Front disc disc fouls calliper

I have a 2nd hand 2003 Monster 620. It had a single front disc & that needed replacing. On stripping the wheel/calliper assembly I noticed the disc is not running central to the calliper and it had worn a step in the inside edge of the calliper. The pads were also worn grossly different on each side. The disc is running 4mm approx inboard of the calliper centre line. Thinking the disc may be wrong I ordered a new Ducati disc, but it is the same (Ducati number 492.4.024.1A – common on many Ducati) . The disc has an offset of 9.75mm (outer disc face to inner carrier face) The disc to fork/calliper distance is controlled by the axle spacer (30mm long) and potentially the location of the bearings in the wheel (which look OK) and the cast fork end. The calliper is a direct fit onto lugs on the fork cast end.
The only other possible issue is the calliper - it looks correct - gold Brembo 4 pot with a casting number 20 6715 00, 2002. The wheel is running dead central in the forks.
Has anyone any ideas what might be causing the 4mm approx disc/calliper offset?

[Nickj]

The disk itself is way more common than you'd imagine and the same unit is used from ducatis through to yams.
The disk has worn unevenly, the pads are uneven. Whats happened is that the pistons on one side aren't moving.
Even if the things a little out of kilter the pistons should accommodate a small offset.
It's quite possible that you either need to get a new / replacement caliper unit or a set of seals and pistons. These are made, they're standard brembo parts BUT ducati don't market them under their name after some twat screwed up a rebuild in the states then sued.
There've been a few seal packs on ebay or Sean at http://www.duetorrimoto.co.uk will get you a set if you have trouble sourcing them.

[Dirty]

Welcome to the forum

[Flip]

Exactly what Nick says!!

I know I've seen seal kits for them somewhere else too- I'll have another look and post it up.

One thing though- I thought all 620's were a twin front disc set up??

[Funkatronic]

most odd 492.4.024.1A looks like right part (320mm disc, six hole pattern,10mm offset) as is found on most old shape monsters and many many other ducatis (and lots of aprillia & ktm)

620 came with 2 different brake setups both twin disc afaik so yours is non standard if its a single disc setup

earlier ones had 320mm discs with 10mm offset with usually twin gold callipers

later ones had 300mm discs with no offset u with black twin 2 pot callipers

could there be a spacer beteween the rotor and wheel?

as your brake setup is non standard its also possible your caliper has been machined down to fit 15mm offset rotors, will try take a pic of one of mine so you can compare

if you now have a pair of discs, i have a set of brembo 4 pot callipers (black in colour but 4 pots identical to the gold ones ) with lines with good pads from an s2r 1000 that should bolt straight onto your bike
send me a pm if your interested

otherwise, i also have a worn pair of 15mm offset rotors i could lend to test if you are able to get to north london

[chris.p]

Originally Posted by Funkatronic

most odd 492.4.024.1A looks like right part (320mm disc, six hole pattern,10mm offset) as is found on most old shape monsters and many many other ducatis (and lots of aprillia & ktm)

620 came with 2 different brake setups both twin disc afaik so yours is non standard if its a single disc setup

earlier ones had 320mm discs with 10mm offset with usually twin gold callipers

later ones had 300mm discs with no offset u with black twin 2 pot callipers

could there be a spacer beteween the rotor and wheel?

as your brake setup is non standard its also possible your caliper has been machined down to fit 15mm offset rotors, will try take a pic of one of mine so you can compare

if you now have a pair of discs, i have a set of brembo 4 pot callipers (black in colour but 4 pots identical to the gold ones ) with lines with good pads from an s2r 1000 that should bolt straight onto your bike
send me a pm if your interested

otherwise, i also have a worn pair of 15mm offset rotors i could lend to test if you are able to get to north london

Might be wrong, but the discs for the 620 and most Ducati's are classed as 5mm offset, with the Ohlin shod Ducati's being classed as 10mm offset, it is down to the way they are measured.

[slob]

620 Dark models were all single front disk as stock AFAIK

Thanks for all the input! The pistons in the calliper are not seized, and this is an assembly condition before the pads are put in. The disc has actually worn evenly, but has obviously been running pushed off centre. It is very slack laterally on the rivets to the carrier. The Calliper has no signs of any machining or modification.
I had considered the forks were incorrect for the bike, but the Ducati dealer did identify 'low cost' single disc variants - the right hand fork has the lug for the calliper, but has a plastic cover fitted over it and that is what I have got.
The inside face of the lugs on both sides look the same, so I do not think that has been modified.
As suggested above I think I need some parts to try or at least a Monster locally I could compare with - anyone near Billericay in Essex?

[slob]

The plastic cover on the lugs suggests yours is indeed a 'dark', I assume it's either satin black or silver?

I'm in East London if that helps. (EDIT: although I've just realised none of my three Monsters has a stock front brake setup but I do have quite a collection of standard brake parts)

Lateral movement of the disc on the carrier probably isn't an issue, rather a benefit.
Excessive radial movement would be unhealthy.

[Funkatronic]

620 Dark models were all single front disk as stock AFAIK

i stand corrected

Might be wrong, but the discs for the 620 and most Ducati's are classed as 5mm offset, with the Ohlin shod Ducati's being classed as 10mm offset, it is down to the way they are measured.

10mm standard and 15mm for OEM ohlins and radials (afaik)
road and track ohlins use 10mm go figure

i was always told to include the thickness of the disc in the offset

[Dukedesmo]

Originally Posted by Funkatronic

i stand corrected



10mm standard and 15mm for OEM ohlins and radials (afaik)
road and track ohlins use 10mm go figure

i was always told to include the thickness of the disc in the offset

Indeed, measured as per the 'F' dimension here;

[slob]

I've got a set of radial R&T Ohlins that require 15mm offset discs (you sold me the 998R discs Ali)

[utopia]

I'm not disputing that it is the accepted method of measuring offset (I don't know either way) but it does strike me as odd that the measurement should include disc thickness.
In that case, two completely flat discs of thickness 5mm and 10mm, would be classed as having an offset of 5mm and 10mm respectively, even though both are completely flat.
From a purely engineering point of view it would seem more sensible to measure from the inboard face of the disc, or better still from the centreline.
I guess the dimension measured in the accepted way could be called MAXIMUM offset.

Anyway, Nick and Flip are usually reliable sources of info but in this case I can't see how your problem can be caused by sticking pistons pistons if the disc is able to foul the caliper body itself.

Strange that the new disc has the same problem.
Sounds like maybe some other components have been changed previously.
Or even that your new disc has been supplied incorrectly.

[Mr Gazza]

Err....I'm not really qualifed to comment here but, is it the right front wheel???

...Sorry should have said the correct front wheel.

[Funkatronic]

gotta be some component thats not right, only thing left is wheel or the spacer but again they are fairly interchangeable


apologies rob - slightly off topic but to be clear

road and track ohlins with standard 65mm spaced axial caliper mounts use 10mm offset

Ducati OEM ohlins (ie come as standard on bike from factory) with standard 65mm spaced axial caliper mounts (eg 748r,996R,998r, GT1000 paul smart ) use 15mm offset

afaik (and my knowledge has been shown to be limited!!) , All radials calliper mounts on ducati bikes (ohlins, showa etc) use 15mm offset as otherwise its impossible to remove the callipers without fouling the wheel