RWD can't get up a wet paved road from a standstill?

[mbt]

went to megamall last night when it was raining hard, and there was a bit of drama on the carpark ramps... a Starex couldn't get up the wet ramp and was just vaporizing its rear tires to thick, expensive smoke. the security guards had to push it up the ramp.

the Adventure behind it (which had to stop to give the starex room to roll back in case) and in front of me had a similarly hard time launching, the rear tires simply couldn't find any grip and the driver was flooring the pedal to no avail. it had to be pushed up as well.

however, the Venture I was driving didn't have any problems going up the wet ramp from a standstill, and the Civic behind me didn't have a problem too

bakit ganun? disadvantaged ba talaga yung RWD up wet inclines?

what could you do to manage the wet incline if you were driving a RWD vehicle, in case you had to stop and couldn't get up? would applying the brakes (foot brake or park brake) while gently opening the throttle do the trick?

[Rediesel]

baka kalbo na yung mga tires nila.

taois sobra yung pag apak sa accelerator, dapat moderate lang or in case too much wheel spin on diesels sa 1st gear pwede 2nd gear.

AFAIK mas llamado nga yung RWD sa paakyat kesa FWD.

[rsnald]

yun din ang alam ko e, mas lamang dapat ang RWD sa upramp climbs dahil mas malakas ang tyre friction sa rear wheels vs. front wheels. baka tyre contact lang nagkatalo, mas malapad yata gulong ng venture vs. starex and adventure tapos mas mabigat pa. yung sa honda naman, baka mas bago gulong...

traction lang nagkatalo yan and coefficient of friction. naalala ko tuloy yung physics lessons ko nung HS pa ko

[RedHorse]

Originally posted by mbt

what could you do to manage the wet incline if you were driving a RWD vehicle, in case you had to stop and couldn't get up? would applying the brakes (foot brake or park brake) while gently opening the throttle do the trick?

yes.

timing sa release ng hand brake. Pero di ko pa nasubukan sa ford, kasi foot break yon and left hand release. Eh sanay na ako na left hand gamit ko sa wheel.

[splerdu]

I saw a similar case going up the Shangri-La multilevel parking. A local diesel pickup couldn't get up, and it wasn't even raining. The guards sat in the bed until the truck could get a move on.

This has nothing to do with RWD but rather with weight distribution. There prolly isn't enough weight at the rear for the tires to grip properly, pointing to an overly front-heavy vehicle design. Nothing unexpected though, those vehicles, starex, adventure, lcv pickup, etc. are designed to be able to load a lot of weight on their rear so when unladen the rear is really very light and the suspension too hard to get proper grip.

[splerdu]

what could you do to manage the wet incline if you were driving a RWD vehicle, in case you had to stop and couldn't get up? would applying the brakes (foot brake or park brake) while gently opening the throttle do the trick?

The technique is similar to the manual-diff lock trick. 4x4 magazine covered it, you basically move at a crawl and give light pressure on the brake pedal just heavy enough to keep a loose wheel from spinning but still light enough to not stall the engine. The end result is similar to pseudo-differential locking in newer SUVs (X5, MDX, etc.). In an issue last year, they demoed this using a Jimny going through a mogul. Opposing tires lifted and spun, then without locking any diffs they got it to move forward using the left-foot braking technique.

[ghosthunter]

Originally posted by mbt
went to megamall last night when it was raining hard, and there was a bit of drama on the carpark ramps... a Starex couldn't get up the wet ramp and was just vaporizing its rear tires to thick, expensive smoke. the security guards had to push it up the ramp.

the Adventure behind it (which had to stop to give the starex room to roll back in case) and in front of me had a similarly hard time launching, the rear tires simply couldn't find any grip and the driver was flooring the pedal to no avail. it had to be pushed up as well.

however, the Venture I was driving didn't have any problems going up the wet ramp from a standstill, and the Civic behind me didn't have a problem too

bakit ganun? disadvantaged ba talaga yung RWD up wet inclines?

what could you do to manage the wet incline if you were driving a RWD vehicle, in case you had to stop and couldn't get up? would applying the brakes (foot brake or park brake) while gently opening the throttle do the trick?

