Unstable on Slippery Roads

[whitetiger]

ive seen that. I must be thinking of the VLSD in the rear then. I know its very easy to overwhelm that diff. Ive done it many times.

[Underdog]

Direct from the vaca pix.

[HAMMER DOWN]

Well I will now put in my 2 cents. With real world driving. The 1st 73k on my 05 GT w/ 5MT & 2 winter. Now I swap in 05 STi 6MT w/ center DCCD & front LSD. 13k, 1 winter, the 6MT is by far way better then the 5MT in rain, mud & snow when you'll pushing it.

 

Now some thing I wrote in another thread that was closed. On open vs LSD.

 

Quote:

Originally Posted by Vimy101 http://legacygt.com/forums/skynetim/buttons/viewpost.gif

Unless there is unequal traction between the fronts, the open diff will apply power to both wheels.

 

Yes & no, if it was, you'll should be able to do a two wheel burn out with a open diff. with equal traction. But you can't. If I remember right . If your car as enough power to smoke tires with a open diff. It will smoke the ring gear side tire first. And when I was at the drag strip. With My GT, w/ 5MT. I always spon the drivers side front tire at launch & chirp the same tire in 2nd & 3rd. A open diff doesn't truly put power to both wheels with equal traction. When push to the extreme it will favor the ring gear side.

 

 

Quote:

If conditions are very slippery, having a front wheel that has not exceeded the available surface friction is a good thing when it comes to steering input.

If that was the true, all rally car's would have open diffs in the front. So they can get though the corners better , right. I think not.

 

Back to your quote on steering input. If your have one wheel not exceeding & the other exceeding [spinning]available traction. All the power is going to the spinning wheel, but we all know the open diff powers the wheel with the least traction. That why vehicle with open diff get stuck a lot easier the vehicle with LSD.

 

But once you break one of your tires free w/ a open diff. you'll lose drive out of a corner & corner speed. Plus it easier to break one tire free, then two. So throttle input is more importain w/ an open diff. But with a day to day driver. It all comes down to driver's preference.

 

An a old racing statement, "Good driver with a lesser vehicle will beet a poor driver with a better vehicle everytime".

 

So people get to know your vehicle, open or LSD, really don't matter. If you'll never exceed your & your vehicles ability.

 

Mike

[Vimy101]

Well I will now put in my 2 cents. With real world driving. The 1st 73k on my 05 GT w/ 5MT & 2 winter. Now I swap in 05 STi 6MT w/ center DCCD & front LSD. 13k, 1 winter, the 6MT is by far way better then the 5MT in rain, mud & snow when you'll pushing it.

 

Now some thing I wrote in another thread that was closed. On open vs LSD.

 

Quote:

Originally Posted by Vimy101 http://legacygt.com/forums/skynetim/buttons/viewpost.gif

Unless there is unequal traction between the fronts, the open diff will apply power to both wheels.

 

Yes & no, if it was, you'll should be able to do a two wheel burn out with a open diff. with equal traction. But you can't. If I remember right . If your car as enough power to smoke tires with a open diff. It will smoke the ring gear side tire first.

And when I was at the drag strip. With My GT, w/ 5MT. I always spon the drivers side front tire at launch & chirp the same tire in 2nd & 3rd. A open diff doesn't truly put power to both wheels with equal traction. When push to the extreme it will favor the ring gear side.

 

I believe it but you're talking large amounts of power on a high friction surface. I mentioned in a previous post that an LSD would be cool to have in that type of situation.

 

 

Quote:

If conditions are very slippery, having a front wheel that has not exceeded the available surface friction is a good thing when it comes to steering input.

If that was the true, all rally car's would have open diffs in the front. So they can get though the corners better , right. I think not.

 

Rally guys are experts and driving with tires that are optimized for conditons (e.g. thin large lug snows for snow, etc.) As unclemat reiterated, grip is where it's at. Even an open diff with great a great tire set up will provide lots of grip/purchase. Additionally, I refer to general not performance motoring in very slippery snow conditions - such as we have seen a lot in these parts this year - where not a lot of torque or power being used because are speeds low.

 

Back to your quote on steering input. If your have one wheel not exceeding & the other exceeding [spinning]available traction. All the power is going to the spinning wheel, but we all know the open diff powers the wheel with the least traction. That why vehicle with open diff get stuck a lot easier the vehicle with LSD.

 

Open diff vehicles can get stuck very easily. Believe me, after driving RWD open diff cars in harsh winters for many years, I know that all too well. However, the open diff won't slide you into the ditch either. FWD open diff, on the other hand, at least allows one to "point" the power so that is an advantage over RWD open diff (OD).

 

Maximum traction occurs before the co-efficient of friction is overcome. For "general" motoring, this is a failsafe (and also what enables great drifting and easy trips to the donut store ). Say you're stopped at an intersection preparing to make a right turn. The conditons are snowy with a compacted base layer. You apply power, get into the turn, the inner wheel (usually) exceeds the coefient of friction and spins, the outside wheel does not. This means that the primary steering tire (outside left in this case) is maintaining maximum possilbe steering control. Oversteer in this case. This is a good thing because understeer created by both fronts breaking the COF takes you into oncoming traffic or the ditch if things are sliipery enough so that the front LSD doesn't "feel" enough relative shear to maintain the max COF for steering purposes.

