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  #16  
Old 06-17-2003, 08:46 PM
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Harvey,

There is another aspect to this. Many front wheel drive cars steer when torque is applied due to design limitations inhibiting an ideal set up. This particularly applies in respect of unequal length drive shafts and diff. action. A hot mini takes off sideways when real power is applied. Honda went to considerable trouble to balance out this problem.

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Last edited by Trevor; 06-17-2003 at 08:52 PM.
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  #17  
Old 06-18-2003, 01:05 AM
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Thanks for the info, Harvey & Trevor.

Makes a lot of sense and explains something that I have frequently wondered about.
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  #18  
Old 06-18-2003, 01:59 AM
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I guess this would make sense as the wider the tire, the further the distance of the tire's edges from their point of pivot thus the more leverage.

So if I'm understanding correctly, if the left tire had more tread on its outside edge, it would pivot clockwise under acceleration, steering the car rightward, as there is more grip to pull the car forward. The opposite would happen under braking as there is more grip/friction to stop the car, or under accelerating if the tread were greater on the inside edge.

And under instances of cornering, the outside wheel is supporting more of the car's weight and has more grip as a result. So accelerating into a turn would jerk the wheel in the opposite direction you're steering, as more weight equals more grip. Braking would jerk the car in the same direction you're turning.

I hope I understand correctly. Sorry if I'm not and thanks for explaining it.
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Last edited by DavieGravy; 06-18-2003 at 02:12 AM.
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  #19  
Old 06-18-2003, 06:55 AM
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Quote:
Originally posted by gl1674
Re torque steer - no, I do not even remember how torque steer feels like. My SVX does a fair bit of "gravity steer" - it does pull sideways whenever there is a dip in a road, and steering is generally on the heavy side, but torque steering is something it never does.
I have come to learn that out of wheel alignment causes this.
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  #20  
Old 06-18-2003, 07:02 AM
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Re: Torque steer

Quote:
Originally posted by DavieGravy
I noticed a bit of torque steer today under heavy acceleration. It only happened twice and I couldn't duplicate it after.
This may be the early signs of the RWD failing. This happened to me and it was a bad transfer valve solenoid assy. Be careful as there may be times when the car will pull/steer you off the road. It was rather quick, the involuntary steering that is, for me.

You also damage the front dif when the RWD is not working.

Do not worry about the roll back off the flat bed. The transfer clutches need power to engage and your car was off.
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  #21  
Old 06-18-2003, 07:10 AM
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Thanks for the advice svx_commuter, but my back left tire was nearly flat which was the problem.
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  #22  
Old 06-18-2003, 02:06 PM
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Quote:
Originally posted by DavieGravy

And under instances of cornering, the outside wheel is supporting more of the car's weight and has more grip as a result. So accelerating into a turn would jerk the wheel in the opposite direction you're steering, as more weight equals more grip. Braking would jerk the car in the same direction you're turning.
Oops, I think I got that backwards
Accelerating into a turn would pull you into the turn and braking would jerk the wheel outward. This would be on an even road surface with the same offset and tread on every tire.
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  #23  
Old 06-19-2003, 05:12 AM
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Re: Torque steer

Quote:
Originally posted by DavieGravy

Upon unloading the car from the bed of the tow truck, it would only roll far enough such that the back wheels touched the ground. This was because my back wheel had seized up due to bearing failure.

Did you post any info on the bearing failure?
How long did it make noise before it failed?

Thanks
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  #24  
Old 06-19-2003, 02:36 PM
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Re: Re: Torque steer

Quote:
Originally posted by svx_commuter


Did you post any info on the bearing failure?
How long did it make noise before it failed?

Thanks
I had it fixed right before the last Colorado meet. The mechanic didn't do it right and it went out completely on my way back. There was no noise and no warning whatsoever.

Before the first fix, it was making a lot of noise, but it never went out. I just couldn't deal with the sound anymore.

