Best Size Rear Slicks

[hjsmith00843]

View attachment 230288Car currently has 31'' x 18.5'' - 15 Mickey Thompson Sportsman tires on it.

They seem rather large and close to the fender well. I want to change it to a full racing slick and I am unsure what size would look and work the best. Below is a picture of the car I just purchased. Car is street "legal" but it will never be driven on the street.

 

[dvw]

The street designation is the diameter and sidewall dimension. On a slick it is the diameter and tread. I run 10.5Wx 31 M/T slicks. They are about 15" sidewall dimension on a 10" rim, tread is just over 11". go here and look under Street, strip, and radial. All the dimensions are there.
http://www.mickeythompsontires.com/
Doug

 

[hjsmith00843]

I am not even sure what size wheel I have.

 

[Cranky]

First off, how much power does the car have? If you can hook with a 9" slick, there's no use in having anything larger unless you're going for looks vs anything else. If a 9" works, anything larger will just add more friction with the surface and create more drag. You can take a straight edge and put it along the side walls of the tires and measure to the bead seats and get a very good idea just how wide the wheels are.

 

[SUPERSTOCKRACER]

The street designation is the diameter and sidewall dimension. On a slick it is the diameter and tread. I run 10.5Wx 31 M/T slicks. They are about 15" sidewall dimension on a 10" rim, tread is just over 11". go here and look under Street, strip, and radial. All the dimensions are there.
http://www.mickeythompsontires.com/
Doug

I agree because this is what I run and I have tried almost every brand slick. As Cranky said, you need to find out what size rim you have. You can run a 10" rim up to a 14" rim with these stiff sidewall slicks but I run 10" on mine and tried 12" with no issues.

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They also hook insanely too

 

[hjsmith00843]

I do not pick the car until Monday afternoon. I am out of town until then. As for horse power I am unsure. I will measure the wheel and report back. I assume Radial tires are better than the bias ply slicks. There are some beautiful vehicles in the above post.

 

[daytona kid]

Forgive me slick fans but I may be going out on a limb here, I'm thinking he may want to consider some M/T street radials or similar. My reasons for this opinion are- The street radials will hook as good as you'll probably want/need, as seen in vid below. Also, I had a RR with fairly big street tires (N50x15s big back then) on 10" rims, I wanted to get slicks and go to the strip. A bud at the speed shop recommended the size slick I needed, But it was a much smaller width than my street tires, maybe 9", so I stupidly got some a little bigger to try to keep the big back tire look, like maybe 10" I think., not considering that my bud said they would be too big. Well he was right, even with my 500hp motor in my 70 RR, 4 speed, 4.88 gear it would bog/bite to much off the line and would have been a lot quicker with a 9" slick. The slicks were also kind of more maintenance and I was kinda skeered of them too, being so thin sidewalled and seeing some blow on other guys cars causing crashs/totaled cars. I'm thinking you want to try to keep a little of the bigggy tire look?, and I think you could run a street radial that could be bigger than the right slick for your power, unless you have 650hp or so. IMO, A street radial might be a little safer and maybe a little less work., I was always airing them up and down, picking out little sharp things, etc.. I guess it all depends on how much hp you have. That car really looks good and I assume by the mods I can see, just guessing I bet it has some big hp. Why don't you trim the wheel well lips where you are worried about rubbing and try the tires you have for a run or 2?
https://www.youtube.com/watch?v=bkGD3JITfb0

 

[dvw]

We hook my kids turbo car on 275/60 radials running 9.80's w/o issue. It does take a nice shock package to make them work at his power level. It makes around 780hp. At lower levels we've hooked on 255/60 radials as well. I agree if it's a show, street, drag car I'd get the 315/60 radials and call it a day. If you were strictly bracket racing it I'd stick with the M/T slicks.
Doug

 

[SUPERSTOCKRACER]

With Hoosiers with the soft compound, you'll hook great for about 30 passes then the sidewall goes away. I had them on my 63 Plymouth and now on my 65 black dodge small tire car. Hoosiers after 17 passes are now junk.these were 29.5 x 10.5 non W bias ply slicks

 

[hjsmith00843]

This is the mods that I currently know about. A speed shop built the car out of NC and I am going to contact them and see if they have more information on the car.

