cable snow chains in winter--Quattro--front or rear tires?

[B72011]

I found a pair of cable chains (low profile) at a garage sale the other day for $5 for the Avant.
Reason was there's a ski resort here in SOCAL--Mt. Baldy. The road is insanely steep and several years ago big pileups happened because fools were running regular tires on their AWD cars (Audi's, Subies, etc) and I dont want to be part of a pileup.
I am running Blizzacks in the winter due to out being in the mtns most wknds... Question is if I need to run chains on the Avant--do I run them front or rear. I would guess rear--or does it matter? My owners manual isnt very clear on the quattro.
Who has experience with this?

[old guy]

Interesting question! I did a little Googling and got conflicting information. According to a Jeep Rubicon website if you only have one set you should run them on the rear whereas the Subaru manufacturers website recommends the front. Here's my recommendation: I would run them on the front going up the mountain. This will give you better steering response. If at all possible switch them to the rear for the return trip down the mountain for for better stability from the increased drag from the rear wheels while going downhill.

[walky_talky20]

I would say front, because it's the front tires that do the stopping. Here's a good discussion on this:
http://www.rubicon-trail.com/jeep101/chains.html

On a B6 quattro, the center differential is a Torsen T1. This means it is a "symmetrical" diff and does not have a front or rear bias built in. More torque is directed to the axle with more traction. Due to the weight distribution of an A4, this usually means about 60/40 split (more torque to the FRONT axle). Of course this changes during heavy acceleration or climbing hills and such. But under most conditions, a quattro A4 is more front biased, so it makes more sense to put the chains on the front.

The only thing to be aware of when running chains on the front only (even on a FWD vehicle) is the rear end sliding out. You've added all kinds of "bite" to the front wheels, which is great for turning, acceleration, braking, but you rear end does not have the same bite. So for instance you can take a sharp corner at speed in the snow/ice and the front end will stick *nicely*, but the rear end won't. So you get some nice oversteer mid corner and the back can slide out on you. So then you try to save it by letting off the gas (wrong move, makes it worse) and hitting the brakes (even worse move, now you've spun). So you just have to be very conscious of your lack of traction out back so you don't overdrive the rear traction abilities. The most dangerous situation in my opinion is hill descent. You've got lots of weight on the front end, and those nice chains. This means LOADS of traction up front which makes for great braking. No weight on the rear axle and no chains, so the rear end *locks*. The ABS steps in to help of course, but that basically shuts down the braking. Switching the chains to the rear for the downhill section is probably a great idea. I would try it out both ways in a safe place if you get the chance, so you can see which way feels more secure and controllable.

[B72011]

Yeah I have been driving in the mtns for 20+ yrs all kinds of weather. My Dodge 2500 Turbo Diesel used to be my weapon of choice, but we're going to sell it fairly soon.
I'll do a bit more research.
Thx for the info........
Z

I would say front, because it's the front tires that do the stopping. Here's a good discussion on this:
http://www.rubicon-trail.com/jeep101/chains.html

On a B6 quattro, the center differential is a Torsen T1. This means it is a "symmetrical" diff and does not have a front or rear bias built in. More torque is directed to the axle with more traction. Due to the weight distribution of an A4, this usually means about 60/40 split (more torque to the FRONT axle). Of course this changes during heavy acceleration or climbing hills and such. But under most conditions, a quattro A4 is more front biased, so it makes more sense to put the chains on the front.

The only thing to be aware of when running chains on the front only (even on a FWD vehicle) is the rear end sliding out. You've added all kinds of "bite" to the front wheels, which is great for turning, acceleration, braking, but you rear end does not have the same bite. So for instance you can take a sharp corner at speed in the snow/ice and the front end will stick *nicely*, but the rear end won't. So you get some nice oversteer mid corner and the back can slide out on you. So then you try to save it by letting off the gas (wrong move, makes it worse) and hitting the brakes (even worse move, now you've spun). So you just have to be very conscious of your lack of traction out back so you don't overdrive the rear traction abilities. The most dangerous situation in my opinion is hill descent. You've got lots of weight on the front end, and those nice chains. This means LOADS of traction up front which makes for great braking. No weight on the rear axle and no chains, so the rear end *locks*. The ABS steps in to help of course, but that basically shuts down the braking. Switching the chains to the rear for the downhill section is probably a great idea. I would try it out both ways in a safe place if you get the chance, so you can see which way feels more secure and controllable.

[CHARLES A4]

I would say front only because I was always told an awd drives like a front wheel drive

[walky_talky20]

I would say front only because I was always told an awd drives like a front wheel drive

Really depends on the type of AWD. For example, the original Mercedes-Benz "4Matic" is *completely* Rear Wheel Drive until slip occurs.

www.awdwiki.com

[freeloader700]

I spoke to a few Audi stealerships and they said you need to run them front and back if you are going to run them because its symmetrical AWD. Adding chains creates more surface area to make full rotation and will no longer be even with the other tires. Thats what they told me and I am not sure it would harm all that much but it does bring some concern

But if anything, I would say front x2, pulling you seems to be better than pushing you in those conditions

[incubusfc]

Try to look on Craigslist for another set.


