RF brake options

Mark Worthington · 05-10-04, 01:32 PM

Hello all. I was finishing up some brake line plumbing last night and I did it again...I galled the crap out of the left rear caliper when I tightened up the banjo bolt. It felt a little weird and I was thinking about running a tap into the hole but I was afraid of getting metal slivers inside the caliper. So it seems my options are (1) repair the caliper; (2) get a new caliper; or (3) upgrade the brake system.

Let's start with option #1: can the caliper be repaired? I'm afraid a helicoil may leak under brake-system pressure.

Now for option 2: can someone tell me what car the rear brake calipers are from? Are there parts available in the US or would I need to get a new caliper from Roaring Forties? I prefer not to wait too long, as I'm ready to pressure test my hydraulic lines and P-clip them permanantly in place if they don't leak.

Regarding option 3, what upgrades ara available? The RF web site mentions a Wilwood option as well as AP. Honestly, I'm not crazy about the brakes as they are and an upgrade was planned. On the other hand, I'm not ready to fork over $2,500 for new brakes yet either. Ideally I'd like to fit Porsche rotors/calipers to the car because you can source that stuff at pretty good prices here in the US. I'd be interested to find out what my options are in this regard.

Hershal Byrd · 05-10-04, 01:59 PM

Hi Mark,
If it was me, I would run a tap through the hole then blow it out with air real good. Put it back together and test it for leaks. The 13" rotors and 4 pot PBR calipers on this car work extremely well. If the car weighed much more I would up grade. It's overkill unless you intend on full competiton.

Hersh [img]/ubbthreads/images/graemlins/smile.gif[/img]

Mark Worthington · 05-10-04, 02:36 PM

Thanks for the reply, Hersh. I'm afraid this puppy is too far gone to let me clean it up with a tap...most of the aluminum threads came out of the hole galled onto the steel threads of the banjo bolt. Do you know what car these brakes come from?

Ron Earp · 05-10-04, 03:29 PM

Drill it over size and use an oversize bolt and banjo. Or, helicoil it. I think the helicoil can take it if you get it properly inserted and installed.

Hershal Byrd · 05-10-04, 09:26 PM

Mark,
Ron is right. I have used heli coils and they work well. However I will find out what this particular caliper is for. I believe it is a C3 or C4 corvette . I just don't know what year.

Hersh [img]/ubbthreads/images/graemlins/smile.gif[/img]

Ron Earp · 05-10-04, 09:46 PM

I want to say C4, but wouldn't bet on my life. Helicoil it, it'll be fine. I've done it a bunch and never had one crap out.

Bill Musarra · 05-10-04, 10:17 PM

If they are C4's then they are 85-87.If you read up on the history of corvette calipers you will find all the weak points of their units. One particular point was the lack of cooling. In the c4s I think that unit added the cooling fins, but lacked the air access for true cooling. Could be wrong as it has been a while since I read up on them. Its one reason I opted not to use the calipers on mine(and the fact they were in a terible state on arrival and would have cost me as much as aftermarket to rebuild).

Bill

dave harris · 05-10-04, 10:19 PM

I have the C4 calipers on my car now (will upgrade later - Bill what did you upgrade to?) so if you need a picture for comparison, let me know - or snap a pic of yours and we can tell if it's from a C4.

cheers

Dan Weilacher · 05-10-04, 10:49 PM

There were different brakes in the C-4 corvettes also. Std model ones and the performance Z-51 brakes. In 1988 (still C4) I think they got bigger rotors and better calipers .
I have seen lots of vettes overwork their brakes, but they weigh 1000lbs more than a GT.You would think they would be more than ample , lap after lap with a good racing pad .

Mark Worthington · 05-10-04, 11:07 PM

Here it is...

Mark Worthington · 05-10-04, 11:23 PM

And here's the buggered threads. I don't know what is is about me and the RF brake system...I've ruined two pieces by improperly tightening fasteners. Other than these two incidents, the last time I broke a fastener by cross threading it was a spark plug and I was 15 years old!

