Font disc brake T140 upgrades.

Font disc brake T140 upgrades.

Postby bigstu » Sun Jul 05, 2009 1:12 pm

I am dealing with a 1981 T140 with a std brake except a braided hose.
It feels 'wooden'.
Does anyone know what the standard caliper and master cylinder piston diameters are?
What upgrades are available?
Thanks. Stu.

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Re: Font disc brake T140 upgrades.

Postby L.A.B. » Sun Jul 05, 2009 2:18 pm

bigstu wrote: It feels 'wooden'.

Does anyone know what the standard caliper and master cylinder piston diameters are?


Indeed they do feel wooden!

The hydraulic ratio between master cylinder and caliper are somewhat less than ideal, but apparently it was designed that way!

The master cylinder is 5/8" dia. which is really too big for the two piston single Lockheed caliper.






bigstu wrote:What upgrades are available?


Depends on how much you intended to spend? As there are various options including twin disc conversion kits. But fitting a smaller diameter master cylinder would be a good starting point?
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Re: Font disc brake T140 upgrades.

Postby B+Bogus » Sun Jul 05, 2009 2:59 pm

I fitted a pair of Lockheed racing calipers and braided hoses to mine and kept the standard master cylinder in stainless. The only concern I now have is whether the frame is adequately braced to deal with the increased performance!
The front brake has good feel and will deliver any amount of power with just two fingers. I'm very pleased with it - previously the single disc with everything standard (including hose) was barely adequate with poor feel; now it's as good as a modern sportsbike, and quite a bit better than my Ducati.

Highly recommended!
Cheers,

Andy

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Re: Font disc brake T140 upgrades.

Postby L.A.B. » Sun Jul 05, 2009 3:33 pm

B+Bogus wrote:The front brake has good feel and will deliver any amount of power with just two fingers. I'm very pleased with it - previously the single disc with everything standard (including hose) was barely adequate with poor feel; now it's as good as a modern sportsbike, and quite a bit better than my Ducati.




I have the same setup, but with twin Grimeca calipers and EBC HH pads on my T160, and that pulls up very well, even though a T160 is over 100 lbs. heavier than a T140.
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Re: Font disc brake T140 upgrades.

Postby bigstu » Mon Jul 06, 2009 3:52 am

Thanks, guys.
I now know the master cyl piston dia is 5/8" , same as my Commando.
The other bit I need now is the piston dia of the caliper. Does anyone know the caliper piston diameters?
I found on the Commando that the biggest improvement I made was the reduction in diameter of the master cylinder piston.
The big disc and Grimeca caliper helped but did not improve the feel. It still felt 'wooden' until I went for an 11mm dia piston.
Of course that was with the Grimeca which had 2 x 42mm pistons
Stu

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Re: Font disc brake T140 upgrades.

Postby B+Bogus » Mon Jul 06, 2009 4:24 am

bigstu wrote:Thanks, guys.
I now know the master cyl piston dia is 5/8" , same as my Commando.
The other bit I need now is the piston dia of the caliper. Does anyone know the caliper piston diameters?
I found on the Commando that the biggest improvement I made was the reduction in diameter of the master cylinder piston.
The big disc and Grimeca caliper helped but did not improve the feel. It still felt 'wooden' until I went for an 11mm dia piston.
Of course that was with the Grimeca which had 2 x 42mm pistons
Stu



Stu,

Doubling up on the calipers will clearly improve the leverage ratio by a factor of 2; the AP calipers are 41.3mm - but a bit pricey!

http://www.apracing.com/info/products.a ... _2536_1085

Has anyone tried the 11mm cylinder with twin discs, I wonder?

Another thought...has anyone upgraded the cylinder and then subsequently upgraded the single standard Commando disc/caliper?

A VMCC friend suggested my Bonnie was overbraked....not sure I recognise the word ;)
Cheers,

Andy

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1964 650SS CR project
1971 Production Racer project in progress
1975 Ducati 900ss x2
1976 Triumph Bonneville
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Re: Font disc brake T140 upgrades.

Postby bigstu » Tue Aug 04, 2009 4:35 am

Using one 41.3 twin pot caliper and a 5/8" master cyl piston the ratio is 13.6 : 1 so it will feel wooden.
If you put twin discs on you will get a ratio of 27.2, so it will feel great. The lever will pull back to the bars in the garage but not on the road, I'll bet!
The only problem here is cost.
I went for a master cyl of 11mm dia to go with my twin pot grimeca setup, which also has 2 x 41.3 pistons down below.
My ratio is 28.2. I bought the master cylinder off a mate, it came off a 125cc scooter (AJP caliper). It cost me £10, and I had it installed in 1 hour.
The increase in performance is massive. I also have 2 finger braking.

Where twin discs come in is I am suffering from fork flexing, and need a brace, where as twin disc setup will be more even on the forks.

Its all a matter of cost.

Thanks for all the advice and the piston diameter specs.

Stu.

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Re: Font disc brake T140 upgrades.

Postby Corona850 » Tue Aug 04, 2009 7:16 am

B+Bogus wrote:Has anyone tried the 11mm cylinder with twin discs, I wonder?


That would be much too small a diameter master cylinder for twin disks, I think. The 11mm gives a good hydraulic ratio with one caliper (at about 28:1 for the Grimeca or AP caliper). With two calipers it would give about 56:1. Whatever the opposite of 'wooden' is, that's what an 11mm master cylinder would be with twin disks. It would be scary!
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