Widening rear track with 15mm spaces: Positives & Negatives?
Discussion
Gibbo205 said:
Hi there
Yet another question from me today!
Car has 5mm spacers all round, factory fit. If I change the 5mm rear spacers for 15mm ones in theory no matter how minor will it effect the cars handling both positive and negative?
Any other effects of 15mm rear spacers apart from look?
I've a suspicion that 15mm spacers will take your wheels a little too far 'outboard'. My car (997S.2) has Carrera Sport wheels that are 1/2" wider than the other Porsche wheels for the 997. It also has the same Tequipment 5mm spacers fitted that your car does. Yet another question from me today!
Car has 5mm spacers all round, factory fit. If I change the 5mm rear spacers for 15mm ones in theory no matter how minor will it effect the cars handling both positive and negative?
Any other effects of 15mm rear spacers apart from look?
Compared to standard 19" Porsche 997 wheels, the outside edge of the Carrera Sport wheels sits approx 6.5 mm further outboard. (Half of the 1/2" extra width). Add the spacers and that becomes 11.5mm per side.
At 11.5mm per side over standard, the outside edges of my wheels are already flush with the body (see pic below). Taken further to 15 mm, I think there'd be a risk the tyres could connect with the arches.
fioran0 said:
It's your front track you want as wide as possible.
Even adding the 5mm spacers made a noticeable difference to my car. Again though, I think the OP could also run into tyre/arch contact issues on the front axle of a standard 997S with more than 11-12mm of spacer on each side. If you look at the pic of my car again (above) the outside edges of the fronts are the same 11.5mm further outboard than standard as the rears and already flush with the body.
The clearance issue could be alleviated to some degree by increasing the camber, but there are a couple of downsides. 1) it will reduce the front track again if it's done by just moving the strut tops inwards (maybe adjustable control arms would help?) and 2) the amount of adjustment you could use will be limited by the amount of negative camber you can properly use. For mainly road use, I'd think any more than 1 degree or so would cause a lot of unwanted tramlining and uneven tyre wear.
Edited by Ian_UK1 on Thursday 17th January 13:49
Ian_UK1 said:
Even adding the 5mm spacers made a noticeable difference to my car. Again though, I think the OP could also run into tyre/arch contact issues on the front axle of a standard 997S with more than 11-12mm of spacer on each side. If you look at the pic of my car again (above) the outside edges of the fronts are the same 11.5mm further outboard than standard as the rears and already flush with the body.
The clearance issue could be alleviated to some degree by increasing the camber, but there are a couple of downsides. 1) it will reduce the front track again if it's done by just moving the strut tops inwards (maybe adjustable control arms would help?) and 2) the amount of adjustment you could use will be limited by the amount of negative camber you can properly use. For mainly road use, I'd think any more than 1 degree or so would cause a lot of unwanted tramlining and uneven tyre wear.
Edited by Ian_UK1 on Thursday 17th January 13:49
absolutely, it responds fantastically well to negative camber as does the 996. -2.5 or there about is really about where you want to be if you have fast road only needs imho. get on even more and things just get better but you can start to wear rubber if you dont drive round alot of corners or do track days. i personally think its worth the trade off but im aware not everyone enjoys such a fussy front end on a road car or are happy enough to sacrifice a couple thousand miles from a set of tyres..
for gibbo specifically, i remember you wearing the outside edge of your MPSS pretty badly, getting more camber in there will help alleviate that.
the lower control arms are where its at for this. you get your wider front track and the camber all at once. its a fantastic mod though as Ian says, you want to make sure you dont have fouling issues, ive no idea where the limits are for a C2S with regards control arm shims, camber and clearance.
gibbo, do you still need emailed? if so ill try and shoot you one across tonight if i get a chance.
for gibbo specifically, i remember you wearing the outside edge of your MPSS pretty badly, getting more camber in there will help alleviate that.
the lower control arms are where its at for this. you get your wider front track and the camber all at once. its a fantastic mod though as Ian says, you want to make sure you dont have fouling issues, ive no idea where the limits are for a C2S with regards control arm shims, camber and clearance.
gibbo, do you still need emailed? if so ill try and shoot you one across tonight if i get a chance.
