3.2 Carrera track widening
08-17-2010, 09:39 AM
#34
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Talking down to you? 
You come on here with like no posts stating you want to improve your handling by increasing the rear track. That isn't going to happen. One can only assume you have no experience with a 911 and are either timid about having the end come around, or have already been scared by it. How in the heck do I know what you've done and what clubs to you belong to? If Porsche could have taken this chassis and made it handle better with a wider track, I'm pretty sure they would have made that discovery.
Lastly, please speak in clearer terms. Your phrases in parenthesis aren't totally clear or commonly used.
Ken has also stated the truth that you should spend some time and attention on your suspension. Then go to wider wheels and tires if you want more grip.
You haven't even taken the time to even put your location or any other info in your signature.
You come on here with like no posts stating you want to improve your handling by increasing the rear track. That isn't going to happen. One can only assume you have no experience with a 911 and are either timid about having the end come around, or have already been scared by it. How in the heck do I know what you've done and what clubs to you belong to? If Porsche could have taken this chassis and made it handle better with a wider track, I'm pretty sure they would have made that discovery.Lastly, please speak in clearer terms. Your phrases in parenthesis aren't totally clear or commonly used.
Ken has also stated the truth that you should spend some time and attention on your suspension. Then go to wider wheels and tires if you want more grip.
You haven't even taken the time to even put your location or any other info in your signature.
See, we can't help ourselves… I write in a convoluted style and you can't stop being condescending, even after I brought it to your attention… Now I'm "too timid" etc... Oyyy.
Ok, back to the topic:
Similar to setting tire pressures, Porsche, like lesser OEM's, has other considerations besides maximum track performance in determining wheel sizes and outer face locations:
1. Product hierarchy and upgrade path - base car is underspec'ed and customers can (are lured to) choose higher spec factory or dealer equipment for hefty margins (such as wider wheels).
2. Chain clearance. Yes, this is a consideration, since, thanks to weight distribution, 911's have been commonly used at least in Europe as winter cars including for ski trips high up the Alps (with the narrower tires of course).
3. Bearing durability - every OEM does this: They will keep the hub and bearing locations and track width common (designed for the higher duty wider wheels which fill out the wheels wells), and the narrower wheels will end up not using all the fender width available but be "centered" over the bearings in order to protect bearing life for warranty, liability and reputation.
It would be a conscious choice on my part if I go with spacers and/or smaller offset wheels at the expense of bearing life, not something Porsche would risk.
Agreed, all suspension parameters on an old car need to be checked and brought up to snuff, but that does not preclude taking in parallel some quick and easy steps. I may not be able to observe the net effect of widening the rear track, but on this car it seems like a "low hanging fruit".
And I will try to be clearer in my future writing - thanks for the feedback and let me know how I'm doing...
Tschuess,
Yoram
08-17-2010, 09:49 AM
#35
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Gents,
Thank you all for all the discussion and insights. I did ignite quite a few flares here and stirred up a rather big thread, which is good. I will take all your inputs, including Ed's, under serious consideration as I experiment with the new toy. And will come back for more good advice...
Cheers,
Yoram
Thank you all for all the discussion and insights. I did ignite quite a few flares here and stirred up a rather big thread, which is good. I will take all your inputs, including Ed's, under serious consideration as I experiment with the new toy. And will come back for more good advice...
Cheers,
Yoram
08-17-2010, 10:26 AM
#36
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Ed, I could go on for paragraphs explaining why this is a bad idea. There would be a thread-division over the merits and failings of the myriad of different wheels blah blah blah. Changing track on one axle is foolish. Both axles is twice as foolish. Wheel offset, scrub radius, and roll center should not be tampered with. This is one of those things where it's all been done. The book was written on this decades ago and there is a good solution. A 911 is really a pleasant and easily tuned chassis.
Everything can and should be tampered with! Stock suspensions end up always, even on Porsches, as compromises among many objectives - transient handling, maximum steady state grip, traction and braking stability, ride, NVH, durability, packaging space, servicing, cost, etc. etc. Whenever the original set of objectives shifts in weighting due to personal preference or mode of use we go in and tamper. Agreed that widening the track in the front will increase an already positive scrub radius and result in greater steering effort at low speed and kickback at all speeds, but it remains to be seen (by me) whether it is not a worthy price to pay for a higher cornering limit. And we change the roll centers every time we lower our Porsches to Euro or racing ride height. (BTW, widening the rear track by 2" on a 911 has a negligible effect on roll center height). And actually changing track width on one axle only may be more foolish than on both because it is likely to change more the original handling balance. Changing front wheel offset on a powerful FWD or AWD car is a big issue as it may increase torque-steer to unmanageable levels. Lucky me, my 911 is RWD...
