V11 Suspension.......Or is it Geometry

[Paul Minnaert]

well see here a picture of a 2002 le mans frame.

 

The change is just behind the head pipe.

 

 

or here a picture with on top a newly welded headpipe(not mine), and a v11 2000 frame.

 

[Guest ratchethack]

well see here a picture of a 2002 le mans frame.

 

The change is just behind the head pipe.

 

 

or here a picture with on top a newly welded headpipe(not mine), and a v11 2000 frame.

 

Paul, I can't tell if you believe this to be counter to something I've said above??

 

In fact, it fits what I've said exactly. The change behind the head pipe is 1 degree of angle only, the lengths of SWB and LWB V11 frames being the same.

 

The photo above takes us back to a similar discussion we had on this from 2 1/2 years ago here:

 

http://www.v11lemans.com/forums/index.php?...rnator&st=0

 

Other comparison measurements we took as posted in that discussion:

 

The wheelbases of my 2000 Sport and my Pal's 2004 LeMans. Mine was m 1471 and his was m 1487.

 

The distance between front tires and alternator covers were 90 mm on mine, and 106 mm on his. This accounts for the 1 degree change in rake.

 

If the LM frame were actually longer than the Sport frame, the distance between front tire and alt. cover comparison would be much greater than 16 mm, since a degree of rake contributes exactly 16 mm to the wheelbase (1487 - 1471 = 16).

 

Again, the frames are the same length (or so very close as to be within the margin of variance from one frame to the next).

 

EDIT: After looking at these photo's until I'm nearly blind, I'm now inclined to see a difference between some of the details that would account for MAYBE a couple of cm longer frame -- at the bottom of the steering head. At the top, however, because of the angle change, this difference is much smaller.

 

Now we're into the hair-splitting territory. The steering head is dropped lower on the LM also, to make up for lost ground clearance of the rake change. But now we're REALLY deep into hair splittage.

 

Yes, I now concede to a difference in actual frame length here -- but sure as the Great Guzzi Goose craps in the crystal clear waters of Lake Como at the foot of the Mighty Dolomites -- it ain't much!

[GuzziMoto]

It looks like there are a couple changes made to accomplish the rake change. It does not appear to be merely a change in rake alone. There is a step down to lower the steering stem, and the distance from the front engine mount bolt holes (atleast that is what I think they are) to the steering stem is noticeably increased by what looks to be an inch or so.

Thnks for the pics, they are worth 1,000 words each.

[Paul Minnaert]

well look at the distance between head pipe, and the front engine frame mounting. Thats more then only one degree would make. looks like + an inch in the top picture and a few mm in the bottom.

[Guest ratchethack]

well look at the distance between head pipe, and the front engine frame mounting. Thats more then only one degree would make. looks like + an inch in the top picture and a few mm in the bottom.

Hard to tell without a scale, but by the photo analysis, YOU'RE RIGHT, PAUL!

 

And after all that measurement and discussion, too.

 

Well, it just shows to go ya -- there's always a new way to look at an old frame angle. . .

 

EDIT:

 

Now here's my Q for the resident Forum mathematicians/ME's/geometric Engineers/drafting Engineers. (There was a time, and that time came and went). . . but I could sure draw it out on a large-scale drawing board and get the answer, if I had one. . . :

 

If the LM frame is ONE INCH LONGER at the spine than the "short frame" Sport, how does the difference in WHEELBASE of only 16 mm (LM over Sport, m 1,487/1,471) square with an INCREASE in fork rake, CONSIDERING that the rake of the LM against the Sport is less steep by 1 degree (26 degrees > 25 degrees)??

 

For the geometrically challenged: Assuming the LM spine is ONE INCH longer, the wheelbases should be very close to THE SAME ONE INCH APART (not quite, because the spine isn't horizontal). Now IF the rakes were THE SAME, the wheelbase difference would actually be GREATER than one inch. But since the LM has a less steep rake than the Sport, one inch longer spine PLUS the one degree rake difference should result in FAR MORE THAN ONE INCH longer wheelbase -- and yet, the wheelbase difference is only 16 mm. (??)

