To 315 or not 315

[project hotrod]

I've been crunching numbers between tire combinations for the Malibu and I fail to see a large advantage going through the work to fit a 315 in the wheel well.

Against a 275 tire I would only gain 1.7" more tread width and would need to run a heaver 11" wheel opposed to getting away with a 9.5"

Sidewall thickness and overall diameter are within .01 between both too.

Not mentioning all the work and cost in the mini tubs and sectioning the rail for a car that will only make around 400 wheel hp.

I guess if I was more after looks a 315 would look tougher but this project is more about function.

The combination which I think will offer the best fitment, and performance would be.

rear
275-40-17 (9.5" wheel) dia 25.6" - tread 9.8" - sidewall 4.3"
front
245-45-17 (8.0" wheel) dia 25.8" - tread 8.3" - sidewall 4.4"

I know I have a greater overall on the front by .2" but I think going to a 245-40-17 with a overall dia of 24.72 would be too small.

Would anyone care to share an opinion on this or validate my theory considering my experience is drag racing?

I would greatly appreciate since I'm close to pulling the trigger on tires and wheels.

[68Formula]

A 315, looks killer no doubt.

As far as traction, the more tire on the road the better. However, I've heard people say that you want your front/rear sizes within 40mm or so to balance handling (of course that varies car to car due to the thousands of other factors affect handling balance).

Also, as you said, mini-tubbing is a slippery slope. Things that need to be considered i addition to the tubs themselves (depending on vehicle model):

• Narrowing the gas tank
• Notching (or removing completely) the rear seat for clearance
• Rearend suspension changes (for leafspring, offsetting the mounting, think most of the aftermarket 3 & 4 link setups are designed with tubbing in mind)
• Narrowing the rearend (you could adjust by using wheel offsets, but to me the deep dish look is part o f the bad @$$ you get with mini-tubbing)
• Exhaust modification

I couldn't justify the cost in all this for myself, so I jammed in what fit.

BTW, you meant 245/45R17 for the front, right?

[project hotrod]

Thanks for the reply.

My initial tires chosen are ZR rated but yeah. 245/45/17 on the front is what I'm thinking.

To me, if the work and money = a large increase in ability I have no problem putting a 315 under it. ie: seconds off of lap times rather than tenths since I won't be competing on a serious level.

I'll be using a 3-link with a watts so I don't have to worry about exhaust, backseat, and so on... I'll also be using a fuel cell so the clearance issues are moot... The problem is I haven't found any imperical data supporting just how much better the 315 would handle over the 275 or even a 285 for that matter.

Regarding your 40mm rule of thumb: With a 275 / 245 combination I have a difference of 38.10mm which should be fine.

It's kind of funny but the decision on tires decides quite a bit of the build, and purchase order of parts depending on the choice.

[Damn True]

You can always put on a smaller tire once the car is finished if you find it difficult to attain balance. Putting on larger tires after the fact would be far more difficult.

[project hotrod]

You can always put on a smaller tire once the car is finished if you find it difficult to attain balance. Putting on larger tires after the fact would be far more difficult.

I'll just cut the wheel wells ala Street stock roundy round cars. lol

[86Cutlass383SR]

Kevin I'm in basically the planning stages for my 86 Cutlass and I've mentally battled that same question. 315 would look cool...but between the frame notch and mini-tubs plus whatever else I run into, the 315's just aren't worth it to my build.

Another factor in my decision is the fact that I plan on making some lengthy road-trips *if* I ever get mine road worthy. The question in my mind is, if I cut a tire and need a replacement, what's the chance of finding a tire dealer with a 315 vs a 275? I'd think a 275 would be slightly less difficult to find. I may be wrong.

[Samckitt]

I have 275's out back with 245's up front. I too want to put 315's out back mainly for looks but seems a lot of work just for the look.

[68Formula]

The question in my mind is, if I cut a tire and need a replacement, what's the chance of finding a tire dealer with a 315 vs a 275? I'd think a 275 would be slightly less difficult to find. I may be wrong.

The 275/45R17s were used on factory Camaros, Firebirds, and other makes. It's a common OEM performance size tire, so replacements are readily available.