As a few folks mentioned here, many of the suspension and tire pressure settings were chosen for liability and "common denominator" reasons, not for maximizing fun.
We must not forget that (blasphemy!) in modern perspective the 911 suspension is extremely primitive, which is a big part of the car's character and entertaining handling, but also a good reason to tinker.
Cheers,
Yoram
08-17-2010, 10:54 AM
#37
Race Car
Yoram. I would encourage you to enjoy your car - primarily thru modifications and "tampering". Keep in mind that dramatic positive scrub radius is more of an issue under braking. later ABS cars HAVE to have a neutral, or slightly negetive scrub radius to function. the same with your RWD 911. You will have pronounced control arm and steering component failures. This does not remain to be seen by me - I have seen this and you will not gain any cornering limit. The 930 had different REAR control arms because of the track-increase. Not only were they extended outward to compensate for the track increase, but they were actually shorter with different pick-up points to maintain a roll center and offset negetive dive/squat qualities. I am certain that Porsche did not compramise suspension geometry in order to upsale wheels. Any available options maintained suspension integrity, and more importantly - safety.
Good luck.
Good luck.
08-17-2010, 11:00 AM
#38
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I think Yoram is bound and determined to justify to himself that there is some handling benefit to be gained with spacers, other than pure aesthetics. It seems his mind is made up.
08-17-2010, 11:14 AM
#39
Race Car
There are many well documented approaches to this. This has been done before. I will contend that a stock 911 will out handle an otherwise stock setup with wider track.
08-17-2010, 03:53 PM
#40
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Whalebird,
Everything can and should be tampered with! Stock suspensions end up always, even on Porsches, as compromises among many objectives - transient handling, maximum steady state grip, traction and braking stability, ride, NVH, durability, packaging space, servicing, cost, etc. etc. Whenever the original set of objectives shifts in weighting due to personal preference or mode of use we go in and tamper. Agreed that widening the track in the front will increase an already positive scrub radius and result in greater steering effort at low speed and kickback at all speeds, but it remains to be seen (by me) whether it is not a worthy price to pay for a higher cornering limit. And we change the roll centers every time we lower our Porsches to Euro or racing ride height. (BTW, widening the rear track by 2" on a 911 has a negligible effect on roll center height). And actually changing track width on one axle only may be more foolish than on both because it is likely to change more the original handling balance. Changing front wheel offset on a powerful FWD or AWD car is a big issue as it may increase torque-steer to unmanageable levels. Lucky me, my 911 is RWD...
As a few folks mentioned here, many of the suspension and tire pressure settings were chosen for liability and "common denominator" reasons, not for maximizing fun.
We must not forget that (blasphemy!) in modern perspective the 911 suspension is extremely primitive, which is a big part of the car's character and entertaining handling, but also a good reason to tinker.
Cheers,
Yoram
Everything can and should be tampered with! Stock suspensions end up always, even on Porsches, as compromises among many objectives - transient handling, maximum steady state grip, traction and braking stability, ride, NVH, durability, packaging space, servicing, cost, etc. etc. Whenever the original set of objectives shifts in weighting due to personal preference or mode of use we go in and tamper. Agreed that widening the track in the front will increase an already positive scrub radius and result in greater steering effort at low speed and kickback at all speeds, but it remains to be seen (by me) whether it is not a worthy price to pay for a higher cornering limit. And we change the roll centers every time we lower our Porsches to Euro or racing ride height. (BTW, widening the rear track by 2" on a 911 has a negligible effect on roll center height). And actually changing track width on one axle only may be more foolish than on both because it is likely to change more the original handling balance. Changing front wheel offset on a powerful FWD or AWD car is a big issue as it may increase torque-steer to unmanageable levels. Lucky me, my 911 is RWD...
As a few folks mentioned here, many of the suspension and tire pressure settings were chosen for liability and "common denominator" reasons, not for maximizing fun.
