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As a warm up, I've spent many hours reading threads on rennlist, articles on various 928 forum pages about which wheels fit and why. It seems there's a lot of views and there's no definitive guide to but there's a reasonably strong cluster of views around certain points.
Keen to replace the aftermarket wheels on my 1990 S4 with something OEM and also a look that modernises the car (the current wheels do that, but I just don't love them, and they're not a perfect fit either). This wasn't something that I was planning to do now, but some wheels have come up for sale that are exactly what I want looks wise and may just fit well. In a very small market like NZ jumping on these might mean I don't need to pay for shipping some from overseas, import duties etc, so it may be an opportunity not to pass up.
I'm also more biassed toward getting the handling of the car to the best it can be rather than the look - so I'm not going to slap the wrong thing on just because it's trendy. I'm also not interesting on rolling wheel arches etc.
Based on what I've read the fronts look ok but the rears might have too large an offset? Maybe they would work with a spacer? And I have no idea if the tyre heights will result in the right speedo reading and ride height.
Those are not the best Carrera wheels,
you need the square spoke type,
though these look a lil better IMHO they dont fit as well.
And the cost is very hi for the ones your looking at
Those are not the best Carrera wheels,
you need the square spoke type,
though these look a lil better IMHO they dont fit as well.
And the cost is very hi for the ones your looking at
Stan, those are KiwiBucks, the OP is in New Zealand. Take off about 30% then figure shipping and duty to NZ. But you are correct about the fit.
Bales, to add to Stan's comments there are two issues that I see: One is that the front offset at ET 50mm is too small. What that does is move the tires outboard of the neutral steering axis, which means that if a tire runs into anything soft (standing water, rutted pavement, edge of the road) then it will pull towards that direction. The neutral axis Is 55mm, factory wheels are ET65mm (60mm for ClubSports), not a huge difference. But one of our wheel sets is aftermarket 18" Cup-2's at 52mm in the front, and I do not like them. On our worn highway pavement, they definitely make the front end feel squirrely compared to 18's with ET 61 or 17" ET65. In the mountains they are fine, it is the highway cruising that is annoying.
The other issue is the width difference front-to-back for these wheels/tires. Earlier 928's had "square" tire fitment, same width front and rear, and handling was pretty neutral. You hear folks say those care feel lighter and are more nimble. Some of itis weight, but also Porsche fit wider rear wheels and tires on the later cars. That moves the handling towards understeer and the car wants to "push" straight ahead when pushed hard. This can be compensated (within limits) by stiffening the rear sway bar (search e.g. "Ott links"), but skinny tires in front and fat ones in the rear are not kind to handling for these cars.
Also try to stick to 25" tire diameter or a bit more, but not less--especially with 18" wheels. You need rubber between wheel and road.
Our favorite wheels & tires so far are 8.5x18 ET61 front, 9.5x18 ET48 rear, with 235/40-18 front tires and 265/35-18 rear (RUF speedline wheels, Michelin Pilot Sport-4 tires). Tire diameter is around 25.4", speedo reads a bit low but that's only a suggestion.
Stan, I like your wheels! In USD theses ones I am considering are about $2500. If I ship from Europe or US I will pay at least 15% duty on top of purchase price plus shipping costs (idk but can't imagine less than $500). So I reckon there's a 30-40% overhead for me to buy offshore, which is why these got me quite excited.
Jim, thanks so I take I should look for an ET55-65 for the front and about 50 for the rear?
Stan's are the carrera 3 right? Looks wise they would be my 2nd pick after the 5 spoke lightweights and from a distance they are hard to tell apart anyway. Not sure how often they would come up here, maybe once or twice a year?
I think only you can answer the questions as applies to your specific needs. Jim has covered the "Raison D'etre" for the ET65 offset. Now you need to decide first of all whether you need such built in protection. Coming from the UK where it rains nigh on every day of the year [or when you take the car for a run that is] I value such design feature as being of paramount importance. Where I reside it is virtually irrelevant given it hardly ever rains and when it does one needs a semi submersible!
I have run with wheels similar to the ones [spec wise] you posted originally. They look good and will fit with a 225 section up front and at ET50 on a track may even perform slightly better given my understanding of handling dynamics. Last thing you want is ET55 as they tend to feel very twitchy and prone to tramlining. Have never run ET57 so cannot comment but if they are good enough for Stan they should be OK but will not give the extreme protection built in by Porsche at ET65. Even Porsche seemingly could not make up their mind as to what is really needed or so it seems given they supplied ET60 on some special models like the CS and SE plus the 89GT.
