"old" V11 sport frame

[dlaing]

Fr chrissake just buy a decent shock,y' miserable sods

Why settle for merely decent when you can have better than that with Ohlins?

[luhbo]

...

This whole soft rear spring of the MG is frankly surprizing to me. Perhaps the engineers of those days balanced increased compression damping with softer springs, but that's not the philosophy of today.

......

 

Is it the huge unsprung mass around the Guzzi rear wheel that needs some extra damping? Could be Guzzi philosophy since 40 years now.

 

Hubert

[luhbo]

At all, reading my last posting again, this question came to my mind: how well do all these standard sag and spring settings and recommendations match with the Guzzi shaft drive. This means not only a fair amount of additional mass to be dealt with, you have also additional moments and forces and so on.

 

Strappe for instance goes into the tyniest details with stiction and so on. This is not wrong under any aspect, but on his homepage you can see that all these theorys and practical results were applied to old-school 2-stroke leisure racers and other stuff like that. Could be that these bikes behave different to at least my Guzzi.

 

Another point hereunder is the fact, that tuners over here use specially adjusted shocks just because of these big unsprung masses.

 

- I ask for your input, thanks

- My intention is to again relativate a bit the doctrins mentioned in this long thread.

 

Hubert

[Guest ratchethack]

Hubert, you raise an i important consideration here. I would also like to hear the opinions of others on this. Of course, I have my own. Just a coupla things to maybe stimulate replies.

 

The relatively large unsprung mass of the bevel drive is, IMHO, THE number-one compromise to suspension operation on the Guzzi. On top of this, the wheels themselves are very heavy, relatively speaking. How then to most effectively set up the chassis in light of this? Is there some kind of a "work around" here just for Guzzis?

 

I submit that there is NO magic combination of spring rate, preload setting, shock damping or sag numbers that is anything like a "magic bullet" that will counter the unsprung mass of the rear hub, and that there's virtually nothing we can do to make it better than it is beyond following the same principles that apply to every other suspension.

 

WRT suspension, what's the difference between a Guzzi rear wheel and a chain-driven wheel? Weight - or more accurately, mass. If there were different setup parameters for "heavy" wheels vs. "light" wheels, this'd be well-understood practice. In fact, the setup is the same for all suspensions.

 

Think of the effects of higher-than-normal spring rate on our suspensions. No, that wouldn't help matters. In fact it would make things worse. Now think of the effects of lower-than-normal spring rate. This seems to be what most of us already have from the factory. Equally bad. It makes things worse. Changing relative sag rates? Again equally bad. More comp & rebound damping? Same thing. More travel? No, we're pretty much limited there as with any shaft drive. Longer swingarm? This would seem to be helpful, but we're equally limited there. At least we have a parallelogram-type brake arm that relieves most of the rear-end jacking that formerly plagued the rigid brake designs created by the pinion climbing the crownwheel under acceleration, and it does a pretty good job of countering squat under braking as well.

 

In the end, chasing improvements in handling comes down to doing the best we can do under the considerable limitations we're given to work with. One reason I haven't been too interested in strapping-on the latest and greatest "racing suspension" gear to the front end is that the chassis is so fundamentally limited by the "boat anchor" rear end. Is there anything to be gained at all by optimizing the front end then? Well, yes, by my experience. I transformed the handling of the entire bike by up-rating fork springs by 50%. But where's the point of diminishing returns as long as the front end is attached to a boat anchor rear??? It ain't far down the track of "improvements", IMHO - and it ends not far from where you find a match of rate and sag to known optimums.

 

That's why I b'lieve the relatively low effort and expense of re-springing both front and rear to principles known to be effective under ALL limitations provides the best bang-f'er-the-buck. For practical purposes, anything you do very much beyond that is not much more than tilting at windmills, IMHO.

 

BAA, TJM & YMMV

[dlaing]

In the end, chasing improvements in handling comes down to doing the best we can do under the considerable ilimitations we're given to work with. One reason I haven't been too interested in strapping-on the latest and greatest "racing suspension" gear to the front end is that the chassis is so fundamentally limited by the "boat anchor" rear end. Is there anything to be gained at all by optimizing the front end then? Well, yes, by my experience. I transformed the handling of the entire bike by up-rating fork springs by 50%. But just how much return on effort and expense can be expected as long as the front end is attached to a boat anchor rear???

I'd much rather have the boat anchor in the stern than the bow.

Imagine having a 30# front wheel and rounding a turn and hitting washboard and or pot holes.

Atleast if the rear loses it, it is much easier to maintain control.

And if the front can handle it better when the rear loses it, you are in better shape.

 

 

Because of the shaft and weight in the rear, I would be inclined theoretically to go with more sag and heavier springs than is recommended for chain driven bikes.

This would reduce compliance and travel, but this in not necessarily a bad thing.

Our bikes have quite a bit more travel in the rear than Tontis with their twin shocks.

Keeping the rear better centered around the axle neutral point may lead to more predictable handling...at the expense of comfort

[Guest Nogbad]

How would you get more sag with a heavier spring? You can only go so far in reducing the preload.

 

Personally, reading what has been said in the last few posts, I think there is a good argument for a progressive rear spring, particularly for 2 up riding, given that most of your pillion weight is on the rear and little affects the front.

 

I'm going to keep my front as it is, maybe reducing the preload a little, and look into getting a new rear shock with a progressive spring. I wonder if anyone does an air-assisted shock that would fit? Any kind of gas spring is by definition progressive.

[Guest ratchethack]

Nog, IMHO air assist is best left for rail cars and lorries (that's boxcars and trucks f'er the Yanks ).

