marknsf

This my first post. I recently acquired an ’87 928 S4 auto with 95k miles. I still have an ’86 944T and had a ’74 911 before that.

The interior, body and paint on my 928 are in good condition, however, there is some deferred maintenance. I been reading this board for the last month and have found answers to ever question I’ve had so far. I commend the group for the outstanding effort that has been done by many over the years to create such a wealth of knowledge and keep these cars on the road.

Right now I’m replacing the Boge shocks (apparently the first time for this car). Bill Ball has come over a couple of times and with his expert help and advice things are going smoothly.

I know that tires for the original 16” wheels are getting harder to find and I am thinking about looking for larger wheels. I’ve read the posts on wheel fitment so I know there are relatively few wheel/tire combinations that will fit properly without modifications.

My interest is in using the car for Grand Touring so I want to keep the ride comfortable with good handling. I would like to go with 18” Panameras as there are lots of tires for that size but I have some concerns:

1. Will the shorter sidewalls of an 18" result in a harsh ride or does this depend on the aspect ratio chosen? Would a 17” Cup style be better for my purposes?

2. If the car is aligned with the 16” wheels will it need to be realigned when I go larger?

3. Does the "928 Wheel Fitment Calculator" spreadsheet work for all years just by entering the stock tire size or does it need adjustment for the model year?


Mark

The Forgotten On

1) I have been using Panamera rims on my 81 for a year and it still has a comfortable ride, more so after I had the shocks replaced as you are about to do.
2) You do not need an alignment if you get a larger rim and tire combo unless you lower the car to account for the amount your car will be lifted from the bigger tires.
3) Not sure, some one else will chime in and help on that one.

17 inch tires are also getting harder to find so I would recommend going for 18 inch Panamera rims to future proof your car a little bit.

Panamera rims are also cheap and plentiful and are not as delicate as cup rims are.

Alan

17" are getting a little harder to find too - but nowhere near as bad as 16".

18" has more choices but regardlees of aspect ratio (e.g. essentially driven by width here) to approx match the stock circumference you must have less sidewall height - so it will be stiffer and you will be relying on more suspension and less tire for ride compliance than in the stock OR 17" case.

18" wheels will be more prone to damage over large potholes as they are relatively weaker for the same construction - obviously depends on wheel type and tire fitment (relative tire tread width to rim bead width).

BTW if your car is lifted from adding bigger wheels/tires you are doing it all wrong...!

Alan

joejoe

I am very surprised with the ride of 18" tires. Have been running 17" twists on my '81 and '86.5. Recenty got some 18" twists for the '86.5 and am pleased with the ride. This car is in need of new shocks also.

Jadz928

I've ran 16, 17, and 18's. I think the 17's are ideal how you want your 928 to behave.
However, 18's are the better choice due to tire selection. And with stock boges (non-sport suspension), it will feel really good.
Now, if your commuting with it and your roads suck, go 17's.

Tire fitment calcultor works for any wheel.

MainePorsche

17

ashmason

I have a 1990 GT and had the same question, I went with 18", but I live in LA and most of the road surfaces are terrible so given I use the car at least once a week and my wife is usually with me, i wish I had gone 17" for a little more forgiving ride.

On the plus side I went with cup 4's from tire rack so the whole package didn't cost that much so I may rethink when I need new rubber

Captain_Slow

I agree. I have the non-sport suspension and have been very pleased with the ride with 18 inch Panamera wheels. The tire sidewall stiffness is a factor also.

stuartbrs

I have 18`s on my S4, the ride is a bit harsher than the 16`s I had on my previous S but to be honest, it doesn't bother me much at all, its not really that bad. I think 18 is as big as you can go on a 928 without the wheels starting to look like wagon wheels!

marknsf

I appreciate the feedback. The Boge shocks are the standard types not sport. I'll probably go with the 18"s as I expect most of the driving to be on at least acceptable highways and it's a bit of future proofing.

Right now there is still a lot of catch-up maintenance to be done before I will be comfortable taking it on a long trip.

Mark

Chalkboss

I am a bit late to the game but I cannot render a decision until I see pics! Having said that, go with future-proofing 18s. I have 16s and would change but they are nice Club sports.

86gtvert

I run 18x9 in the front and 18x11 in the rear. I have never ridden in another 928(for comparison) but the ride is very. ... let's just say sensitive. I feel everything. Aside from that, I feel it has a bit more bump steer than I care to have. [See my avatar]

SMTCapeCod

Bump seer is probably more attributable to the offset on the wheels. I'm thinking you're at ET50 best case scenario. Lower offsets will amplify any play in worn suspension parts, and increase jitteriness, tramlining, bumpsteer etc.

tda1

I have the exact same wheels as 86GTvert and have no issues. 235 front and 285 rear

khalloudy

16" tires 225/50 and 245/45 are still available in europe and RoW. I have seen both Continental and Bridgestone offering them.