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Square or Staggered tyre setup?

 
Old 02-26-2015, 06:05 PM
  #31  
Paulyy
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Originally Posted by odb812 View Post
What Lee's saying is correct: unless dictated by class, you should design your suspension around wheel/tire package and design aero around wheel/tire/suspension. That being said, I think you could still make things work with your setup with the adjustable sway bars. Try stiffening the front bar and softening the rear. Worst case, you can disconnect the rear bar. That would probably help with your lack of LSD, too.



This doesn't make any sense. Wider front tires will make a car tend to oversteer more at the limit given the same driver inputs. However, adding a wider front tire will also make the steering feel slow and numb, which could be what you are feeling unless it was the mismatched tires. Either way, readers should know that going to non staggered wheels and tires will not make a car push that does not already push.
He means his tyres where crap. ****ty branded tyres and missed match.
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Old 02-26-2015, 06:10 PM
  #32  
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Originally Posted by Paulyy View Post
He means his tyres where crap. ****ty branded tyres and missed match.
gotcha
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Old 02-26-2015, 10:25 PM
  #33  
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I feel that in a track car with close to 50/50 weight distribution, there is no reason NOT to run a square setup. You need all of the front grip you can get in these cars. Then use spring rates/sway bar/damper settings to fine tune the balance to your preference and to the particular track/course. More front tire also helps braking. Plus you can rotate/flip/swap wheels and tires as needed at any corner.

I only run 16x8 phone dials with 225s all around on track, and plan to go to 17x9s with 255s all around at some point. A couple years ago I had to run my stock 16x7s in the front at a track event as one of the 16x8s was bent and the understeer was noticeable, had to band-aid the setup by adding rear sway bar rate, which is not great fix.

More rubber on the road is almost always better! It'll take trial and error to make it all fit without rubbing, but it is doable.
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Old 02-28-2015, 07:25 AM
  #34  
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Originally Posted by Droops83 View Post
1. I feel that in a track car with close to 50/50 weight distribution, there is no reason NOT to run a square setup.
So many people seem to think this and it's nonsense - particularly for a track car.

It would be more accurate to say that "If you are NOT prepared to modify your spring and bar rates, or spend money on optimum size rims and tire, then the EASIEST way to make these cars more neutral is to run a bigger tire on the front - which, if that HAPPENS to be the same size as your existing rear tire, then you will have a square setup." And for the budget conscious it makes it easy for tire rotation etc.

Possibly that does apply to the majority of people on this forum with road cars or only occasional track day use, but don't kid yourself. Even if you squeeze the biggest square tire setup you can onto your 944, say 295s all round on a wide body setup, you won't have as much grip level as you could achieve with a stagger and an even bigger rear tire, say 295/315, or 295/335 which there is room for on these cars with up to a 13 or 14 inch rear rim.

Set up properly, the car with the most rubber will have the most grip. Staggered or not. And set up properly a car with a stagger can be made just as neutral as a car with a square tire setup.

People talk about 'square tire setups' like they are some mythical holy grail of 944 handling. It's not the 'square tire setup' that is the hot ticket, it is the 'more tire setup'.
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Old 03-01-2015, 04:08 AM
  #35  
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Originally Posted by odb812 View Post
This doesn't make any sense. Wider front tires will make a car tend to oversteer more at the limit given the same driver inputs. However, adding a wider front tire will also make the steering feel slow and numb, which could be what you are feeling unless it was the mismatched tires. Either way, readers should know that going to non staggered wheels and tires will not make a car push that does not already push.
The PO was clearly open to economical solutions. The car had a cheap a$$ stereo, steering wheel, generic floor mats, and different (very old & hard) tyres on front and rear. I understand it makes no sense but that would be with decent tyres. As these tyres were well past use by date, the car pushed badly with the old tyres. I went back to staggered tyres with new Pilot sport 3's and car was transformed, and the understeer was gone. It became very neutral in handling. I totally blame the tyres and I guess my question to Pauly was more about how a good squared set up handled, not did it push like my old set up, as I haven't experienced a proper squared set up and was interested in his feed back. Sorry if you got the wrong impression from the way I phrased things.

