73 Riv... what options have I got here? (suspension, tires, brakes, diff questions)

Hi all,

So I have a '73 Riviera that I picked up a while back as a project. Right now it needs the entire suspension (front & rear) completely rebuilt. The bushings are all shot, the springs sag, the shocks are worn out, etc. It also stops like a 5000lb American car built in 1973 (can't imagine why ). And finally, the differential (as far as I can tell) is not a limited slip unit, which is something I'd like to change.

So, basically I've got a few questions:

1. Is there a "best" way to make the car handle reasonably well? It'll never be an auto-x car, and I don't expect it to be. I'd just like it to handle respectably. I'll post the links to the parts I had in mind later this evening if I get a chance, but basically I was looking at urethane bushings, a set of lowering springs, larger diameter roll bars, bilstein shocks and a quick ratio (12:1, iirc) steering box. Does anyone have any other suggestions?
2. What's the largest size wheel & tire (width, bolt pattern, offset; I wasn't planning on going larger than 18" or so in diameter, which I figure ought to be fine...) I can put on it without going to extremes like tubbing the back end or engineering my own suspension for it?
3. I've heard that the 12 bolt is a stronger differential than the 10 bolt that is in it (at least I think it's a 10 bolt; I haven't crawled under it in a few months now). If this is the case, are there any 12 bolt axle assemblies that will just bolt up in place of the stock axle?
4. Is there any way to upgrade the brakes, say to larger brakes off of another GM car or off of something else?

Thanks in advance!

 

Re: 73 Riv... what options have I got here? (suspension, tires, brakes, diff question

If there's two things on a car I completely don't understand, it's differentials and transmissions, so this is probably a stupid question... But assuming it's a 12 bolt, would something like these work in it?
(stupid post count requirement; search for ETN-19554-010 and RMG-4900391 on Summit Racing's site)

For the car's age and weight it handles and stops very well. Motor trend did a comparison test on the '73 and found that it stopped in 160ft from 60mph, vs. almost 190 for a '73 Thunderbird, and the turning circle was <42ft, compared to almost 46 for a Toronado (though unfortunately apparently magazines didn't put cars on the skidpad or through a slalom in the early 70s). So yes, put in that perspective, it does very well.

Problem is, I live in northern California. We seem to have more incompetent drivers per mile of paved road (and I use the word 'paved' in the loosest possible sense... dunno where all the money the DOT gets goes, but it's nowhere around where I live, that's for sure) than anywhere else in the country, perhaps the world. And they're all blissfully ignorant of the fact that the Riviera weighs 2.5 tons and has no ABS, and thus have no problems cutting me off at every available opportunity. My current daily driver does 60-0 in 111ft, and most cars (including cars that weigh more than the Riviera, such as the Mercedes S600 and the Porsche Cayenne Turbo) stop in 120-135ft from 60. I'd like to drive the Buick at least a few times a week once its finished, and in my opinion, the braking and handling capabilities of the car now are not good enough to make that a particularly good idea from the standpoint of keeping the car's front bumper intact and my insurance premiums down.

It may not be possible to get the car to stop as well as the Porsche or whatever, but if I can get it into the same ballpark, say 140-150ft from 60, I'd be happy. And I'm not sure how to do that... I don't know what the diameter of the front rotors is, though my dad seems to think they're 11" and he claims that there were full size GM cars that came with 12" rotors, which should fit, according to him. I'm wondering if there's like a Baer or Powerstop or Brembo system or something that could be made to fit. I've looked, but I haven't found anything, so... o No:

 

Re: 73 Riv... what options have I got here? (suspension, tires, brakes, diff question

It is a Buick only rear end with no repro gears. You will need to get a used posi from another 71 -76 Buick 9 3/8 inch donor. Basically these were the big body Buick cars although some, like most LeSabres, did not used the 9 3/8".

