StratfordShark

My original rear left liner still has foam in OK condition (see photo) but a number of cracks in the plastic so the foam is holding some bits together!

Spotted a NOS GTS liner 92850430304 on eBay with a Oct 2018 parts sticker, at very good discount to Porsche price so bought it. The foam is lovely and thick and different kind to original.

My understanding is that post 2016 Porsche made the GTS rear liners so that they'd fit the MY91 S4s without modification, but I'm not having any luck getting it positioned in the wheel well — feels as if it has to be crammed in and then it gets stuck in wrong position, whereas the original slides in OK with all the holes lining up.

Can anyone suggest a technique to install it, or is there some cutting I can do that will help? If not I conclude that the liners to fit the wider GTS rear arches don't in fact fit the S4, and I'll have to just sell the new one to a GTS owner and put the old one back, cracks and all!

StratfordShark

Just to answer my own question here, it seems my GTS wheel liner is one of earlier ones which is too wide for S4. Measures 14" across middle (measuring across section with top fixing hole) but the original measures 12". Even allowing for some 'forming' of the liner it's not going to fit! I wonder if anyone can confirm the width of the LHS liners currently supplied by Porsche?

FredR

Adrian,

The font of all knowledge for this item is most probably Jerry [Redesign by Feather]- he made a version of this item when they were unobtainium clever chap that he is.

I know my 93 GTS does not have these things but why I have no idea. Neither did my 90 S4. Both vehicles are a little noisy in the rear end but then I run wider rubber. I have run with stock rubber on both the 90S4 and my current 928 and felt they were a bit noisy in this regard- however 20 years on I am a tad deafer so maybe my sensitivity is not what it once was. I also have some natural noise cancelling eardrums [tinnitus]!

StratfordShark

Thanks Fred and yes I’ve read with interest/admiration Jerry’s threads on fabricating these.

Could be I’ll have to trim the new liner, but I’m reluctant to wield scissors yet having read here that ‘new’ GTS liners fit narrower S4 with no problem. My liner is dated 2018 and I know a U.K. owner couldn’t fit new liners bought from Porsche in 2019 to his MY91 GT without removing a lot of the foam.

Just curious how to identify the mysterious ‘universal’ fit and how it works. Does it leave a lot of the GTS arch uncovered perhaps?

FredR

As I recall the GTS wheel arches protrude some 40mm or so or 1.5 inches in pre-historic units

Jerry Feather

Based on my own measurements I found that the wheel arches on the GTS are just at one inch wider on each side from the earlier cars. I used that measurement in devising the shape and size of the outer half of my two-piece design of these 928 WW Liners that I made some of. These liners were put in by the factory starting in 91 when they put the two little hat-section mounting points up in the top of each wheel well. Then they originally had two different sets of molds or forms to make the two different sizes of liners.

I think what must have happened at some point well after the 928 production ended was that someone decided that having two sets of molds or forms was no longer necessary, thinking that, and they looked to be the same, so they decided to ****-can one set. However they ended up getting rid of one of the GTS molds and one of the earlier molds. I think it was the right side GTS and the left side the earlier one that they kept. Then they produced the liners not realizing that they were two different sizes, and put the GTS part numbers on them.

I got involved in the Liner project about when Roger found himself sending back the liners because one side did not fit the GTS, and there was no other alternative. Roger and I were cross-ways with each other and when I told him that I would not sell him any of my Liners I think he actually went back to the Factory and got them to correct their error and they then started producing just the wider GTS liners. I think Roger may be the one who suggests that the new Factory liners are "one size fits all." That factor (the Factory effort) and other events in my life kind of put my liners on the back burner.

I recall seeing a picture I think was posted by Rob Edwards of the latest factory liners in one of his cars. I don't recall now if it was a GTS or Earlier car, but the fit shown in his picture was really quite crappy. I still have all the components of my Liner Project but they are all kind of tucked out of the way now since I had to move much of my stuff to make room for the Radical Custom 928 project that I have also now been away form for too long.

What I need is a student to start to take over some of these unfinished projects and things, but a student with some already developed fabrication skills. My 22 year old daughter is showing some interest in my projects, but I don't think I have the time to teach her the basic skills and then the projects. One thought is that I might take the WW Liner project over to my remote shop, about 8 miles away, but I will need to remove a couple of cars first and I don't have another good place for those. I think I'll work on that some. Too, I still need to devise a couple of mounting points for the liners to work in the S4s before 91. I have the points for the left side, but there is none for the upper rear of the right one.