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My goal with the car is to be a consistent bracket car. I will be running in the 1/8 mile mainly at the local tracks. I would love to run in the low 7's but if the car will not do it then I will just work with what I have. I would rather have a consistent car than one that is fast and not as consistent.

 

[2059]

I agree w/ Daytona kid an DVW. If you watch your tire pressure and heat 'em up, I think you'll find they perform very well. I found M/T's Sportsman Pro's work well for me. As you can see, they hook well enough to "wrinkle down" at 24 lbs of pressure. Keep in mind I don't race the car however; It hooks pretty well for a ~600HP Hemi. These are 28X13.5's. I had a set of Hoosier street slicks on previously and didn't like the way they "felt". That's just me. Also, You may want to get used to the car before you change out the tires.

Good luck and keep us posted on your choice and results..

 

[383man]

I feel we need to know the combo real good to get an idea of the power the car makes and what suspension it has on it now. There are alot of choices today and the question also is how big do you want to go ? Do you want just enough to hook good consisdently or do you also want the looks of the big tire back there ? It looks like I see a 12.3 et on that paper but I cant see the mph as the mph will give an idea of what kind of power its making. Also whats the car weigh ?
Myself I like the radial 9" slick I use as I drive the street and the car handles better with radials on all four corners and does not wander at all on the top end as it did a little when I had bias tires in the rear and radials up front. I have basically old 60's and 70's suspension as I just use SS springs and standard long non adjustable rear shocks and the 30 x 9 Hooser radial slick hooks good for what my car is in running 10.70's and being street driven most of the time.

Do you know the mph the car ran for the last owner on the 12.3 run as I can see they say it was spinning ? You have many good fast racers on here that will help you make your decision but all the info on the car we can get will help. Ron

 

[Cranky]

The 12.3 gives some idea that it's making some power but knowing the MPH and the rest of the short times would help more.....

 

[hjsmith00843]

I made my bed on the tire choice. I found a set if new MT 31 10.5 15w tires for $300. Too good of a deal to pass up. If I do not like them when I replace them I will try something new. I then turned around and sold the tires to the previous owner for $300 so I will not be losing anything if I do not like them. The tires that are on the car currently was brand new too.

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I will update on what times it is running after next weekend. I will be going to a test and tune. How ever I am unsure of how hard I should turn the engine. It is the 340 with a steel crank with a decent cam 587 lift and 303 duration. Not looking to make any record runs. Just want to feel it out and see if it tracks straight. It currently has a 6500 chip in it now.

 

[aldal]

Mopar Performance Chassis guide 9th edition has a lot of great information on the subject.

 

[Budnicks]

with the 5.13:1 gears {not bad for 1/8th mile}, IMO I'd stay with a taller tire, or it'll be possibly over geared,
The overall weight of the tires/wheels "rotating mass" can effect the performance,
along with too much tire, causing lack of wheel speed, doggy it out of the hole/staring line/60ft,
the lighter wheels & tires is always better, especially with a lower HP SB combo, that has less torque,
but you have a pretty steep gear, to help make up for allot...

good luck, have fun

 

[hjsmith00843]

I found some more information on the car thru this ad from a previous owner. Found it by searching the VIN number. It is much cleaner now than in these pics. It is a rear coil over car with ladder bar suspension. Wish I could post more pictures in detail but the car is not at my shop yet. I had to sell my current car to make room for it. I have it in storage till Tuesday. http://www.2040-cars.com/plymouth/Road-Runner/1973-plymouth-roadrunner-base-5-6l-560251/

 

[hjsmith00843]

I think it looks much better now. Changed the tires to a slick and dropped the rear coil overs to a lower position. Still need to set the pinion angle. But it sits so much better now. The tires are over inflated in this pic so I think it will drop slightly when I set it to racing pressures. I think there may be 25 psi in the tires right now.

 

[Budnicks]

looks good