Front end shimmy

[Rufus]

Hello,
I just fitted new tyres but every now and then I get a slight front end shimmy at the handle bars.
It does it at different speeds and sometimes not at all or not noticeably.
One of the pistons on the ride hand side calliper sometimes drags a bit, do you think this could be the cause?.
I checked the fork and axle alignment, wheel bearings are ok,
Could it be the tyre. I balanced it and it was perfect BUT it took 50g. with I think is a lot.

[Tug]

If as you say it happens at different speeds and sometimes not at all i would be looking at a tyre fault, the tyreis not a constant as temperature / pressure can be a factor to any defect.

[gsxbarmy]

When you fitted the tyre - did you fit it with the painted spot on the sidewall next to the valve? If not this could be why you needed 50g (which as you say is quite a bit). If you didn't, it doesn't matter, but the spot is there to align next to the valve to minimize the amount of weight used in balancing.

Regards the shimmying - with the front wheel off the ground, have you spun the wheel - is it straight on the rim as you look at it head on?

[Timothy Spencer]

...or is the front tyre just tracking road seams and white lines occasionally?

[Rufus]

Hi, thanks for the suggestions.
I checked the tyre and it has a yellow blob and a white triangle, I guess the white triangle is the weight bias mark and that's almost opposite the valve. The yellow blob is 90 degrees away from the valve.
I didn't fit the tyres, although I wish I had now,cos it took 4 days to get them half done 
I took them to the garage, had to go and pick them up again, take the tyres off the rims for them. Took them back, the tyres were fitted. Picked them up and then had to balance them myself. - This is one of the better places here !

No obvious defects that I can see, both tyres hold air pressure really well.
It could be tracking bad road features, the roads are shite here.

Anyhoo, I'm riding around Sicily later this week so hopefully it won't become a problem. At the end of the day it might just be me being paranoid. 

[Kiwifruit]

Hi Rufus. Just out of curiosity what brand of tyres did you fit ?

[Rufus]

Hi, Dunlop SportMax Q2s
Just got back from Sicily, mostly fine but the last day the front end was doing it a lot.

[grog]

any suspension shops in Malta or nearby. something wrong somewhere mate.

[Rufus]

Hi Grog
No-one on this island that is capable or that I would trust, so I'll have to take it apart this weekend and see what i can find.

Back to the Tyre alignment, which would you say is the marker for the tyre heavy spot - white triangle or yellow blob?

[Rufus]

According to Google the Yellow dot is the light spot, it's 90 degrees off from the valve on mine. However some say as long as it's balanced it shouldn't make much difference.
Can't think what else it could be, was fine before the new tyre.

[Blubber]

It's the coloured dot on the side wall that needs to be aligned with the shrader valve.

This only to save on balancing weights.

Since its already balanced,  I doubt relocating the tire on the rim wil cure your problem.

Maybe the internal design of the tyre is different than the one before?

( causing a different feel / feedback?)

Had that on my car.

[Rufus]

Hello, an update
I took the front wheel off, it was still balanced perfectly.
Then I looked at the forks, the right hand fork was 2mm lower than the left.
Cleaned and unseized the compression adjuster, wound them right in and recounted the clicks out, there was 1 click difference.
Re-assembled and did a fork alignment thing where you undo everything below the top clamp/triple tree and bounce the bike.
After a few rides, it seems to have solved the problem, only a slight wobble when hard on the gas over 50mph.
The rest of the time it's ok or not noticeable, so one of the above fixed it. 

[grog]

shouldnt be any wobble, mine never has.

[Rufus]

I found a quote from a Dunlop tyre guru that some bikes will have a slight wobble at certain stages, i.e. when the tyre is cold or on deceleration and so on. They don't engineer this out because they are concerned with high speed stability. 
Should have kept the reference, maybe I'll find it again.
It could explain why I never noticed it with the previous tyre or it could be bs