Or drive slow w them on the front.

[audinaut]

Running or not running chains on B6 Quattro's has always been clear as mud. With the whole "do not run 4/32nds wheel differential" thing we've all heard, how does that fit in with running chains where link size must not "protrude no more than 1/2 inch" per what the owner manual states?

On the question of whether to run chains on the front or back. My 2002 owners manual states the front. Why? Dunno.



Also, the following is from the Bentley, also implies that chains be run on the front. Why? Dunno.

Audi > A4, S4 (B6, B7) > 2002-2008
Wheels and Tires Guide
44 - General Information.Emergency Wheels, General Information

• It is not permissible to use snow chains on the emergency wheel for technical reasons.
• If vehicle must be driven with snow chains, therefore the emergency wheel must be installed on the rear axle for a breakdown on the front axle. The rear wheel freed up must then be mounted in place of the faulty front wheel.

(Emergency wheel would refer to those skinny temporary wheels, which did not come from the factory. Full-size spares came from the factory.)

For me, there's a lot of good common sense reasoning in some of the thread replies to run chains on the front or the rear. But Audi says the fronts. Why? Dunno.

Now on whether to even be running chains.......

If you're comfortable running chains where they may cause the "4/32nd wheel differential" situation..........are the chain links smaller than what a cable chain layout would be? Does the chain wrap around onto the inside sidewall?

I'd test fit them first with the chains on and with your wheels on the ground. Visually check the clearance between the tire and the upper pinch bolt area where your upper control arms meet, and your brake calipers. Then think/imagine what the chain does when it rotates at speed -- centrifugal force will cause any slack the chain has on the wheel to expand outward. Previous comments and second-hand stories have always said chains/cables get hung up in the suspension, causing them to then wrap up the brake calipers. I test fitted some cables on 235/45-17 on my 2002 sport suspension, and did not feel comfortable that the cables would not get caught up in the suspension -- the available clearance was miniscule. The cables I fit were a low profile cable setup euro-rated for tight wheel to suspension clearances. Running a narrower tire may help mitigate any clearance issue the wider tires gave me.

If suspension clearance is a potential concern, alternative to chains or cables are AutoSock, Thule K-Summit Low-Profile Passenger Car Snow Chain, or Spike-Spiders.

[Docwyte]

If you have snow tires you don't need to run chains. I've never run chains and I drive up to Vail on the weekends. The drive to Mt Baldy is nothing, I used to do it in my fwd GTI on summer performance tires.

[audinaut]

Another alternative chain/cable option. Pretty much identical to the Thule K-Summit Snow Chain. Might only be available in Europe -----> Weissenfels Clack & Go Quattro Snow Chain

Too late for you right now, but FWIW traction devices are always cheaper outside the fall/winter season. Thule K-Summit Snow Chain's do go on sale for around $300 ------> CamelCamelCamel Amazon Price Tracker

[Charles.waite]

The whole 4/32nds thing really only applies side to side on the same axle.

Also the chains would be run for maybe a few miles at slow speeds so honestly ignore all those warnings. They don't really apply to someone who knows what they're doing. For the average moron though yea they probably shouldn't be driving in those conditions in the first place...

My voters put them on the front. Turning/braking is more important and the front wheels do the majority of both. Downhill I think the rears makes more sense as it'll stabilize the car. In the end, if you drive carefully, you'd probably be fine in snow tires...

[audinaut]

The whole 4/32nds thing really only applies side to side on the same axle.

In all my years on the boards, that is the first time I've seen a comment that it applies to the same axle </files that one away into the brain bucket>

[Charles.waite]

In all my years on the boards, that is the first time I've seen a comment that it applies to the same axle </files that one away into the brain bucket>

Well it applies all around, but the really tight tolerance is mainly from side to side so that that front and rear diffs don't wear out prematurely from different sized tires causing it to rotate incorrectly. The center diff is generally designed to distribute torque so its not too likely it'll have many adverse effects from the different rolling radii.

Granted, its generally not a great idea to run staggered setups with quattro because any undue wear on the diff isn't a good idea, but some people do it and I've never heard of a center diff blowing up.

[walky_talky20]

Well it applies all around, but the really tight tolerance is mainly from side to side so that that front and rear diffs don't wear out prematurely from different sized tires causing it to rotate incorrectly. The center diff is generally designed to distribute torque so its not too likely it'll have many adverse effects from the different rolling radii.

Granted, its generally not a great idea to run staggered setups with quattro because any undue wear on the diff isn't a good idea, but some people do it and I've never heard of a center diff blowing up.

