Commando Top Speed? (2010)

Discussion in 'Norton Commando Classic Motorcycles' started by highdesert, Dec 21, 2010.

  1. Anonymous

    Anonymous Guest

    It is a low cloud dull grey drizzling rain day here and the GPS still says 3 metre accuracy (sitting inside the house as well). I changed the colour scheme to improve clarity (I prefer the green when in use on the bike).
    Ta.
     
  2. Old Scratcher

    Old Scratcher

    Joined:
    Mar 1, 2015
    Our govt has just reduced the margin of error it allows for inaccurate speedos, citing the improvement in accuracy of modern electronic speedos as one reason for the decision, with their desire to get us all to sit on or below the speed limit being the other reason. The real kicker is they won't say what the new margin of error is! So it really does pay to not go over the limit. That's why I love a car with an accurate cruise control. It's saved my licence many times. I'll be running lots of trials on both my bikes, when I'm riding again, to find out just how accurate each one is. I'll post the results here when I do. But that could be up to a year away! :shock: Unfortunately! :?
     
  3. gortnipper

    gortnipper VIP MEMBER

    Joined:
    Nov 11, 2013
    Ours is 4 kph. Try that with a 74 Speedo that's in mph...
     
  4. WZ507

    WZ507 VIP MEMBER

    Joined:
    Dec 26, 2013
    In some parts of the world
    Tomorrow is already Today
    and Today is Yesterday.

    In other parts of the world,
    Today is Yesterday
    and Tomorrow will be Today...

    So nobody's say'in you forgot anything, just that you promised :D
     
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  5. gortnipper

    gortnipper VIP MEMBER

    Joined:
    Nov 11, 2013
    LOL. As I like to say to guys on the Left Coast of the US, here in NZ we are now 5 hours behind you. Tomorrow.
     
  6. frankdamp

    frankdamp

    Joined:
    Oct 7, 2005
    During timed laps at MIRA, when we were doing max performance and endurance on their banked tri-oval circut and on their abolutely level mie track, the best top speed we got was a continuous 106 mph over about 30 minutes.
     
  7. Old Scratcher

    Old Scratcher

    Joined:
    Mar 1, 2015
    Which model? 750, 850? What tooth sprocket? I could see a stock 750 maxing out around there, but the Combats, JPS & 850s would've been quicker, I'd have thought.
    Sorry I just saw you were there during the development years. So was that the first production model or a prototype?
     
  8. Rohan

    Rohan

    Joined:
    Aug 26, 2010
    Redline with a 19 tooth gearbox sprocket and a stock bike calcs out at 107 mph.
    And thats what shown in the PUBLISHED gearing charts for a C'do with a 19 tooth.
     
  9. Rohan

    Rohan

    Joined:
    Aug 26, 2010
    With taller gearing, things happen a bit faster, of course.
    Gearbox sprockets are/were also available in 20t, 21t, 22t, 23t and 24 tooth.

    That FACTORY BUILT 850 Roadster Hotrod - with the 4S prototype cam etc - averaged out at 143 mph (2 way average) at Elvington in 1973.

    Dave Rawlins the pilot, and John Baker da enjinnear.
    Discussed here muchly - Andover Norton recently had their mugshots on the website there for a while too.
    Stock looking bike. As they said at the time, it was ridiculously fast for a road bike.
     
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  10. Jagbruno

    Jagbruno

    Joined:
    Jan 6, 2014
    The same published chart shows 124Mph @ 7000rpm with a 22T sprocket such as on my Featherbed/850/PW3 racer. My bike easily does that, even uphill such as the Dijon racetrack straight. In fact the tacho showed north of 7500 rpm on top at that spot on every lap... :mrgreen:
     
  11. chaztuna

    chaztuna VIP MEMBER

    Joined:
    May 5, 2017
    During my edit of the Mk III manual, section A page 10, I found a small error in the "Theoretical Top Speed Table" at the bottom of the page. I was looking for a formula to determine if the error I found caused an error lower in the table. [It didn't]. While researching a formula, it was suggested that you should be using the "loaded" [ie riders weight depressing the tire] radius for these calculations. By using 25", rather than 25.5" [I realize Jean is not using a stock Commando tire size], I was able to get his calculations to agree with the factory table.

    My research also states that bias ply tires will "grow" in circumference at speed, due to centrifugal force. Do any of you racers know what the size of a K81, K391, K591, Venom or Roadholder is at speed?

    The Mk III manual lists the diameter of a K81 4:10 X 19 tire as 26.46". Could it grow to that size "loaded" at speed?

    Charlie
    edited page number
     
    Last edited: Apr 11, 2018
  12. texasSlick

    texasSlick VIP MEMBER

    Joined:
    Jan 2, 2013
    I do not know if tires "grow" in diameter at speed, but films I saw in the 60's of tires rolling at speed, made me slow down.

    In the films, the loaded tire does not simply return to its unloaded radius after it rotates past the contact patch. The tire flexes rearward after leaving the contact patch , forming a rather large bulge before returning to normal radius. Naturally, all this flexure creates heat.

    The films gave me pause not to drive at speed on tires not speed rated.

