I'm no mechanical wizard so please go easy on me if this is a real stupid question but how does ABS have any effect on tires breaking loose due to hydroplaning?
BTW gang, I still don't have my two replacements yet
2 new tires......mount on front or rear?
- Thread starter mikep
- Start date
- Status
BTW gang, I still don't have my two replacements yet
- Joined
- Jun 2, 2003
- Messages
- 23,591
All manuals I have seen have stated that the tires with the deepest tread should always be mounted on the front. That makes sense to me, since during emergency breaking and abrupt maneuvering,due to intertia and centrifugal forces, most "weight" will rest on the front tires. Most cars, at least all FWD and permanent AWD cars are made to understeer, so losing grip in the rear is not very likely. Even with my A4 quattro with a weight ratio of about 55/45, oversteer isn't that easy to achieve. That's not an endorsement for bald tires on the rear, because a blow-out in the rear can be lethal. Two years ago I had a rear tire disintegrate while going 75 on the Freeway. I never even felt it. The only indication that something was wrong was a droning noise and teh scared face sof other drivers.
By the time I pulled over, which was about 30 seconds after I heard the noise first, the tire was in shreds around the rim, the rim was very hot to the touch. I found a small screwdriver inside the tire. I think every Audi quattro should have tire monitors, because the car won't even slightly pull when a tire falls apart. I remember losing tire pressure on my VW Scirocco many years ago when going very fast. That was really scary, with the car pulling and almost breaking out.
PS: Note to all Audi quattro drivers: make sure your front and rear tires do not differ more than 3% in circumdifference, or you may do damage to the torsen differential.
PS: Note to all Audi quattro drivers: make sure your front and rear tires do not differ more than 3% in circumdifference, or you may do damage to the torsen differential.
The reason is that the rears would then hydroplane first. This leads to a car with EXTREME oversteer propensities while in this condition. It does not matter how much understeer bias is dialed into the car, if you completely lose traction in the rear, while reataining traction in the front, you have a car on the knife's edge of a spin. I've had this happen, and it is a real nail biter. If it had happened in a turn, there is no way I could have recovered.
With video;
http://www.michelinman.com/care/buy_how.html
Other faqs
http://www.goodyeartires.com/faqs/Care.html#9
http://www.discounttire.com/dtc/brochure/info/newTiresRear.jsp
[ July 14, 2004, 09:49 AM: Message edited by: VaderSS ]
As a result of posting this question here and the many responses...some saying mount in rear while othres saying mount in front, I did my due diligence on the subject. What I found is VaderSS and those who said "mount in rear" are correct (for precisely the reasons VaderSS stated).
Having said that, in my situation I think it is splitting hairs as the tires have less than 1000 miles on them. True, they have seen some hard track use and have worn more than they normally would in those few miles but overall they are still "new" tires.
Having said that, in my situation I think it is splitting hairs as the tires have less than 1000 miles on them. True, they have seen some hard track use and have worn more than they normally would in those few miles but overall they are still "new" tires.
- Joined
- Jun 2, 2003
- Messages
- 23,591
Someone please imform Audi, VW, Porsche, Mercedes, BMW, and their dealerships that their recommendation of mounting the tires with the deepest tread on the front is incorrect and outright a liability. As we all know, it never rains in Germany and they don't ever drive over 55 in rain and sleat there. Those guys need to get a clue!
I honestly don't know why anyone would reccomend that the new tires be placed up front. For some reason, my Impala wears it's back tires out faster than the front... Because I had not kept up with the rotation, the rears had 1/32" less tread than the fronts, and when I hit some standing water on the highway, the rear hydroplaned while the fronts did not.
The car fishtailed back and forth for about 3 seconds until the rears touch down. The car was ready to spin with the slightest over-correction. If I had been in a turn, the car would have instantly spun and been out of control.
Had the tires been reversed, it is likely the tires would not have hydroplaned at all, since there is more weight on the front end, and even if they had, the car simply would have understeered until traction was regained. Had I been in a turn, that means I may have left the road, but at least the car would have been pointed in the right direction to regain control when traction was regained rather than sideways or backward.
The car fishtailed back and forth for about 3 seconds until the rears touch down. The car was ready to spin with the slightest over-correction. If I had been in a turn, the car would have instantly spun and been out of control.
Had the tires been reversed, it is likely the tires would not have hydroplaned at all, since there is more weight on the front end, and even if they had, the car simply would have understeered until traction was regained. Had I been in a turn, that means I may have left the road, but at least the car would have been pointed in the right direction to regain control when traction was regained rather than sideways or backward.
