Tony
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Posts posted by Tony
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This topic definitely cannot be explained in one post so small informative increments will over time cover the whole picture.
Scrub Radius ( SR ) is the point that all the Geometrical angles at the front are placed. When a Geometry is measured the figures suggest an area within the radii and careful positions conclude all the forces to ensure the car performs as desired.... but what are these forces? and what do they look like?
This image displays three angles the other six would have made things even more complicated, we will work on them at a later date.
Nevertheless you can see these angles in 3D, we have 'Longitudinal, lateral and vertical' And the 'SR' is the recipient, ( triangulate)
The 'SR' is the contact area between the tyre and the road, these 'forces' need to be directed to specific areas of that patch...... To far to the outside with the Camber will make the car pull...... To far in will make the tyre wear, to much toe out will make the car bump steer and nervous, to little will make it lazy, both if incorrect will force the tyres to wear. The Castor will add/retract directional control, add/retract the Turing radii, all of this is the direct consequence of the positions within the 'SR' there are also indirect consequences....again this we will discuss later.
Add to this any modifications then calculating the placement of these three angles becomes a nightmare. But not impossible
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The only major experience I've had was the day after I got two new rear tyres on my IS200.
On a wet roundabout, only doing about 10mph the back end decided to go walk-about - I over-corrected which snapped the back end round the other way and the rear of the car ended up going sideways into the kerb:
Whoops!
Oh my word i never know about that incident!..... with the known problems the Lex has with Geometry maybe you were not entirely to blame?
I remember almost poohing my pants the time I took the Tubby out for a test drive - It was a cold November morning and there must have been some frost on the gound.I was doing no more than 30mph on a rural Nothamptonshire lane and gave the throttle a boot to see how the turbo spooled up. Instantly the back end shot out to the left and I was heading for the hedge! I managed to steer into the slide and corrected but not before I was on the grass verge
Fortunately there was no contact with anything other than the grass, but it taught me to treat this powerful car with a bit more respect!
Do you feel to much power in truth is a bad thing..... i like you would go for the maximum possible but it makes you wonder when even experienced people like yourself can be bittern what would happen it it were one of the Max power boys on a 'cruse trip'
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Understeer is a condition when during cornering the circular path of the vehicles motion is greater than the circle indicated by the direction that the wheels are pointed. This circumstance allows the front tyres to lose traction during a turn, causing the car to either not turn as tightly as expected or continue in a straight line.
Manufacturers today tend to configure Understeer into the design by default, seemingly it is thought that if the car Understeers slightly it tends to be more stable if a violent change of direction occurs, improving safety, this i don't entirely agree with
Under all high speed conditions cornering with pneumatic tyres generates amplification of the slip angle (side slip) velocity this is in reply to the direction in which the wheels are pointed. If the slip angle of the front and rear wheels is equal, the car is in a neutral steering state, if the slip angle of the front wheels exceeds that of the rear, the vehicle is said to be understeering.
All vehicles understeer or oversteer at different times based on road conditions, speed and available traction. The design of the vehicle, will tend to produce a particular 'terminal' condition when pushed to the limit of available traction, then the 'Terminal Understeer' refers to a vehicle which, as a function of its design, tends to understeer when cornering loads exceed tyre traction.
Terminal handling conditions are a function born from vehical length and front/ rear weight distribution this is the polar moment of inertia and front and rear tyre traction. Further modified by the relative roll stiffness front and rear, which affects the outward weight transfer during cornering.
A front heavy car with low rear roll stiffness albeit soft springs or insufficient sway tension will have a tendency for terminal understeer. The front tyres being more heavily loaded will reach the limits of grip before the rear tyres, and thus develop larger slip angles.
Although understeer and oversteer can cause a loss of control, many manufacturers design their cars for terminal understeer in the belief that it is easier for the average driver to control than terminal oversteer. Unlike terminal oversteer, which requires several steering corrections, understeer can often be reduced simply by reducing speed.
