ducatipaso.org

qldman36 wrote:surely is th geometry very important.
but the changes are not so heavy that you can recognize any bad results.

Oh yeah? Try this; Slide your forks up 3/4" in the triples and put all preload you can on your rear shock. Now find straight road and bring up to 90mph. If you survive this, let us know how it felt. This was just a geometry change.

If you survive this? That's a touch dramatic I think... proof being the changes a bike goes through under hard braking at high speeds, to the extent the rear wheel is off the ground. People live through that all the time.

Yes, geometry makes a difference. But there's nothing sacred about the factory numbers.

Wow, the twists and turns this thread takes. To start off, i was ONLY addressing Ved's statement that geometry doesn't matter, not how his particular 906 may or may not handle.
Now DesmoDog. No the factory settings are far from sacred. As a point of fact, i had bar risers made so i could raise tubes 1/4" in triples to quicken steering. 3/4"? how do you spell tank slapper? All you gotta do is hit small bump UNDER ACCELLERATION or steady throttle, not under braking to get the real definition of"tank slapper". Believe me, you'll find it very "dramatic". Not convinced? Try it. :thumbdown: [/u]

Ok but with the change you are talking about, is that geometry or just a change in tire profile - if the increase in profile of the tires between front and rear is the same, i.e the ride height is changed by the same amount front and rear then the geometry hasn't changed significantly.

:neener:

Very true Duc750, but lower only the front end as i meant all along is a significant geometry change and will be felt. Really don't understand what you mean by tire profile in this context. To me, tire profile is cross section view of tire. But that's ok, understand point you are trying to make and agree.

Sorry mate thats kind of what I mean with tyre profile.
a 130/60 -16 wil give a tyre profile of (60% * 130) = 78
a 130/70 - 16 (Blade front tyre) will give (70% *130) = 91
Standard rear = 60% * 160 = 96

So standard tyre heights are 78 front and 96 rear. the difference being 18

To keep the "standard weight distribution" whatever wheel size you get you need to keep that difference in height to keep the "standard handling" (although larger or smaller wheels will increase or decrease wheel base slightly) However fit too larger (i.e. taller) back tyre then you will get the same effect as dropping the forks through the yokes (or triple tree for those the other side of the pond!)

120/70 - 17 = 84 (+15 for the increase in wheel size)
180/55 - 17 = 99 (+ 15)
Difference = 15

120/70 -17 = 84 (+15)
170/60 - 17 = 102 (+15)
Difference = 18
SO using a 170/60 will give a slight increase in forward weight distribution and slightly more sensitive steering (which may feel quicker).
However if you then use a 907 rear swingarm which is longer this will be off set by the increased length of the swingarm.
Assuming no other core geometruy is changed like Rake or trail.

When you drop the forks through the yokes you adjust rake and trail as well as weight distribution and this is what can make the bike slap happy rather than tyre sizes although when taken to extreme or using un matched profiles a bike can be very unstable when cornering)


Srry if thats not relevant to the postings but once I started it was so much better than work !!!!!

hi guys doing this conversion at the moment.got a 4.5 rim of a 400ss.need to have bearing seat machined out .paso runs a 20mm axle compared to the more common 17mm axle.bearings are common stock.common =[17x40x11] paso =[20x42x11] can supply bearing numbers if req.rear brake hanger bracket is the sticky part for me at moment not sure which way to go .got a twin pot caliper of honda cbr 1000 which mean having a bracket made.or get a setup of a 900ss [1990]single pot brembo & hanger bracket.either way goin to have better brake than original.
Front was easy.17 in rim off 1990 900ss [300mm discs]& calipers[4 pot brembos] need speedo drive.shave approx 3mm off drive or l/h leg .make adaptor plate to mount calipers[check measurements . stagger in original caliper mounting holes on fork legs. top 13mm lower 10mm]
original speedo cable bolts straight up.make sure calipers are centred on disc.original brake lines mount up but are ugly [goin braided myself]
I have new chain & sprockets with 170/60x17 tyre not much room for error goin to run 160/60x17 myself[if tyre too wide for rim profile exagerated] remember you own a paso nothing is the same as many other Ducs but thats why we love em eh???