Personally I went back to staggered because I much prefer how it looks on these cars, and also because thats how it left the factory, and I had no intention of messing with the suspension
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Old 03-01-2015, 06:43 AM
  #36  
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I'd not necessarily disagree with you Steve even though I'm one of the main proponents of a square setup. The caveat I'd add to your logic is that you can have too much tyre if you can't get heat into them. A 335 rear might be too much rubber for a lot of owners in my estimation. Might be wrong, but cold wider tyres should offer less grip than smaller warm ones. Squaring up the front may be a band aid, but I'd rather be running say 275 all round than 235/295 any day. Sure, tuning springs, sways, t-bars, bushes, bearings, bumpstops (last three sound like a shonky law firm) etc can equalise things and only goes to prove that there's more than one way to skin a cat.
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Old 03-01-2015, 08:45 AM
  #37  
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Originally Posted by 333pg333 View Post
I'd rather be running say 275 all round than 235/295 any day.
275 all around is more total tire than 235/295 so I agree..lol. Like I said 'more tire' is the winner. In this case that just happens to be a square setup.

Would you prefer 235 all round vs 235/295 assuming you could set both up properly? I wouldn't. Just because it's square doesn't make it better..which was my point - trying to get people to think about why bigger front tires (which happen to result in square setups) work better. It's not inherently because you have the same width tires front and rear...

If you went from 275s all round to 275/295 and assuming you set up both properly, you would still get an overall grip improvement, all else being equal.

So many factors relate to getting heat into tires other than their size. . Tire compound, track temp and surface type, weather, length of straights, number of corners, power output, braking capability, wheel weight etc...Of course not every car will suit running a 335 rear tire.Thus my caveat - "setup properly".

Just not "square is always better" and "there is no reason NOT to run a square setup"!!
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Old 03-02-2015, 02:24 PM
  #38  
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My preference for running square is only based on mine and other's positive experience. It's not the only way to fly. Usually I advocate it to people that have a medium to large stagger with small front tyres and often suffer from push understeer. Increasing the front contact patch is a no brainer in my books, but sure, if you can retain or increase the rear even further, then perhaps that can be better. Have seen and felt too much rubber and there is a limit to the more is betterer mantra.

I'd like to do back to back comparisons of the 275 all round vs 265 / 295.
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Old 03-02-2015, 03:38 PM
  #39  
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OK, so here's another question. Other than the basic rule of stuff as much tire under the fenders that you can... Is there a resource (I've looked and not found it yet) that might help determine optimal wheel width/tire size for a given setup? Unfortunately my budget does not allow for a lot of testing... That was one of the nice aspects of spec. 1 wheel tire combo available.
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Old 03-03-2015, 12:03 AM
  #40  
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Originally Posted by Dubai944 View Post
So many people seem to think this and it's nonsense - particularly for a track car.

It would be more accurate to say that "If you are NOT prepared to modify your spring and bar rates, or spend money on optimum size rims and tire, then the EASIEST way to make these cars more neutral is to run a bigger tire on the front - which, if that HAPPENS to be the same size as your existing rear tire, then you will have a square setup." And for the budget conscious it makes it easy for tire rotation etc.

Possibly that does apply to the majority of people on this forum with road cars or only occasional track day use, but don't kid yourself. Even if you squeeze the biggest square tire setup you can onto your 944, say 295s all round on a wide body setup, you won't have as much grip level as you could achieve with a stagger and an even bigger rear tire, say 295/315, or 295/335 which there is room for on these cars with up to a 13 or 14 inch rear rim.

Set up properly, the car with the most rubber will have the most grip. Staggered or not. And set up properly a car with a stagger can be made just as neutral as a car with a square tire setup.

People talk about 'square tire setups' like they are some mythical holy grail of 944 handling. It's not the 'square tire setup' that is the hot ticket, it is the 'more tire setup'.
I see your point, and it may be that the ultimate setup for a no-holds-barred wide body track machine with lots of aero like yours is to pack as much rubber in as possible. Slightly wider in the rear may be better for your setup, but not all of us have the budget for such a machine.