I would say that if a bearing were to completely fail out of long-term wear and tear, it would be making a hell of a noise before hand. I say that not because I know about cars, but because I've heard other members here say the same thing. And notice how you never hear anyone complaining that their wheel bearing completely failed because they neglected to have it fixed? Maybe some mechanics here would contradict that statement, but I haven't heard anyone here complain about that.

Just a thought.
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Last edited by DavieGravy; 06-19-2003 at 02:42 PM.
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  #25  
Old 06-19-2003, 06:07 PM
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Re: Damage front diff,,,,,,,Why?????

Quote:
Originally posted by svx_commuter


This may be the early signs of the RWD failing. This happened to me and it was a bad transfer valve solenoid assy. Be careful as there may be times when the car will pull/steer you off the road. It was rather quick, the involuntary steering that is, for me.

You also damage the front dif when the RWD is not working.


Gid’ay John, I have seen you say this a few times before, and have not seen the point. Though reading all the talk about the amount of torque steer, that you blokes all seem to have, got me thinking.

I think I have got the picture now. As you know the type of AWD that we have is different and does not have these traits, of torque steer, understeer. It does not happen, with our model.

In a front wheel drive car, and I suppose the FWD SVX would be the same, the front wheels are controlled to prevent wheel spin. The TCU detects the wheel starting to spin and sends the torque control signal to the engine, to turn down the power, till the wheel stops spinning. This is to prevent the type of torque steer that you are talking about. Trevor’s description of the sideways accelerating Mini Minor, is what it was like, before this type of control was used.

I think what is going on in the US model is, as a number of people have said, is the transfer clutch not working. In this case when clutch does not drive the back wheels, for the usual reasons. The front wheels start to spin, when this happens the TCU does not turn the power down, it just applies the transfer clutch, to move some of the torque to the back wheels. Then as far as the TCU is concerned if the front wheels are still spinning, than all the wheels are spinning, we know this condition is allowed to happen, eg in snow etc.

So if the US model experiences this severe torque steer problem, then the transfer clutch is not working, as it would not be possible to spin the front wheels, under normal AWD conditions. It would be the same if the FWD fuse were inserted.

So the front diff WILL, have an unusual amount of torque shock loading under these conditions, that could cause damage to it. Thinking back, there have been a number of Front diff failures, maybe this has been the cause?????

Funny how these things all come together in the end, to show the cause.

Harvey.
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Last edited by oab_au; 06-19-2003 at 06:10 PM.
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  #26  
Old 06-20-2003, 09:17 AM
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Yeah Harvey you got it!

Realize this too.
When the gas gets stomped on, the torque split is 50/50 as this is controled by the TPS and TCU. The line pressure goes to max as well as the transfer pressure. So when the RWD is not working there is 100% torque to the front wheels.

Add in that extra 37 HorsePower when the IRIS opens and you could find yourself in a tree.
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  #27  
Old 06-20-2003, 09:30 AM
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I only get an extra 35hp, what mod have you done for the extra 2?
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  #28  
Old 06-20-2003, 12:59 PM
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  #29  
Old 06-20-2003, 11:26 PM
DavieGravy DavieGravy is offline
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That was all great information and I enjoyed learning about it, but I still need to ask: Should a virtually flat back tire cause torque steer on the US model SVX?
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  #30  
Old 06-21-2003, 04:05 AM
DavieGravy DavieGravy is offline
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Quote:
Originally posted by Trevor
Yes Trevor, I understand the physics behind tire tread, acceleration, and deceleration. Less inflation equals less grip, I know. I just wasn’t sure how the US AWD system comes into play with this.

What's the difference between FWD and AWD in this situation? Why would torque steer be abnormal on an AWD vehicle and not on a FWD? I assume AWD implies a less of a differnce in overall grip of the car (from side to side) than it would on a 2WD car, but I don't really know.
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Last edited by DavieGravy; 06-21-2003 at 04:09 AM.
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