MCfan

Looks like you have made some excellent tire/wheel combo choices for both front and rear, Mark! All four tires will be 27" tall with 10" wide treads on the front and 11.2" wide treads on the rear. I would guess that the addition of 2" drop spindles will result in a modest "rake" stance but that is probably what you are trying to achieve anyway. The +6mm offset on your front rims gives you a bit more clearance with the frame on tight turns and the +12mm offset on the wider rear rims centers your 285/40s within the available space with approximately .8" clearance inboard and outboard. It all looks great "on paper"! Looking forward to hearing and seeing how it turns out when "the rubber meets the road". 😀 Good luck and thanks for sharing!

Mark, I appreciate your observations relative to the centering of a 10" wide rim (11" overall width) in the 13" available space between the rear quarter panel and the frame on our first gens by using a +12mm offset. I don't believe you mentioned the size of the tire you are planning to run on those 10" rims but the visualization tool uses the tire size (width and height) for comparisons, not the rim dimensions. Point being, that depending on the width of the tire you mount, you could still run into some tighter clearances. However, having the rim perfectly centered with the +12mm offset, gives you the very best latitude for some additional sidewall width. I'm guessing you are planning to run a wider tire on the rear or you wouldn't have gone to the 10" wide rim. I compared my 275/60s on 15x8" rims with 5" backspace (+12mm offset) with your 18x10" rims with 6" backspace (also +12mm offset) and it places a 275/45-18 in exactly the same position as my setup which I know has about 1" clearance inside and out. I also looked at the wider and taller 285/45-18 and 295/45-18 tires which reduce the inside and outside clearances by .2" and .4" respectively. Either should still work for you on the rear. This is a good example of why it is so important for positioning and clearance considerations to work with offset rather than backspace. As we both have proven with our different setups, using a +12mm offset with any rim width is what our first gens need to center the rear tire/wheel combo in the available 13" space.

Mark, I am running 255/60s on 15x7 rims with 4.5" bs (+12mm offset) on the front with stock spindles. Using Tiresize.com, the Tire Size Comparison tool shows your combo is .3" shorter and .4" narrower than mine. Then, using the Wheel Offset Calculator and Visualizer, the positioning of your combo, 245/45s on 18x8 rims with 4.75" bs (+6mm offset), will be as follows: outer sidewall is .04" further out; inner sidewall is .44" further out, top of tire is .15" lower. To me, all of that says your combo will fit and work as well as mine IF you were using stock height spindles. Frankly, I would think the 2" drop spindle would mostly affect the clearance from the top of your tire to the top of your inner wheel well, but it may also close up some clearances at the extreme ends of your turning range. Since I have absolutely no experience with dropped spindles, I can only guess that you will probably be okay with that combo - at least I hope so, Good luck!

Ron, I think you will like the result of installing this conversion (although you'll never get tp see it while you're driving)! I had a guy pull up beside me just last week and ask if my tail lights were aftermarket (as he assumed). I confirmed that they were and told him they were Shiney Hiney LED conversions. He loved them.

Great looking '70 SS but something seems wrong here. Either it's not actually an SS or there is something seriously wrong with the car (that can't be known by the single photo). Maybe the owner just has no clue of the current market? I would think anyone who represents his car as a true SS and knows the relative rarity of that model would also know the current market value. I bought my '70 SS in Wichita ten years ago and paid more than this asking price for it. I thought I got a reasonable deal and it didn't have rear disc brakes and cool wheels and tires, either. If it is legit, that is one heck of a deal! My son-in-law still lives in Wichita and might be able to help check it out if anyone is interested.

Congratulations on your find and purchase, Jared! I understand and share your affection for '56 Chevys. The first car I ever owned was a '56 Chevy Bel Air 4-door HT with a 265 and a Powerglide. Mine was Turquois blue and Ivory like the one on your sweatshirt. I was a sophomore in high school when I bought it for $600 in '63 with my own money. I couldn't afford any major modifications back then so a chrome air cleaner and exhaust tip plus a set of baby moons was pretty much it. Flat black electricians tape on all of the vertical bars of the chrome grill gave the effect of a billet grill and was easily reversible. New rear tires and a new water pump were also added, otherwise it was completely original and in good shape inside and out. Loved that car but a rod was beginning to knock and I knew I couldn't afford an engine rebuild so I dumped a couple of cans of STP in the crankcase and sold it after a year for $375. Good experience and good memories ... Good luck restoring yours - it's a beauty!

Nice! That white '71 SS even appears to have the correct rear bumper and hard-to-find rubber strip. Both are rare and gorgeous specimens of first gen Montes!

