Britbike forum Forums British motorcycles in general British modified/specials Twin disc setup?

I saw awhile back in a magazine someone with a T140 that had fit some sort of Honda forks with a twin disc setup, this was on a street/drag bike. I think they were an inch or two shorter than the Triumph forks, too. I'd like to do the same but am lost on where to start. Should I look for a Honda front end with twin discs and forks that are the same diameter as my t140's and just switch them out or will I be looking for a new front wheel as well? I'd like to keep my front wheel if possible.
Thanks

I am putting a Yamaha xs650 on my 1963 BSA a-65. I am having a machinist turn some bearing cups to be welded on to the BSA that will hold the Yamaha tapered bearings. I am also having the steering stem reduced and possibly the fork legs and springs reduced. When finished I will post. TC

The T140 axle is part of the hub whereas most H*nda wheels have a removeable stepped axle that is pulled against the inside of one fork leg by the nut. You could put a sleeve in the T140 hub so a stepped axle arrangement can be used. Look for a H*nda front end that uses the same bearings (6204?).
The steering stem is another matter. Easiest to press out the T140 stem, weld/cut a piece on to fit the H*nda stem hole and press in. Make a sleeve for top triple clamp.
Of course then you have to mount the H*nda discs on your T140 hub possibly with new carriers to match the caliper spacing.
Less work to add a second Triumph disc, fork slider, caliper and hoses. The stock 5/8" master would then be the correct size.

Yeah DM sounds like a lot less hassle. I was hoping for some reason it'd be less expensive to go the retrofit route, but perhaps not. Thanks.
So how do I find a fork slider for the right side that'd place the caliper on the after side of the forks? So far as I know, Hyde is the only source for such a thing or did Triumph make a twin disc model of a triple or something at some point?

Triumph made them but they are rare (expensive). If you know a good welder you can have tabs welded to the drum slider. You have to pre-heat the slider to keep it from distorting. You can make a simple bracket to hold the pieces that bolts onto a piece of bar stock held in the axle mount.

I'm not sure I get that last bit. Could you explain in a little more detail? Thanks.

Hi,

Anything can be fitted to anything, given enough time and money.

However, if you want to achieve your goal while spending only sensible amounts of time and money, perhaps the following bits of first- and second-hand experience might be of use:-

1. Japanese forks with 35mm dia stanchions require only a small amount of machining to the Triumph yokes/triple trees to fit. However, finding forks that would take the Triumph axle might prove too great a challenge. Also, dunno what corrosion problems you experience in Maine but here in GB, Japanese alloy corrodes like crazy and some of their more Heath Robinson swinging and sliding arrangements need stripping at least every couple of years, unless you remake pivots, pins, whatever in stainless (same goes for XS650 brake bits ).

2. A Triumph right-hand disc slider, second caliper and disc might be the easiest route to retaining the existing Triumph front wheel. As well as Norman Hyde, certainly British dealers like Triple Cycles (www.triples.demon.co.uk) and L.P. Williams (www.triumph-spares.co.uk) have right-hand disc sliders; whether your wallet can handle the exchange rate is a matter between uou and it.

One thing you may want to know is that there are two slightly different r-h sliders. Originals have the seal held in with a circlip; certainly L.P. Williams makes the seal holder more like the pre-circlip ones.

You can fit alloy calipers from Lockheed or Grimeca, or match the standard original caliper by fitting another one upside down on the right. Bleeding isn't a problem if you also fit braided hoses, you simply unbolt the caliper from the leg and turn it 'right way up'. Ime, the weight of twin steel calipers doesn't affect the handling.

Lockheed made (make?) alloy calipers with two different piston diameters. The large ones are the same as those in the steel calipers, and it's debateable whether a 5/8" i.d. (single-disc) master cylinder is sufficient - it's possible but you get a lot of lever travel. Lockheed actually supplied Triumph with 7/10" (*not* 3/4") i.d. for twin calipers with large pistons. The alloy calipers with smaller pistons were supplied to Triumph later so that Triumph could fit a 5/8"i.d. master cylinder irrespective of whether the bike was going to have single or twin calipers.

The r-h slider caliper mountings are threaded UNF and helicoiled as standard, so that the caliper can be removed easily for wheel removal/replacement. I recommend doing the rethread/helicoiling to the l-h slider too.

Hoses are much easier if you use the L.P. Williams cross-over tube. This bolts to the lower yoke stanchion clamps and takes a banjo in each end. You then just require a banjo-fitted hose from each end to one caliper and a third banjo fitted hose from one end to the master cylinder; this can be two single banjos on a double banjo bolt at one end or a double banjo on a single bolt. You can also attach a banjo adapter, perhaps on the opposite end to the master cylinder one, to take the proper '79-on brake light pressure switch.

Standard Triumph springs and dampers are poor by modern Japanese standards. Progressive springs aren't too expensive and are a worthwhile mod. on their own; however, to match modern standards, you need the (expensive) damper rods from Triple Cycles.

