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Tire pressures

Discussion in 'V7/V85/V9 Chat & Tech' started by andyb, Jun 4, 2016.

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  1. andyb

    andyb Cruisin' Guzzisti

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    I'll go with the American spelling for the title - but want to ask about tyre pressures. Surprisingly the search did not come up with any other threads.
    The manual says 36/36 psi solo and 1 more psi dual. I have never had a bike with the same pressure in both wheels. More normal is something like 36/42psi.
    Has anyone tried different pressures?
    I have a Mk I Stone with standard tubeless Pirelli Sport Demon tyres.
    Thanks
    AndyB

    (If I retire my bike in UK it means I put it to rest or scrap it...in US I think it means it gets new rubber. Oh no, another dual meaning.....)
     
  2. sib

    sib Cruisin' Guzzisti

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    And if your bike becomes redundant in the UK, it means it's been retired, whereas in the US, it means you got another bike just like it.

    My '13 V7 and '16 V7II manuals say 36/36 one up and 36/38 with a passenger.

    CORRECTION: the recommended pressures with passenger are 38/38.
     
    Last edited: Jun 5, 2016
  3. john zibell

    john zibell Moderator Staff Member GT di Razza Pura

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    36 psi seems a bit high for the front. For years the older Tonti and small block recommendation was 32 front, and 36 rear. Unless you are running radials, I can't see a need for more than 36 psi in the rear for solo riding. Tire pressure is adjusted to control tire flex and tire temperature. Unless you flex enough to build up some heat, the tires won't stick well. I go for traction over mileage myself and tend to run slightly lower pressures.
     
  4. rob-mg

    rob-mg Just got it firing!

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    My 2016 V7 II manual says 2.5 bar, front and rear, for one up, and 2.6 bar, front and rear, for two up. The manual translates this to a rather overly precise 36.3 psi and 37.71 psi respectively.
     
  5. rob-mg

    rob-mg Just got it firing!

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    My understanding is that the pressures stated in the manual are jointly recommended by Pirelli and Moto Guzzi.
     
  6. andyb

    andyb Cruisin' Guzzisti

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    I think that the figures in the manual should be taken as a starting point rather than absolutes.
    I had assumed that the Pirelli Demon Sports on my V7 Stone were radials but the Pirelli web site says they are X-Ply.

    Intuitively I would think that the front should have a lower pressure as it carries less load.
    I run my BMW R100R Airhead runs at 42/36psi - on tubeless radials - and it is about 35kg heavier than my Stone.
    So 32 front / 36 rear as John says on the earlier bikes could be worth trying. It may also soften the front end a little when hitting bumps.

    I am sure somone else must have tried different pressures??

    AndyB
     
    Last edited: Jun 5, 2016
  7. sib

    sib Cruisin' Guzzisti

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    You are right, I mis-remembered, senior-itis, I've corrected my post.
     
  8. andyb

    andyb Cruisin' Guzzisti

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    100 miles today - 2 up - at 32 / 36psi - motorway and smaller roads - and I can not notice any adverse effects of the lower pressure in the front tyre so will leave it like that for the moment. No wobble at speed, no instability. The reduced front tyre pressure must make the ride slightly less harsh and give more grip, and in UK conditions help the tyre to warm up.
    AndyB
     
  9. rob-mg

    rob-mg Just got it firing!

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    Well either it does or it doesn't, not "must".

    The fact is, there is no groundswell of V7 and V7 II owners, or in fact any as far as I am aware, who have a problem with what Pirelli and Moto Guzzi recommend.

    And it is not true, as someone earlier suggested, who appears doesn't even own a V7 (happy to be corrected on this), that reduced tire pressure is just a matter of grip.

    Absent hard data, this just seems to be somebody saying, with no apparent credentials, and apparently not even knowing that the tires aren't radial, that he knows better than the engineers at Pirelli and Moto Guzzi.

    Next will be about how the Moto Guzzi engineers don't know anything about what oil to use.
     
