75 911s Targa

[djtalon]

Just bought a 75 targa that needs a bit of work, previous owner really did not use it much. Owner before him rebuilt trani, rebuilt engine with 2.8 rsr pistons and cylinders and added weber carbs. Somewhere in the past 2 yrs the rims tires were changed. The car has 215/60 16's in the back and 205/60 16's in the front. They seem big; are they?? i haev read people have been putting 50 series in the rear and 55 in the front. Why different size sidewall front to back? What size should i use?
Are the cars pretty quick with thos engine mod's?

[djtalon]

another

[djtalon]

here is the pic

[Trak Ratt]

As the cars got heavier (and more powerful) Porsche started putting wider tyres in back. To keep the same overall tyre height front and rear the aspect ratio was lowered out back.
If CIS then likely not 2.8 pistons. If carbed then likely very high compression.

[ludwig]

My 1985 Carrera uses 225/50-16 rear and 205/55-16 front. Change in aspect ratio is probably done to equalize overall tire diameter, front to rear.

[pookie]

Cool color.

I have a 76 (pretty much the same) and I have 205/60R15 up front. I just put a used set of 16's in the rear but I will get you the tire size tonight. I can't explain about the different sidewalls but some more knowledgeable on here will help you out.

If it was bumped to 2.8 and carbs it out to scoot pretty good.

[Jase007]

Ahh ... another MY [mid-year '74 - '77] owner.

Welcome :)

* I run 215/60/15 on 6.5" X 15" rims. No rubbing and all fits.

Stock cookie cutter wheels were 6" X 15" all around.

** Ludwig: welcome ... introduce yourself here. (http://dorkiphus.net/porsche/showthread.php?t=13610)

[djtalon]

records say that it has mahl 2.8 rsr pictons /cylinders, solex cams and yes it has 6 weber carbs. I am assumming always run high test gas.
what would the ballpark hp/torgue be?


thanks

[86911TLCAB]

Welcome to the board. I also have a 75 targa...though the engine was replaced with a 3.0 years ago. Tito

[markwemple]

Check for clearance on the rear, but the fronts should be 205/55 16s. The rears could be 55s or 50s, 55s being a little too big and 50s being a little too small. You'd be safer running 205s all around as you have a narrow car but if the 215s are working.....

Nice ride, enjoy!

[racer]

Until dyno'd HP is just a guess.. 210-230?

Also notice how those rears stick out abit. Until you put on rear flares you will have to have an unconventional ride hieght to prevent rear tires from rubbing.

You don't mention the rim widths (but they look like 7" front and 8" rear). If so a 205/55-16 front and 225-50-16 rear would be a prefered set up.

[djtalon]

i think the rears have spacers also (not sure) right now the rears are currently 215/60 16; so if i had 215/55 16 or 215/50 16 they should fit because the walls are smaller

[racer]

Even if the rears have spacers, the actual RIM WIDTHS are too wide for the rear. 1974-1977 are the "mid year" cars, they are also "narrow body" cars when compared to the SC and Carerras that followed. Comfortably fitting larger than a 7" rim in the rear, under the narrow body will be difficult. Looking at the "dish" on the rear rims, they would appear to be at least 8" wide. Appropriate for the potential horsepower, but perhaps not an aethetic best.

The car came (stock) with 6x15 inch rims. A 6 or 7" (and some 8") rims will fit up front fine as the front fenders were unchanged from about 1969 till 1995.

A 215/55 or 215/50 should fit better than a 215/60 because of reduced sidewall height. Then again, you can have some brands who produce a 225 width that is a big as some others 245 widths.. so I won't guarantee a fit from one internet pic ;)

[Trak Ratt]

records say that it has mahl 2.8 rsr pictons /cylinders, solex cams and yes it has 6 weber carbs. I am assumming always run high test gas.
what would the ballpark hp/torgue be? thanks

Until dyno'd HP is just a guess.. 210-230?

Also notice how those rears stick out abit. Until you put on rear flares you will have to have an unconventional ride hieght to prevent rear tires from rubbing.

You don't mention the rim widths (but they look like 7" front and 8" rear). If so a 205/55-16 front and 225-50-16 rear would be a prefered set up.Maybe even a little higher HP. Agree, wheels look like 7 and 8s and would explain why the ass is so high ;)

[djtalon]

fronts have a spacer on them and the rears look like the hub is just real wide

definatly need to change the tires around, hate that jacked up rear look

[Trak Ratt]

Just changing the tyres won’t work. Without rear flairs the wheels are too wide for the ride. Search is your friend. Plenty here about mid years a tyre fitment. Save the spacers from the front ;)

[djtalon]

if 60 size 16's are working now couldn't i put 50 series in the back and 55's in the front? I am missing somthing

[Trak Ratt]

Yes you are. Your car doesn’t have the clearance for the wheel width/offset in back at proper ride height for just about any 16” tyre. The flairs were added in ’78 with the SCs for that very reason. If the backs are 8x16 they are very desirable but need more flair on that chassis.

