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Dick Mann Lean angle

Discussion in 'Motorcycle Related Discussions' started by jseng1, Oct 23, 2019.

  1. Fast Eddie

    Fast Eddie VIP MEMBER

    Joined:
    Oct 4, 2013
    Al, you should ask someone who knows about this stuff... which ain’t me !

    As has already been said, if my otherwise good handling machine started running wide on the exit I’d probably first look at the rear and suspect my shocks were squatting too much. Which means I’d be suspecting the rake needed steepening.

    But their really are many possible factors in play. As explained here:

    https://suspensionsecrets.co.uk/motorcycle-front-geometry/

    https://www.cycleworld.com/3-reasons-motorcycles-run-wide-in-corners/
     
  2. o0norton0o

    o0norton0o VIP MEMBER

    Joined:
    Apr 27, 2015
    My point to alan was that the more stable bike (the one with more trail) does want to go straight, and that you actually reduce the trail (and therefore stability) to make a bike steer more quickly. More trail makes a bike more stable, but also less nimble in the corners. When you brake going into a corner you momentarily get a less stable (but more nimble) set up as your forks compress due to weight transfer.

    Stability and quick handling are on opposite ends of trail adjustment. You don't get more stable and more nimble handling by adjusting trail. As one of them gets greater, you get less of the other...

    ....I'm sure there will either be an argument or a long convoluted series of hyperbolic rhetorical questions to follow, of which I will be answering none of them...
     
    Eljahara likes this.
  3. acotrel

    acotrel

    Joined:
    Jun 30, 2012
    You never know how fast you can get around a corner until you go in too hot. When I've had brake fade, I've found the tendency is always to run wide, because the dragging front brake forces the front down. You have a choice, you can continue to run wide washing off speed until you reach the edge of the bitumen, or you can choose a point at which you can get back on the gas and force the back down and the front up, then ride out of the problem. Many years ago, I rode at Phillip Island with a drum brake which had too much self-servo. When you braked, the brake did not come off again straight away when you let go of the lever. I ended up dodging small trees on the outside of Southern Loop, then I locked the brake doing about 90 MPH and crashed onto the non-skid surface. Later in the day, I started in a race. When I reached Siberia, I felt the bike would not go around the corner. Being an idiot, I thought the problem was psychological because I had crashed, so I went faster. All that happened was I ran off the outside of the corner faster and went up a four foot high bank on my back. After the race had finished, I tried to ride the bike back to the pits. There is a corner at the hay shed which is a slight right-hander. The bike would not go around it even at very low speed, because the front brake was dragging, forcing the front of the bike down.
     
  4. Eljahara

    Eljahara VIP MEMBER

    Joined:
    Jul 8, 2018
    Al,
    Stop taking the bait
    As we say ......hook, line and sinker!
     
  5. acotrel

    acotrel

    Joined:
    Jun 30, 2012
    With road bikes, how they steer naturally is not usually very important. But in Australia, many guys do historic racing with converted road bikes. When you look at a race bike, the steering geometry looks just like it does on any other motorcycle. Rex Wolfenden's methanol-fuelled 1100cc CB750 creations all tend to run wide in corners. That is the reason I was able to ride under them in turn two of that race 6 years ago. They cannot get the power down on the road early enough in corners. In two earlier races, because of the 4 speed CR box, I couldn't get a decent start - so ended up in the middle of the leading bunch of riders. In the last race, I took a chance and used a big heap of revs off the start, so I was with them in the first two corners. I accelerated under them easily. If there is ever a next time, I will win. And that is simply a statement of fact, not bragging.
     
  6. acotrel

    acotrel

    Joined:
    Jun 30, 2012
    This stuff is something I never knew when I raced regularly in the 60s and 70s. I'd love to see guys doing better with Commandos. That is the reason I stay with this subject. With a Commando, you usually have lower horsepower than most other bikes in historic races. And it should not always be about horsepower. 'torque wins races'. It is probably the reason Peter Williams was able to beat the TZ750s all those years ago. A TZ750 is a very serious motorcycle. If you get one of those upright and pointed, a Commando won't see which way it went.
     