However, your point does not completely invalidate mine. A square setup may not be the "holy grail," but it makes a hell of a lot of sense for most people here who frequently track their stock-bodied street car. This is a 944 forum after all, and the vast majority of folks here are on a tight budget, myself included. A square setup makes a lot of sense in this case, as you do mention. Might some be better served by slightly wider rear wheels/tires? Maybe, depending on setup. The fact is, the factory front end geometry leaves a lot to be desired from a camber gain/caster standpoint. Lots of front tire goes a long way towards quelling understeer, band-aid or not.

Many of the wheel/tire upgrades that are installed on 944s, street or track, have too much stagger as they are often based on setups for rear- and mid-engine Porsches that DO require more rear tire to keep the rear end in check. 993TT/996TT wheel setups pair 225 front tires with 285s or 295s in the rear. It will certainly look cool on a 944, but is a recipe for understeer on track or in an autocross setting. Of course, a less staggered setup may be ideal (say 265-275 front and 285-295 rear, but it is difficult to find a matching set of rims in those sizes unless you go to high-dollar 3-piece wheels and mix and match rims/barrels, etc.

Therefore, the sensible approach is to run the same size wheels all around. This not only balances the handling (in many cases) but allows for swapping/rotating wheels and tires as necessary. I think a lot of people on this forum have played around a lot with spring and sway bar rates, no matter what their wheel/tire setup is; I certainly have! I have modified almost everything possible on the suspension of my '86 short of a replacement rear suspension member to replace the torsion bar tube. Even with a square setup, front end grip was a limiting factor on track until I modified my front spindles to correct the front roll center with my desired low ride height.

I am certainly not an engineer, merely a mechanic who has played around a lot with my 951's suspension setup over the years. But, some very smart and experienced engineers at GM were given free rein to create the ultimate street-legal track car based on the Camaro. I'm sure that you have heard of the recent Camaro Z/28. The engineers designed the entire setup of the car around a set of tires . . . . a square set of 305 Pirelli Trofeo Rs (though it must be said that the wheels are 11.0" front and 11.5" rear, likely to prevent squirm in the rear). The resulting car is capable of stupidly quick lap times for such a heavy pig (almost 3900lbs). It does have 53% of its weight over the front wheels, but then again so do many 944 race cars (most of the weight loss when stripped is from the rear, unless very light hood/fenders are used).

Again, not disagreeing with you, as you obviously have a lot of experience setting up your awesome-looking car, but I stand by my contention that a square setup makes sense for most of the rest of us!
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Old 03-03-2015, 12:19 AM
  #41  
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A square setup may not be the "holy grail," but it makes a hell of a lot of sense for most people here who frequently track their stock-bodied street car. This is a 944 forum after all, and the vast majority of folks here are on a tight budget, myself included.
This!
While I love both of my 951s, (and I love beating $200,000+ cars with the $20,000 one that's a race car) I don't have them because I just couldn't take the "Me too" stigma of owning a 991 turbo s and a Cup car.
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Old 03-03-2015, 12:50 AM
  #42  
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I'm also not advocating extremes. There is a point beyond which it will become increasingly more difficult to set up the car if the stagger is too big. In order to keep the car neutral there is a limit to how much you can soften up the front or stiffen up the rear to balance weight transfer on a car that has half its weight on the nose, before you run into other issues which reduce grip. I would never advocate running less front tire than you have room for on these cars. However I also don't see the point of stuffing a bigger tire on a non optimum rim like so many do just to say you have a square setup. With road tires you can go a bit wider than with race tires but you don't end up with a flat contact patch and often have too much sidewall squirm, both of which negate the advantage of the wider rubber to some extent. On those rims that Paulyy is using I used to run 225/640 slicks on the front 8.5 rims and 255/640 slicks on the rear 10 inch before the car was wide bodied. The car was absolutely neutral the way it was set up. Track also has a bit to do with it. I used to run spacers on the front with that combination to widen the front track as far as I could within the body limits.

