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pitzel

Big brake upgrade differences

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Long story short, my entire strut tower assembly had to be replaced in the middle of nowhere in North Dakota by some hack mechanics with one from a junkyard off of a newer car with the bigger front brakes.  Unfortunately I wasn't able to supervise the repairs. 

They re-used my existing 1992 calipers, rotors, slide-pins, bearings.  But the caliper doesn't really ride properly in the assembly, and only makes about 2/3rds contact with the brake rotor.  And everything is all bound up.

My questions:

1)  Are strut tower assemblies identical and interchangeable between the "small brake" and "big brake" models?  

2)  Could it be possible that the shop kept the 'big brake' bracket, but swapped my small-brake calipers and rotors?  

3)  Would going to a junkyard, finding a "small brake" caliper bracket, and fitting it fix the issue?

Braking-wise, performance is perfectly acceptable, although I think it is burning up pads faster and longer-term it'll probably kill the rotors too.  

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More information is needed,

 

what year is your car?  '92? is the replacement front strut taken from a 94 -96 vehicle?

 

if so the mounting for the calipers are different, the later strut allows an 11" front rotor, the earlier cars (88-93) are fitted with 10.5" rotors. The caliper bracket & the calipers are the same, the only difference is where the later struts stamped welded bracket flange locates the caliper bracket to move it further away from the centerline of the rotor/spindle to accommodate the larger rotor dia.

 

If the shop that did this tried to use the 10.5: rotor mounted to the hub where an 11" rotor should be the pads will not be in the proper location on the rotor contact surface.

To correct this you will need to install a proper 11" rotor to that repaired side. This is also going to upset the braking force to the front wheels as well. The smaller 10.5" rotor will not deliver the same amount of braking torque that the 11" rotor will. The larger the diameter of the rotor the greater the braking torque will be. You will need to do the same mod to the other side to equalize the braking torque to both wheels.

 

The shop that did this should've seen that something was visually incorrect when they re-installed the pads & could see that they were out of place.

Edited by 55trucker

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3 hours ago, 55trucker said:

what year is your car?  '92? is the replacement front strut taken from a 94 -96 vehicle?

 

if so the mounting for the calipers are different, the later strut allows an 11" front rotor, the earlier cars (88-93) are fitted with 10.5" rotors. The caliper bracket & the calipers are the same, the only difference is where the later struts stamped welded bracket flange locates the caliper bracket to move it further away from the centerline of the rotor/spindle to accommodate the larger rotor dia. 

 

If the shop that did this tried to use the 10.5: rotor mounted to the hub where an 11" rotor should be the pads will not be in the proper location on the rotor contact surface.

To correct this you will need to install a proper 11" rotor to that repaired side. This is also going to upset the braking force to the front wheels as well. The smaller 10.5" rotor will not deliver the same amount of braking torque that the 11" rotor will. The larger the diameter of the rotor the greater the braking torque will be. You will need to do the same mod to the other side to equalize the braking torque to both wheels.

 

The shop that did this should've seen that something was visually incorrect when they re-installed the pads & could see that they were out of place.

Yup, a 1995-ish strut tower assembly was put in place of the 1992 factory original.  Everything else remained identical.  Of course predictably it doesn't really work properly.

So you're saying that the strut tower, where the holes are drilled, is different between a 1992 and a 1995?  

Darn...  So basically I need to have identical strut towers on both sides.  Which means basically I have to go to a junkyard and pull a strut tower assembly to down-grade my setup to the 1992 caliper bracket positioning?  Or alternatively, upgrade the other side to the 1995-ish spec?  

 

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2 hours ago, Imp558 said:

What led to having to replace the entire assembly? 

Long story short, the spring seat failed catastrophically due to rust on a trip to Minneapolis.   The hacks who worked on it didn't realize that the spring seat could be ordered as a separate part, so they found a 1995-ish wreck, swapped the spring/strut tower/strut assembly, and fitted my existing bearings, caliper bracket, rotor, calipers, etc. to the "new" strut tower and sent me along.   Because it was in small town North Dakota, there wasn't really a lot of good options otherwise. 

I've since gone in and replaced the spring seats on both sides with brand new ones (the other side was pretty bad too, and not far from failure), so I've had the strut towers apart.  But the brake alignment problem with the newer tower has been quite vexing.

 

 

Edited by pitzel

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18 minutes ago, pitzel said:

 

 

Darn...  So basically I need to have identical strut towers on both sides.  Which means basically I have to go to a junkyard and pull a strut tower assembly to down-grade my setup to the 1992 caliper bracket positioning?  Or alternatively, upgrade the other side to the 1995-ish spec?  

 

There's no real sense in going *backwards* on this, the larger rotors will brake better than the smaller ones, so you're looking for the later strut.

