Over sized Tire 1980 Mirada

Mirada 1

New Member
Joined
Mar 26, 2024
Messages
4
Reaction score
0
Location
Truman Mn
Good morning Everyone , Im new to the group here , I recently just bought a 1980 Dodge Mirada with a 318 , Bought it from a older couple it was somewhat of there daily driver , so everything works , cruise , and they said the ac still works , My question I have is Im putting aftermarket wheels on it 15x7 with $" backside with 225/70r15 tires up front , 15x8 with 4.5" backside and was thinking about the 255/70r15 on the rear any of you done this combination , looking for other insight wanting to know if everything would fit right , Thanks
 

Camtron

Well-Known Member
Joined
Apr 25, 2019
Messages
1,867
Reaction score
1,415
Location
US
I can get 255/60 to rub pretty good on the rear going over bumps/railroad tracks/drainage ditches at moderate traffic speeds with upgraded rear suspension, the extra 2” could do some damage.
The 29” tire, will throw your speedometer and odometer off too. The tire makes 42 less revolutions per mile. Getting a smaller corresponding speedometer gear will keep mileage/speedo reading correct in the car.
 

Mirada 1

New Member
Joined
Mar 26, 2024
Messages
4
Reaction score
0
Location
Truman Mn
Glad I asked , So I should run the 60 series , I have seen other guys post that they can 275/60r15 with no problem is this true ? I also should tell you im adding a 1-1/2" shackle lift as well , Thanks for you help with this matter
 

Mirada 1

New Member
Joined
Mar 26, 2024
Messages
4
Reaction score
0
Location
Truman Mn
I can get 255/60 to rub pretty good on the rear going over bumps/railroad tracks/drainage ditches at moderate traffic speeds with upgraded rear suspension, the extra 2” could do some damage.
The 29” tire, will throw your speedometer and odometer off too. The tire makes 42 less revolutions per mile. Getting a smaller corresponding speedometer gear will keep mileage/speedo reading correct in the car.
Glad I asked , So I should run 60 series , I have heard others say they can run 275/60r15 with no problem is this true ? I also forgot to mention Im installing 3" to my rear shackles so that should bump my height about a 1-1/2" , Thanks for your help with all this
 

Camtron

Well-Known Member
Joined
Apr 25, 2019
Messages
1,867
Reaction score
1,415
Location
US
They’ll fit but, you’ll likely have to slow down like it’s lowered for things mentioned above.
I wouldn’t know with the drop shackles. I mentioned ordering a set of them on here when I first bought my car and started posting here…was pretty heavily ridiculed by the guys.
If you want the car to handle with good spring rebound rate, put the time and money into a good set leaf springs/bushings, consider doing an ISO bushing delete from the rear axle and going to B-body shock plates to gain rear shock options. The ISO delete will raise the rear end up about as much as you’re looking for while improving handling as well.
 
Last edited:

Mirada 1

New Member
Joined
Mar 26, 2024
Messages
4
Reaction score
0
Location
Truman Mn
They’ll fit but, you’ll likely have to slow down like it’s lowered for things mentioned above.
I wouldn’t know with the drop shackles. I mentioned ordering a set of them on here when I first bought my car and started posting here…was pretty heavily ridiculed by the guys.
If you want the car to handle with good spring rebound rate, put the time and money into a good set leaf springs/bushings, consider doing an ISO bushing delete from the rear axle and going to B-body shock plates to gain rear shock options. The ISO delete will raise the rear end up about as much as you’re looking for while improving handling as well.
Sounds like Maybe I should run the 255/60r15 in the rear , I have almost got the shackle job done , I understand what people say about handling etc.. since its almost done , im going to try it and see how it is , Im mainly going to be driving this as a summer car to from work on county roads which are pretty straight and boring and a total of about 15 miles one way [lol] , if its to bad of a ride or notice big things at least everything on the shackle end will come apart easier for me , Thanks for your advice , I hope to do more upgrades next winter and other things between now and than
 

