Tire Size and AWD [Merged 5-7] diameter radius rolling different sizes size
Newbie ForumBeginner/newbie/general DSM questions. first mods, how to run 10's when you haven't run 12's yet, any tech question that doesn't fit in another tech forum. New Members must limit their tech posts to this forum and sub-forums.
hey guys heres the deal....im runnin stock gsx 17 rim with stock good year tires. i was planning on buying rims and tires this summer to replace them because i want wider tires and am tired of bending rims. Anywayz i got a nail in my tire and they found another so they said it couldn't be fixed. under road hazard they are helpin me pay for one so i went ahead and bought the other so i would have two new tires. My question is am i hurting my car at all by runnin 2 new tires in the front or back and then the two old ones? i read somewhere that the VC may not like that.. thanks guys
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errr I dunno dude, I know Left and Right Size tires will break shit. But I dont know how much a diffrence is alowed in the front and rear. now I know theres give in the VC. like 2-4 Mph or something. I dont think same size new fronts, and Same size old tires in the rear will make a diffrence. I mean The tred on tires isnt that tall, The main size of the tires is the Sidewall height.
thanks for the reply i was hoping that was the case....i really dont wanna buy 4 new tires if i plan on upgrading in the summer but id rather do that than hurt the car ..thanks alot for your answer tho you have made me feel a lil better about doin it
2/32??? whoa...i just picked up my car and it seems to be that the rear (new tires) have about 50% more tread than the old (front now) tires. so your saying ill mess things up..my question is will i be okay to drive it back to school (70 miles) away tomorrow than let it sit till ig et new tires or will i blow something up on the way?
got that right, AWD vehicles need to have tires almost exactly the same tread depth, or the transfer case will be screwed.......i work in a tire shop so take my word for it.......we will not put 2 new tires on an AWD vehicle becuase of it, the customer either has a choice for us not to do any work, or put 4 new on........liability reasons, if u do any new, DO 4 NEW
I had the same problem just about two weeks ago...I came back from Iraq to find that my front left tire had a "slow" leak....well I went to breakfest and on my way driving back it felt real sluggish. Pulled into the next gas station and the tire was coming of the rim. Kinda sucked....long story short. ABout 95% of tire shops will tell you if you have a AWD car that they are required to change all four. Makes sense....
I will agree on that, you should not have a difference between 1/8th of the tread. Although I have changed a lot of tires 2 fronts, 2 backs. there was not that much difference in the tread. I have done that on my GSX for about 3 years.
Just because I have done it does not make it right. I have heard the same story that you need to change all 4. This is coming from techs that are good friends.
So take it for what you will, but I don't want to be the casue of someone blowing out their transfercase.
Has anyone seen anything in either an owners manual or the shop manuals?
Would there be any benefit to having wider tires in the rear than up front on an AWD? This assumes that the overall diameter of the front and rear tires is the exact same, only the rears are wider than the front? I know some of the exotic AWD cars have wider tires out back then up front, jsut wondering if it helps with anything like handling or something.
Now the overall diameter would be the same so that all the wheels spin at the same rate... other than when turning and such.
ok, i understand the mid engine and more weight to the back, just was not sure if it would help any, maybe on launching the car since the weight shifts to the rear, youd have more tire...not that its needed with AWD unless making a lot of power, or if it would help turning in anyway.
Originally posted by 14.5 drift Mc-G is right. The exotics are ussually mid engine cars and more weight is placed on the rear, hence the wider rear tires.
Please name an AWD car that is not either front- or rear-engine. I'm just trying to figure out how you get power to both the front and rear if the engine is in the middle. I know how they do it on a pick-up truck (although this is front-engine, the system would still work if it were mid-engine, because of the height); but I have no idea how they would do it on a car. Thanks.
Bugatti Veyron is the first one that comes to mind. Also the AWD lamborghinis are mid engine. one shaft goes forward and one goes to the back. which could mean they may have diff ratios so that may make it easier to have wider in the rear
Originally posted by jtmcinder Please name an AWD car that is not either front- or rear-engine. I'm just trying to figure out how you get power to both the front and rear if the engine is in the middle. I know how they do it on a pick-up truck (although this is front-engine, the system would still work if it were mid-engine, because of the height); but I have no idea how they would do it on a car. Thanks.
- Jtoby
porche makes an all wheel drive mid engine vehicle. I'm not sure what your asking but I dont think it would be a 50/50 split. Would probly favor the rear wheels in order to prevent over steer unlike my car, lol.
Originally posted by 14.5 drift porche makes an all wheel drive mid engine vehicle.
Really? I was under the impression that the AWD Porsches were all rear-engine. Unless you mean that silly SUV; who cares about that! I know that the AWD 911 is rear-engine, not mid-.
