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        General >> Give/Need advice to/from others >> Still   pulling ?
        
(Message started by: mr._floppy on Apr 28^th, 2006, 12:43am)

Title: Still pulling ?
Post by mr._floppy on Apr 28^th, 2006, 12:43am

Fitted new wishbones and bushes yet still drifts to the left. Brakes are fine as are the springs and shocks.
Had the front alignment checked on them state of the art sooper dooper computer things. Camber within tolerances, Castor angle slightly out, but equal on both sides so it shouldn't pull, toe-in adjusted to perfection, yet it still drifts to left on cambered roads. My poor right arm is sore with continually correcting the steering. @

Apart from misaligned rear wheels "pushing" it to the left ( of which there's no evidence ), I'm stumped. :'(

Title: Re: Still pulling ?
Post by jonnycab on Apr 28^th, 2006, 3:18am

There are only four other suggestions I can think of:-
The outside of the tyres are more worn than the inside
You are stuck in the lorry gulleys
The car has been involved in an accident at some point & the subframe is bent
The rear brake is binding or the bearing is dry
Sorry if this isn't much help.

Title: Re: Still pulling ?
Post by Highlander on Apr 28^th, 2006, 4:17pm

tyres ok?
correct direction of rotation, pressures? same size? ;)
too big a difference in front treads might do it? 7mm on one and 2 on another?

rear inner wishbone bushes? allowing a "steering" effect?

Title: Re: Still pulling ?
Post by mr._floppy on Apr 29^th, 2006, 12:15am

As I'm replacing the two front discs after being on the car only 6ooo miles ??? ( the dreaded wobbly steering wheel when braking has returned ) I'll try swapping the two front tyres over, as one is almost done and the other almost new !

Title: Re: Still pulling ?
Post by Kjetil S on Apr 29^th, 2006, 3:31pm

on 04/29/06 at 00:15:16, mr._floppy wrote:

as one is almost done and the other almost new !

Couldn't this be the cause???

Title: Re: Still pulling ?
Post by mr._floppy on Apr 30^th, 2006, 12:30am

Swapping the two fronts has made an improvement, although I'm unsure if it's the difference in tyre tread ( which can only affect the N/S ride height by a couple of mm ) or a slightly biased alloy.

Mmmmm ( thinks ! 8)) Do you think the MOT tester will allow a 16" wheel on the N/S front and 15" for the others ?

Title: Re: Still pulling ?
Post by Kjetil S on Apr 30^th, 2006, 1:58am

Don't know about the UK laws and regulations, but I know it would be instant fail here in Norway. Probably not a good idea anyways. Up here it's illegal to use different tyre types (and therefore different wheel sizes) on the same axle, with good reason.

Edit: Will recalculate how much drag this would lead to tomorrow, when I'm more awake ;D

Title: Re: Still pulling ?
Post by Bren_K30 on Apr 30^th, 2006, 2:52am

And the same applies in the good old U.K

Bren

Title: Re: Still pulling ?
Post by Kjetil S on Apr 30^th, 2006, 1:52pm

Okay, did some quick math now.. In 100km/h (approx 60mph) and with 195x65R15's, a tyre worn 5mm more than the other (on the same axle) would "lag behind" 44cm or 17 inches per second. This should give the same effect as trying to roll an empty glass bottle of coke in a straight line :)

My calculations (someone will probably find a comma error or three):

New tyre

Height of rubber: 195*0,65*2mm = 253,5mm
Height of rim: 15"*2,54mm/in = 381mm
Total height: 634,5mm

Circumference: 2*Pi*(635,5mm/2) = 1993,34mm (Formula for circumference is 2Pi*r where r is half the diameter)

100km/h (62.5mph) = 27,78m/s (100/3,6)
converted to millimeters: 27777,78mm/s
wheel rotations per second: 27,78 / 1,993 = 13,94

worn tyre (-5mm)

Doing the same math as above, subtracting 10mm from the height, gives a circumference of 1961,92mm, 31,42mm less than the brand new one.

At 13,94 rotations per second, this makes a difference per second of (31,42*13,94) 437,99mm.

If anyone spots an error, please tell me ;)

A little note: 5mm wear difference on a 195x65R15 is A LOT, so this is probably bit extreme, but still possible.

Title: Re: Still pulling ?
Post by Snoopy on Apr 30^th, 2006, 4:18pm

there is an easy calculator on this site HERE (http://www.chris-longhurst.com/carbibles/tyre_bible.html) for working out Rolling radii and stuff like that saves getting the calculaotr out and also give you some very useful info!

Title: Re: Still pulling ?
Post by Kjetil S on Apr 30^th, 2006, 4:28pm

Seems like the circumference part was correct :)

The calculator didn't say much more than that

Title: Re: Still pulling ?
Post by Snoopy on Apr 30^th, 2006, 4:30pm

In theory you are correct but in practice you probably would not notice the difference in the rtyre sizes as the on with theLARGER tytre will just rotate slower and therfore NOT travel as far...... ;D ;D

Title: Re: Still pulling ?
Post by Highlander on Apr 30^th, 2006, 5:35pm

So is the pulling sorted now Mr Floppy? ;D

Title: Re: Still pulling ?
Post by jonnycab on Apr 30^th, 2006, 10:54pm

??? A little bit too technical for me....Einstein was a mathmatical genius, but I don't think he had the Scorpio in mind when he made his calculations.
A pulling to the left problem is probably a lot more simple, & nothing to do with simultaneous equations.
How long has it been pulling to the left Mr._Floppy?

Title: Re: Still pulling ?
Post by mr._floppy on May 1^st, 2006, 12:49am

It has always drifted left, the meatier tyre is now on the N/S and has counteracted the pull quite a bit. I've also adjusted the front alignment to a slight toe-out ( naughty, I know ::)) position which gives better straight ahead stability but slightly heavier steering.

However it's been a fruitful day, put new discs and pads on the front and rear and now the usually pathetic handbrake is back to full braking power and the wobbly steering has ( hopefully for good ) dissappeared.

Small tip: If you are trying to retract ( turning clockwise ) the rear caliper pistons and seem to be getting nowhere, try turning them anti-clockwise for a couple of turns then back to clockwise rotation.

Title: Re: Still pulling ?
Post by jonnycab on May 1^st, 2006, 1:06am

If it has always drifted to the left since you've had it, then could it be possible that the last owner had an accident, & even though it was repaired, the repairer failed to notice a distorted subframe?
Also, I assume you know this, but both front tyres should be the same size & so should both back tyres. The back tyres can be bigger than the front tyres for an MOT but not vice-versa.