My writeup on disc brake conversion

[drooartz]

Okay, I *finally* got around to working on the writeup from my disc brake conversion on the Tunebug. I meant to finish this at the time, but things got a bit out of hand... so two years later I'm finally sorting this out. I'd like to make this useful for folks who are considering doing the conversion.

If you have a second, please give it a read through and let me know what needs to be fixed. After two years I've forgotten much of the detail, and would really like to add it back in.

https://www.drooartz.com/index.php?page=61

 

[Rut]

Drew, that will help me a lot! I don't know enough about the tech details, but your explanation flows well and makes sense to me. Thanks for taking the time to put this together.
Rut

 

[Trevor Jessie]

Very nice, maybe a reminder to put the calipers on the correct side (bleeder at the top). Also a note about felt washers on the E-brake yokes to minimize rattles.

 

[tdskip]

Thanks Drew

 

[drooartz]

I've added a bit on making sure the calipers are on the proper side, bleeders up.

Not sure what you mean about the felt washers on the emergency brake (yoke?), Trevor. Looks like something I didn't do that I should do. Could you explain a bit more?

 

[BWillis]

WOW, this is a REALLY good tip. I had a few rattles myself until putting a felt washer on my e-brake rods....

 

[Jim_Gruber]

Drew, really nice write up. I sent this to a friend going through this exact conversion right now and saved this to my big file of useful Spridget Info. Hopefully if I can close this deal...I may have the opportunity to use this.

 

[Gerard]

Okay, I *finally* got around to working on the writeup from my disc brake conversion on the Tunebug. I meant to finish this at the time, but things got a bit out of hand... so two years later I'm finally sorting this out. I'd like to make this useful for folks who are considering doing the conversion.

If you have a second, please give it a read through and let me know what needs to be fixed. After two years I've forgotten much of the detail, and would really like to add it back in.

https://www.drooartz.com/index.php?page=61

Good, concise information Drew.

I'm curious what year car you sourced your rear brakes as I've never run into the short brake rod issue. I think that is only an issue when sourced from later cars as they did make some brake rod modifications by the time the rubber bumper cars came out, but possibly sooner. I did mine with a '69 donor and no modification was necessary.

Thanks too for the mention and the links. I'll just add that the caliper rebuilding can be done through the same service/same time as the master cylinder. For that matter, <span style="font-style: italic"><span style="font-weight: bold">any and all</span></span> hydraulic services can be handled by Sierra. Return shipping is provided free in the lower 48.

 

[drooartz]

The donor car was a 1974 Midget. Only one I've ever done, so no idea as to how common the rear brake rod issue is.

 

[bugedd]

Question, why rebore the master to 3/4? Stock is 7/8, right? So the bore needs to be smaller??

 

[drooartz]

Question, why rebore the master to 3/4? Stock is 7/8, right? So the bore needs to be smaller??

They switched to a 3/4 master cylinder when they switched to disc brakes with the MK2 Sprite/MK1 Midget. It's not strictly necessary, but would be the correct bore for discs.

Gerard's site has a good description:
https://gerardsgarage.com/Garage/Tech/DbrakeUg.htm

 

[Gerard]

With regard to brakes, pedal effort will be reduced by roughly 33% by using the 3/4" MC. On the clutch side, you will experience less "twitchiness" in the clutch and better control.

 

[bugedd]

What if you are still using the stock rear brakes, but with front disc? Still rebore it to 3/4?

 

[Gerard]

What if you are still using the stock rear brakes, but with front disc? Still rebore it to 3/4?

Yes.

 

[bugedd]

Guess thats on my list of next winter projects