The two exotics cited by Eagle 5 are real, AWD mid-engines. I had never heard of either one and say thanks for the pointer. Normally I avoid thinking about things that I'll never be able to drive, but in this case it was interesting.
Missed the Group B rally cars as well - most of those were mid-engined AWD. One of the Ford variants had front engine with rear transmission (a la 944) and shafts running all over the place...
theres two for ya. BTW what is the difference between the rear or mid engined cars? If you'll notice they both have the same wieght distributions so the drive trains would likely be setup the same, no?
theres two for ya. BTW what is the difference between the rear or mid engined cars? If you'll notice they both have the same wieght distributions so the drive trains would likely be setup the same, no?
mid engine means the engine sits behind the passenger compartment but in front of the rear axles. rear engine means the engine site behind the rear axles.
mid engine cars can probably do the diff size because they would have one shaft going to teh front and one to the rear and coule probaly have diff ratios so larger tires in the rear would be needed. but thats only a guess
The centre diff can be geared any way the engineer wants it to be, and similarly the wheels/tyres can be different ODs, which produces a similar effect, that of altering the static torque distribution.
The limitation with DSMs is purely the use of a Viscous Coupling. If the VC is required to constantly rotate differentially it will overheat and die, so with a 50/50 geared centre diff the tyre ODs must be the same to avoid this. However, if the centre diff internal gearing was changed, one could fit larger OD tyres to one end (the output shaft with the slower rotational speed) and that would neutralise the gearing difference, and the VC would be happy again. Or simply get rid of the VC and employ a different slip limiting mechanism.
Originally posted by ACM The centre diff can be geared any way the engineer wants it to be, and similarly the wheels/tyres can be different ODs, which produces a similar effect, that of altering the static torque distribution.
The limitation with DSMs is purely the use of a Viscous Coupling. If the VC is required to constantly rotate differentially it will overheat and die, so with a 50/50 geared centre diff the tyre ODs must be the same to avoid this. However, if the centre diff internal gearing was changed, one could fit larger OD tyres to one end (the output shaft with the slower rotational speed) and that would neutralise the gearing difference, and the VC would be happy again. Or simply get rid of the VC and employ a different slip limiting mechanism.
Charles
I figured this is is the reason why you have to have same size tires, however, what if you have a clutch type slip or say the quiafe? With the clutch would it simply burn out the clutches much quicker? or say with the quiafe, would it just cause the car to "jump" or jerk occasionally?
It would jump and jerk all the time. A regular LSD in the center diff would try to stop the wheels from turning at different speeds and it would lock up. So it would be like driving a car with a welded center diff and different size wheels.
Like the guy up there ^ said, you have to change the gearing inside the diff to match the different size tires.
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Hey Eagle, decided to make my first post on here aimed at a fellow Natian. I can't recall where I read it, but on awd DSMS (1gs at least) power distribtuion is 70/30 rear/front. I find that believable too as my talon tends to have a more rwd handling bias. You may be able to get away with different sizes, but I honestly have yet to see a dsm to try it and would make things more expensive anyway, as you wouldn't be able to rotate your tires at all. Just some food for though
Originally posted by DSM4DSM Hey Eagle, decided to make my first post on here aimed at a fellow Natian. I can't recall where I read it, but on awd DSMS (1gs at least) power distribtuion is 70/30 rear/front.
Originally posted by DSM4DSM Hey Eagle, decided to make my first post on here aimed at a fellow Natian. I can't recall where I read it, but on awd DSMS (1gs at least) power distribtuion is 70/30 rear/front. I find that believable too as my talon tends to have a more rwd handling bias. You may be able to get away with different sizes, but I honestly have yet to see a dsm to try it and would make things more expensive anyway, as you wouldn't be able to rotate your tires at all. Just some food for though
Hey, I think I have seen your name on the local board.
Would it be possible to change the gearing in the differential? Or would that be way too much work or cost too much for something that would not be very beneficial? Seems like if you were hardcore or something it could help out. Maybe make a 40/60 or 30/70 power split, throw a little wider tires in back, maybe like 215 up front and 235 or 245 in there rear and it could help with the understeer.
Of course, I dont know and changing the gearing would probably be quite hard or just cost a lot... but hey, its only an idea.
Regardless of the engine location you need to keep the rolling diameter of the tires all the same. If you're good with numbers and can figure out the right width to go without changing the diameter then you'll be ok. If you put taller tires on one end and smaller tires on the other you will destroy the transfer case and viscous coupler. Not to mention you will then lose the 50/50 split by simply putting different tires on.
Refer to your owners manual for tire replacement requirements.
Doug
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2 new tires bad for awd?