The problem I had with the wheel set I had that were similar to the set you initially listed in post 1 was the chronic understeer and the general feel of the handling. With hindsight I think it was down to my head wanting the fronts to keep up with the rears, that and I hate cars that chronically understeer even though they are much safer in the hands of lesser drivers. The 285s on the rear simply out handle the fronts by some margin and this becomes apparent instantly when on a track or driving at the limit. If you want a good looking set of wheels, are not pushing any handling limits and you do not drive in extremely wet conditions then the original set you posted may be very attractive, especially as the wheels are shod with Michelin PS2 rubber and that has to be worth a grand or so if they are pukka. There again i understand it rains in NZ!
Simply put- it is very much down to you and what you want. If you are a mature driver and want something that looks good with some limitations go for it.
You may also find the following thread interesting:
Cooky cutter wheels in 17 or 18 inch size are very 928 and look awesome but no idea how much they are today. Rob got a stonking Black Friday deal last year. Sadly modular wheels typically cost about USD5k a set.
The Carrera Lightweights are not a good fit or offset. I had them when I bought my car and hit a mid-corner bump that had the tire grab the inner fender lip. I moved to an 8" et 57 and rolled the fender lip and have been fine since. One of the best OEM wheels for the 928 fitment is the Panamera wheel.
I run 8" fronts and 10" rears with 295 rear tires and don't have any handling issues with regard to understeer and the extra rear meat helps the car put the supercharged power down better. I think Porsche themselves went to a staggered setup during the evolution of the 928, so wouldn't worry too much about doing a square setup.
Carrera Lightweights car came with Carrera LW front wheel in fender - offset is too low unless the car is at stock 4x4 ride height
Petza - supercharged convertible 928... ?! Definitely living up to the addict tag
I've decided to pass on the wheels and wait until I find the right set of the carrera 3's. Just had the existing wheels taken into a specialist and given a once over (2 were slightly bent), has improved ride quality but now I'm really noticing understeer so new wheels will happen, just not right now.
Besides, my rear wing just fell off so that feels more important to get fixed rn...
Petza - supercharged convertible 928... ?! Definitely living up to the addict tag
I've decided to pass on the wheels and wait until I find the right set of the carrera 3's. Just had the existing wheels taken into a specialist and given a once over (2 were slightly bent), has improved ride quality but now I'm really noticing understeer so new wheels will happen, just not right now.
Besides, my rear wing just fell off so that feels more important to get fixed rn...
Darn that underside is clean! I only just worked out from the photos that the workshop is your garage, lol. Saw a supercharged 928 for sale in NZ couple of years ago but they'd sacrificed the AC to fit the supercharger in, not the best choice in our climate imho. Wasn't sure if it could be done and keep the a/c, nice to know even though I'll probably never go there
... I've decided to pass on the wheels and wait until I find the right set of the carrera 3's. Just had the existing wheels taken into a specialist and given a once over (2 were slightly bent), has improved ride quality but now I'm really noticing understeer so new wheels will happen, just not right now...
I found your earlier thread, you wrote that wheels are 18" of unknown offset/width and tires are 225/40/18 on the front 265/35/18 on the rear. That's a bit fat in the rear (or skinny in the front, by comparison) and will understeer. More meat is always better but there are limits especially in the front.
Factory S4/GT was 16" wheels with 225/50 front and 245/45 rear, and understeered. The GTS (and many S4/GT retrofits) was 17", 225/45 front and 255/40 rear, also understeered. All of those were 25.0" tire diameter.
The factory never fit 18" wheels to the 928 (and would be horrified), but our favorite setup is 18" wheels with 8.5" ET 61 in the front and 9.5" ET 48 rear (RUF Speedline), with 235/40 front and 265/35 rear tires, which are around 25.4" diameter. That's about the same amount of rubber between wheels and pavement as the 17" setup, and the speedo reads a bit low, but that only relates to posted suggestions. And yes, that would also understeer a bit, except that ...
The other piece to the puzzle is to stiffen the rear sway-bar a bit. If you do that, then 225/255 or 235/265 front/rear tires will be very close to neutral handling-- at least that's what we've found. And the simplest way to do that is with a pair of "Ott Links", which shorten the lever-arm on the rear bar. Louie Ott made them for years and Hans has picked up the design, his post is here: https://rennlist.com/forums/928-forum/814172-ott-links-return-rebirth-of-the-original.html.
For the Carrera 3's, it seems you can find sets that have have a low 50's offset for the rears but only in 11"rims. To get a set in 10" rims you're at ET58.
From the reading I've done, and the advice below I can't seem to see an issue going with this set-up (on the basis I just want to put them on and drive):
12-16-2020, 04:00 PM
Wheels - offsets and tyre sizes - advice needed
