What is the effect of LESS TRAIL (Racers encouraged to answer)

which change in trail makes a bike more stable??

  • More trail makes a bike more stable

    Votes: 9 90.0%

  • Less trail makes a bike more stable

    Votes: 1 10.0%
  • Total voters
    10
acadian said:
nobody has mentioned wheel diameter as a determinant of trail, important consideration for me at the moment as I ponder whether or not to go with 18" wheels on my race bike
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A Manx Norton usually has 19 inch wheels, and the yoke offset is minimal, however the rake is much steeper than normal. If you are on a lean with a Manx, you can usually gas it much harder than many other bikes, it will steer in the correct direction. 18 inch wheels are OK on a featherbed, but if the motor is well forward, the handling becomes less nimble. Fastest cornering is motor well forward and 19 inch wheels.
The guy in this video never seems to mention trail - not all bikes have the same steering geometry.

 
acotrel said:
A Manx Norton usually has 19 inch wheels, and the yoke offset is minimal, however the rake is much steeper than normal.
Click to expand...
What do you mean by normal? Go fast bikes like a Fireblade or a R1 has steeper rake than a Manx. The BMW S1000RR about the same rake as a Manx. Trail about the same on all of them.
 
Mike40M said:
What do you mean by normal? Go fast bikes like a Fireblade or a R1 has steeper rake than a Manx. The BMW S1000RR about the same rake as a Manx. Trail about the same on all of them.
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I mean a normal British motorcycle of the 1960s - sorry, I forgot my age. When I talk about race bikes, I live in the 1970s. When you get later, the horsepower is often double My project bike is an Egli frame with an H1 Kawasaki motor fitted with RD350 reed valve cylinder. It has 17 inch wheels and the steering geometry of the second model of Suzuki RG250. 600cc two-stroke is a different thing altogether. Increased trail on an R1 or a Fireblade might be exciting.
 
acotrel said:
It has 17 inch wheels and the steering geometry of the second model of Suzuki RG250.
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My son races a -86 RG250. Fitted with TZ wheels and fork. Because no slicks available in 16" and 18". We never measured geometry after change but it handles very well. Looking a bit funny with stanchions sticking up some 40 mm over top yoke.
The original RG250 24.7 rake and 102 trail seems reasonable to me. Guess anything between 24 to 26 rake and around 100 mm trail gives fairly decent handling.
 
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acotrel said:
I found this video interesting. It makes several conclusions at which I have also arrived :

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Friend, boss of MotoGP suspension department of a well known Swedish company. Told me that with all software design aids and data from the bikes they can get fairly close to best setup for different tracks. But then feedback from the riders needed for final adjustments. The team don't want to hear what to do but how the bike feels. Final setup different for each rider. Valentino Rossi is the best of them at describing the feel around the track.
 
Mike40M said:
Friend, boss of MotoGP suspension department of a well known Swedish company. Told me that with all software design aids and data from the bikes they can get fairly close to best setup for different tracks. But then feedback from the riders needed for final adjustments. The team don't want to hear what to do but how the bike feels. Final setup different for each rider. Valentino Rossi is the best of them at describing the feel around the track.
Click to expand...
The Cycle World site talks mentions the mighty Norton Commando quite often in the various episodes I have seen. In one that featured the 900 Kaw had a stock 850 Commando turning 12.96 second 1/4s at 102 MPH only 4 tenths slower than the 1973 Z1 Kaw 903cc. 12.61 But with the 1/4 mile times of the early 750 Commando in the low 12s, It really came down to rider ability. But a Commando hold it's own. As far as roadracing there are ways to make them take no prisoners and take out some big guns and show them how with very low tech.
 
Carl H said:
The Cycle World site talks mentions the mighty Norton Commando quite often in the various episodes I have seen. In one that featured the 900 Kaw had a stock 850 Commando turning 12.96 second 1/4s at 102 MPH only 4 tenths slower than the 1973 Z1 Kaw 903cc. 12.61 But with the 1/4 mile times of the early 750 Commando in the low 12s, It really came down to rider ability. But a Commando hold it's own. As far as roadracing there are ways to make them take no prisoners and take out some big guns and show them how with very low tech.
Click to expand...
I am still surprised that the Commando is so good, but perhaps I should not be. A Manx Norton was usually unbeatable in its class by any bike which was not four cylinder or a two-stroke. I doubted the Norton road bikes would reflect the technology of the race bikes. I always suspected the high-crown pistons in my 650 Triumphs were a problem. The fastest one had 350 Gold Star BSA pistons - flat-top with the edges of the crown to make squish in the Triumph head.
 
