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Wheel slip on dry pavement

Discussion in 'Norton Commando Motorcycles (Classic)' started by worntorn, Mar 29, 2019.

  1. worntorn

    worntorn

    Joined:
    Dec 22, 2006
    I've been riding this bike for 15 years now and it still surprises me now and then.
    For a boring old MK3 slug it seems to have a lot of grunt.
    Yesterday on one of my favourite twisty sections the back end stepped over about a foot on acceleration out of a corner. I've never had it do that before.
    This is a very twisty road. Leaned right over I can get thru the uphill corner in question at about 45-50 mph. 3rd is a little high for it, so second was the choice.
    My first thought was that there must be sand on the road, so I went back and checked. Its dry clean pavement, no sand.

    Ran thru again and again it stepped over and did the same on the next 2nd gear corner.
    I guess I don't use second gear on corners very often, will have to show the old girl some respect and maybe stop jamming the throttle open like that!

    Glen
     
  2. concours

    concours VIP MEMBER

    Joined:
    Dec 29, 2011
    Squared off rear tire?

    Give us a profile pic...
     
    Last edited: Mar 29, 2019
  3. Craig

    Craig VIP MEMBER

    Joined:
    Dec 20, 2005
    You say 45-50 mph in second ...
     
  4. o0norton0o

    o0norton0o VIP MEMBER

    Joined:
    Apr 27, 2015
    did you gain 40lbs over the winter?? Are your tires old, oxidized and stiff? Tire pressure?? Early season thirst for torque after a long winter of downtime?
     
  5. worntorn

    worntorn

    Joined:
    Dec 22, 2006
    Tires are new last Spring, Avon Roadriders. Tire pressure is right, just added a bit before taking it out
    Im about the same weight as I have been for many years.
    I normally use third on that corner but decided to use second as with the uphill component third is a bit high.
    Second is definitely more fun!

    Glen
     
    Paul W. likes this.
  6. worntorn

    worntorn

    Joined:
    Dec 22, 2006
    6500 rpm in second gets about 65 mph by speedo on that bike.

    Glen
     
    Craig likes this.
  7. Craig

    Craig VIP MEMBER

    Joined:
    Dec 20, 2005
    I don’t often reach those rpm heights ....
     
  8. Dances with Shrapnel

    Dances with Shrapnel VIP MEMBER

    Joined:
    Jul 8, 2011
    Second gear at 6,500 rpm offers a lot of torque to the rear wheel. There may be a light oiling or ethylene glycol on the road - no see ums.
     
  9. Tornado

    Tornado VIP MEMBER

    Joined:
    Dec 5, 2017
    Can rear suspension be playing a role here, letting the rear loose contact with road? Any chance of an errant oil leak onto the rubber?
     
  10. worntorn

    worntorn

    Joined:
    Dec 22, 2006
    Definitely suspension is involved, but I suspect the rear suspension is about the same as ever on that bike.
    No oil on the tire, the Commando is as oiltight as the modern bikes.
    The tire has about 2500 miles on, so a bit less than half worn. There's a bit of a flat in the centre, not awful. It will only get worse from here, so you have to either cope with it or change it early.
    At the speed where it slipped the engine was probably at 4500-5000 rpm, maybe it's strongest level for torque.
    As you can tell, I was quite proud of the old girl!


    Glen
     
    Fullauto, cash and Tornado like this.
  11. Tornado

    Tornado VIP MEMBER

    Joined:
    Dec 5, 2017
    There are loads of Web articles and videos on setting up bike suspension, sag, pre-loads etc etc. We don't see too much of that talk on these forums regarding the classic bikes. If your bike still has original rear shocks. Could they be in need of replacement or adjustment?
     
  12. worntorn

    worntorn

    Joined:
    Dec 22, 2006
    Maybe. I don't mess with it because it has the most comfortable ride out of the 8 road bikes I have here, including two modern Triumphs.
    It's excellent over a rough patched blacktop road. The suspension is too cushy for ideal for track performance, but it is miles from being a track bike.



    Glen
     
    Last edited: Mar 29, 2019
    Tornado likes this.
  13. jbruney

    jbruney

    Joined:
    Jan 5, 2019
    Mine does the Norton squat & jump when the rear is set too light in the curves. I no longer ride in that manner, but I certainly do remember it hopping over. It left stains too.
     
