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Old 03-16-2005, 08:13 PM   #1
zacek
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Default Staggered Wheels/Tires really BAD idea

WOW! not sure if this has been covered before but staggered combos besides being just logically bad for AWD cars is specially BAD on the STi's. The Active Differential will actually sense a tire's height (circumference would be more accurate) down to 0.5 inch and will start adjusting the compensate for the slower or faster spining tire. This just causes NASTY noises from the differential specially duing coasting (decelerating) conditions.

I had 235/40 on FRONT and 245/40 on REAR with the purpose of giving the rear tires a beefier look. Well, the looks part looked awesome but the DCCC did not like it at all. I would also get vibrations during normal driving at random times. I initially thought I had a bad balancing issue, then I went for the stiffer Hochtkis Bars, then finally used the stock front wheels to see if the vibration would go away leaving the big aftermarket in the rears. This obviously amplified the effent in height diferences of the tires and completely threw the differential off to the point of getting a strong vibrations while over 40mph and eventually a CE light. I then installed all 4 stock wheels and all strange noises and vibrations went away. So if you must use a staggered setup make sure the tire heights match because any difference greater than .25" will be picked up by the Active Differential.

Just wanted to share this!
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Old 03-16-2005, 08:26 PM   #2
ripvw
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No AWD should run tires that differ in circumference by more than 1/4" - active differential or not. Subaru makes this clear in every owner's manual of every AWD car they've ever made

some on this board have run/are running wider wheels up front, narrower wheels in back for better handling, i.e. 17x8 front/17x7.5 rear - same size tires front and rear. this combination will reduce understeer by providing more grip up front.

your approach - even if it had worked - would have added additional grip in the rear and thus more understeer - something the STI does not need
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Old 03-16-2005, 10:35 PM   #3
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WE already knew this....You SHOULD have.
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Old 03-16-2005, 11:24 PM   #4
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How lame is it to run narrower rear tires though.. performance or not, just looks ghey.
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Old 03-16-2005, 11:33 PM   #5
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.....WAY TOO many people worry WAY too much about 'looks' these days......and what they think other people think....about them....by what they have, and drive, and wear and.............................
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Old 03-17-2005, 12:01 AM   #6
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No offense, but I'm really suprised you did something like this especially considering the time you've been a member and your posting status. Hope nothing was permanently damaged.
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Old 03-17-2005, 01:04 AM   #7
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You've been on this forum long enough to know that is a horrible idea. I hope your warranty gets denied when your car breaks and you come back here to whine about it.
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Old 03-17-2005, 03:18 AM   #8
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wow! cut that negative chatter people, gees! Nothing is wrong with my car luckily. I just thought I should share this because I bet there are a lot of people out there probably thinking around similar lines. I knew that staggered combos are not good for our cars but I did not know how sensitive it was. As far as criticizing me for my status and lenght as a forum member is non-sense, my specialty are electronics and handcrafting and not wheel /differential oriented.
The difference in tire diameter between a 245/40 and a 235/40 tires is less than half inch. I just never thought the DCCC controller would pick on that.
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Old 03-17-2005, 09:38 AM   #9
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noob gets pwned.

Next time... try the search function before making such silly choices in tire sizes.
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Old 03-17-2005, 10:22 AM   #10
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Quote:
I knew that staggered combos are not good for our cars but I did not know how sensitive it was. As far as criticizing me for my status and lenght as a forum member is non-sense, my specialty are electronics and handcrafting and not wheel /differential oriented.
I respectfully disagree. You deserve all the "negative chatter," and should get more.

Though I know far more about wheels/tires, brakes and suspension than electronics, I also knew enough when adding a UTEC to consult a local expert for tuning. A man's got to know his limitations.

...and as you said, you even knew staggered tire diameters are not good for subies. I'm not just posting to flame you, but perhaps if some other "specialty" n00b reads this thread then perhaps, maybe, they might think twice before trying something really dumb--especially something that can be easily researched.
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Old 03-17-2005, 11:01 AM   #11
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Quote:
Originally Posted by ripvw
No AWD Subaru should run tires that differ in circumference by more than 1/4" - active differential or not. Subaru makes this clear in every owner's manual of every AWD car they've ever made
Fixed. There are AWD non-Subarus that run F/R tires of different circumference. Porsche and Lamborghini, just to name two.

Quote:
Originally Posted by zacek
The difference in tire diameter between a 245/40 and a 235/40 tires is less than half inch. I just never thought the DCCC controller would pick on that.
As ripvw said, the tolerance listed in the owners manual is a quarter inch. This goes for the STi and standard WRX, Legacy, etc. Basically, by doing what you did the center diff is constantly working to get the front and rear axles spinning at the same rate. It's a lot like towing the car with the front wheels off the ground, only less visible.

Neil.
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Old 03-17-2005, 11:04 AM   #12
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Quote:
Originally Posted by zacek
As far as criticizing me for my status and lenght as a forum member is non-sense, my specialty are electronics and handcrafting and not wheel /differential oriented.
The difference in tire diameter between a 245/40 and a 235/40 tires is less than half inch. I just never thought the DCCC controller would pick on that.
I mentioned your status because it reflects how active you are on this site. With the amount of info regarding this issue, I was just suprised that you went with the set-up that you did. I didn't intend to offend you zacek and I'm sorry if I did. .....anyhow, I'm glad your car is o.k. and everything worked out in the end.