  7. Fast Eddie

    Fast Eddie VIP MEMBER

    Joined:
    Oct 4, 2013
    Nope, although the Commando no doubt handled better than a TZ, the reason Peter Willimas won on the Commandos is because Peter Williams was riding (and had essentially designed chassis package that suited him perfectly).
     
    xbacksideslider and Snotzo like this.
  8. Seeley920

    Seeley920

    Joined:
    Jan 6, 2009
    Absolute BS from Alcatraz as usual. Peter Williams almost never raced against a TZ750, they didn't come out til 1974 and Peter was in hospital by then and the 1974 JPN was a failure in Peters eyes :eek:
     
  9. Bernhard

    Bernhard

    Joined:
    Apr 20, 2011
    Agreed, but the Yamaha tz 700 came out earlier (2x 350s)
     
  10. Bernhard

    Bernhard

    Joined:
    Apr 20, 2011
    Last edited: Nov 5, 2019
  11. Danno

    Danno

    Joined:
    Feb 7, 2010
  12. acotrel

    acotrel

    Joined:
    Jun 30, 2012
    I found this interesting - have a look at the adjustable fork yokes:

     
  13. acotrel

    acotrel

    Joined:
    Jun 30, 2012
    So I have confused a TZ700 with a TZ750 ? Was there a big difference in performance ? - I don't think so- especially as far as a Commando 750 is concerned. In a straight line, no Commando on earth would which way either of them went. However I think Peter Williams won at Silverstone in the dry, which as far as I know is a 'power circuit'.
     
    Last edited: Nov 5, 2019
  14. acotrel

    acotrel

    Joined:
    Jun 30, 2012
    Peter Williams, by his own words, has confessed that when he specified the steering geometry for the first commando - he got it wrong. However I'd bet anything it was perfect for the race track. If you set a bike up the way my Seeley 850 is set up and gave it to a beginner, they would probably crash it on the first corner. You brake in cranked over without reverse-steering, then get straight back onto the gas and let the bike do the rest. Whichever way it is cranked over, that is the direction in which it will oversteer. Most guys actually steer their race bike. With mine, you brake before the corner, aim it going in and then steer it on the throttle. It is much faster than intentionally steering your way around the corner. And you can still miss anybody who gets in your way.
    If you listen to most of the on-board videos on Youtube, you usually hear the guys back-off halfway around the corners. I never do that.
    I get confused with this stuff about trail and stability. To me stable is when the bike is difficult to turn into a corner when braking. I reduced the yoke offset from 69mm to about 30mm. At the first, the bike would actually rise in the wrong direction as I braked. With second it is still stable but with absolutely no understeer. But accelerating out of the corner feels totally different with the two different offsets. With 30mm offset, it is ridiculously confidence-inspiring. (My Seeley has 27 degree rake and 18 inch wheels. I don't know whether this stuff would be safe, if you did it with a normal Commando )
    From what I have read, it seems that MotoGP bikes went through this throttle-steering phase in the early 1990s. (These days they are probably too powerful. ) Is it possible to hi-side a Commando ?
     
    Last edited: Nov 5, 2019
  15. lcrken

    lcrken VIP MEMBER

    Joined:
    Mar 15, 2009
    Yes. My racing buddy high sided his Commando race bike (short stroke 750 engine) at Daytona exiting turn 1 back in 1990. Broke his pelvis and several other bones.

    Ken
     
  16. lcrken

    lcrken VIP MEMBER

    Joined:
    Mar 15, 2009
    Jarno Saarinen is usually credited as one of the first, if not the first, serious road racer to develop the hang-off riding style, back in the early '70s (he was killed in a crash in '73). Kenny Roberts has stated several times that he got his original idea from watching Saarinen when he came to the US to race at Daytona in '72 (where he won).

