Modern Vespa

Have to add more photos, but these were quick ones in parking lot. If the front tire is wearing on one side, off center; then this may help. Order of proceedure. 1 remove cover with philips screw. 2 remove 13mm nut. 3 slide off big washer, then thin spacer washer. 4 Pull knuckle joint apart. (dark photos) 5 another thin washer is on this side. 6 Idea is to move the washer to the OPPOSITE, of wearing side. So it pushes the tire top to offset wearing. Bottom line, move both thin washers to one side of knucle joint, and reassemble with big washer and nut, then cover and screw. Example: this tire was wearing on the outside, so both thin washers were moved to OPPOSITE inner side of joint. If tire was wearing on the inside, then both thin washers would go to OUTTER side of knuckle joint, with nut and big washer. UPDATED correction 9/24/2011 Thanks OAD & Fuzzy for the information, I only posted the details.


cover

nut under cover

first removed nut, big washer and thin washer.

nut off

tire wearing off center.

knuckle joint pulled apart

knuckle joint together

knuckle joint with outter big washer only.

knuckle joint with thin washers on inside.


Last edited by G03 on Sat Sep 24, 2011 3:37 am; edited 5 times in total

you put the inside thin washer to the outside so both thin washers are behind the nut correct?

Even though I was standing right there I missed seeing it live. Thanks for posting G03. Does anyone know if it is the same set up on the 250?

yes they use the same parts.

Corrected 9/24/2011

Last edited by G03 on Sat Sep 24, 2011 3:38 am; edited 1 time in total

better mesure with one of these



use 2 and the distance between them has to be 37.5cm both sides front and rear then you don't have any toe in or out

you got the wrong way of thinking on the washer placement. if the tire is worn on the inside remove the inner thin washer and place to the outside behind the nut and thick washer so bothe thin ones are on the outside, If the tire is worn on the outside remove the outside washer and put it on the inside next to the thin one and just leave the thick washer and nut outside.

Somebody should make this into a wiki item.

DISCLAIMER
This is a quick fix that may correct an uneven wear pattern on a front tire if the wear is heavy to one side of center. Other uneven wear such as cupping is a different problem / correction.It is a correction in the right direction but may not be the optimum amount. It is not a complete substitute to having a dealer use the alignment jig. If both front tires have a problem then there is no reference point and this method will be a crap shoot at best.

METHOD
Moving the washer changes the aim of the wheel known as toe in. This is the front to back angle not top to bottom.

If one front tire is worn excessively to one side of center it indicates that tire does not have proper toe in and the adjustment to the tie rod is required.

Where the tie rod connects to the steering there is a universal joint shown in the pictures. Where the universal joint bolts to the steering above the wheel it has a thin washer each side and to the outside just under the nut is a thicker washer.

The tire needs to be turned with the front moving towards the worn side, Moving a washer from the wornside to the good side in relation to tire. For example if the tire is worn on the side closest to the other front tire it needs to be turned closer to the other front tire. Removing a washer from the back of the connection so both are just under the thick washer and nut does this.

I am now personally aware of 4 MP3s with wear to the inside of a front tire so I am inclined to think this is the more common occurance. In this case move the washer from inside to outside.

I can also say that on my MP3 400 this has corrected the wear problem.

Mine was one of those that had this problem. Glad to see that it's posted now for everyone else's reference.

You added reflective tape to the side of the control arms, didn't you, G03?

Reflective tape in a couple areas, never to safe with no lights on!

You guys have to use a knuckle buster or pickle fork to get the joint apart?

Don't actually take the u-joint apart. It has a threaded piece on each end for attachments to the wheel steering tube and tie rod. Only the end connected to the steering tube needs to be taken apart as the washers are either side of the attachment. Once the nut and outer washers are removed just pull on the wheel to turn it and the attachment point comes off the u-joint threads exposing the washer on the back.

