between zing and comfort. Brought back fond memories of crisp mornings at the TT start with Clement No. 5s at 120 psi 🙂

    whatnobeer
    Member

    80/90 but then I run tubeless

    Same here, when I ran 23c ProRace3’s with tubes I ran 90/95. I’m 63kg. No point in running higher than that for me with the quality of roads around here and my weight.

    I’ve never run 28c tyres but I’d reckon 100psi would be too much unless you’re a very big bloke.

    retro83
    Member

    njee20 – Member
    So they reckon 40:60 weight distribution on a road bike, so that’s 28kg on the front wheel for a 70kg rider, so 65psi… no thanks!

    No, it’s bike + rider weight, and the 40:60 is just a guide line. Yellow pages under the back wheel, then scales under the front and sit on the bike; then swap to get an accurate ratio.

    70kg rider + assumed 7kg bike on 23 mm tyres = 70 front / 105 rear.

    Don’t write it off without trying it.

    asterix – Member
    at such a low pressure doesn’t your front tyre start to “squirm” when cornering fast?

    Not that I’ve noticed. It gives the same effective squish on your front and rear tyres. Without carrying the track pump and trying a corner at e.g. 100/100 and 75/110 I don’t think you’d readily notice.

    The main difference I have noticed is that the front wheel grips so much better and doesn’t skip over small bumps, and the rear wheel never bottoms out.

    Works for me anyway. Nothing to stop you adding 10% to those figures, but according to the article, that’s the optimum balance between the amount of squish for the tyres to work properly over bumps and roll fastest.

    mrblobby
    Member

    So they reckon 40:60 weight distribution on a road bike, so that’s 28kg on the front wheel for a 70kg rider, so 65psi… no thanks!

    Sounds pretty crazy. Anyone actually run their bikes like this?

    Am intrigued though. May get the powertap out and do some testing.

    Gary_M
    Member

    120 rear and 110 front, slightly less when it’s frosty/cold.

    I’m 70kg and that’s how I roll.

    I just use a fiddle around and see what feels right method.

    I doubt pressure gauges are *that* accurate or consistent, especially between different pumps?

    MrSmith
    Member

    http://www.bikequarterly.com/images/TireDrop.pdf

    70kg riders with 100psi 😯 you need to look at the chart in the link above.

    mrblobby
    Member

    70kg (on a very good day!) and 100 psi on 23mm here. Been out with a lot less pressure in the tyres having forgotten to check before going out. Tends to feel slower, but probably because the ride is less harsh. May need to do some experimentation.

    110kg here 100 front 120 rear. It’s like riding a penny farthing with iron hoops.

    Premier Icon mikewsmith
    Subscriber

    about 100 as it’s a round number and never had issues with grip etc. but then again I’m probably in the 4th tier of STW roadies….

    brakes
    Member

    ^^^ same here, 100 is an easy number to hit, plus my track pump is knackered so I doubt it’s very accurate. even when it was new it can’t be that accurate anyway.
    over a week my tyres go down by 10-15psi so are between 85 and 100 psi depending on when I last pumped them up. anything less than 80 psi just feels weird.

    and remember for that ‘calculator’ it’s rider + kit + bike.

    EDIT: why does a randonneur have more weight over the front than a racer?

    TheDoctor
    Member

    Continental recommend 110 for 23c and 95 for 25c

    Premier Icon cookeaa
    Subscriber

    Continental recommend 110 for 23c and 95 for 25c

    Does in not also depend on the weight of the meat sack sat on top?

    Haze
    Member

    Chart has me at 75/110.

    I don’t get too precious about it, normally put 100 in each and top up periodically.

    asterix
    Member

    but the footnote to the chart also implies that the optimum tyre pressures depend on the springyness of the frame. Higher pressures for a springier frame

    Premier Icon wwaswas
    Subscriber

    Higher pressures for a springier frame

    how on earth do you measure the springiness of your frame.

    we’re all sat here worrying about 5psi either way on tyre pressure but no objective way of measuring spring in a frame.

    asterix
    Member

    I don’t know how to measure it – its just what the chart says.

    I only brought it up because I am in the process of buying a rather springy carbon road bike

    bikebouy
    Member

    I have a Cervelo R5 which is quite “springy” and run GP4’s at 95 front and 110-115 rear.
    I also have a Parlee Z4 which is solid as a rock and run again on GP4’s and …yes you guessed 95, 110 as before.
    I do change the wheels though and Mav R-Sys which are light climbing wheels feel better at this psi, I’ve some carbone 40mm aeros and again run psi’s at the above.

    I ride SOuth Downs lanes and they are full of potholes and shagged out surfaces..

    What a bunch of twatbags….stop talking in bloody PSI, I don’t understand it!

    60kg, 9 bar in the front 10bar in the back! I really really need to experiment with lower pressures!!

    Premier Icon wwaswas
    Subscriber

    I really really need to experiment with lower pressures!!

    Take those bars out and put some air in them instead?

    asterix
    Member

    60kg, 9 bar in the front 10bar in the back!

    man alive! – your off the chart!

Viewing 45 posts - 1 through 45 (of 57 total)

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