Hth.

Regards,

Whew. That's a lot to digest. thanks!

Hi Sisyphus if you want to see what the front end as described by Stuart looks like , go to the 3rd page of post a pic of your Triumph and look for my bike , 'cos thats the front end I've got , it's the red triple . Johnny .

I made a mirror image caliper bracket with undersize bolt holes. Then made another that bolted to this and fit over a dummy axle bolted in the axle mount. This held everything in place for welding. Afterward, set the slider on the mill and drill/tap the caliper mounting holes and skim the mounting surface square to the wheel plane at the correct offset. I made a reamer to go into the slider to clean up any distortion on the inside.
Sounds more complicated than it is.

I think Norman Hyde do a large diameter floating brake disc kit (13"?) to get good braking with a single-sided system.

Twin-discs do look better though.

hey DMadigan

What the story on that disc of yours.
Is that a stock disc, drilled and cut-out?
Did you do it?
What is the seemingly black finish?
Thanks

I windowed and drilled the stock disc. The black is just Orrlac laquer. The pads will cut it off the running surface. I just wanted to keep the rest from rusting.

Hi Peter,

Ye-e-a-ah ... but have you seen what even a standard single 10" disc does to the forks when you grab even a reasonable handful of brakes? Why do you think original single-disc forks used to leak so soon after seals replacement, before Triumph introduced super-seals?

Hth.

Regards,

Norman hyde works well..... I have one on mine.
Stops on a dime and gives you 9 cents change.

They also sell a fork brace if you've deep pockets

This is a xs 650 fork and hub assembly mated to a
yamaha rear 18" rear rim. I bored out the lower norton tree and added adapters on top of the forks. A magura master cylinder provides two finger braking.

Since adding a japanese front end wasn't bastardizing it enough I added a set of dual 34mm mikunis.

c

c

two answers in one! i have fitted a comlete front end off a m guzzi cali that comes with twin brembos and 18 inch alloy boranni rim, to make the bite snapppier on the huge 260mm cast discs i fitted ferodo 4004f pads and a master cyl off a 916 duke, if you dont need to modify it youcan always move it on later to a guzzi man.
The cheap option as done in early production racers was to fit a left leg reversed so as to fit the extra caliper forward of the spindle and use a modern 16mm or larger bore master cyl, I have this setup on my racer with 2 std discs and its as good as you'l ever need on the road it just looks a bit odd!

Hi,

How is it cheap? You still require exactly the same number of components as you do with a right-hand caliper behind the leg. Perhaps in theory a left-hand slider should be cheaper because there are more of 'em; in practice, usually the final arbiter is what's available for what on Fleabay.

Imho, fit a 'reversed left-hand' slider on the right and all you end up with is a dog's breakfast. :rolleyes: The *only* reason production racers fitted a l-h slider on the right was because, between 1973 and 1978, Triumph *only* used one slider, so it was the *only* way of getting twin front discs through the increasingly-stringent production racing regs. of the era. Probably the most famous Triumph production racer of the era with this arrangement is Slippery Sam; ask people like Mick Grant, Alex George or Dave Croxford, who actually raced Sam, how happy they were, say, braking at the bottom of Hilberry with the arrangement.

16mm is barely larger than 5/8". As I said in my earlier post, this can be made to work with twin Lockheed calipers having 'usual-diameter' pistons, but you end up with a lot of travel at the handlebar lever and, certainly if you have a dog-leg lever, the lever will hit the handlebar grip before the brakes are fully applied. This is precisely why Lockheed originally supplied Triumph with 7/10" (18mm as near as makes no odds) i.d. master cylinders for twin front discs.

Contemplating this mod. to one of my triples, tapping into the collective experience of the British classic racers in the Trident & Rocket 3 Owners' Club found widely-varying opinions on its usefulness - in short, the effects work for some but not for others. Certainly ime, steepening the head angle by not very much (just by raising the rear a little, in my case) had fairly dramatic handling/steering results.

Hth.

Regards,

yes the reversed leg is fine and for most a cheap option certainly as thr leg and caliper are oem (mine has 2 notch lockheed and is rock hard)....i did say 16nmm or bigger! a pad ratio as suggested on the tzowners site works well at 27:1 pad area to piston 13: is softer feel amd fine in my experience...i thought this was for a cafe racer not doin the tt??...the guzzi fix is good cause the calipers are alloy and the pistons smaller ...hence 16mm

late night fingers...should read "27:1 pad to piston area is recommended but down to 23:1 is softer feel but fine in my experience" the two front ends are certainly ok for a t140 but yes with the extra weight and speed of a trident brakes are more sstressed. I have raced a number of twin disc set ups all 10" ish with cast iron rotors and lockheed racing or std two piston calipers and found with ferodo or mintex race pads these to be a good stopper, with the price of big single (floating or otherwise) conversions a twin conversion with std kit makes some sense.