1972 MC 350/Auto - Suspension Upgrade

[MC1of80]

Just like Steve said. Put the jack under the shock/lower control arm mount and jack up till you can slip the coil in, repeat for other side. Ez pz. 

[B-Man]

@cny first gen 71 and @MC1of80, thanks guys.  I guess I was almost there and didn't consider jacking up one side to lower the other ... hmm, makes sense though.  I will give it a shot tonight, though my coworker showed up with the spring compressors too.  Updates coming!

[cny first gen 71]

1 hour ago, B-Man said:

@cny first gen 71 and @MC1of80, thanks guys.  I guess I was almost there and didn't consider jacking up one side to lower the other ... hmm, makes sense though.  I will give it a shot tonight, though my coworker showed up with the spring compressors too.  Updates coming!

I learned that here from Aaron,  I always had a helper at the shop that would pull down in the tire to get them in. One time at the shop I worked at was working on a ferd and another guy put a pry bar between the axel and frame to get a spring in well the bar slipped and I moved out of the way but my foot stayed planted on the floor my knee twisted nicely had surgery 3 weeks later was out of work for 10 weeks that's why I'm always very careful working on stuff now. Safety first. 

[B-Man]

Update ... new rear coil springs and isolators installed. Much easier with the borrowed set of spring compressors, for sure. I was really tempted to drop it down and see the stance but I've got more work to do while the jack stands are giving a gravity assist.

Onto the front end - SWEET MERCIFUL CRAP!!!!!!!!!!  I had no idea the front end was in as bad a shape as it is. I mean, check out that passenger side upper ball joint. Geez!  I guess I'm in the market for a front end rebuild kit.  Onward and upward!

[cny first gen 71]

Not sure how far your going on front end or how experienced you are but some parts of that can be very dangerous, be very careful!

[B-Man]

For the front suspension rebuild I'm going with an inexpensive stock replacement for now.  As mentioned in previous posts on this thread, at some point I may go 'full bore' on the suspension upgrade to do some track-racing.  So keeping the car on all four while not breaking the bank, for now, is the immediate goal.

I found the kit linked below on the OPG web site for $193.  The price for the same kit on Summit is $240.  This will be a fun afternoon project, with a buddy, for sure.  I've still got the borrowed spring-compressors, along with a generous pickle fork and some sledge hammers!!

https://www.opgi.com/chassis-suspension/steering-components/standard-front-end-rebuild-kits5/rebuild-kit-front-end-1971-72-a-body-oval-rk1008.html

Note: This same kit is offered with oval or round lower rear control arm bushings.  I called OPG and one of the tech's there informed me that some Monte Carlos came with an oval bushing there, and some came with a round one.  Sort of a who-made-it and where-was-it-made thing.  My MC has the oval bushing, confirmed this morning before I left the house.  The more you know!

[cny first gen 71]

First I'd call to make sure they have it in stock, also I'd suggest the center link (as long as your going to do all of that) not in that kit and probably going to have to have the bushings pressed in. Good luck be careful with the springs they can hurt.

[B-Man]

On 3/29/2023 at 1:28 PM, MCfan said:

Brendan,

If your rims are actually 15x7 with a measured 4.25" backspace, they should work beautifully with 255/60s both front and rear.  Having a measured 4.25" backspace on a 7" wide rim gives and offset of +6 mm (versus a -6 mm offset with the same backspace on an 8" wide rim).  That means your wheel/tire combo will be moved .5" further inboard (compared to an 8" rim) which increases your rear wheel well lip clearance.  All of my initial calculations and examples were based on your assumption that you had an 8" wide rim (not counting the lips) so you can disregard that reply if, in fact, you have 15x7 rims with 4.25" backspace. 

Honestly, it sounds like you may have a set of factory Monte 15x7 rallys with the 4.30" backspace.  If you do, you should be good to go. Good luck.

@MCfan, so its been 2+ years since you helped me figure out tires, so I guess it's finally time to order them!  I've been riding dirty on these old dry rotted tires all this time.  Over the weekend I came out to a flat on the front left - luckily while my MC was in the garage right next to the air compressor, jack and tools :).

Buried in this thread it the fact that I found the "FW" marking on my wheels.

FW   15X7     BS-4 1/4"    71-up most any GM

So I'm going to go ahead and order up 4 of the 255/60-15 tires.  But will shop around for pricing and coupons of course.  Thanks again for all the info a couple of years ago!  And I'm sorry its taken me this long to heed the advice.

[Scott S.]

There's not a lot of options on that size tire.... Believe me, I'm still looking too. lol 

Cooper and B.F. seem to be the most available, and priced about the same.

I found Tiger Paws, but they're a bit more pricey. 

And, of course, there's always the "no name" versions.   

[B-Man]

@Scott S., are you calling my Dayton Daytona SR tires "no name"??!!  I'm so NOT insulted, haha.  They were so popular, they sold out and aren't even made anymore according to Google!

I will probably end up with the Cooper Cobras.  I just need to find a source and a discount code.  Most of the YouTube channels I watch (VGG, PBG, JD, etc) have tire sponsors.  I wouldn't mind giving them a bump and maybe get 5% off or whatever.

[Scott S.]

3 minutes ago, B-Man said:

@Scott S., are you calling my Dayton Daytona SR tires "no name"??!!  I'm so NOT insulted, haha.  They were so popular, they sold out and aren't even made anymore according to Google!

I will probably end up with the Cooper Cobras.  I just need to find a source and a discount code.  Most of the YouTube channels I watch (VGG, PBG, JD, etc) have tire sponsors.  I wouldn't mind giving them a bump and maybe get 5% off or whatever.

