"old" V11 sport frame

[Guest ratchethack]

Nog, I have no experience with how air shocks work on motorcycles, but I am familiar with Boyle's Law. I'm also experienced with an air-bladder lumbar support I had in a Recaro-designed car seat. When the temp's were high, the thing ballooned up into painful range. When the temps were low, it shrunk into uselessness. I was constantly fiddling with the air pressure, well past the point of irritation.

 

Unless the Fournales shock is designed to work with an on-board compressor and continuous pressure control (doesn't look like it from the Web site), there would seem to be considerable problems conceptually with varying temp's.

 

What say you?

[Guest Nogbad]

The working pressure will rise with temperature according to the ratio of the kelvin temperature of the shock. The nominal working pressure at 20°C will be 6.8% lower at 0°C and 6.8% higher at 40°C As, I should point out, would be your tyre pressures as well.

 

These things are alleged to work well on porky cycles like H-Ds and Pan Europeans, so I would think they would be well suited to the Guzzi.

 

Anyway, bollocks to what the rest of you think, I'm ringing them on Monday and I intend to fit one if there is a unit available for the V11.

 

I downloaded their catalogue and they list the V11 Sport. I can even get the version with the solo / pillion swap valve! One press of the button and the spring is uprated.

[Guest ratchethack]

The working pressure will rise with temperature according to the ratio of the kelvin temperature of the shock. The nominal working pressure at 20°C will be 6.8% lower at 0°C and 6.8% higher at 40°C As, I should point out, would be your tyre pressures as well.

 

Are you sure about this? This seems like a very low variance to me. The old rule of thumb on tire pressures (before steel radials came along and rendered it useless) was that cold tire pressure should vary with warm riding temp. by 10%. But I believe that was relative to degrees Fahrenheit, not Kelvin.

 

Anybody got the skinny on this?

[bigbikerrick]

There is a good bit of information available at http://www.guzzitech.com/ concerning various V11 Sport handling and maintenance tips. Look under "Suspension Related". If you're looking for the wiring schematic in color (as well as for other Guzzi's), you can look at http://home.pacbell.net/guzzi007/sportissimo.html.

Carl Allison

Modesto, California

01 V11 Sport TT

97 MG Sport 1100i "Bright Red Italian Bugswatter"

97 MG California 1100i

MGNOC 17546

http://home.pacbell.net/guzzi007/sportissimo.html

Hey Carl, Did you call me at home and leave a message for me? regarding the engine on my guzzi? please email me at bigbikerrick@hotmail.com Thanks Rick Duarte

[Guest Nogbad]

Are you sure about this? This seems like a very low variance to me. The old rule of thumb on tire pressures (before radials came along and rendered it useless) was that cold tire pressure should vary with warm riding temp. by 10%. But I believe that was relative to degrees Fahrenheit, not Kelvin.

 

Anybody got the skinny on this?

 

 

(p1 x V1)/T1 = (P2 x V2)/T2

 

But the volume is constant. We will ignore the minute expansion of the shock body - OK

 

Therefore:

 

P1/T1 = P2/T2

 

And P2 = P1xT2/T1

 

Remember you have to use ABSOLUTE temperature - 0°C = 273K and Δ1°C = Δ1K

 

Then for a Fournales shock at 20°C with 220psi, what is the psi at 40°C?

 

P2 = 220 x (40+273)/(20+273)

p2 = 235psi

 

What is the % difference?

 

100 x (235-220)/220 = 6.81

 

And BTW Hatchet, whether you do the maths in °F or °C won't make a damn bit of difference, although you need to be careful with absolute temperature in Fahrenheit as it is easy to become confused.

[badmotogoozer]

Plow that furrow, Noggers, Plow It!

 

I think we should be supporting someone's venture into unknown territory. If Noggles wants to try out an air shock, why argue?? I'd like to hear how it turns out. No need to get into partial pressures and such nonsense. Strap it on and take her for a spin!

 

I always thought "ploughing my own furrow" was a lesbian term... perhaps you meant "pulling my goalie"?

