Geometry Change

Sorry, I’m not following you.
Change -1t on the front and you are trying to work out the effect on the rear ride height?
Do you mean because you needed to move the rear wheel back so increasing the wheelbase slightly to take up the chain slack?
Or because you will be theoretically applying more torque to the back wheel for a given throttle opening making it squat a little more?
Both of which IMO fall within the normal operating parameters of using the bike (adjusting the chain for wear, opening the throttle more without a gearing change) and are pretty much irrelevant unless you are right at the top of the MotoGP God pile.
Or did I miss something else?

 

If you moved the eccentric to make the chain the right tension the ride height has changed and the bike has got shorter/longer. If you haven’t it won’t change.

 

What year is your V4 ? Andy

 

I’m not up to speed with panigales yet. But older models you’d need to reset the ride height with the tie bar to factory or the height you like it at. But worth riding and seeing if you notice any difference: if not I wouldn’t worry

 

I ask because the 2nd iteration (yours) increased the rear ride height by (I think) 7mm over the early bike. Not that it needed quicker steering IMO. Andy

 

Doubt it’ll be noticeable on the road but it is on track when tramping on.

 

Ride height isn’t really the key issue here.

You have altered the gear ratio - and therefore changed the squat/anti-squat percentage in this case you have increased Anti-Squat - I know it sounds counter intuitive but a smaller front sprocket actually increases the lifting effect under acceleration rather than increasing squat.

Moving the rear wheel back is akin to slightly lengthening the swingarm - now in theory this would slightly raise the ride height - but not by much. However you have also increased the leverage that the swingarm can exert on the shock spring, so the cumulative effect - especially with your weight on the bike, would be negligible.

A longer swingarm also flattens the anti-squat curve - it’s a good thing and makes the finding the perfect squat/anti-squat ratio easier.

The change you have made that has the greatest effect is altering the gear ratio - in weighting terms that smaller front sprocket has a greater effect on anti-squat than any slight change in height or wheelbase. So under very hard acceleration it’s possible that grip could be reduced because you have too much anti-squat and the rear suspension extends and loses compliance.

That being said - the 2022 version of the V4 has a 4mm higher swingarm pivot to increase anti-squat - so it’s entirely plausible that the earlier bikes have a tendency to squat too much - in which case - you might be golden!

As Adam says - this only really becomes noticeable if you are riding hard enough on track to push these limits.

 

Changing the sprocket size has everything to do with altering the ride height as you will undoubtedly adjust the chain.

Rotating the eccentric to readjust the chain once you have fitted a different sprocket means the position where the spindle sit in the hub is moved around, a bit like a clock face it goes up and down. From the lowest point to the highest point can make up to 15mm difference!
The trouble is from the lowest point around 7 o'clock rotating clockwise around thought 8,9,10,11,12,1,2,3 it goes up and then starts to come down. So, for example changing from std rear up one tooth lifts the rear ride height by 3mm.
Of course putting a longer chain to extend the wheel base also altered the ride height as you adjust the eccentric.
On SSSA ducati in the past with an eccentric hub you corrected/compensated your ride height (or should do) using the ride height adjuster length, this isn't possible on a V4 as there isn't one.
Older Ducatis SSSA rear hub adjusted anti clock wise, so they went down before up.

If you have a OHLINS rear shock then you can adjust the length of the shock eye to eye but this really means removing the shock altering the length and refitting....only to find you have moved it too much....

So yes is the correct answer!

 

Ultimately you need one of these!

 

If the bike is longer why does this lift the ride height. I always believed it lowered the ride height as it flattened the angle more towards 3 o’clock from 5 o’clock

 

I didn’t know about the effect the eccentric adjuster had on ride height so was just thinking about it as a triangle - if you lengthen one side without changing the angle of then the top point is going to be raised.

To flatten the angle surely you would have to reduce shock length at the same time as extending the swingarm?

But that would be the simple way of looking at it for a double sided swingarm with extending axle block - Andy’s post just prompted me to find this which seem useful in visualising how the eccentric position effects geometry.



https://www.motospec.ca/knowledge-base/swingarm-length-reference

 

So the std rear calliper bracket won't let the centre of the rear axle go as low as the picture above which is at 6 o clock. As std it kinda works between 8 and 2 but you can see it moves both up and down and back and forth.

You also have to take into account the chain as to lengthen or shorten it you need to add or remove a male and female link pair which is a set size and therefor restricts the window it can be altered too.

Bearing in mind Pierobon have added 35mm!!!! to their modified swing arm which seems to suggest longer is the way to go (the Factory RS swing arm is a thing of beauty and is of course longer too)

Put this into account that you'll need to adjust the chain through wear and stretch and its very difficult to achieve the longest wheel base and maintain an adjustability for the chain. (unless you have the budget for a new chain every session) its a toss up on configuration, and of course there is no easy, quick and real way of maintaining a consistent ride height! still its the future!

Also lower the forks (front end) by 3 or 5 mm. You can physically see the difference that makes and I would wager a fairly competent rider would also feel... So altering the rear a similar amount is also quite a critical alteration!


(any information given may be that of a dick so choose to ignore if you like!)

 

What effect does this have on swingarm angle Andy?

AFAIK a steeper swingarm angle increases anti-squat and a shallower angle increases squat.

Just wondering how the cumulative effect of smaller front sprocket and changes to swingarm angle would pan out in the squat/anti-squat equation?

 

take the old 996 etc they really suffered with a lack of swing arm angle .long engine, short arm etc etc so I recon the fact the chain adjust was anti clockwise meant for the majority of the chin adjust the spindle was getting lower in the hub so increasing the SA angle. Not so much a problem on the V4 more compact rotated engine, longer arm, can't believe the RS etc go even longer....
on a v4 from the std chain and sprockets position adjusting the normal stretch of the chain initial reduces the SA angle a bit and lengthens the wheel base. Now I don't know if one cancels out the other I doubt it. With my bike up one tooth on the rear sprocket using the same chain (Im on a longer chain with 520 set up) meant it shortened the wheel base slightly and lowered the ride height.
It is frustrating there is no easy scope on the bike like the 998 999 1098 etc to easily return this to where you want it to be..

I did this for a concept.. and it works. I am in the process of a even more Gucci solution....

 

K5 gixer 1000 was same, AMA and other early Superbike teams extended the sa as far as poss and most teams ram right to the end of adjustment. More edge grip and the chassis was tuned to suit.

 

This one's above my pay grade but I always suspected that increasing the length between the two sprockets would increase the rear height as the swing-arm is pointing down towards the rear. But what do I know? I need enlightenment on this topic.