GT 380 Front Brake Modification

[BlueSmoked]

Hi there!

I search on the web about what the specification would be of the GT380 front brakes. Ours has disc brakes I think from '75 not sure.

I saw that pistons in caliper could be 38mm. And that there are two mastercylinder diameters 14 and 16mm Not sure which one on our bike. And size of the banjo bolt of the masters I don't know.

Last year I modified the brakes on my RD250 (also has disc at he rear) to 13mm Brembo units. Orgininal it had a caliper piston - master cylinder area ratio of 18,3 with 5/8" masters. And modified to 13mm masters it changes ratio to 27,3. Which is on the spot of two finger braking and world difference on feeling braking other than " wood" feeling.

So if GT has 2x 38 pistons 16mm master -> ratio 11 ; 14mm master -> ratio 15. Both should feel like "wood" no whether state of seals and wear calipers and masters.

So I thinked to look for 11 mm masters that should give a ratio of 24 ish. Which is on the "sweet spot" between 27-20 ratio which 23 is less line and caliper flex.

http://www.vintagebrake.com/mastercylinder.htm Something to read!

[Alan H]

Does it have twin or single disc front wheel? If twin, you need a master cylinder with 'D' (for dual) underneath.