We must not forget that (blasphemy!) in modern perspective the 911 suspension is extremely primitive, which is a big part of the car's character and entertaining handling, but also a good reason to tinker.
Cheers,
Yoram
Now you say you want to increase performance. I have to go back to my recommendation on the 9" wheels. Just go get some El Cheapo knockoffs. They'll return more bang for your buck in terms of performance and looks. You'll be able to run big meaty 245s and they will go right out to the edge of your fender. Put the 7"s on the front with 205s.
There is no religion about keeping the stock tire sizes, no matter how much you try to make it so.
08-17-2010, 06:06 PM
#41
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Rusnak,
Good point. Let me try to explain myself: I intend to proceed gradually with some changes (which may or may not turn out to be improvements, I realize) based on "quick and easy picks" first, and also based on what I discover as I go to be more important (or bothering...). I do not intend at this point to turn the car into a track beast, but extrapolating from my past this may happen over time (and money...).
First goal is street (eh, country road) usable fun with good margins of safety. Track performance will come later.
I have personally found that cars with very high cornering limits such as C6 Corvette or Lotus Elise (oops, is it allowed to mention Brand X here?...) are difficult for me to fully enjoy on public roads because they just go "on rails" without much slip up into very high G levels (and hence speeds in corners), often too high for available reaction time and space. I think Ed calls this "timid". So I would rather have less cornering stiffness for public road use but keep the limit as high and as predictable as possible.
I am wondering whether tires that are very wide and stiff, such as low profile 245's on 9" rims (what diameter? 16?), will be too camber sensitive, which I recall semi-fondly from my 944TS. This leads to less predictable transitions. Sounds like you found this not to be the case?
No, it's not a religion at all, just the current phase in the exploration...
Thanks!
Yoram
Good point. Let me try to explain myself: I intend to proceed gradually with some changes (which may or may not turn out to be improvements, I realize) based on "quick and easy picks" first, and also based on what I discover as I go to be more important (or bothering...). I do not intend at this point to turn the car into a track beast, but extrapolating from my past this may happen over time (and money...).
First goal is street (eh, country road) usable fun with good margins of safety. Track performance will come later.
I have personally found that cars with very high cornering limits such as C6 Corvette or Lotus Elise (oops, is it allowed to mention Brand X here?...) are difficult for me to fully enjoy on public roads because they just go "on rails" without much slip up into very high G levels (and hence speeds in corners), often too high for available reaction time and space. I think Ed calls this "timid". So I would rather have less cornering stiffness for public road use but keep the limit as high and as predictable as possible.
I am wondering whether tires that are very wide and stiff, such as low profile 245's on 9" rims (what diameter? 16?), will be too camber sensitive, which I recall semi-fondly from my 944TS. This leads to less predictable transitions. Sounds like you found this not to be the case?
No, it's not a religion at all, just the current phase in the exploration...
Thanks!
Yoram
08-17-2010, 06:18 PM
#42
I haddah Google dat
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Camber sensitive? What's wrong with dialing in a bunch of negative camber? Even so, I find that even at less than 1 degree negative the 9s still grip well and wear evenly. I think you must be over-analyzing the effect of adding another 20mm to the tread width.
check out Chuck Moreland's store: Elephant Racing. There is a lot of info pertaining to these cars there. Also Steve Weiner, Pete Zimmermann, and others here and on Pelican have a lot of first hand knowledge.
I guess what keeps bugging me is that if you buy the spacers, they will become paperweights as soon as you come to your senses and add additional rear rubber. To me, a logical starting place is to change or replace your rubber suspension bushings with either new rubber ones or the trick poly bronze ones.
check out Chuck Moreland's store: Elephant Racing. There is a lot of info pertaining to these cars there. Also Steve Weiner, Pete Zimmermann, and others here and on Pelican have a lot of first hand knowledge.
I guess what keeps bugging me is that if you buy the spacers, they will become paperweights as soon as you come to your senses and add additional rear rubber. To me, a logical starting place is to change or replace your rubber suspension bushings with either new rubber ones or the trick poly bronze ones.
08-17-2010, 06:35 PM
#43
Race Car
Yoram. I think you have an attainable goal. I'm just not so certain that wider track will give you anything your looking for...in theory it should'nt.