 

Enquiring minds. . . (well, you know). . .

[luhbo]

.... that would account for MAYBE a couple of cm longer frame -- at the bottom of the steering head. At the top, however, because of the angle change, this difference is much smaller.....

 

What a relief. Only a couple of cm. Not worth 3 pages of discussion.

 

Hubert

[mille108]

2 degrees on a 93 daytona

 

[motoguzznix]

If the LM frame is ONE INCH LONGER at the spine than the "short frame" Sport, how does the difference in WHEELBASE of only 16 mm (LM over Sport, m 1,487/1,471) square with an INCREASE in fork rake, CONSIDERING that the rake of the LM against the Sport is less steep by 1 degree (26 degrees > 25 degrees)??

 

For the geometrically challenged: Assuming the LM spine is ONE INCH longer, the wheelbases should be very close to THE SAME ONE INCH APART (not quite, because the spine isn't horizontal). Now IF the rakes were THE SAME, the wheelbase difference would actually be GREATER than one inch. But since the LM has a less steep rake than the Sport, one inch longer spine PLUS the one degree rake difference should result in FAR MORE THAN ONE INCH longer wheelbase -- and yet, the wheelbase difference is only 16 mm. (??)

 

Enquiring minds. . . (well, you know). . .

Ratch

 

I was always of the opinion that the later frame has the steeper rake angle and the frame was lenghthened to keep the alternator cover clearence. So one measure makes up for the other wheelbasewise. 1 inch longer frame, 16 mm less due to the steeper angle is a difference of approx. 9 mm. To bring one more fact on the counter: The newer bikes have the forks lenghthened which contributes to more wheelbase.

 

The difference in frame length is clearly visible as the distance of the breather hose connection to the steering head is bigger on the new frames.

[Guest ratchethack]

Thanks for the thoughts, MGNX. The later LM frame has a 26 degree rake, which is 1 degree LESS STEEP than the previous "short frame" 25 degree rake. Breather hose to steering head distance must have somehow got overlooked when we measured, it's been many years now. We measured the alternator clearance of both. The difference amounts to 16 mm, which is EXACTLY the difference in wheelbase, as measured. A difference in length of forks had not been considered previously by Yours Truly, and could explain part of the apparent discrepancy. Gets complicated, dunnit?

[motoguzznix]

Thanks for the thoughts, MGNX. The later LM frame has a 26 degree rake, which is 1 degree LESS STEEP than the previous "short frame" 25 degree rake. Breather hose to steering head distance must have somehow got overlooked when we measured, it's been many years now. We measured the alternator clearance of both. The difference amounts to 16 mm, which is EXACTLY the difference in wheelbase, as measured. A difference in length of forks had not been considered previously by Yours Truly, and could explain part of the apparent discrepancy. Gets complicated, dunnit?

Very interesting, thanks for clarification.

So Guzzi did it vice versa than I would do it and the conversions by Paul and Mille108 did it.

They lengthened the wheelbase and increased the caster by two or tree measures to make the vehicle more stable at the expense of the manoevrability. I like my lightfooted KR frame.

[Guest ratchethack]

So Guzzi did it vice versa than I would do it and the conversions by Paul and Mille108 did it.

They lengthened the wheelbase and increased the caster by two or tree measures to make the vehicle more stable at the expense of the manoevrability. I like my lightfooted KR frame.

Legend has it that when it was introduced, some Euro Photo-journo had complained about the "new" sharper handling of the 25-degree rake not being "Guzzi-like", and Mandello's response was to discontinue the "short frame" and redesign the frame jig for 26-degree rake, lest they lose sales.

 

After being accustomed to the "short frame" geometry over a period of many years, particularly after sharpening mine up somewhere near 24 degrees by raising the rear ride height 1 cm and dropping the triples, whenever I ride a 26-degree LM, it feels like a stretch limo on the straight -- very stable -- and at the same time, a real bear to wrestle through the tight stuff. But I'm pretty sure I could get used to it without too much grief. . .

[motoguzznix]

The V11 was designed by Guzzi prior to the Aprilia takeover.

