How To: Fitting 315-50-17 Tires Without Spacers

[Micah-OST Dyno]

We recently completed another 315 tire install at the shop. This time we took some pictures so we could share how we do it and help those looking to do the same thing.

The 315/50/17 tire is a relatively new tire from M/T and a great step between the 305/45 and a 15" conversion. However, the cars we see with these tires almost always have a large spacer to help the tire clear the inner wheel well. This does the job but in our opinion it makes the car look pretty silly. Our approach is to modify the inner wheel well to clear the section width of the tire and keep everything inside the factory quarter panel.

This is what the wheel well looks like from factory.

This is the area we modify. It gets pushed in and smoothed out.

We then prep, mash, and color match paint the area.

Finally the fender liner is cut and reinstalled.

The finished product is a tire that doesn't rub, doesn't stick out, and keeps the car looking clean and professional.

 

[Speedy!]

Glad to see it done right!

 

[Old Mopar Guy]

Nice, thanks!

 

[tkracing1]

Clean job... well done!

 

[Markp]

Awesome!

 

[Hpindy]

That's my next set of tires . Thanks for the reference pics

Sent from my BBF100-2 using Tapatalk

 

[Marc W]

Just a FYI about these tires. The 305 is 28” tall. That is basically the same as stock. The 315 is 2.5” taller at 30.5”. That in effect is the same as putting a higher gear ratio (lower numerical) in it. If you are running a 2.62 ratio.... look out! There has been experience that has shown how much harder on the driveline this can be and some people who have tried it have gone back to the 3.09 because of increased breakage. In my unworthy opinion.... the 315’s are great with the 3.09’s. You are looking for a early end to your day if you run them with the 2.62.

 

[Markp]

That's my next set of tires . Thanks for the reference pics

Sent from my BBF100-2 using Tapatalk

FYI one of my guys at work was a body guy for 20 years if you want to do it. We could also grind it so that you can't even tell the rib was there.

 

[hellno]

Just a FYI about these tires. The 305 is 28” tall. That is basically the same as stock. The 315 is 2.5” taller at 30.5”. That in effect is the same as putting a higher gear ratio (lower numerical) in it. If you are running a 2.62 ratio.... look out! There has been experience that has shown how much harder on the driveline this can be and some people who have tried it have gone back to the 3.09 because of increased breakage. In my unworthy opinion.... the 315’s are great with the 3.09’s. You are looking for a early end to your day if you run them with the 2.62.

This is exactly why I’m going 15 inch conversion and going back to my 3.09

 

[Micah-OST Dyno]

Just a FYI about these tires. The 305 is 28” tall. That is basically the same as stock. The 315 is 2.5” taller at 30.5”. That in effect is the same as putting a higher gear ratio (lower numerical) in it. If you are running a 2.62 ratio.... look out! There has been experience that has shown how much harder on the driveline this can be and some people who have tried it have gone back to the 3.09 because of increased breakage. In my unworthy opinion.... the 315’s are great with the 3.09’s. You are looking for a early end to your day if you run them with the 2.62.

That is not correct information. Mickey Thompson gives the tire ODs on their site and I have confirmed them to be accurate.

305/45/17 - 28.1"
305/45/18 - 29"
315/50/17 - 29.4"

The 315 is only 1.3" taller than the 305 on a 17 and only .4" taller than a 305 on an 18; the tire we previously ran. We have been running the 315 on our 2.62 car for a while now with no issues. It still shifts into 5th at the same point down the track and we have yet to break parts from driveline strain.

Additionally, keep in mind that and added diameter is divided by two when talking about added strain on the drivetrain. This additional 0.4" inches makes the "lever" the diff has to turn only 0.2" taller; a pretty insignificant change.

 

[Markp]

Did anyone else notice the sound deadening material in pic 2 and 3 ? Looks the same as 1970 that stuff will hold water and rot out your car. I think I am going to pull all that crap out this weekend.

 

[Marc W]

Thanks for that info Micah. The measurements I was giving was from me measuring with a tape on my car. Maybe inflated to 30 lbs (pressure I use for the street) the 315 will grow some over the M/T off wheel measurement. I can say that the 315 is huge compared to the 305 on the car. I also removed the stiffening rib in the wheel well to keep the tire inside as much as possible because I agree that spacing the wheel out looks stupid. I’ll attach some of my comparison pictures. I can say that the results of going to the taller tire with the 2.62 gear have had some consequences. Some of the serious drag racers are reporting significant increase in driveline parts breakage when changing to the 2.62 from the 3.09. Steve Ripa has a FB post on this subject just yesterday. Tommy Peters owns the shop I work with (SRT Autoworks) went to a set of the 315-17’s on his 2.62 geared Charger and broke the trans input shaft first time at the track. Anyway.... that’s what this forum is good for. Sharing info and experiences. Here are a couple pics to try to show the difference between a 28” tall tire and the 315-17
when on the car.