I wonder about this riding style thing. I aways adapt to the bike and change my style to suit the way it handles and where the power-band is. The last time I raced, was the second time after fitting the Yamaha TZ25 fork yokes. I discovered I did not know how to use the bike properly. It is really stupid to flick a bike into a corner, then immediately accelerate full bore past the leaders in a race. It makes me nervous even thinking about it. When you pass guys like that, they can fall off, or panic about being passed by such on old bike. That was the only time I have ever had a machine fault which stopped the bike, and the guys I passed were worth beating. I had them cold - they were done. None of them said anything after the race.
The joke is I have never been a fully committed road racer, and the kids noticed my age.
Those other bikes go down the straights like rockets. - Commandos are good motorcycles.
 
Carl H said:
The Cycle World site talks mentions the mighty Norton Commando quite often in the various episodes I have seen. In one that featured the 900 Kaw had a stock 850 Commando turning 12.96 second 1/4s at 102 MPH only 4 tenths slower than the 1973 Z1 Kaw 903cc. 12.61 But with the 1/4 mile times of the early 750 Commando in the low 12s, It really came down to rider ability. But a Commando hold it's own. As far as roadracing there are ways to make them take no prisoners and take out some big guns and show them how with very low tech.
Click to expand...
I used to race Z900 Kawasakis in Allpowers races with my 500cc short stroke Triton when I was a kid. I had a 4 speed close ratio gear box. So I could either gear it high or low. Either way I was going to lose. Geared high I could stay with them, but I was too slow coming out of corners. I only geared it low once. I blitzed them all off the start and led for most of a lap, but they passed me towards the end of the main straight. I came into a corner miles too hot behind the three leaders, then stood the bike to miss them and speared off. That was on the small circuit at Winton. I would not like to ride a Z900 at Philip Island. They used to go around the bend which leads onto the main straight doing high speed weaves, due to flex.
 
It is relatively easy to beat a Z900 Kawasaki or an 1100cc methanol-fuelled CB750 on Winton Raceway. The longest straight is about half a kilometre in length. If you power through the preceding corner and are doing about 60 KPH faster than the Z900, when the guy on the Z900 begins to accelerate, you should get to the next corner first.
 
Regardless of opinions regarding figures, I have a simple approach to set up. Do what you can without butchery, use quality parts. have some adjustability, but not too much.

I use a frame as provided by the manufacturer! The fork legs are by Maxton, and are longer than standard for this frame. I use standard fork yoke dimensions, i.e. standard offset.

The only non-standard component is have is a slightly longer swinging arm, this was done purely to allow the use of a 130/70 x 18" profile rear tyre. In an ideal world I might have preferred to shorten the wheelbase, but compromise is the name of the game.

To adjust the set-up to reduce stability and improve steering responses, I raise the rear suspension. It is about all I have. To that end, the Rickman I race has shocks 2" longer than Rickman fitted.

The only other adjustment I have is to lower the fork yokes on the stantions. I have tried small increments, but have settled back at the standard fork length, which in any case places the headstock a little lower than originally designed, due to a front 18" rim with 90/90 profile tyre on a WM3 instead of the 19" WM2. So the rake/trail is not as standard, even if I don't even know what that or the current figure is.

Technically I think it steers a little quicker that it did when I bought the chassis in 1975, but, that really was a long time ago, and fogged by the fact that it was on 19" Dunlop triangulars then. I made two changes back then, I fitted a KR83 intermediate rounded profile rear tyre and 1" longer shocks. I think both of these things were an improvement.

Is it ideal today? Of course not. Is it rideable by the average rider? Yes. Do I want to mess with it any more or explore the science? No.
 
SteveA said:
Regardless of opinions regarding figures, I have a simple approach to set up. Do what you can without butchery, use quality parts. have some adjustability, but not too much.

I use a frame as provided by the manufacturer! The fork legs are by Maxton, and are longer than standard for this frame. I use standard fork yoke dimensions, i.e. standard offset.

The only non-standard component is have is a slightly longer swinging arm, this was done purely to allow the use of a 130/70 x 18" profile rear tyre. In an ideal world I might have preferred to shorten the wheelbase, but compromise is the name of the game.

To adjust the set-up to reduce stability and improve steering responses, I raise the rear suspension. It is about all I have. To that end, the Rickman I race has shocks 2" longer than Rickman fitted.

The only other adjustment I have is to lower the fork yokes on the stantions. I have tried small increments, but have settled back at the standard fork length, which in any case places the headstock a little lower than originally designed, due to a front 18" rim with 90/90 profile tyre on a WM3 instead of the 19" WM2. So the rake/trail is not as standard, even if I don't even know what that or the current figure is.

