weight distribution vs "sags"

[Camn]

Very interesting measurements.

 

Last summer I tried the most extreme: I dropped the triplets as much as possible (18 mm more than the factory setting) plus had the sag adjusted to maximum. Rear sag to minimum. The idea was to try, if I could move more weight to the front. The tendency to wobble at high speed did not change for better. At least not very much. The steering was clearly easier on curvy roads, I liked that a lot. But the result was that the “free space” between the oil pan and ground was reduced. The side stand took a good hit on asphalt…and there we went… (when training cautiously on a track). My experience was, that for normal driving – I liked it a lot. For practicing on  track – you should be more experienced (than me, to know how much lean over).

 

The RSV Mille was mentioned. RSV 1000 Technical Training Course 7/1999: "The RSV Mille is the best production line bike for use on the track. Dry weight 189 kg, optimally distributed with 49.2% on the front axle and 50.8% on the rear axle.”

 

V11 46/54%, RSV Mille 49/51%, both values from the first production model from 1999 (Mille obviously with original parts, the muffler weighs a ton...).

[JRD]

Very interesting results Docc, thank you very much for posting.  Did you by any chance try cranking some spring pre-load into the bike to see if it affected the weight bias?  I'm jus curious to see if would make any difference at all.

[docc]

With so many measurements to take on two separate bikes, while trying to keep them off their sides, we decided not to make any changes during this exercise.

 

My rear Öhlins does have a remote adjuster cranked up about 3/4, but I am reluctant to move it. Twice I have found it backed off completely (the last time I pulled over to inspect because it felt like the rear tire had gone flat!). I painted a big, ugly white stripe down the side of the adjuster to alert me if it moves again.

 

As GuzziMoto said, preload changes are not likely to materially change weight distribution. Even hanging twenty pounds behind the rear axle only changed the distribution 1%. And the rider only 2-3%.

 

When we set up the test bed again, we will be making sag changes on the Sport1100 and can record the effect on weight distribution.

[docc]

Interesting, Chuck posted his findings on weight distribution in another thread and I wanted to reference them here (once again: 46/54 with no rider):

 

"First, the Lario. I filled the tanks so we would be at least have the same "ready to ride" weights.
The Lario weighs 205 lbs on the Front wheel and 234 on the rear. All up weight 439 minus 29.7 lbs of fuel= 409.3 empty. I would have thought it was heavier. The Lario *does* have HB racks.. call it 5 lbs or so for a little over 400 lbs empty.

The Monza. 186 front 210 rear=405 lbs all up. minus 26.4 lbs of fuel= 378.6 empty.

Scura. 247 front 290 rear= 537 lbs all up. I ran out of fuel.. it was about 1 inch below the filler neck, so I'd say a gallon or less, but if it was full it carries 37.95 lbs of fuel for 499.05 empty. I'll say it was a gallon low and call it 505. I would have thought it was heavier. "

[not-fishing]

Before I look at weight distribution and "sag" of my Lemans I need to deal with weight distribution and sag of the rider.  45 lbs overweight and to much weight in the "middle".

 

Mark

[Cabernet]

Before I look at weight distribution and "sag" of my Lemans I need to deal with weight distribution and sag of the rider. 45 lbs overweight and to much weight in the "middle".

 

Mark

Like me, we have good mass centralization.

 

Sent from my D5803 using Tapatalk

[GuzziMoto]

Ah, nice reading an old thread.

Some general input from me.

Cars, having four wheels, are affected much differently by changes of preload to a given wheel. With four wheels, if I give one wheel more preload than the others it makes that wheel take more of the weight than the others because that wheel is trying to stick out more than the others. That wheel, if the car was upside down, would be sticking out further than the others so it is taking more of the cars weight. Imagine a table where you can make the legs different lengths. Adding preload to one wheel of a car also pushes the diagonally opposite wheel into the ground more as well, they are affected in pairs. Motorcycles lack this dynamic. Adding preload to one wheel does not have a large change on how the weight of the motorcycle is distributed. It can make very small differences, but nothing of significance as far as weight distribution. Think of a two legged table (useless, I know), changing the length of one of the two legs would make little difference in how much weight was on each leg. Preload and sag do have a large affect on the geometry of motorcycles. Adding rear preload steepens the rake and decreases the trail up front. Steeper rake makes the steering quicker, less trail makes the steering lighter. But too much, too steep a rake and / or too little trail can cause stability issues. Way back in the old days I raced a Harley 883 in a class where everyone raced the same pig of a bike. It was fun, in a weird way. But everyone was doing crazy stuff to try to make their pig dance better than the others. We would drop the front and raise the rear crazy amounts. The bike would end up being very unstable, so you fit a steering damper and cranked it up a lot. I had one nasty crash where I hit a bump in the chicane at Daytona. The 883 started head shaking so violently that I could not steer it through the rest of the chicane. It shock so hard it broke the steering stops. I did not save it, I went down hard. That was a learning experience for me, I learned to be more careful about bumps, be lighter at the handlebars (death grips = death wobbles), and run more steering damper. We also backed off the ass high thing just a little. Sometimes that is how you find the edge, by going over it.

