[AdamIsAdam]

Does anyone know which would have more launch traction on the street: 275/60 or 255/60 both in 15". Right now I'm only talking about BFG Radial T/A.

I have brand new 275s and they make the car sit kind of high out back and rub slightly on the passenger side with a loaded car, so I'm considering a change.

I have 225/60 up front so I could go 225/70 to reduce the rake. I just hate the idea of raising a car in general.

Note: I have drag radials for the track. This question is for regular street use.

Opinions wanted.

http://i300.photobucket.com/albums/n...O/IMAG2901.jpg

[The Champ]

Your current setup (275/225) gives you about a 1 and a quarter inch rake.

275's are 28" tall. 255's are 27.1" tall. The 255's would lower the rear about a half inch.

225/60's are 25.6" tall. 225/70's are 27.4" tall. That's a dramatic change - about a 1 inch lift.

I would suggest a 235/60/15 up front - 26.1" tall.

A 235 front/255 rear would end up with about a half inch rake.

As far as street launch traction goes - a shorter narrower tire most likely won't help with a 469 with 3.42 gears.

[Formulajones]

You have a pretty short 225/60 tire on the front which is where the big difference is coming from.

2 ways to do it, install 255/60's on the rear and keep the 225/60's in the front, or install 225/70's on the front and keep the 275/60's in the rear. Either way is roughly half inch difference that is hardly noticable with the naked eye. If you want them perfect in regard to height front and back. 255/60s on the rear and 225/70's on the front would work.


Personally I prefer the tire to take up wheel well space, so I prefer the 28" tire in the rear, and I always run a 225/70 or a 205/75 (both 27.1" tall) in the front to keep the front tire height close to the rear. A slight rake doesn't bother me but that difference isn't all that noticable and my cars sit pretty level with this setup. Have several here with that exact setup if pics would help.

It's all personal preference.

[AdamIsAdam]

Originally Posted by Formulajones

You have a pretty short 225/60 tire on the front which is where the big difference is coming from.

2 ways to do it, install 255/60's on the rear and keep the 225/60's in the front, or install 225/70's on the front and keep the 275/60's in the rear. Either way is roughly half inch difference that is hardly noticable with the naked eye. If you want them perfect in regard to height front and back. 255/60s on the rear and 225/70's on the front would work.


Personally I prefer the tire to take up wheel well space, so I prefer the 28" tire in the rear, and I always run a 225/70 or a 205/75 (both 27.1" tall) in the front to keep the front tire height close to the rear. A slight rake doesn't bother me but that difference isn't all that noticable and my cars sit pretty level with this setup. Have several here with that exact setup if pics would help.

It's all personal preference.

I tend to agree with you and was also considering the 225/70 up front. Pics would be great if you have them handy. I like a slight rake, like I have when my 275/50x15's are on, but those are drag radials so I don't want them on there all the time. (Although I love the better performance I get off the line -- remember, I have a M21 and 3.42, not ideal combo. The flip side of that coin is that I like being able to cruise on the highway comfortably with the 275/60's now. 55@2,500 RPM is great and 70 comes in around 2,900 as I recall.

Here's a pic with the 275/50's:

http://i300.photobucket.com/albums/n...1.jpg~original

[78w72]

i like the bigger tire on the back too, fills the wheel well & looks better. the 225/60 up front is a very short tire & makes the rake a little too much IMO. the car looks great but i think a taller front would give it a better stance. 225/70 or step up to a 235/60 up front if you keep the 275 rears. if you want the rear smaller & not rub etc, then a 255/60 would be best & decide what you prefer on the fronts.

as for street traction, i'm pretty sure a wider tire will give better traction vs a thinner tire. keep in mind a shorter tire will lower your final gear ratio & increase highway cruise rpms.

[Formulajones]

Originally Posted by AdamIsAdam

I tend to agree with you and was also considering the 225/70 up front. Pics would be great if you have them handy. I like a slight rake, like I have when my 275/50x15's are on, but those are drag radials so I don't want them on there all the time. (Although I love the better performance I get off the line -- remember, I have a M21 and 3.42, not ideal combo. The flip side of that coin is that I like being able to cruise on the highway comfortably with the 275/60's now. 55@2,500 RPM is great and 70 comes in around 2,900 as I recall.

Here's a pic with the 275/50's:

http://i300.photobucket.com/albums/n...1.jpg~original

I agree, as I also manipulate my cruising rpm with tire height so it's also a part of my decision making. The 28" tire with 3.42's make a nice highway cruiser in my opinion and good "all around" performance, I use this tire height with 3.73's in a couple cars and they cruise on the highway at 65 mph/2800 rpms and it's just fine for me. Yeah an M21 with 3.42's is boarderline around town but not horrible. I'd like to see an M20 with that combo but we use what we have .

Those 275/50 drag radials are 26" tall, and since the drag radials are used at the strip the shorter tire will certainly help the gear situation out (2.20 1st and 3.42's) so I like that thinking.

I have pics of various cars, however not all pontiacs since I tend to collect other brand X stuff. If you don't mind that I'll post a couple. All with different styles of wheel well openings, some more open or larger than others has a pretty drastic affect on appearances with tire height.

[AdamIsAdam]

Originally Posted by Formulajones

I agree, as I also manipulate my cruising rpm with tire height so it's also a part of my decision making. The 28" tire with 3.42's make a nice highway cruiser in my opinion and good "all around" performance, I use this tire height with 3.73's in a couple cars and they cruise on the highway at 65 mph/2800 rpms and it's just fine for me. Yeah an M21 with 3.42's is boarderline around town but not horrible. I'd like to see an M20 with that combo but we use what we have .