 

Re: 73 Riv... what options have I got here? (suspension, tires, brakes, diff question

Somehow I didn't see the "9 3/8in" part when Smartin posted it ou: I assume then that even if I were able to find a positraction diff for it, I'd still be stuck with the stock 2.93 final drive, or were they offered with something in the 3.50-4.10 range?

The other option I suppose would be to try to swap a 'normal' 8.whatever inch 12 bolt into it, or a Ford 9in., but I have no clue what would be involved in something like that, or where I'd look to find out.

 

Re: 73 Riv... what options have I got here? (suspension, tires, brakes, diff question

Steepest available was 3.42, then 3.23, 2.93, 2.73, 2.56.. I think it goes. There might have been a 3.91 that has been seen on paper, but I don't think anyone has ever seen one in person for the 71-76 models.

 

Re: 73 Riv... what options have I got here? (suspension, tires, brakes, diff question

As far as the rear end goes, if you can find a posi it doesn't really matter what the ratio is. I have a 2.93 posi in my 71 and I wouldn't consider going to a 3.42 at any point. You have front discs on the Riviera so I don't think there is much you can really do to improve stopping, locking up the tires is locking up the tires. A rear sway bar and improved shocks will help handling, I'm not really sure that it would help stopping. You should already have a front sway bar on there as well. Better tires could help, I'm not sure what you have on there.

 

Re: 73 Riv... what options have I got here? (suspension, tires, brakes, diff question

Removing the rubber and substituting poly bushings will help the handling buut make the ride stiffer.

 

Re: 73 Riv... what options have I got here? (suspension, tires, brakes, diff question

I don't agree that just having disc brakes is the best you can do.

I used to do some autocrossing in various vehicles. An autocross event consists of time trials for cars run through pylon delineated courses laid out on large parking lots (see www/autox4u.com for info on events in the northeast. SCCA is nationwide so there's events all over the country).

Here's what I found out while trying to improve the braking performance of my '92 Nissan Sentra SE-R (which stopped pretty well to begin with):

- The performance of a braking system varies with temperature. ie, if the brakes are cold they won't work as well as when they are warm, and when they are too hot they don't work very well either. Your brakes may not be capable of locking if they are too cold or too hot... or maybe not at all if you are using those crappy non-metallic pads (I'm not sure anymore what they give you at NAPA or Big A... or even what the manufacture uses for brake pad wearing material.)

- Locking-up the brakes is a bad way to try to stop. You can't control the vehicle once you lock them up. Also, stopping distances aren't necessarily minimized during wheel lock-up (This does work the best in some snow conditions). Stopping distances are maximized in most situations when the tires are at the limit of their grip... ie. just on the verge of locking. This is how anti-lock brakes work. They apply braking until the wheel just stops turning... then the wheel is released... then locks... then releases... and so on, at a high frequency that mimics keeping the wheel at a theoretical limit of adhesion. If you don't have anti-locks (your 73 Riv sure doesn't!) Your best attempt at stopping fast would be to, very robot-like, hold the brake pedal at the exact pressure required to accomplish a limit of adhesion. Or... you could try slamming the brake pedal down and releasing it very fast...

Of course, given the variability of the performance of the brakes due to heat and other factors (are your rear drums perfectly adjusted?) your chances of making a perfect emergency stop are just about nil.

-What I found was that aftermarket brake companies such as CARBOTECH (www.ctbrakes.com) offer brake shoes and pads with fancy composite compounds that offer superior brake modulation and grab that is superior to stock brake components.

I got a set of front pads only for the SE-R and I was AMAZED at how much quicker the car stopped. After I first put them on I got the car up to 95 MPH on the highway, made sure there was no one around, and tromped on the brakes. I couldn't believe the force that tried to put me through the windshield! Not on that, they worked the same no matter if it was my first stop... or tenth. When I finally put the old pads on I swear that I thought something was wrong with them and I almost coasted through an intersection... I had gotten used to how well the brakes worked with the Carbotech pads.

I talked to someone at Carbotech on the phone and he told me that they would put the braking material on any set of brake shoes or pads if I shipped the cores to him. At the time, I was going to send cores for my wife's Subaru to him.

