Dumb tire size question - but ask I must

[foothilltom 33]

Hi gents,

 

I've searched through previous posts about wheel/tire size and it seems everybody is putting huge wheels on their Mustangs. I have much more modest requirements, but still I think I've managed to screw up. Hoping you can help a brother out.

 

Bought 14x7x4.5" wheels from Summit Racing. They're neat. So far, so good, according to what I've read so far.

 

I put 235 60 R14's on these wheels and DANG IT if they tire doesn't rub on the front suspension (the control arm or whatever that is). There seems to be plenty of room in the rear, but the fronts rub. The original crappy tires are 205 70 R14s and even they have *barely* any room between the inside of the tire and the suspension.

 

Have I hosed myself? I was trying to understand "back spacing", but can't really say I do at all. Is there a different wheel hub I need? Tires just too big?

 

The boy is looking at me with that sad face again...so close and yet so far.

 

Thanks for your kind help!

 

Tom

[69RavenConv 286]

Maybe this can help?

 

http://clubs.hemmings.com/clubsites/chevylist/tech/tire_size_conversion.htm

 

You'll get a zillion different opinions on wheel & tire sizes, and most will be much more knowledgeable than me. But I think the factory original was 7.35-14 (E78-14) which looked dorky-skinny even back in the day. E70-14 or F70-14 was a good upgrade. You've got the equivalent of F60-14's. From the chart, maybe 225/60R14's would be a better fit? Or, like you say, use spacers behind the rim. Somebody smarter than me will tell you how to make yours work.

[Pakrat 1,043]

Basically your issue is too much backspace and a little too much tire Tom. For a 7" rim that small you really don't want anymore than 4.25", 4" is an even better fit. Your 4.5" is better suited to an 8" rim. Take a look at this simplified wheel chart, this is not max limits like the dodgestang charts show, these are much more concervative. They don't list 14's but you'll see the same BS on all the 7" rims.

 

 

I have/had stock 14" SSW rims on my car (actually will be for sale this spring) and I am pretty sure they are a 4" BS, I ran 225-70R14's on them with no issues at all and no rub. I know between two cars you have a lot of extra rims lyinng around, lay one flat on the ground face down, place a straight board across the back and measure down to the hub, that is what your current backspace was and I would be surprised if it was much more than 4".

[foothilltom 33]

Hey Pak, I think I'm starting to get this.

 

The backspacing on my new Cragar 14"s is 4.25". The 235 60's rub like no tomorrow as I've said on these rims.

 

The BS on the donor rims is 3.75" and they have 215 60's mounted. They fit with about 1/2" (maybe a bit more) of clearance from the nearest thing that will rub (don't know what it's called, but it's the suspension piece that attaches to the wheel itself with a trailer-hitch-looking knob.

 

So, according to the chart above, 15x7's with 4.25" BS *should* fit 225s, which makes me wonder what the maximum should be for 14x7's.

 

But if I just apply some public-school math, I have 1/2" difference in the BS between the old and new rims and what looks like just over 1/2" of clearance with the 215s mounted on the old rims. If I install 215s on the new rims with 4.25", it should just fit, with a little bit to spare.

 

Does this reasoning sound pretty solid?

 

Finally, did I hose myself by buying 14"x7" wheels in the first place? I was trying to AVOID rubbing/fit problems, but it appears I've actually created them. Whooda thunk that?

 

Thanks for your last follow-up here, Pak.

 

Tom

Edited October 20, 2008 by foothilltom

[cphsonic 11]

Your fix, besides buying more rims, could be a quality spacer. Try http://www.skulte.com/index.php/cPath/21?osCsid=b0c1022ae55227d3c5f9054019fcbd10

[Pakrat 1,043]

Hey Pak, I think I'm starting to get this.

 

The backspacing on my new Cragar 14"s is 4.25". The 235 60's rub like no tomorrow as I've said on these rims.

 

The BS on the donor rims is 3.75" and they have 215 60's mounted. They fit with about 1/2" (maybe a bit more) of clearance from the nearest thing that will rub (don't know what it's called, but it's the suspension piece that attaches to the wheel itself with a trailer-hitch-looking knob.

 

So, according to the chart above, 15x7's with 4.25" BS *should* fit 225s, which makes me wonder what the maximum should be for 14x7's.

 

But if I just apply some public-school math, I have 1/2" difference in the BS between the old and new rims and what looks like just over 1/2" of clearance with the 215s mounted on the old rims. If I install 215s on the new rims with 4.25", it should just fit, with a little bit to spare.

 

Does this reasoning sound pretty solid?

 

Finally, did I hose myself by buying 14"x7" wheels in the first place? I was trying to AVOID rubbing/fit problems, but it appears I've actually created them. Whooda thunk that?

 

Thanks for your last follow-up here, Pak.

 

Tom

 

So were the new rims actually listed on the summit site as 4.25 or is that just the measurment you got? I can't help but feel that they are really 4.5" just because of the issues you have. As you can see by the dodgestang chart there are not many running 14" rims these days the ones there don't have issues with their BS/Tire combo or at least they shouldn't, some people live with a little rub though. http://www.dodgestang.com/emAlbum/albums/Tire%20and%20Wheel%20Charts%201965-1973/Tire%20and%20Wheel%20Chart/Tire%20Fitment%20Guide%2069-70.pdf

 

I don't think you hosed yourself unless you actually have to buy spacers too. I'm not a fan of them but sometimes they are necessary when you aren't doing a custom BS and need to make something work. As a general rule to remember the idea is to keep the wheel centered so every extra 1" of wheel is an extra 1/2" of BS, then you have the plus or minus factor to either tuck them in more if you are really lowering the car or to make them stick out past the fender when you need more rubber than you can fit inside. That's why 17" rims are getting so popular on the older cars now, they are tall enough to clear over that ball joint you rub into so you can now tuck them in more and go wider up front.

 

Try using a bunch of washers or some home made spacers just to be able to turn the wheels on jackstands and see what the minimum spacing is needed for your set up now. Something will obviuolsy have to change wether it be narrower tires, exchanged rims or purchase spacers.

[bnickel 10,004]

i have run a 15X7 wheel on the front of my stang with close to the same backspace (maybe 4.75") and had the same issue. i used a 3/8" Mr Gasket spacer to move the wheels out enough to clear the upper control arm and ran them like that for many years. it would be wise to use 1/2" longer wheel studs though i didn't on mine and had no issues.

[foothilltom 33]

Thanks for all the info, fellas. The boy and I just now have to decide if spacers are in the cards or if he can live with the smaller meats. As always, I've learned a lot and I hope I can pay it forward.

 

Tom