Shock fitment differences

[Lucky Phil]

43 minutes ago, docc said:

So . . . no one has volunteered to perform the assigned geometry problem, yet . . .

But, we can agree that increased shock length approximately is doubled in ride height?

 

Double ish 

 

Phil

[GuzziMoto]

17 hours ago, docc said:

So . . . no one has volunteered to perform the assigned geometry problem, yet . . .

But, we can agree that increased shock length approximately is doubled in ride height?

 

Yes, it would be close to double. If shock travel is 2" and rear suspension travel is 4" that would be a two to one ratio, and that would mean a 5mm increase in shock length would equal a 10mm increase in rear ride height. The only fly in the ointment is that it is not consistent throughout travel. The ratio changes as the rear swingarm goes through its travel. The ratio should start lower and increase as the rear swingarm goes through its travel (raising rate). The one factor not shown in your diagram that is important is the shock itself. The angle the shock runs at also plays a part in how the ratio changes through travel. But rounding it to double, or "doubleish" as Phil said, would be safe. The other thing that would cause the actual results to deviate is that the seat is not all the way at the back of the back over the rear axle. So an increase of 10mm of rear ride height would not mean the seat is 10mm higher, it would probably be something like 9mm higher.

Most of my experience with Ohlins is with the higher end Ohlins stuff. I have never had a bike that came with Ohlins out of the box. But I get that the OEM Ohlins stuff is not as nice as the custom Ohlins stuff. It kinda seems like it could be no other way. No doubt the OEM Ohlins stiff is better then the standard OEM stuff, but that gap does seem to be closing. All the Ohlins stuff I have used has been custom. Some of it has been more custom then others, but it was all high end stuff. The forks on one of our race Ducati's came off a Kawasaki superbike. It is a sweet piece of kit, it worked amazingly well. As Phil mentioned, the Penske stuff is also high end. And it is built to be fully serviceable. Having a fixed length shock that is longer then stock is fine. But better is having a shock with an adjustable length that allows you to adjust from stock Sachs length to longer, or even shorter then stock length if you are on the short side. It is better to be able to adjust the length of the shock then to use preload to set seat height. Preload should be set based on weight, not based on height.

[docc]

On 12/30/2023 at 4:12 PM, docc said:

Engineering professor:

                    "When a deflection of 6mm is applied in the x-axis to the

                             upper mounting point, calculate the mm change

                           in position of the rear mounting point in the y-axis:"

Student (docc):

                       "Er, doubl-ish?"

Engineering professor:

                            "Young man, have you considered a transfer to the Business College?"

[docc]

I see the published seat height of the short frame V11 Sport, 1999-2001, is 800mm (31 1/2").

My Öhlins (not the OEM Guzzi part) is 5.5mm longer than the Sachs and the seat height is ~819mm (32 1/4").

So, my ride height increased about triple the change in shock length, but I went with a significantly stiffer spring and chose a more aggressive rider sag (25%) for the rear.

I suspect without the stronger spring and increased preload (if only the shock length changed), the change in ride height would have been about (well, you know):

 "double-ish"

 

[GuzziMoto]

20 hours ago, docc said:

I see the published seat height of the short frame V11 Sport, 1999-2001, is 800mm (31 1/2").

My Öhlins (not the OEM Guzzi part) is 5.5mm longer than the Sachs and the seat height is ~819mm (32 1/4").

So, my ride height increased about triple the change in shock length, but I went with a significantly stiffer spring and chose a more aggressive rider sag (25%) for the rear.

I suspect without the stronger spring and increased preload (if only the shock length changed), the change in ride height would have been about (well, you know):

 "double-ish"

 

Bingo.

The shock length certainly affects ride height. So does the spring rate and corresponding preload of the spring, which sets sag. There is not one single factor that determines seat height. All the various factors contribute. You can change one factor, like a shorter or longer shock, and if everything else stays the same the change in ride height should be predictable. But often changes like a new shock that is longer or shorter accompany other changes like a new spring that is stiffer or softer and different preload to get a different sag amount. It is possible to run a longer shock (5mm longer) and simply have 10mm more sag because you are running a different spring and preload combination resulting in the same seat height you had with the shorter shock. That said, the generally positive improvements of running a longer shock, quicker steering, won't really be delivered if you don't also have a corresponding increase in rear ride height with the longer shock combination you switch to.Running a longer shock without the small increase in rear ride height it tends to deliver won't deliver the improvements in steering that a longer shock can. But you can get similar improvements without a longer shock simply by running a spring / preload combination that increase rear ride height by 10mm or so. It is a more complete improvement if you run the longer shock with the correct spring / preload combination. But a similar improvement can be achieved by swapping out the spring and setting preload to get the desired increase in rear ride height.

[mjseymo]

This is all really useful stuff, the ride height and the effects of different shock lengths to rider experience. Also peopel oftne drop the front forks in the triple clamps by 2 - 3mm to sharpen up the steering. I wonder how the combination of the two work together to get a happy set up?