The problem is a combination of two factors:

1. weight distribution... the engine is in front & the van/pickup is RWD. The drive wheels don't have enough weight on top of it to give them a good grip.

2. open differential... once one wheel starts to slip, all power from the engine goes to that wheel. If the vehicle was equipted with a limited slip differential (LSD), the entire incident wouldn't have happened.

[Supierreman]

baka sinubukan mag burnout hehe

[Rod & Bubbles]

Actually, in that condition, even an lsd equipped vehicle will have a problem. Its mainly a traction problem. Lsd will help but only to an extent. Btw, pagkakaalam ko LSD ang starex diba.

Tire brand makes a big difference in this aspect. Tire width doesn't matter. Its the tire compound. A soft compound tire would grip better. Hondas, being lighter would have softer compound tires (depends din on the brand) designed to grip the road for better handling. A load carrying vehicle, would have harder compound rubber to withstand the heavy loads and still provide acceptable tire wear. Of course at the expense of handling but then you won't corner an AUV at 120 kp/h.

This is also the reason why many dedicated off road tires, like my swampers wear faster on pavement (aside from the tread design). Off road tires are made with soft compound rubber to grip rocks better and be soft enough to flex and wrap the tread around an obstacle. At the expense of load carrying capacity. The max. load rating on my tires are 2250 lbs. per tire, i think. Many SUV AT tires have a higher load rating.

[kiper]

san ulit yan? megamall?

masubukan nga..4x4 rulez..!!

hmm..pero sa malamang tire traction ang naging problema nila..sa ganung sitwasyon lang naman hindi hahatak ang sasakyan eh.

[kimpOy]

driver skills siguro

[mbt]

come to think of it, the ramps in the megamall carpark aren't completely flat. the surface is 'toothed'... maybe that's why the tires, with an even smaller sontact patch because of the road surface, had a particularly tough time scrambling for traction

kiper,

traction nga yung problema, i think that's rather obvious :D

rod,

hindi lahat ng starex may LSD.

[boybi]

kakayanin kaya yan ng patrol ko na 4x2 lang? sa shangrila di naman nahihirapan yung patrol. lagi nga lang tumatama yung gulong dun sa maliit na parang center island and sa side.

meron din ba effect kung over inflated yung mga tires ng adventure and starex?

[Ungas]

Over-flated tires will have less traction. That's why you hear people from offroading world lower their tire pressures on some trails.

[mbt]

if the tires are overinflated, mas maliit pa lalo yung contact patch nung goma (gitna lang nung goma yung dumidikit sa daan)

[boybi]

which would have better traction? H/T tires or A/T tires?

[pajerokid]

boybi, depends on where youre trying to tread on.

Sa highway(on road), HTs are way better coz mas malaki contact area nila sa tarmac.

Off road, A/Ts grip more coz the Thread blocks are designed to bite the dust (Queen hehehe :D )

[sixpack]

i think hindi smooth ang pag release niya sa clutch, kasi ones the tires start to spin, it looses traction

[johnqpublic318]

Originally posted by splerdu
The technique is similar to the manual-diff lock trick. 4x4 magazine covered it, you basically move at a crawl and give light pressure on the brake pedal just heavy enough to keep a loose wheel from spinning but still light enough to not stall the engine. The end result is similar to pseudo-differential locking in newer SUVs (X5, MDX, etc.). In an issue last year, they demoed this using a Jimny going through a mogul. Opposing tires lifted and spun, then without locking any diffs they got it to move forward using the left-foot braking technique.

Correct... If vehicle is just a 2wd, apply a few notches (2-4) of the parking brake while going up... Yes, drive with the parking brake "on" until ramp or obstacle is cleared. This will have the same effect as sperdu's technique without any resistance from the front brakes.

[HBOY]

main problem encountered is since twisty yung ramp, one of the rear wheels are not properly planted on the ramp... subukan mong umakyat ng incline (maybe a small gutter in an angle... aangat yung likod mo)... saa FWD this does not happe, hence you have the grip...

guess where this problem is evident?... dun sa parking lot sa shangrila. steep grade na paliko.. instant lifting of rear tire closest to teh curve.