The biggest reason that I endend up taking the Carbotech pads off was that they squealed a bit. However, there are numerous mixes of materials that Carbotech uses and the rep assured me that I could get a set that was not annoying to use everyday. Unfortunately, I never followed through with the Subaru... and I stopped autocrossing so I didn't finish my reasearch. I guess I should put my money where my mouth is and get some Carbotech brakes form my minivan... and my 72 Riv. That way I'd REALLY be able to give a good testimonial.


I don't work for Carbotech or anything... It's just that I believe the sales rep that their stuff works as advertised... you just need to be sure what's being advertised. They make pure racing brakes which will not work on street applications because they work over a different temperature range. You have to order the right stuff for the right application.

Does anyone else have any experiences with aftermarket brake pads/shoes?

 

Re: 73 Riv... what options have I got here? (suspension, tires, brakes, diff question

Have you taken the car to the track at all? Any idea what it runs in the 1/4? I'd be curious to know

It also might help if I explained why I was looking for a 3.73 (or shorter...)

Basically, my goal with this car as far as acceleration goes is a low 13s 1/4, or faster. Ideally a good deal faster. But <13.5 at least. Without having to strip the interior or dump the a/c or whatever. My gut feeling (and I may be completely wrong about this; if I am please correct me because it'd make my life a lot easier and a lot less expensive) is that there is absolutely no way in hell a 5000lb car with a 455 that's pushing at most 600-700hp through a th400 and a 2.93 (especially if I can't find a posi) is going to run a 13.5s 1/4. I just don't think it's got enough power to shift that kind of mass that quickly without shorter gears. Am I totally wrong?

 

Re: 73 Riv... what options have I got here? (suspension, tires, brakes, diff question

Hey Geeky. Alright, I've run the Riv on the strip exactly once, And as long as you don't laugh I'll post exactly what happened. This is a 1971 Riviera, basically stock with an open 2.93 rear end. My reaction time is weak, because when i hit the gas, all it did was spin. but here you are.

Reaction time1.434
60' 2.784
330'7.175
1/8 mile10.737
mph 69.56
1000' 13.777
1/4'16.353
mph.87.55

So that's it. At stockish with a posi, with good tires and some practice, I'd think 15.5 could be attained.

And Doug, all I meant was that he couldn't upgrade front drum to front discs, because he already had them. I'm glad you have had good experience with your upgraded brakes, but Geeky won't be autocrossing this car (Will you Geeky)? So there isn't really much he can do cost effectively to really improve the braking performance of his car.

By The Way Geeky. If you're looking to run the car on the drags a fair bit, It's time to put the car on a diet and start looking for weight to remove. You'll pick up speed better and stop better too!

 

Re: 73 Riv... what options have I got here? (suspension, tires, brakes, diff question

 

Re: 73 Riv... what options have I got here? (suspension, tires, brakes, diff question

Hi Geeky, I installed a 1 1/8" front sway bar from Performance Suspension Technologies along with polygraphite bushings and end links on my 73 Riv. I thought it made a huge difference. I tried a 12:1 steering box and didn't like the way it felt. As far as rear end gears, I have run 3.42's and 3.23's . The car ran 14.80 with the 3.23's and 14.66 with the 3.42's. These times were with a .030 over 455 with stock cast 8.5:1 pistons and street radials. A friend of mine has a 73 centurion that he put in an 8.5 10 bolt out of a 74 impala. He runs 14.0's with 3.73 gears. The swap was a direct bolt in. Hope this helps.

 

Re: 73 Riv... what options have I got here? (suspension, tires, brakes, diff question

Hey guys, sorry about the lack of a response for the past few days. My grandfather fell down a flight of concrete stairs the other day (the entire flight, no less) so I've been dealing with that.