Jerry Feather

What I think I would do if I were you, Stratford, is modify the newish liner that you bought. I would first remove exactly one inch of the foam in a strip front to back just outside of the two top mounting points, and maybe adjust the one inch line so that the front mounting points will match the car. Then I would cut the liner material, whatever it is, along one side of the one inch foamless liner strip and then overlap them that same one inch and glue it back together with some kind of appropriate adhesive. When you have it cut apart you can fit the inner side of the liner to the car and figure out what to do with the other front and rear mounting points, then you can work the outer half into position and adjust the overlap as necessary. Now that I think about it you might even consider using some kind of temporary clips to connect the two inner and outer halves so that they end up two-piece kind of like mine.

FredR

I suppose the $64 million question is whether they make any real world difference noise attentuation wise.

I have often wondered if it might be possible to cast something "in-situ" that would still be removable

StratfordShark

That's an ingenious thought Jerry thank you very much. I was just thinking of trimming the outer side by an inch but your idea is more elegant, and preserves the formed outer edge.

GregBBRD

The factory inner liners make a huge difference in the amount of both tire and pebble noise transmitted into the interior of the car.

Everyone's first impression is that the material they were made of was fairly fragile, but once you stop and think that all the originals are now over 25 years old, the material actually held up fairly well.

The price?
Well, it's a replacement Porsche part for the flagship of the Porsche line, back then.
And anyone who bought a 928 thinking replacement parts were cheap, made a bit of a mental error.

Gary Knox

And, when I bought a set of replacements a few months ago, I heard there WERE only 2 or 3 new sets left in the world.

FredR

I must say the 928 feels sweeter when I play Sweet Alabama and other memorables through my mobile phone via ear buds!

I am the sort of engineer who would use a pencil when travelling in space rather than a zillion dollar ballpoint- not that I actually believe that one [100%]!

For sure tyres are very noisy little buggers. I have no idea why my 928 does not have these- one wheel arch has nothing so something could have dropped to pieces in there and the detrius removed but on the other side it looks like there is a delibrately fitted plastic cover but it does not look like it ever had sound asborbent foam on it. I doubt the foam things were an option [were they?].

The positive side of it is that in our climate there is no such thing as road salt and sand/dust tends to settle on the surfaces with no detriment. I let this crud settle onto whatever Porsche put there to start with and I reckon if I ever tried to remove it it would look factory new it is that clean. No sign of rust anywhere on the car.

Maybe it is possible to fabricate some kind of plastic / foam sandwich plate that can attentuate the sound some. As things stand the factory insert appear to run at something like 500 bucks a pop each side. If we are talking about maintaining a concours finish on a top end GTS maybe - for the immediate future reckon I'll continue to give Lynyrd Skynryd some clog!

StratfordShark

Lynyrd Skynyrd sounds a good option Fred.

Sound deadening foam wasn’t an option but only installed on MY91 and all following GTS cars. It’s included in the service information for MY91.

No idea why your liner missing on one side. If they deteriorate then the biggest stress is removal and reinstall which is only necessary on the left side for PSD service. Maybe in past a garage just forgot to put it back?

Gary Knox

Fred,

Check Alan Moore's website (Electron wrangler,lives in the Arizona desert) - he has a very nice write up on making a set of rear wheel liners from large size plastic trash cans. If you can't find it, send me a PM and I'll send you a copy of the article. I think his website is: http://928-electrics.com I would have followed his procedure if my car hadn't been a '95, and I wanted to keep it 'stock'.

Here is a link to his 'projects' page: http://928-electrics.com/Porsche/928%20Projects.htm

If I recall correctly, the rear wheel liners are at the bottom of this page. LOTS of other good stuff on the page, however.

Cheeers,


Gary

FredR

I can understand one side missing completely but the other side looks stockish to my 900S4 way of thinking. Maybe both sides fell to pieces in our local heat and the main agents dumped something from an earlier S4 model in there to provide some protection.

I like Gary's post about Alan coming up with something based on lateral thinking- sounds like my kind of mod- if all else fails I will drop Alan a mail.

When my vac reservoir connector on the servo snapped off I found a piece of broken radio control unit telescopic antenna in my "saved just in case" box of bits and pieces. Bonded it into the unit- still perfect years later. Then last year during a inlet maniold out job I found the actuator for the flappy was not working. A new one was something like 80 bucks. i was fitting a new heater valve at 30 bucks- in my case I do not use the heater- it is bypassed- so I pulled the actuator and cut the mounting bracket off the heater valve and managed to modify it to fit and work on the inlet manifold using one of my wife's aluminum kebab skewers as a support bracket- still holding OK but not for the purist I would suggest!