Setting sag has a few effects. It sets the ride height of the motorcycle. It (hopefully) puts the suspension in its happy starting spot. It affects the geometry of the motorcycle, which determines steering and stability. What the rake angle is, for example, of the motorcycle while sitting there statically is not as important as what the rake angle is when you are riding it. I briefly had a Honda CTX 700 (don't laugh), and it was sagging so bad with the preload it came from the dealer with. When I (lets say over 200 lbs) would sit on it the front end would rake out even more than it was supposed to be. That did not help steering at all. I added all the rear preload it could take, and steering was much better. More balanced. Thankfully the Honda is gone.

[JRD]

GM-  great explanation of the cause and effect of increasing preload/decreasing rake/trail and its possible consequences . Thanks for posting.  

[GuzziMoto]

It is good for me to remember this crap. Helps as I get old......

The HD 883 did teach me a lot about suspension, especially about how to make bikes do things they weren't meant to. 

I also seem to remember adjusting the way the rear tire slide by adjusting the rear shock compression dampening. If I remember correctly (and I may be wrong), adding compression dampening to the rear shocks (yeah, it had TWO) made the rear tire slide earlier but more controllably (if that is a word). Less compression dampening in back gave you more grip at the rear but when it did let go it let go harder. We would run as little compression dampening as we could, for more grip. But you actually wanted some slide from the rear, so you could dial that in by adding compression dampening, The rear sliding would help the pig turn. It was a balancing act, grip vs controlled slide.

We would run as much rebound dampening as we could, that helped fight the high side that seemed to be always around the corner (so to speak). When you high side, the rear tire lets go, slides out, grips, the grip compresses the rear suspension like a giant spring (it is), then it uses that energy in the compressed spring to launch you into the air. Running rebound to the limit of what you can run without causing the suspension to pack down helped control that energy to an extent and could make the difference between saving it or not.

Not sure what, if any, relevance this has to the average street rider. I am just putting it out there for discussion.

[luhbo]

...

Not sure what, if any, relevance this has to the average street rider. I am just putting it out there for discussion.

If we would pay halve as much attention and religious efforts to suspension topics as we do to whether the battery must see 13.5 or 14.3 (and all in-between)this would be another place here

[Scud]

The time and money I have spent on suspension tends to give the greatest return in terms of enjoyment and performance - and probably also increases safety.

[andy york]

The time and money I have spent on suspension tends to give the greatest return in terms of enjoyment and performance - and probably also increases safety.

 

Ditto

[JRD]

But "high sides" make for such spectacular photographic moments As long as Im not the one in the picture!!!!!!!

[GuzziMoto]

 

...

Not sure what, if any, relevance this has to the average street rider. I am just putting it out there for discussion.

If we would pay halve as much attention and religious efforts to suspension topics as we do to whether the battery must see 13.5 or 14.3 (and all in-between)this would be another place here

 

I agree 100%. If my battery has enough charge to start the bike, that is all I care about from the battery.

Tires and suspension are far more important to me.

 

The time and money I have spent on suspension tends to give the greatest return in terms of enjoyment and performance - and probably also increases safety.

Quality suspension bits, better shocks and sometimes forks, are always money well spent. But I do admit to also truly enjoying money spent on motor. It may not have the safety aspect, but nothing puts a smile on my face than more power than I need.

 

But "high sides" make for such spectacular photographic moments As long as Im not the one in the picture!!!!!!!

That they do. As many times as I have done it, I have never had a picture of it, though. I did have a buddy of mine behind me on one such occasion. He had a lovely view of the whole thing. But alas, no pictures.

Even my wife managed one spectacular high side way back when we were parking lot racing at a BattlTrax event. She launched her V11 big time. So as a family we say, slow riders low side but the fast riders high side :-)

[68C]

Only ever one hi side, chasing my mate out of a roundabout. I remember that out of body feeling when I thought I could control it followed by the impact on the road on my left shoulder which informed me it had already all happened, that it was a flashback memory and that is was too late to do anything as I was now flat out in the road. Then came the desire to get me and the bike away away from the scene, too many years in my youth of not having all the documetaion, insurance etc.

Do not like hi sides, all too quick. Also the only time I needed an ambulance, police turned up also. About two months later I found a 'producer' (must show documents in the next week to local cop shop) in my jacket pocket, I must have been too shook up to remember them issueing it, funnily enough they never chased it up.