Sprung hub and tyre

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Notsospeedy
Posts: 136
Joined: Sun May 17, 2009 8:04 pm
Location: Cheshire

Sprung hub and tyre

Unread post by Notsospeedy » Fri Sep 26, 2014 5:03 pm

Whilst I'm struggling with the silencers/ kick start/ rear stand on my pre-unit Speed Twin (either the stand hits the inside of the silencer or the kick start hits the outside), I noticed the tyre on the back wheel isn't in the centre of the rear stays.
It's well over to one side, surely this can't be right?
I'd have thought the rim and tyre would be central but it's not. The final drive chain is in a nice straight line but the rim and tyre are way over to the offside. They're central to the sprung hub itself and both sets of spokes look to be the same. The parts book only gives one number for all 40 spokes so that seems correct.

If I lay a plank along both edges, a la MOT, the wheels are far from in line.

Image
Any suggestions what's wrong? It surely can't be supposed to be offset...can it?


Malcolm

DerryUK
Posts: 107
Joined: Fri Dec 03, 2010 11:24 pm

Re: Sprung hub and tyre

Unread post by DerryUK » Fri Sep 26, 2014 5:24 pm

You need to compare the rear wheel with the front. Have you got a long straight edge, I use a piece of aluminium angle from B&Q.
The front wheel should be in the centre of the frame by default.

Maybe your rear wheel was from a different bike? Hence the offset is wrong.

Derry.

Notsospeedy
Posts: 136
Joined: Sun May 17, 2009 8:04 pm
Location: Cheshire

Re: Sprung hub and tyre

Unread post by Notsospeedy » Fri Sep 26, 2014 8:32 pm

The front wheel is in the centre of the frame, the rear quite obviously not!

The only bikes that had sprung hub MK2 were Triumph rigid frames and only for about 4 years so whichever model it came from originally it should fit as they all used the same frame effectively.

What gets me is that many years ago I had the actual mechanism refurbed by the late great Hughie Hancox and he got the wheel re-built as well at the same time, so it should be right.
I'm just having difficulty believing that it was supposed to be offset.

Anyone out there got a MK2 sprung hub fitted to compare?


Malcolm

Triton Thrasher
Posts: 774
Joined: Wed Feb 18, 2009 12:51 pm

Re: Sprung hub and tyre

Unread post by Triton Thrasher » Fri Sep 26, 2014 9:02 pm

Looks like the rear wheel is spoked with the wrong offset.

You can ride a bike with wheels out of line. Taking another look, I think my Indian Enfield might have been farther out than that, from new.

Willpower
Posts: 679
Joined: Sat Feb 21, 2009 2:56 pm
Location: St. Annes on Sea

Re: Sprung hub and tyre

Unread post by Willpower » Sat Sep 27, 2014 11:29 am

The gap between the rear sprocket and the hub looks too big. Any chance of a 'angled' shot from the rear looking at the sprocket and hub?

Notsospeedy
Posts: 136
Joined: Sun May 17, 2009 8:04 pm
Location: Cheshire

Re: Sprung hub and tyre

Unread post by Notsospeedy » Sat Sep 27, 2014 2:46 pm

Here you are
Image

The sprocket and brake hub are a single piece and they bolt directly onto the large hub housing. there aren't any spacers or washers etc.

Malcolm

Willpower
Posts: 679
Joined: Sat Feb 21, 2009 2:56 pm
Location: St. Annes on Sea

Re: Sprung hub and tyre

Unread post by Willpower » Mon Sep 29, 2014 7:25 pm

If the final drive chain aligns nicely with g'box and rear wheel sprocket, then I'd say TT (and yourself) have already identified the problem with rim/hub offset.

Pete R
Posts: 81
Joined: Sat Jul 07, 2012 8:04 am

Re: Sprung hub and tyre

Unread post by Pete R » Sun Oct 05, 2014 8:22 pm

The centreline of the gearbox sprocket is normally 3" from frame centre.
See if the centreline of the rear sprocket is 3" from the rim centre.

Notsospeedy
Posts: 136
Joined: Sun May 17, 2009 8:04 pm
Location: Cheshire

Re: Sprung hub and tyre

Unread post by Notsospeedy » Sun Oct 05, 2014 9:32 pm

Thanks for those figures, that's just the sort of thing I've been looking for. It also confirms I've got the gearbox set up properly.

I took the wheel out and found the dust covers/small springs that sit on the axle on the chain side weren't seated properly and that helped a little.
Pieces of string, laser lines, straight edges,rulers all suggest the rim is over to the off side and your figure confirms it.
It's not a huge amount, about 3/16" but enough to look horrible.
Hoping it will just be a case of getting the spokes slackened off and then trued with the correct offset. Wheelbuilding is one thing I've never tried and whilst I know a lot of people do, I'm not sure I want this to be my first attempt.

Phew, feeling I'm getting somewhere.

Thanks all.

Malcolm

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