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Avon tyres... bummer...

Discussion in 'Norton Commando Motorcycles (Classic)' started by Fast Eddie, Jan 13, 2020.

  1. dobba99

    dobba99

    Joined:
    Jan 25, 2014
    Thats good info. Could i ask how wide is the tyre on that rim?
    Looking on the Avon website, the 120/80-18 roadrider isn't listed either. It would be more helpful if they listed how wide the tyres are on the different widths of rims they recommend.

    Many thanks
    Peter
     
    Last edited: Jan 19, 2020
  2. gortnipper

    gortnipper VIP MEMBER

    Joined:
    Nov 11, 2013
    116mm
     
  3. Fast Eddie

    Fast Eddie VIP MEMBER

    Joined:
    Oct 4, 2013
    According to Avon, the 4.00/18 is 116mm (when on a 2.5 rim) and the 120/80 18 is 120mm (when on a 2.75 rim)...

    265046C0-26DF-42B7-B01C-38EE8F86B772.png
     
    gortnipper likes this.
  4. gortnipper

    gortnipper VIP MEMBER

    Joined:
    Nov 11, 2013
    I misstated what I have. I actually have a 4.00/18.

    IIRC, it has pretty much the same rolling diameter as a 100/90-19 on the front.

    The pair handles well.
     
  5. Fast Eddie

    Fast Eddie VIP MEMBER

    Joined:
    Oct 4, 2013
    Gortnipper, they’re not similar... the 4.00 18 and the 100/90 19 have EXACTLY the same overall diameter at 671mm (when fitted to 2.5 rims)!

    That’s why I use them, it gives the closest to a 19 front and rear set up, BUT you get a dedicated rear tyre. Hence I got the hump when I thought they were no longer an option!

    By the way folks, the 120/80 18 mentioned on here has an overall radius of ‘only’ 652mm
     
    gortnipper likes this.
  6. Time Warp

    Time Warp .......back to the 70's. VIP MEMBER

    Joined:
    Dec 3, 2012
    They would be.

    The 4.00 / 18 has a 4 inch profile (101.6 mm or near 12 mm compared to the 90 mm profile of the 100/90%/19.
    Two times that is close enough to the one inch difference in rim diameter.

    Edit.
    Which suggests (There are a few mm difference at the profile) the height but not necessarily the thread profile/shape is somewhere similar.
     
    Last edited: Jan 20, 2020
    gortnipper likes this.
  7. gortnipper

    gortnipper VIP MEMBER

    Joined:
    Nov 11, 2013
    So no more 100/90-19 in the RR MK3 EH? Sigh.
     
  8. kommando

    kommando

    Joined:
    May 7, 2005
    In the RR MKII there is a 100/90 19, but like the previous range it is Universal not a dedicated rear so tread depth is lower. Eddie's image is not of the full range and missed out the Universal tyres.
     
  9. Matchless

    Matchless

    Joined:
    Dec 23, 2010
    What baffles me is how a so called 4" tyre can vary in width from one make to another. The Michelin tyre I mentioned previously measured 109mm/4.29" whilst the Avon I now have is 116mm/4.56". A BMW R100RS I owned was fitted with a Bridgestone 4.00 x 18" which, if I remember correctly measured 122mm/4.80". These were all on the same width of rim. WHY?
     
    Fast Eddie likes this.
  10. kommando

    kommando

    Joined:
    May 7, 2005
    From my previous post, the full range of Roadrider MKII/2 as listed on the PDF.

    If you send a query into Avon they will send you a PDF of the full range they plan to supply (I asked as a UK user, US may be different)

    Avon Roadrider MKII Front

    90/90-19 (replaces 3.00-19)
    90/90-21 (replaces 3.00-21)
    100/80-17 (replaces 3.25-17)
    110/80V17
    110/80-17
    120/70V17

    Avon Roadrider MKII Rear

    4.00-18
    120/80-18
    130/70V18
    130/70-18
    130/80-17
    130/80-17
    130/80V18
    130/90-17 (replaces 5.10-17)
    140/70-17
    140/70V18
    150/70V17
    150/70V18
    150/80V16
    160/80V15
    MT90-16* (130/90V16) (74V)

    Avon Roadrider MKII Universal

    3.25-19
    90/90-18
    100/90-18
    100/90-18
    100/90-19
    110/70V17
    110/70-17
    110/80V18
    110/90V18
    120/80V16
    120/80-17
    120/90-17
    120/90-18
    130/70-17
    140/80V17
     
    Fast Eddie likes this.
  11. Fast Eddie

    Fast Eddie VIP MEMBER

    Joined:
    Oct 4, 2013
    ... and equally baffling, with the exception of a few companies (like Avon) getting such information about ACTUAL widths and diameters is surprisingly difficult...
     
