997/996 GT3 dynamics

[evodarren]

Jamie

You can have a drive of mine anytime to get your fix. I need to go out in your wife's SC

[LaSource]

JMo22 said:

Thanks for comments guys.

Does anybody know what weight savings the BBS LMs offer over the standard 996.1 GT3 BBS wheels? Only been able to find a decade old PH thread, which surprisingly given their popularity seemed to suggest no difference? Seems to be easier to pick up spares of the original wheels these days vs LMs so probably worth carrying on risking using those?

Also debating whether to replace front discs with Alcons when the time comes but not sure the £/kg saved stacks up as they are made in such low volume nowadays.

Appreciate any thoughts!

I have done some weight comparisons between BBM LMs and 6GT3 Mk2 wheels...will need to find where I wrote down the numbers! IIRC the LMs were lighter but can't say off top of head whether a material difference or not.

[Slippydiff]

LaSource said:

JMo22 said:

Thanks for comments guys.

Does anybody know what weight savings the BBS LMs offer over the standard 996.1 GT3 BBS wheels? Only been able to find a decade old PH thread, which surprisingly given their popularity seemed to suggest no difference? Seems to be easier to pick up spares of the original wheels these days vs LMs so probably worth carrying on risking using those?

Also debating whether to replace front discs with Alcons when the time comes but not sure the £/kg saved stacks up as they are made in such low volume nowadays.

Appreciate any thoughts!

I have done some weight comparisons between BBM LMs and 6GT3 Mk2 wheels...will need to find where I wrote down the numbers! IIRC the LMs were lighter but can't say off top of head whether a material difference or not.

BBS E88 18x8.5 = 20lbs : 9.1Kg
BBS E88 18x11 = 21.5lbs : 9.8Kg

BBS LM 18x8.5 = 21.6lbs or 9.8Kg
BBS LM 18x11 = 26.9lbs or 12.2Kg

Mk1GT3 18x8 = 25.35lbs or 11.5kg
MK1 GT3 18x10 = 28.88lbs or 13.1kg

Mk2 GT3 OE 18x8.5 = 27.00lbs 12.25Kg
Mk2 GT3 OEM 18x11 = 29.98 or 13.6Kg

[ttdan]

Is there some magic formula to convert un sprung weight to the equivalent sprung weight?

[isaldiri]

ttdan said:

Is there some magic formula to convert un sprung weight to the equivalent sprung weight?

Not really because the distance from rotational centre is also relevant ie the further the more important the saving. Having seen numbers range from 3-8x sprung weight saving, basically just assume anyone who makes anything that saves unsprung weight anywhere tends to claim a rather high multiple

[Taffy66]

In Slippy's example above, if you compare the lightest BBS E88 to the OEM 996.2 GT3 it translates to a saving of 14Kg unsprung weight.This is a huge saving and would be very noticeable in terms of turn-in,bump absorption and even acceleration.
I'm pretty dumbfounded at this as the OEMs are way heavier than i expected.

[Slippydiff]

Taffy66 said:

In Slippy's example above, if you compare the lightest BBS E88 to the OEM 996.2 GT3 it translates to a saving of 14Kg unsprung weight.This is a huge saving and would be very noticeable in terms of turn-in,bump absorption and even acceleration.
I'm pretty dumbfounded at this as the OEMs are way heavier than i expected.

OE’s are heavy (ish) but strong and durable. E88’s are featherweight in comparison, but one good pothole impact would see a rim section consigned to the scrap aluminium skip. You pays your money and takes your choice...

[Steve Rance]

The LM are a good compromise for road track. To be honest, although unsprung weight savings are useful, the biggest changes in driving experience in these cars is found by set up and damping. If I were looking at £ for £ rewards on. 996/7 GT3 I’d start on dampers and chassis. £4K will bring a lot more marginal gains there. The best is simply a set up the 997 really benefits from a diff upgrade which is around £1500 for guards internals. I saw track wheels as really merely something to protect the OEM units from constant tyre changes and litter rash

[Dr S]

Steve Rance said:

The LM are a good compromise for road track. To be honest, although unsprung weight savings are useful, the biggest changes in driving experience in these cars is found by set up and damping. If I were looking at £ for £ rewards on. 996/7 GT3 I’d start on dampers and chassis. £4K will bring a lot more marginal gains there. The best is simply a set up the 997 really benefits from a diff upgrade which is around £1500 for guards internals. I saw track wheels as really merely something to protect the OEM units from constant tyre changes and litter rash

Always quality comments from you, Steve. Your posts are always highlights on this forum

[Steve Rance]

Thank you. Much appreciated

[lemmingjames]

What about tyre weight and the air inside?

Hasn't anyone looked into jdm wheels, is volks and rays?

[Porsche911R]

Slippydiff said:

BBS E88 18x8.5 = 20lbs : 9.1Kg
BBS E88 18x11 = 21.5lbs : 9.8Kg

BBS LM 18x8.5 = 21.6lbs or 9.8Kg
BBS LM 18x11 = 26.9lbs or 12.2Kg

Mk1GT3 18x8 = 25.35lbs or 11.5kg
MK1 GT3 18x10 = 28.88lbs or 13.1kg

Mk2 GT3 OE 18x8.5 = 27.00lbs 12.25Kg
Mk2 GT3 OEM 18x11 = 29.98 or 13.6Kg

all pretty heavy in todays standards.
when a 20" BBS Fir is 17lbs

and even a OZ cheapo is 17.6 lbs for the 8.5 OZ Alleggerita HLT 11" is 23lbs and only £1,770 as well for 4 , must be the wheel of choice for a track car, or even road car and the cheapest , and maybe strongest.

fitting those over oem is 15kg unsprung and rotation mass saving , that you would feel big time.

