Tire fitment for a RGruppish '70 911

[zymurgist]

I have a 1970 911T that was fairly substantially modified by the PO. It has a 2.4 with MFI, a 911SC 915 tranny, and it has been lowered somewhat. It came with 15x7 inch Fuchs with 205/60R15 Yokohamas (apparently very old tires) all around. The car also came with racing rims with 205/50R15 front and 225/50R15 rear. I will be having my wheels refinished and when I get them back, I plan to put on new rubber. I was wondering what tire size, manufacturer, etc. would be best for a hotrod 911 that is used only on weekends (not a daily driver, never sees rain) and hopefully some DE events in the near future. Thanks...

[Jim Richards]

Ken, with your 7" Fuchs and assuming your rear fenders aren't flared beyond stock for '70 cars, you'll be able to carry 205's at all four corners. 215's in the rear are a maybe, with more negative camber and rolled fender lips. What are your racing rims? What sizes are they? Are they Fuchs? If not, what's the offset values?

[sturco]

Ken, Here's what I run on my 71 911T. It's an RS clone with std. rear & front flares. Street set-up is Fuchs 6 X 15's with yokohama 205-60-15's . Track set-up is 7 X 15's with 205-50-15 yokohama (compound tires). The 7's in 50 series will not scrub the rear inner fenders on the track. The 6's on the street are fine. I have the car severely lowered for the track & negative cambered also. The 60 series tires on 7's burned the paint off the rear fenders from the inside due to rubbing. switching to 50 series on 7's lowered the profile enough to eliminate the damage. hope this helps you. By the way, street tires are AVS Intermediate & tracks are 032R's. Steve Turco, R-Gruppe #123

[ttweed]

Originally posted by zymurgist
I was wondering what tire size, manufacturer, etc. would be best for a hotrod 911 that is used only on weekends (not a daily driver, never sees rain) and hopefully some DE events in the near future.

Check the 7" rims in the rear with the 225/50s for clearance issues before you invest in the new tires. Some of the un-flared early cars won't tolerate a 225 on a 7 in the back. You don't mention what type and offset the race rims are, but if they are purpose made to fit the rear with the correct offset, you may be golden.

If you want the best dry grip and still get decent wear, run the Kumho V700 Victoracers in the 205/50-15 front and 225/50-15 rear. They are excellent for autox and DE, but they are a race compound, so some people would only recommend them for experienced drivers.

TT

[dd74]

Ken - I just fitted 225-50-15 Yokohama EVS 100s on 15x7 Fuchs in the rear of my standard narrow body 911. If enough negative camber is dialed in, this is very workable. I have no rubbing issues, though I do think the corner balance and ride height adjustment that I had have helped in this.

I'll find out what the camber is - I can't remember off hand - and post the figure.

[ttweed]

Originally posted by dd74
I have no rubbing issues, though I do think the corner balance and ride height adjustment that I had have helped in this.

Have you driven it hard around corners yet? Are your torsion bars and ARBs stock? The trouble is that even if the tire clears the lip, in high body roll situations, the outside shoulder of the tire contacts the inner side of the fender about 1-2" above the lip and rubs. I have seen paint bubble from the friction, as sturco describes above.

If your car doesn't roll much in hard cornering, and you have a lot of negative camber, you can get away with it. I ran 225/50-15s on my '73 for awhile before it was flared, and it was fine with 26mm T-bars, 19mm ARB, and -1.5 camber in the rear. Other early cars with similar setups have had problems on one side or the other, though. Best to test fit your car and see.

TT

[911novice]

Tom,

I've got a narrow body and 225-16's on the rear with neg camber. I just got the paint bubble you described on one side after a hard day of driving. Living with it but considering new T-bars. Did you find that they really helped? Also, any comment about the flare job? Also considering that down the road.

b

77s, 3.2 block w/78 heads/CIS and 74 exhasut

[tangerine911e]

Steve,

Have you got any pictures of your setup. I always looking for pics of RS style cars but with the narrow bodywork (just trying to convince myself I need a duck!).

wrt to the 225s - is possible but check and double check before you do it (and then allow some more!). I've got 205 & 225s.