Gibbo205 said:
The 911 loves front camber, think upto -2.3 is OK for street before un-even tyre wear, gotta remember its very light on the front too, but to get more that -1 front camber you need lower GT3 arms.
fioran0 said:
absolutely, it responds fantastically well to negative camber as does the 996. -2.5 or there about is really about where you want to be if you have fast road only needs imho. get on even more and things just get better but you can start to wear rubber if you dont drive round alot of corners or do track days. i personally think its worth the trade off but im aware not everyone enjoys such a fussy front end on a road car or are happy enough to sacrifice a couple thousand miles from a set of tyres..
Very interesting info. I'm doing a lot less suburban driving in the 997 now so setting it up for weekend use sounds like exactly the right way to go. The more responsive the front of my car is, the better I like it, so GT3 control arms and a lot more front camber sound like a must-have next mod. Is there any need to change anything else if I go with the control arms and a -2.5 camber setup? As I'm going to be changing the car at the end of this year - the intention being to buy a 997.2 GT3 - I'm not looking to get too ambitious with modding the '7S for now. I would, however, change anything essential to safe/balanced handling.
Edited by Ian_UK1 on Thursday 17th January 17:33
Ian_UK1 said:
Very interesting info. I'm doing a lot less suburban driving in the 997 now so setting it up for weekend use sounds like exactly the right way to go. The more responsive the front of my car is, the better I like it, so GT3 control arms and a lot more front camber sound like a must-have next mod.
Is there any need to change anything else if I go with the control arms and a -2.5 camber setup? As I'm going to be changing the car at the end of this year - the intention being to buy a 997.2 GT3 - I'm not looking to get too ambitious with modding the '7S for now. I would, however, change anything essential to safe/balanced handling.
Yeah you can do it with just GT3 lower arms, you want to use the 996 lower arms though, they cost far less and it does indeed work fine. To get around -2.0 negative on the front you need around 22-26mm worth of shims for the arms.Is there any need to change anything else if I go with the control arms and a -2.5 camber setup? As I'm going to be changing the car at the end of this year - the intention being to buy a 997.2 GT3 - I'm not looking to get too ambitious with modding the '7S for now. I would, however, change anything essential to safe/balanced handling.
Edited by Ian_UK1 on Thursday 17th January 17:33
The only other thing I'd recommend then doing is thicker front and rear arbs, then you should have a really sorted C2S and it does not cost a lot of money. 996 arms are about £250 each, arbs are about £200 each and geo wise well you can either just take it to any geo place and tell them the settings you want put on the car, cost circa £100-£150. Or you can go to somewhere like centre gravity who will do a great job and he will go over your suspension like a scalpel, he charges about £250ish for a geo I think, but most people leave spending nearly 1k as he will advice you on stuff that should ideally be replaced.
My view is get the settings you want, -2.0 front negative camber, caster 8.50-9.00, front toe neutral and for rear -1.75 negative camber and approx 30 minutes of toe in on the rear axle is a good starting place and will transform the way the car handles. Then for understeer/oversteer you can tune using GT3 ARBs.
P.S. Florian be great if you can drop us a mail please.
-2.0 is better than stock but really you want about -2.5 up front, -2 rear. Caster is 8.0 deg. This is important. More track work and you can run with even more neg.
You may not get this up front with your shocks though. If not then get as much as you can set in the front and set the rear based on this.
Be wary of going much past 14mm total shims per arm unless you want to make buying new arms a hobby.
You may not get this up front with your shocks though. If not then get as much as you can set in the front and set the rear based on this.
