c4 calipers for "big brakes" ?

[fatbloke-dim]

I have a '93 'vert . It has 13" discs , but I don't know which calipers are fitted . The guy who sold me the car did the switch , from 12" discs , but I don't think he changed the calipers , they are more than likely the originals . Is there any way to identify which caliper variant may be fitted if the big brake option has been fitted ? It may be the parts that constitute the J-55 option , but the car was'nt built as such . If it be any help , the front calipers are 2-piston type , I can't see too well without wheel removal if there are any pistons opposing these 2 , thus making for a 4-piston caliper . I want to amass the parts I'll likely need to swop put the 4 calipers , as there is a bit of drag when warm . I was thinking of going for stainless sleeved ones , so ,to that end , any ideas who offers the best deal ? I would rather try to dodge hefty core charges , as I 'd like to keep them as spares , or get them sleeved locally . I have no qualms about importing a replacement set fro the U.S. to get me fixed up in the first instance - it'll be the cheapest option whilst leaving me at the disadvantage of being off the road as little as poss . Any thoughts ,folks ?
Nige.

 

[Hib Halverson]

As I recall, factory "big brake" (J55) system was only front rotors, pads and mounting brackets. Base and J55 for 88-93, 94/95 all and non GS 96 used the same calipers.

You can't put 65-82 four piston calipers on a C4. Besides....who'd want to.

If you want a four-pot, fixed caliper, you'll have to go to an expensive aftermarket conversion along with larger wheels. Your talking serious dollars...er...pounds for that.

 

[fatbloke-dim]

Hi ,Hib....

Thanks for that lightning quick response , mate ! As for the 4-pots ,I don't wish to fit 'em if they are a departure from stock , it's just that I can see there at least 2 pistons by squinting thru' the wheels , I did'nt know if the pistons were single-acting or opposed . I have seen , however on Muskegon Brake's webthing , 2 types of front caliper , one billed as "H.D." , the only difference I can see between 'em is that the H.D. one has some finned pert on the housing over the piston section that "standard" ones don't have . EDIT!!! I've just looked at Zip's site ,and it looks like the finned bit applies to both caliper types ! I can't find an image of the standard and H.D. caliper taken from the same angle ,so cannot directly compare them . I don't know if the previous owner achieved the conversion by changing the caliper bracket or the caliper . so.......is there any distinguishing feature I could use to identify which caliper I actually have ? Would I be correct in assuming that the 13" discs won't fit with these "standard" calipers ? I really ought to get the car jacked up and a wheel off ,but it's raining copiously ( again ) , and my trolley jack is deep buried under heaps of what my missus refers to as "crap" in my shed ! Wot she know ,eh ?!:L

Another thought .....the car has a different brake bias spring fitted to give a little more emphasis on the front - are these known to cause any drag issues ? It's not bad , but the car does'nt feel as "free" as when the brakes are cold . The car had a master cylinder cap with a square hole cut into it for some reason , and this only had a bit of electrical tape over it , so I figure that moisure is likely doing misdeeds in there , so it may be pointless doing a fluid change if corrosion has a hold . If I can get some calipers brought back by folks I know are visiting America ,it will be cost-effective to just swop 'em out for stainless sleeved ones . But for now ,I 'm just weishing the interminably cold , lousy weather would give me a sporting chance of getting some 'Vette action ! No wonder we Limeys are preoccupied with the weather ...............:eyerole

 

[Hib Halverson]

Front calipers were all two-piston sliding caliper.

In my experience, aftermarket "brake bias" springs typically bias braking more towards the rear not more towards the front.

I incorrectly stated in my earlier post that all the calipers are the same. I was wrong on that. It's been a while since I've had to discuss all the differences between base and J55. On J55 the front rotors are 330-mm base brakes were 305. The aftermarket sometimes calls those FE7 or HD brakes.

You need to get the car up in the air, get the front wheels off and measure the front brake discs.

If you have a master with a hole cut in the top, obviously some moron had been working on the car. Order a new cap (PN DB-761) from my friends at Zip. Absolutely do a brake fluid change and soon. Flush then bleed the brakes per the factory service manual. It's much easier to pressure bleed the system. Old brake fluid accelerates the corrosion process. When you find out how much the ABS EBTCM costs, you'll have kittens. Best to flush every two years.

If your car has the big front rotors, and you're going to change calipers, you need Zip PN DB-843.

If you change pads before you flush the system, open the caliper bleeder before retracting the pistons. That prevents brake fluid from being forced backwards though the ABS modulator valve.

By the way, over here in the "colonies" we don't quite speak the King's English so...WTF is a "trolley jack".

 

[fatbloke-dim]

Hello again, Hib.....

Sorry I'm a bit slow on the uptake here with replies ,but the weather just got into overdrive ,and with temps in the low 80's ,and one of my fave shows being on the weekend close to the 4th of July , and very local to me , I've been busy getting some 'Vetting done , in between working a few shifts where I can't get to the internet for a while . A trolley jack ,hmmmmmm.....I can usually speak American , but I'm stumped at what you may call 'em ,but it's nothing fancy , just a regular roll-under , pump it up 4-wheeled jack . As opposed to a bottle-jack . I'd "kind of" decided my days of lifting cars and doing my own work on 'em were over , but it seems I 'll have to get active and pull the wheels . I know there have been new discs - rotors - fitted , and they are 13 -inchers , but I'm not sure if the calipers have been changed ,or whether you can use base brake calipers with just a change of bracket. I've e-mail the fellow who did the change but not had a reply yet . I've already changed the reservoir cap for a new one ,and put a new gasket on there , which I picked up on a 'Vegas trip in April , but the damage is most likely done .My plan was to get my brother to bring me some calipers home from Florida next month , seeing as I will most likely never get to the "Colonies" again ,due to Her Ladyship's health deteriorating such that she can no longer travel . To say I'm disappointed is putting it mildly ,indeed . Stii l, we have each other ,and 39 Stateside trips means we have'nt tried ,eh ? Woulda been nice to get 40 plus!!

Are there ant distinguishing marks between the different caliper types ? I have a week off next week , so should get something done , if the weather does'nt persuade me to "get 'Vettin' " !otfl

 

[Hib Halverson]

We call 'em "floor jacks".

If you have 13" brake discs then you have the calipers to fit those rotors.

To my knowledge there are only two calipers which fit 88-up C4s with the larger front brake discs.
88-94 w HD brakes (came with Z51, Z07 or ZR1)
95-96 all except 96 Grand Sport
96-Grand Sport

The 96 GS calipers are said to be stronger across the bridge than the standard 88-96 front caliper.

 

[fatbloke-dim]

O.K. , then....

will check which disc size is on the car , and arrange calipers to suit . Are there any recommendations for what bits of mounting hardware may be better to swop out at the same time ? Thinking of slide pins/mounting pins ,bolts , clips , hose washers etc. Anyone know if anyone does a full kit for same , so that nothing may be overlooked ? I'd hate to start the job and find myself stalled due to missing a minor part , especially if it means waiting for more international shipping . I hate when that happens.........

 

[fatbloke-dim]

Right-o !

Ascertained I have 12" discs, and calipers ordered , along with a new set of Hawk pads . Car is going in on Weds for oil and brake fluid change , but the calipers won't arrive in timee , unfortunately . Never mind , the fluid flush can't hurt , and the calipers will be in my sweaty palms soon enough . Car is running much strong just now with the regular exercise it's been getting !