Will NEW 996TT 18" Twists fit '86 961 ?

Body: Applications include 993 C2S, 993 C4S, 994 Twin Turbo, 930 from 1987-89 &
1976-79.Also fit wide body converted 911s.

Tire specs are as follows:

Fronts are 8" wide with 50mm offsets. 225/40 ZR 18
Rears are 11" wide with 45mm offsets. 295/35 ZR 18

<a href="http://pages.prodigy.net/pjbloom1/_import/pages.prodigy.net/pjbloom1/index2.html" target="_blank">http://pages.prodigy.net/pjbloom1/_import/pages.prodigy.net/pjbloom1/index2.html</a>

Those are 335ZR35/18's on the rear,BTW

 

No, they will not fit unless you get spacers and longer wheel studs or adapters w/ studs.The offset on the '86 is 23 mm,(early offset) thus making the wheel offset towards the outside of the car. The offset which was introduced in '87 (late offset) places the majority of the wheel towards the inside of the car. This was done so that they could install the wider suspension pieces for different geometry and ABS etc..

 

Lou,
Do you remember what you had to buy to adapt 18's on your '86? And did the 18's help reduce tire spin as you hoped ? Jim Cunningham has same 17" cups on red '86 and is installing Quaiffe lsd for maybe $2k. I figure for that kind of $$ I could trade up to '18's and forget the lsd and use hoosiers for track fun.
I don't enjoy these supercharged Honda Qualudes hanging with me off the starts. The 951 is a dog on a 1/4m launch anyhow and tire spin just further makes situation worse than it should be. These mods I am going with are just going to help top-end with my 17" tires.

 

I didn't have to buy anything. My wheels were made for my car, they are a 3 piece design so it has the correct offset. As for tire spin, that's where throttle modulation comes in. The real benefit is handling and turn-in response along w/ better braking. Tire spin is related to traction, something that rim diameter will not cure.

 

Norman,

Porsche issued a bulletin against installing 18" rims on the 944 series vehicles.

I agree with Lou, wheel diamiter will not improve traction. But a lsd WILL MOST DEFINATELY improve traction!

 

I have heard several 18in. owner (doesn't sound good) tell me how much they love them. I hear with 16's they run 4.9 to 60 and 4.3 with 18's. I hear they have run 18's for a couple years without problems.
.
.
then I also hear of 18's in owners going through 3 steering racks in a year?!? <img src="graemlins/oops.gif" border="0" alt="[oops]" />

 

Here is what Porsche has to say about it;

March 23, 1993
Subject:
Installation of Porsche 18" Wheels Not Approved
Models Affected:
All
Concern:
Retrofitting 18" wheels on Porsche vehicles which do not have 18" wheels as original equipment is NOT ALLOWED.
General Information:
Endurance tests have shown that equipping certain Porsche vehicles with 18" wheels in an application not already approved by Porsche Cars, N.A. may result in loosened bolts and/or threaded connections on the front wheel carriers. This, in turn, may cause fractures in these components. Fractures may also occur in the front strut mounts and in the body in the area of the rear suspension as a result of the installation of 18" wheels not already approved for installation for this specific application.

Such damage can occur without warning and the vehicle may become very hard to control or steer as a result of this improper installation.

 

why do so many people run and sell (ie vertex/automotion/lindsey racing) 17 in wheels then? they were never optional/standard on any 944?

 

I have never heard anything bad about 17" with the right offset and tire size, Porsche is warning about using 18". If you want to see some BIG 17" tires see the ones Danno put on his car.

<a href="http://members.rennlist.com/951_racerx/" target="_blank">http://members.rennlist.com/951_racerx/</a>

 

I researched the Tech Bulletin concerning the installation of 18" wheels and there was nothing there pertaining specifically to the '86 951. I then contacted my local Porsche dealer, after his research, he too, could not verify anything concerning the '86 951. In fact according to the dealer, the '86 was not part of the results that were noted in such bulletin. Not that I disagree w/ Porsche, but it was my decision to install 18" wheels on my car.

 

[quote]Originally posted by beab951:
<strong> Porsche is warning about using 18". If you want to see some BIG 17" tires see the ones Danno put on his car.