- Kean
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Old 03-17-2005, 03:14 PM   #13
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I told you it would give you problems! Just wasn't sure exactly how the car would react long term. I guess its good to know what sort of things to look for. Thankfully, so far, it does not look like permanent damage.

So how long did it take before thing started acting up? I'm just thinking about this in terms of using the spare tire. How many miles can one expect to use the spare before one might get Zacek's symptops?
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Old 03-17-2005, 03:22 PM   #14
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.....IMO, the spare should be a LAST RESORT and used as little and at as slow a speed as is at all possible to get the vehicle(and yourself) out of harms way....and that's it.
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Old 03-17-2005, 05:04 PM   #15
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I agree, however I've been stuck in the middle of the F'en desert with a flat, no cell reception, with easily 75-100 miles in either direction before there was any signs of life.
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Old 03-17-2005, 05:13 PM   #16
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I think the spares are supposed to be used for about 50 miles. That probably assumes you are keeping the car around 50Mph.
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Old 03-17-2005, 06:21 PM   #17
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and shouldnt the spare only be on the rear? or was it only on the front? cuz of the diff or something? can someone confirm...
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Old 03-17-2005, 08:28 PM   #18
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well, from my recent experience, keeping speeds below 50 mph and turning the DCCC (for those who have it) all the way back to the rears if the donut is on front or the torque to the fronts is the donut is on the rear will help out.
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Old 03-17-2005, 08:34 PM   #19
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i remember it had something to do with limited slip in front or rear. and wrx's dont have dccd. bah it should be in teh manual anyway....
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Old 03-18-2005, 01:00 AM   #20
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Now, if you had open diffs int he front and rear, you could have gotten away with 240's on the right and 235's on the left...
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Old 03-18-2005, 10:40 AM   #21
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Quote:
Originally Posted by zacek
well, from my recent experience, keeping speeds below 50 mph and turning the DCCC (for those who have it) all the way back to the rears if the donut is on front or the torque to the fronts is the donut is on the rear will help out.
The DCCD only has a range of 35F/65R to 50/50. There is no full front or full rear setting.

It's been my belief that the issue with the spare is less because it's a single tire that is having to be dealt with, as opposed to both front or both rear. My thinking was that this allows the front differential (or rear, depending on where the spare is) to take some of the load away from the center diff. The front and rear differentials are designed to operate much more frequently (turning), so they aren't as adversely affected as the center is when you've got tires of different heights front to back.

Now, I don't believe the regular WRX has a front diff (it's open?) so I don't know how this affects what I've said. And, I'm by no means an expert on this.

Neil.
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Old 03-18-2005, 02:20 PM   #22
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Quote:
Originally Posted by NTP WRX
Now, I don't believe the regular WRX has a front diff (it's open?)
yes, open front diff on WRX makes it the place to put a spare - assuming that you haven't upgraded your front brakes so it no longer fits...

there's a couple of threads running around here regarding the spare for those looking for more info on that topic
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Old 03-19-2005, 01:42 AM   #23
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man, now you guys have me all paranoid. i had to replace the rear driver's side tire after the stocker had a slow leak in the side. it looked like it was cut with a blade, but not that deep... anyways, i had a new tire put on the other day. so i've got one new tire, and three moderately worn tires. after reading this thread and checking my manual, it seems like i've got trouble. i plan to get the other three tires on, i considered taking my time, but now i think the sooner the better. but i can feel the car is different. at freeway speeds, the car feels like i'm driving it on a windy day, and i have to counter-steer the car a little bit from side to side.
BUT ITS NOT CONSTANT. maybe about 10-15% of freeway driving is when i notice this, and at speeds of over 65mph. well, i'm getting new tires tomorrow, and if things are still a little freaky on the highway, probably an alignment too...
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Old 03-19-2005, 01:12 PM   #24
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Ok guys, since this seem to be the hot topic i want to set something stright, u can put a larger wheel on the back than in the front, IF u make sure that the overall diameter is within the 1/4" or less difference. Example i have 18 all the way around right now with 225/40/18 on, im looking to put 19s on the back and after doing some research found that 235/35/19 are really close to the diameter and its in the 1/4" difference. Also as u could see i listed the 19" as a wider tire and was wondering if that tire would clear the strut. remember its the same heighth as the 18.
Thanks Guys
Tanner
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Old 03-19-2005, 02:56 PM   #25
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Quote:
Originally Posted by WolfInSheepsCLothing
man, now you guys have me all paranoid. i had to replace the rear driver's side tire after the stocker had a slow leak in the side. it looked like it was cut with a blade, but not that deep... anyways, i had a new tire put on the other day. so i've got one new tire, and three moderately worn tires. after reading this thread and checking my manual, it seems like i've got trouble. i plan to get the other three tires on, i considered taking my time, but now i think the sooner the better. but i can feel the car is different. at freeway speeds, the car feels like i'm driving it on a windy day, and i have to counter-steer the car a little bit from side to side.
BUT ITS NOT CONSTANT. maybe about 10-15% of freeway driving is when i notice this, and at speeds of over 65mph. well, i'm getting new tires tomorrow, and if things are still a little freaky on the highway, probably an alignment too...

Put the new tire on the right front.....
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