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

For the 20th time, I've disagreed with Acotrel who says:

When the trail is reduced and the bike becomes more stable


I have said repeatedly that:

When the trail increases the bike becomes more stable

He clearly doesn't believe me and for as many times as I've disagreed with him, I've yet to see a person "like" his response and I always get "likes" when I disagree with him so I'm pretty sure what I've learned about Rake, offset, and trail is correct.

What say YEE????

If your motorcycle was running wide as you accelerate out of corners would you wind the rear suspension up to get less trail - or down to get more trail when the bike squats more and increases the rake on the steering head ?

Good explanation here:

If what I do does not work, I must be dead.

The system is dynamic - not static. The biggest vector is the one through the centre of the front wheel The resultant force acts through the trail and is found by addition of vectors. If you stand on the right hand side of the motorcycle, the direction of the vector of the front wheel goes in the same direction as a right hand screw thead. If you hold the bars of a motorcycle during a tank slapper, the force is strong enough to flick you off like a rag doll.
The caster effect of a wheel on a piano is different - the wheel has no gyro effect.

o0norton0o said:

For the 20th time, I've disagreed with Acotrel who says:

When the trail is reduced and the bike becomes more stable


I have said repeatedly that:

When the trail increases the bike becomes more stable

He clearly doesn't believe me and for as many times as I've disagreed with him, I've yet to see a person "like" his response and I always get "likes" when I disagree with him so I'm pretty sure what I've learned about Rake, offset, and trail is correct.

What say YEE????

Click to expand...

Give it up, my friend. I've had the same back and forth with Alan a few years back, and he just doesn't understand the relationship between trail and handling. He means well, he's just wrong.

Ken

Thanks Ken, good to hear from you. I guess I should have known better...

In use the only thing can vary is trail, as the rest of the geometry is fixed. To explain this you can use two extremes, a stoppy, the trail will be reduced to zero when the line through the forks is vertically over the wheel spindle, both the vertical line through wheel spindle and the line through the forks have reduced the trail. Now do a wheelie, and the vertical line through the wheel spindle is still vertical and the line through the forks could be near horizontal. This simple terms and does not include things like offset, and where the wheel spindle pass through the forks at the lower end which is not always inline with the forks.

Easiest demonstration of effect of increasing trail is the wheels on a shopping trolley, the further away the wheel is from the pivot point the less the wheel will waggle from side to side as you push the trolley forward.

This thread reminds me of something that occurred in the USA some 40 or 50 years ago. A US government committee awarded a grant of half a million $, If I remember correctly, to someone to develop a motorcycle with rear wheel steering. My first thoughts were that the committee comprised a bunch of imbeciles and the recipient was either a con artist or another imbecile. A year or so later I heard that the rear wheel steered bike had been built but they hadn't been able to find anyone who could ride it. What a surprise!

Another source: Kevin Cameron https://www.cycleworld.com/blogs/ask-kevin/what-is-motorcycle-trail-explained/

Northern Norton Nut said:

Another source: Kevin Cameron https://www.cycleworld.com/blogs/ask-kevin/what-is-motorcycle-trail-explained/

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From Kevin's essay on his website:

Trail gives a motorcycle stability by causing both front and rear wheels to align with the vehicle’s direction. Sporting motorcycles tend to have trails in the range from just over 3 inches to 3.75 or even 4 inches. Anything over 4 inches has generally been provided to give extra stability to large touring rigs. This is the geometric trail.

Perhaps I'm too optimistic but I figured it's worth one last try.

I don't know what I have done with my Commando/Featherbed but it's very stable in corners and even better when you put the power on when in the corners and at high speeds it grips the road like glue and hence the old saying about Featherbed frames, like riding on rails and like riding on a Featherbed, also how the motor is mounted also plays a big part, the 850 sits as low as it can be and as forward as it can and still keeping the tilt like a Commando.
I run my Commando front end and Commando rear Koni shocks with both 19" Akront alloy wheels on my Wideline Featherbed and seems to match up perfectly, I got it right from the beginning all of them years ago when I built it in 1980, sometimes I got to look back to see if I did push it through that last corner, it's such a fun bike to ride, puts a smile on my dial every time I am out on it.
As for the front and tail, I know mine is set just right for me.

Ashley

Most road bikes are designed so that beginners do not crash them, so have neutral handling. My mate bought a Suzuki Babdit 1200, Under brakes it stands upright and goes straight. It is designed to do that. When you brake on a motorcycle, the trail reduces. If you already have a lot of trail, the handling is in a different position. The bike will oversteer and enter corners without counter-steering, and will oversteer as it accelerates out of corners. It means the bike can be flicked into a corner and accelerate from start to finish with less lean, so more power can be used. But the power delivery needs to be very smooth. For a large four cylinder bike, or a two stroke, that sort of steering would be very dangerous. When you race a Commando, you need to race with your strengths. In races, I would always much rather go under other riders than over. To go over, you need much more horsepower, and you usually end up in a drag race, which you cannot win. When you turn inside the other riders and accelerate, you come out of the corner at a much higher speed, so the other guys need much more power. If you watch the video of Mike Hailwood racing the Ducati at Mallory in 1979, you will see the opposite strategy. When he passes, he goes over rather than under. His bike is extremely stable and understeers, so not suited to going under. My bike is stable but oversteers and is suited to going under. In corners, most guys are usually out fairly wide, and there is always room to go under them.
A lot of guys are fixated on high horsepower, extreme angles of lean and sticky tyres. It does not have to be that way.

ashman said:

I don't know what I have done with my Commando/Featherbed but it's very stable in corners and even better when you put the power on when in the corners and at high speeds it grips the road like glue and hence the old saying about Featherbed frames, like riding on rails and like riding on a Featherbed, also how the motor is mounted also plays a big part, the 850 sits as low as it can be and as forward as it can and still keeping the tilt like a Commando.
I run my Commando front end and Commando rear Koni shocks with both 19" Akront alloy wheels on my Wideline Featherbed and seems to match up perfectly, I got it right from the beginning all of them years ago when I built it in 1980, sometimes I got to look back to see if I did push it through that last corner, it's such a fun bike to ride, puts a smile on my dial every time I am out on it.
As for the front and tail, I know mine is set just right for me.