My approach for the 944 is to pick the biggest wheel rim size that fits the front of the car without clearance problems when fitted with a tire size suited to the rim width (not necessarily the biggest tire you can fit on the rim) at an offset that maximises track first, or the biggest front size you can afford that fits properly. If you are on a budget and want to be able to rotate wheels it then makes sense to run the same at the rear, but to do it properly you really need the same rim widths and offsets as well, otherwise you can't rotate very well. If you have an excess of power,can afford it and are prepared to play with spring rates and adjust bars then you can consider taking advantage of the room in the rear to run a bigger tire - but it should match the rim you put back there as well.
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Old 03-03-2015, 12:51 AM
  #43  
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Originally Posted by LUCKY DAVE View Post
This!
While I love both of my 951s, (and I love beating $200,000+ cars with the $20,000 one that's a race car) I don't have them because I just couldn't take the "Me too" stigma of owning a 991 turbo s and a Cup car.
Hi Dave,

My sentiments exactly.

Not to change the subject too much, but I have noticed your mention of pretty stiff spring rates in several suspension threads. I am running 450F/650R, can't go much stiffer in a street car!

What size wheels and tires do you run, and what kind of lap times are you seeing at Willow Springs big track?

Thanks,
Chris
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Old 03-03-2015, 01:01 AM
  #44  
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Originally Posted by Dubai944 View Post
I'm also not advocating extremes. There is a point beyond which it will become increasingly more difficult to set up the car if the stagger is too big. In order to keep the car neutral there is a limit to how much you can soften up the front or stiffen up the rear to balance weight transfer on a car that has half its weight on the nose, before you run into other issues which reduce grip. I would never advocate running less front tire than you have room for on these cars. However I also don't see the point of stuffing a bigger tire on a non optimum rim like so many do just to say you have a square setup. With road tires you can go a bit wider than with race tires but you don't end up with a flat contact patch and often have too much sidewall squirm, both of which negate the advantage of the wider rubber to some extent. On those rims that Paulyy is using I used to run 225/640 slicks on the front 8.5 rims and 255/640 slicks on the rear 10 inch before the car was wide bodied. The car was absolutely neutral the way it was set up. Track also has a bit to do with it. I used to run spacers on the front with that combination to widen the front track as far as I could within the body limits.

My approach for the 944 is to pick the biggest wheel rim size that fits the front of the car without clearance problems when fitted with a tire size suited to the rim width (not necessarily the biggest tire you can fit on the rim) at an offset that maximises track first, or the biggest front size you can afford that fits properly. If you are on a budget and want to be able to rotate wheels it then makes sense to run the same at the rear, but to do it properly you really need the same rim widths and offsets as well, otherwise you can't rotate very well. If you have an excess of power,can afford it and are prepared to play with spring rates and adjust bars then you can consider taking advantage of the room in the rear to run a bigger tire - but it should match the rim you put back there as well.
I totally agree with not stuffing too much tire on a narrow rim, the squirm factor negates any gain in contact patch; I have driven students and customer cars thus equipped and felt it for myself. I was making a general point about square setups and failed to notice the extreme difference in the width of Pauly's wheels front to rear! Tire manufacturers will publish a recommended rim width for each given tire size. The general rule of thumb is to be in the middle of this.

In Pauly's case: too bad they don't make 245s for the front. Otherwise 235 front and 265 rear is what I'd do if restricted to those wheel and tire sizes, despite all of my rambling on about square setups: by square I mean equal wheel AND tire widths front and rear (OK, maybe a half-inch wider rim in the rear is good), and tire widths properly matched to the rim width!
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Old 03-03-2015, 01:54 AM
  #45  
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I acknowledge we are of course talking about fine points here and handling limits that most people don't need to consider.

At the end of the day not too many people driving their cars on here will be approaching the grip limits of their cars often enough and to the extent that it will make that much difference. As long as you are using sensibly sized and good quality tires and don't have clearance problems, go with what looks good... Paulyy's car certainly looks great and I am sure it will have more than enough grip for anything he wants to do with it!
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