[djtalon]

my confusion is this; if i just change the sidewall height dosent the entire car lower? If i lower the suspension then the car lowers and the tires go up in the wheel well? and they dont fit

or

is it if i change the sidewall size i am changing the geometry of the ride height and thus more weight on the rear and the suspension compresses more causing problems?

[racer]

There are two issues here

1) Your rear RIMS are too wide for your cars fenders. That is why the car is "jacked up" in the rear- so as to avoid tire rubbing. This is why your suspension can not be lowered and thus your handle-ing will never be optimal.

2) Yes, lowering the aspect ratio of your tire from 60 to 55 or 50 will leave you with a shorter sidewall and also better acceleration. However, the tire/rim combo will STILL be too wide for the cars fenders. And, since it is a ratio, the whole car will sit 1/2-1" lower than before. However, the suspension will still not be optimized.

[Trak Ratt]

Reducing aspect ratio of tyres while keeping same size will lower car (about ½”). IMO still would be way high in back. Most say as a rule of thumb rear ride height should be about 24” – 25” at the highest point of wheel well opening measured through the center of the rear wheel. Front ride height set based on backs. My suggestion is that you do some more research before buying new tyres. 215 rears are likely not the best for your application. And you should prolly consider adjusting ride height before making any final wheel/tyre decisions.
Sounds like you have a great motor but the PO was trying to get more rubber under the back without thinking it through. Said before but will restate; 8x16 are very desirable wheels.

[djtalon]

i was not thinking that the PO changed the suspension in the back? How would he do that? Dont you have to change the torsion bars?

[Trak Ratt]

i was not thinking that the PO changed the suspension in the back? How would he do that? Dont you have to change the torsion bars?

Yes, it's called "indexing."

[}{arlequin]

any pics of your engine?

[djtalon]

will get some pics, so theheight is changed by pulling out the torsion bars and reindexing them?

car is a 75

[Jazzbass]

i was not thinking that the PO changed the suspension in the back? How would he do that? Dont you have to change the torsion bars?
You don't have to change them, just "reindex" them as DR said. The ride height on a 911 can be set independent of spring rates (to a certain degree), which is different than most cars where you have to change the springs to get a different ride height. Most of the time you do see guys changing t-bars to something stiffer like 28mm, but this is not strictly a requirement if all you want to do is raise the car up. You can lower the car, too, with stock t-bars but it's not recommended because the soft springs + lowered car = tire rubbing.

[djtalon]

engine pics

[Trak Ratt]

Very cool! Nice to see the PO added the cam tensioner upgrade, and fuel pressure gauge. Since carbs are OK on gentle acceleration you might look at the accelerator pumps first to make sure they are functioning OK. I have some docs on Webers if you want to PM me your e-mail address.

[barranr]

I'm the pre-PO, sweet car. I changed the rims. They had lower profile after market rims on them till i hit a pothole. I forget the brand (andahl or something like that) but i couldn't get a replacement anywhere. Bought the car for my son when he was to get his license but he moved back to oz to finish high school so i got rid of it

[djtalon]

just a correction barranr is 2 PO's back, i boughg it from a guy that only had it for a couple of months.

[Jase007]

I'm the pre-PO

Got it ;)

PRE-vious - Previous Owner (PO)

:)

"djtalon"

Put your first name in your signature so we don't have to call you "DJTALON" whenever someone is addressing you.

[djtalon]

still trying to find out why somone raised the ride height in the rear. Fender to ground is like 27.5 inches

[barranr]

George may have had it raised, it was a lot lower with the old rims on it though


still trying to find out why somone raised the ride height in the rear. Fender to ground is like 27.5 inches

[Trak Ratt]

still trying to find out why somone raised the ride height in the rear. Fender to ground is like 27.5 incheswheel tyre clearence.
If you don’t totally understand the re-indexing process you can raise car more than needed. Adjustments can be made on torsion bar's inside and outside but not necessarily in single spline increments.

[Jase007]

Dave:

When I set my Targa to "stock" specs ... it was easily ~ 27 +/-" in the rear and higher in the front :shock:

That was US height for bumper / impact laws.

It'll look MUCH better when you lower it. :)

[Trak Ratt]

Great another Dave... the new Muhammad :roll:

[djtalon]

rod

did you put the tires on or the guy i bought it from?

[barranr]

They were complete with tires when i bought the rims


rod

did you put the tires on or the guy i bought it from?