One other interesting observation of the problem. I have personally seen the excessive wear on 3 MP3s. All were wear on the inside of the right front tire and I think the 4th mentioned may have been as well. (Correct OAD?) If 4 for 4 it is a strong statistical indication that the problem is much more likely on that wheel for some reason?

Count that 5 and 6.
I´ve had it twice. First time I had to change the tie rod(Bent more than 1cm), this time its not that much, can probably fix it with some washers.
Both times, right wheel inside wear.

One thing I´ve noticed, if I do a hard right hand turn and hit some bumps/potholes, it bottoms out much faster than on left hand turns.....
Strange?????

Correct.

Here is the (toe in / toe out) procedure.
http://www.wotmeworry.org.uk/manuals/useful%20info/Steering%20Alignment%20&%20Shimming%20Procedure.pdf

The toe in toe out link no longer exist Does anybody have an updated link for the toe in toe out solution?

Strange i was told by my dealer that wear on the inside of the tires is normal due to the way the suspention is set up (camber). Honestly, i'm not seeing any noticeable camber that would point to such abnormal wear, but i'll guess we'll see how my new tires will fare.

On most rear wheel drive vehicles it is unusual to find front tyres which do wear evenly in normal road use. The actual wear is typically because of road camber so tends to be worse on the nearside tyre. i.e. left hand wheel in the UK, right hand wheel in the US. Adjusting the toe-in as described may well reduce the wear and the MP3 cannot directly be compared to car suspension because much smaller angles of turn are involved for any given corner radius. Increasing the amount of toe-in increases the self centering force generated by the two wheels opposing one another. Setting the wheels with toe-out would make them unstable and the scooter could act like a shopping trolley although castor angle is the bigger factor in this. If you don't believe me try reversing a car at high speed, preferably in a field, but keep a tight grip on the steering wheel or you will end up in a ditch.

Great anology on the reverse theory!

Mike

Heh.

Road camber has eff-all to do with tyre wear on motorcycles - or cars - or MP3s! Tyre wear occurs only on acceleration. That means positive or negative acceleration, from foot to the floor, braking or cornering.

Duff camber or toe-in is the usual culprit on cars (and MP3s), (occasionally caster is the culprit) - on a 2-wheeled motorcycle it's about vehicle (not road) camber only - how the wheel is centered vertically wrt the frame and main body mass.

Someone who normally rides with their bum slightly to one side could cause uneven side-to-side tyre wear on a motorcycle.

Road camber (which is normally minute, and anyway m/c riders tend to ride nearer the centre of the road) is a total red herring. Far more wear occurs on the sides of the tyre each time you take any sort of curve in the road.

With greatest respect we will have to agree to disagree on this. There are far too many variables at play to be dogmatic.
Tyre construction - MP3 uses scooter tyres which are not design for MP3 front wheels.
Riding style (lean angles, cornering speed, braking technique etc.).
Road condition and type for riders typical journeys.
Laden weight.
Tyre pressure.
Design compromises and manufacturing variations in all of the geometric factors you list.

I don't think uneven tyre wear is something to get too concerned about unless it means changing front tyres at a ridiculously low mileage. Especially when a hard ridden MP3 will go through rear tyres in 3 to 4 thousand miles.

Jim is correct in his answer above.
Off center tire wear is a cause of a problem in the motorcycle or scooter.
You can't ride enough on the sides of tires to cause that much wear before the centers are worn out.

Actually that's not true for the dual-compound City Grips - I've just had to change a couple of GTS front tyres that had loads of tread left but were nearly worn to the cords on both sides. We had done loads of twisties.
They had a very triangular profile - I wish I'd taken pictures. They also caused tons of the dreaded GTS wobble - which vanished with the new rubber.

Maybe they were under inflated ?
I adjust my air pressure to change the wear patterns, and that seems to work.

Keith,
Marietta, GA

Actually they were inflated to a couple of PSI over the recommended pressure - both of us prefer the ride like that.

over inflation is just as bad as under inflation.