 

[hellno]

Hell I just called THOR and put the hammer down on mine 😂

 

[motorhead]

Did anyone else notice the sound deadening material in pic 2 and 3 ? Looks the same as 1970 that stuff will hold water and rot out your car. I think I am going to pull all that crap out this weekend.

Research the rust issues in the rockers and leading edge of the quarter panels from the expanding foam - I am going to Krown the crap out of that internal area this spring.

 

[Micah-OST Dyno]

Thanks for that info Micah. The measurements I was giving was from me measuring with a tape on my car. Maybe inflated to 30 lbs (pressure I use for the street) the 315 will grow some over the M/T off wheel measurement. I can say that the 315 is huge compared to the 305 on the car. I also removed the stiffening rib in the wheel well to keep the tire inside as much as possible because I agree that spacing the wheel out looks stupid. I’ll attach some of my comparison pictures. I can say that the results of going to the taller tire with the 2.62 gear have had some consequences. Some of the serious drag racers are reporting significant increase in driveline parts breakage when changing to the 2.62 from the 3.09. Steve Ripa has a FB post on this subject just yesterday. Tommy Peters owns the shop I work with (SRT Autoworks) went to a set of the 315-17’s on his 2.62 geared Charger and broke the trans input shaft first time at the track. Anyway.... that’s what this forum is good for. Sharing info and experiences. Here are a couple pics to try to show the difference between a 28” tall tire and the 315-17
when on the car.

See below. This is a worn 305/45/18 next to a 315/50/17. Both are mounted and at the same tire pressure (18psi). The 315 is negligibly taller than the 305. Be careful what you read on the internet. I haven't seen the posts you mentioned but I have to believe the cars mentioned are breaking for other reasons.

We have been racing our shop car nearly every weekend for four years and every pass, change, DA, etc. is documented in a spreadsheet. We have certainly broken axles and driveshafts but every time it has been from wheel hop and on the 305. We went to this tire to prevent wheel hop and for the last few months of last season we went to every rental, test and tune, and event we could and did not break a single part. I'd like to think the tire change was successful in preventing failures.

 

[hellno]

I disagree that 315 broke my axle because no way my 650 whp did it , that’s my story and I’m sticking to it but on a side note @Marc W I agree you are right the 2.62 is definitely harder on the drivetrain with the 315 , the 3.09 will definitely help in that area to alieve some of the stress

 

[Hpindy]

On a side note which 3.09 differential is better ? The demon or the scat pack?

Sent from my BBF100-2 using Tapatalk

 

[Mean Cat]

We recently completed another 315 tire install at the shop. This time we took some pictures so we could share how we do it and help those looking to do the same thing.

The 315/50/17 tire is a relatively new tire from M/T and a great step between the 305/45 and a 15" conversion. However, the cars we see with these tires almost always have a large spacer to help the tire clear the inner wheel well. This does the job but in our opinion it makes the car look pretty silly. Our approach is to modify the inner wheel well to clear the section width of the tire and keep everything inside the factory quarter panel.

This is what the wheel well looks like from factory.

This is the area we modify. It gets pushed in and smoothed out.

We then prep, mash, and color match paint the area.

Finally the fender liner is cut and reinstalled.

The finished product is a tire that doesn't rub, doesn't stick out, and keeps the car looking clean and professional.

Looks good , I did the same thing , I really like the 315 with the 309.

 

[Primetime Hellcat 17]

I had to do some pounding to that rib that sticks out as well to clear the 315 big boy tire. It was easy.
Just had to cut away some of the wheel liner to see the rib. Then I bought some spray paint to paint we’re I pounded away. Turned out pretty clean. My car is black so it was easy to color match it.
I used a 8lb small sledge hammer.
Was told how to do it from another member in here. He was super helpful.

 

[16GoManGoHC2]

I still can’t take a hammer to my car, my 315/50-17’s will just see track duty and I doubt anyone is going to notice 12 mm of extra stick out from the spacers I made so they don’t rub the rib. Nice write up though