930 calipers (for '86 carrera) have arrived! what other parts do i need?

dickster · 08:15 AM

wow, they're HUGE

(i'll post pics soon as)

i know i need to get the rears modified, and i know i need rotors.

but what else??

do i really need to change the mc, and bias valve?

is anyone running 930 brakes on a carrera with the stock mc/valve setup??

can't wait to fit these, they're twice the size of the std brakes

(btw-paid £250. they seem to be in good cond. no rust etc. some of the pistons seem tight, but i'll give them a good spray and we'll see - hope not to rebuild them now)

addictionMS · addictionMS's Garage

you really will need the 23mm master, I was just reading Carrol Smiths book drive to win last night and the subject of brakes came up, he states that a brake pedal should have a little pedal movement as possible, and modulation of the brakes sould be based on pressure not movement. I cansee that he is correct, the more the pedal moves the harder it will be to modulate, a pedal that does not move but is pressure sensitive will allow better modulation. All fighter jet joy sticks are pressure sensitive not motion sensitive.

so the 19mm you have will give you a lot of pedal movement, it needs to travel further to fill the extra pistons than the 23mm.

if you can't find one, I have one from a 1988 930 I did not use because I have the earlier style chassis, and the master is under the footwell. Shipping to the UK will not be worth it unless you totally strike out.

Jim

GeorgeM · GeorgeM's Garage

Nice work, Dickster. You practically stole those things.

I was told I would need the 23mm MC as well. You should be able to get one for around $150. I have seen a few new ones on Ebay with no reserve go for less than $100.

Nobody has said anything to me about the bias valve. If it does need to be changed or removed I'll need to know that as well.

You'll need new hard lines that run from the rubber lines to the calipers (you can buy straight metric line and shape your own). It's not a bad time to change those rubber lines while you're at it if they're original. I got the Kevlar reinforced/Stainless braided type.

If they are the older style with the big cooling fins, you may have to mill down the fins to fit them under your 15in wheels. The later models had shorter fins that might fit without milling.

I'm sure you'll get yours done before I will, so let us know how it goes.

Glasgow 911SC · Glasgow 911SC's Garage

here's what Thom (widebody) did to fit them on his car. His Turbo flares make it a bit easier though (I believe!?).
£250 is a great price! Where did you get them from? I've got a chance to buy 993 brakes at a good price but I'm not sure whats required to fit them, and am worried the price would get too much.

dickster · 07-10-2002, 11:38 AM

jim

thanks for the advice and offer. i'll see what i can find

george

LOL, i did, threw £250 at him and ran off down the road

i think they're the later ones then, wasn't aware of difference, i'll post pics soon (clean 'em up first

)

i got them at jm autos in uk. i was looking for an alignment shop and came accross them on their website - so i couldn't resist. they were up for £400 with new front rotors which were no good to me so i knocked him down. the guy had upgraded his turbo.

glasgow,

do some research. i wasn't going to do this but for the right money its gotta be worth it. right??

Bill Verburg · Bill Verburg's Garage

I can't remember what year you car is but the 19mm non boosted mc will work as will the 20.6mm boosted mc and of course the 23mm 930 boosted unit as well. Jim has raised a valid point the bigger the mc the higher and firmer the pedal will be and the easier to modulate. Boosting takes all of the leg work out of it. Its a good thing I run

and ride my bicyle

so much!

You do not want any p/v with the 930 brakes. If you have an 84 up remove it!

The 911 rear splash plate is too small for the 309mm 930 rear rotor. Remove and discard or replace with a 930 piece. The front shield is small and looks odd with the big rotors but will work fine, or again you may discard it. If discarded it will radiate better but as the air flows outward from the center it won't help convective cooling at all.

On a personal note I would really appreciate it if you could weigh and post the following info; caliper weight f/r, front rotor wt alone front rotor weight with hat bolted on, rear rotor weight. And pics are always nice!!

dickster · 07-10-2002, 11:45 AM

bill

mines an '86. guess i remove the valve then?.

you reading george?

p/v - whats that stand for?

i'll let you know the weights as soon as, the rotor will take a while - i haven't got 'em yet!

GeorgeM · GeorgeM's Garage

Got it.

P/V = proportioning valve.