Ashley

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When you fit 18 inch wheels to a bike like yours, the trail is reduced and it becomes much less nimble. I did it to my 500cc Triton and when I got off it after races I used to be exhausted. And even with the better rubber, it was no faster. The position of the motor is critical. My mates 650cc Triton is a nice bike to ride. The motor is an inch further back, and in corners it is not so positive - but is faster down the straights where my Triton was faster in the corners. In races we were very evenly matched. I could never convincingly beat him.

In the vertical plane. the bike rotates around its centre of gravity as you accelerate and brake, the position of the motor affects the feel and the grip of the tyres. When the motor in my 500cc Triton was that inch further back, it was horrible. I couldn't ride it without scaring myself. My mate had ridden it at Bathurst in about 1958, and almost killed himself. He got a broken arm and a broken leg in the one crash. It bounced him off the fence at Skyline Corner. Everything about it had been done to the theories - bullshit !
- I liked it a lot - in those days I was an adrenaline junkie. It was a thrill a minute.
I still have a trophy which was won with that bike when it was detuned.

Here is an excercise some of you might like to try. Get yourself onto a race circuit and ride your bike at moderate speed into a right-hand bend in the middle of the track. And while the bike is still on a lean, gas it hard to see which way it turns when you do not help it. I suggest most road bikes and Japanese two strokes would go straight ahead. A Commando might go left, and Manx Norton would probably go right. My Seeley 850 would definitely turn right.

One post admitting defeat would be sufficient, four rabbling posts just confirms you are best on the ignore list.

acotrel said:

Most road bikes are designed so that beginners do not crash them, so have neutral handling. My mate bought a Suzuki Babdit 1200, Under brakes it stands upright and goes straight. It is designed to do that. When you brake on a motorcycle, the trail reduces. If you already have a lot of trail, the handling is in a different position. The bike will oversteer and enter corners without counter-steering, and will oversteer as it accelerates out of corners. It means the bike can be flicked into a corner and accelerate from start to finish with less lean, so more power can be used. But the power delivery needs to be very smooth. For a large four cylinder bike, or a two stroke, that sort of steering would be very dangerous. When you race a Commando, you need to race with your strengths. In races, I would always much rather go under other riders than over. To go over, you need much more horsepower, and you usually end up in a drag race, which you cannot win. When you turn inside the other riders and accelerate, you come out of the corner at a much higher speed, so the other guys need much more power. If you watch the video of Mike Hailwood racing the Ducati at Mallory in 1979, you will see the opposite strategy. When he passes, he goes over rather than under. His bike is extremely stable and understeers, so not suited to going under. My bike is stable but oversteers and is suited to going under. In corners, most guys are usually out fairly wide, and there is always room to go under them.
A lot of guys are fixated on high horsepower, extreme angles of lean and sticky tyres. It does not have to be that way.

Click to expand...

acotrel said:

Here is an excercise some of you might like to try. Get yourself onto a race circuit and ride your bike at moderate speed into a right-hand bend in the middle of the track. And while the bike is still on a lean, gas it hard to see which way it turns when you do not help it. I suggest most road bikes and Japanese two strokes would go straight ahead. A Commando might go left, and Manx Norton would probably go right. My Seeley 850 would definitely turn right.

Click to expand...

Then what?

If your bike oversteers into the direction you want to go when you gas it - it can make the difference between winning and losing races. If you are on a lean to the right, and the bike turns in that direction instead of running wide, you can accelerate much harder. And bikes that do that do not lean much, so they are not so tyre dependent. Bikes which have very high horsepower and are peaky, usually require more lean and better tyres and are usually committed to taking the higher line in corners. They usually get on the gas later in corners. If you ride a Commando-based bike and join the procession, you come out of corners much slower and the others will always be ahead of you. Those other bikes usually cannot use full power in corners, because they have more lean.
In the old days, Manx Nortons oversteered in the correct direction, could not be forced to adopt much lean. They also had shit tyres. Two-strokes were lighter, had better gear boxes and had much more lean. The style of riding changed - on very tight circuits a Manx was a better deal. A two-stroke is usually a peaky power machine - get them pointed before you give them the berries. Racing against them is bad, I am always worried I might hit one in a corner. Same with big four cylinder bikes. They need to be straight up and down before they really go.
I never really believed in my Seeley 850, until I figured-out how to use it. When you race, try advancing the transition point in corners. The last time I raced, my transition point was just inside the beginning of the corner. But I think I can brake before the corner and accelerate hard before I even enter it. A Commando motor cannot grab you by the throat. To make my bike steer itself around corners, I need to make it squat about 1 inch, so the rear suspension needs to be soft. Making it harder decreases the rate of turn.