Just want to clear up some things about staggered

[trackTSIawd]

I've been searching around on here and looking up threads about staggered rims. A while back I posted a thread asking to see staggered wheels on a 1g awd. Every single thread on here I read as soon as staggered comes about someone says NOT FOR AWD IT'LL WRECK YOUR DRIVETRAIN. First, staggered refers to width and offset not height. If you were to run an 18 and a 19 on an awd obviously it would take less rotations of the axle to turn the 19 the same distance as the 18 and the drivetrain wouldn't know what to do with itself. Anyways, if the wheel height and profile of the tires are the same there won't be a problem with a two inch difference in width. Audi quattros can have staggered wheels, gallardos and murcielagos come stock with staggered wheels, porsche awds can have staggered wheels, hell theres a guy with a mk2 gti around me with a synchro drivetrain and he runs staggered wheels. Most cars aren't a 50/50 distribution of power anyways. Then there is the comment about the rear getting more traction than the front and that will wreck your drivetrain.. it doesn't already? do you think when you launch your awd and all the weight transfers to the back that the front is getting the same amount of traction? no. I suppose you could also make an argument that there would be more drag and rotating mass in the back, so if you want to make this argument, go out in your car and partially engage your e-brake... I'm pretty sure the only thing you will come back home to is some hot rotors. I'm not trying to be a dick about this but it just irritates me that people are probably not putting staggered wheels on their cars because of the posts of some people that probably haven't researched the topic at all ... which is pretty apparent considering the first post is usually about the height of the wheel. feel free to correct me if I'm wrong and it's just that all the cars I named above have super drivetrains specially designed for staggered wheels.

 

[mavisky]

The only thing that matters in the end is overall tire diameter. Some EVO autox'ers actually run 275's up front and 245's in the rear to get the car to rotate. They've apparently found a combination that gives them near identical outer diameters while having different widths.

Im looking into a setup like this, although mine will probably be 275's all around, but with 10's in teh front and 9's in the rear. Of course being a fwd, I could run 175/13's and not care

 

[Defiant]

The crucial dimension is the radius from the hub to the roadway. Are all tires going to grow the same amount with rotation? Will they have the same grip? A "no" to either -which is just about inevitable with non-identical tires- will have the VCs fighting the drivetrain even more than they usually do. The amount to which this may or may not cause damage will be determined after failure.
No other vehicle I've been able to discover uses the DSM scheme of full-time, 50/50 torque split controlled by viscous couplers. Audi/VW/Lamborghini, Subaru, Honda and others (who has Ford/Jaguar stolen theirs from?) are two-wheel drive cars which throw in AWD when they feel like it. They don't compare to DSMs. Whether they're "better" or not is subjective.

 

[trackTSIawd]

Escort cosworth, subaru impreza, and legacy use viscous couplers. That's just what I know off the top of my head. So what you are saying is that because the rear tire would have more width it would be able to stretch out in the profile more than the front. But with an extra inch I really cant see that causing a huge difference in diameter. http://forums.vwvortex.com/zerothread?id=2965946 Go look at the side view of the rear wheels on that jetta. If you notice they generally use the same tires on both front and back and stretch them which would make it impossible for them to be any different when accelerating.

 

[Dorifto]

Escort cosworth, subaru impreza, and legacy use viscous couplers. That's just what I know off the top of my head. So what you are saying is that because the rear tire would have more width it would be able to stretch out in the profile more than the front. But with an extra inch I really cant see that causing a huge difference in diameter. http://forums.vwvortex.com/zerothread?id=2965946 Go look at the side view of the rear wheels on that jetta. If you notice they generally use the same tires on both front and back and stretch them which would make it impossible for them to be any different when accelerating.

That right there is called "tire tuning".

It is known that a stretched tire will not "give" under load, making it more resistant to manipulation by road and vehicle forces acting upon it, and as a result it is much more responsive, but loses grip much more easily. Hence, why many drift cars use a stretched tire in the rear.

A bulged tire will have too much give and sidewall flex, as a result you see decreased response but trade that for increased grip [lateral loads are placed on the sidewall versus the contact patch, allowing grip to be sustained].

A "squared" tire is considered ideal for neutral handling characteristics, from the standpoint that an equal amount of grip and slip is desired [also assuming individual vehicle characteristics are null and void, meaning the test chassis doesn't suffer from either over- or under-steer.].

Do keep in mind, diameter does not change concerning sidewall stretch or bulge. It DOES change, however, concerning centrifugal force - watch a drag slick on a Pro-Mod 'rail, they stand up in a quick hurry in the burnout stage, and down the track.

The main thing to consider is tire height or tire diameter [the terms are interchangeable]. DSMs commonly have about a 24.5" tire height from the factory [assuming 16" wheels and factory-spec tire dimensions]. While keeping as close to 24.5" as possible will keep the speedometer accurate, the number can fluctuate so long as all 4 tires are the same height. Case in point, check out TireRack.com's specs on the Sumitomo HTR Z tire in the following link:

http://www.tirerack.com/tires/Spec....145WR7HTRZ&tirePageLocQty=&partnum=145WR7HTRZ

Look at what tires have corresponding tire diameters. For argument's sake, we'll say we're going with 17" wheels, in a staggered offset and width [8" front, 9.5" rear]. The two tires that have identical diameters in this particular size are the 245/45 ZR17 and 275/40 ZR17. Should we desire to go all widebody-Supra style with a DSM, we could go as far as to stuff 315/35 ZR17s under the ass-end, and still have an appropriate tire diameter/height.