- Joined
- Jun 2, 2003
- Messages
- 23,591
Well, I was unaware that we were talking about two almost BALD tiresand two new tires on the same car! I fugured we weere talking about maybe 1/3 to half worn tires and new tires. 1/32" isn't safe to drive with anyway. With 1/16" tread depth left it's high time to get new tires. The wear indicators on most tires are at 1/16, and that (1/16" = 1.6 mm) is incidentally the legal wear limit in some countries.
If you hydroplane, you're simply going to fast. If you have the tires with less tread on the front, the front will possibly float first, but you won't be able to steer and your only option of slowing down will be coasting.
Actually, while having less tread will make the car hydroplane at much lower speeds, whether the car hydroplanes first in the front or rear depends also on the weight ratio (front/rear) of the car, rather than on tread depth per se. With a decent amout of tread on ALL tires left, and without standing water on the road, I have never encountered hydroplaning at under 50 mph.
If you hydroplane, you're simply going to fast. If you have the tires with less tread on the front, the front will possibly float first, but you won't be able to steer and your only option of slowing down will be coasting.
Actually, while having less tread will make the car hydroplane at much lower speeds, whether the car hydroplanes first in the front or rear depends also on the weight ratio (front/rear) of the car, rather than on tread depth per se. With a decent amout of tread on ALL tires left, and without standing water on the road, I have never encountered hydroplaning at under 50 mph.
quote:
Originally posted by moribundman:
As we all know, it never rains in Germany and they don't ever drive over 55 in rain and sleat there. Those guys need to get a clue!
I don't know about Audi, Mercedes, BMW, et all....I only know what Firestone/Bridgestone, Michelin, TireRack and Car and Driver say is the proper place to mount the newer tires.
Read my post again... The rear tires had 1/32" less tread than the fronts. Actual tread depth was 4/32" and 5/32". Yes, I was traveling too fast when I hit the standing water. That happens... Should the car go to an extreme oversteer condition when it happens?
- Joined
- Jun 2, 2003
- Messages
- 23,591
Sorry, Vader, yes, I was reading that too fast.
First of all, a 1/32" difference in tread depth between front and rear seems negligible to me, unless very little tread is all that's left.
When your car begins to hydroplane, the only way to let the tires grip is to let the car slow down. The car will normally not start over or understeering by itself, unless you attempt to steer while the car is hydroplaning.
I'm sure weight distribution of the car matters. What's the ratio for your Impala?
I asked Gary at the Tirerack and this is what he said:
"Easier to control understeer than oversteer for most... this is why rear is recommended. Also on a wet skid pad in testing, the vehicle with new tires on the rear and worn on front could go faster while maintaining control than the car with worn tires on rear and new on front.
Keep in mind if this is a quatto car this might be a moot point as Audi says all tires need to be within 4/32nds of each other."
Maybe I once again over-estimated common sense in most drivers. ;-) In all my years of driving, I've encountered hydroplaning only at high speeds on straight stretches of road, never in curves. My concluison is that anyone should try their car out on a test track anyway. I know I'll try with more tread on the rear than fornt next time I get around to it. Maybe I'll even change my evil ways, if I like what I find.
We have high crowned roads here in Texas. Start a full blown hydroplane and the car will start moving to the side. Loose it in just the rear and the back starts sliding to the side, which has to be compensated for by turning the wheel toward the side. Make any attempt too keep the car from moving in this condition and you just spun the car. Just making the correction starts a pendulum effect. Only happened once, but it was enough to make a believer out of me.
Weight distribution for the Impala is around 55/45.
Keep in mind that AWD vehicles need there tires to be close to matching for center differential issues. Same goes for my Impala which has an LSD. Spare is slightly bigger than the normal tires and WILL cause increased wear of the differential if mounted on the back. Nice huh?
Weight distribution for the Impala is around 55/45.
Keep in mind that AWD vehicles need there tires to be close to matching for center differential issues. Same goes for my Impala which has an LSD. Spare is slightly bigger than the normal tires and WILL cause increased wear of the differential if mounted on the back. Nice huh?
- Joined
- Jun 2, 2003
- Messages
- 23,591
How on earth do you start hydroplaning on a crowned road? Are you sure the tires weren't just slipping? To me, hydroplaning is when the tires begin floating on the water. Just losing grip isn't necessarily hydroplaning, so maybe we aren't talking about the same thing?