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Taken from the fact the car delivers a reply from your foot have you been caught out by this reply... what was your worst experience with the cars handling.... and how did you deal with this?
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Oversteer is when the rear tyres suffer a lose of traction during a cornering situation, causing the rear of the car to head towards the outside of the corner. A more technically correct definition is that oversteer is the condition when the slip angle of the rear tyres exceeds that of the front tyres. Older rear wheel drive cars were generally more prone to oversteer, in particular when applying power in a tight corner.
Contrary to popular opinion, modern rear wheel drive cars are much more user-friendly in this regard as they are set-up to understeer, the more powerful ones even have on-board computer systems which can automatically brake the car or override the drivers throttle inputs.
This is because understeer is generally much safer for new drivers, whereas oversteer is much more difficult to correct when not prepared for it.
The natural reaction of most drivers in the event of losing control is to try to slow down, either by lifting of the throttle or braking. Both of these will help bring an understeering vehicle under control but can have disastrous effects in the case of oversteer.
This is because braking causes weight transfer toward the front of the car, reducing the rear traction even further. The correct oversteer correction is to gently steer into the slide then take the power away as needed.
In fact cutting the power at mid-corner can induce oversteer even on front wheel drive vehicles. This is known as 'lift off oversteer'
A car that tends to neither oversteer or understeer when pushing to the limit is said to have neutral handling. Most racing drivers prefer their cars set-up just on the oversteer side of neutral. This is almost always the fastest set-up as it helps the car on tight corners.
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no commet... just
Dan Discount is the 'Access'
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I have available access to machinery that will 'cold roll' compressed alloy wheels and re-shape the inner dish....Scarface would be a perfect example for compressed wheel damage aligner since two of his new wheels were ovaled after hitting Motorway debris........... anyway what do you feel about this new saviour of wheels?
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They are 225-40/18 i know since i fitted them
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Im after 4 new tyres Proxe's TI-R 225/35/18 anyone know where the best place to get from ?
Try some searches on line with BC and mytyre and display what you find..... after that allow interests to compete here..........
Thanks Tony.
Had a look at both, mytyre's best, unless you know any better
Toyo Proxe's t1-r 87y rim/pro = £107.40 incl vat + post
Goodyear Eagle F1 G3-D3 £117.60
Bridgestone Potenza S-03 pole position rf doudle marking 87zr £137.50
All 225/35/18
looking for 4 will want fitting and car setting up with new wheels and everything else please
Thanks Gordon
Anyone better the prices, or know somewhere ?
Not me..... my best price is £117.60 for the F1 fully fitted......... and that's undercutting BC.
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Also having fitted:
HKS FCON V PRO + harness
HKS Navigator
HKS MAP SENSOR + Harness
The car should now be future poof.. ready for internals...then upping the rev limiter and boost..boost..boost
How have things gone
i am very interested to know how much 'warp speed' TDI have infused into the car.... -
As far as I'm aware, the only way plod could book you is under the "Construction & Use" legislation whereby plod would need to be able to show that the excessive camber was dangerous.
Interesting..... i never thought the Geo could violate the law until a post here earlier. I wonder if anyone has ever been booked for the offence, even more interesting is the Geo is not part of the MOT even if the angles do look extreme.... whereas in Germany front wheel alignment is part of the test.
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Does anyone know if modifying the Geometry to the extreme is against the law?
Typical visual angle would be Camber.... if plod saw this could he do you for it?
If yes then what would the offence be.....
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that bulletin is just showing how to put the steering wheel straight, bit of a cheat really because if the alignment was correct in the first place this problem wouldn't exist, as tony quoted in his post if the thrust-line is dead centre then front wheels can be set to match with no problem, but if the rear wheels are slightly toeing to one side, then even though the front tracking may appear to be correct the steering will need to be held at an angle to correct the problem. ever seen an old mini 'crabbing'?