    You are correct in that gearing/speed calculations must be based on the loaded radius of the tire .... whatever that turns out to be at speed.
     
  13. hobot

    hobot

    Joined:
    Oct 19, 2005
    I can verify on Ms Peel, that after 130 mph 120x18" radical will suddenly expand to raise speed almost 5 mph w/o engine rev's increasing past torque peak. I can see this happen on my wifes 250 Honda scooter on center stand, about 60's mph it suddenly expands significantly. There is magic lurking in skinny tires distortion vs fatso tires, which too often is more that best modren cycles and pilots can tolerate. If not comfy over 120 mph on Commando, when aerodynamic begin to dominate, tire expansion is a non issue. Tire expansion does not influence any handling issues, if any thing makes more like ice skater blade secure accurate aim. Aero dynamnics dominate over 120, nothing else as ya ain't gonna be leaning much at that speed so tires ain't limiting, just tuck down of lift/drag streamlining does.

    Hehe in my case I discovered 120 threshold when cresting hills on SuVee or Peel, I would be sucked out off of seat if not tucking down some and that's about the speed a knee out causes enough wind drag to help tip over before sucking knee back in for road lean clearance, not sticking way out like limited moderns feeling for lean limits to avoid or else.

    We are talking top outs, not sane mature survival but current age cycles and pilots requires 120 as baseline to go up/dn from in public so if not shifting to 4th as 120 ya ain't got what it takes to worry about tire expansion. In my dreams I want Peel to pull strong, about floating front to 165 then continue less strong to well over 175.
     
    Last edited: Apr 11, 2018
  14. Mr. Rick

    Mr. Rick VIP MEMBER

    Joined:
    Feb 6, 2009
    "I can verify on Ms Peel, that after 130 mph 120x18" radical will suddenly expand..."

    I assume you mean radial, as opposed to radical?
    I was under the impression that bias-ply suffered from such expansion, but that one of the advantages of radials is to largely eliminate this behavior. No?
     
  15. hobot

    hobot

    Joined:
    Oct 19, 2005
    Ms Peel never had full street tires fitted after using up old original tires, only a dual 20/off-80 on pavement Dunstal radial ply rear with tractor like cleats, rated to 120 sustained, which Peel exceeded routinely. Only once had opportunity to reach top out - 137 mph steady speedo needle on slight down hill 1/2 mile semi straight before sharp turn. I had pow wows with mature seasoned modern riders to see if their speedos matched Peels but they all quit after 130. Peel pulled good to 135 on level,
    so only teenager squids on 600's reported it took over 140 to past me - after I slowed down from my long lead through turns, d/t cresting blind I'd had bad surprises over, but they didn't so passed me over blind crests, to give sense of how much more crazy public racing is than regulated tracks. 900's to 1200's could out hp pass Peel after her lead to the the ton, if long enough opens, which pissed me off so spent on big block boosted engine to solve that. Most tagged Commandos can not reach 120 or owners not brave enough - so tire expansion mph increase w/o rpm increase not encountered.
     
  16. XTINCT

    XTINCT VIP MEMBER

    Joined:
    Jan 10, 2012
    1975, Me on "73" 850 Commando, long straight road, catching up to a friend on a Z900 Kawasaki. He had told me that he had previously had it up to 135 mph. If you remember the Z 900's, they had the speedo and tach tipped up almost vertical.
    As I passed him doing 110 on my Smiths Gauges, I could see his speedo, sur-nuff, he was doing 135.
    I had a stock 1968 CL 350 Honda that would do 97 mph. Yeah right!!
     
  17. JimC

    JimC

    Joined:
    Oct 12, 2007
    Two things wildly exaggerated by the owners, top speed and penis size.
     
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  18. worntorn

    worntorn

    Joined:
    Dec 22, 2006
    And a third item- stock market returns.
    Never met a man who made less than 40% percent per anum.
    Correction, Warren Buffet admits to making quite a bit less than this, poor fellow!

    Glen
     
    Last edited: Apr 12, 2018
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  19. XTINCT

    XTINCT VIP MEMBER

    Joined:
    Jan 10, 2012
    I have never met anyone that has lost money at the Native American Casinos, but still they show great profits.
    And by the way, my top speed is huge.
     
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  20. hobot

    hobot

    Joined:
    Oct 19, 2005
    One my wives said she married me because I had long nose and feet indicating other parts as well. Peel had tall gearing and steady accurate speedo so sticking with my claim of her rush to over 130 any time I wanted but had to wait 1/4 mile to get a few more to show up. Peel got passed a few times by 900's-1200 in opens, but only after 90-100 sprints on leaving parking for next leg of joy ride, but could hang right with em indicating 130 on both our speedos. Rather better than sex and lasts way longer too. I lived on Peel back then so got to play with people out of state, which lead to other pilots showing up on R1's, GXRS1000's, AprillaV4's, Ninja liter size, etc, seeking out Kingston Norton Nut for pecking order contests, so if not able to strongly pull to 120's, no contest. These were not squids but vacationing racers to Doctors, laywers, DDS, hi tech mature young people from big cities, we discussed rules/plans - not crazy squids. Mz Peel will have data logging of performance.
     

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