Your Impala seems to have almost the same weight ratio like my Audi quattro. I know I can throw my quattro into oversteer on a dry road, so I suppose it might happen more easily on a wet road, although it's never happened to me. However, I see oversteer as a seperate issue from hydroplaning. Of course, oversteer will make hydroplaning even worse.
Another thing I'm thinking: if I go fast on a wet road with maybe 1/2" of water or so on it, the front tires plow through the water, pushing it to the side, meaning the rear tires will go over less water than the front tires. Hydroplaning should occur first in the front. Whenever I can feel hydroplaning, it seems to announce itself in the steering wheel first, meaning front tires.
Your Impala seems to have almost the same weight ratio like my Audi quattro. I know I can throw my quattro into oversteer on a dry road, so I suppose it might happen more easily on a wet road, although it's never happened to me. However, I see oversteer as a seperate issue from hydroplaning. Of course, oversteer will make hydroplaning even worse.
Another thing I'm thinking: if I go fast on a wet road with maybe 1/2" of water or so on it, the front tires plow through the water, pushing it to the side, meaning the rear tires will go over less water than the front tires. Hydroplaning should occur first in the front. Whenever I can feel hydroplaning, it seems to announce itself in the steering wheel first, meaning front tires.
Transition light rain to very heavy rain in an instant and you get hydroplane conditions, even on crowned roads. Have water crossing the road from ditch overflow and same thing. When I say hydroplane, I mean just that, tire lifted off the ground on a wedge of water.
My car's handling balance is as follows; mild oversteer in turn in, milder understeer in static cornering, neutral with light to medium throttle or braking and very controllable oversteer under heavy braking or throttle. Basically, it's set up to be an enjoyable autocross car.
On the night in question I experienced the back end starting to drift off to the right after a transition to standing water due to heavy rain with no extra throttle, braking, or steering input. The usual attendent "roar" of being in deep water was there and the feeling was exactly like times when I had purposely hydroplaned the car except that only the rear was doing it. I dropped speed by several mph and full control was reestablished. During the time it was in this condition, it was mildly fishtailing and slowly drifting to the right. It's cliche', but it felt like a minute or more passing.
I've seen inch deep water flowing across the the middle of a turn. At night that would be hard to see. It's likely that a full blown hydroplane would run the car off the road and cause a wreck, but hitting something head on is always preferable to hitting it sideways. I do not believe that a hydroplane induced oversteer, even momentary, in a corner would be recoverable by the average driver.
My car's handling balance is as follows; mild oversteer in turn in, milder understeer in static cornering, neutral with light to medium throttle or braking and very controllable oversteer under heavy braking or throttle. Basically, it's set up to be an enjoyable autocross car.
On the night in question I experienced the back end starting to drift off to the right after a transition to standing water due to heavy rain with no extra throttle, braking, or steering input. The usual attendent "roar" of being in deep water was there and the feeling was exactly like times when I had purposely hydroplaned the car except that only the rear was doing it. I dropped speed by several mph and full control was reestablished. During the time it was in this condition, it was mildly fishtailing and slowly drifting to the right. It's cliche', but it felt like a minute or more passing.
I've seen inch deep water flowing across the the middle of a turn. At night that would be hard to see. It's likely that a full blown hydroplane would run the car off the road and cause a wreck, but hitting something head on is always preferable to hitting it sideways. I do not believe that a hydroplane induced oversteer, even momentary, in a corner would be recoverable by the average driver.
- Joined
- Jun 2, 2003
- Messages
- 23,591
I'll second that opinion.
I can tell you that especially with a quattro I have to be very careful, because the extraordinary grip the system provides is so tempting and enables you to go faster than most, but loss of control will come very sudden and with very little warning. I can't claim to have encountered hydroplaning on roads other than Autobahn or high speed highways. I'm not counting the effects of hitting small patch of standing water on the road.
Best to avoid hydroplaning altogether is of course adequate speed depending on driving conditions, which is someting we all know.
Still, I want to see what Audi's offical stance is on the tire issue. I may contact them and ask them why their manual is in conflict with what seems to be reommended by many now.
I made the mistake of owning a FWD car once in the mid-80's for a couple of years. Other than that (until this last year) it was nearly always V8 American cars these past thirty-plus years. I have had more than my share of premature rear brake lock and fishtail in 4500-6200 lbs of all-American steel cars.
Still, I've nearly always -- when replacing tires in pairs -- have put the new ones on the front.
