Ducati Sporting Club UK > Model Specific - Discussion, Technical Problems and Help > 998 / 996 / 916 / 748 > tyre rubbing exhaust

[Bungi]

my rear tyre is rubbing on the exhaust.

standard 94 link chain
14t front and 38 rear
50mm pipes alll the way

the swing arm i believe is off a 748r 1999 the engine is a 998s

i have checked all the pipes are fully home in the sleeves but the tyre rubs on the pipe that comes from the rear cylinder, temp solution is ave chabged rear sprocket to a 37t and this moves it away just enough to get away with it with a 180 rear tyre, but when i went to fit a spare wheel on track day yeasterday which had a 190 fitted it wouldnt even spin coz is had so much contact.

the bracket on the engine block to the bottom of the midle pipe is positioned around 8pm. is this about right my 916 is nearer 7pm? but has differant pipes

q are any of the standard swing arms differant ??

Q anyone have any similar problems, suggestions as to the cause?

[Bungi]

by the way the hub IS in the lower part of the swing arm

[MARTIN H]

Had exactly the same myself. I had fitted a 180 rear and also some track day bodywork. I noticed the rear of the bellypan was very close to the rear tyre compared to the identical kit on Lilys bike. We messed around with the bodywork until we got a decent clearance. On a run out however I took a look at that are of the bike to check if the tyre had contacted the bellypan at all (it had not) but noticed that the section of exhaust you mention was highly polished from the tyre rubbing it. At standstill there was a good few mm clearance but at speed the radius of the tyre increases and hence the contact.

A 180 tyre has actually a slightly greater radius than a 190 (think its about 4mm or so more) so a new 190 should give greater clearance than a new 180.

Like yours my eccentric was in the correct range of adjustment so I was a little baffled. I ended up losing patience with it and ordering a 96 link chain to lengthen the wheelbase a little. It actually lengthened it quite a lot and a then couldnt get my chain tight enough! Not a major problem as I wanted to lower the gearing anyway so I went up 3 teeth on the rear (instead of fitting the 14t sprocket I already had) The end result was the tyre was just a little further back than it was when I started. Worked out pretty expensive with new Tsubaki chain and Renthal rear sprocket and carrier. Promptly did a track day at Oulton that stretched the new chain enough to increase clearance a little more after adjustment. Happy with it now.

[MARTIN H]

My original post.

http://www.ducatisportingclub.com/sh...ad.php?t=31650

[Bungi]

the 190 tyre is definatley tighter and less clearance than the 180?

althought they are fitted to differant rims the 180 to a 3 spoke and the 190 to a five spoke alloy mach.

[MARTIN H]

I think if perhaps the 190 is fitted to a 5.5 rim instead of a 6 it is more pinched for want of a better word and probably then a larger diameter/radius.

A 180/55 is about 99 mm tall and a 190/50 is about 95mm tall meaning the 190 (on the correct rim) should be about 4mm further from the exhaust?

[Bungi]

UNDERSTOOD HOWEVER
THE 190 WAS FITTED AS STD TO THE 996R ON THIS RIM? AND DIDNT RUB THE EXHAUST, SO IS THIS SOME kinda Phenomenon

[Bungi]

so what ive found out is...

that tyres have differing profiles(or should i say shapes )dispite what is written on the side of them,
the dunlop 209s that i was running have a profile which runs closer than say a supercorsa.
come to think of it i had a prob b4 when running a 208 and it started rubbing the rear hugger, just the tyre wasnt on there long enough to cause an issue

Martin H did you cahnge tyres when you discovered this

[MARTIN H]

No, I stuck with Diablos both 180 and 190. I do recall noticing in the past that certain manafacturers tyres were wider than others for any given width. I think Dunlops were always wider (or appeared so) than others. If the tyre is slightly wider than another make it makes sense that if its profile whether it be a 50 or 55 is accurate then the rolling radius of the tyre will be larger and so nearer to the exhaust.

I spoke to a few people when I had trouble with mine and nobody has heard of this problem before. JPM reckons I must have a short wheelbase 996R!

[Bungi]

well i cant really make much sense of it, as thinking about it the bostrum rep 998s came with dunlop 208s or were they 207's anyhow the problem exists.

potential soloution of a 16.5 rear rim being considered