I am not sure that changing wheels to 17" for the 906 is that easy. The rear swingarm does not have much room with the 16" wheel anyway. I have heard that the front needs the forks lowered to allow for the larger wheel, hardly possible with the standard headstock/handlebar arrangement. Has anyone actually changed the 16" wheels to 17" or is this an urban myth?

JWilliam wrote:I am not sure that changing wheels to 17" for the 906 is that easy. The rear swingarm does not have much room with the 16" wheel anyway. I have heard that the front needs the forks lowered to allow for the larger wheel, hardly possible with the standard headstock/handlebar arrangement. Has anyone actually ch

anged the 16" wheels to 17" or is this an urban myth?

yep me doin it now .yes front end does need lowering .but 907 & 750 paso forks are only 20 mm longer if you drop 906 forks so they level with top of triplle tree you gain 15mm .this is only issue under extreme braking so wheel doesnt hit radiator .stiffer springs in forks will also help ![or more fluid] rear swinarm is tight but 160/60x17 gives good clearance.need more info contact me at ajmarshman@hotmail.com lata

No thats OK, I am using Metzeler 16" Bias belt tyres for my Paso. Not impressed by the grip characteristics of the original radial tyre - can't get them anyway!

JWilliam wrote:No thats OK, I am using Metzeler 16" Bias belt tyres for my Paso. Not impressed by the grip characteristics of the radial tyre.

Can you give us the models number of the tyres u are using, so we might at least have another avenue, thanks

Duc750 wrote:...SO using a 170/60 will give a slight increase in forward weight distribution ...When you drop the forks through the yokes you adjust rake and trail as well as weight distribution ...

Starting to work out a 17" conversion for my Paso 906. Do you know which way the effect works when you add a 907 swingarm, because i have one to put on.

I understand your explanation, so apart from the swingarm, if I drop the forks by 12mm to avoid 17" front tyre hitting radiator, then front front 120/60-17 and rear 170/60-17 would be same geometry as original 906.

Except the variable - I have the 907 swingarm, so can I presume that won't make any significant difference to the geometry so as to negatively affect the ride?

Bump !!

So what's the easist way to get 17" Wheels on the 906 ?

I started this thread awhile ago, and have finally done the swap. I ended up using a pair of zxr400 wheels 3.5 front and 4.5 rear (I think, can't remember!).
The machining required was to fit new bearings into each wheel to reuse the original axles.
Also required to make some carriers for the brake disks. This meant I could keep the original brake caliper positions and if ever required the orginal 16"ers can be bolted straight back in.
The work was done by a very clever engineer friend, but anyone who is good with a lathe should be capable. I just put it all back together.
I didn't change any geometrys.
I'll post a couple of photos when I get back home and let you know what size tyres I used.
Cheers, Rob.

here are a couple of photos.
The new disc carrier was machined out of a single piece of ally for each side and 1 for the rear as well, so that the discs would be in the same plane as the original calipers.
I've fitted new discs but they are the same as original ducati ones.
I plan on painting the whole bike next winter so will do the wheels white then as well, although the kawasaki red doens't look too bad

Tyres are 120/60 17 on 3.5" front and 160/60 17 on 4.5" rear.

