Alignment

[Wack]

I've always been aware that my Italian GP rear wheel has never sat central to the rear end so I knocked up a wheel alignment jig which clamps to the rear tyre and follows through to the front wheel. I've found that the rear wheel is about 10mm to the nearside of the front wheel so even though the scoot handles fine at all speeds ,it isn't right . The frame loop was welded on a friday as it's about 5 mm over on the rear support and the panel spring arms don't sit central to the tyre but that's not the real problem.The engine mounts look good and the offset cones are both the same with the slot vertical and the front wheel is parallel to the guide so the frame isn't bent mid section.I checked a mates GP and his wheels were perfectly in line and have the same distance from the engine stand lug to the rim inner as his.Any ideas?

[Knowledge]

This a complicated one Wack, because after 50 years, a frame can have many defects, all of which add up to a 10mm defection. My thoughts are that with a small bit of wear in the engine mounts and the front fork links (rebound rubbers) you could probably account for 5mm. With a bit of twist in the frame or fork legs, you could have another 5mm of deflection.

I guess the intriguing thing is the fact that rides OK. Mind you, my mate Dr Phil thought his scooter rode OK, until the very defective bottom steering race was repaired, and the scooter is now transformed. You might find that your scooter is even better once you have eliminated the 10mm.

[Wack]

Thanks Martin,the steering is perfect and uses the Innovations outboard springs so no problem with the links and vertical alignment.I replaced the rear hub(UNI) and fitted SIP tubeless rims and noticed things didn't look quite central from the rear so re fitted the old SIL hub but was just the same.I'm building a new motor at the moment so will see how it sits when fitted but as in original post the wheels are parallel to each other just the rear is stepped over but I'm sure it didn't used to be like it .

[Warkton Tornado No.1]

It sounds like your frame is Indian, which might account for the inaccuracy. However, presumably you don't want to strip it to get re-jigged, in which case you could play about with gaining a bit here & there to re-align, if you feel you must.

However, one thought that struck me would be to correct the frame where it needs it: modify the existing engine mount tube by cutting back on the offending side ensuring the taper bore is also cut deeper. Then shim up the other side with a special spacer.

Just a suggestion.....



I've just re-read your post after submitting this. The problem isn't @ your layshaft/hub interface, is it? The cone is not the wrong taper for the hub, is it? Sorry if that question is a silly one, but I've known it happen.

[Wack]

The frame is definitely Italian Mark and the cone is what came with the UNI hub. It would be hard to alter the frame mounts as the flywheel side is flush with the main tube.

[Warkton Tornado No.1]

Sorry Wack. I'm not quite getting it, am I?

I thought the tube was misplaced to the nearside & could be cut back to be flush. I shouldn't be allowed out on my own....

If that was the solution (which it sounds now, not to be the case) I agree that it would be hard to carry out but still do-able. Then, the next obstacle would be the engine lug interfering with the frame main tube.

I have an Italian GP frame in the attic & just looked. It is, more or less, flush on the nearside. Yours could be a twist in the mount tube to the frame as it would mean the same. The wheels would still end up parallel but gapped by 10 mm. The only way to be certain is to check rear wheel direct to frame. I suppose spirit level the fork tube on a side (the best available datum) & level the frame via packers until it is vertical. Then spirit level each side of the rear rim initially to check how true they are to the fork tube. If in alignment, measure to the main tube. The distances should be equal.

I suppose a photo would be handy because, having got this far in asking, you must really want it sorting.

[dave81]

Sorry to come in late on this one Wack. Just curious as to how the scooter passed the mot.I have put my GP through two mots and both times I saw them put a straight edge from rear to front wheel or was my tester a bit fussier than some? Does the tyre not wear uneven?

[Wack]

I've owned this scoot for around 10 yrs now and I don't think it's been straight edged before. What Ive found today is that the offset cones are not a match.So I've fitted some standard ones which has bought the wheels in line with each other. The rear end is still not central to the tyre but with measuring it's obvious it wasn't welded true in the factory so that's a job for the future. This is how it was before changing the cones.

[Warkton Tornado No.1]

The cones were wrong, after all that. Swap left for right & you might fix the problem!

If your rear wheel is an alloy tubeless, it may be offset on the nearside. SIP's are as their drawing on their boxes shows.

I don't consider that a problem, especially if used in pairs. Is that what you are doing as I notice you don't have a standard front hub?