 

Rj

[Guest ratchethack]

And BTW Hatchet, whether you do the maths in °F or °C won't make a damn bit of difference, although you need to be careful with absolute temperature in Fahrenheit as it is easy to become confused.

I beg you differ, my Supreme Noggatollah. Other than the question that you seem to've answered, no confusion whatsoever on my part. The ol' "10% cold-vs.-warm rule of thumb" has always been applied directly to the numbers in Fahrenheit degrees, not to absolute temperature. If applied directly to numbers on any scale other than degrees F on an absolute scale, of course it would not work out to a nice convenient 10%. There may've been a few racers who could do the calc's in absolute temp's in their heads, but I can think of a few that I'm pretty sure couldn't. . . . .

 

Thanks for the calculations. You would seem to be justified, and 6.81% would not seem to be TOO terribly significant with respect to changes in RATE over the temp range you used for illustratration.

 

Now it seems that perhaps all you need be concerned with next WRT a variable air spring is the resulting changes in laden and unladen sags, which presumably also vary with temperature.

 

Unless possibly you plan on doing exclusively 2-up riding only on warmer days and exclusively solo on cool days?

 

This is all good to think about before you commit, wouldn't you agree??

 

I'm not slamming it - it may in fact be just peachy f'er ya. Just checkin'. . . . . .

[Guest Nogbad]

 

 

 

Unless possibly you plan on doing exclusively 2-up riding only on warmer days and only solo on cool days?

 

 

 

No if you look carefully there is the option of a valve that increases the volume of the air chamber for solo riding, i.e. a bigger V gives a lower rate as the piston displacement is a smaller fraction of the total volume. For 2 up, close the valve reducing the volume and increasing the rate, so correcting the sag.

 

The physics of these things is so elegant I just have to have one.

[Guest ratchethack]

Missed that in my scan of the Web site. Intriguing indeed. . . . .

 

Reminds me of the "expansion chambers" used to augment air forks 25 years back. Never caught on. . . . .

[Guest Nogbad]

Look, here's the deal.

 

I am calling the UK distributor and getting a price for the V11 unit with the solo-duo valve.

If the price isn't too outrageous I shall order one up.

 

When and if I get it, I will put the pictures of the changeover up for the general delectation of members.

 

Then, and here is the best bit: To avoid accusations of "post purchase response" and bias if I think it handles well, I will make my bike available for testing by respected UK board members like Martin and Guzzirider so that an independent assessment of the air shock as applied to the V11 is available.

[Guest ratchethack]

. . . .To avoid accusations of "post purchase response" and bias if I think it handles well, I will make my bike available for testing by respected UK board members like Martin and Guzzirider so that an independent assessment of the air shock as applied to the V11 is available.

Fair enough!

 

But would you also let Dave ride it and give his analysis with color bar graph visual aids?

[Guest Nogbad]

Fair enough!

 

But would you also let Dave ride it and give his analysis with color bar graph visual aids?

 

Certainly not! I wouldn't want to be responsible for increasing his "carbon footprint" in the pursuit of a hobby! The only circumstances in which he could ride it would be if he needed to take his pregnant wife to hospital, and the battery in his Toyota "Pious" was flat.

[Guest ratchethack]

[dlaing]

[Martin Barrett]

Look, here's the deal.

 

I am calling the UK distributor and getting a price for the V11 unit with the solo-duo valve.

If the price isn't too outrageous I shall order one up.

 

When and if I get it, I will put the pictures of the changeover up for the general delectation of members.

 

Then, and here is the best bit: To avoid accusations of "post purchase response" and bias if I think it handles well, I will make my bike available for testing by respected UK board members like Martin and Guzzirider so that an independent assessment of the air shock as applied to the V11 is available.

 

Thankyou for holding me such high regard. But I think I'm only qualified to see how dirty a motorcycle can get. I can tell that my tyre pressures are a bit low normally when they get to about 20 psi and I'm detecting a weave in sweepers. Whilst I'm localish I'm not the man for the job unless its such an obvious improvement that I'd be bound to notice. GuzziBun is local and Baldini has a sensitive rear end but in darkest Wales.