Here is what I have done for my tyre solution - more than a solution - it is better handling :-). In my case when I was thinking of how to fix the tyre problem I had the opportunity to pick up a 907ie swingarm and 17" hubs, so I went the 17 " wheel way. In the first pic above I have just got the back wheel on. Now (Sep, 2011) I have both wheels on as you see below. Hope this info is of some help:


Pic 1.
- Front 4.5 hub is original ( wanted to keep it, at this stage to keep costs down).
- Front tyre: Pirelli Diablo 130/70 x 16 (this is higher profile than original)
- Rear Brembo 17" 5.5 hub is 900ss including sproket, axle.
- The rear was black - I hand painted it to keep costs down (could powder coat another time).
- Rear tyre: Pirelli Angel 170/60 x17. There is a Diablo 180/55 ZR 17 but I wanted to go with the 170 width).
- Rear brake caliper bracket for 907ie swingarm.
- 907ie swingarm with axle set
- Front forks lowered/lengthened ~8mm. With forks lengthened and higher profile front tyre it is close to 907 geometry, which has 10mm longer front forks.

Pic 2.
Copper pipe as spacer to raise front mudguard. I couldn't find suitable plastic.

Pic 3.
Benefit of lowering [edit: meaning lowing down in the triple clamp to make longer] the front forks is so there is a good space from the fairing and since 907 front forks are 10mm longer.

Pic 4.
The fork caps are not bolts - they are plastic from the local hardware shop. These are held in place with silicone (hopefully they will not fly away). These were needed, since dropping the front forks leaves the access hole open. Maybe, I could get extended fork bolts from another bike to extend the forks down more.

Pic 5.
Brembo brake upgrade - suitable, since holes in caliper bracket are smaller than on 906 swing-arm brake caliper bracket. (Edit: Needs normal, not sintered pads since still cast iron rotor - I first put on sintered ones and they overheated, ^%$&^)

Pic 6.
- Chain adjusters were second hand from a Ducati Monster. They were not an exact fit, so I had the inside lip machined to fit for $20. They are not load bearing so I figured that was fine.
- I got a new DID chain 108 links. The 906 is 106 links, so the 907 longer swingarm wants 2 extra links.
- I also got a new rear sprocket to fit my 900SS hub (Ducati 900SS 89-92 Supersprox rear sprocket) from https://www.slipstreamperformance.com.au/ selecting 40Teeth, which is the original 907ie sprocket teeth number (906 factory is also 40T).
- Also realised later, I needed to change the front sprocket to the 907ie part which is different from 906 as can see from parts catalogue for 907ie. I couldn't get an original so I got a match from http://www.jtsprockets.com

PROCEDURE (I muddled around a bit, but this is the basics of it):
- Took off fairings.
- made and put in spacers for the front mudguard.
- Lowered/made longer the front forks. to do this I referred to the workshop manual. The handles come off, three allen key bolts on each side of the forks are loosened, drop them level with the top to get about 8mm and tighten the bolts (I pushed down the back of the bike by lodging a piece of wood from the back hand rail to a ceiling rafter in the garage - which took the front wheel off the ground for the job). Covered the handle bar access gaps with the plastic bolt look-a-likes - used silicone to hold those in place.
- had new tyre put on front.
- fairings on.
- took new hub to tyre shop in car and had rear tyre put on hub.
- put new rear sprocket on hub.
- on bench checked if new rear fitted together into 907ie swing-arm.
- Fairings off, tank off.
- took off engine crankcase re-breather filter, to access inside bolt on rear exhaust.
- took off exhaust system.
- took off old rear Brembo
- took off 906 rear wheel and chain.
- took off 906 linkages at bottom of swing-arm (see also workshop Manual). There is no load up pressure, so linkages come off the rear shock easily.
- took off rubber flap connecting swing-arm to frame.
- took out swing-arm axle - it dropped out easily.
- changed the front sprocket (lock-tight on bolts)
- new 108 link chain on.
- put 907 swing-arm in according to reverse order.
- put in new wheel.
- attached brembo and bled.
- torqued all bolts as per Workshop Manual settings.
:-)

For the last job on the front, I bought new brake disks and lines, then second hand brembos (off a 907ie) from e-bay. I already had the hub, I think from a 900SS, which I hand painted white.