Triple clamp musings.

[Lucky Phil]

1 hour ago, docc said:

Seriously, this tuition so informs the reports and concerns about the earliest V11 Sports showing bad handling behavior. Was it a "1/2º change in the cant" of the triples?

That has long been disputed as unlikely.

Was it the holdover of 45mm offset triples that had been used on 26º 1100 Sport spine frames, then did not work well on the 25º V11 ShortFrames that benefited from a 40mm offset?

Would the change from a 26º frame with 45mm offset to a 25º frame with that same 45mm offset = that "1/2 degree" that has been of so much concern?

 

 

So here's my calculation docc. A std 1100ie Sport 26deg/45mm offset combination has approx trail of 96mm. If someone has the guaranteed actual figure let me know. Working on the same assumptions for fork length and front tyre OD a std V11 Sport with a 25deg/40mm offset triple also has 96mm trail. Now if you use a set of 1100ie Sport triples with 45mm offset on the V11 Sport so you get a 25deg/45mm offset combo you end up with 90mm of trail. A significant difference towards the "sharper steering" end of the spectrum. My 1198 has 30mm offset aftermarket triple clamps down from the std 36mm offset so it steers better on the track and doesn't push the front on corner exit on the throttle. That 6mm on the Ducati makes a lot of difference to the steering so 5mm offset and 6mm trail on the Guzzi V11 is a significant change to the steering and stability. I think this is probably whats happened back on the early bikes. We'll know for certain when I pull the triples on my bike after I get the replacement forks sorted and I can measure the supposed "cant" on my bikes original triples. 

If you had a std V11 Sport 25/40 set up and canted the triples 1/2 deg you'd go from 96mm to 103mm trail. If you instead opened the head angle to 25.5 you'd go from 96mm to 99mm trail.

If you had 1100ie 45mm triples on a V11 sport and you "canted" the triples 1/2 degree you'd end up with 97.5mm trail from 90mm. Seems to me the most likely scenario is they started with 1100ie Sport triples at 45mm offset and then due to customer/journalist feedback increased the trail from 90mm to 96mm by virtue of 40mm offset triple clamps to bring the figures back to the same as a std 1100ie Sport.

Ciao     

 

[nobleswood]

My V11 Sport is the 2003 model sold as a 2004. It has the 43mm Marzocchi forks & is the KT model.

So from your discussion I understand that, for my bike, the head angle is 25*, the offset is 40 mm. Now written in my notes, from where I don’t know, I have a trail of 103mm. Should that be 96mm ?

Having the Griso & the V11, I’m trying to educate myself about these details, as the two bikes steer differently & trying to understand the mathematics behind the riding feel. Especially as I change the forks &  potentially the geometry.

[Lucky Phil]

1 minute ago, nobleswood said:

My V11 Sport is the 2003 model sold as a 2004. It has the 43mm Marzocchi forks & is the KT model.

So from your discussion I understand that, for my bike, the head angle is 25*, the offset is 40 mm. Now written in my notes, from where I don’t know, I have a trail of 103mm. Should that be 96mm ?

Having the Griso & the V11, I’m trying to educate myself about these details, as the two bikes steer differently & trying to understand the mathematics behind the riding feel. Especially as I change the forks &  potentially the geometry.

I assume so from my calculations but I'm open to being corrected by attributable material. In broad terms it's not a major issue if my actual figures aren't exactly correct it's more about the differential between the various permutations based on the same baseline data I used.

Ciao

 

[nobleswood]

It's these subtlies that I'm interested in as I try to understand the different values between the Griso & V11 

Wheelbase V11: 1490

                   Griso: 1554

Head angle V11; 25

                   Griso; 26.5

Offset V11; 40 mm

                  Griso; 35mm

Trail V11; 103mm

                  Griso: 108mm

 

Yet the V11 steers as if it has more trail. The Griso acts as if the steering is very 'light' & is quick to turn in.

Sorry to go off topic , it's just interesting & currently head scratching

[Lucky Phil]

16 minutes ago, nobleswood said:

It's these subtlies that I'm interested in as I try to understand the different values between the Griso & V11 

Wheelbase V11: 1490

                   Griso: 1554

Head angle V11; 25

                   Griso; 26.5

Offset V11; 40 mm

                  Griso; 35mm

Trail V11; 103mm

                  Griso: 108mm

 

Yet the V11 steers as if it has more trail. The Griso acts as if the steering is very 'light' & is quick to turn in.

Sorry to go off topic , it's just interesting & currently head scratching

My calcs must be pretty close as I get the Griso at 110mm trail using assumptions about front tyre dimensions and fork length.

Remember a Griso uses traditional style wide handlebars compared to a v11 clipon style as well which gives more leverage.

