What is needed for a 'big brake' upgrade; how well does it work?

[twas_brillig]

I've seen references to upgrading the front brakes of a Spridget with MGB calipers and Triumph Spitfire (?) rotors, but was unable to find any real explanatory information on the conversion, in either this forum or elsewhere.
At the moment, we're converting our BE to the later front discs and appropriate rear drums etc., and I'm dreaming of using Joel Young's (of Creative Spridgets) rear disc conversion for the future.
To my eye, it looks impossible to increase the existing front rotor diameter as it would contact the steering arm and shock absorber connection.
So - does it work? how does it work? what's required? what do you gain (rotor diameter change; brake pad area change; impact on stopping distance).
Thanks, as always. Doug

 

[Jim_Gruber]

Lot's of $, steering arm needs ground down. Lots of work for IMHO street use. You may also need to go to 14" wheels for a larger rotor size.

 

[JPSmit]

Lot's of $, steering arm needs ground down. Lots of work for IMHO street use. You may also need to go to 14" wheels for a larger rotor size.

+1 If you are just going to drive it don't overcomplicate things. FWIW while I have a couple of regrets of things I should have done while the car was apart - notably 5 speed and notch for twin SU's, I also realize every "good idea" I or someone else had was another $1000 and six months, so, comes a point where you just get it done and drive!

 

[SaxMan]

Or, as it took me several times to learn: When you try to make a solution for things that aren't problems, you often end up making a bigger problems for yourself.

 

[Jim_Gruber]

Great minds thinking alike. The voice of experience.

 

[Gerard]

I installed this setup once for someone who wanted it. It was a poor fit and required a lot of grinding and adjustments. It doesn't come as a complete kit (that I have found), and requires buying many parts separately. I'd never do it again, certainly not on my own car. I didn't find the improvement very significant, especially not as much as big brake kits I've installed on the Morris Minor.

I have not tried Joel's setup yet myself, but have heard good things about it and would be my first choice for such a conversion. It's also possible to use the Nissan components on the front, though it requires a special bracket.

 

[JPSmit]

Just remembered, Back in the day Classic Motorsports magazine restored a Midget and put this kit on the car - MGB Rotor & Spitfire calipers - they got the adapter from the Winners Circle - https://spridget.com/ - this was more than a decade ago so I have no idea if they still make it. I do have a scan of the article - which is all about rebuilding the calipers and nothing about the kit, but, PM me your email and I can send it on.

 

[twas_brillig]

Sounds like a good idea not to consider this particular potential 'good idea'. We're putting Spridget discs on the one BE; need to get used to non-power assist drum braking on the running one. And not worry about trying to upgrade the Spridget disc system. Thanks all, Doug

 

[Gerard]

If you want that to improve, you'll want my master cylinder conversion. It will reduce pedal effort by 33%. You could either send your core to be redone or maybe, considering cost of shipping from Canada, you might want to consider buying one outright that I already have built and ready to go.

https://gerardsgarage.com/Garage/Tech/DbrakeUg.htm

Sounds like a good idea not to consider this particular potential 'good idea'. We're putting Spridget discs on the one BE; need to get used to non-power assist drum braking on the running one. And not worry about trying to upgrade the Spridget disc system. Thanks all, Doug

 

[twas_brillig]

We have a running (as of yesterday) BE with a 948 and standard drum brakes and the stock master cylinder - it's the one I was remarking on having to get familiar with the braking effort versus stopping distances. The one we're assembling has the upgraded front discs and rear drums, and the master cylinder was one of the last to be rebuilt & sleeved by Sierra Specialties a few years ago, with the bores modified to match the Rivergate clutch system and the Spridget front discs. I expect that I'll be talking to you if/when we upgrade the drum/drum yellow BE to disc/drums. Thanks again - and thanks for your thoughts on the rocker shaft locator screw. Doug

 

[Gerard]

Excellent!

I don't know if you are aware of it, but I was the impetus for this conversion. It was always a collaboration with Sierra, beginning in 2006; what you have is one one and the same.

We have a running (as of yesterday) BE with a 948 and standard drum brakes and the stock master cylinder - it's the one I was remarking on having to get familiar with the braking effort versus stopping distances. The one we're assembling has the upgraded front discs and rear drums, and the master cylinder was one of the last to be rebuilt & sleeved by Sierra Specialties a few years ago, with the bores modified to match the Rivergate clutch system and the Spridget front discs. I expect that I'll be talking to you if/when we upgrade the drum/drum yellow BE to disc/drums. Thanks again - and thanks for your thoughts on the rocker shaft locator screw. Doug

 

[twas_brillig]

Dang! Did NOT know that! Congratulatons, and a sincere 'thank-you'! Doug

 

[Gerard]

Dang! Did NOT know that! Congratulatons, and a sincere 'thank-you'! Doug

 

[AHS]

I'm working from memory here, but this was an approved modification in some SCCA production classes. First there is an aluminum spacer that fits tightly over the Spridget hub and has 8 tapped holes in it, because the Spitfire rotor has a much shorter "hat" section and also a different bolt pattern. The spacer is of the correct length to center the rotor in the caliper. Naturally you'll want to make sure the rotor runs flat & true with a dial indicator. Next is the Spitfire disc. Some will clear the MGB caliper without modification, but as I remember it Brembo discs required a very slight cut like .010 around the top edge of the "hat" to clear the inner edge of the caliper. The clamp plate I made to do this on a rotary table is still in my toolbox. Finally there's the MGB caliper, which bolts directly to the Spridget spindle without the need for any spacer. I used to bevel the very bottom edge to get more clearance to the aforementioned cut in the disc hat. Some brands of brake pads also extended a tiny bit beyond the inner diameter of the Spitfire friction surface ID. It's only about 1/8" and pads can be easily trimmed before installation. I believe this all fits without modification of the later small style tie rod ends and steering arms, though clearance to the back of the rotor is very little and race cars run without backing plates. Hope this helps you understand the pieces & challenges.

 

[twas_brillig]

I'm just go back and checking for a couple of items and ran across thread (that I'd started), and I never said 'thanks' to AHS for his contribution and information.
So: Thank-you! Doug