22+ V4 chassis geometry

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SuperDomestique said:
I’ll give it a shot. I’m all about less is more. Will consciously think about countersteering mid-corner a bit more
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I’m not sure you want to add counter steer mid-corner, that may upset the bike…for me it’s add more bar counter steer input on initial turn in…which means you are cutting it to the apex faster with a more aggressive/quicker tip in, and ultimately more lean angle as you reach the apex.

You are still keeping the same line and braking zone, and are turning in at the same point, so the distance from your turn in point to to apex is the same, but because the starting tip in is faster and more aggressive the bike gets to a greater lean angle faster… it closes down on the apex faster and easier. You still need to be smooth with the bar input, just add more and slightly quicker bar input on initial turn in.
 
Steven31371 said:
I’m not sure you want to add counter steer mid-corner, that may upset the bike…for me it’s add more bar counter steer input on initial turn in…which means you are cutting it to the apex faster with a more aggressive/quicker tip in, and ultimately more lean angle as you reach the apex.

You are still keeping the same line and braking zone, and are turning in at the same point, so the distance from your turn in point to to apex is the same, but because the starting tip in is faster and more aggressive the bike gets to a greater lean angle faster… it closes down on the apex faster and easier. You still need to be smooth with the bar input, just add more and slightly quicker bar input on initial turn in.
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Wouldn’t reducing trail help this phenomenon?

One of the funnest bikes I ever rode was my 2007 Daytona 675. It was so easy to ride and cornering was almost telepathic. I just looked up the trail figures on that bike and it’s 89 mm. Granted the 675 has 90 less hp. But I’d like to go more in that direction
 
Why don't you just change the fork height between sessions and see what works better. And sometimes a cg change can be transformative. If these were like ducati's of old you could change rear ride height in about 5 minutes and try that in different sessions. I have the front height on my bike the same as the 22's and have raised the rear about 10 mm. Should put the head at about 24 degrees. Totally neutral, you set it on a line in the corner and you can pretty much take your hands off the bars. Needs a tiny bit of force to hold it down trailing in but that's the tire. So make small changes between sessions, one change at a time.
 
baggerman said:
Why don't you just change the fork height between sessions and see what works better. And sometimes a cg change can be transformative. If these were like ducati's of old you could change rear ride height in about 5 minutes and try that in different sessions. I have the front height on my bike the same as the 22's and have raised the rear about 10 mm. SHOULD put the head at about 24 degrees. Totally neutral, you set it on a line in the corner and you can pretty much take your hands off the bars. Needs a tiny bit of force to hold it down trailing in but that's the tire. So make small changes between sessions, one change at a time.
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Is that should a definite maybe?…
 
The wheelbase is 57.8 inches (the radius). 2 pi R= 363. 363/360= 1.008. So raising the rear 1 inch would change the rake about 1 degree. What's your question?
 
baggerman said:
The wheelbase is 57.8 inches (the radius). 2 pi R= 363. 363/360= 1.008. So raising the rear 1 inch would change the rake about 1 degree. What's your question?
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'about' then not 'should'......

oh and 1 inch.....25mm :eek: what rear ride height is that? What does motospec say?
 
andyb said:
'about' then not 'should'......

oh and 1 inch.....25mm :eek: what rear ride height is that? What does motospec say?
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I don't measure the chassis, I simply change stuff until the bike works like I want. I think this is the reason that no one else realized that Ducati was lying about the SF chassis specs. I couldn't fix it, didn't make sense to me.
 
I did a little more digging into the '24 V4RS front geometry (at least from the start of the season where I can find good photos). If my assumptions and calculations are correct, Bautista is running a 25 mm offset and effective 23º rake (Corse offer 23.5º bearing cups so that jibes). These figures would translate into approximately 99 mm trail with the guesstimated tire radius of 298 mm for a 125/70 Diablo SC slick (610 mm per Pirelli's guide). So 99 mm of trail seems to be the golden number for trail.

