Been riding Thunderbird 5 for a couple of years now, and try as much as I can, I just don’t like them bloody linked brakes. Had me on me chuff t’other winter, just touched the rear brake, forgetting it operates the front as well. And went down like a sack of shyte…
So THIS Drunk Drivers season, when I usually use the tin box for the commute, I thought I’d have me a go at ‘De-linking’ the brakes, only trouble is, I’m GORMLESS, and don’t know what’s needed, or indeed how to do the job…
Can anyone out there enlighten me please…
Also, does De-linking, make it easier to bleed the system, what a pain in the chuff that is, even using a syringe to back feed the fluid in, is a pain…
Course, being tighter than a Crab’s chuff at 50,000 fathoms, I will leave it be if it involves spending excessive Beer tokens, can’t be wasting good Beer money on brake parts, not when there’s a whole new season of camps upon us…
The handlebar master cylinder will work both front discs just fine, in fact it will give you a better feel to the brake with a bit more movement. You need a splitter to feed 2 calipers mounted on the yoke somewhere or use 2 long lines and a double banjo connector.
Getting the rear to work well is apparently a nightmare.
The better solution is to get the Spada splitter which puts the rear on first and then the front.
It also has a bleed nipple which makes bleeding the brakes easier.
With not much practice you can learn to just apply the rear.
The Spada splitter will be difficult to find and will not be cheap.
They do wear out with age, the control valve thingy (actually a sort of rubber grommet type thing) stops working, I once tried to rebuild one but couldn’t, so got a whole new one, but then you could back then (1982 -ish?) doubt there are any new ones to be had anymore, and in any used ones you can find, the rubber bit will be knackered anyway from old age. Doubt Shaun wants that kind of aggro.
I think the issue with the rear master cylinder is that it’s chosen to drive 2 calipers, to change to single caliper requires smaller diameter piston, or summat, else leverage is too low. Something like that. Will work, just not very well.
I forgot, the Spada also had the larger P9 caliper (with different larger pads); ALSO, the brake pads’ friction coefficient (correct term?) was different for each caliper, these different grades you can’t get anymore, so it’s all a non-starter really as an idea.
I’ve never managed to get my SP to work the rear disc only. I think that is a bit of a falicy.
As for getting the rear disc working, logic would say you need a smaller piston on the pedal as the one fitted is designed to operate 2 calipers, but others suggest otherwise.
A mate had a T5 and he de-linked the brakes, front was great using the original master cylinder, the back was poor.
I agree with Don, I think the SP valve operates both brakes together and then shuts the rear off at a certain pressure.
I’ll have a look in Guzziology and see if there is a recommended size for delinked rear master cylinder.
I’ve d linked a few, always used a jap front master cylinder, (bit difficult on a t5 due to the switches).
Back brake simply use one ss line from the master cylinder to the caliper, it feels weak at first, (no massive retardation from front and back disc’s), but if you push hard you can lock the back wheel and the bike always passes the MOT brake test.
For the brake light switch, a pressure banjo bolt type worked on 1000s, used a common jap bracket+spring type for the cafe racer as no room on the t3 frame for the pressure switch
Used to do it all the time.
It is why I used to get through rear pads in 8,000 miles, flh pads in 15-20,000 miles and frh pads I used to change when they got crumbly.
Never bothered with the different friction materials,
I never really realised how much I used the rear until on the way to Applecross I wore through the link pipe with my rear tyre so I blanked off the hole out of the splitter and carried on.
I hardly noticed any difference in braking.
There has also been 2 occasions when I am going round a corner, have to brake hard and feel the front start to slide so I let the brake off gently whilst still braking on the rear and then reapply full brakes when the front starts to behave again.
As the only reason for braking in a bend is ‘oh sh1t’ this has been a definite plus.
You reminded me, sure I read somewhere at the time that it’s supposed to make 50/50 front/rear braking force initially, then increases the front (only) if you press harder. But it all hinged on the proportioning vavle working as it should, and choice of pad compounds. Think it was something like, the P9 (rear) was medium, i.e. bog standard, and the front P8 was ‘soft’. I.e. more grabby.There was also a ‘hard’, however the ‘soft’ and ‘hard’ options disappeared maybe 20 years ago or more.