  14. Tornado

    Tornado VIP MEMBER

    Joined:
    Dec 5, 2017
    On my 2013 T100, the stock rears have a rep as being poor performers. I tried playing with preload and saw big swings from soft and cushy to harsh and jolting. Best compromise was the dealer setting, but that tended to throw me up off the seat hitting moderate road bumps at speed. Took the legions of advice over on TRat forum to upgrade and found a nice pair of Hagon Classic III's used with only 200 miles on them. What a huge improvement! Bike no longer squats down in higher speed covers and never throws me off the seat hitting big road bumps. Best $150 I've spent on that bike.
    Got to wonder how well the Commando units actually perform, esp at their advanced age! I know Hagon will setup new units for your riding weight, so that's got to helpful as well.
     
  15. baz

    baz VIP MEMBER

    Joined:
    May 26, 2010
    I've not had the back wheel step out on avon road riders on my commando but I'm not surprised by this
    There is a lot of torque at those revs I have had plenty of unexpected wheelies on commandos, I detuned a combat for a mate of mine I put a 1mm plate under the barrel
    And fitted a single 34mm mikuni vm from a t500 suzuki stroker that bike would step out on tight bends when you grabbed a handful
     
  16. worntorn

    worntorn

    Joined:
    Dec 22, 2006

    With that Commando last year on a really snakey piece of road, I left a hotshot knee down rider on a Thruxton R behind , so I think they are adequate!
    Shocked the shit out of him, pardon the pun.
    He wanted to know what suspension and engine upgrades had been done to get that performance.
    Not much is the answer.

    The stock suspension on the 790 and 865 Bonnie's was pretty awful.
     
    Fullauto and Tornado like this.
  17. Tornado

    Tornado VIP MEMBER

    Joined:
    Dec 5, 2017
    Yup...best shocks on earth that could be made for $8 a pair !! :)
     
  18. acotrel

    acotrel

    Joined:
    Jun 30, 2012
    When I take my bike to Winton Raceway, I always find out how it is performing on the tightest corner which is a 180 degree hairpin bend. Because of the steering geometry, the bike never runs wide and tends to stay more upright in the corner. It wheel-spins in second gear every time, coming out of that corner. My tyres are old, but after they have ben used for a while, the grip improves - the bike still wheel spins after the tyres become hot. I suspect I need to go one tooth down on the rear sprocket. But the Commando engine is very strange. I have never previously had an engine which responds so well to tuning. It absolutely loves methanol fuel and the 2 into 1 exhaust. It pulls like a train, but without a close box it is hopeless. My revs are usually above 5500 RPM wherever I am on the circuit and I try to avoid going over 7000 RPM.
    If your bike is not cranked over when it wheel-spins, it usually won't step out. So the steering geometry is very important if you ride fast. I have never ridden a standard Commando, so I don't know what they do in corners. I would suspect they would be fairly neutral steering so would have a fair bit of lean.
     
  19. worntorn

    worntorn

    Joined:
    Dec 22, 2006
    I can see that an extra gear and closer ratios could be useful.
    Second gear on the stock box is 1.7 to 1 and third is about 1.2 to one. That's a big jump.
    Some literature shows the 74 on gearbox with a 1.6 to one second gear ratio and the earlier gearbox with a 1.7 to one second.
    The big white book shows the MK3 at 1.7. I'm not sure which ratio I have here, will have to measure.
    To my mind ,1.6 would be better than 1.7.

    Glen
     
    Last edited: Mar 29, 2019
  20. jbruney

    jbruney

    Joined:
    Jan 5, 2019
    I've never ridden any thoroughbreds. Stock Commando's are the closest I've ever been, and I find them to be more than adequate providing the front & rear damping is in good order with good rubber on the road. I've never been a lightweight, so dialing up the rear for cornering is a must to avoid the Commando twitch and for me keeping off the brake when it happens. I always allowed the throttle to salvage my situation. Anyway upon the rear jumping over it had a tendency to try going upright. More lean, more throttle was my compensation because hit brakes once and the bugger headed for the ditch in a straight line. I'd rather slide a bit than go cross country on a road bike.
     

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