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GT Disk calipers
https://delcohacking.net/forums/viewtopic.php?f=35&t=1870		 Page 1 of 1
Author:  Glenn [ Mon Apr 16, 2012 12:14 am ]
Post subject:  GT Disk calipers
We all know that GT caliper kits and parts are near impoosible to find.

I don't have this part but it looks similar to the GT. What is GT caliper piston size ?
Uses a solid disk too.

This one is 54mm piston size (~2 .125")and from Triumph GT6. There are a couple of verisons with metric or imperial fittings. Mount spacing might vary too. Don't know what it is.

While certainly not common here in Oz, seems they are easy to buy in the UK.
Would be interesting to compare to GT in the flesh so to speak.

glenn

Attachments:
159027 GT6 metric version.jpg
159027 GT6 metric version.jpg [ 11.46 KiB | Viewed 15947 times ]
Author:  Glenn [ Mon Apr 16, 2012 1:13 am ]
Post subject:  Re: GT Disk calipers
another shot

Attachments:
307977R GT6 triumph looks similar.jpg
307977R GT6 triumph looks similar.jpg [ 29.16 KiB | Viewed 15943 times ]
Author:  JT191 [ Mon Apr 16, 2012 1:29 am ]
Post subject:  Re: GT Disk calipers
Glenn wrote:
What is GT caliper piston size ?


viewtopic.php?f=40&t=336&p=3631&hilit=sumitomo#p1964

Re: Dunlop Sumitomo Brake Calipers
Quote:
Bad news on interchangeability. The Datsun Fairlady Roadster calipers are 2 1/8 inch piston size. The Bellett GT calipers are 2 1/4 inch piston size. That 1/8 inch larger size difference might have made a big difference in marketing 40 years ago ("Our Bellett has bigger brakes than their Fairlady..."), but it puts a dead end on using the readily available Fairlady caliper parts.
Author:  Glenn [ Mon Apr 16, 2012 2:14 am ]
Post subject:  Re: GT Disk calipers
I was wondering if this whole caliper could be fitted instead.

I am no brake guru though so not sure what effect this would have with smaller piston size. Presumably more pressure needed. Pads might a be a bit bigger than GT's though. Assume the donor is a little heavier car also.

master cyl size etc of the GT6 is as below...

glenn

Attachments:
Triumph GT6 twin spot calipers 16P etc 54mm d pistons.jpg
Triumph GT6 twin spot calipers 16P etc 54mm d pistons.jpg [ 63.81 KiB | Viewed 15938 times ]
GT6 master cyl sizes.jpg
GT6 master cyl sizes.jpg [ 66.06 KiB | Viewed 15938 times ]
Author:  JT191 [ Mon Apr 16, 2012 1:37 pm ]
Post subject:  Re: GT Disk calipers
Glenn wrote:
I was wondering if this whole caliper could be fitted instead.


The previous thread was more about finding another car with 2 1/4 inch caliper pistons for donor rebuild parts. But the difference in the size of the piston remains a problem if the plan is to substitute the entire caliper.

It has to do with the fluid capacity. Assuming the original brake system worked well/safely when new, they put some thought into sizing the pieces. The master cylinder would have been chosen to apply adequate capacity, and the front caliper and rear wheel cylinder matched to the capacity, and the fronts would be a ratio larger than the back in order to balance the braking force so the car stops in a straight line, doesn't spin, and makes maximum use of the rear brakes to slow the car down.

The normal issue is someone wants to use a huge caliper on the front, with the factory master cylinder, and it takes three pumps on the brake pedal before the front caliper will start pushing the pads against the rotor.

But moving to a smaller capacity caliper causes its own problems. The front brakes engage earlier. The rear brakes do less of the stopping work, or no work at all, and stopping distance increases. The front disks wear faster. The pedal catches higher.

2 1/4 was a big piston size in the 1960's. And for whatever reason, it's bigger than most brakes today, also.
Author:  Glenn [ Mon Apr 16, 2012 10:16 pm ]
Post subject:  Re: GT Disk calipers
What you say is true but many have fitted the galant brake calipers which are single piston type. I don't know what Diameter but obviously overall area is lower than 2 x GT pistons.
Author:  JT191 [ Tue Apr 17, 2012 12:46 am ]
Post subject:  Re: GT Disk calipers
Glenn wrote:
What you say is true but many have fitted the galant brake calipers which are single piston type. I don't know what Diameter but obviously overall area is lower than 2 x GT pistons.


But with a single piston caliper, the piston has to move twice as far because it has to push the pad on the near side, and also to pull the pad on the far side.
Author:  adrianglock [ Mon Sep 03, 2012 2:51 pm ]
Post subject:  Re: GT Disk calipers
I'm hoping that some companies will reproduce some parts for the GT so I don't need to modify by brake system! It's really hard to find some stuff for the car since it is very rare and hard to find.
Author:  gt orphanage [ Mon Sep 03, 2012 5:07 pm ]
Post subject:  Re: GT Disk calipers
I send mine to bhss and the reco them for me in around three day's. The reciept refers the boots are from a jag :?: The last set were in bad condition as the better ones were used in other cars they machined the pistons down and chromed them as they were badly pitted with new hoses it cost around $600 for the pair.
Author:  gricey [ Mon Sep 03, 2012 8:30 pm ]
Post subject:  Re: GT Disk calipers
Wonder what they do in Japan . There seems to be a lot of gt belletts there. Greg you should get your repair guys to give you the info of what bits they use. I have got one new caliper and 2 new pistons so I probably should get one done up. What about roaters . I have just used my last two spares . Gricey
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