*Note - also compare the Revs Per Mile rating with tire height/diameter - too-large a differentiation in revs per mile is what kills VCs, half-shafts, rings and pinions, etc. etc., and should be kept to a reasonable low in cars like ours. This is where the often-argued point of mismatched tire sizes [and by generalization, tire width] took off with destroying drivetrain parts. The deviation should be kept within 10 revs per mile to avoid damage, as a rule of thumb. An argument here is that the VC is required to slip much more than 10rpm when cornering sharply - I am very positive it can take the abuse.

I've got two setups in mind for my car's wheel-and-tire selections:

1- 17x7" wheels, with as close to a +35 offset as possible, at all 4 corners; 225/45ZR17 Sumitomo HTR Zs up front, and 205/50ZR17 HTR Zs out back. Yes, I realize there is a difference of near a quarter-inch in tire height [24.9" vs. 25.1"], but this is an autocross setup with intentional oversteer characteristics. Very rarely will I see a straight line in excess of 50mph with this setup. To me, this is an acceptable sacrifice with my vehicle, others may choose otherwise with their individual setups and vehicles.

2- 17x8" wheel, 245/45ZR17 HTR Z [F]; 17x9" wheel, 255/45ZR17 HTR Z [R]. To most, the 8 rpm difference between front to rear is almost unacceptable - as I said above in the note, an acceptable maximum is +/- 10rpm from most standpoints. This selection is aimed for spirited high-speed driving in a straight line. Again, an acceptable sacrifice for my car, and my settings.

Now, given all this awesome info backing up staggered wheels, there is one anomaly which cannot be escaped - weight. Rotational mass will ALWAYS be greater with a wider wheel, given matching diameter, brand, model, and construction. Simply put, there is MORE wheel to throw around the hub. Also of noteworthiness is weight differentiation between same-spec wheels of different brands. If you've got money to throw around for grins and giggles, you can purchase custom wheels of different brands/sizes that have IDENTICAL weights with deviations of less than a gram. But of course, most of us are not so lucky.

Can you tell I'm an advocate for staggered wheels on AWD whips?

 

[trackTSIawd]

Thats exactly what I needed... another person that likes staggered wheels with some facts. I have no idea why people don't like that looks of staggered wheels.

 

[Dorifto]

I personally think it's less the liking of a staggered look, and more being afraid of consequences that are avoidable with research and thought. In the case of FWD cars [I'm a big Honda sellout, I'll be honest here ], many people immediately denounce wider REAR tires, claiming there is no benefit. Sure, a performance benefit doesn't exist in most cases, but if aesthetics is where you're working, why not? Of course, a viable option in that respect would be using same diameter and width wheels, with different offsets to give the appearance of wider rears without having the wider contact patch.

I'm a big fan of track-width though, and any increase in such nets cornering stability. Can't ever have enough of that.

I suppose its' being open to sacrifice and change in the quest for your look. Nothing tweaks me more than seeing a nice Mustang GT with 8" wide wheels front to back ... those cars NEED a stagger to look good with stock bodywork.

 

[Defiant]

Escort cosworth, subaru impreza, and legacy use viscous couplers. That's just what I know off the top of my head.

But do they split the torque distribution 50/50 like a DSM does?

 

[trackTSIawd]

Hm, thats a good question. One would have to assume yes though because since there aren't any electronics in our cars.. and since fluid cant really be electronically controled to move and mimic centrifugal force acting on it, how would it be able to differ power from 2 of the wheels at will? I'll have to research this.

 

[Dorifto]

The Cosworth has a rear-biased AWD system, 40/60 or 35/65 I believe is the split.

With the DCCD in STi WRXs, it varies, but when being automatically controlled tends to stay 40/60. As for standard Imprezas and Legacys, I can't say, I believe they're as simple as 50/50. A Legacy understeers like it's 50/50, that's for damn sure.

 

[goodbye]

VC's don't magically blow up because you have a low tire or are running front tires with more tread than the rears as reading the Talon Digest back in the day would have you believe. I've had 60+ AWD DSM's with varying conditions of tires and even some with mis-matched tire sizes and I've yet to have one problem with a VC in all that time.

I've been toying with the idea of staggered rims on my hooptie since around '99, just never got around to it. I've looked it over from every angle though, if your rolling diameter is close, it shouldn't be any problem.

And I don't have my tech manual at home here, but as memory serves, I believe the torque split is 45/55. Don't quote me on that though. [We won't. You're wrong. It's 50/50.]

 

[mavisky]

I've personally watched a VC lock up in less than 20 miles by running two brand new tires on the rear and two tires with 2/32nd's tread depth on the front. VC ran fine for years, he went and bought two new tires for winter (roads still dry though) and within 20 miles the vc had locked up and the car had to be flatbedded home. Swapped in a new vc, bought new front tires as well. Car works perfect to this day.

 

[Defiant]

Hm, thats a good question. One would have to assume yes though because since there aren't any electronics in our cars.. and since fluid cant really be electronically controlled to move and mimic centrifugal force acting on it, how would it be able to differ power from 2 of the wheels at will? I'll have to research this.

Viscous couplers don't work by centrifugal force, but by the nature of the silicone oil they're filled with. How It Works has a very good article about them.