To get to 99 mm trail on a stock V4S, you'll need a rake of 24.1º. To get to this will require a 2.25 mm fork drop which is inline with what Rick did to speed up the steering on his bike.
 
We may be into the weeds, but model year specs matter.

2022 and + bike have a different fork travel.

I'm having trouble getting to that 100mm number with the measurements I have. Did you measure front tire circumference and convert that to radius?
 
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SBK-SP said:
Yes, but is it split upper/lower, all upper, or all lower…?
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I don’t know if I’m understanding your question. 5mm more travel merely means there’s more travel from fully extended to fully collapsed. I don’t really think that matters outside of examining rake and trail numbers when the forks are fully extended or fully collapsed.
 
SuperDomestique said:
I did a little more digging into the '24 V4RS front geometry (at least from the start of the season where I can find good photos). If my assumptions and calculations are correct, Bautista is running a 25 mm offset and effective 23º rake (Corse offer 23.5º bearing cups so that jibes). These figures would translate into approximately 99 mm trail with the guesstimated tire radius of 298 mm for a 125/70 Diablo SC slick (610 mm per Pirelli's guide). So 99 mm of trail seems to be the golden number for trail.

To get to 99 mm trail on a stock V4S, you'll need a rake of 24.1º. To get to this will require a 2.25 mm fork drop which is inline with what Rick did to speed up the steering on his bike.
Click to expand...

So put stock SF ones which are 26.5 degrees in backwards (they're cheap relative to the corse ones). Gives you 22.5 degrees. Raise the fork, lower the rear and you're at 23 degrees. If it doesn't turn now may I suggest push-ups. Andy made a nice pair of 24 bushings (23.5?). But I'm thinking it's not likely he'll make you a set.
 
SuperDomestique said:
To get to 99 mm trail on a stock V4S, you'll need a rake of 24.1º. To get to this will require a 2.25 mm fork drop which is inline with what Rick did to speed up the steering on his bike.
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I actually have mine steeper. Probably in the high 23's. I was watching one of the WSB interviews and whoever it was said "I'm a short trail kinda of guy. Some others may find this too twichy". This is a track adjusted sort of thing anyway. But running it real steep to get exit speed on chicanes on some tracks make total sense.
 
bp_SFV4 said:
I don’t know if I’m understanding your question. 5mm more travel merely means there’s more travel from fully extended to fully collapsed. I don’t really think that matters outside of examining rake and trail numbers when the forks are fully extended or fully collapsed.
Click to expand...

Im talking about the positioning of the forks from the factory. Yes, they say they are 5mm longer, but what is the overall effect? As in the fork positioning in the clamps may or may not affect the actual length 5mm as the top-out spring, main spring, and preload tube(if any) can affect the functional length.

Their “5mm more travel” may have many additional impacts that aren’t mentioned.
 
baggerman said:
So put stock SF ones which are 26.5 degrees in backwards (they're cheap relative to the corse ones). Gives you 22.5 degrees. Raise the fork, lower the rear and you're at 23 degrees. If it doesn't turn now may I suggest push-ups. Andy made a nice pair of 24 bushings (23.5?). But I'm thinking it's not likely he'll make you a set.
Click to expand...

Not sure why you’d need to make them… You can buy them https://www.forza-moto.com/en/p/3726+ducati-corse-special-frame-bush-for-steering-1199rs-v4rs
 
SBK-SP said:
Im talking about the positioning of the forks from the factory. Yes, they say they are 5mm longer, but what is the overall effect? As in the fork positioning in the clamps may or may not affect the actual length 5mm as the top-out spring, main spring, and preload tube(if any) can affect the functional length.

Their “5mm more travel” may have many additional impacts that aren’t mentioned.
Click to expand...
I don’t think 5mm more travel necessarily equates to 5mm longer overall. The forks on the 2022+ V4S look like they have the same 4mm of fork tube above the top clamp as my 2021 which was the last year to use the non gas charged Ohlins fork that didn’t have the longer travel.
 

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