GT6 Brakes

[realdj]

I install GT6 brakes on my Spit. Having trouble sorting out the different drums. What is the difference in the drum depth of the inch and a quarter ones and the inch and a halt drums.Or are they the same. The ones I have are 1 1/2 deep. The shoes are 1 1/4. Any info would be helpful. Thanks Don

[Pete Lewis]

i would expect the standoff of the hub/backplate is changed to suit a wider drum 

the hubs are the same unless the offset is in drum nave 

Pete

[NonMember]

The wider drums were only used on self-adjusting brakes. The earlier manual-adjusted backplate won't take them, I don't think.

Incidentally, I also uprated my Spitfire to GT6 brakes but only at the front. I was advised (possibly by John Kipping, it was that long ago that I did it) that there's no need to uprate the rears.

[dougbgt6]

Ha! Rob got there first!

Don,

The 1.5" were fitted to the late GT6 MK3 from Feb 1973 on, The car only ran another 9 or 10 months so spares are difficult to find. It also had larger brake cylinders which are rare as hens teeth. The backplate is different to accommodate the auto brake adjuster, which doesn't work too well, (not at all on some!) The late MK3 had swing spring similar to the spitfire, the earlier MK3 had rotoflex so the drive shafts are very different and I'm not sure the 1.5" drum is going to fit.

There's no benefit in having 1.25" shoes in 1.5" drums and like Rob I would leave the rear end Spitfire original.

Doug

[Clive]

33 minutes ago, NonMember said:

The wider drums were only used on self-adjusting brakes. The earlier manual-adjusted backplate won't take them, I don't think.

Incidentally, I also uprated my Spitfire to GT6 brakes but only at the front. I was advised (possibly by John Kipping, it was that long ago that I did it) that there's no need to uprate the rears.

I ran my 2.5 vitesse with the correct front brakes, but when I built the car I couldn't get vitesse/GT6 rears, so used spitfire/herald rears. Initially meant to be temporary, but I soon discovered the rears were more than adequate, and could be locked up when provoked. If you can lock the brakes, you don't need bigger/better.

[Nick Jones]

1 hour ago, clive said:

If you can lock the brakes, you don't need bigger/better.

Unless you can set them on fire……😳

[Clive]

3 hours ago, Nick Jones said:

Unless you can set them on fire……😳

Fair point! But I never did that either.

I guess vented are a sensible upgrade for car driven hard. They work for me, when stag brakes are giving up the ghost and smoking like a chimney, my vented discs were fine. Warm, but fine. 

[realdj]

I just wanted to know the difference in the depth of the drums between the two.  Seems like no one can tell me this. I even emailed Rimmer to see if they could measure  some stock drums for me and got a reply like a politician every thing I all ready know but no answer to my question.

[Colin Lindsay]

There seems a lot of confusion about these even from suppliers.

I've just checked to find that the later drums from KE20001 onwards are 8" by 1.5 inches deep. Part number is GDB101.

Early drums are being listed as 8 inches by 1.25 deep. Part number 203077 (although I have found one seller selling 8.5 inch drums).

So: 1.25 or 1 1/4 inches difference.

[dougbgt6]

1 hour ago, Colin Lindsay said:

There seems a lot of confusion about these even from suppliers.

I've just checked to find that the later drums from KE20001 onwards are 8" by 1.5 inches deep. Part number is GDB101.

Early drums are being listed as 8 inches by 1.25 deep. Part number 203077 (although I have found one seller selling 8.5 inch drums).

So: 1.25 or 1 1/4 inches difference.

Uh?

db

[Colin Lindsay]

47 minutes ago, dougbgt6 said:

Uh?

db

Have I said something incorrect?

Last post by realdj says he wants to know the difference in depth between the two drums, and no-one will tell him. 

One is 1.25 and the other 1.5, unless depth means something different to what I thought it did?

 

[NonMember]

13 minutes ago, Colin Lindsay said:

Have I said something incorrect?

 

2 hours ago, Colin Lindsay said:

So: 1.25 or 1 1/4 inches difference.

It's only 1/4" of *difference*

[dougbgt6]

1.25"  IS 1 1/4" 

It's this foreign metrification has you confused.

db

[Colin Lindsay]

Well whats an inch between friends? Nice to see someone's keeping an eye on me.

As long as realdj ignores me, he'll be ok.