Whether you believe the "science" or not has no bearing on the validity or usefulness of the Wheel Offset Calculator. Offset and backspace are different measurements of the position of the wheel/rim mounting surface and are taken from different physical references. Offset is measured from the centerline of the wheel/rim while backspace is measured from the outer lip/edge of the wheel/rim on the inboard side. If two rims of different widths have the same backspace (3 1/2" or whatever) they will have different offsets. in your example, the 15" wide rim has an offset of -115mm (4.5") while the 8" wide rim has an offset of -25mm (1"). Conversely, if two different width wheels/rims have the same offset, they will have different backspaces. A 15" wide rim at 0 offset has a 8" backspace while an 8" wide rim at 0 offset has a 4.5" backspace. The backspace of any rim at 0 offset is always (rim width + 1)/2. BTW, the Wheel Offset Calculator with convert any offset to backspace or backspace to offset if you also input the rim width. The issue is the positioning of the wheel/tire combo relative to the body/chassis structure around it. The location of the mounting surface of the wheel/rim is clearly fundamental to its relative positioning within the body/chassis space. This discussion is about the practical use of wider tires and rims for first gen Montes which have stock bodies and rear ends of known dimensions and a practical range of wheel/tire combinations that will work. The beauty and value of the Wheel Offset Calculator at the tiresize.com site is that you can enter any working/fitting wheel/tire combination for a first gen as the current setup and then compare any other prospective/desired wheel/tire combo to it and visually see how the positioning will change relative to the current setup. It also gives you the exact dimensional changes so you don't have to guess by just looking at the comparison image. You should be able to see and measure any/all sidewall-to-fender/frame clearances with your current setup and know if the change in wheel/tire position of any new setup will fit within them. With online tools like the Wheel Offset Calculator readily available, I don't understand why anyone would guess or take a chance on some wider wheel/tire combo working on their first gen Monte. It's not rocket science ...

Thanks, Tom, Let's focus on the Monte. That 5 1/2" Back Space on a 10" wide rim is exactly 0 offset (see the table in the Wheel Offset Calculator). If you put your Monte's setup in the Wheel Offset Calculator and then compare it to Jeff's proposed setup with the same 275x60-15 tire on the 15x8.5" rim with +1.25" (32mm) offset (6.0" BS), the entire tire/wheel combo is moved exactly 1 1/4" inboard, not 1/2" as you may have suggested. A Back Space figure without the accompanying rim width is meaningless. Back Space comparisons are meaningful only when comparing rims with exactly the same width. That's why wheel manufacturers use offset because that measurement is relative to the center of the rim (regardless of rim width). Oh, sure, they will quote you a Back Space measurement but only for a specific rim of known width. Next, I compared your setup to mine. Same tire size but my rims are 15x8" with 5" BS (which is +12mm offset). As you would expect, my tire/wheel combo is 1/2" (.47") further inboard for additional outer quarter panel clearance. I also use my telescoping bore gauges to measure the inboard and outboard minimum clearances of my setup. Inner sidewall of 275/60 tire to inner quarter panel was 1.4" driver's side and 1.14" passenger side. Outer tire sidewall to wheel well lip (untrimmed) was 3/4" driver's side and 1" passenger's side. Naturally, one would have to consider the worst case since the drive train is not necessarily perfectly centered with the body. Further, some shift in the drive train relative to the body during hard acceleration, braking or body shift during turns should be a consideration. Now, as I revisit my earlier comparison of Jeff's proposed combo to my current set up (knowing actual minimum clearances), it appears that he could technically run 275/60s on the rear using those 8.5" rims but will only have 1/4" of inboard clearance. That may not be adequate under all of the various considerations listed above. Alternatively, he could run 255/60s or 245/60s or even a 235/70-15 (which is also 28" tall) on the rear only and the inner sidewall would be within .04'" of my setup, giving adequate clearance all around. Likewise, he might get by with 225/70s on the front with some rubbing on the tightest turns. I have no idea what a 70 series tire looks like mounted on an 8.5" wide rim but that is another consideration. Thanks for sharing your Monte's tire/wheel setup, Tom. Every workable wheel/tire combo we know about lends insight for making decisions on other available combos.

What was the width of the rims with 5 1/2 backspace? Were they used on the front, rear or both? Thanks.

