02-02-2019, 06:40 PM | #1 |
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AWD in Rain
So with my new car had an opportunity to test the X-Drive in the rain. It was good and fine, but like any car not immune to hydroplane. So as any driver, one needs to be cognizant of the hydroplane. End of day, was quite pleased on how the summer tires which came with car did in the rain. Cranked it safely to 95mph at times generally cruise at 80 and car was very stable I'd say 110+ x-drive rain or maybe 120+rain with no pooling water would be just fine for this car. Not advocating same, just an observation.
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02-02-2019, 07:50 PM | #2 |
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Read and heard a few times that at high speed on the lambo Miura the front got so light you could turn the front wheels left to right and the car would track straight.
If you search YouTube you should be able to find videos of hydroplaning testing where the car track straight but you can turn the wheel left and right. This video is close but not the crazy amount of lift I’ve seen in some test Last edited by overcoil; 02-02-2019 at 07:57 PM.. |
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02-02-2019, 08:07 PM | #3 |
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...was shot at Palmer Motorsports Park, a track which, unlike tracks with wider pavement and plenty of runoff room with no fixed objects in sight, is no place to practice car control - wet or dry.
I doubt he was hydroplaning. My experience is that playing with the steering wheel while hydroplaning has no effect upon the direction the car is going (i.e., that's the definition of hydroplaning). Nevertheless, the driver did well to keep the car on the track.
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02-03-2019, 08:34 AM | #4 |
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AWD is good for accelerating quickly in slick conditions. Nothing more. Adds weight, complication, and cost. Does not turn or stop any better than RWD. Some claim AWD will "pull you out of a corner" better, but that's only after you enter the turn slower or to make up for plowing understeer from the additional weight towards the front of the car. Unless one is a rally driver or after stop light victories in the rain, I'm not sure I understand the obsession with AWD cars. I had a '16 WRX for a year and a half. Do not miss the poor handling and inability to rotate the car with throttle input.
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02-03-2019, 09:16 AM | #5 | |
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I don't see how on a truly water covered surface one can drive safely any tire without hydroplaning at 100mph unless tires are at unreasonably high tire pressures. (Notwithstanding the issue of driving 100mph on any public road, even in the best conditions.)
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02-03-2019, 12:39 PM | #6 |
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In its simplist form: Tires, tires, tires. This is the main key!
A good set of specific tires (bearing in mind the weather & road conditions) will suffice in most cases... Due to the fact I live in the Midwest, with varying temp changes & inclement weather, I would always choose AWD & a good set of A/S tires, all day long, but that's just me... If I lived where the temps barely drop below 40 degrees Fahrenheit, I'd never consider AWD, but again, that's just my opinion. If I only owned one car, and lived in the Midwest, I'd pick a vehicle w/AWD, due to reasons outlined, supra... Cheers/B
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02-03-2019, 12:52 PM | #7 | |
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The run-flats that came on my M240Xi were shit in the rain at higher speeds. When I switched to Pilot Sport A/S 3+, the car grew some balls in slick conditions. Even with the tires at half life, their still much better than the crap OEM run-flats in the rain. Snow and dry are no comparison as well. Sure, the AWD will launch much better in the rain, snow, ice, and even the dry, but what it won't do is turn, slow, cruise, or stop better. That's all tires. |
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02-04-2019, 09:49 AM | #8 |
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What does CA man consider to be rain?
My experience is that a shower in SoCa gets the reaction that a hurricane gets on the east coast. I can't imagine driving at those speeds in serious rain in any vehicle. The lack of visibility compounded with the likelihood of hydroplaning strike me as a sure death sentence. Also, DO NOT EVERY USE CRUISE CONTROL IN THE RAIN! |
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02-04-2019, 10:15 AM | #9 |
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Automakers need to make it clear to people that AWD doesn't have anything to do with what the OP is talking about. I have a feeling a ton of people think this way...
Don't go 95 in the rain because you have AWD. |
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02-04-2019, 11:01 AM | #10 | |
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Lastly, why in the world would someone want to go so fast in the rain on a public road or non-professional sanctioned race event If there is any standing water, one should dial back speed. There are enough obstacles to contend with on the street in the dry. Why push your luck in the wet?
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02-04-2019, 02:30 PM | #11 | |
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It actually drives fairly close to RWD. (Randy Pobst understeer/oversteer scale from -10 to 10, it may be 1 to 1.5 vs -0.5 for M235 RWD he drove in Motor Trend review ) Also, one of the instructor from a BMW driving event mentioned that Xdrive car will be faster than RWD by about half second around the AutoX course they used. (Although it was 540) xdrive does have it's advantage for quick acceleration. (start line, out of the corner...etc) However, everything else will be on tire, not the drive train. (especially like hydroplaning, pretty much 100% on tire) I don't even understand why OP even mentioned hydroplaning and xdrive together. |
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02-04-2019, 04:48 PM | #12 |
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BMW's xdrive system is one of the least "performance" focused AWD systems out there. The AWD systems used in the higher end Audi, Nissan, and Subaru win that game. Xdrive is one size fits all in BMW cars. Compared to those systems, it's pretty slow to react plus no limited slips diffs on the xdrive either.