    I started racing in '72, and at that time there was still a lot of controversy over the advantages of hanging off. I started doing it mostly because of watching guys like Kenny. I don't know if I was any faster because of the style, but it did help keep me from grinding all the way through the primary cover:D.

    Saarinen 1.jpg

    You can see the difference in style here between Saarinen and Yvon Duhamel. Duhamel has his knee out a bit, but is still centered on the bike, while Saarinen is not.

    Saarinen 2.jpg

    I liked this description from one of his histories, of his development of the riding style:

    "In order for Jarno to ride his "hang-off" style, he lowered the clip-ons (handle bars) and excessively angled them downwards. Initially he got this from his previous experience as an Ice Racer in Finland before he started road racing. After Jarno's death, Kenny Roberts adopted this style and perfected it for road racing."

    Ken
     
    Last edited: Nov 6, 2019
  17. acotrel

    acotrel

    Joined:
    Jun 30, 2012
    I use the hang-off style with my Triton after I fitted 18 inch wheels, so the footrests would not ground and lift the rear wheel. ( I once crashed it because of that). With the Seeley set up the way it is, it seems to turn more under itself and in any case the footrests are on the swing arm spindle, not that inch or so lower. When I get confident, I always become apprehensive. So far the Seeley has not decked me, but in corners, everything happens extremely quickly. The last time I raced, I became more used to it's handling over two days and started using it to much better effect. I still have not found it's limit. So it is probably waiting to grab me by the throat. It is counter-intuitive to grab a handful of throttle in the middle of a corner.
     
    Last edited: Nov 6, 2019
  18. acotrel

    acotrel

    Joined:
    Jun 30, 2012
    In the early 1970s, I watched Mike Hailwood ride a Manx on Winton Motor Raceway. The most noticeable thing about him compared with the other guys, was the absence of lean. He was simply tucked in all smooth and neat - and super-fast.
    With Jarno Saarinen, he was riding a two stroke. The power characteristics of two-strokes back then dictated that you kept them as upright as possible, so getting off the side achieved that. It means you can get on the gas earlier coming out of corners - (point and squirt) and you are probably a bit quicker in the middle, if you have good tyres.. A normal Commando has neutral steering and with soft suspension, grounding things probably becomes a major problem, as you corner faster. Climbing off the side might get you around quicker, but the major problem is the way the bike steers and how far it leans naturally in corners. However changing it would probably introduce a risk.
     
    Last edited: Nov 6, 2019
  19. Bernhard

    Bernhard

    Joined:
    Apr 20, 2011
    Since you have never ridden either a water-cooled TZ700 or 750 (neither have I) I can tell you the TZ 700 was piston ported and was too peaky for solo use but the engines were very popular in the UK for sidecar racing, the TZ750 was fitted with reed inlet valves which made solo riding more agreeable and wouldn’t sprat the rider off more readily – I watched both being raced in the 70s.
     
  20. lcrken

    lcrken VIP MEMBER

    Joined:
    Mar 15, 2009
    I owned a late model TZ750D for a while that was licensed for the road. It was a full-on race bike with a license plate stuck on, and absolutely no street equipment. I bought it from the guy who restored it. He said he had a friend in the local (San Jose?) DMV who managed to get it registered for him. The only concession he made to street riding was to put treaded tires on in place of slicks. I later sold it to an owner of a bike shop in Britain, who was here in the US buying bikes to ship back. He said he wanted to put it in his showroom window. Unfortunately, I've lost his name, so I don't know what happened to it later.

    Anyhow, the point of this post is that I rode it briefly around the local streets, and can attest that it was quite rideable. If I could have fitted a starter, I would have wired it for lights and kept it. On the other hand, selling it let me buy a nice new heavy duty Miller TIG welder, as well as paying for half of a new Chinese milling machine. I've got a lot more use out of them than I would have from the TZ.

    Ken
     

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