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BSA 8" half width front hub offset please? #758312
12/06/18 2:43 am
12/06/18 2:43 am
Joined: Oct 2004
Posts: 120
Adelaide South Australia
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GROG Offline OP
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GROG  Offline OP
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Adelaide South Australia
Does anyone have or can measure the offset for the 8" half width wheel please?

It is to be used in a 1950s swingarm frame frame.

The wheel builder is questioning the offset figure I gave him..... and it's already taken him too many weeks (12) to do my job.

Before pulling the wheel apart I measured offset at 48.5mm from the drum face to the rim centre. ... but am now questioning myself.

I cannot readily go and get the hub back to put between forks to check since the bike is in a million bits with the forks being rebuilt and the yokes out for painting and I'm running out of time to get it all done for a race meeting I've entered.
Even if you measure from backing plate face to rim edge and give me the width of your rim I can work it out from there.
Ah, this is assuming your front wheel is central in your forks of course...haha!

I had a good look around online and found one dubious measurement that was close to mine and I searched this forum and found no figure... so please, any help would be much appreciated.
Cheers and Thanks,
Greg

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Re: BSA 8" half width front hub offset please? [Re: GROG] #758400
12/07/18 2:32 am
12/07/18 2:32 am
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Phil R Offline
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Hello Greg,
I remembered I still had a 19" WM2 8" SLS that I once had used on an A10. It was in my son's shed. Took a few pic's of the same in the hopes they'll help you out.
One caveat: when acquired, the A10 needed a front wheel. I sourced the rim and brake assy separately and asked a local wheel builder to build the wheel.
First question: " what offset do you want?" I had no idea so Harry ( who owned the shop) said: "well, I'll use a standard BSA offset, & just let me know if you have any problems with it".
Now this A10 had an A65 front end on it, but as near as I can recall, I don't remember that the wheel looked off-center when mounted on the bike.
It's difficult to see it clearly in the photos, but the scale shows approximately 0.650" from the rim of the brake drum to the wheel rim. HTH
Phil
[Linked Image][Linked Image][Linked Image]

Attached Files Offset 1.JPGOffset 2.JPGOffset 3.JPG
Re: BSA 8" half width front hub offset please? [Re: Phil R] #758404
12/07/18 2:44 am
12/07/18 2:44 am
Joined: Oct 2004
Posts: 120
Adelaide South Australia
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GROG Offline OP
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Adelaide South Australia
Phil,
Thanks for the response... I will dig out a WM2 rim and measure the outside width so I can work out what the distance to the centre of the rim is.
Hopefully my WM2 rim will be the same outer width as yours. (I'm using an 18" flanged alloy rim for this build, it's a road racer and a bit of a Bitza, but should be fun)
I will also check that the A65 had the same fork leg spacing as the earlier pre-unit swingarm models... I expect it would have, so your info should help for sure.
Thanks again,
Greg

Re: BSA 8" half width front hub offset please? [Re: Phil R] #758405
12/07/18 2:49 am
12/07/18 2:49 am
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Adelaide South Australia
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Sorry Phil,
Would it be possible for you to measure the outer width of your rim so I can calculate that distance from drum face to rim centre please?
I just had a look and don't have any old 19" steel rims anywhere, I did a scrap run recently.
Cheers,
Greg

Re: BSA 8" half width front hub offset please? [Re: Phil R] #758430
12/07/18 1:47 pm
12/07/18 1:47 pm
Joined: Oct 2004
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Adelaide South Australia
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Adelaide South Australia
Ah, cancel that last request Phil.
Someone local checked their bike for me and they agree with you, assuming your rim is about the same as theirs. So I rang the wheel builder who is doing it for me and it turns out the turkey was not measuring to rim centre.... like his Dad told be to do years ago when he was still doing wheels.
He died a while back, but wold be turning in his grave most likely...haha!
It seems the father-son communication was not what it should have been.

Thanks again for your help.... two answers the same give me great confidence.
Cheers,
Greg

Re: BSA 8" half width front hub offset please? [Re: GROG] #758436
12/07/18 2:39 pm
12/07/18 2:39 pm
Joined: Aug 2015
Posts: 1,301
Bolton Lancs UK
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Andy Higham Online content
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Bolton Lancs UK
IMNSHO measuring to the outside of the rim is asking to go wrong, different makes, styles and material rims are different widths.
The centre line of the rim is the important datum. Measure from the drum edge to the edge of the rim then add on half the rim width to find the centre line. When building the wheel subtract half the width of the new rim from the centre distance and measure to the edge.
I have just measured a few wheels
Akront WM2 flangeless alloy = 64.9mm
Morad WM2 flangeless alloy = 66.9mm
Borrani WM2 Flanged alloy = 65.7mm
DID WM1 steel = 70.2mm

So the narrowest rim is actually the widest


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Re: BSA 8" half width front hub offset please? [Re: Andy Higham] #758452
12/07/18 3:53 pm
12/07/18 3:53 pm
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Phil R Offline
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Greg,
Glad it all appears to be working out.
Looks like Andy may have you covered as well.
Sorry for the photo separation in my initial post, when previewed they appear fine, but when posted take on this "thumbnail" effect.....very mysterious....

