Upgrading wheels / tires on a 73.5T

[fastricky]

Hi all, I'd like to upgrade the stock (puny) wheels and tires on my T. I'll be going from the stock 14" up to 15". I'm pretty settled on Pirelli Cinturatos CN36, but please chime in if I should reconsider that idea.

Wheels I'm looking at are Maxilite Replica Fuchs Deep 6 and 7R wheels + tires in 185/60/15 and 205/60/15.

Does that make sense? Will those sizes work without any issue? Any other thoughts? Thanks in advance - Rich

[aus911]

Hi fastricky,

Both the sizes you are targeting will fit, however the diameter of that combination is not the same. There are tyre calculators available to assist your choices, but I would consider the rears being 55 profile for a closer match

[fastricky]

Originally Posted by aus911

Hi fastricky,

Both the sizes you are targeting will fit, however the diameter of that combination is not the same. There are tyre calculators available to assist your choices, but I would consider the rears being 55 profile for a closer match

Appreciate the advice, would 185/70/15 and 215/60/15 be an option?

[aus911]

Hi Again,
Looking at your sizes they may be smaller than std, I think std for your car was 185/70r15 and 215/60 r15.
this will just change your ratios a little

Cheers
Ray

[aus911]

You beat me to it!!

[fastricky]

Ha perfect thanks again!

[aus911]

Check the rear clearance, front no problems.

[aus911]

I am sure others will chime in too.

Cheers
Ray

[HarryD]

Are you sure you want 15’s. Tire selection is very limited and performance tires are few and far between.

Factory fitment is 185/70–15. Other sizes with the same rolling diameter and ok fitment are 195/65-15 and 205/60-15.

I have moved to 6x16 Fuchs with 205/55-16 tires. This keeps my Speedo reading correctly. I kept my original 6x15!cookie cutters that I use for Autocross with 205/50-15 Hoosier’s. Speedo reads way high.

As far as using 215 tires, you may have rubbing issues. I have had issues of rubbing with 205 tires.

[MrBonus]

I'm running 205/55/15s on 15x7s. When I purchased the car, it had 195/65 tires that rubbed in the rear bad enough to burn through the paint. Currently, they do not rub.

As Harry mentioned, the available performance tires are somewhat limited, probably worse now with the ongoing tire shortage. I picked up the last four DZ102s in the country in March so let's hope I don't drive over any nails.

[Bill Verburg]

Originally Posted by fastricky

Hi all, I'd like to upgrade the stock (puny) wheels and tires on my T. I'll be going from the stock 14" up to 15". I'm pretty settled on Pirelli Cinturatos CN36, but please chime in if I should reconsider that idea.

Wheels I'm looking at are Maxilite Replica Fuchs Deep 6 and 7R wheels + tires in 185/60/15 and 205/60/15.

Does that make sense? Will those sizes work without any issue? Any other thoughts? Thanks in advance - Rich

You don't need the 7R o/s in back, stock 7 ET23.3 is fine as long as the tires aren't too tall

CN36 215/60 x15 on the stock 7ET23.3 will rub several inches up above the rear lip, unless the suspension is very stiff, the car rides high or a lot of neg camber is used or some combination of all 3

even w/ a tall 215/60 x15 CN 36 and the 7R wheel you will need a spacer and likely need to change studs

CN 36 does not come in 185/60 x15, that is an odd size for a 911 front or rear

the usual good 6ET35/7ET23.3 set is one of the following
185/70//195/65
195/65// 205/60

if you use 205/55 x15 or 205/50 you will want a 195/55 front to match tire heights, also will want 7ET23.3 front wheels

[fastricky]

It's getting quite complicated! Not to mention I'll be importing tyres from the UK so I think maybe I should just go with a tried and true approach? How do you all feel about sticking with the classic 6x15 all around and 185/70 15s all around as well?

[HarryD]

Just a comment. For a while I had 205/55-15 tires on my 1973.5. They were ok but I HATED the inaccuracy of the Speedo and Odo.

Depending on your feelings, you may want to be sure the OD of any tire is approximately the same as stick to keep your instruments close to accurate.

[Bill Verburg]

Originally Posted by fastricky

It's getting quite complicated! Not to mention I'll be importing tyres from the UK so I think maybe I should just go with a tried and true approach? How do you all feel about sticking with the classic 6x15 all around and 185/70 15s all around as well?

That would be fine, what you use just depends on what you want out of the car

I think that Tirerack may also sell the Pirelli classic tires like CN 36, wouldn't hurt to ask

[fastricky]

Originally Posted by Bill Verburg

That would be fine, what you use just depends on what you want out of the car

I think that Tirerack may also sell the Pirelli classic tires like CN 36, wouldn't hurt to ask

No track use. Mostly long distance / hwy driving.

[fastricky]

Also regarding the speedo, currently it reads @ 5mph too high so I suspect the wheels/tires were once larger on the car and now with the smaller size it reads too high so I hope going with the new sizes with come close to correcting the issue

[Bill Verburg]

Originally Posted by fastricky

No track use. Mostly long distance / hwy driving.

Different combos have additional effects besides street/track
A shorter or lighter setup will fee up some additional torque that goes for acceleration,
more grip in front reduces under steer
more grip in back reduces over steer
some opt for looks
etc

4 x6ET36 w/ 185/70 x15 is a nice stock setup, using 4x 195/65 on the same rims adds grip at both ends and is slightly shorter than 185/70
using 4x 195/60 does more of the same

4x 205/55 is slightly taller than 195/55 but again adds grip
you won't want to use 185/70 on 7s but just going to 4x7 adds grip at both ends w/ any of the above tires

6 front & 7 rear adds grip in back

the stock speedo is supposedly calibrated for a 25.1" tire 185/70 unless you have a '76 930 or '76 Carrera 3 w/ optional 50 series tires.

I've found that they are rarely accurate

[KMoore68]

For later as I'm going to need tires eventually, thanks for all the good information!

[fastricky]

Thank you Bill, excellent info! I'm narrowing down my decision:

- I also have a '76 912E that came with 215/70 15s all around. I LOVE the ride of that car, I'm no expert but with some informal measurements all seems to be the same in the wheelwells on both cars... true?

- My initial thought was to just go with that same setup but I'm a little superstitious that it'll be problematic so perhaps a better idea is to go with 4 x 205/55. Is 205/60 an issue?

- I'm decided on going with the same rim on all 4 corners, 7s so thanks for that help!

[Bill Verburg]

Originally Posted by fastricky

Thank you Bill, excellent info! I'm narrowing down my decision:

- I also have a '76 912E that came with 215/70 15s all around. I LOVE the ride of that car, I'm no expert but with some informal measurements all seems to be the same in the wheelwells on both cars... true?

- My initial thought was to just go with that same setup but I'm a little superstitious that it'll be problematic so perhaps a better idea is to go with 4 x 205/55. Is 205/60 an issue?

- I'm decided on going with the same rim on all 4 corners, 7s so thanks for that help!

yes, '76 912 and '73T will have the same wheel wells

and yes the 215/70s will provide a relatively cushey ride

but
the issue is their heights, @ ~26.9" tall they are energy hogs compared to any of the tires discussed above, I'd never want that size on one of my cars, let alone on a relatively underpowered car like yours

you really, really want to keep tire ID under 25"