Be wary of going much past 14mm total shims per arm unless you want to make buying new arms a hobby.
Edited by fioran0 on Thursday 17th January 19:21
fioran0 said:
-2.0 is better than stock but really you want about -2.5 up front, -2 rear. Caster is 8.0 deg. This is important. More track work and you can run with even more neg.
You may not get this up front with your shocks though. If not then get as much as you can set in the front and set the rear based on this.
Be wary of going much past 14mm total shims per arm unless you want to make buying new arms a hobby.
Remember to drop me an email please m8. You may not get this up front with your shocks though. If not then get as much as you can set in the front and set the rear based on this.
Be wary of going much past 14mm total shims per arm unless you want to make buying new arms a hobby.
Edited by fioran0 on Thursday 17th January 19:21
Ian,
As per other posts. Arms are a straight fit and need nothing else. You may need washers for the compression arm fitting against the arm central bush. These are just regular pick up anywhere washers though. You only need them if the arm on the car is wider than the new arm. I've heard some people fitting to caymans etc needed to. YMMV.
Fwiw, if you are going to upgrade to a 997.2 GT3 then think about getting some Cup arms instead. They are solid bushed and can be used to upgrade the rear of your GT3 when it comes. There's third part options too that may be better on price for essentially the same thing.
This along with adjustable solid rear toe links and locking plates are a must do on any GT3. The cars are very toe sensitive at the back. This keeps toe stable under load and also saves you running for a geo after every decent bump you meet.
If you are going to change up, sharpening the front of your current car is a great idea. For some time fiddling and the price of a geo you can start getting closer to the feeling at the front you will be moving too. It can be your transitional phase
As per other posts. Arms are a straight fit and need nothing else. You may need washers for the compression arm fitting against the arm central bush. These are just regular pick up anywhere washers though. You only need them if the arm on the car is wider than the new arm. I've heard some people fitting to caymans etc needed to. YMMV.
Fwiw, if you are going to upgrade to a 997.2 GT3 then think about getting some Cup arms instead. They are solid bushed and can be used to upgrade the rear of your GT3 when it comes. There's third part options too that may be better on price for essentially the same thing.
This along with adjustable solid rear toe links and locking plates are a must do on any GT3. The cars are very toe sensitive at the back. This keeps toe stable under load and also saves you running for a geo after every decent bump you meet.
If you are going to change up, sharpening the front of your current car is a great idea. For some time fiddling and the price of a geo you can start getting closer to the feeling at the front you will be moving too. It can be your transitional phase
Gibbo205 said:
Yeah you can do it with just GT3 lower arms, you want to use the 996 lower arms though, they cost far less and it does indeed work fine. To get around -2.0 negative on the front you need around 22-26mm worth of shims for the arms.
The only other thing I'd recommend then doing is thicker front and rear arbs, then you should have a really sorted C2S and it does not cost a lot of money. 996 arms are about £250 each, arbs are about £200 each and geo wise well you can either just take it to any geo place and tell them the settings you want put on the car, cost circa £100-£150. Or you can go to somewhere like centre gravity who will do a great job and he will go over your suspension like a scalpel, he charges about £250ish for a geo I think, but most people leave spending nearly 1k as he will advice you on stuff that should ideally be replaced.
My view is get the settings you want, -2.0 front negative camber, caster 8.50-9.00, front toe neutral and for rear -1.75 negative camber and approx 30 minutes of toe in on the rear axle is a good starting place and will transform the way the car handles. Then for understeer/oversteer you can tune using GT3 ARBs.
The only other thing I'd recommend then doing is thicker front and rear arbs, then you should have a really sorted C2S and it does not cost a lot of money. 996 arms are about £250 each, arbs are about £200 each and geo wise well you can either just take it to any geo place and tell them the settings you want put on the car, cost circa £100-£150. Or you can go to somewhere like centre gravity who will do a great job and he will go over your suspension like a scalpel, he charges about £250ish for a geo I think, but most people leave spending nearly 1k as he will advice you on stuff that should ideally be replaced.