 

[GuzziMoto]

4 hours ago, mjseymo said:

This is all really useful stuff, the ride height and the effects of different shock lengths to rider experience. Also peopel oftne drop the front forks in the triple clamps by 2 - 3mm to sharpen up the steering. I wonder how the combination of the two work together to get a happy set up?

 

Both dropping the forks and a longer shock are common mods for the V11. But usually it is one or the other. That said, there is nothing that says you can't do both. But just because some is good doesn't always mean more is better. Both dropping the front forks and a longer rear shock reduce trail. Trail is a big part of what make the motorcycle stable. Too little trail can lead to stability issues. So, there is a point where more is not better, at least when it comes to this.

That is one reason why I prefer an adjustable length shock to a fixed length longer shock. But if the shock length is fixed you can always use the fork height adjustment and the preload adjustment to get the steering where you want it.

[docc]

With the 5.5 mm  longer shock on my ShortFrame Sport, the forks are raised 5mm. With my spring selections and "sags" (30% front/25% rear), I found this all a sweet spot.

As @GuzziMoto said, more fork raise was not better (for my set-up)......

[GuzziMoto]

3 minutes ago, docc said:

With the 5.5 mm  longer shock on my ShortFrame Sport, the forks are raised 5mm. With my spring selections and "sags" (30% front/25% rear), i found this all a sweet spot.

As @GuzziMoto said, more fork raise was not better (for my set-up)......

I think when you say "forks are raised 5mm" you mean the triple clamps are slid down the fork tubes 5mm, so that the front end is 5mm lower, right?

When you say "raised" you mean the fork tubes relative to the triple clamps, I think.

10mm - 15mm is a common amount to lower the front end, but raising the rear end means less lowering of the front end would be required to achieve the same result. 10mm higher at the back along with 5mm lower at the front is roughly the same as 15mm lower at the front as far as steering goes,  while not costing you the ground clearance that only lowering the front 15mm would have cost.

Back when I raced a HD 883 we ran way longer shocks in back AND lowered the front to try to get the bike to turn faster. But you were flirting with the limits of not having enough trail. Stability was often an issue.

[LaGrasta]

My front is lowered 15mm. I experimented a lot until I found this sweet spot. I was comparing the 2003 V11 to my 2010 V7, which handles amazing. After I landed on 15mm, I discovered GuzziTech advises exactly the same. Do a search for my thread for more specifics, if interested.

I still desperately need more preload, but the overall handling, with OEM forks and shocks, are acceptable. I'm wondering if I should replace 2 inches of spring with 2 inches of spacer. I did this with other bikes with great success.

 

 

[docc]

2 hours ago, LaGrasta said:

My front is lowered 15mm. I experimented a lot until I found this sweet spot. I was comparing the 2003 V11 to my 2010 V7, which handles amazing. After I landed on 15mm, I discovered GuzziTech advises exactly the same. Do a search for my thread for more specifics, if interested.

I still desperately need more preload, but the overall handling, with OEM forks and shocks, are acceptable. I'm wondering if I should replace 2 inches of spring with 2 inches of spacer. I did this with other bikes with great success.

 

 

First priority: get the right springs. More preload will not solve that. I had to learn this "the hard way" . . .

[Pressureangle]

Shock length... a thread of landmines the likes of tires and oil.

The difference between a long and a short shock where the ride height is identical, is zero until you find the circumstance in which the longer shock can extend further than the shorter shock. (or bottom out, but that's dirt stuff)  The shorthand of this is that on-road, the only time you'll see a difference is when you're turning on the brakes, hard. A longer shock allows the rear to rise further before the weight of the rear wheel comes into play, which in turn reduces rake and generally eases turn-in. 

[LaGrasta]

@docc let's define "that".

When riding down the street, straight or in turns, the bike handles as well as I expect for stock suspension. However, when first striking a surface change such as when I encounter the street transition from my sloped driveway, it slams. To avoid it, I gingerly brake and roll over this transition each time I leave my drive. But again, once on the road, it seems fine.

My guess is the springs need to be more firm during a harsh transition. Is this indeed, preload?

[audiomick]

57 minutes ago, LaGrasta said:

My guess is the springs need to be more firm... Is this indeed, preload?

No.

Preload can help to get the ride height right, as long as the springs have approximately the right rate.

If you are bottoming out regularly, the spring rate is perhaps too soft, or the springs have maybe lost something due to age.

 

Having said that, I'm nor exactly a suspension Guru, but I believe that is correct.

[LaGrasta]

They never bottom out while riding, unless I nail a pothole hard! In fact, I'd say they feel really good on-road. I usually only notice during on a slow roll, over a harsh transition. I'm only 165lbs, so the stock spring rate should be perfect for my weight. As for being old, I'm not sure steel loses tensile strength like that, but maybe.