As for the wheel builder's father "turning in his grave"....."Harry" (mentioned in my initial post) passed away years ago.....so hopefully, I won't need to get any more wheels rebuilt myself ! grin
Best of luck with the project.
Phil

Re: BSA 8" half width front hub offset please? [Re: GROG] #758492
12/07/18 7:34 pm
12/07/18 7:34 pm
Joined: Aug 2001
Posts: 4,251
argyll. scotland, uk
gavin eisler Online content
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Triumph steel Dunlop 19" WM2 , 68.5 mm across the rim, fresh off the calipers , had this lying handy.


71 Devimead A65 750
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Re: BSA 8" half width front hub offset please? [Re: Andy Higham] #758537
12/07/18 11:06 pm
12/07/18 11:06 pm
Joined: Oct 2004
Posts: 120
Adelaide South Australia
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I fully agree Andy.
Once my old wheel builder woke me up to using the centre as the only way to do it in future I've stuck with it... a pity he died before he'd beaten that into his son...haha!

For kicks, I averaged your WM2 rim widths along with Gavin's Triumph rim and one I measured at a mate's place yesterday and came up with a figure of 66.4mm and that, along with Phil's edge offset figure (matched by what my local guy measured (edge offset and rim width) gives me 49.6mm..... so my original instruction to the wheel builder of 48.5mm was not too bad.

Since 48.5 is what I measured before pulling the old wheel apart that figure is what I will stay with..... once I'd pointed out his (obvious?) error he will go ahead with that figure.

I had been unable to check if the old wheel was laced to be central in the forks, because it came to me separately to the rest of the bike which as in pieces at the time and the forks were of the wrong model to accept it anyway. So all your efforts on this post have given me some confidence it should be within a millimetre of central. That will be quite adequate in my opinion.

Thanks again to all. It is appreciated. The bike is being built up to race on the beach at the forthcoming Sellicks Beach re-enactment race event early next year....and since I am currently designing and building a new custom crank for it at the moment... hurriedly trying to get the bits made to get them into the heat treater before next Wednesday so I can get them back before the Christmas close down, the last thing I needed was a hassle with the wheel build.
Cheers, and an early Merry Christmas!
Greg

Re: BSA 8" half width front hub offset please? [Re: gavin eisler] #758538
12/07/18 11:07 pm
12/07/18 11:07 pm
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Adelaide South Australia
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Thanks Andy, see my other reply to the guys that helped out.

Re: BSA 8" half width front hub offset please? [Re: GROG] #758540
12/07/18 11:10 pm
12/07/18 11:10 pm
Joined: Oct 2004
Posts: 120
Adelaide South Australia
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Adelaide South Australia
Oops.... sorry for my clumsy replies.... I've not used this forum for quite a few years and forgot how it is structured... ie in replying generally or to specific people in the thread... and sorry Gavin, I called you Andy....lol. Some days I should not rush.

Re: BSA 8" half width front hub offset please? [Re: GROG] #758566
12/08/18 3:10 am
12/08/18 3:10 am
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Phil R Offline
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Greg,
Post a picture of your racer when it's ready, I'm sure there'd be a lot of interest especially if it approaches anything even close to those on your website.....really nice machines!
And BTW, has there ever been there a more serious, purposeful or just down-right MEANER looking engine than a J.A. Prestwich....?
I DON'T THINK SO !!
Best,
Phil

Re: BSA 8" half width front hub offset please? [Re: GROG] #758567
12/08/18 4:09 am
12/08/18 4:09 am
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Posts: 120
Adelaide South Australia
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Adelaide South Australia
Phil,
Yes, I will. There will be periodic updates on my Farcebook page if anyone is interested but for those that avoid that media I will probably remember (hope so) to post some pics here.

As for the JAPs, well, they are my first love. The big 1000cc racing V twin model 8/80 is my favourite, having built three of them from scratch for road racing and speedway sidecar. I've rebuilt quite a few of them too, they are used not only in vintage speedway sidecars but also in Cooper open wheeler race cars. I have made a bit of a name for myself with my conversions of their bottom ends to use modern stiffer and more durable interference fit crankpin and mainshaft cranks... with Carrillo rods of course.

Have a look and a listen to some of those engines via these links

http://www.youtube.com/user/grannyjumast
http://www.facebook.com/greg.summerton
http://www.eurospares.com/greg.html

Cheers and thanks again.
Greg


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