My view is get the settings you want, -2.0 front negative camber, caster 8.50-9.00, front toe neutral and for rear -1.75 negative camber and approx 30 minutes of toe in on the rear axle is a good starting place and will transform the way the car handles. Then for understeer/oversteer you can tune using GT3 ARBs.
fioran0 said:
Ian,
As per other posts. Arms are a straight fit and need nothing else. You may need washers for the compression arm fitting against the arm central bush. These are just regular pick up anywhere washers though. You only need them if the arm on the car is wider than the new arm. I've heard some people fitting to caymans etc needed to. YMMV.
Fwiw, if you are going to upgrade to a 997.2 GT3 then think about getting some Cup arms instead. They are solid bushed and can be used to upgrade the rear of your GT3 when it comes. There's third part options too that may be better on price for essentially the same thing.
This along with adjustable solid rear toe links and locking plates are a must do on any GT3. The cars are very toe sensitive at the back. This keeps toe stable under load and also saves you running for a geo after every decent bump you meet.
If you are going to change up, sharpening the front of your current car is a great idea. For some time fiddling and the price of a geo you can start getting closer to the feeling at the front you will be moving too. It can be your transitional phase
Many thanks to both of you for taking the time to share your knowledge/experience and make the above recommendations. It's really appreciated.As per other posts. Arms are a straight fit and need nothing else. You may need washers for the compression arm fitting against the arm central bush. These are just regular pick up anywhere washers though. You only need them if the arm on the car is wider than the new arm. I've heard some people fitting to caymans etc needed to. YMMV.
Fwiw, if you are going to upgrade to a 997.2 GT3 then think about getting some Cup arms instead. They are solid bushed and can be used to upgrade the rear of your GT3 when it comes. There's third part options too that may be better on price for essentially the same thing.
This along with adjustable solid rear toe links and locking plates are a must do on any GT3. The cars are very toe sensitive at the back. This keeps toe stable under load and also saves you running for a geo after every decent bump you meet.
If you are going to change up, sharpening the front of your current car is a great idea. For some time fiddling and the price of a geo you can start getting closer to the feeling at the front you will be moving too. It can be your transitional phase
I'm going to investigate the Cup arms (or aftermarket alternatives) as it makes a lot of sense to be able to re-use them in future. As I already know Chris at CG (he's set up a few cars for me now) I'll entrust the work to him.
Hopefully, I will have the mods installed by the time Spring and some improved weather arrive and I'm really looking forward to seeing how much more front-end bite the car will have - it's a real weakness in the standard 997S setup.
Off the public roads, I'm also interested in how the car will handle on limit. If there's a lot more front-end grip and no more at the rear, then the car could be even more of a sideways tool than it was last time I was at Bruntingthorpe! At the moment, the car is running less toe on the rear then normal - an experiment to see if, in the absence of being able to dial-in a lot of front camber on the standard suspension, it would help turn-in and response. This it did for most normal purposes, but it has made the rear end a little loose (and the car a bit of a handful) on the limit. If the mods on the front are going to give me vastly-improved turn-in and response anyway, I'm thinking it might be a good idea to put the toe back on the rear at the same time.
Edited by Ian_UK1 on Friday 18th January 08:50
Ian_UK1 said:
Many thanks to both of you for taking the time to share your knowledge/experience and make the above recommendations. It's really appreciated.
I'm going to investigate the Cup arms (or aftermarket alternatives) as it makes a lot of sense to be able to re-use them in future. As I already know Chris at CG (he's set up a few cars for me now) so I'll entrust the work to him.
Hopefully, I will have the mods installed by the time Spring and some improved weather arrive and I'm really looking forward to seeing how much more front-end bite the car will have - it's a real weakness in the standard 997S setup.
