Short Commando main front fork tubes

Hi I purchased a set of tubes from a fella that said I could use them to lower the height of the bike . They are 21.8 inches and the springs are 17.5 inches and the rods 18.5 inches in length. My question is will I be able to use the standard Dampers and all the other internal parts with these tubes. I am looking to build a complete front end damaged in an accident and would like to lower the bike at the same time to enable both feet planted on the ground. Would appreciate your feedback
Thx
Drummer99

If you lower both the front and rear of the bike by the same amount, your footrests will be closer to the road, so you will not be able to lean as much in corners. If you only lower the front, the bike might tend to run wide in corners, but the steering might be quicker. You are probably better with longer forks, softer suspension and more suspension travel front and rear. That way the rake on the steering head stays fairly constant.

When I used to have road bikes that were high, I used to slide to the left of the seat when the bike was stationary. I have never had the situation where both of my feet were on the ground, except when I had my 1940 Indian Scout.

Drummer99 said:

Hi I purchased a set of tubes from a fella that said I could use them to lower the height of the bike . They are 21.8 inches and the springs are 17.5 inches and the rods 18.5 inches in length. My question is will I be able to use the standard Dampers and all the other internal parts with these tubes. I am looking to build a complete front end damaged in an accident and would like to lower the bike at the same time to enable both feet planted on the ground. Would appreciate your feedback
Thx
Drummer99

Click to expand...

I think the dampers will work, but I question the value. You're lowering the front end about 1-1/2" - that's probably about 1/2 to 3/4" where you'll sit. I understand the desire - I wish my seat was lower too. If I were going to do something about it, I would consider a lower seat or shorter rear shocks.

acotrel said:

If you only lower the front, the bike might tend to run wide in corners, but the steering might be quicker.

Click to expand...

wrong again. If you only lower the front, you get a steeper rake angle which makes your steering quicker, but it does NOT make the bike want to run wide. It actually shortens up the "trail" so the bike could become unstable...

My friend has 1200cc Suzuki Bandit. If you brake while it is cranked over, it simply stands up and goes straight ahead. There is a difference between quick and fast steering and the tendency to tighten the bike's line or run wide. If the rear end squats more, the bike turns tighter. - Try it. Try braking slightly in the middle of a corner and see where you go. Most bikes refuse to turn as you brake and simply run straight off the outside of the corner. Another friend got on a fast Suzuki Katana historic racer and got into the sweeper on Winton too fast and backed off. Whatever he did he was going to crash. Fortunately for him, he decided to turn it on again and it steered . The guy who did that was not a beginner, had he been racing for many years.

o0norton0o said:

wrong again. If you only lower the front, you get a steeper rake angle which makes your steering quicker, but it does NOT make the bike want to run wide. It actually shortens up the "trail" so the bike could become unstable...

Click to expand...

Unstable is better than stable for cornering.
If you shorten the trail too much, the bike can stand up under brakes and turn the wrong way - it becomes too stable. This is not about stability, but where the bike tends to go as you gas it coming out of corners. I had the bad moment with my Seeley and came out of it by gassing the motor - after that happened, I took particular notice of how the bike felt under brakes. It was trying to stand up. If you have to reverse steer going into corners, you have a problem. I now have much more trail and the bike turns in extremely easily and tightens it's line if gassed coming out.

I think it would be possible to get the geometry so wrong that the bike would tie itself in a knot. When my Seeley mishandled, I was up shit creek without a paddle. It was just dumb luck that I decided to drive off the bitumen and turned it on again.

There is a guy here in Victoria who has an ex-Barry Sheen TR750 Suzuki. It has too much offset on the fork yokes and has scared him shitless - not just because it is fast.

Alan, you don't know what you are talking about. If you make the yoke angle steeper by shortening the fork tubes, the bike wants to TURN more easily PRECISELY BECAUSE IT HAS LESS TRAIL.

If you made the fork tubes longer, then it would want to go straight because it would have MORE TRAIL.

You should learn the physics instead of talking out your ass...

The length of the fork tubes in itself has no effect on trail or riding height .
They just hang down from the tripple trees , and support nothing .
( ok , a slight simplification ..)

In the standard design the damper rods are too short and the valve clunks on the underside of the damper body top, if you fit shortened tubes you fix this but then the top and bottom bushes get too close to each other at full extension so you also need to fit longer top bushes.

ludwig said:

The length of the fork tubes in itself has no effect on trail or riding height .
They just hang down from the tripple trees , and support nothing .
( ok , a slight simplification ..)

Click to expand...

I think you are being disingenuous here. If you are going to claim that the springs inside the tubes actually support the tubes mounted in the yokes rather than the fork tubes, I think you are splitting hairs. My point to Acotrel simply was that lowering the front of the bike by shortening the length of the fork tubes doesn't make the bike more likely to "run wide". He has that relationship backwards,.... again.

As far as the original poster's issue of wanting to lower the bike goes, the least complex way to do it without effecting the bike's geometry is to lower the seat itself by removing some padding. Short of doing that, almost every other method imparts changes to the bike. Granted, they may not be drastic or even noticable changes to an average rider, but the laws of physics predicts some differences.

-smaller wheel diameters will lower the bike. Many people here decry the use of anything but 19" wheels and cite mostly voodoo rather than science for the prohibition.
-shorter rear shocks will lower the rear of the bike and change the angle of the swingarm to the frame, which changes the "squat" characteristics of braking and throttle.
-adjustable yokes, in combination with shorter rear shocks are probably the best way to lower the bike and try to reach a happy compromise between what lowering one end of the bike does to the other end....

