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Standard front disc brake problem

Technical help for Series one, two and three Lambrettas. Models include the Li, Li Special, TV, SX, GP, Serveta and API/SIL models

Standard front disc brake problem

Postby superhooper » Sun Sep 20, 2020 2:09 pm

Hi peeps, on inspection i noticed the tyre [ scootsmart] fitted to the front rim/hub was worn flat on one side but ok on the other. Spinning the wheel there is distinct wobble and it's not running true. Took rim/tyre off and tried another quality rim [stainless bgm one] and tyre , that isn't running true either. Could it be the actual hub that's running out of true? To my eye it spins true with wheel off. Could it be a bent spindle Hub? had a complete rebuild about 3-5 thousand miles ago with quality parts. Any help would be greatly appreciated!

Thanks, Super
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Re: Standard front disc brake problem

Postby MickYork » Sun Sep 20, 2020 5:42 pm

Check the fork links are level.
If a spring on one side was harder/softer than the other, this would cause the wheel to tilt........just an idea :)
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Re: Standard front disc brake problem

Postby gp200ts1 » Sun Sep 20, 2020 7:08 pm

Don’t trust BGM rims either.
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Re: Standard front disc brake problem

Postby Storkfoot » Sun Sep 20, 2020 8:45 pm

As above, could well be the fork links.

Get someone to stand in front of the scooter as you take it off it’s stand and then rock it back and forth putting the front brake on. When I had this same issue, I could see that my front wheel, which looked central, went off to one side when the brake was applied.

When I took it all apart and put the links side by side on a flat surface, I could see they were out of plane.
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Re: Standard front disc brake problem

Postby Warkton Tornado No.1 » Sun Sep 20, 2020 11:37 pm

I agree that fork links can vary side to side, but mostly you may see that on the links on varying rebound rubbers.

Nevertheless, that in itself won't cause a wheel to run 'out of true', only not in line with the forks/machine. If you have a wobble, it can only be down to the hub &/or rims. Nor can it be due to a "bent axle" as that is stationary.

I would take the whole wheel out & clamp one end of the axle in a substantial soft jaw vice & spin it. You'll be quicker than trying to assess the cause any other way IMO
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Re: Standard front disc brake problem

Postby superhooper » Mon Sep 21, 2020 7:18 pm

Thanks for you advice peeps, i'll post any results when i have time for further investigation.

Regards Super
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Re: Standard front disc brake problem

Postby coaster » Wed Sep 23, 2020 9:02 am

superhooper wrote:Thanks for you advice peeps, i'll post any results when i have time for further investigation.

Regards Super


Dont rely on your eyes only Roy, hold a straight edge with one end touching the rim or hub and the other braced against the fork then spin the wheel to check runout, should also see any ovality too.
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Re: Standard front disc brake problem

Postby superhooper » Wed Sep 23, 2020 7:18 pm

Thanks Colin!
Super
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Re: Standard front disc brake problem

Postby superhooper » Sun Sep 27, 2020 1:17 pm

Hi, had time today to investigate wheel/hub. Here's what i found - removed tyre from rim, laid rim on a flat machine bed and both halves were flat within a very very minute amount if anything. Cramped bare hub in vice and spun the actuator side. there was a slight rock as expected due to not being held in links but it seemed to spin fairly parallel with other half, maybe not 100% but not far off. Visually checked links for parallel from side of scooter, they looked fine. Measured from back of fork to spindle recess in links and they are within 1mm of each other. Refitted hub & rim [no tyre] & theres a distinct wobble on turning wheel. The hub sits central in forks. I guess it must be the hub [ which i bought & stupidly restored without checking it ran true] From my analysis would anyone agree with my thoughts?

Cheers peeps, Super
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Re: Standard front disc brake problem

Postby Warkton Tornado No.1 » Sun Sep 27, 2020 1:44 pm

Thanks for the feedback.

If I understand correctly, the spindle must also no longer be a suspect.

That leaves the brake hub &/or the bearings fitted that results in the "wobble"

(Automatically, my understanding of a wobble is 'side to side' but that doesn't seem likely from your last post)

If it is running eccentrically, I can understand there is an issue, but @ least if you qualify that, "we" can suggest remedies.

(Sorry to appear so pedantic, but I'm hoping to glean the precise problem in an attempt to help with any remedy ;) )
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Re: Standard front disc brake problem

Postby superhooper » Sun Sep 27, 2020 2:25 pm

Hi, to be more precise. The hub is fixed firmly in links with no bearing wobble but when hub/rim are spun it does not run true. ie looking at a fixed point it looks like the rim is not flat.
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Re: Standard front disc brake problem

Postby MickYork » Sun Sep 27, 2020 3:19 pm

have you got another hub to try ? seems the quickest solution. If not, whereabouts are you ? someone might be generous and loan one to confirm or eliminate the hub.
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Re: Standard front disc brake problem

Postby superhooper » Sun Sep 27, 2020 5:23 pm

MickYork wrote:have you got another hub to try ? seems the quickest solution. If not, whereabouts are you ? someone might be generous and loan one to confirm or eliminate the hub.

Not got a spare hub but will ask around. i live on the essex/suffolk border on the off chance anyone local has one i can borrow

Cheers Super
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Re: Standard front disc brake problem

Postby superhooper » Sat Oct 03, 2020 5:01 pm

Hello again, tried another hub [drum] in forks with a rim & it seems to run a lot truer so i'm assuming my hub is the cause. Took spindle out & rolled it along a machine bed and it doesn't seem 100% flat. There is a dull spot about 1/5th of the circumference & about 3/4 of the length. could this be the problem or not. As usual any feed back is greatly appreciated.
I guess the easiest option is to try another spindle, any recommendations?

Cheers Super
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Re: Standard front disc brake problem

Postby Knowledge » Sat Oct 03, 2020 8:16 pm

Roy,

I have another spindle here if you want to try it.

Martin
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