Off the public roads, I'm also interested in how the car will handle on limit. If there's a lot more front-end grip and no more at the rear, then the car could be even more of a sideways tool than it was last time I was at Bruntingthorpe! At the moment, the car is running less toe on the rear then normal - an experiment to see if, in the absence of being able to dial-in a lot of front camber on the standard suspension, it would help turn-in and response. This it did for most normal purposes, but it has made the rear end a little loose (and the car a bit of a handful) on the limit. If the mods on the front are going to give me vastly-improved turn-in and response anyway, I'm thinking it might be a good idea to put the toe back on the rear at the same time.
Regards to the rear being loose, more toe in add stability, especially under braking! Wider rear tyres could help, 305's if your currently using 295's, also maybe some 5-15mm rears spacer as theory is a wider track within reason gives more theorectical grip and a wider track normally means better compliance over bumps. Also remember adding GT3 arms will widen front track considerably, circa 22-28mm depending on how many shims you use so that will give a big improvement and as such it might be a requirement to widen the rear track a bit when widening the front so much. But I am not sure so maybe Florian can comment better on this. My view is if you increase the front track by circa 25mm, then surely it makes sense or is logical to increase the rear track as well, but like I say Florian shall know better!I'm going to investigate the Cup arms (or aftermarket alternatives) as it makes a lot of sense to be able to re-use them in future. As I already know Chris at CG (he's set up a few cars for me now) so I'll entrust the work to him.
Hopefully, I will have the mods installed by the time Spring and some improved weather arrive and I'm really looking forward to seeing how much more front-end bite the car will have - it's a real weakness in the standard 997S setup.
Off the public roads, I'm also interested in how the car will handle on limit. If there's a lot more front-end grip and no more at the rear, then the car could be even more of a sideways tool than it was last time I was at Bruntingthorpe! At the moment, the car is running less toe on the rear then normal - an experiment to see if, in the absence of being able to dial-in a lot of front camber on the standard suspension, it would help turn-in and response. This it did for most normal purposes, but it has made the rear end a little loose (and the car a bit of a handful) on the limit. If the mods on the front are going to give me vastly-improved turn-in and response anyway, I'm thinking it might be a good idea to put the toe back on the rear at the same time.
Then don't forget ARB's you can fine tune a cars handling dynamics using ARBs, which is exactly what I've being doing, C2S bar naturally gives me push as its a puny 19.7x2.6mm if memory serves me right. I then tried an adjustable GT3 gen2 bar (same as GT2) which is circa 25x4.4mm so substancially stiffer, this gave me too much oversteer. So next stop is regular C4 ARB and see how that effects the balance. Another option which would work would be gen1 GT3 bar for me too and adjust it along with front to get the handling I want.
Also bear in mind, setting ARBs too stiff ruins wet weather handling, back in the old days when racing at the track in the wet, race teams would even disconnects the ARBs for wet races, so you've got to find a balance. On a UK road where wet weather is an issue normally a softish ARB setup is better, but if the car is a dry track day weapon that stiffening ARBs will improve things further.
Edited by Gibbo205 on Friday 18th January 09:00
fioran0 said:
Chad speed said:
But if you want to achieve it without altering the scrub radius then it will cost you a whole lot more than a set of spacers.
See posts ref two piece control armsForgive me if I'm going over old ground and most of you probably know this already but just to reiterate what scrub radius is:
On the hub strike a line through the top outer ball joint down through the lower outer ball joint. Looking from the front of the car this line will be inclined inwards at the top (kingpin inclination).
Carry this line downwards until it meets the ground. Ideal scrub radius is when the centre line of the width of the tyre coincides precisely with the point that the kingpin line meets the ground.
Moving away from this ideal will increase the weight of the steering and dull feel. Note also that increasing or reducing tyre diameter will also effect scrub radius to a small degree as well.
Apologies for labouring the point, let us know how you get on.
Edited by Chad speed on Friday 18th January 09:34
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