Dodgy handling under heavy(ish) breaking
05 June 2000, 01:17 PM
#1
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I experienced it once a few weeks ago but thought it was just a one of (wet road or something). But it happened again this morning on a perfect dry road.
I was breaking from I reckon 60-70mph to 30-40 mph to enter a tight corner. As I was breaking it felt like the car was shifting slightly from side to side with some vibration through the steering wheel.
Any ideas what it was and why? How to correct?
Cheers,
Andrei
I was breaking from I reckon 60-70mph to 30-40 mph to enter a tight corner. As I was breaking it felt like the car was shifting slightly from side to side with some vibration through the steering wheel.
Any ideas what it was and why? How to correct?
Cheers,
Andrei
05 June 2000, 02:23 PM
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S,
I can think of a few things it could be straight off...
1) Tramlining - its where there's a rut / line / tarmac join in the road, and the car decides to try following it instead of the route you wish - can be a pain on multiply repaired roads....I tihnk theres supposed to be a geometry fix for this..anyone?
2) Unevevan pad wear. If one of your pads has worn more than the other, then heavy breaking will cause the car to pull somewhat to one side (obvious really) - get pads checked
3) Worn pads. If the car is just juddering a lot under heavy braking then it could be the pads are very worn or glazed...this tends to make the car shudder a bit - get pads checked
4) If you're still braking, and carying a bit too much speed into the corner, then you're making the car try and do too much at once. Due to the braking, all the weight has been transferred to the front. The then you're turning, shifting the loading force laterally - meaning you have significantly more weight over 1 wheel than the other three. If you dont steer in one single action, you'll likely notice the car squirming as its trying to sort all the different loading forces out. beware - its times like these, that if there's an unexpected puddle, oil or bicycle you could be visiting the hedge.....- dont brake so late and so hard is about the best fix here...and make sure you've done it before you turn!
It could easily be any of those, or something else entirely!
cheers
Night
I can think of a few things it could be straight off...
1) Tramlining - its where there's a rut / line / tarmac join in the road, and the car decides to try following it instead of the route you wish - can be a pain on multiply repaired roads....I tihnk theres supposed to be a geometry fix for this..anyone?
2) Unevevan pad wear. If one of your pads has worn more than the other, then heavy breaking will cause the car to pull somewhat to one side (obvious really) - get pads checked
3) Worn pads. If the car is just juddering a lot under heavy braking then it could be the pads are very worn or glazed...this tends to make the car shudder a bit - get pads checked
4) If you're still braking, and carying a bit too much speed into the corner, then you're making the car try and do too much at once. Due to the braking, all the weight has been transferred to the front. The then you're turning, shifting the loading force laterally - meaning you have significantly more weight over 1 wheel than the other three. If you dont steer in one single action, you'll likely notice the car squirming as its trying to sort all the different loading forces out. beware - its times like these, that if there's an unexpected puddle, oil or bicycle you could be visiting the hedge.....- dont brake so late and so hard is about the best fix here...and make sure you've done it before you turn!
It could easily be any of those, or something else entirely!
cheers
Night
05 June 2000, 10:57 PM
#5
HI,
I had exactly the same in a Primera GT this week when some prat pulled out of a side road without looking. Heavy braking from 60 ish on a long sweeping bend. On coming traffic so no option but to heave on the brakes. The front of the car "squirmed" left and right (bit like a minor tank slapper). I put it down to the cheap/barely legal tyres.
I have noticed that when taking roundabouts at a lively pace the side walls didn't inspire much confidence and could feel the car "rolling over" (i think) onto the shoulder of the tyre.
I have replaced these naff tyres and will let you know if I have the squirmy feeling the next time some prat decides to test my reactions.
JJones
[This message has been edited by jjones (edited 05-06-2000).]
I had exactly the same in a Primera GT this week when some prat pulled out of a side road without looking. Heavy braking from 60 ish on a long sweeping bend. On coming traffic so no option but to heave on the brakes. The front of the car "squirmed" left and right (bit like a minor tank slapper). I put it down to the cheap/barely legal tyres.
I have noticed that when taking roundabouts at a lively pace the side walls didn't inspire much confidence and could feel the car "rolling over" (i think) onto the shoulder of the tyre.
I have replaced these naff tyres and will let you know if I have the squirmy feeling the next time some prat decides to test my reactions.
JJones
[This message has been edited by jjones (edited 05-06-2000).]
06 June 2000, 06:02 PM
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I sympathise with the thought that the car has only done 5k miles. - My tyres are shot after 2000 miles!
Check out the outside edges of the tread blocks and compare them to those on the inside.
If you're into serious overspeed into corners with lots of understeer you will wear the outside edge of the tyre and in particular you will spoil the edges of the tread blocks. This is a major cause of tramlining.
Put new tyres on and hey, it all goes away.
The ultimate solution is to manage your speed more accurately into corners and minimise the amount of steering input used.
In fast cornering on the limit you can move the steering wheel a whole turn further than necessary with relatively little effect on cornering ability - this is called terminal understeer.
When the corner gets tighter the natural tendency is to turn the wheel more - on the limit this is not the best solution - the correct answer is usually to reduce steering angle slightly and gently lift off the throttle at the same time.
This combination moves more of the weight of the car onto the front wheel and at the same time ensures that you are operating in the optimum part of the tyre efficiency curve. Minimum slip angle also means that the tyre drag is minimised (its almost always better to have the tyre rolling than sliding).
Hope this is useful
Don
Check out the outside edges of the tread blocks and compare them to those on the inside.
If you're into serious overspeed into corners with lots of understeer you will wear the outside edge of the tyre and in particular you will spoil the edges of the tread blocks. This is a major cause of tramlining.
Put new tyres on and hey, it all goes away.
The ultimate solution is to manage your speed more accurately into corners and minimise the amount of steering input used.
In fast cornering on the limit you can move the steering wheel a whole turn further than necessary with relatively little effect on cornering ability - this is called terminal understeer.
When the corner gets tighter the natural tendency is to turn the wheel more - on the limit this is not the best solution - the correct answer is usually to reduce steering angle slightly and gently lift off the throttle at the same time.
This combination moves more of the weight of the car onto the front wheel and at the same time ensures that you are operating in the optimum part of the tyre efficiency curve. Minimum slip angle also means that the tyre drag is minimised (its almost always better to have the tyre rolling than sliding).
Hope this is useful
Don
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