<a href="http://members.rennlist.com/951_racerx/" target="_blank">http://members.rennlist.com/951_racerx/</a></strong><hr></blockquote>

you are right, I misread.

<img src="graemlins/oops.gif" border="0" alt="[oops]" />

 

People can (and should) modify their car as they see fit...but you should understand the risk. Porsche is just warning people and covering their interests.

I use ALLDATA. Referenced the Technical Service Bulletins for:

1986 Porsche 944 Turbo L4-2479cc 2.5L SOHC Turbo 01/16/2003

Number Date Description

49305 930415 Wheels - Retrofitting Unapproved 18 Inch Wheels

49305 930323 Wheels - Unapproved Installation of 18 Inch Wheels

 

This topic seems to come and go with clockwork precision like the autumn leaves, eh?

• <a href="http://forums.rennlist.com/scripts/rennforums/ultimatebb.cgi?ubb=get_topic&f=15&t=001319" target="_blank">Do 18 inch wheels put a lot more stress on the suspension than 17s?</a>
• <a href="http://forums.rennlist.com/scripts/rennforums/ultimatebb.cgi?ubb=get_topic&f=15&t=002201" target="_blank">Why are 18" wheels not recommended??</a>
• <a href="http://forums.rennlist.com/scripts/rennforums/ultimatebb.cgi?ubb=get_topic&f=20&t=000095" target="_blank">Wheel spacers for early offset</a> (really about 18" wheels)

Also refer to all the threads referenced in this one:
<a href="http://forums.rennlist.com/scripts/rennforums/ultimatebb.cgi?ubb=get_topic&f=15&t=003961" target="_blank">What is the widest wheel/tire combo for '86 944? </a>

One of those threads has the TSB on using 17" wheels on cars that came equipped only with 16" wheels. I'm a filthy capitalist and I firmly believe that we should have the right and freedom to do as we wish... BUT we should also have the sense to accept responsibility for our actions as well; since some of them can be quite dangerous. Don't go skydiving, rock-climbing, stunt-flying, motorcycle-racing, car-racing, shark hunting, etc. with the mistaken assumption that these activities are 100% risk-free! If there's a warning, a known history of a certain degree of risk, or there's a TSB/note/warning from the manufacturer, then there's real danger involved and one should take those precautions to heart.

One of those threads above has a parts list using all Porsche parts and part numbers of the longer studs and spacers as well as the procedure you would use to install them. Only thing different in this case. since you're using 11" rear wheels, is to use the 65mm studs and 21mm spacer (instead of the 72mm studs & 28mm spacer specified for the rear).

Following the procedure proscribed by the TSB on 17" wheels, I've updated my car with the recommended newer caster mounts. Also had it re-aligned to the new specifications. And IF you take things further than the precautionary notes recommend (like 17x10.5/11.5" wheels which never, ever came on ANY stock Porsche), then you had better accept responsibility for your actions and take even more precautionary steps.

I've got X-rayed and magna-fluxed spindles on my car that I inspect every single month when I repack and adjust my wheel bearings before every track event. I've got a second spare set in case the first one cracks so I'm not tempted to "make it last".

So when you chose to tread into territories not tested or recommended by the manufacturer, do not expect them to pay you millions when you spill hot coffee on yourself and get burned! And even if you were to win such a case like that, I think that's highly unethical!

 

bump!

none of the linked threads work anymore, but i'd love some more info on this topic, as i just saw the c4s turbo-twist style wheels on a friend's car.... *Drools* me wants

 

If I ever get my stuff together and put some wide wheels on the car, I'm definitely going with 18's. The availability of wide 17" track tires is gradually decreasing, and the availability of 17" slicks is virtually non exsistent. I think Alan C. recently made the same change, likely for these same reasons. Also, the diameters and widths available in 18" sizes seem to suit a maximum width fitment within the confines of the stock bodywork better than the 17" sizes available.

Like Danno, when the time comes, my suspension will get frequent inspection and yearly magna-fluxes to keep Darwin at bay.

EDIT: One more thing, I haven't had any problems yet with my 24" diameter Omega Zab Judah Gold spinner wheels either. Amazing how the inertia of these wheels prevents wheelspin and brake lock up.