 

But once you break one of your tires free w/ a open diff. you'll lose drive out of a corner & corner speed. Plus it easier to break one tire free, then two. So throttle input is more importain w/ an open diff. But with a day to day driver. It all comes down to driver's preference.

You're talking max track performance and I agree completely with that and also with the dd preference things.

An a old racing statement, "Good driver with a lesser vehicle will beet a poor driver with a better vehicle everytime".

 

So people get to know your vehicle, open or LSD, really don't matter. If you'll never exceed your & your vehicles ability.

 

Mike

 

The engineers, accountants and lawyers sit around all day sending memos to each other about this stuff. The accountants have final say.

[SBT]

Captainmorgan:

 

It feels as if I am in a boat on the water. The care does great on the snow but when it becomes hard packed and icy it seems to sway. For instance: last night driving home going under an overpass I felt the rear end of the car start to slide. I know driving on ice is no good with any vehicle but it did not seem to track as well as a FWD car.

 

Since this is a 2.5i wagon, a lot of this sway is, IMHO, due to the fact that you have open differentials front and rear, which would cause one side or the other to spin, slip and then take up, which would tend to rock the car. Put dedicated snow tires on this, and 90% of this will likely go away.

 

I'm trusting that you're not going to run the worn-out tires for much longer and are planning to get dedicated snow tires. That's asking for trouble. But whichever tire you use, make sure that you check your tire pressues. Minimum 35F/33R and keep the 2 PSI bias unless you're towing, then bump up the rears to 2 PSI above the fronts, i.e., 35F/37R.

 

With Subaru's AWD system, TPs greatly affect the handling and can cause sway, if you're unbalanced side-to-side on each axle. That's because TPs affect circumferential difference (CD) and CDs can/do cause one wheel to turn faster or slower than the opposite wheel on the same axle. That's also why you never replace just one tire, or one axle, always replace all four.

 

Edit: Reread the whole post again - ignore the open diff comment as it now appears that you have an Outback which has a rear LSD.

HTH,

SBT

[Vimy101]

^ One could pull the fuse for the 2.5i AWD system putting it into FWD mode, correct?

[SBT]

^ One could pull the fuse for the 2.5i AWD system putting it into FWD mode, correct?

 

I've done this before and it makes for a very skerrwy wide. And not too much fun, traction-wise.

SBT

[ebpda9]

i think it all has to do with the rear suspension. the front is great on my 2.5i, but it seems that the rear unloads the suspension to easy. i am experiencing all the above even with dedicated snow tires. Maybe it has something to do with the rear suspension geometry ?

[k2flipside]

nevermind the obviuos about the tires being possibly worn out. some subaru models have an option that allows its owners to tune their suspension electronically to the type of driving they want to do (sort of like the electronically controlled hydrolic suspension on a BMW X5, so as the car turns on a sharp curve, the suspension automatically tightens for better handing.

[TimGinCentralNJ]

ive seen that. I must be thinking of the VLSD in the rear then. I know its very easy to overwhelm that diff. Ive done it many times.

 

Well, if you think about it, most production LSDs (regardless of manufacturer) are setup with only 25% lock-up--this means when brand-new, they're only designed for transferring up to 25% of the power from a wheel which is slipping to the wheel which has grip. Many commercially available racing LSDs are setup with 40% lock-up, but again (for aforementioned reasons)--this is probably way too much for the daily driver under most circumstances.

 

Not sure of the "on-road" usefullness, but I seem to recall Toyota or someone actually has or had a factory rear LSD which could be turned into a full locker (100%) by way of a switch if both rear wheels were spinning. Not THAT is the best of both worlds

 

Tim

[TimGinCentralNJ]

nevermind the obviuos about the tires being possibly worn out. some subaru models have an option that allows its owners to tune their suspension electronically to the type of driving they want to do (sort of like the electronically controlled hydrolic suspension on a BMW X5, so as the car turns on a sharp curve, the suspension automatically tightens for better handing.

 

 

Out of curiousity, what model Subaru is that? Tribeca is the only one I can think of which might have this, but I've not heard for sure.

 

Not a new technology by any means, but I know BMW used to call this "EDC" (Elec. Controlled Damping). One of the coolest application of this I know of this is in the Acura MDX; the shocks are filled with a liquid containing metallic particles which can be positively charged causing the shock to stiffen up or loosen up depending on the road conditions and/or driver's selection. Wouldn't want to have to replace one of those....

 

Tim

[ehsnils]

Out of curiousity, what model Subaru is that? Tribeca is the only one I can think of which might have this, but I've not heard for sure.

 

I think that the SVX had that, and the old XT (as in my Avatar) had air suspension , but not adjustable dampers .