Bill,
I think that's mounted on the firewall in the back, right?
Is it a pain to remove? Does it require re-plumbing of any of the lines?

Wish I could just go out to the garage and look for myself.

No Porsches in the garage out here, just Grumman, Boeing and Lockheed.

addictionMS · addictionMS's Garage

one other thing to start looking for, I needed 1/8 inch spacers in the rear so my 16 Fuchs would clear. Not sure if yo need them in the front, I have a full 930 front so if they were needed they are built in on mine.

Jim

dean · 07-10-2002, 06:42 PM

I had to mill the cooling fins off front and rear. Up front I also needed .090" wheel spacers that I made. I don't know what rotor you are going to run but you might need some hats.
Have fun

dickster · 07-10-2002, 11:07 PM

bill

the calipers (without pads) weigh approx 3.75 kilos or 8.26 Ibs ea.

theres no front/rear - they're all the same?? (they look the same anyhow!)

i'm running 15" wheels - do i need spacers??

dean · 07-11-2002, 03:28 AM

You might need spacers. I think the fit is very close so some cars need spacers here or there. I am running 7&8x16 Fuchs and I needed them up front. The rears are very tight also but I didn't need them there. It is a good idea to get new allen head bolts and you will have to modify a wrench to install the rear bolts

Glasgow 911SC · Glasgow 911SC's Garage

Richard,
How about a tech article / idiot guide for this. It seems just about everybody wants todo this but don't fully understand whats involved. You could settle the questions once and for all!

dean · 07-11-2002, 03:49 AM

Thom did a nice writeup of it with pics.

dickster · 07-11-2002, 04:15 AM

Glasgow

i'll put something together. it'll take a while for me to get the parts together though - so be patient!

thom's write up was great. it must have doubled the install time putting the pics and text together.

however, thom's car is a wide body(?) so he didn't have all the installation issues that us with narrow body cars face

actually, i guess its just the front rotor thats more straightforward on wide bodies.

there is also the issue of the m/c and p/v.

i know what glasgow means though. i've read load of threads and still don't know exactly whats involved. another problem is there's so many variations with different model years.

Bill Verburg · Bill Verburg's Garage

There is a difference between front and rear besides pistons, 38/38 go on the front and 30/30 go on the back. the bridges are slightly different also.

Thanks for the weight info.

On the 84-89 the p/v is the round cannister looking thing coming off the left side of the m/c(looking towards the rear of the car). Yes, when using the 930 brakes remove the p/v. Though you might want to try it w if your taste is for more front bias, in extreme braking where there is a lot of forward weight transfer front bias is increasingly desireable. The 930 calipers w/o p/v have a hbr of ~1.6, I use ~1.7 on my car, some people like even higher. It's a very personal issue.

dickster · 07-11-2002, 06:49 AM

Quote:

There is a difference between front and rear besides pistons, 38/38 go on the front and 30/30 go on the back. the bridges are slightly different also.

i'm glad you're around bill, i wouldn't have noticed they were different

where do i find the numbers?

i can find, almost hidden, 25 on two calipers and 38 on the other two?

all other numbers appear to be the same.

Bill Verburg · Bill Verburg's Garage

Those #s may be casting #s or ?. All 930 fronts were 38/38 and all 930 rears were 30/30. You should be able to see the piston faces to tell. Also its a good idea to clean and exercise all the pistons while its convenient, when the pistons are hyperextended they can be measured witha mic.

dickster · 08-09-2002, 09:13 AM

here they are:

i have tried cleaning with brake cleaner but its tough. i figure if i use another method i'm gonna have to strip them. i already tried white spirit on one, and am wondering what effect thats had on the rubber seals.

any ideas on cleaning?

should i strip? one of the seals is out of shape, so that will need fixing.

whats the best way to get the pistons out? and do they have to go back in the same bores?

help appreciated guys.

dean · 08-09-2002, 12:34 PM

I just cleaned mine with brake clean and shot them with hi temp flat black paint. If I had to rebuild them I might powder coat them.
You can try to use air pressure to get the pistons out. Put a piece of wood between so the piston doesn't fly out. I don't think it matters if you mix the piston up, but it won't hurt not too.

Have fun, they look pissa when they are done.