wobble,wobble. Smaller tire

[ALdad]

Hi guys, Took everbodys advise and put a new 160/60 diablo on my 2000 sport on a 4.5 rim. previous owner had a 180/55 .The bike feels great turning in and at speed in a straight 90mph. The Question is, on my way home tonight going through my favorite uphill left sweeper at about 60 mph I chopped off gas to slow for a red light and got a significent wobble. I have run this corner for the past year on this bike, and three previous years on my monster, and have never experienced this before. I am sure I have come off the gas at the same speed in the same place before. I am running 39lbs rear,37frt. Maybe I have not had this exact scenario before but with the light at the top I would think I would have. Any Ideas? Maybe I just need to learn how to ride a Guzzi and not chop the throttle mid-corner YA-Think!!

[rocker59]

Seems like a little too much air pressure to me.

 

I'd drop two or three psi both front and rear, if it were me...

 

On my Nero Corsa, I run 33f/36r most of the time with the Z6 Metzelers.

 

No problems with wobble...

 

The Guzzi owners' manual I received with my Nero Corsa recommends 2,2bar front / 2,4bar rear for a solo rider. That equates to 32psi front / 35psi rear...

 

For two-up, 2,3bar front / 2,5bar rear. That's about 33psi front / 36psi rear...

 

FWIW, I've gone from the OEM 180/55-17 to a narrower 170/60-17 rear tire and have been pleased with the improved steering response...

[Guest ratchethack]

Wot Rocker said. Get spring rates, sags and preloads correct, keep forward on the seat in turns, 34F/37R, dial up some steering damper. Chopping throttle mid-corner heeled hard over -- not so good an idea, (ever). . .

[FuelCooler]

Setting the spring rates and sags as stated above will solve many ills, because it helps maintain your front to rear weight bias (and these V11s the bias is to the rear, which is not typical for a sporting bike).

A 180/55 is taller than a 160/60. When you took that wildly pinched 180 tire off your 4.5 rim and replaced it with the correct 160, you lost rear ride height, effectively taking weight off the front. And assuming your are riding on stock springs, when you chopped the throttle you suddenly went from loading the soft rear spring to (over)loading very soft front springs which upset the bike enough to wobble. I believe your taller (incorrect 180 tire) was loading the front, somewhat masking poor spring rates and sags.

Are the tops of your fork tubes flush with the upper tripple clamp? Pulling them through 8-10mm helps load the front as well. But you still probably need springs. If you do a search for 'springs' or 'fork springs' this board has many good recommendations on springs and sags. Or just call Ratchethack and save yourself some time

Have fun!

Steve

[ALdad]

Setting the spring rates and sags as stated above will solve many ills, because it helps maintain your front to rear weight bias (and these V11s the bias is to the rear, which is not typical for a sporting bike).

A 180/55 is taller than a 160/60. When you took that wildly pinched 180 tire off your 4.5 rim and replaced it with the correct 160, you lost rear ride height, effectively taking weight off the front. And assuming your are riding on stock springs, when you chopped the throttle you suddenly went from loading the soft rear spring to (over)loading very soft front springs which upset the bike enough to wobble. I believe your taller (incorrect 180 tire) was loading the front, somewhat masking poor spring rates and sags.

Are the tops of your fork tubes flush with the upper tripple clamp? Pulling them through 8-10mm helps load the front as well. But you still probably need springs. If you do a search for 'springs' or 'fork springs' this board has many good recommendations on springs and sags. Or just call Ratchethack and save yourself some time

Have fun!

Steve

Yes my fork tubes are flush . I had thought about lowering them . I also have standard bars,triple clamp drilled and risers, putting even more weight to the rear.This setup prior to the tire change took enough weight off the front to give my 210lb on the bike proper sag in the front. the fork felt OK. I am in the process of trying to figure out what rear spring to go to to get correct sag without a bunch of preload.I have the stock shock with the blue rebound adj. and seporate comp. cylnd .Anybody have any sugjestions what spring setup and where to get them? Thanx!!

[FuelCooler]

Yes my fork tubes are flush . I had thought about lowering them . I also have standard bars,triple clamp drilled and risers, putting even more weight to the rear.This setup prior to the tire change took enough weight off the front to give my 210lb on the bike proper sag in the front. the fork felt OK. I am in the process of trying to figure out what rear spring to go to to get correct sag without a bunch of preload.I have the stock shock with the blue rebound adj. and seporate comp. cylnd .Anybody have any sugjestions what spring setup and where to get them? Thanx!!

 

Hi ALdad,

Lowering the front should help (and it's free!) but I suspect your springs are too soft. Do a search on 'laden sag' or 'unladen sag' and compare those numbers to what your getting.

Our bikes have the shortest wheelbase and the steepest fork rake out of all the V11 spine frames so weight transfer issues affect us more. When a bike has soft springing there is a greater variation in the rake and trail during rapid transitions from throttle on to throttle off i.e. going from rear 'squat' - front 'light' to rear 'light' - front 'dive'. Getting either front or rear spring closer to ideal will help, but in my opinion (as well as others on this forum) getting the front end right is a better bang for your buck.......to start. I am 185 ready to ride and I have Wilbers progressives up front, which are good for me. HyperPro makes some progressives which could be alright, but if I were to do it again I would try 1.0 to 1.1 kg/mm straight wounds. Again, there is alot of good info on this board regarding this subject if you do a search. And if you happen to find another solution that doesn't match what is posted here but makes you happy......enjoy it and ride! And let us know, I haven't quite learned everything yet.

 

Cheers,

Steve