[JRouche]

I ended up with a 275 mainly due to wheel selection. I wanted 315mm tires but no 11" wheels in a soft lip hoop. Custom sure, add 400 a wheel. So I went with 10" billet specialties and GY F-1's in 275. They look ok. (62 Nova) ALOT of tire choices in 275.. JR

[dlrepmn]

315's just for looks, yes. That's true. But you have to admit they look pretty good.



Is it worth the grief and expense? You have to decide. To get a decent size tire on an F-body you have to mini-tub. You are at pretty good size without it. Don't forget you have to modify your rear seat frame as well with the mini-tub.

Looking at JR's you have a tough time telling between a 315 on a 12" rim and a 275 on an 10" rim. I'm sure if you looked from directly behind the car you could, but would you find a tremendous difference in performance unless you were on a track?

I have a 400HP motor, but I didn't have a choice if I wanted decent sized meats. You do.

[JRouche]

Looking at JR's you have a tough time telling between a 315 on a 12" rim and a 275 on an 10" rim. I'm sure if you looked from directly behind the car you could, but would you find a tremendous difference in performance unless you were on a track?

Ummm, I screwed up. They are 285 tires Not much diif though from the 275. Im an idiot LOL Dont even know what tire Im using LOL Oh, the GY F-1s tend to run a lil wider than some. JR

[SicMonte]

I had a 315 out back and I only had a frame notch done. The rims were 17x11 with 5.5 bs but a 6.0bs would have been better.

Have you ever thought about going for a 305?

[syborg tt]

I'm sorry i disagree - they look great.

I ended up with a 275 mainly due to wheel selection. I wanted 315mm tires but no 11" wheels in a soft lip hoop. Custom sure, add 400 a wheel. So I went with 10" billet specialties and GY F-1's in 275. They look ok. (62 Nova) ALOT of tire choices in 275.. JR

[SS1156]

The problem with 315's is there aren't many tires to choose from. I have a 96 Camaro SS and the factory tire is a 275/40ZR17. I was gonna put 11's on the back with 315's but there weren't enough tire choices so I left the car stock. Now that I have a 72 and I'm gonna mini tub it I have all the choices in the world. Good luck with the tire pickins. BTW, the GS -D3's look awesome on there and they are an awesome tire too. They do run large for there size.

[andrewb70]

I'd go with a 285/40-17 in the rear and 245/45-17 in the front. The 285s are just slightly taller which I think will look better.

http://www.tirerack.com/tires/Spec.j...e1=yes&place=1

Andrew

[BigBlockOlds]

I had a 315 out back and I only had a frame notch done. The rims were 17x11 with 5.5 bs but a 6.0bs would have been better.

Same here. Although I have a 6" BS and I did move my stock wheel wells in just a touch (maybe 1" or so). But the rear seats and trunk hinges still fit.

[DAK]

I'd go with a 285/40-17 in the rear and 245/45-17 in the front. The 285s are just slightly taller which I think will look better.

285's on the left. I had 275's on the back of my car for a fews yrs and a taller tire would fill the wheel well nicer. I didn't realize how much bigger the 285's were over 275's but I hope they fit.

[JRouche]

285's on the left. I had 275's on the back of my car for a fews yrs and a taller tire would fill the wheel well nicer. I didn't realize how much bigger the 285's were over 275's but I hope they fit.

Wow!!! Thats really odd. Are those 275s on the right. There should only be a total of LESS than one inch (more like .800") for the whole stack. Im I losing my mind, yeah, yeah, I did find it again, but I swear its on the way out again. Tell me they are not 275s on the right? JR

[Throttle]

315's just for looks, yes. That's true. But you have to admit they look pretty good.



Is it worth the grief and expense? You have to decide. To get a decent size tire on an F-body you have to mini-tub. You are at pretty good size without it. Don't forget you have to modify your rear seat frame as well with the mini-tub.

Looking at JR's you have a tough time telling between a 315 on a 12" rim and a 275 on an 10" rim. I'm sure if you looked from directly behind the car you could, but would you find a tremendous difference in performance unless you were on a track?

I have a 400HP motor, but I didn't have a choice if I wanted decent sized meats. You do.

You can run a 315 under a real F-Body..

[syborg tt]

Wow!!! Thats really odd. Are those 275s on the right. There should only be a total of LESS than one inch (more like .800") for the whole stack. Im I losing my mind, yeah, yeah, I did find it again, but I swear its on the way out again. Tell me they are not 275s on the right? JR

could also be 8" rim vs 10" rim