    Last edited: Jun 5, 2016
  10. john zibell

    john zibell Moderator Staff Member GT di Razza Pura

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    Rob-mg, we once owned both a V50III, and a 750 Breva. 32 front, and 36 rear were the recommended pressures for the V50, and the little Breva. Also I've attended track schools, and seminars conducted by Bridgestone on motorcycle tires. Just for your information, maximum, traction is achieved when the core temperature reaches 100 degrees Celsius. However at those temperatures, a tire doesn't last long. Manufactures recommended pressures are suggested to give a compromise between wear and traction. In my opinion, the pressures recommended for the new small block bikes are on the side of more tire life, not more available traction. When I participate in a track school, I drop tire pressures 4 psi from what I use for street riding.
     
    Chris Malberg likes this.
  11. Wisconsin v7 Racer

    Wisconsin v7 Racer Cruisin' Guzzisti

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    I would like to hear what Todd recommends since I trust his opinion over what's in the manual and what the engineers at Guzzi recommend.
     
  12. rob-mg

    rob-mg Just got it firing!

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    In other words, despite offering an earlier comment in this thread, it's now clear that you don't own a V7 and never have.

    If you've been to tracks, you should know that track tires are constructed very differently from street tires. It is certainly not a matter of showing up with a street tire and dropping the pressure by 4 psi.

    There is nothing that you are saying that has any bearing on V7 tire pressure for the Pirelli Sport Demons, and with the greatest respect, your "opinion" appears not to be based on any experience, on a V7 or otherwise, with respect to these tires.
     
    Last edited: Jun 5, 2016
  13. andyb

    andyb Cruisin' Guzzisti

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    Rob-mg,
    The experience that John has on other (very similar) Guzzis - and on other bikes - is clearly valid and relevant to a V7, and rather than knock him it would be better if you could discussi the topic of this thread.

    I have had quite a few other bikes - Ducati MHR, 750 Sport, BMW airheads, Yamaha SR500, Triumph Speed triple - to name just a few - and as far as I can remember all have a lower pressure in the front tyre as it carries less load than the rear. The V7 seems the odd bike out for no logical reason and John's email about the 32 / 36 pressures in earlier small block bikes does make me wonder if the pressures in the manual are wrong. It does happen.

    And an over high front tyre pressure will give a harsher ride - which is what a lot of riders complain about.

    AndyB
     
  14. rob-mg

    rob-mg Just got it firing!

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    Andy,

    Go for it and when you're finished give us objective analysis, not "it must".

    If you look at comments on the V7 stock suspension, what you will in fact find out is that some people find it too harsh, some people find it too soft, and some (clearly a minority) find it just right.

    Your argument that this is a tire pressure issue has the merit of being original.

    Meanwhile, it is a plain ordinary fact that just about nobody, if anybody, has a problem with the pressure that Pirelli and Moto Guzzi recommend.

    And personally, I couldn't be bothered worrying about a .3 bar/4 psi difference.

    This is within gauge error for most people, apart from the few who use very high end gauges to measure pressure, and I sure doubt that it has much to do with complaints about suspension.

    But if you can demonstrate otherwise, with hard data rather than theoretical blue skying, I'm all ears.

    P.S. I happen to use a rather expensive gauge, said to be highly accurate, and it just reinforces my view that you are being anal retentive about this, and that the idea that minor tire pressure changes address issues that some people have with suspension has very little, if anything, to do with their complaint.
     
    Last edited: Jun 6, 2016
  15. GuzziMoto

    GuzziMoto GT Reference GT Contributor

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    Wow.
    I don't have a dog in this fight (I do have a V65 Lario, but it seems that is not relevant).
    But 4 psi is a massive difference and if that is within "gauge error" you are using the wrong gauge.
    John has a massive amount of experience with small blocks, and I would listen to him if I was in need of advice about a small block.
     
  16. GT-Rx®

    GT-Rx® Administrator Staff Member GT di Razza Pura

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    Guys, tire and oil threads in any capacity spiral downward fast.
    It's simple... less pressure means more grip and wear. I've raced on as little as 22 psi in near freezing air temps on radial tires. V7's mostly use bias-ply, so I'd never go that low personally, but people ride on less all the time when neglected.
    32-38 psi is about the norm, higher if your bike is heavily loaded (two-up, etc). Again, often neglected yet all is fine. I personally run 2 psi less in the fronts on my bikes, as racing has trained me to do so; 34/36 on the RentAGuzzi V7s with stock Pirelli tires. I bump those #'s up 2 psi when the bikes are ridden two-up.
    This thread is now locked.
     
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