Ciao 

[nobleswood]

Front tyre inflated to 36 psi

V11 Circumference 1883mm Diameter 600mm

Griso circumference 1878mm Diameter 598mm

 

Fork length, I believe I measured this with the front wheel off the ground, from top of triple tree to center of axle

V11; 750mm

Griso; 725 mm

[Lucky Phil]

2 hours ago, nobleswood said:

Front tyre inflated to 36 psi

V11 Circumference 1883mm Diameter 600mm

Griso circumference 1878mm Diameter 598mm

 

Fork length, I believe I measured this with the front wheel off the ground, from top of triple tree to center of axle

V11; 750mm

Griso; 725 mm

With your figures I get 109.982 trail for the Griso and 95.758 for the V11.

Ciao

[nobleswood]

That confirms the numbers then. 

On my Sport I have the LSL handlebars & risers to sit up more, rather than the clip-ons.

[Lucky Phil]

26 minutes ago, nobleswood said:

That confirms the numbers then. 

On my Sport I have the LSL handlebars & risers to sit up more, rather than the clip-ons.

Yes so the V11 figures should be pretty close.

Ciao

[Lucky Phil]

Ok so I've had to delete my last post on this because it was wrong. I have established without doubt that the later V11 sport triple clamps are indeed "canted" or more correctly have a built in negative rake. You can fairly easily check what your bike has by a measurement insitu. I have a new set of the later black triples and you can confirm by measuring the steering stem hole location in the bottom clamp. If you measure from the edge of the stem hole OD to the front and aft edges of the oval flat face the newer raked clamps measure  11mm and 16mm respectively where the older 0 rake forks measure 13mm and 14mm. So Guzzi have moved the stem forward 2mm in the new lower triple clamps effectively steepening the angle in the lower clamp and left the top clamp the same. So 40mm offset on the top clamp and 38mm for the lower. They have of course machined the fork leg bores at a fractional angle to allow for this so you cant mix and match new and old clamps.

Here's an image of a later clamp base and you can see the stem hole is obviously off set on the machined flat face. The earlier lower clamps have the stem hole more centred by 2mm. The effect of this negative offset is to give the bike more trail. How much I don't know but it may also clear up some of the wheel base question marks as well between the bikes which I think have been discussed aside from the long/short frame variations.

 

[motortouring]

6 hours ago, Lucky Phil said:

Ok so I've had to delete my last post on this because it was wrong. I have established without doubt that the later V11 sport triple clamps are indeed "canted" or more correctly have a built in negative rake. You can fairly easily check what your bike has by a measurement insitu. I have a new set of the later black triples and you can confirm by measuring the steering stem hole location in the bottom clamp. If you measure from the edge of the stem hole OD to the front and aft edges of the oval flat face the newer raked clamps measure  11mm and 16mm respectively where the older 0 rake forks measure 13mm and 14mm. So Guzzi have moved the stem forward 2mm in the new lower triple clamps effectively steepening the angle in the lower clamp and left the top clamp the same. So 40mm offset on the top clamp and 38mm for the lower. They have of course machined the fork leg bores at a fractional angle to allow for this so you cant mix and match new and old clamps.

Here's an image of a later clamp base and you can see the stem hole is obviously off set on the machined flat face. The earlier lower clamps have the stem hole more centred by 2mm. The effect of this negative offset is to give the bike more trail. How much I don't know but it may also clear up some of the wheel base question marks as well between the bikes which I think have been discussed aside from the long/short frame variations.

 

Very interesting!! The first proof I have seen. I am going to the shed this evening to measure. I have a 1999(KR, redframe) and a 2002 (KS)

[motortouring]

It is maybe a bit difficult to see, but the aluminium colored is 44mm and the black is 42,.. mm

Very provisional measurement.

The reference is the frontside of the triple clamp and the inside of the triple clamp tube. 

So the rake is smaller for the later models. It will give 8mm more  trail(estimate). 

[motortouring]

On 2/4/2022 at 12:45 AM, Lucky Phil said:

My calcs must be pretty close as I get the Griso at 110mm trail using assumptions about front tyre dimensions and fork length.

Remember a Griso uses traditional style wide handlebars compared to a v11 clipon style as well which gives more leverage.

Ciao 

I think fork length is not in the equation.

[Lucky Phil]

7 minutes ago, motortouring said:

I think fork length is not in the equation.

No it is involved. Here is a calculator for example.

https://www.rbracing-rsr.com/rakeandtrail.html

[motortouring]

15 minutes ago, Lucky Phil said:

No it is involved. Here is a calculator for example.

https://www.rbracing-rsr.com/rakeandtrail.html

O yes, you are right. This is because the steering head and fork are not parallel.

And I finally understand the difference between offset and rake.