Jeff, I assume you are interested in a wider rim in order to run wider tires so it may come down to how large of a tire you plan to run. According to the Wheel Offset Calculator at the Tiresize.com website, a 1 1/4" positive offset (+32mm) is equivalent to a 6" Back Space on an 8 1/2" wide rim. Generally, positive offset (greater Back Space) on a rim is good for our first gen Montes because it moves the wider wheel/tire combo inboard away from the quarter panel, especially in the rear. HOWEVER, too much positive offset can get you in trouble in the front with rubbing against the frame on tighter turns and in the rear with rubbing on the inner quarter. I used the wheel offset calculator to compare some tire/wheel combos using those 15 x 8.5" rims with the combos I am running because my wheel/tire specs are known and clearances are all workable. Here's what I found: On the front: If you mount a 255/60-15 on those 8.5" rims with +32mm offset, your inboard sidewall will be .79" closer to the frame than my 255/60-15s on rims with only +12mm offset. I am positive that combo will rub on tight turns because mine barely rubbed until I put a 1" spacer in the front coils. Dropping back to a 245/60-15 tire on those rims will still move the inboard sidewall .59" closer to the frame and they will also rub on sharp turns. On the rear: If you mount a 275/60-15 on those 8.5" rims with +32mm offset your inboard sidewall will also be .79" closer to the inside quarter than my 275/60-15s on rims with +12mm offset. I can't say for sure that they will rub but I would be nervous that they might. If you drop back to a 255/60-15 tire on those rims the inboard sidewall will be .39" closer to the inside quarter panel and that is probably doable. If you have to run a narrow tire get the inboard clearance you need, what is the point of using 8.5" wide rims? It is important to remember that the offset of any rim is relative to the exact center of the rim and is therefore independent of the actual rim width. However, Back Space is relative to the outside edge of the inner rim and is totally dependent on rim width (see the conversion table in the Wheel Offset Calculator at Tiresize.com). For any wider rim, including the 15x8.5", to work well on our first gens, an offset of +12mm (+1/2") is nearly ideal for 60 series tires. Some have tried 50 series tires on the rear and more positive offset is usually required in addition to trimming the wheel well lip. Because of the almost certain clearance problems on the front with wider tires, I'd pass on those particular rims, even as cool looking as they are. JMO

Hard to say what will solve your body roll problem best, Scott, but you have several options including new springs, shocks, anti-sway bars and air bags or combos of these. I have had good success with a combination of rear bars and air shocks/bags. I used Moog 5379 and Monroe air shocks on my '70 SS and the stock BM rear coil with Air Lift 1000 air bags on my '70 4-speed. Both had rear anti-sway bars. Others have used Moog CC501 cargo coils successfully. If air shocks or air bags (i.e. Air Lift 1000) are terminated individually with Schrader valves, you can adjust the pressure differently side to side if necessary. You can also adjust ride quality and rear end height better with air than with fixed height/rate springs. Good luck.

Welcome to the club and forums, Mike! Looks like you have a great starting point of years of personalization and enjoyment. One nice thing about a lower optioned first gen Monte is that you can enjoy several projects that add "factory" upgrades and still have an original car (albeit not matching your original Build Sheet). I spent several years after buying my low-optioned '70 4-speed car just adding factory options like power steering (it's not standard), power windows, power door locks and a full gauge dash conversion, all of which increased the pleasure of daily driving. I don't know how mechanically inclined you are, but rebuilding/refreshing the front suspension is very doable, as is adding the RPO F41 anti-sway bar and boxed control arms to the rear. Swapping in a four barrel carb and manifold should be a nice "original" upgrade, also. I like the original appearance on first gens but am happy to add functional upgrades even if not original factory options. Keyless door and trunk entry, power seat back releases, LED dash lights and tail lights and rear air bags are non-original upgrades I use and enjoy every outing and they don't affect the original appearance of my '70. So, I think lower optioned models are just more opportunity for enjoyable projects and personalizing your Monte to your own preferences. Enjoy!

Mike, I used the wheel offset calculator at tiresize.com to compare your wheel/tire combo to mine and verified that it should fit fine on both front and rear. In fact, you will have slightly more inboard clearance on the front (to avoid frame rubbing) than my setup which is 255/60-15 on 15x7 rims with 4.5" BS. On the rear, your outboard side wall has only .07" less clearance from the wheel well lip than my 275/60-15 on 15x8 rims with 5.0" BS and I currently have about .75" of side wall clearance. However, if you ever decide to mount 275/60s on the rear, the 4.5" BS on those 8" wide rims could get you dangerously close to the wheel well lip (unless you also decide to trim it). Great looking wheels, BTW!

Rob, may I ask where in FL it is located? Thanks.