Camtron

Well-Known Member
Joined
Apr 25, 2019
Messages
1,867
Reaction score
1,415
Location
US
Sounds like Maybe I should run the 255/60r15 in the rear , I have almost got the shackle job done , I understand what people say about handling etc.. since its almost done , im going to try it and see how it is , Im mainly going to be driving this as a summer car to from work on county roads which are pretty straight and boring and a total of about 15 miles one way [lol] , if its to bad of a ride or notice big things at least everything on the shackle end will come apart easier for me , Thanks for your advice , I hope to do more upgrades next winter and other things between now and than
For sure, take your time and enjoy your car. That’s the most important part of all.
If you use the little magnifying glass/search tool on here, you can find all kinds of suspension and tire size questions and answers. Some of it is thread specific and easy to find, but there’s even more gold randomly sprinkled in threads where you may not expect to find it. Using the keyword search option is a big help.

Cheers, have fun!
 

Duke5A

Well-Known Member
Joined
Apr 6, 2018
Messages
1,661
Reaction score
876
Location
Michigan
If you don't plan on a host of other upgrades I would run 235-60-15 on all four corners. Now you can rotate the tires. You'll need a different axle and some motor upgrades to spin those tires.
 

AHBguru

Member
Joined
Apr 3, 2024
Messages
14
Reaction score
5
Location
WI
245/60/15 is equal to the 215/70/15 that was standard on M-body squads. 27" diameter, fits perfectly, still rides decent, sticks well. I believe the Ford P7B 235/55/17 is also the same overall diameter, but I can't recall if they mount up to the Chryslers.
 

Dr.Go!

Member
Joined
Oct 26, 2020
Messages
16
Reaction score
5
Location
Wisconsin
The above posts are spot on and if I had that advice 2 years back, that might be me. I only drive about 2,000-3,000 miles per summer. I wanted an offset look... what I did is likely not the best set up, but here is what I did. Car was all stock. My back leaf spring were badly bent since about 1984 (long story and long trip with trailer I got stuck towing and bottomed out for 400 miles as kid). I lived with limping along with air shocks for years and light towing, but still saggy. With a fully loaded car and trunk with cooler and swap meet cast heads in the trunk with a couple more car parts...trunk and back seat full and 2 adults. Even with air shocks full to max, I bottomed out hitting my mufflers at least 20 times on the Pennsylvania turnpike when I ran the 235/60/15s on all 4 corners...loved the tires, but I needed to replace the bent leaves. Last summer I replaced the leaves with Eaton Detroit Spring new leaves with 1" extra and made as heavy duty. Put on BFG Radial TAs - 245/60R15 in front that are 26.6" diameter and spec said 783 REVs per mile. I put 275/60R15 in back for the offset and taller look. Those say they are 28" tall and 743 REVs per mile. Still had room to leaf where a 295 would have fit, but my rims are not wide enough. Like others said, my speedo is off until I fix that. I calculated and also timed it so that I could make my adjustments for speed... I think about 5mph off at highway speed. I love the look. I love the firm feel of new leaves. I did not bottom out. I did not cut any sidewall on my Pennsylvania Turnpike run with minimal air (like 50 pounds) in air shocks. I did put new air shocks on just as protection in case I get stuck adding too much weight to trunk or towing heavy tongue weight trailer. I am happy with the results. Likely not for everyone. I still tow an old boat with lots of tongue weight, so I just fill the shock halfway to 100lb and it looks as flat as with no trailer and minimal air. I will try to find and load some before and after pictures.

Old bent -flat spring.jpg


new vs old.jpg


New and old.jpg


Bent original springs.jpg


New Eaton Detroit Spring plus 1 inch heavy duty leaf springs.jpg


After new Leaf Springs.jpg


New Leaf Springs - parked up hill.jpg
 
Back
Top