Trying 275/40/17s all around on a '70

70vert · Jun 21, 2005

Hey all,
With much searching for info, checking the dodgestang chart, and a related thread on 69stang.com, I'm going to go ahead and try to fit 275/40/17 Bridgestone RE750 tires all around on Edelbrock 454s on my '70 convertible. The things that convinced me that this should work:

-SitDown and iskwezm said 275s would fit on a 17x8 rim. ;-)

-I'm dead set on the 454s and want the fattest rubber I can get

-Trans-Am Boss 302s had wider rubber up front and back

-I have R&P and a reduced turning radius

-I can always roll the fenders if need be

I went to Costco today and I had been looking on their site at the RE750s. Well, they had a $60 off sale if you buy the tires before June 25th and they just happened to have a set there that an employee bought and changed his mind on.
I don't have the wheels yet, but my plan is to mount 2 tires, try them on the front and if they don't work return them and swap for something smaller. They said they can be returned if they are not driven.
If anybody can see any problems with this, let me know. I'm pretty sure they'll work in back but not sure what the front will look like.

Joe

iskwezm · Jun 21, 2005

That back should be easy,the fronts are a different story,esecially if its lowered.Good luck

bnickel · Jun 22, 2005

must have picks when you're done. i'm betting it won't be too hard, good luck

Bullitt · Jun 22, 2005

you can put a 275 on an 8" wheel, but it's really not ideal. the sidewalls are going to stick out quite a bit. the tires also won't have a real "sharp" feeling to them that you'd experience if they were mounted on the right size wheel.

of course, the only experience i have related to this is with 275 hoosier race tires on 17x8s...

grego37 · Jun 22, 2005

I agree with the above.
17x8 not wide enough for a 275.

I wouldnt focus on having the same size all around. You have allot of room in a 69/70 out back for 275 or even 295 with the correct backspacing.
But up front, 245 seem like the max to me , unless you put flares on it.
Do you know what your backspacing is?

mattrod70 · Jun 22, 2005

do they offer the 454 in a 17x9? if they do that would be a much better way to go for all the reasons bullit mentioned. you can definately fit them in the back and if you think you can fit the 275's in the front a little massageing and the right backspacing they should be ok.

now that i think about it there used to be a guy on here with a 69 mach who had 17x9 cobra r's all the way around. does anyone remember him? it was red and he was gonna put a quickchange in it, think it had an aod? well whatever

my .02
matt

70vert · Jun 22, 2005

I went to corner-carvers on this, great discussions

grego37 said:
I agree with the above.
17x8 not wide enough for a 275.

I wouldnt focus on having the same size all around. You have allot of room in a 69/70 out back for 275 or even 295 with the correct backspacing.
But up front, 245 seem like the max to me , unless you put flares on it.
Do you know what your backspacing is?

Backspace is gonna have to wait until tomorrow when I order the wheels from UP or customwheelsdirect.
There are a range of opinions, but the general consensus is that the closer the tire section width is to the rim diameter the faster turn-in you will get - the sidewall won't flex - and the wider, the more flex but the cushier the ride and the greater the ultimate traction. I understand at least in part that the tire will "cup" slightly but you still get most of the benefit of the wider tire. One guy on the CC site had this to say:

"I have a set of 275/40/17 Hoosier's that Chris Lindbergh gave me off his Bullit Mustang that he ran on 17x8 rims in F stock. Chris took 3rd at Nationals on these tires this year, so they seem to work pretty well. The tire design is interesting though in that they have an offset built in to the sidewall that allows them to run with a narrower rim"

I want traction out back especially, (duh) so the 275s there should help me on launches and in turns. I could go smaller on the front, but I shouldn't be shooting myself in the foot if I just mount 2 of the tires and try them on the front for giggles, then switch them to the back if/when they rub and return the other tires to costco for narrower.
The thing I don't get is that the racing Trans-Am Boss 302s had 11.5" rubber up front (292mm) and rears had 12" (304mm). They were lowered. Did those wheels have monster backspace? Were the fenders rolled? Hard to tell from race pics.
If I wasn't stuck on the Edelbrock 454 wheel I would go with wider wheels, but that's my limiting factor here. There is a guy named robbiedogg on 69stang.com that is running these in a 255 width on his '69 sportsroof, so I have a PM to him to see what he thinks.