Ash

[dd74]

Originally posted by ttweed
Have you driven it hard around corners yet? Are your torsion bars and ARBs stock? The trouble is that even if the tire clears the lip, in high body roll situations, the outside shoulder of the tire contacts the inner side of the fender about 1-2" above the lip and rubs. I have seen paint bubble from the friction, as sturco describes above.

If your car doesn't roll much in hard cornering, and you have a lot of negative camber, you can get away with it. I ran 225/50-15s on my '73 for awhile before it was flared, and it was fine with 26mm T-bars, 19mm ARB, and -1.5 camber in the rear. Other early cars with similar setups have had problems on one side or the other, though. Best to test fit your car and see.

TT

Aside from taking it to Willow Springs, all the twisties I've gone through haven't caused any issues yet. BTW: 1.5 neg. camber is what I believe I have.

[DonDavis]

David,
Are the rear flares the same on your 74 as 69-73? I thought they had a touch more flare.

I had 205/60/15 on 6jx15 on my '71 and my '72 has the same. I think I saw some fresh marks on the inside rear of the 71 but its suspension was a bit tired. I had heard that 215s are safe and 225s with neg camber.

[dd74]

Hi Don:

I haven't really studied the flares on cars earlier than my '74. However, there are so many differences from car to car, that it is difficult to get an definitive "yes" or "no" on a 15x7-225-sized tire combination on the rear of a narrow body 911.

Tire sizes vary from one manufacturer to the next, body alignment varies, condition of suspension is always a variable, and I certainly would not attempt this without the guidance of Tyson and his suspension abilities with corner balancing and ride-height adjustment.

Now here's a teaser: Last Friday night we came very close to fitting a standard 15x8 Fuch with a 225-50-15 tire on my car. It didn't quite make it, but like I said, tires vary from manufacturer to manufacturer, and my car can, I believe, withstand possibly a half-degree more camber; so I am not ruling out the possibility of even a larger rear-wheel-tire combo than the 15x7 and 225-50-15s.

We're going to try the 15x8 with a different 225 tire again this week. I'll let everyone know what happens.

[sturco]

Hi Ash, Will get you some pics this weekend, the car is in my sons garage for winter. I'll be there for a visit on friday. Steve

[ttweed]

Originally posted by dd74
Aside from taking it to Willow Springs, all the twisties I've gone through haven't caused any issues yet. BTW: 1.5 neg. camber is what I believe I have.

If you have run it hard at WSIR with those tires already then you will never have a problem! I thought you said you "just fit" the 225s, and wondered if you had driven them hard yet. If you already had them on for your last track day, then you are fine. Good luck on the 8x15s- they put the entire extra inch to the outside, so I don't see how you will make them fit! Does Tyson have a magic wand?

TT

[dd74]

Originally posted by ttweed
Does Tyson have a magic wand?

TT

LOL! Don't know. The women seem to think so!

[ttweed]

Originally posted by 911novice
I've got a narrow body and 225-16's on the rear with neg camber. I just got the paint bubble you described on one side after a hard day of driving. Living with it but considering new T-bars. Did you find that they really helped? Also, any comment about the flare job? Also considering that down the road.

You don't mention what aspect ratio the 225 tire is on your 16" rim, or what the rim width is (7x16", I assume?). If you are using a 225/55 tire, then a 225/50 or 225/45 may still work for you. It will lower your final drive gearing, though, as you go to smaller aspect ratio tires, and make for a harsher ride over bumps.

Heavier T-bars will help control the amount of upward travel the wheel has in cornering and over bumps, and heavier sway bars (ARBs) will control how much the body leans over onto the outside wheel, so both will help with your tire clearance problem. They will also seriously effect your ride quality. Additional negative camber will tilt the top of the wheel inwards and help clearance, but will affect both handling and tire wear. Everything is a compromise.

As far as flaring the car goes, that is the most expensive thing you could do to correct the problem, as it will involve cutting your fenders and welding (or bonding) on the flares and repainting to match. Figure $1500-2000 minimum unless you do all the work yourself.

TT