17 inch Cup II's
01-27-2021, 11:00 AM
#34
Drifting
Quoting from another thread, where someone asked about a set with ET50 front:
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.
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.
01-27-2021, 02:37 PM
#36
Rennlist Member
Quoting from another thread, where someone asked about a set with ET50 front:
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.
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.
TEILE.COM | 17-inch CUP wheel, 7,5J x 17 ET65 / new / 968 / 601-00 Rims / 9653621240561M
01-28-2021, 01:56 PM
#37
Rennlist Member
Quoting from another thread, where someone asked about a set with ET50 front:
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.
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.
I hope that helps?
01-28-2021, 02:45 PM
#38
Rennlist Member
Not sure what the legal position is in the UK with regard to non stock modifications but if nothing else I would think that you need to be aware as to whether such fitment could potentially invalidate your insurance. If you did happen to wipe out and a big claim resulted insurance investigators might cotton on and theoretically could use such as a basis not to cough up. Most UK insurance quotations specifically ask whether the car has been modified in anyway- if you have declared such all well and good..
As you have seen wheels with ET65 are more expensive- with a greater degree of overhang the wheels need to be stronger to resist the increased over turning moment. Such offsets are quite rare so no economy of scale as it were.
01-28-2021, 02:56 PM
#39
Rennlist Member
Theory says that the offset you have on those wheels may optimize cornering performance but the fact is that the reason the offset should be 65mm may well not be apparent until such time as it is too late sad to say- hopefully you will never have to find out the hard way and you would have to be pretty unlucky for such to happen but.....?
Not sure what the legal position is in the UK with regard to non stock modifications but if nothing else I would think that you need to be aware as to whether such fitment could potentially invalidate your insurance. If you did happen to wipe out and a big claim resulted insurance investigators might cotton on and theoretically could use such as a basis not to cough up. Most UK insurance quotations specifically ask whether the car has been modified in anyway- if you have declared such all well and good..
As you have seen wheels with ET65 are more expensive- with a greater degree of overhang the wheels need to be stronger to resist the increased over turning moment. Such offsets are quite rare so no economy of scale as it were.
Not sure what the legal position is in the UK with regard to non stock modifications but if nothing else I would think that you need to be aware as to whether such fitment could potentially invalidate your insurance. If you did happen to wipe out and a big claim resulted insurance investigators might cotton on and theoretically could use such as a basis not to cough up. Most UK insurance quotations specifically ask whether the car has been modified in anyway- if you have declared such all well and good..
As you have seen wheels with ET65 are more expensive- with a greater degree of overhang the wheels need to be stronger to resist the increased over turning moment. Such offsets are quite rare so no economy of scale as it were.
Is the general consensus that I should just sell my firstborn and get ET65 fronts on the basis of being able to sleep at night?
17" Porsche Cup wheels in 9A1 Silver - Alloy Wheels Direct (2461916)
01-29-2021, 06:04 AM
#41
Drifting
Thanks Fred
Is the general consensus that I should just sell my firstborn and get ET65 fronts on the basis of being able to sleep at night?
17" Porsche Cup wheels in 9A1 Silver - Alloy Wheels Direct (2461916)
Is the general consensus that I should just sell my firstborn and get ET65 fronts on the basis of being able to sleep at night?
17" Porsche Cup wheels in 9A1 Silver - Alloy Wheels Direct (2461916)
The reason I was so interested in your Cup 1s is that I have original set on my S4 and agree they suit the 928 brilliantly. Recently I had them powder-coated and had a lot of grief and to-and-fro to the tyre fitters as I was having difficulty getting the RDK switches to seal properly, and had to get round fact that the RDK nuts are NLA. I like having the system all working as it's accurate and reliable in my case (yes I know Fred isn't a fan!), but even if I did what many do and 'defeat' the system, I'd still need to weld up the wheels to cover the 30mm holes! Happily I discovered the correct sealant to use and how to apply and I'm pretty much home (one wheel which I sealed the 'wrong' way has a very very slow leak, but I'll redo that one post-lockdown.
The RDK system adds extra costs (switches, o-ring, protective cover, nut) so when I was getting very frustrated with leaks on an otherwise lovely set of brand-new looking wheels, I even looked round at what it cost to replace the wheels with non-RDK alloys (I think the wheels you've linked to require RDK switches installed) and was horrified by the cost — a few years ago you could pick up running 928s for the cost of four new Cup wheels from Porsche! Hence I focused back on getting my wheels properly airtight, but also why I was curious about the set you obtained.