Technically I think it steers a little quicker that it did when I bought the chassis in 1975, but, that really was a long time ago, and fogged by the fact that it was on 19" Dunlop triangulars then. I made two changes back then, I fitted a KR83 intermediate rounded profile rear tyre and 1" longer shocks. I think both of these things were an improvement.

Is it ideal today? Of course not. Is it rideable by the average rider? Yes. Do I want to mess with it any more or explore the science? No.
Click to expand...
Usually on a road bike, as you use the front brake is used the front of the bike goes down and the bike becomes more difficult to turn as the rake steepens - the bike is understeering slightly and might even need counter-steering to get it to tip into corners. If you have a lot of trail the reduction caused by the decrease in rake makes the bike less stable and easier to tip into the corner. If you go into the corner too fast and gently use the front brake to lose speed, on any road bike , if you wait until you get down to a speed at which you have rear tyre grip, while you are running wide you can accelerate, and as the rear goes down and the front comes up, the bike will self-steer out of your predicament and turn in the correct direction. The problem is the first time you do it, it requires a leap of faith. The natural instinct is to brake harder - not accelerate,
If you have a lot of trail on a Commando engined bike, you can just flick the bike into a corner then accelerate full bore and the bike steering itself. If it turns too much, wind the rear suspension up slightly and it will turn slower.
It is easy to get this wrong, if you have not experienced it. The only way I suspected it was possible was I was beginning to transition from braking to accelerating much earlier in corners after I reduced the yoke offset by 12mm.
Kevin Cameron of Cycle World does not seem to really understand it. But do not get it wrong, it can be bloody dangerous,
If the bike understeers while braking into corners, it will usually understeer as it accelerates out. And vice-versa with oversteer. The understeer is stable, the oversteer is unstable. With a lot of trail, the bike will steer in the direction of lean when you accelerate to a much greater extent - the rear must squat to increase the trail. So always brake before entering a corner at speed.

 
It's not a road bike.

I always counter steer.....so does everybody else.....those who say they don't do too....they just like to argue about it.

Gyroscopic precession is a bit of science I understand reasonably well, having been taught it several times in the world of avionics.

How many handling threads have you started because you changed the yokes on your bike?
 
acotrel said:
I am still surprised that the Commando is so good, but perhaps I should not be. A Manx Norton was usually unbeatable in its class by any bike which was not four cylinder or a two-stroke. I doubted the Norton road bikes would reflect the technology of the race bikes. I always suspected the high-crown pistons in my 650 Triumphs were a problem. The fastest one had 350 Gold Star BSA pistons - flat-top with the edges of the crown to make squish in the Triumph head.
Click to expand...
The Commando should have been better, The first year 1968 Commando raced on terrible sized and shaped stock tires in the classes they raced and very poor set up. Later on, in Vintage racing it seems to me they just did not know how to set them up or make them reliable or even well tuned. As Hall of fame racer Joe Bolger said after seeing my bikes run for years and do very well. '"You (meaning me) should have worked for the Norton Factory," and As Dick Klamfoth told me, My streetable Commando was the fastest Norton he ever rode. Some of the great racers like DuHamel, Henning, Wood and Greg Nichols needed a bikes to race and we showed why the CHR Commandos were formidable weapon even in street trim. They won a few AHRMA nationals and an FIM#1 plate as well as 4 #1 plates in a row in the USCRA open class. At the original "Laconia" track, the bikes and my riders Klamfoth and Gariepy put the Commandos way ahead of the other legends on the track. And Yvon in 2002 destroyed all the others that was gunning for him and won by a country mile in the 750 class feature race at the very dangerous Laconia track. The old time fans there were amazed by what a good Norton could do and how pretty the bikes were, pretty awesome that is. The New Hampshire tracks were just perfect for a streetbike set up with real handlebars and a nice cushy stock seat that could accelerate like a jet with men on board that are HOF legends , it was an unbeatable combination.

The thing that changed USA Vintage racing was when Todd Henning #454 developed the CB Hondas into his Drixton framed world class race bikes with his race tech, but that is a whole other story. I did own his first 450 Honda race bike, briefly, that started the Honda revolution in all the 4 stroke classes he raced in. But he did prove you can do a real lot with a streetbike, even a CB Honda. His son Ari Henning still races Todd's old bikes and is a heck of a rider.
 