Knowing the operation of the center differential, I would argue the opposite. The front and rear open differentials would make up for the diameter difference across the axle with relatively low friction bevel (spider) gears. However, the Torsen T1 center differential makes up for speed differences *between* the axles using multiple high friction worm gear/wheel pairs. The amount of heat created (and thus, wear) would be greater in the torsen differential.

[Charles.waite]

Knowing the operation of the center differential, I would argue the opposite. The front and rear open differentials would make up for the diameter difference across the axle with relatively low friction bevel (spider) gears. However, the Torsen T1 center differential makes up for speed differences *between* the axles using multiple high friction worm gear/wheel pairs. The amount of heat created (and thus, wear) would be much greater in the torsen differential.

Really? I was under the impression the front/rear diffs tended to be the weakest links?

[walky_talky20]

Depends on what you are talking about. Which blows up first with 600HP drag strip launches? This discussion here is which one takes more wear when dealing with wheels of different diameters.

Either way, the point is moot. The chains are really only needed on the mountain - low speed, low traction. The diff will hardly take any significant load when the surface is slick. As long as you aren't spinning the tires excessively or using them for highway cruising, the diameter difference is nothing to worry about in this case.

[B72011]

Sure, that road when there is WET snow and its always wet given where the mtn is in relation to the ocean--means there's a brutal layer of ice on it. Going up is not so much an issue---its coming down later in the day. Its so steep, your car just want to slide.
I was there several years ago after a 4 foot storm and there was literally a 15 car smash up as cars just slid and slid into one another. I want to try and avoid that. The chains are just a bit of insurance in addition to the blizzacks I usually am running.
I'll go with the front if necessary.

If you have snow tires you don't need to run chains. I've never run chains and I drive up to Vail on the weekends. The drive to Mt Baldy is nothing, I used to do it in my fwd GTI on summer performance tires.

[old guy]

Reread post #2. I am sticking with my recommendation. If I were in your shoes that is what I would do. Front going up. Rear going down. If you don't think you will be able to change them out then I would go with the rear. You are much more likely to have problems going downhill than uphill.

Cheers!

[ThirdAudi]

Just ran my 2013 S4 with cable chains on the front over Continental ultra high performance summer tires. The car sounded like a Cessna but smoothed out at 40-55mph. Great traction, did notice a bit of slide in the rear but it was controllable.

[B72011]

What size tires do you have? S4 I am assuming 250 30 18" or something?

What specific brand were they? I'll get the same.

I know people run the cables as I have seen FWD Audi's up in the mtns of SoCal.

[ThirdAudi]

255/35 19" Continental ContiSportContact 3 came on the car new.

I've had 3 other A4's and an A6 with either all season Michellin Pilot Sport A/S Plus, Pirelli P Zero Nero, and Yokohama AVID. The best performance I've found for my style of driving (usually pushing the limits in all weather situations) and on perfect dry summer roads has been the Pirelli PZero Nero but I'm sad to see they don't make it in my new tire size.

I have now been in Idaho and Washington for the past week driving every day in snow and ice conditions, temperature hovering between 27-32 degrees F and I have to say driving on these 3 season tires is a bit scary. If you are like me and plan on doing lots of winter driving, I would stick with 4 season tires. I plan on replacing mine with either Michelins or Bridgestones when the time comes.

I would rather stick to using chains only when required.

What size tires do you have? S4 I am assuming 250 30 18" or something?

What specific brand were they? I'll get the same.

I know people run the cables as I have seen FWD Audi's up in the mtns of SoCal.

[silverfox.mike]

The manual for my 2007 Audi Q7 Quattro 3.0TDi states that chains should only be used when the car is fitted with 18" rims and using a tyre size of 215/60/R18. It also states that the chains should be fitted to the rear wheels only.

I assume that this is because there is insufficient clearance to the suspension at the front - but then if that was the case, my summer wheels/tyres are 235/45/R20 that makes the summer tyre 20mm wider which is much wider than the snow chains.

Previously I've had Volvo XC90s and they run the same [winter] tyres as the Audi of 215/60/R18 - chains on that vehicle are fitted to the front. However I believe the Volvo XC90 is biased to mostly Front Wheel Drive until rear drive is needed whereas the Audi Q7 is a full time 4WD vehicle.

My preference would be to run them on the front since that is where the steering is and therefore much traction is needed, so I would like to know if anyone has run a Q7 with chains on the front.

Also I'm intrigued by reports that say when going down the mountain, having them on the rear makes a lot of sense. However I'm not against getting another set and running with all 4 wheels chained up if that is recommended from a wheel geometry point of view.

[fR3ZNO]

so I would like to know if anyone has run a Q7 with chains on the front.

Holy necrobump, also this is the B6 A4 section... I would go with what the owner's manual says