Safe Speed Forums

Indeed - supposedly locking a wheel once can then produce a vibration that stays with them until the next pit stop. Not much fun when you're already in a less than luxuriously comfortable environment..!

Have you got the message yet that ABS is NOT a good thing on loose surfaces?

Based on what information

http://www.msgroup.org/TIP083.html
There are tests that show improved stopping performance (for cars and trucks) on WET surfaces, where drivers are more apt to overuse their brakes to the point of locking them, but there are several other studies that demonstrate absolutely convincingly that braking distances increase with ABS over non-ABS equipped vehicles when riding on loose gravel or snow covered surfaces. (This, because gravel and loose snow piles up and tends to create a 'dam' in front of a locked wheel where a rolling wheel tends to ride up and over a much smaller 'dam'.)

http://en.wikipedia.org/wiki/Anti-lock_braking_system
In gravel and snow, ABS tends to increase braking distances. On these surfaces, locked wheels dig in and stop the vehicle more quickly. ABS prevents this from occurring.

http://www.dervman.com/abs.htm
Some cars had an ABS override switch, whereby the driver could turn the system off. Why would you want to do this? There are two reasons - one being that an experienced driver might want to eke out a bit more braking performance at a track day (see below), and the other being that you were driving on a snow covered road (or indeed, on gravel driveways). This is because snow building up in front of a locked wheel improves braking performance. Of course, with ABS, this does not happen since the wheel is not locked for long enough! For some (foolish) drivers, the perceived dismal braking performance of ABS equipped cars can come as a big surprise in snowy conditions!

http://bmwdean.home.att.net/abs.htm
Why doesn't his magazine include real-world braking tests including on dry pavement, wet pavement, gravel roads, and paved roads with sand or gravel on them. The response I received was that it would be too dangerous for the magazine's riders to stop in those conditions on bikes without ABS brakes, so they don't do it.

http://www.gmfleet.com/us/products/specialized/police/safety/abs.html
On some surfaces, such as gravel roads, braking distances can be longer, but you will still have the control benefits of ABS.

http://www.mucda.mb.ca/aboutabs.htm
You should allow for a longer stopping distance with ABS than for conventional brakes when driving on gravel, slush, and snow. This is because the rotating tire will stay on top of this low traction road surface covering, and effectively "float" on this boundary layer.

A non ABS braked vehicle can lock its tires and create a snow plow effect in front of the tires which helps slow the vehicle. These locked tires can often find more traction below this boundary layer.

http://www.abs-education.org/faqs/faqindex.htm
In what circumstances might conventional brakes have an advantage over ABS? There are some conditions where stopping distance may be shorter without ABS. For example, in cases where the road is covered with loose gravel or freshly fallen snow, the locked wheels of a non-ABS car build up a wedge of gravel or snow, which can contribute to a shortening of the braking distance.

http://www.audi.com.sg/glossary/a/abs.htm
A note on ABS: when driving on certain surfaces like gravel or snow on a hard road surface, ABS may result in longer stopping distances.

http://www.honda-acura.net/forums/archive/index.php/t-25220.html
Gasoline Fumes10-01-2002, 04:19 AM
Road & Track did an ABS test a few years ago using a Mercedes modified so the ABS could be switched on and off. ABS stopped sooner on almost all surfaces. Snow, ice and gravel were where ABS didn't work too great (tires locked up worked the best here). On dry pavement ABS will win every time. If I ever have a car with ABS, I will be adding a switch.

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1stGenCRXer10-01-2002, 06:57 PM
Yep, there's no way you can modulate the brakes faster than a computer w/ actuator. On pavement, ABS is the way to go. On extremely slick surfaces, such as snow and ice, ABS is still the way to go because a wheel slowing down still has more grip to the pavement than a sliding tire. On gravel, mud or sand, where a stopped tire will pile up the material infront of the tire, effectively "digging in," then non-ABS will help you stop the quickest, but may also get you stuck. All in all, if you have the option and don't mind the extra heft, ABS reigns.

http://www.ambulancedriving.com/extra-info/ex-u1-e4-pce-09.html
On some loose gravel surfaces and fresh snow, ABS may activate before the tyres have had a chance to 'bite down' into the true road surface. In this case, braking distances for an ABS equipped vehicle may be greater than a non-ABS vehicle.