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02-04-2019, 06:32 PM | #13 | ||
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02-04-2019, 06:49 PM | #14 | |
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02-04-2019, 10:33 PM | #15 | |
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I do wish that I have LSD though. That will be a killer. |
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02-05-2019, 08:58 PM | #16 |
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I appreciate everyone's thoughts, and I came here to learn about the car as well. So all input is appreciated. As someone who has been on various car message boards for over 20 years nothing shocking with what I consider some of the admonishment type posts. Point taken. I've owned powerful RWD cars in the past, and currently have a 2011 vette with 4S tires. End of day, everyone has opinions and such, some are purists, and like the option of widowmaker oversteer on tap and that, and it's all good. Realistically, to chastise 95 mph straightline motoring in a heavy rain seems a bit of a disservice to the capabilities of the car (my opinion, and I never said it was a public road, but that is neither here nor there). Again, everyone has thoughts, and I respect that. Equally interesting is how some folks are quick to throw the BMW AWD technology under the bus. Alas, I don't know yet. Had a 2010 Audi S5 which I put about 60K on and sold for $ for this car, which is not even out of break in, but seems to possess similar properties and capability. So what do some folks say, Cheers .
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02-06-2019, 01:10 AM | #17 | |
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I probably should have clarified, but my comments above were in regards to how AWD affects overall handling capabilities and characteristics of a traditional sports car or sports coupe, which is the type of car that one usually buys for thrills and smiles. This does not mean AWD doesn't have a place in motoring. The reality is that someone who commutes daily in year-round or long-season wet or winter conditions would be foolish to not choose an AWD system. No one should be taking hard corners or enjoying the benefits of RWD balance in those conditions... AWD also makes sense in super high HP cars where there simply isn't enough rear wheel grip to make use of all the power even in dry conditions. Think F90 M5, Porsche 911 Turbo, etc.
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02-06-2019, 07:54 AM | #18 |
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The Quattro system on the transverse engined Audis in the A3, S3, RS3 and TTRS use a Haldex centre clutch system that can only send a maximum of 50% of power to the rear wheels, one of the reasons it is optional to have wider front tyres than rear tyres on the RS3 to quell understeer. The BMW system is a lot more flexible in power distribution than the Audi Haldex system.
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02-06-2019, 12:47 PM | #19 |
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There are different types of Audi AWD systems as there are Subaru and some a better than others. BMW's Xdrive system isn't has good as the best systems from Audi and Subaru. If BMW incorporated at least a rear LSD with the Xdrive M235/240 and forced even more RWD bias through better management, it could be a pretty good performance AWD system on a 2 series.
The current gen M5's "M"-xdrive is pretty clever. Though I still think the car should be RWD only, I can see why BMW did it as most drivers aren't good and would have trouble keeping such power on the road only driving two wheels. The M x-drive system uses the trick eLSD and has a ton of RWD bias. Better yet, it can be shut off and be full on RWD. With that said, an RWD M235/240 is entirely fine in the wet and snow with the proper tires. I've been doing it for 3 years in the Midwest winters on performance winter tires and even those are overkill. I'm going back to Conti DWS06s.
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02-06-2019, 02:28 PM | #20 |
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It's often forgotten, in the discussions over winter tyres for snow, that they are as much engineered to reduce aquaplaning as they are for running in cold conditions. In a typically wet British winter, the wet-weather handling on my M235i is noticeably improved when I switch to my winters (Pirelli Winter Sottozero S3). And there have been occasions in midsummer thunderstorms when I'd much rather be on my winters. As you can see, the winters simply have much more water-carrying and dispersion capacity, and note how the tread pattern allows drainage to occur both sides of the contact patch on the winters (right):
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02-06-2019, 02:34 PM | #21 | |
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Subaru still uses Viscous coupling center differential and open front and rear differential for WRX. Only WRX sti has LSD in front and rear as well as the adjustable center diff. Audi's quattro recently added torque vectoring rear diff for their S and RS models as an option. Their regular AWD is not any better than BMW's. One of the most advanced AWD is from Acura. SH-awd was the first torque vectoring diff. Then Evo copied it and called 'active yaw control'. lol |
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02-13-2019, 03:53 AM | #22 | ||
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