BSA Owners' Club Forum

The BSA Workshop => Twins => Topic started by: boriscross on 15 December, 2017, 14:56:54

Title: A65 OIF conversion to disc front brake.
Post by: boriscross on 15 December, 2017, 14:56:54
Has anybody any experience of this? I assume that you could take the front end of a late Triumph and fit this onto the standard frame but I might be wrong.
Title: Re: A65 OIF conversion to disc front brake.
Post by: A10 JWO on 15 December, 2017, 15:12:37
Sounds straight forward but expensive albeit you could sell your old sort after front end. If a front end off a Yamaha fits my mates 500 Triumph I can't see why not. A T140 may be a good donor. I always thought that later twin Triumphs appeared to look lanky at the front, perhaps the forks are a bit longer or it's my perception. Let us know how you get on and good luck.  8) 
Title: Re: A65 OIF conversion to disc front brake.
Post by: Editor on 15 December, 2017, 16:20:25
If you do, watch out for the steering stops. Someone did this on my mates Triumph TR6R OIF and they cut off the 'arc of cup' (for want of a better description) steering head stops. I had to do a total rethink to change it back to standard front.
If you do need to, keep the steering stops in case you ever want to change it back.
Chris
Title: Re: A65 OIF conversion to disc front brake.
Post by: Mike Farmer on 16 December, 2017, 09:47:43
 :)

I put a Commando front end on a 1967 A65. It was only a case of having a couple bearing collars made. Its a long time ago but I THINK the commando head bearing OD was marginally less than the BSA. Cant remember about the steering stops.

Good luck.

Mike 8) 8)
Title: Re: A65 OIF conversion to disc front brake.
Post by: Editor on 16 December, 2017, 16:16:01
Mike,
This is an OIF frame. The steering stops set up is alot different compared to the pre OIF version.
Talking about the pre OIF, on my Royal Star, there are two drilled and tapped holes(1/4 UNC - 1970 frame) on the bottom yoke steering stop pad. I believe this was done to limit the side to side lock when a fairing was fitted. Without bolts in there the steering lock is so great, with low bars you trap your left thumb between the handlebar grip and the tank, it comes over that far!!! ouch!
Chris
Title: Re: A65 OIF conversion to disc front brake.
Post by: Steve Tipper on 16 December, 2017, 17:20:54
AFAIK a complete T140 type front end will bolt straight up.
You have to use the T140 type yokes as the fork tube centres are further apart on the disc front ends.
There are no mounts for the wire type headlamp brackets  on the top yoke but nobody seems too fond of them anyway.
The '71-2 mudguard won't fit without bending out the wire stays, but again, nobody seems to be too fond of them either.
Title: Re: A65 OIF conversion to disc front brake.
Post by: Ken Oaff on 17 December, 2017, 18:51:31
fitting a T140 front end to my 71 A65

made up spacers to fit original front guard

had custom alloy top yoke made up to suit the original wire headlight stays
Title: Re: A65 OIF conversion to disc front brake.
Post by: Editor on 18 December, 2017, 16:31:20
Do the steering stops on the bottom yoke connect with the original A65 stops o the frame?
Title: Re: A65 OIF conversion to disc front brake.
Post by: Ken Oaff on 19 December, 2017, 19:38:09
Had a look at that, probably not but its a minor problem to solve on the grand scale of things

Trying to find a decent single seat that mounted to stock seat hinge and latch and decent rear sets was a far bigger issue, ended up making my own seat base and own rear sets
Title: Re: A65 OIF conversion to disc front brake.
Post by: Editor on 20 December, 2017, 11:30:45
Thanks Ken,
I was just wondering if prev owner removed the stops for no reason. Anyway, it is something to consider as necessary before shelling out for the T140 front end.
Title: Re: A65 OIF conversion to disc front brake.
Post by: Ken Oaff on 22 December, 2017, 09:20:14
I think the serious question you need to consider is that 45 plus years later is the conical front brake suitable for modern traffic, the disc option with a caliper upgrade is far more suited to todays traffic
Title: Re: A65 OIF conversion to disc front brake.
Post by: Editor on 22 December, 2017, 10:45:16
Each to their own Ken. The bikes don't go any faster and idiots use to pull out in front of you back then but I suppose the car in front stops quicker these days. That's why I always leave plenty of room in front.
Both my conical hubs the A65 and the B25SS work really well. The B25SS is really effective but then it has the standard, longer brake levers on the plate. Why they didn't make these standard on all, we'll never know.
Title: Re: A65 OIF conversion to disc front brake.
Post by: Ken Oaff on 24 December, 2017, 09:35:16
true, the bikes don't go any faster but the general traffic is quicker and a lot more of it

also brakes on modern vehicles are a lot better

also have a 916 series alfa spider v6, brakes on this were ok when it was built but on todays roads I have to leave a huge gap in front of me because modern cars can stop that much quicker

Title: Re: A65 OIF conversion to disc front brake.
Post by: Mike Farmer on 24 December, 2017, 11:35:38
 :)

That gap sounds awfully sensible to me regardless of what brakes you have. About half the required braking distance is taken up by thinking/reaction time. AND that hasn't improved much over the years for most of us.
Then if you do stop quickly enough you get rammed by the other twerp who is driving tooooooooooooo close. Hence multi car pile ups.

Theres really no single answer to it. I too spent a great deal of time flying. The adage: "If you give yourself space you will be giving yourself time".

Happy Seasons greetings whatever you are celebrating

Mike 8) 8)
Title: Re: A65 OIF conversion to disc front brake.
Post by: A10 JWO on 24 December, 2017, 16:59:49
Would the lower fork legs from a T140 be the same size as OIF A65 legs. If so just change the lowers to accommodate the disc etc. Just a thought ?
Title: Re: A65 OIF conversion to disc front brake.
Post by: Ken Oaff on 25 December, 2017, 20:26:29
no yokes on T140 are about 1/2" wider than A65
Title: Re: A65 OIF conversion to disc front brake.
Post by: CROFTY1984 on 13 January, 2018, 10:54:49
I have both, as it happens! Maybe I can weigh in?
As others have said, the yokes are different as the hub and brake assembly is wider, so you can't use just the forks or just the lowers. The top yoke has no mountings for the headlight bracket wires.
The top yoke on the bonnie is a clamp-on type, whereas the BSA is tapered forks at the top.
I honestly have no idea about the compatibility of the steering stem and bearings, but I would think if they only need minor modifications your best bet would be a complete T140 front end.

Some notes on the bonnie brake:
The chrome discs look very nice. You can admire them as you stuff yourself into the back of the car in front. They're awful. The best value upgrades I did to mine were: single piece braided hose, M/C mount pressure switch banjo, the best pads LP Williams sell, lightweight disc, rebuild calliper.
That lot was probably about 150, not far off what one disc cost me for the Kawasaki! I can't recommend them enough.
You can of course get twin discs and larger single disc, but then you're talking big money. I also like that it still looks fairly "period".