At high speeds the thought of losing steering control outweighs my fear of another wild-asss fishtailing. Not to mention a blow-out at speed.
Really, there is no one answer as there are simply too many variables. Granny going to church and grocery? Poor boy in pickemup commuting 30-miles each way on Interstate? Live in rainy climate or dry? Snow or never? Etc.
Still, I've nearly always -- when replacing tires in pairs -- have put the new ones on the front.
At high speeds the thought of losing steering control outweighs my fear of another wild-asss fishtailing. Not to mention a blow-out at speed.
Really, there is no one answer as there are simply too many variables. Granny going to church and grocery? Poor boy in pickemup commuting 30-miles each way on Interstate? Live in rainy climate or dry? Snow or never? Etc.
- Joined
- Jun 2, 2003
- Messages
- 23,591
The quattro AWD system distributes power via a torque sensing differential to the front and rear wheels. Usually, the front wheels receive most of the power. If wheel slip occurs, the slipping wheel gets less power, and more grippier tires receive more power. This is a purely mechanical system. At low speeds, the quattro utilizes in edition EDL (electronic differential lockup) to ensure traction and the ABS system to prevent wheel spin. The system works so well, that unexperienced Audi drivers find themselves more often in the ditch than anyone else, because though you can go incredibly fast on the worst roads, you still can't overcome the laws of physics. In Montana, cops used to call bad weather "Audi-Duty Time."
- Joined
- Jun 2, 2003
- Messages
- 23,591
I haven't gotten around to contacting Audi regarding this issue, but I asked a guy who works for VW in Germany. Here is what he said regarding the issue:
The front tires displace most of the water, so the rear tires will encounter less water, hence more tread on the front tires gives more grip, BUT only as long as the driver maintains a SAFE SPEED. Unskilled drivers or those who can't gauge their own and their car's limits, are advised to mount the tires with more tread on the rear.
The German ADAC conducted tests on wet and dry road and concluded that a below average or average driver was advised to mount the tires with more tread on the rear, as loss of control announced itself less drastically. That goes for cars with all drive systems, including AWD.
The advantage of having the tires with more tread on the front are superior grip, better handling and steering response, and better braking.
The consensus seems to be that skilled drivers can enjoy better tire performance with the more grippy tires on the front.
The front tires displace most of the water, so the rear tires will encounter less water, hence more tread on the front tires gives more grip, BUT only as long as the driver maintains a SAFE SPEED. Unskilled drivers or those who can't gauge their own and their car's limits, are advised to mount the tires with more tread on the rear.
The German ADAC conducted tests on wet and dry road and concluded that a below average or average driver was advised to mount the tires with more tread on the rear, as loss of control announced itself less drastically. That goes for cars with all drive systems, including AWD.
The advantage of having the tires with more tread on the front are superior grip, better handling and steering response, and better braking.
The consensus seems to be that skilled drivers can enjoy better tire performance with the more grippy tires on the front.
This could be so if hydroplaning was the only issue and the ''skilled'' drivers avoiding drinking or using their cell phones and other things taking the edge of their performance. Hydroplaning isn't that big of a deal anyhow. It only happens with a combination of high speed and exceptionally hard rain. The skilled driver anticipates it, and backs off a little at the first sign of it with no problem.
A big issue is braking. You can buy sedans even better balanced than Vader's 55/45 Impala. However most of the stuff on the road are FWD cars and unloaded trucks, both of which are front end heavy. It is very easy to break the back end loose and difficult to keep it from coming around. If you spin, you best have lots of unobstructed space around you. Hitting a curb going sideways can roll you. ABS helps, but I want some tread back there.
The front tires that came on my Cavalier are staying there as long as their performance is acceptable. Then the rears will move up front, and something new to the back. I have been following the ''Need quiet tires'' thread. Looks like I can find something quieter than the OEM Goodyears and with as good or better ride and wet traction.
A big issue is braking. You can buy sedans even better balanced than Vader's 55/45 Impala. However most of the stuff on the road are FWD cars and unloaded trucks, both of which are front end heavy. It is very easy to break the back end loose and difficult to keep it from coming around. If you spin, you best have lots of unobstructed space around you. Hitting a curb going sideways can roll you. ABS helps, but I want some tread back there.
The front tires that came on my Cavalier are staying there as long as their performance is acceptable. Then the rears will move up front, and something new to the back. I have been following the ''Need quiet tires'' thread. Looks like I can find something quieter than the OEM Goodyears and with as good or better ride and wet traction.
- Status
