Another 'will it fit' wheel/tire thread...

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bac

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1971 Mach 1
Hi all, still not an official owner of a '71-'73 'stang yet but hope to have a '71 Mach 1 M code in a few weeks!  Have browsed some of the discussions here and elsewhere but haven't found an answer to my specific question, so here goes:

Looking to replace the 15" Magnums currently on the car with some Ridler 675 polished wheels.  Spec I'm considering is 17x8" on the front and 17x9.5" on the rear. Trying to keep within a couple of percent of the stock rolling diameter to minimise speedo error, so thinking 225/50 tires on the front and 275/40 on the rear.

My question is: will the 275/40s clear the fender lips or are they likely to rub?  Offset on the 9.5" rims is -5mm so by my calculation that puts the backspace at 5.05", but I've read I might need more like 5.5". I know there will be less sidewall bulge with a low profile tire but not sure if it will be OK.

Cheers,

Brian

 
Last edited by a moderator:
OK, after some more reading it seems pretty clear that for a '69-'70 you need at least 5.5" backspace to clear a 9.5" rim, but I can't find any info specific to the '71-'73s.

Does anyone know if there is more space between the axle hub and the lip of the wheel well on a '71-'73 compared to a '69-'70 and if so, how much?

Cheers,

Brian

 
Last edited by a moderator:
Something else to be aware of - with 17" rims the front wheel rim is right in line with the end of the upper A-arm - I had rubbing problems when the front end went light. Here in the UK 18" rims are a far better choice than 17s as there are almost no decent tyres for 17s that are not crazy low profile but there are many choices for 18s. However low profile tyres on leaf spring cars do give a harsh ride.

In the rear I think 5.5" backspace would be optimum with 9 or 9.5" rims. You definitely don't want much more than 4.5" on the outside. So a 9" rim (10" overall width) with 5.5" backspace will have 4.5" on the outside. If you err on this side, you could always space it out a little if required to tailor the looks.

 
Also you probably want 235 or 245 on the front!

 
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