In racing circles, many will tell you that loose is fast. Keep things on the soft side, just isolate the given components with healthy bushings, assuming shocks etc. are good. A nice set of adjustable spherical swaybar endlinks(rear) and weltmeister poly swaybar bushings will give you a healthy confidence in the chassis.
There was a discussion some time ago about tires. I recall many 911 drivers with torsion bar cars were having a hard time finding a nice round-edged tire - almost an all season tire by todays standards. The current trend in square, stiff walled low profile tires were not optimal for the T-bar chassis. Remember the Yoko A008P(for porsche). The complaint was a lack of slip angle in the newer tires that so many 911 owners had become used too. I think Rusnak has hit the magic button. get some 9" rears and a modest set of performance tires. Forget the R-compounds and go for a pleabian-class set of Dunlops or falkens, all the while refresh ALL suspension (neatrix spring plate bushings are fine on the street) and go push the limits on the track at a PCA drivers Ed. Report back here with your findings - You will not find a single "track beast" with wheel spacers as a performance upgrade.
In racing circles, many will tell you that loose is fast. Keep things on the soft side, just isolate the given components with healthy bushings, assuming shocks etc. are good. A nice set of adjustable spherical swaybar endlinks(rear) and weltmeister poly swaybar bushings will give you a healthy confidence in the chassis.
There was a discussion some time ago about tires. I recall many 911 drivers with torsion bar cars were having a hard time finding a nice round-edged tire - almost an all season tire by todays standards. The current trend in square, stiff walled low profile tires were not optimal for the T-bar chassis. Remember the Yoko A008P(for porsche). The complaint was a lack of slip angle in the newer tires that so many 911 owners had become used too. I think Rusnak has hit the magic button. get some 9" rears and a modest set of performance tires. Forget the R-compounds and go for a pleabian-class set of Dunlops or falkens, all the while refresh ALL suspension (neatrix spring plate bushings are fine on the street) and go push the limits on the track at a PCA drivers Ed. Report back here with your findings - You will not find a single "track beast" with wheel spacers as a performance upgrade.
08-17-2010, 06:35 PM
#44
Dude...
Decide what you want to do...
A box-stock 3.2 is WAY faster than anyone should ever drive on the street, so any mods you do are purely cosmetic.... and that's ok... do what looks good.
For track, you have to do bars, sways, shocks, and alignment to get the benefit from larger tires.. that's at least $10-15K and the car will drive like sh*t on the street.
I'm no engineer, but Porsche designed the wheel offsets for a reason... large spacers could screw-up the suspension geometry, and put load on the wheel bearings.
I run 9" rears on my SC racecar, and have to replace rear wheel bearings twice a season, if that tells you anything.
Decide what you want to do...
A box-stock 3.2 is WAY faster than anyone should ever drive on the street, so any mods you do are purely cosmetic.... and that's ok... do what looks good.
For track, you have to do bars, sways, shocks, and alignment to get the benefit from larger tires.. that's at least $10-15K and the car will drive like sh*t on the street.
I'm no engineer, but Porsche designed the wheel offsets for a reason... large spacers could screw-up the suspension geometry, and put load on the wheel bearings.
I run 9" rears on my SC racecar, and have to replace rear wheel bearings twice a season, if that tells you anything.
08-17-2010, 06:37 PM
#45
Rennlist Member
I've got 255's, 17" in diameter, so much stiffer that 16's, in the rear. Remind me to take pics of "camber sensitivity" at -2.5 degrees. They wear unevenly, but there are no negative issues in performance or handling.
I think you're overanalyzing this without having the experience of what the car is actually like to flog. Don't believe the Mazda commercials bragging there are more Mazdas raced than any other. There are a ton of 911's in all stages of tweaks. Learn from what others have done. Spacers aren't part of anyone's formula for improving handling.
Ruby has evolved a bunch over the years, and is probably at a pretty aggressive level, and still retaining street drivability. No spacers required.
I think you're overanalyzing this without having the experience of what the car is actually like to flog. Don't believe the Mazda commercials bragging there are more Mazdas raced than any other. There are a ton of 911's in all stages of tweaks. Learn from what others have done. Spacers aren't part of anyone's formula for improving handling.
Ruby has evolved a bunch over the years, and is probably at a pretty aggressive level, and still retaining street drivability. No spacers required.