Ultimately there is good reading, and video material out there to explain how actual professional racers do this kind of thing.

here's a starter: http://www.advpulse.com/adv-prepping/how-to-lower-a-motorcycle/

Most bikes that are not 100 years old become stable as you brake and unstable as you accelerate. If you have ever had a front brake drag in a corner, you will know what I am talking about. Some brakes stay on, even after you have let go of the lever. Then you are driving the bike against the brake and the front stays down. It happened to me at Phillip Island when I first raced. At Southern Loop the bike took me off into the trees. I then crashed going into Siberia, but got back on the bike. Later in the day, in a race - I was rounding Siberia and got the feeling the bike would not go around. Because I had crashed there earlier, I thought I had a psychological problem - so I gassed the bike harder. All that happened was I went off the bitumen faster and ended up in the drain where there was a metre high bank - I slid up it on my back.
Disc brakes are much better than drum brakes, because when you let go of the lever, they come off immediately. However the single chrome disc on the Commando is not enough for racing. The first time I raced the Seeley, I had a large diameter GS1000 Suzuki disc. I got into a corner too fast and it refused to stop me. All I could do was hold it on and hope I did not run out of road before it decided to work. The whole time, the bike was running wide because the front was down. One thing some guys do, is use cast iron discs - don't do that !

I don't know what happens when you fit 18 inch wheels to a Commando. If you fit 18 inch wheels to a featherbed which has the 24.5 degree rake, in place of 19 inch wheels - you will stuff the handling. I did it and it cost too much to reverse. So I rode my Triton for years getting exhausted in every race. And the footrests were too close to the road. Most featherbeds which use 18 inch wheels have 26 degree rake and handle like Suzukis. It is a different deal.

' My point to Acotrel simply was that lowering the front of the bike by shortening the length of the fork tubes doesn't make the bike more likely to "run wide". He has that relationship backwards,.... again.'

What you think might happen and what actually happens are two different things. To make the bike turn tighter, it needs to squat more in the rear. If it goes down in the front, that is the same situation you have when the front brake drags. If bikes did not become more stable as we brake, everybody would crash. All you have to do to find out, is shut the throttle when halfway around a moderately fast corner and see where the bike goes.

acotrel said:

' All you have to do to find out, is shut the throttle when halfway around a moderately fast corner and see where the bike goes.

Click to expand...

Another one of your cryptic statements without any debatable statement of what you claim happens... I got news for you, what happens isn't a fixed thing in every case. It could depend on what happens to the bike's geometry based on what releasing the force on the drive chain does to that geometry. Depending on how the rear swingarm geometry is set up, releasing the throttle could reduce, or increase, the resulting trail... so I wouldn't expect the same results.

Do you see that both ludwig and madass "liked" my call out of your mistake? I think you should just learn the physics and give up the spouting of stories about your friends and your unscientific impressions of how motorcycle geometry works. Didn't we have a many page thread about how you mixed up the relationship of yoke offset and resulting trail??? maybe this will refresh your memory...

https://www.accessnorton.com/NortonCommando/steering-geometry-confirmation-bias.24310/

Most bikes that a ridden regularly don't have chain snatch. Have you actually tried what I have said about backing-off halfway around corners ? If your bike tends to run wide, you are often forced to back-off - that usually only makes the situation worse. But because you go slower, you recover. If your bike tightens it's line instead of running wide, you simply gas your way through problems. The ideal is when the bike tightens it's line when gassed when cranked over. You get that by having the rear end squat. Setting the rear suspension higher makes the bike turn less when gassed coming out of corners. I've watched a lot of Mike Edward's videos - he never gets to correct the problem of running wide, because he always winds the suspension up, instead of down. If you think about it as a castor effect - the castor trails behind the steering head, but the gyro is ahead of the steering head and that stuffs your thinking. A lot has to do with weight distribution and addition of vectors. If your bike tightens it's line in corners, it leans less, because it turns under itself.
You will note that Honda built a race bike with 50% weight distribution which did not handle because it did not rock backwards and forwards. Ducati got one of their race bikes to handle by running the motor backwards. - Vectors !

With race bikes, most of us simply adjust to their problems. Just about every on-board video I have ever watched about bikes on race circuits other than the IOM, has got the guys shutting-off halfway around corners through running wide. If everybody knows the answer to the problem of running wide in corners - why does that happen ? I always listen to the soundtrack and take note of where the back-off occurs. With my own bike, when the rear end squats - it turns. When I back-off in corners, it tends to run wide. If your bike does the opposite, you have a real problem. There is only one thing which worries me about my Seeley - when I ride it, I am probably riding it too fast. I have never had a bike previously with which I can get on the gas so early in corners. It means the fast corners are really fast. Thankfully it is a bit slower down the straights than modern bikes and it has not got the guts to hi-side itself.

acotrel said:

When I back-off in corners, it tends to run wide. If your bike does the opposite, you have a real problem.

Click to expand...

Again, why would I take advise about handling from someone who doesn't even know how offset, rake, and trail relate to handling?? Read your own thread in the link below, where you get that relationship wrong, over and over again...

https://www.accessnorton.com/NortonCommando/steering-geometry-confirmation-bias.24310/

To the original poster Drummer99:
I apologize for calling this guy out on the erroneous comment he posted on your thread. He posts his handling voodoo so often here, I wanted to call out his mistake about how lowering the front yoke height effects trail, but he doubles and tripples down on his nonsense as you can see, and turns the question you asked in your thread into stories about himself and hyperbolic questions about his own experiences riding.

Guys thanks for all your input I think I will keep the forks standard and take some padding out of the seat. As you say it will lower the foot pegs and that in itself is a problem
Thx Drummer 99