There's ALWAYS Amazon..... 

[72 Monte Carlo]

I bought my Cooper Cobra tires through the Walmart App.

I haven't put them on the Cragar wheels yet, because I want the Monte to be painted first.

[B-Man]

Well I went out to the garage this morning, and the front left tire was flat again.  So i guess the dry rot in the tires is a terminal issue.  And yes, I got VERY lucky that it happened while in my AC'd garage, right next to my tools and jack stands, and NOT on the highway next to a semi.  So she shall live to ride another day!!!

[Robnhood]

On 4/17/2023 at 11:09 AM, B-Man said:

You know, spring spacers might be all I need for the near term. Again, I plan on a full suspension upgrade / rebuild at some point. I will grab some spacers and see if that gets me what I want for now - a combination of ride quality and ride height. Cheating the ride height with spacers may degrade the ride quality a bit. But it might not either 

Ok.  So I know that this picture was posted a long time ago, but I know where that was taken! I recognize the submarine in the background.  LOL!

[B-Man]

Update on the tire purchase ... the other day I bought Qty2 of the Copper Cobra 255/60-15 tires off of Amazon for $158 each off of Amazon (free shipping of course), and its a 7-day lead time (coming in on Monday 7/28).  I figured I would buy 2 to start and replace just the fronts.  My concern is that the 255/60-15s might be at the peak of what can fit up front, but will fit just fine in the rear.  If I can drive around for a bit with them on the front and confirm that for my MC there are no unintended consequences, then I will leave them and order 2 more for the rear.  Else, I will move them to the rear and get something a bit smaller for the front (whatever I'm currently running, would have to go back through this thread).

Anyway, thats the tire plan update

@Robnhood, yep that's ye ol faithful Nautilus in the background.  Certainly a relic now, but one of the coolest of the coolest no doubt!   I live nearby and make it over there at least once a year for one reason or another.  My dad (retired sub Captain [Sturgeon -class]) was on the board at the museum forever.  And I work, sort of, in the industry.

[B-Man]

I got the 255/60-15 Cooper Cobras on the front of my 72 yesterday, and took her for a rip this morning. As expected, zero issues with them in the front. Even with sharp, hard cornering.

Caveat - my front suspension is still 100% original and well worn, other than the Bilstein shocks I put in (see earlier in this thread)

In this photo I measure:

Floor to trim 27 1/2 in

Front of tire to fender trim 1 1/2 in

Rear of tire to fender trim 4 1/2 in

When the wheels are turned all the way to the left, there is about 1 1/2 in (est) between the rear, inside wall of the tire and the control arm. When the wheels are turned all the way to the right, there is about 3 1/2 in (est) between the forward, inside wall of the tire and the away bar.

I'm definitely going to bigger in the rear. Will have to go back in this thread, the wheel / tire thread and elsewhere to take my best, safe guesstimate.

But thanks for the help here everyone!

[Scott S.]

Good to know the 255's fit the front. 

If I every get a pair of 8" wheels now I know I can fit some rubber up there.   

[SPLATT71MC]

7 hours ago, Scott S. said:

Good to know the 255's fit the front. 

If I every get a pair of 8" wheels now I know I can fit some rubber up there.   

I got 275/40r18 to fit the front on 9.5 wheels wit 5.75bs

 

[Scott S.]

Any suspension modifications to make them fit ??

[B-Man]

3 hours ago, Scott S. said:

Any suspension modifications to make them fit ??

From above, "Caveat - my front suspension is still 100% original and well worn, other than the Bilstein shocks I put in (see earlier in this thread)"

[Scott S.]

55 minutes ago, B-Man said:

From above, "Caveat - my front suspension is still 100% original and well worn, other than the Bilstein shocks I put in (see earlier in this thread)"

Opps.... lol

[Scott S.]

Sounds pretty much what I'm running for a front suspension, but was rebuilt before I bought her.....

But I've been toying with the idea of a bigger sway bar. 

[SPLATT71MC]

On 7/27/2025 at 11:29 AM, Scott S. said:

Any suspension modifications to make them fit ??

For mine I have aftermarket a-arms and sway bar but nothing that allows extra clearance. I was going to go staggered but when I used the wheel fitting jig set for the specs I came up for the rear to get what I wanted I set it up on the front out of curiosity. I found I had enough clearance to where I might get very slight rubbing if any on the sway bar during hard cornering so it's pretty much maxed out unless I get to cutting and welding to make more clearance. On the rear it looks like if I want to in the future I can step up to a 10" wide with 6.25bs and a 295.

 

[B-Man]

Ok I FINALLY had a chance to swap the 255/60-15 tires on the driver side from front to rear for a fit check. Here are the resulting clearance measurements (inch)

2 1/4 front of tire to trim

4 1/4 rear of tire to trim

3 1/4 down from horizontal fender edge to sidewall tangent

3/4 tangent sidewall to fender edge extended down with a straight edge (see photo). This is the dimension that will close with wider tires and the suspension flexing down or in a corner.

2 frame front, inside sidewall

2 1/4 frame rear, inside sidewall

I might see about a tire up to 1 inch wider, but wouldn't go more than that without rolling the lip of the fender 

[B-Man]

It looks like the 275/60-15 is the right balance without pushing too much into that 3/4 in clearance (I think another forum member said this earlier in the thread). This will be 0.8in wider and 1.0 taller than the 255/60-15. So 0.4 of the 0.75 clearance will be eaten up. Fingers crossed, not a big deal