  12. worntorn

    worntorn

    Joined:
    Dec 22, 2006
    Some of those Universal tires have the same 7.5 mm tread depth as the dedicated rears.
    I wonder why Avon offers this on some Universal tires but not all?

    Glen
     
    Last edited: Jan 20, 2020
  13. Bernhard

    Bernhard

    Joined:
    Apr 20, 2011
    Different tyre company's have different tyre mould makers, there appears to be no universal standard, does the 4.00 x 18 come in 4 ply and /or 6 ply?
     
  14. Fast Eddie

    Fast Eddie VIP MEMBER

    Joined:
    Oct 4, 2013
    That’s a good spot Glen. I wonder too, because I was told by Avon (some time ago I confess) that the reason universal tyres don’t have the same 7.5mm tread as a rear is because the deep tread can allow the tyre surface to flex and effect the feeling and / or steering precision when fitted to the front.

    Whereas a rear tyre benefits from the deeper tread by allowing more miles, and the flex is not important on the rear.

    Therefore the tread depth on the universals was a compromise between the two needs of front end steering precision and rear wheel wear requirements.

    But in the pdf, some universals have 5mm, some 5.6mm and some 7.5mm...:confused:
     
  15. lcrken

    lcrken VIP MEMBER

    Joined:
    Mar 15, 2009
    Back in the '80s I tried a variety of 120 section 18" rear tires on my Commando race bikes. I had previously used several different 4.25 tires with no clearance issues. The 120 tires varied enough in actual width that some of them would clear the chain, and some would not. I recall the Dunlop tire dealer at Daytona one year using an electric wood plane to shave down the left side of the tire a bit so it would clear the chain. But some brands (Pirelli Gordons, for example) would fit with no interference. I think I was using 2.5" rims by then.

    I later moved the gearbox over to the left by almost 1/4" (.200" IIRC), which allowed me to use wider tires. I also had to modify the chain guard and space the left shock outboard a bit, was also using a home made swinging arm with more clearance, and had switched to 520 chain for 1/16" more clearance. There is enough difference in dimensions and settings on our 30 - 40 year old Commandos that some bikes will take the 120 tires more readily than others. It can also depend on how wide a chain is used. The heavy duty o-ring chains are significantly wider than the older original equipment styles. Clearance also depends on how far forward the tire is adjusted. I recall having to be careful to keep the tires as far back as I could for swinging arm clearance.

    Ken
     
  16. worntorn

    worntorn

    Joined:
    Dec 22, 2006
    The newish 530 xring Chains are narrower than the 530 O and X ring chains made just a few years ago.
    One can now use a narrow type 530sealed and regular 530 sprockets in many applications where a 520 sealed conversion would have been required 5 years ago.
    I have a 530x ring chain with rivetted M/L here that is identical in width to an old 530 unsealed.
    This is a fairly recent change.
    RK makes a gp530uwv x ring chain that has a pin width of just .89".
    It is specifically made for the classic bike market, where tire and gearbox clearance for an early sealed 530 chain was a problem.

    Glen
     
    Last edited: Jan 20, 2020
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  17. Matchless

    Matchless

    Joined:
    Dec 23, 2010
    That's good to know for bikes where no 520 (5/8" x 1/4") sprockets are available, as I have stopped using non sealed chains on most of the fleet. On the 920 I use a DID 520 X ring & it is superb needing virtually no adjustment.
     
    Last edited: Jan 21, 2020
  18. Matchless

    Matchless

    Joined:
    Dec 23, 2010
    Glen, I have just looked at the RK website & the chain you quoted isn't listed. Where did you get the listing from?

    Martyn.
     
  19. worntorn

    worntorn

    Joined:
    Dec 22, 2006
    Here's one.

    https://www.google.com/url?sa=t&sou...FjAAegQIAxAB&usg=AOvVaw17B5uHZRWiVrbr315Sykoe

    The DID VX530 is only slightly wider than the above chain and is a little easier to find.
    In the past it was standard procedure to change Vincent sprockets to 1/4" in order to upgrade to sealed chain.
    Most owners still go that route.

    I had a nearly new but already clapped out 530 unsealed chain on a Vincent here. The 530 sprockets looked good still so I tried the 530VX on there. It fit nicely.
    Aside from not having to find 1/4" sprockets, the big benefit is long lasting sprockets.
    With the reduction to 1/4" sprockets for the old sealed 520, the chain problem was fixed but now the wear rate went way up on sprockets.
    The 33% reduction in tooth area by dropping from 3/8" to 1/4" gives a 50% increase in tooth pressure.

    Glen
     
    Last edited: Jan 21, 2020
  20. 84ok

    84ok

    Joined:
    Aug 10, 2014
    afaik 5.0-16
     

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