Sitting back with the popcorn half gone.
Thought I'd throw gas on the fire for a great finish.
What would be the effect of non-parallel triple clamps on a Norton. ( Both directions, esp in deep braking corners )
Without googling, 2 examples of bikes using non-parallel triple clamps.
Cheers
 
TheCounty said:
Sitting back with the popcorn half gone.
Thought I'd throw gas on the fire for a great finish.
What would be the effect of non-parallel triple clamps on a Norton. ( Both directions, esp in deep braking corners )
Without googling, 2 examples of bikes using non-parallel triple clamps.
Cheers
Click to expand...
I think non-parallel fork yokes would make the steering try to centre itself and lift the front of the bike as it was steered out of a straight line. Playing with fork yokes is dangerous If you create a problem, it can come from nowhere and deck you. When I fitted the TZ Yamaha yokes to my Seeley, I knew the Yamaha had 60 degree rake and the Seeley had 70 degree rake. The first time I rode it I was still taking very careful note of what the bike was doing as I accelerated and braked. For someone less experienced, it might not be a good exercise.
 
Carl H said:
The Commando should have been better, The first year 1968 Commando raced on terrible sized and shaped stock tires in the classes they raced and very poor set up. Later on, in Vintage racing it seems to me they just did not know how to set them up or make them reliable or even well tuned. As Hall of fame racer Joe Bolger said after seeing my bikes run for years and do very well. '"You (meaning me) should have worked for the Norton Factory," and As Dick Klamfoth told me, My streetable Commando was the fastest Norton he ever rode. Some of the great racers like DuHamel, Henning, Wood and Greg Nichols needed a bikes to race and we showed why the CHR Commandos were formidable weapon even in street trim. They won a few AHRMA nationals and an FIM#1 plate as well as 4 #1 plates in a row in the USCRA open class. At the original "Laconia" track, the bikes and my riders Klamfoth and Gariepy put the Commandos way ahead of the other legends on the track. And Yvon in 2002 destroyed all the others that was gunning for him and won by a country mile in the 750 class feature race at the very dangerous Laconia track. The old time fans there were amazed by what a good Norton could do and how pretty the bikes were, pretty awesome that is. The New Hampshire tracks were just perfect for a streetbike set up with real handlebars and a nice cushy stock seat that could accelerate like a jet with men on board that are HOF legends , it was an unbeatable combination.

The thing that changed USA Vintage racing was when Todd Henning #454 developed the CB Hondas into his Drixton framed world class race bikes with his race tech, but that is a whole other story. I did own his first 450 Honda race bike, briefly, that started the Honda revolution in all the 4 stroke classes he raced in. But he did prove you can do a real lot with a streetbike, even a CB Honda. His son Ari Henning still races Todd's old bikes and is a heck of a rider.
Click to expand...
When the 850 Commando arrived, I was still racing my 500cc short stroke Triton. SR Evans were the dealers for the Commandos, and the got Jeff Curley to ride one in a production race - which he convincingly won. It was obviously about getting sales. But Jeff was a cop, and an excellent A-Grade rider. So it appeared to be the rider and not the bike which won.
I don't think I ever saw another 850, or even 750 Commando get raced. It was Z900 and H2 Kawasaki era.
As I have said, I am amazed that 850 motor is so good. I just needed to find out how to use it. It is very different from a Triumph or BSA twin. The close ratio gearing really fixed it.
 
TheCounty said:
Sitting back with the popcorn half gone.
Thought I'd throw gas on the fire for a great finish.
What would be the effect of non-parallel triple clamps on a Norton. ( Both directions, esp in deep braking corners )
Without googling, 2 examples of bikes using non-parallel triple clamps.
Cheers
Click to expand...
I tried that once by swapping unequal length rocker links on a custom girder front end back on my chopper days. Yes the straight line stability was increased but the bike would try to lay down when the forks were turned in the slightest.
 
This is what I'm talking about The 1968 Commandos ridden by George Kerker and Art Ninci. Just leaving the 1 foot square license plate air dam was worth negative 5 MPH down the straights. The tires were scary and the riders were brave. If the Nortons could win like they did in stock trim, there was a heck of a lot more you could get from one, just with simple mods.

Back when I rode in the late 1980s, the grids were filled with big bikes and pro level riders in the field with some well developed "factory like" equipment. I did OK winning #1 plates several times in a row. Then when I finally got real racers needing rides, the fun really began, and they made CHR Commandos a frequent visitor to Victory Circle. Our club USCRA was like a wrecking crew when it came for AHRMA and Can Am races, lots of fast bikes from elsewhere went home with few points due to the USCRA's stranglehold. Commandos actually became respected again as the great bike they are. And old racers got to do what they do best, ride like the wind.

No matter who the racer is , he needs a decent bike to win and one that can finish.

www.cyclenews.com

Archives: The Pipe Man

George Kerker was an innovator and an unforgettable personality
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magazine.cycleworld.com

Norton Commando | Cycle World | SEPTEMBER 1968

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