Really envy our 911/Boxster/944 cousins who have choice of more reasonably priced wheels as they are more plentiful. The unique offset of 928 spec is in effect another 928 'tax', but I like to feel those wonderful engineers at Porsche knew what they were doing when they specified them.
All the best.
Last edited by StratfordShark; 01-29-2021 at 06:17 AM.
01-29-2021, 06:29 AM
#42
Rennlist Member
Factory chrome CupII on mine.
01-29-2021, 10:50 AM
#43
Rennlist Member
I don't know John, but Fred's comments on insurance are potentially crucial.
The reason I was so interested in your Cup 1s is that I have original set on my S4 and agree they suit the 928 brilliantly. Recently I had them powder-coated and had a lot of grief and to-and-fro to the tyre fitters as I was having difficulty getting the RDK switches to seal properly, and had to get round fact that the RDK nuts are NLA. I like having the system all working as it's accurate and reliable in my case (yes I know Fred isn't a fan!), but even if I did what many do and 'defeat' the system, I'd still need to weld up the wheels to cover the 30mm holes! Happily I discovered the correct sealant to use and how to apply and I'm pretty much home (one wheel which I sealed the 'wrong' way has a very very slow leak, but I'll redo that one post-lockdown.
The RDK system adds extra costs (switches, o-ring, protective cover, nut) so when I was getting very frustrated with leaks on an otherwise lovely set of brand-new looking wheels, I even looked round at what it cost to replace the wheels with non-RDK alloys (I think the wheels you've linked to require RDK switches installed) and was horrified by the cost — a few years ago you could pick up running 928s for the cost of four new Cup wheels from Porsche! Hence I focused back on getting my wheels properly airtight, but also why I was curious about the set you obtained.
Really envy our 911/Boxster/944 cousins who have choice of more reasonably priced wheels as they are more plentiful. The unique offset of 928 spec is in effect another 928 'tax', but I like to feel those wonderful engineers at Porsche knew what they were doing when they specified them.
All the best.
The reason I was so interested in your Cup 1s is that I have original set on my S4 and agree they suit the 928 brilliantly. Recently I had them powder-coated and had a lot of grief and to-and-fro to the tyre fitters as I was having difficulty getting the RDK switches to seal properly, and had to get round fact that the RDK nuts are NLA. I like having the system all working as it's accurate and reliable in my case (yes I know Fred isn't a fan!), but even if I did what many do and 'defeat' the system, I'd still need to weld up the wheels to cover the 30mm holes! Happily I discovered the correct sealant to use and how to apply and I'm pretty much home (one wheel which I sealed the 'wrong' way has a very very slow leak, but I'll redo that one post-lockdown.
The RDK system adds extra costs (switches, o-ring, protective cover, nut) so when I was getting very frustrated with leaks on an otherwise lovely set of brand-new looking wheels, I even looked round at what it cost to replace the wheels with non-RDK alloys (I think the wheels you've linked to require RDK switches installed) and was horrified by the cost — a few years ago you could pick up running 928s for the cost of four new Cup wheels from Porsche! Hence I focused back on getting my wheels properly airtight, but also why I was curious about the set you obtained.
Really envy our 911/Boxster/944 cousins who have choice of more reasonably priced wheels as they are more plentiful. The unique offset of 928 spec is in effect another 928 'tax', but I like to feel those wonderful engineers at Porsche knew what they were doing when they specified them.
All the best.
01-29-2021, 03:49 PM
#45
Rennlist Member
[QUOTE=StratfordShark;17197162]Wow that’s brilliant! Let me know if you have any issues transferring the RDK switches - it became my specialist subject last year!
Adrian[/QUOTE
I would hope the RDK sensors are fitted given they are genuine Porsche wheels. The part numbers are slightly different from the info in my files but that may be because of some update.
I think the Cup 1 wheels are the best 928 option cosmetically speaking. Mine are sat gathering dust in the garage pending a revamp at some stage in the future. From new the hubs/spokes were painted body colour of Cobalt Blue- looked awesome when new. I figured that should I ever return to the UK with the 928 I would need them as discussed above.
Adrian[/QUOTE
I would hope the RDK sensors are fitted given they are genuine Porsche wheels. The part numbers are slightly different from the info in my files but that may be because of some update.
I think the Cup 1 wheels are the best 928 option cosmetically speaking. Mine are sat gathering dust in the garage pending a revamp at some stage in the future. From new the hubs/spokes were painted body colour of Cobalt Blue- looked awesome when new. I figured that should I ever return to the UK with the 928 I would need them as discussed above.