 

The short frame was not stable above 150 km/h where massive speed wobble occured. Also on mine, was better with the BT010 tires and got worse with the Z6.

 

To overcome this, Aprilia launched the lenthened frame, changed the subframe front and introduced the attachments from the rear subframe to the engine. The vehicle is now absolutely stable up to topspeed, but handles slower.

 

Returning to the photo above: As you can see, the steering head is welded onto the frame in a lower position, which gives a further variation in the wheelbase department. Complicated indeed...

[Guest ratchethack]

The short frame was not stable above 150 km/h where massive speed wobble occured. Also on mine, was better with the BT010 tires and got worse with the Z6.

Hm. Despite the persistence of this Old Wive's Tale^, to my knowledge, there has never been one single credibly documented case where a short frame chassis KNOWN TO HAVE BEEN SET UP PROPERLY ever exhibited any trace of "speed wobble" (massive or otherwise). My own short frame Sport IS properly set up, and has always been rock-steady and 100% stable at all speeds up to, and over 190 kph. Due to their lack of center groove, Z6 rear tires (and others without center groove) are known for imparting a slight weave above 150 kph -- on any moto -- that has nothing to do with chassis geometry.

 

From a recently resurrected, nearly 5-year old thread nearby:

. . .If you don't have your suspension settings set right, or don't know, don't care, etc., this isn't a credible case that supports the stigma, IMHO - because again, you can get nearly any bike to headshake if it isn't sorted.

 

I certainly don't worry about it & never have, 'cause I'm confident in my chassis setup.

 

BAA TJM, but come to think of it, IMHO, YM ain't likely to V.

[Greg Field]

Different individual bikes, built to the same pattern, can exhibit different behavior. A manufacturer is responsible for all of them, so naturally the manufacturer has an interest in making them to a pattern where all will be safe. If they turn up a few examples that show problems, despite their having set them up, they must change the pattern. This is likely what happened with the V11 Sport, as it was with the LeMans 1000 and other Guzzis, including one that I am extremely familiar with: the Eldorado.

 

I have a police Eldorado that I ride the hell out of. I can go all day at 120 mph, and usually, I get no weave. Other Eldorados will wobble at 80 mph or so, as the American cops found out using them. Cops crashed and got got injured. Naturally, they complained. Guzzi did not believe them and sent over an engineer to see what was up. That guy did every set-up thing possible, and then he took the bike out for a ride. It wobbled and threw him, badly injuring him. Still not believing there was a problem, Guzzi them flew over several of the wobblers to Italy for testing. One of their ace test-riders was killed when one went into a wobble. After that, Guzzi believed there was a problem and stopped building that chassis entirely.

 

That your bike doesn't wobble and even that most of them don't is not good enough. None of them should wobble. Some do. You can believe yours doesn't wobble because of your superior abilities to set it up all you want. That doesn't make it true.

[Guest ratchethack]

I have a police Eldorado that I ride the hell out of. I can go all day at 120 mph, and usually, I get no weave. . .

 

That your bike doesn't wobble and even that most of them don't is not good enough. None of them should wobble. Some do. You can believe yours doesn't wobble because of your superior abilities to set it up all you want. That doesn't make it true.

Hmmmmm. That most (or even any) don't have ANY credible history of an inherent tendency to wobble wotsoever is not good enough for whom or what, exactly? "Usually no weave" seems to be plenty good enough for you. . .

 

I'm still waiting for the first CREDIBLY DOCUMENTED case of an inherent tendency to wobble on the short frame Sports or RMs. That would be a case where suspension sags and damping had been set up to established industry standard parameters, and any kind of inherent instability was ever credibly identified.

 

NOTE: "I heard some guy fell off his short frame" IS NOT a credibly documented case.

 

You can believe that an old Eldo model with a factory undiagnosed stability problem has anything wotsoever to do with the stability of a short frame Sport -- or any other moto -- all you want. Your belief doesn't make THAT true, either.

 

FWIW, for comparison purposes, the Guzzi V11 LMs have a 26 degree rake, short-frame Sport and RMs have a 25 degree rake, the MGS-01 has a 23.5 degree rake, and the Duc Classic has a 23 degree rake.