 

Reading your last post, this didn't happen just recently?

You've been driving the car this way for some time now?

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58 minutes ago, 55trucker said:

There's no real sense in going *backwards* on this, the larger rotors will brake better than the smaller ones, so you're looking for the later strut.

 

Reading your last post, this didn't happen just recently?

You've been driving the car this way for some time now?

Yeah about 10k miles / 2.5 years ago.  I don't really notice any asymmetry or loss of performance braking-wise, but brake pads that previously had only about 1/3rds wear after 70k miles wore down extremely quickly on that side (and not on the untouched side) only making about 50% contact with the rotor's outer edge.  

It doesn't matter to me whether its an upgrade or not -- I'd just like it to wear the brake pads evenly, and of course, get through an inspection properly.  The 1990s W bodies are starting to become rather scarce at the local pull-a-part, so whether I do the upgrade or it becomes a downgrade would be dependant on what I can actually get on the day I go.  

 

EDIT:  I've been using 'strut tower', but I actually mean "strut knuckle" which I believe is the more appropriate term.  

 

Edited by pitzel

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Any one of the 1st gen W's 94-96 & also the 95 thru 99 Monte Carlo will have the strut you're in need of. I'm inclined to think the later cars would be easier to find than the older cars.

 

I too am looking for the later struts for a brake upgrade to my 91, but it means a trip south of the border to where they still can be had, there are none at all up here.

Edited by 55trucker

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23 minutes ago, 55trucker said:

Any one of the 1st gen W's 94-96 & also the 95 thru 99 Monte Carlo will have the strut you're in need of. I'm inclined to think the later cars would be easier to find than the older cars.

 

I too am looking for the later struts for a brake upgrade to my 91, but it means a trip south of the border to where they still can be had, there are none at all up here.

Yeah its crazy, nothing this old in the GTA when I drove there last year (live in Western Canada).  Too bad you're not closer, we could do a trade, at least for the drivers side.  Well if I junkyard it next spring and end up getting the older one, I could perhaps drop the upgraded old part off for you as I have to drive by there next summer.   Used to be more Luminas than you could shake a stick at in the yard, now they're rare.

Are you absolutely sure the calipers and brackets are the same?  

Edited by pitzel

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Yes I am.......no change in their castings at all

to simply improve on the front braking ability GM just installed a slightly larger rotor. To do that they had to move the caliper outward to relocate it in the appropriate position for the larger rotor.

But really, when this platform 1st arrived there were droves of cars coming back to the dealers with brake issues. My 1st two GP's were no different, the cars would not stop very well in panic situations. The brakes are/were too small (front & rear rotors & rear caliper pistons), the boosters were substandard, there was an 1/8" air gap between the booster & the master cylinder pushrod, the diagonal opposed brake lines at the master sound good in theory but in a practical sense BOTH front calipers need to be driven off the same primary piston not split between the one primary & the secondary as the lines were installed, all tied together make for horrendous brakes.

 

 

Edited by 55trucker

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15 minutes ago, 55trucker said:

both sized rotors were available for the 95-96 years

Yeah I'm gonna have to get the part numbers off of those strut towers and see if I can get to the bottom of it...  Because the donor car didn't seem like a 1996, as I'm pretty sure it still had the 'old' interior.  

I was hoping it was just a different caliper bracket...  Would've saved me a lot of work..  But if the greater offset was implemented by way of the strut tower, then its obvious that the only way to fix the problem would be to make sure that the strut tower matches the rotor.  

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7 hours ago, Imp558 said:

Wait until summer,  I should have my Regal stripped then and you can just send me shipping fees. I'll have them from a 1995 and a 1996.

Ok i'll keep that in mind...  I have to drive from Minneapolis to Albany sometime over the summer or early fall, so picking them up might be a possibility too...  Thanks..

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Any 96-99 Lumina will have what you need and they are at least somewhat common in the yards here in central mn.  Definitely upgrade the other side to match.  Don't downgrade.

Edited by Dark Ride

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32 minutes ago, Dark Ride said:

Any 96-99 Lumina will have what you need and they are at least somewhat common in the yards here in central mn.  Definitely upgrade the other side to match.  Don't downgrade.

Yeah there's still a few kicking around in Saskatchewan, Canada (where I live..), the newer Luminas in the yards.  Probably would have to buy a ball joint and a pair of rotors to complete the bilateral upgrade.   They're quite the PITA to remove in the junkyard though as its hand-tools only around here, and separating everything down to just the knuckle isn't easy.  And those T60 caliper bolts are a giant pain in the butt.    On the bright side, very little salt used here (way too cold for salt to work), so not much rust.

Edited by pitzel

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