I am doing a frame off resto on a 68 SS and just bought Heidt's bolt in 4 link rear suspension/ford 9" combo. Since this setup uses adjustable coil overs, will I be able to fit any larger tires under the rear end? I love the sticky showing all the different wheels/tire combos on you guys' rides and the trend shows that a 275 tire fits on a stock setup. Anybody have this set up for some help here???? I also just found in Summit Racing that Percy's makes a fitment tool for under $100 that tells you tire size as well as backspacing. Anybody use of these and is it worth $100? I don't want to keep guessing on rims/tires until I find what fits. I am putting a 850+hp 565 Dart BBC that runs on E-85, so I need the biggest tire that will fit. And they say us car nuts don't care about the environment!!!
Thanks

I see you have a gang of answers so I figured I would jump in. I have the same 4 link set up, bought the complete 9" housing and differential. I havn't seen any articles here about Heidt's setup so you might not get any answers. I dunno if the setup sucks or if it cost too many bones? Anyways I'm curiuous to see if you get any answers. My ride isnt ready for tires right now, it's in the paint shop with some stockers. My ride seemed a little low in the back so I put the bottom shock mount bolt in the middle hole of the 4 link setup. I moved it to the middle with very little clearance, the driver's side shock and the 4 link housing almost touch but the back of the car came up a bit. Just wondering where you put it? I don't have the motor or trans. in it yet either so I might be changing it.

1st question - did you check with Heidt's? I think (and I do stand to be corrected if I'm wrong) you will gain no additional room with the Heidt's 4 link. So that gets us back to the standard 275 on a 9.5 answer. With that said you can alter the width of the rear and run a deeper dish wheel (less backspace) so the "look" is bigger. As always the same rules apply to what you have to check for proper fitment including checking both sides. As far as the tool goes you can make something to measure or read the article from Chevy Hiperformance "fat on all fours". The bottom line is it's always better to test fit if possible.

Here's the link to that CHP article. http://www.chevyhiperformance.com/techarticles/72978_chevrolet_wide_tire_install/index.html

I see you have a gang of answers so I figured I would jump in. I have the same 4 link set up, bought the complete 9" housing and differential. I havn't seen any articles here about Heidt's setup so you might not get any answers. I dunno if the setup sucks or if it cost too many bones? Anyways I'm curiuous to see if you get any answers. My ride isnt ready for tires right now, it's in the paint shop with some stockers. My ride seemed a little low in the back so I put the bottom shock mount bolt in the middle hole of the 4 link setup. I moved it to the middle with very little clearance, the driver's side shock and the 4 link housing almost touch but the back of the car came up a bit. Just wondering where you put it? I don't have the motor or trans. in it yet either so I might be changing it.

My car is rolling (barely) on a dolly under the firewall and 2 space savers on the rear in the body shop. The front subframe is being blasted and powdercoated, then being reinstalled with all new factory suspension except for some tubular a-arms in with coil overs. I figure that will get me slightly more room for the 2 1/8" primary headers. As for the rear, I am pullin out my multi-leafs and existing Ford 9" in favor of the Heidt's 4 link/coil over setup. I ordered the works in hopes of getting the adjustability to hook straight. I have an email to Heidt's to ask them the same question if it would garner me any additional room, haven't received the response yet. I will get pics to post on the sticky as quick as I can.

1st question - did you check with Heidt's? I think (and I do stand to be corrected if I'm wrong) you will gain no additional room with the Heidt's 4 link. So that gets us back to the standard 275 on a 9.5 answer. With that said you can alter the width of the rear and run a deeper dish wheel (less backspace) so the "look" is bigger. As always the same rules apply to what you have to check for proper fitment including checking both sides. As far as the tool goes you can make something to measure or read the article from Chevy Hiperformance "fat on all fours". The bottom line is it's always better to test fit if possible.

thanks Jack,
I didn't know for sure but you are the 2nd person to tell me the same thing. Silly question, but what do you mean by "looking bigger", just the visual depth of the rim lip to the mounting surface? From the rear it would look the same correct? I would love to keep the 15" rallye rim look but have read several places (including the link you sent) that the larger sidewall bows out farther and can make clearance more difficult. It is interesting to see how the different manufacturers list the sec width and tread width. Some 275 tires have a wider listed tread width than some 295 tires. I ran a 295/50/15 BF Goodrich Comp TA forever, but the rear end of the car was taller and the tire didn't really fit "under" the car, more sticking out from it. The rims that came on the car didn't have the correct backspacing or the 9" housing wasn't cut down to the correct size but either way it didn't look right. Thank you for the help.

thanks Jack,
I didn't know for sure but you are the 2nd person to tell me the same thing. Silly question, but what do you mean by "looking bigger", just the visual depth of the rim lip to the mounting surface? From the rear it would look the same correct? I would love to keep the 15" rallye rim look but have read several places (including the link you sent) that the larger sidewall bows out farther and can make clearance more difficult. It is interesting to see how the different manufacturers list the sec width and tread width. Some 275 tires have a wider listed tread width than some 295 tires. I ran a 295/50/15 BF Goodrich Comp TA forever, but the rear end of the car was taller and the tire didn't really fit "under" the car, more sticking out from it. The rims that came on the car didn't have the correct backspacing or the 9" housing wasn't cut down to the correct size but either way it didn't look right. Thank you for the help.
With less backspace you will have a deeper dish on the the wheel (looks more dramatic especially with a "flat lip" wheel). Now on a Ralley wheel it will not have the same visual impact. Yes from the rear a 275 tire on a 9.5 wheel (or what ever size tire and wheel) will look the same no matter what the backspacing is (but depending on ride height and eye level how many times will you or your car's admirerers be looking at the rear of the car from directly behind it?). Since you are changing the rear and you haven't bought your tires/wheels yet the opportunity is there to create a little bit different than the standard look by using deeper dish wheels. Different not better or worse. Good luck with what ever you decide.