[Wack]

Yes SIP rims and narrower tyres now. It used to have a wide rim at one time and the rear end looked more central but a mates has the same SIP rims and tyres and his is central. Both have PM front hubs as well.

[carlos fandango]

Im not to sure i understand your problem, but why are you assuming its your rear wheel that out of line ?
I see you have what looks like a PM front disc , are you sure you have this centralised ?

[monument7]

Firstly I know I should have checked more thoroughly but here goes.
Bought a pair of silent blocks from a supplier I have had parts from in the past without problem and when fitting the inner of one of them actually pushed out of the outer shell which I complained about and they sent a replacement without argument. Built the rest up as I was waiting and noticed the rear wheel was out of alignment. Checked rear hub and cone were ok then noticed the silentblock seemed out of centre the same way the rear wheel was out. Feeling a bit relieved I got out the replacement from the supplier ( which I hadn't unpacked ) . More shite for the pile in the corner.

[Warkton Tornado No.1]

Way off track, but the photo made me smile. Not in a 'mocking' way....

Firstly the brass tap. I bet it's been 'ported' like virtually all of my old taps that......well, I've just kept them!

Secondly, though, the fully retarded '& then some' stator!

Jeez! We must be enthusiasts!

[monument7]

[Wack]

Has anyone got a good frame to compare this , pretty sure it's not welded central. If I run a straight edge along the seat arch to the steering column, there's 30 mm difference each side. The main tube looks true .

[Warkton Tornado No.1]

I've checked two of my Italian bare frames (GT & GP) & they are central compared to your frame which is obviously offset.

I took photos on my iPhone but upon connecting to my PC, they have decided to synch for the first time ever, after numerous previous attempts have failed. Currently 3647 of 7047 music files have transferred to the iPhone so there's a while to wait.

If I live long enough, I'll post my pictures, but unfortunately you already know that your suspicions are true. Your frame is in need of some accurate correction when you get the chance, although getting the wheels in line might not involve making all the changes @ once. Little consolation, I'd imagine.

In any case, can you assume the fork stem is as it should be as I reckon they are quite vulnerable to twisting out of line relative to the rest of the frame?

For long term peace of mind, you'd be best to get your frame jigged to standard specification.

[Wack]

PM sent

[Warkton Tornado No.1]

PM sent back in reply.

[Fast n Furious]

I think the moral of the story here is to confirm that the frame is straight and true before you spend any time or money putting it on the road.
It might cost you a couple of hundred to have it done by one of the noted professionals if you don't have the skills and facilities to do it yourself.
It will be the best money you will spend on a Lambretta because it will make your riding experience live up to expectation irrespective of what power your engine has.(The grim reaper hates me)
Worry about the engine mountings later cos, if yer frame ain't straight, you is urinatin' int't' wind.
Let's face it...... Unless you have owned that scoot since new, then you will have little evidence that it has never gone down the road sideways and horizontal at some point in the last 50 odd years! So..... assume it has. If those handlebar ends have ever bashed tarmac (and most have!) ( The low speed "offs" do most of the unseeen damage) then the frame tube under your feet is probably twisted ever so slightly enough to make a handling difference. (Its only circa 2mm thick and the leverage factor from the bashing is "enough" but your naked eye won't perceive this)
The various manuals out there seem transfixed on a non critical measurement from the top steering bearing area to some uncertain point around the toolbox. Unless the scoot has been in an absolute head-on crash, this measurement is unlikely to change and wouldn't have any significant negative affect on handling anyway unless "out" very severely.
Some machines were definitely "Friday afternoon bikes" and some Fridays in certain countries lasted for some time!
I have a 75 Jet, and the welding and geometry could only be described as absolutely shocking. It took me a couple of days to sort it, and now, the improvement bears the fruit from all the effort. (I do like to eat GTS Vespa's and then regurgitate.)......(This used to be my deceased brothers scoot, which no-one wanted to ride when we was kids, cos it was crap? Not anymore)
Can you take both hands off the bars at sixty, sit up like a Cheshire cat and be confident that you won't need to put them back on again until 20 or less? (Don't dare GTS owners with +5K on the clock to do this unless you dislike them intensely).
Think how much it will cost you to do this remedial work after you have spent shitloads of money on that lovely award winning paint job and how do expect your prize rev monster to handle at 90+MPH?........ OUCH.?
Think on lads n lasses and spend your hard earned where it really matters! THE FUNDAMENTALS.

[kennystag]

Well said FnF.
stag