S2R 800 Brakes and 749S forks...not working together, happily in harmony...

[yosso]

Hi,

Bike: 2000 M750
Forks: 2004 749S
Brakes (calipers and rotors): 2005 S2R800

After spending several weeks trying to get my brakes bled (see my earlier post ) I finally realized that the bleeding is fine, and that it is the mounting of the calipers to the forks that is causing my limp and flaccid lever.  If the caliper mounting bolts are not tightened, the lever is firm, but as soon as the bolts are tightened with or without spacers the lever will no longer be firm, i.e. it will go completely to the grip. 

I've removed the wheel and measured the caliper spacing and disc spacing and ran the numbers and I came up with a 3.67mm spacer thickness which doesn't match the 5mm that has been discussed (but never actually verified) on the forums. 

Just to throw another log on the fire, I also measured the distance from the mounting flange to the rotor surface and it appears as if the top mounting bolt is 3mm farther from the rotor than the lower mounting bolt on both forks. (2.005" at lower bolt and 2.124" at the upper bolt)

Does anyone know if that's normal for the 749S forks or do I have a tweaked mounting flange on both forks?

Thank you for any and all assistance.

Mike

[Raux]

discovered with my help
no but glad you finally got to the root cause.

have you checked if your rotors are warped. ie rotate the wheel around and measure the distance at different parts on the rotor and see if you are still getting the same measurements.

are the 749 forks off a wrecked bike?

are the measurements consistent on both forks?

I suppose the 5mm could be a theoretical number. it's based on brake rotor offset of the 10mm normal bike vs 15mm superbike.

[Slide Panda]

Did the 749S use the narrow band rotors anyone?

[yosso]

discovered with my help
no but glad you finally got to the root cause.

Yep, and I greatly appreciate your assistance.

have you checked if your rotors are warped. ie rotate the wheel around and measure the distance at different parts on the rotor and see if you are still getting the same measurements.

are the 749 forks off a wrecked bike?

I rotated the wheel and checked the measurements at six locations, and I ended up with a fairly consistent values, but as I can't find my Grizzley el-cheapo dial gauge I was unable to check the runout.  But from the six measurements I had a standard deviation of 0.002" on the left and 0.004" on the right.

are the 749 forks off a wrecked bike?

Yep, one of the forks (the left) was slightly tweaked and I took it apart and had the lower straightened by an local mechanic/machinist, but now I'm thinking about sending off both forks to a professional, to see if the mounting bracket can be straightened on both forks.

are the measurements consistent on both forks?

I suppose the 5mm could be a theoretical number. it's based on brake rotor offset of the 10mm normal bike vs 15mm superbike.

The left side has a average delta of 2.48mm, while the right side has an average delta of 3.30mm.

FWIW, the 300mm S2R rotors don't appear to have any offset, my original 330mm rotor has some offset.

I guess I can always put the stock forks back in place and simply shim the upper triple or source a factory triple. 

There's another pair of 749 forks on Ebay right now...it's only money, right?   

SWMBO is going to kill me. 

[ducatiz]

For some reason, I thought the offset was due to the calipers, not the mounts.. thus if you put 749s calipers on an S2R's stock forks, you had to get the narrow band rotors... am i wrong?

[He Man]

theres a difference between S2R and S2R1000 rotors. the 749 calipers is a bolt on for the S2R1000 rotors. Thats because they both have the same offset.

the S2r800 IRRC has no offset on the rotor, so you would need to either add shims or get the correct motor.

[Raux]

all monster rotors are 10mm offset.

the forks carry the offset. that's why you can't put a superbike wheel on a monster without superbike forks. well there are ways, but not plug and play.

he's using monster calipers and rotors so no issue with narrow band

[ducatiz]

all monster rotors are 10mm offset.

the forks carry the offset. that's why you can't put a superbike wheel on a monster without superbike forks. well there are ways, but not plug and play.

he's using monster calipers and rotors so no issue with narrow band

S2R800s with 300mm rotors are definitely not 10mm offset.

[Raux]

S2R800s with 300mm rotors are definitely not 10mm offset.

ahhh my mistake. then it's all the 320s are 10mm

[Raux]

still puts him in the same situation with the rotor offset being wrong for the forks then.

so he just needs to make sure everything is straight, not warped or bent. and then add the correct spacers, based on his measurements and not my theoretical BS  to line it all up.

[suzyj]

There's another pair of 749 forks on Ebay right now...it's only money, right?  

Go for 748/998 forks.  They work seamlessly with both 300mm rotors and 2 pot calipers (as I had originally on my 695) and with 320mm rotors and 4 pot calipers.  No spacers required.

Of course the top is a bit more work, but it's the same work you'd be doing with the 749/999 forks anyway.

Here's the thread about mine:

http://ducatimonsterforum.org/index.php?topic=41414.msg740226#msg740226

Here's what they look like on my 695 with new 320mm rotors and goldline calipers - no spacers



And finally a picture with my original 300mm rotors and 2 pot calipers - again no spacers:

[yosso]

Go for 748/998 forks.  They work seamlessly with both 300mm rotors and 2 pot calipers (as I had originally on my 695) and with 320mm rotors and 4 pot calipers.  No spacers required.

Of course the top is a bit more work, but it's the same work you'd be doing with the 749/999 forks anyway.


Here's the thread about mine:

http://ducatimonsterforum.org/index.php?topic=41414.msg740226#msg740226

Yep, read your thread earlier, very nice and helpful,

There is a set of  748 forks for sale on ebay..but I really don't want to go with clip-ons at this time.  So I'll stick w/trying to fix what I've already got in hand.

I did manage to tweak the mounting flanges to within 0.006 on one side and not so good on the other side using some 3/8-16 threaded rod, one in the lower holes to keep them in position, and a second rod in the upper hole to try to draw the flange to the correct position...but that's not close enough.  So I'll try to see what one of the professional fork straighteners might charge (or if it's even possible) to straighten the flanges.

Again, I appreciate all the help and advice.

Mike

[yosso]

Just an update (in case anyone cars  ).

<whining>
I pulled the SBK forks off to be fixed by a pro and was planning on using the stock forks in the bored upper triple with the appropriate shims.  Upon reinstalling the stock forks I discovered another problem...the boring of the upper triple is off on one side, so now I'm needing a new stock upper triple.  Sigh, it never ends.
</whining>

Anyway, hopefully I can find a stock upper triple for a reasonable sum.

Mike

[corey]

if you're bottom caliper bolts were closer in than your top bolts, it leads me to think that maybe your wheel spacers or axle are about 4 mm short of what they should be (two mm on each, seems to match your measurements right?)... if your axle lips and spacers aren't adding up to what the correct spacing should be, when you torque down your axle nut, you are bending the bottoms of the forks closer together a bit...

this is all theoretical.

i have an s2r800 with 999 forks and stock brakes.
5mm spacers on the calipers.
no spacers on rotors.
i used stock s2r800 axle for now, because the 999 axle was not the right fit.

what axle are you using?

also, i have a stock s2r800 top triple, silver. pm me to discuss.

[Raux]

woah.

ok so the triples are off.

makes more sense now.