Anyhow, thanks for the input guys
crazyjackcsa; Thanks for posting the timeslip info, and I agree that losing weight (both on me and the car... ou: ) would go a long way to improving acceleration, handling and braking. Problem is, offhand I can't think of anywhere to lose any weight (on the car, that is) save for replacing the front bench with buckets, which I was planning on doing regardless. Other than that... if I can find a way to do it, I will, but removing things like the A/C and the sound deadening negates what my intentions for the car are (more on what those intentions are in a later post when i have more energy and I haven't got so much stuff on my mind).

Free Riviera; Nah, no auto-x for the Buick. That's what my other car is for. :grin: I just need to get it to stop & turn well enough that I'm comfortable that a. it's safe to drive it around here, and b. that the rest of the car is as capable as the engine is (or will be, hopefully...) I think what I'm going to do is start with bigger wheels & stickier tires (look for a thread in the appropriate forum on that in the near future >_>), urethane bushings all around, stiffer springs & shocks and upgraded roll bars. Those should all help braking to a degree, and will help handling quite a bit. If I'm still not happy with it I'll go from there.

Ok, now about the differential. At the moment, the diff leaks badly. From the pinion seal, both axle seals and the rear cover. I'm assuming (though I have not checked) that to reseal it, it will need to be removed from the car. Now, if I'm going to take it out, I might as well explore options for replacing it while it's out.

According to my Hollander manual, the Buick 12 bolt is the most robust axle which will fit in the Buick. However, it also says that it interchanges with the less durable 8-7/8" 10 bolt and 8-1/2" 10 bolts installed in '71-76 Buicks, Pontiacs, Oldsmobiles and "Chevy passenger cars" (excluding station wagons). How they define a "passenger car" I'm not sure, because I'd assume the Camaro and the Caprice don't have the same width axle). However, I was under the impression that the 8-7/8" 12 bolt was installed in full size Chevys between '71 and '76. And if they did, that will interchange with the 8-7/8" 10 10 bolt (I think). Thus, I should be able to put an 8-7/8" 12 bolt from a full size Chevy in the Riviera. Which would be infinitely preferable to me to putting a Ford anything in it (and yes I know and will freely admit that the Ford 9" is probably a better differential. Unless I start breaking a 12 bolt every time I stand on it, I don't care).

 

Re: 73 Riv... what options have I got here? (suspension, tires, brakes, diff question

does anyone know if swapping another axle in really works?

 

Re: 73 Riv... what options have I got here? (suspension, tires, brakes, diff question

I think you could easliy shave off .5 sec to begin with in the 60' with a posi and steeper gears, probably even more. I've run 2.22 in the 60' as best, and I've got 3.42's and posi, but my engine seems weaker than yours. I've come in at 80 mph's at 16.5'ish. Smartin ran a flat 2 sec. 60' with 3.23's posi, at a flat 15 sec. run, that's with a very healthy engine as I've understood it.

 

Re: 73 Riv... what options have I got here? (suspension, tires, brakes, diff question

Geeky1, where are you located in California?

 

Re: 73 Riv... what options have I got here? (suspension, tires, brakes, diff question

simon1243: yes, it's possible to swap the rear end. Moser Engineering just quoted me about $3k to put together a Ford 9" (couldn't get a quote for a 8.875 12 bolt for some reason. o No with discs and a locker or a posi (price is the same, give or take a few bucks) for it; with the locker they claim it's good for 1000hp; the posi is good for 600-700ish. Only catch is I'd need to move all of the mounting brackets and hardware from the old rear to the new one.

I've gotta call some local companies that my boss recommended and get some prices and stuff from them, but if the prices aren't radically different I'll probably end up going with a posi unit from them (and hope it doesn't break after I magically come up with the money and skill to do what I'd like to do with the engine ) after I get the transmission fixed and put a Gear Vendors overdrive unit in it.


EEE: I'm up in San Jose.

 

Re: 73 Riv... what options have I got here? (suspension, tires, brakes, diff question

i was referring to using another gm axle instead of the 9&3\8" i also looked at having a ford 9" built for my car and was quoted around the same prices as you