Tires dimensions on 911R

[ydderf911]

Hi everybody,

My project is finishing.
I need to choose tires for my 911R Replica.

I got 4 deep 6*15 for rear and front wheels because 7*15 for the rear are still a dream for the moment, but would be done in the future.

So, i need some confirmation about tires dimension i would mount.

My choise is:

Front: 6*15 deep + 7mm spacer + 185*60*15
Rear: 6*15 deep + 21mm spacer + 205*60*15

Is that ok for you ?

Freddy

[911r67]

I would use the wider wheels in the rear then you can use 225 tires works better for handling!
I would widen the 6x 15 to 7 x 15!

[andyjboy]

Hi Freddy - good to hear that your project is nearing completion.

I would probably go for the same size tyre on the front & back - either 185/70 x 15 (expensive & not much choice) or 195/65 x 15.

[Harvey Weidman]

Hi Freddy - good to hear that your project is nearing completion.

I would probably go for the same size tyre on the front & back - either 185/70 x 15 (expensive & not much choice) or 195/65 x 15.

+1 on the 195/65 and when you widen the rear to 7R you can use 215/60 for the stagger.
H

[ydderf911]

Thks for the tip,
Anyway, does anybody know the real dimension which was mounted on a 911R ?
Rgds
Freddy

[1QuickS]

I couldn't find my reference info but I think they were Dunlops; 5.50L-15's and 5.50M-15's.

[Grady Clay]

Tires:
It very much depends on your intended use.
The good news is that you can have several sets for different uses.

Generally, you will have far larger and better choices with 16” wheels.
The 6x16 Fuchs fits properly and look acceptable to most.

For ‘close-to-proper’, I would choose the Michelin XWX 185/70VR15 on 6x15 in front and 7x15 rear.
Here I would choose modified wheels that appear to be ‘deep’ but have the safety bead on the rim.

For ‘dead-nuts-original’, the configuration is original ‘deep’ 6x15 and 911R 7x15 with replica period Dunlop race tyres.
I think Paul has the correct size above.
These wheels don’t have the safety bead and were originally designed for tube-type tyres.
Fortunately, tubeless tires work satisfactorily for casual use but without the safety bead.
I won’t track these wheels with sticky, tubeless tires (Goodyear slicks).

Replica period Minilites and American Racing Mags are another period choice.
Again, the rim width should be 6” F, 7” R.

One of the fun ‘arts’ of 911R-like is to squeeze the 7x15 under the rear.
This takes substantially longer wheel studs and spacers.
Even with the 185/70VR15, the 7x15 puts a lot of tread on the ground.

If you are going to own a pair of original 7x15Rs, it is useful to invest in a plastic or leather rim cover for taking the tire off and on over the outside rim
These rims are very unusual as the drop-center is close to the outside rim and exceedingly difficult to mount from the inside.

Best,
Grady

[Harvey Weidman]

The closest to the original sizes that I have found is Dunlop 500M and 550M. I have installed them on Rs and clones on many occasions.

I hate to disagree with Grady, but the "saftey beads' have nothing to do with tube or tubless tires. They were devolped independently. They were designed originally to address the run flat issue, not for the tubless tire. There were non saftey bead wheels used on production cars through the 80s. Some aftermarket wheels still don't have them. At every race weekend there are numerous cars running tubless tires on non saftey bead wheels. I have never heard of a failure from a tubless tire seperating from a non saftey bead wheel. We did many experments in the beginning when Porsche went to the saftey bead in late 71. We found no difference when pressure was applied to the sidewall of either type of wheel using a tubless tire.
H

[Grady Clay]

Harvey,

I learn something new every day.
I didn’t know these were separated in time.
I guess it was the coincidence with Porsche changing to the safety beads in late ’71 and the (bit earlier) introduction of tubeless tires.
Has Porsche ever used a non-safety bead wheel since ’71?

My reticence to use non-safety bead wheels comes from seeing this photo of me at the Seattle (’75?) Parade.
http://forums.pelicanparts.com/uploa...1158114958.jpg
This was from just cornering, not upset from an apex burm.
Got my attention.

Best,
Grady

[Harvey Weidman]

I have commented on your photo before. Some of the effect looks to be the camera angle. I have seen similar angles with saftey bead wheels. The shine of the lip confuses the camera some how.
The tire still didn't come off? I wonder what the tire pressure was.
I have seen a R with a flat grinding the rim edge on the track and the tire was still on the bead area...That was a tough one to repair..
H