Dan Weilacher · 05-10-04, 11:29 PM

Mark is there a part number(cast or stamped) you can check up on. That looks like a C-4 .
C-3 brakes were 4 pot and weighed a ton (not alum)
Here are a few pics of the vette calipers , 84-87 is same one , and 88 to 96 is another , except for J55 option (havnt found that one. yet)

Dan Weilacher · 05-10-04, 11:30 PM

88 to 96 , yours looks like the earlier one for sure , I checked rock auto, AC brand new, $119. I would put a new one on it, your car is worth it,, that thread is bad , and its worth piece of mind! OOPPs , those are fronts, hang on,, let me find the rears,,LOL here it is, looks the same in the Ecklers corvette online catalog, but you cant always go by that.

Ross Nicol · 05-10-04, 11:36 PM

Mark
That caliper is off a Holden Commodore a General motors car built in Oz,hence your on the right track with corvette but these are on fairly late model cars here.I feel the same as you about brakes, any kind of repair is potentially dangerous.Get a new one from Robert.I went the AP route myself but then mine is a race car.
Regards Ross

Kalun D · 05-11-04, 03:49 AM

I've seen aluminum threads gall no matter what you do. You could helicoil it provided that it's not a flair fitting. I believe you said it was a banjo? A helicoil shouldn't leak because the banjo sealing surface is on the outside face.

Even better than that would be a TIMESERT. We used to pre-emptively install them in the sparkplug threads on our racing go-karts. A timesert actually is an improvement on an aluminum thread making the piece more durable than original.

One caveat though, both these thread repairs are dependent on being able to drill and tap past the bottom of the threads, this may not work if the hole has a shallow bottom.

Mark Worthington · 05-11-04, 09:06 AM

Thanks for the replies. Last night it occurred to me that a helicoil should be OK because the threads aren't doing the sealing...just as Kalun pointed out. I'll bring it by a machine shop today.

After I git fixed I think I should remove the piston and seal so I can flush out the metal shavings from the interior of the caliper.

Trevor Booth · 05-11-04, 09:35 AM

Dismantle the caliper, fit a timesert they are satisfactory for this purpose. Save up your money and put suitable double sided calipers on. IMHO Single sided calipers are not the best if you want good brakes

Mark Worthington · 05-11-04, 01:55 PM

After much screwing around this morning I've ordered a Time-Sert kit and a new banjo bolt for a C4 Corvette. It is a rather unusual thread, M10 x 1.0mm, and my local auto machine shop didn't have heli-coils or even a M10x1 die (to clean up the old bolt). So rather than pay him to buy the tool, I'll do it my self. The Heli-coil kit was about the same cost as the Time-Sert kit.

I tried to find an early ('84-'87) C4 caliper to look at to compare mine to but couldn't locate any nearby. That picture looks close to mine, but it is definitely different (extra cooling fin, and I think the boss for the bleed valve is configured differently. I also couldn't find out what the piston size was on the C4 rear calipers.

I'm sure the standard RF brakes will be fine, especially the 4-pots up front, but I think my GT40 with its drivetrain over big, fat 315 tires deserves better rear brakes than the single-pot rear calipers that are in the base kit. I will indeed save my money and put some better brakes on the car, but no need to upgrade right now.

Robert Logan · 05-12-04, 02:39 AM

Mark,

The calliper is NOT repeat NOT from a Commodore.

As I said earlier, send it back to Roaring Forties and we will repair . replace Free Of Charge. I can not offer any MORE than that. This is a SAFETY item , I want it right, please send back to Australia.

Robert

Mark Worthington · 05-12-04, 10:50 AM

Thanks for your kind offer Robert. But no worries, she'll be right. I'm sure a 15-mm-long Time-Sert will suffice. I'm rather anxious to test my hydraulic system and move on with the build, and prefer not to dely this task while we ship parts back and forth halfway around the globe.

That said, I am sending you a care package via Hershal which you should receive at Carlisle. [img]/ubbthreads/images/graemlins/smile.gif[/img] I am unable to attend this year, but here's hoping that it's not as soggy there as it was last year.

Finally, it would be helpful if you could let us know what car these calipers are from. It can be very time consuming to track this information down by trying to compare them to known parts, rooting for information on Corvette caliper piston size, etc. This information would also be helpful in the event that I wanted to order some replacement or performance brake pads.