 

Wilbers offers full custom shocks & springs to order with progressive springs. I'm in-process of spec-ing out an order today. If you'd like to use me as y'er guinea pig, by all means feel free. FWIW, I've been warned that the US channel for custom orders is reliable, but not necessarily expedient. Will advise.

[big J]

How would you get more sag with a heavier spring? You can only go so far in reducing the preload.

 

Personally, reading what has been said in the last few posts, I think there is a good argument for a progressive rear spring, particularly for 2 up riding, given that most of your pillion weight is on the rear and little affects the front.

 

I'm going to keep my front as it is, maybe reducing the preload a little, and look into getting a new rear shock with a progressive spring. I wonder if anyone does an air-assisted shock that would fit? Any kind of gas spring is by definition progressive.

 

Contact Richard at Maxton,he'll build you a shock to your specs.When the Tenni's raced at the TT(or MGP,cant remember which)they were unable to get the Ohlins set up properly,though I dunno if this was due to parts availability.The Guzzi team switched to Maxton for the race.

I'm delighted with mine,which smooths out the worst surfaces imaginable but is still well controlled and fade free. http://www.maxtonsuspension.co.uk

[luhbo]

Nogbad, you probably wont get enough cooling to an airspringed monoshock, the more as it is hidden behind the engine.

They were available as duo shocks, but I never saw any on the road. They could't be refilled at gas stations because the average compressor could not deliver the necessary pressure.

 

Actually I cannot even mind its name...

 

Hubert

[big J]

The only air sprung shocks I can recall having any dealings with were Fournales made in France.They were ok for a day or two but leaked down slowly til there was no pressure left.The Schrader valves for adjusting pressure/adding air were different to anything I had seen before so I modified them to normal fittings.I connected them both together to maintain even pressures both sides and added a pressure guage to monitor things.They would probably have worked well if we had an onboard compressor,but we didnt.

BTW,the air pressure was for springing,compression and rebound damping was not adjustable.

[dlaing]

Nog, IMHO air assist is best left for rail cars and lorries (that's boxcars and trucks f'er the Yanks ).

 

Wilbers offers full custom shocks & springs to order with progressive springs. I'm in-process of spec-ing out an order today. If you'd like to use me as y'er guinea pig, by all means feel free. FWIW, I've been warned that the US channel for custom orders is reliable, but not necessarily expedient. Will advise.

Any chance the shock spring will be lighter sprung than the HyperPro rising rate spring?

[dlaing]

How would you get more sag with a heavier spring? You can only go so far in reducing the preload.

Exactly. Only go so far.

EDIT Note my hypercoil spring is about an inch shorter than the OEM, so lighter preload is possible

FWIW I mean more bike only sag.

Perhaps

Without rider:

Rear: Road and Track 20 mm

With rider:

Rear: Road and Track 40 mm

 

or probably too extremely

Without rider:

Rear: Road and Track 30 mm

With rider:

Rear: Road and Track 45 mm

 

compared to what I currently have:

Without rider:

Rear: Road and Track 10 mm

With rider:

Rear: Road and Track 35 mm

[motoguzznix]

Very interesting topic

 

The frame topic is focused on ride height now, so I will contribute a input to that:

 

My KR fork seems to be in line with Huberts and Nocs: I always found the front too hard (75 kg rider). I do not remember exactly the sag numbers I took some years ago, but on the front my figures were less than mentioned above. So I shortened the spacer tubes slightly to get the right numbers.

 

But that was not the main problem with the fork: The damping tube inside the left leg (compression) showed three holes drilled in the lower area, two of them drilled in opposed position. So the damping piston travels down half of its way and every damping effect of the damping valve is bypassed via the 3 holes. When you go over a hard bump, the fork moves down undamped very rapidly until the piston has passed the holes and then full damping occurs due to the high speed movement of the fork. This behavior makes a very harsh and unpleasant ride. I ended up by closing the holes with a sleeve. The adjustment srews are completely open on both sides.

Now the fork works much better, but still not perfect. Especially when braking the front moves down in a more controlled manner. Not perfect is the reaction of the fork on small bumps, it feels not sensible. The rebound damping also works sightly during the compression stroke, thats not desirable. With a more sensible front, a lot of influences would not be transmitted into the frame contributing to an unstable driving behavior of the vehicle.

 

I am thinking about Öhlins on the front......

[Guest ratchethack]

Any chance the shock spring will be lighter sprung than the HyperPro rising rate spring?

Dave, because this is a custom order, I'm assured it will be 100% make-to-order. I happen to be of fairly average weight, so I don't know if they'll just use an "off the shelf" spring, or if they wind every spring to order. Since I'm having them match the sags I get with their fork springs, it wouldn't surpirse me to get a spring that isn't given any rate at all. I've been told it'll be what I ordered - "mildly progressive", (like the fork springs) so it'll be interesting to see just how this and all my other parameters get through the demand chain and a language translation. . . .

[dlaing]

Dave, because this is a custom order, I'm assured it will be 100% make-to-order. I happen to be of fairly average weight, so I don't know if they'll just use an "off the shelf" spring, or if they wind every spring to order. Since I'm having them match the sags I get with their fork springs, it wouldn't surpirse me to get a spring that isn't given any rate at all. I've been told it'll be what I ordered - "mildly progressive", (like the fork springs) so it'll be interesting to see just how this and all my other parameters get through the demand chain and a language translation. . . .

If Wilbers could build the shock to Ohlins dimensions (286mm length 70mm stroke) or even Sachs 276/60 or WP 280/64 and put a softer spring on it than HyperPro does, I would place my order tomorrow!

Chris Beauchemin wrote a nice write-up on the Wilbers Shock where he determined the travel was 58mm

http://www.v11lemans.com/forums/index.php?...ic=5898&hl=