LM for show ! OZ for go ;-) E88 for the rich.

Edited by Porsche911R on Tuesday 12th February 08:32

[MDL111]

can't get the FI / FI-R as 18 though I believe

[Slippydiff]

MDL111 said:

can't get the FI / FI-R as 18 though I believe

This ^ and if you could, they’d be £6k plus based on the price of the 19/20” versions.
The OZ are light, but hardly the last word in aesthetics (they’re known to crack, or were) too.

[Porsche911R]

MDL111 said:

can't get the FI / FI-R as 18 though I believe

that's why I said buy "OZ Alleggerita HLT" and still save 15kg for £2k with a nice picture to match :-)

[LaSource]

Steve Rance said:

The LM are a good compromise for road track. To be honest, although unsprung weight savings are useful, the biggest changes in driving experience in these cars is found by set up and damping. If I were looking at £ for £ rewards on. 996/7 GT3 I’d start on dampers and chassis. £4K will bring a lot more marginal gains there. The best is simply a set up the 997 really benefits from a diff upgrade which is around £1500 for guards internals. I saw track wheels as really merely something to protect the OEM units from constant tyre changes and litter rash

Totally agree. Diff, dampers, geo (I guess maybe front brakes as well)….all you need to make a 996/7 from a great car to a superb one for road and track use. The spring stiffness will determine whether it becomes more track than road, but even a track orientated car is good fun for a sunday drive (but perhaps not on the most pothole-ly B-road or London zone 1 20mph speed bumps!)

Porsche911R said:

all pretty heavy in todays standards.
when a 20" BBS Fir is 17lbs

and even a OZ cheapo is 17.6 lbs for the 8.5 OZ Alleggerita HLT 11" is 23lbs and only £1,770 as well for 4 , must be the wheel of choice for a track car, or even road car and the cheapest , and maybe strongest.

fitting those over oem is 15kg unsprung and rotation mass saving , that you would feel big time.

LM for show ! OZ for go ;-) E88 for the rich.

Yeah fair point the OZ's are a value buy for track use if one needs another set of wheels.
'LM for show' goes a long way with GT3s though

Slippydiff said:

This ^ and if you could, they’d be £6k plus based on the price of the 19/20” versions.
The OZ are light, but hardly the last word in aesthetics (they’re known to crack, or were) too.

Yes I recall disco posting about cracking his OZ's spokes at the ring (but perhaps that was an after effect of an off and not the cause of it). Are there other reports of cracks?

Edited by LaSource on Tuesday 12th February 13:10

[LaSource]

Steve Rance said:

The LM are a good compromise for road track. To be honest, although unsprung weight savings are useful, the biggest changes in driving experience in these cars is found by set up and damping. If I were looking at £ for £ rewards on. 996/7 GT3 I’d start on dampers and chassis. £4K will bring a lot more marginal gains there. The best is simply a set up the 997 really benefits from a diff upgrade which is around £1500 for guards internals. I saw track wheels as really merely something to protect the OEM units from constant tyre changes and litter rash

Totally agree. Diff, dampers, geo (I guess maybe front brakes as well)….all you need to make a 996/7 from a great car to a superb one for road and track use. The spring stiffness will determine whether it becomes more track than road, but even a track orientated car is good fun for a sunday drive (but perhaps not on the most pothole-ly B-road or London zone 1 20mph speed bumps!)

Porsche911R said:

all pretty heavy in todays standards.
when a 20" BBS Fir is 17lbs

and even a OZ cheapo is 17.6 lbs for the 8.5 OZ Alleggerita HLT 11" is 23lbs and only £1,770 as well for 4 , must be the wheel of choice for a track car, or even road car and the cheapest , and maybe strongest.

fitting those over oem is 15kg unsprung and rotation mass saving , that you would feel big time.

LM for show ! OZ for go ;-) E88 for the rich.

Yeah fair point the OZ's are a value buy for track use if one needs another set of wheels.
'LM for show' goes a long way with GT3s though

Slippydiff said:

This ^ and if you could, they’d be £6k plus based on the price of the 19/20” versions.
The OZ are light, but hardly the last word in aesthetics (they’re known to crack, or were) too.

Yes I recall disco posting about cracking his OZ's spokes at the ring (but perhaps that was an after effect of an off and not the cause of it). Are there other reports of cracks?

Edited by LaSource on Tuesday 12th February 13:10

[BrotherMouzone]

LaSource said:

Slippydiff said:

This ^ and if you could, they’d be £6k plus based on the price of the 19/20” versions.
The OZ are light, but hardly the last word in aesthetics (they’re known to crack, or were) too.

Yes I recall discocolin posting about cracking his OZ's spokes at the ring (but perhaps that was an after effect of an off and not the cause of it). Are there other reports of cracks?

NXI20 has had a few cracked.

http://911uk.com/viewtopic.php?t=124640

[Digga]

Taffy66 said:

In Slippy's example above, if you compare the lightest BBS E88 to the OEM 996.2 GT3 it translates to a saving of 14Kg unsprung weight.This is a huge saving and would be very noticeable in terms of turn-in,bump absorption and even acceleration.
I'm pretty dumbfounded at this as the OEMs are way heavier than i expected.

Pretty much the weight difference between steel or PCCB brakes and, even with the BBS E88's, for less money too.

[Steve Rance]

Personally, unless I'm racing, I'm not keen on lightweight wheels on track cars unless they are extremely strong and those are generally also extremely expensive