 

The problem with an advanced suspension is that it's yet another thing that can go wrong. And it's expensive. And there is always a risk of someone messing up the setup causing a vehicle that's dangerous to drive.

 

But I really liked the air suspension.

 

At least - I know that the STI has an adjustable center differential, that can be either set to Auto or manually all the way to full lock.

 

But it would have been interesting to test a Subaru with a full set of Torsen differentials. But that would probably mess up any possible support that a VDC system could provide.

[SBT]

Out of curiousity, what model Subaru is that? Tribeca is the only one I can think of which might have this, but I've not heard for sure.....Tim

 

Subaru has used air suspension/load leveling, but it wasn't tunable in the sense that you could control individual corners. The 91 XT AWD 2.7 H6 Turbo Coupe comes to mind. Other than possibly a AWD DL or GL of that era, I don't believe Subaru (at least in the USA) has offered such a system.

SBT

[DukeTrout]

ive seen that. I must be thinking of the VLSD in the rear then. I know its very easy to overwhelm that diff. Ive done it many times.

 

I've done both, up on the mountain in winter with the OBXT. I was turning right onto a very empty, cold highway and really gave it the go pedal. Rear end swung nicely wide under control, then gave up the ghost and just slid. Luckily, the center diff sent a big chunk of power up front to compensate, and the front grabbed and I shot forward in the correct line, with the rear end coming back in line with some oscillation. It was quite fun. The only problem was, when I overwhelmed the rear diff, all kinds of warning lights lit up and I ended up with the cruise light and error code showing for about 50 miles. Then they went back to normal.

[TCSKIBIKE]

This thread has gone crazy, the guy is driving in the winter with all season tires, bad ones at that. All season tires should be outlawed! They dont work and they make people think they are good to go in the winter. I was recently rear end by a girl with all season tires on snowy roads!!

 

If you drive in winter conditions you need winter tires.

[Voytech]

This thread has gone crazy, the guy is driving in the winter with all season tires, bad ones at that. All season tires should be outlawed! They dont work and they make people think they are good to go in the winter. I was recently rear end by a girl with all season tires on snowy roads!!

 

If you drive in winter conditions you need winter tires.

Agreed.

 

Want to buy me a set of snows for the three times there was snow on the roads this winter?

[taz]

I hate these stock tires they put on these cars. Anything firestone/bridgestone you can bet on having bad traction and wear. Get rid of those and pick up something with some good tread!

[Guest]

Agreed.

 

Want to buy me a set of snows for the three times there was snow on the roads this winter?

 

For millionth time. It's not just snow it's also, or perhaps mainly about low temperatures. That's why there is distinction between snow-biased tires from winter-tires.

[Voytech]

For millionth time. It's not just snow it's also, or perhaps mainly about low temperatures. That's why there is distinction between snow-biased tires from winter-tires.

Oh I know that. But from what I understand, all seasons do not suddenly loose traction the moment it goes below a certain temperature. So it's feasible to say that even in the lower temps I've seen here (10ºF-20ºF) the grip of my advan's is still ample for daily driving.

 

I'm not at all questioning the advantages of having dedicated snow/winter tires. It's just that I cannot justify the cost for a few days of snow.

 

/dead horse

[Guest]

Oh I know that. But from what I understand, all seasons do not suddenly loose traction the moment it goes below a certain temperature. So it's feasible to say that even in the lower temps I've seen here (10ºF-20ºF) the grip of my advan's is still ample for daily driving.

 

I'm not at all questioning the advantages of having dedicated snow/winter tires. It's just that I cannot justify the cost for a few days of snow.

 

/dead horse

 

Fair enough. The best way to justify winter tires is to buy summer tires

[dujie]

Okay then! I had no idea that my original question would initiate all of these responses. This is all good information from what I can understand. I went the most logical and cost effective approach and purchased a set of new Toyo tires. Toyo Versado LX.

[Voytech]

Let us know how much difference the new tires make!

[dujie]

I will follow up with ya'll.

[ehsnils]

Agreed.

 

Want to buy me a set of snows for the three times there was snow on the roads this winter?

 

Notice that the winter tires also are a lot better on black ice, which is a much bigger problem than snow on most roads. So if you have freezing temperatures you will need winter tires.

 

The really interesting thing is that when it gets really cold the benefits of winter tires decreases again - mostly because the all season tires will get better grip again, but also because the rubber in the winter tires gets harder. Its really when it's around the freezing point that you will benefit the most from winter tires. Wet ice is the worst winter surface that you can have!

[robinlsb]

Notice that the winter tires also are a lot better on black ice, which is a much bigger problem than snow on most roads. So if you have freezing temperatures you will need winter tires.

 

The really interesting thing is that when it gets really cold the benefits of winter tires decreases again - mostly because the all season tires will get better grip again, but also because the rubber in the winter tires gets harder. Its really when it's around the freezing point that you will benefit the most from winter tires. Wet ice is the worst winter surface that you can have!

 

Ummmmmm, I think not. In comparison the winter tire will be MORE flexible than the AS tire.