Thanks,
Joe

iskwezm · Jun 22, 2005

grego37 said:
I agree with the above.
17x8 not wide enough for a 275.

I really dont see a problem with a 275 on a 8" wheel

70vert · Jun 22, 2005

site w/69-70s with Edelbrock 454s

been spending way too much time on this today on my day off. here are all the photos I could find on the web of '69-70s with these wheels:

http://homepage.mac.com/jbauder/PhotoAlbum68.html

man iskwezm, you certainly do skwezm. That tire doesn't rub the fender??

iskwezm · Jun 22, 2005

70vert said:
man iskwezm, you certainly do skwezm. That tire doesn't rub the fender??

only when I drive it

12sec67 · Jun 22, 2005

iskwezm said:
only when I drive it

i was going to ask the same thing

looks bad a$$ though.... really like the matching jack stands

bnickel · Jun 22, 2005

70vert said:
Backspace is gonna have to wait until tomorrow when I order the wheels from UP or customwheelsdirect.
There are a range of opinions, but the general consensus is that the closer the tire section width is to the rim diameter the faster turn-in you will get - the sidewall won't flex - and the wider, the more flex but the cushier the ride and the greater the ultimate traction. I understand at least in part that the tire will "cup" slightly but you still get most of the benefit of the wider tire. One guy on the CC site had this to say:

"I have a set of 275/40/17 Hoosier's that Chris Lindbergh gave me off his Bullit Mustang that he ran on 17x8 rims in F stock. Chris took 3rd at Nationals on these tires this year, so they seem to work pretty well. The tire design is interesting though in that they have an offset built in to the sidewall that allows them to run with a narrower rim"

I want traction out back especially, (duh) so the 275s there should help me on launches and in turns. I could go smaller on the front, but I shouldn't be shooting myself in the foot if I just mount 2 of the tires and try them on the front for giggles, then switch them to the back if/when they rub and return the other tires to costco for narrower.
The thing I don't get is that the racing Trans-Am Boss 302s had 11.5" rubber up front (292mm) and rears had 12" (304mm). They were lowered. Did those wheels have monster backspace? Were the fenders rolled? Hard to tell from race pics.
If I wasn't stuck on the Edelbrock 454 wheel I would go with wider wheels, but that's my limiting factor here. There is a guy named robbiedogg on 69stang.com that is running these in a 255 width on his '69 sportsroof, so I have a PM to him to see what he thinks.

Thanks,
Joe

the ta boss 302's had flared fenders and some even had "mini-tubs" but not so much like we think of them today, basically they would section the wheelwells so they were flatter at the top, but not necessarily all that much wider, that way they could fill the existing wheelwell with as much rubber as they could possibly fit without rubbing when the suspension compressed, also since the fenders were slightly flared they could move the tires out as far as possible increaing the overall track width of the car, they did some sneaky stuff back in those days. i've read stories about how on the penske camaros had the body acid dipped so much that the roof literally collapsed when one of the tech inspectors leaned on it.

iskwezm · Jun 23, 2005

12sec67 said:
i was going to ask the same thing

looks bad a$$ though.... really like the matching jack stands

Well its off the stands now and moves under its own power

jbuening · Jun 23, 2005

My buddy's 69 Boss 429 has BFG 275s all the way around on Magnum 500s. Yes they did have rolled fenders but it wasn't tubbed or anything. This was on 15x8" rims with the usual old school backspacing. Can't help much on the larger rims with more backspacing. You can always add spacers if they rub the suspension in the front.

70vert · Jun 23, 2005

Finally figured out backspace

I emailed the guy on that photo of the red '70 on the web page I put up above. He is "Bossy '70" on cardomain.com and he seemed to recall that the backspace was 4.5. I called up both customwheelsdirect and Unique this morning and both were backordered. Customwheelsdirect was going to have them sooner and they were cheaper, (and didn't require it to be PAID IN FULL 2 MONTHS BEFORE THEY SHIP like their competitor, so they get my business.

cardomain.com is awesome for mustang photos btw.

Trying 275/40/17s all around on a '70

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