1969 A65 Front Fork Lengths.

[DAVE BRADY]

I have just done a simple drawing and the difference across the bottom of the forks and the angle of 1deg makes is less than 1mm and probably 0.7mm.  This would in effect move the centre line of the rim by about 0.75mm off line. The tyre edge the same, so in theory to compensate for this the fork slider would only need to be about 0.7mm longer so why 3.5mm longer.  This is unlikely to correct itself under load as it would require the twisting of the spindle in the bottom clamps.
Does anyone know if they are actually running a bike with these different length sliders?

Dave.

[Wilf2019]

Dave,
I agree with what you are saying regarding the slider lengths. It seems strange, but looks to be common. I wish I could explain it.

Julian,
I will check the wheel offset tomorrow. These wheels are newly built so worth checking.

Also I have just fitted new wheel bearings, so it makes me question if the bearings / spindle are seated correctly.

I will check the bike off the stand tomorrow. But as the engine is out there is not much weight to it, so don't think it will alter much.

Even with just a bare spindle fitted though the angle it quite steep with the 3.5mm difference between fork legs.

[Bess]

Hi Dave,
             I've searched around for quite awhile in the past and never discovered why, this issue crops up regularly. The service sheets give a reason which I guess we have to believe no matter how our gut feeling suggest a factory machining problem.

http://www.britbike.com/forums/ubbthreads.php/topics/686454/2

Usually people just live with it or decide it was a manufacturing fault and machine the slider ends to an equal length, drilling the hole horizontally. Some fit the wheel and adjust the offset so that the wheel is central to the forks. personally I have only fitted sliders of equal length discarding the rest.


Best wishes...

[morinipete]

Hi, just to add to this the front wheel should slope. The reason is that it is impossible to get the front and rear wheel to align properly as when the engine was designed it had the final drive sprocket too close to the centre line of the bike. As such the back wheel is out of line. On Press bikes they'd pull the back wheel right over and cut a bit out of the chain guard so the chain was running on the tyre! On the production bikes they sloped the front wheel so the two tryes, back and front, were in line where they made contact with the road. Triumph and other BSA forks - B25, Rocket 3, etc - all hold the front wheel vertical, but A65/50 ones slope. I know it looks wrong, but its right! Incidentally this all came from Mick Bowers, Les Mason, etc who worked on this in the factory. Les also said it was done as built vertically bikes tended to pull to the left. In the UK this put you in a ditch, in the States it put you into the front of a Buick and BSA didn't want any insurance claims!     

[Bess]

Hi morinipete,
                     Thanks for the information, makes perfect sense now.

Bess...

[DAVE BRADY]

Does this need to slope the spindle only apply to forks with caps to hold the wheel in?  What about the 1/2 width hub?
If the reason was to compensate for an off centre back wheel then the push through spindles must also be on a slight angle.  I will have to measure mine tomorrow to see. Would the tendency to pull to the left apply with other forks fitted?
I have a non BSA front end and have never experienced anything but straight line steering and although several people on the Britbike forum have altered their forks to be equal length they have not mentioned a tendency to pull to the left.
Also, wouldn't a wheel angled over to the left tend to steer left?
It is possible that this was necessary to counter the camber on UK roads but surely the angle would have be the other way for US and European roads where the camber goes to the right.  The other interesting thing is the effect of a left hand camber and driving on the left is the greater wear on the righthand side of a front tyre.  Did this not happen on A65s as it did on A10s and B40s etc.?  I do not doubt anything that has been said but to me there are still questions.

Dave.

This arrangement of the wheels must  have also caused problems when wheel alignment was checked at MOT.

[Bess]

Hi Dave,
             Looks like before 1966 it wasn't an issue.

The +1° replacements with the A stamped in replaced the spindle sliders, 1966 to 1968:-

https://www.ebay.ie/itm/262837440669

The sliders with the counter bores supplied as standard were caps as shown in the image.

Best wishes...

[Wilf2019]

There is certainly some useful and interesting information coming up here with the various findings.

Dave,
I think once weight is on the forks and the bike is ridden the wheel should pull itself vertical? The difference in fork length would only happen with the forks on maximum travel with the weight off the wheel.

With weight on the forks there would be slightly more spring tension on one side, but only say 3mm. Am I right in thinking this?

I was thinking that it may be possible to shorten either the top bush or the fork inner sleeve by a few mm on the shorter fork leg rather than machining the bottom of the longer leg, as had been done by some people.

Or just leave it as it is, even though it certainly doesn't look right, and not common on most people's bikes. 🤯

Thinking back when I stripped the forks apart - the inner sleeves were very deteriorated and more of a rubber material than the plastic that it is now replaced with. Therefore the angle would not of been noticed.

[DAVE BRADY]

Hi,

Every time I see an A65 now, I will have to have a look.
So the spindle clamp is first tightened on the right/brake side with the other one left loose. The forks are then pumped before it is fully tightened. Perhaps this action helps to preload the longer fork leg and tightening it up holds it in that position with a barely detectable slope to the left.
I wonder why the offset rear wheel did not cause a problem with the earlier forks - we will probably never know.

Dave.

[DAVE BRADY]

Good morning,

I have measured the sliders fitted on a '69 A65 and they are 'counter bored' and of different lengths.  The sliders from a '68 A65 with push through spindle are the same length.
So the sliders are right but for me the question why still remains.

Dave.

[Wilf2019]

Thanks for the info Dave. That's good to know.

Does the wheel look cocked over one way in the forks at the top?

I'm not sure why either. The question is, do I leave the wheel cocked over or try and adjust the bush / sleeve to bring the wheel more upright!

[DAVE BRADY]

Hi Wilf,

The wheel is slightly over but it does not seem to be a much as yours.  If you check the offset as mentioned previously just in case it needs pulling over a bit.
Until this thread I had never heard of this despite many years with an A65 but then again the one I have had the longest and used the most has a non BSA front end and previous to that it was an A10 combo with leading link forks or an A10 solo.  I still cannot see why this strange way to address a problem (?) came about.  Why was there only a problem with these particular forks and only on the A65? 
Being a bit cynical I still suspect an attempt to correct a cockup in the manufacture of the sliders and as the next design for the oil in frame was on its way why not save some money and bodge a modification.

Dave.

[Bess]

Hi,
     As BSA did the adaption to ensure the wheels are in line if I build another I will try and fit sliders with the +1°.


morinipete stated, "I know it looks wrong, but its right!"


Best wishes...

[Wilf2019]

So, I have just checked the wheel offset. The brake drum face is near enough flush with the edge of the rim. The rim is approximately 68mm wide. Therefore an offset from the centre is 34mm.

The manual says it should be 1-11/64", which is approximately 29.8mm. So just over 4mm error!

If this offset was correct it would bring the wheel back the correct way to centralise the wheel.

I think I will now need to speak to the guy who built the wheel and see what he says. 

Thanks for all of the input.

Wilf.