Those 275/50 drag radials are 26" tall, and since the drag radials are used at the strip the shorter tire will certainly help the gear situation out (2.20 1st and 3.42's) so I like that thinking.

I have pics of various cars, however not all pontiacs since I tend to collect other brand X stuff. If you don't mind that I'll post a couple. All with different styles of wheel well openings, some more open or larger than others has a pretty drastic affect on appearances with tire height.

Exactly my thinking on everything.

Yes, if you don't mind posting pics, thanks

[Tom Vaught]

How much clearance with the wheel lip at the rear of the front fender do you have with the different front tires? Back spacing on the Cragers (front and rear)?

Very pretty car.

Color looked good on OMT's 64 and looks good on your car.

Tom V.

[psw]

Love the color and wheel combo too! ;>)

[BILTIT]

IMO, neither. Those BFG tires have very little usable traction on the street. I was running 295/50 and they still couldn't hold a lick down.

Why not run the drag radials on the street? I even found them to be lacking a bit but much better than the bfg's. I went to 13.5 wide et streets to make it bite on the street, overkill at the track but really helps otherwise.

[Formulajones]

This took a bit of digging since it seems I don't really have perfect pictures that would depict how the tires fill wheel wells, pics seem to be at angles or not perfectly level ground but at the risk of being too much, maybe this will help some. They likely won't stay up too long since I have technical issues with photobucket I have to figure out.

My firebird with 275/60 rear and 225/70 front. The slightly taller rear tire really doesn't seem to affect the ride height on this car. This car is largely unrestored and still has it's original 44 year old springs. Wheel wells on these cars are HUGE so I felt the car really needed 28" tires to take up the space.


My chevelle with 275/60 drag radials and a 205/75 front tire. I run the drag radials full time as street tires are useless and a bit dangerous with this one on the street. It sits very level as well although the pic isn't very good, best I have from the side I think where the tires are most visible


Here's my fathers car with 295/65 drag radials (30" tall) on the rear and a much shorter 205/75 on the front. Sits very level, but that was achieved with more front spring mainly to gain ground clearance for the oil pan and headers dangling down. Probably not what you want to get into on yours.


Here are a couple of 14" combo's I have thrown in the mix. This is an original unrestored 71 Sprint with it's original 14" wheels and an oddball mix of front/rear sizes. 235/60's rear and 205/70's front. This is a situation where the front tires are actually taller than the back, and I would have rather had more tire on the car but didn't want to ditch the 14's, so choices were limited. This car actually sits fairly low in the rear with original saggy mono-leafs so the front sits a tad higher, but this pic doesn't show it.


This is one of the mustangs I have, also all original and unrestored with it's original 14's. In this example a set of original F70-14's all the way around that are 26" tall. Over the years the front springs have sagged a bit with that heavy FE so the rear of this car actually sits just a tad higher. I actually like the looks of it when the trunk is loaded squatting the back to a more level stance where the top of the rear tire is parallel with the wheel lip, then these little 14" tires actually do a decent job of filling the wheel wells. An example of a not very large wheel opening where 14" tires work fairly well in appearance.

[AdamIsAdam]

Thanks fellas. Fjones, NICE COLLECTION! That Chevelle looks like a beast.
I want the BFG's for the street for looks mostly. Plus I like that it's easy to smoke `em. It's the only kind of smoking I do with the kids ;-) Plus I figure it's easier on my drivetrain to have tires that are slippery a bit.


Rear rims with Summit part numbers are:
CRR-61C583442
Wheel, 61C S/S Super Sport, Steel/Aluminum, 15 in. x 8 in., 5 x 4.75 in. Bolt Circle, 4.250 in. Backspace
(Mfr. #: 61C583442)

Front rims are:
CRR-61C573440
Wheel, 61C S/S Super Sport, Steel/Aluminum, 15 in. x 7 in., 5 x 4.75 in. Bolt Circle, 4.000 in. Backspace
(Mfr. #: 61C573440)

I gotta run, but I'll continue this post later. Dinner calls...

Thanks again.

[AdamIsAdam]

Originally Posted by psw

Love the color and wheel combo too! ;>)

What color is yours? Mine is viper blue.

I'll measure the current front wheel well clearance Monday.

I'm inclined to get the 225/70 fronts. I'll mount the current fronts on my weld wheels again.

[66beaumont]

66 Pontiac Beaumont with 215/65 r15 on15x7 and 255/60r15 on15x8

[AdamIsAdam]

Anyone have pics of first gen GTO with 225/70 up front? I think that's my answer.

BTW, As I mentioned, I like the look of BFG with raised white letters on this car. And while I don't mind running drag radials on the street, I tend to drive my cars and don't want to wear them out so fast.

[Jim Doran]

Adam, here is a pic of my 65 with 225/70/r14 BFG upfront and 245/60/r14 out back.

[AdamIsAdam]

sweet looking car! Love the color. And I like the wheel/tire combo. But I see those are 14's, so that'll be a little different. But wow, that's a nice looking car, Jim.

Anyone else?

[unclescratch]

Here is my set-up with 275x60x15 on 15x8 rims out back and 215x75x15 on 15x5-1/2 rims on the front. My 4-foot level on the frame rails says my car is 'level !

For more launch on the street (or strip), with the same aspect ratio '60', the 275 tire will give you a greater contact patch and more chance for traction.

[unclescratch]

from the other side:

[AdamIsAdam]

I just wanted to add another pic. Can you all tell if there's a difference in rake now as compared to my earlier posted pic of the passenger side? (only difference is tire PSI - in reduced rear PSI from 30 to 25 (and i'm still barely getting all the tire on the ground) and increased the front to about 35PSI.

[img][/img]