"ever seen an old mini 'crabbing'?"... that is so funny when I get behind one doing that
Indeed
i wonder if extreme Geometry positions are illegal? Like crabbing or very low camber? i think i will ask........ -
Oerrrrr..the Tubby
Should be ....... wheel off, caliper off, carrier off, disc off, then the drive flange with studs should be visible. Look to see if the studs will pass the hub? if they do then hammer them out, if not then the 'flange' will need to be removed, but this will split the bearing so this will also need to be replaced.
Assuming the studs will pass the hub then the re-build is easy.... all studs have a spline fitment, so the new studs only need to be 'pulled' back into the flange, best method is to offer the stud 'loose' from behind, place a spacer over the exposed thread and use the wheel nut on the stud to pull it through, the spacer is a must! since the thread does not cover the whole length of the stud.
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As odd as it seems the manufacturing industry does not have a commercial reference table for the vehicles ride height, the information is vital for the pre-inspection before any Alignment or Geometry is performed.
I challenged the industry for the data, the best they could offer was some A4 typed pages relating to about 40% of cars, this i can make available by request.
Suspension travel (Curve) is vital in all areas relating to Handling/ Geometry/ Breaking and general performance, unmodified car owners should be aware that a difference of 10mm in height over the axle measured from mid-arch to mid-wheel may suggest a sagging or broken coil spring.
This is an example picture of the damage by excessive suspension travel.
Obvious tears in the bushing is visible, this is totally due to the ( Curve ) exported to the wishbone by the suspension travel, an accident waiting to happen!
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People power is something i enjoy........ to often decent requests become unanswered via denial or ignorance. Today's example belayed my normal opinion and showed real customer care, i solute the Dealer in question.
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I had a call today to book an IS200 for a Geometry....... in conversation the Lady explained the Dealer had set the Geometry eight months ago but once again the front tyres are wearing on the inside.... The Dealer was aware that the positions were wrong by 'Manufacturer' and directed the owner to wim because i can deviate from these positions.
First i feel really sad that the Dealers know there is a problem but cannot react to it... secondly i feel proud they direct the customer to me.... Well that's great but what about all the others that sufferer the same problem without direction?
......... We will get there eventually.
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I have a pair of 15mm H&R hubcentric spacers to fit to the fronts, which will require the standard studs being replaced with the longer studs that are supplied with the spacers.
How easy to fit?
Which car are these for?
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Got it!
So we will try to go for:
Front
Camber: -25' to -15' (but not less), both wheels not more than 10' disparity.
Castor: will be worked out through castor an toe, both wheels not more than 20' disparity.
Toe: +8' (+/-2') per side
Rear:
Camber: -1°20' (+/- 10')
Toe: +10' (+/-2') per side
Thanks a lot
Almost:- Castor will be worked through the ( Camber and toe ) Everything else is as you state..... let us know how things go!
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I still worry about my exhausts as they're rather loud
.Had the police behind me a couple of times, so I have to take it really steady with the gas... would/could they pull me?
Excluding actual DB measurements, the exhaust should sound 'similar' to the original factory fitment. Other than that a loud exhaust could just make you a target for the law.... to be fair some owners do abuse the noise to the max.
"the exhaust should sound 'similar' to the original factory fitment..." Mmmmm, that would be 0DB then
My intention was never to abuse the law, just wanted to be different... approaching my 40's (
), i'm not your typical "boy-racer" any more - hence I drive a Lexus I understand mate
Recently we had a Vectra in for MOT that had a big bore exhaust..... our old boy tester 'revved' this car time and time again in an attempt to (personally) decide if the sound was outside of the (similar) guidelines... in the end he decided it was and failed the car. -
Hi,
I have just had an alignment done using a Pro-Align SPACE 800, I gave the mechanic the required specs for the vehicle (350z) as the machine did not have the car in its database.
After getting my printout i have noticed that the Rim Diam is down as 14" where as my car has 18" wheels
Will this make a difference to the measurements taken? all readings on the sheet are in degrees and minutes, apart from the toe which is in mm.
Thanks
MrRoper
I spoke to Paul, the 14' diameter is 'default' if the car is measured as 'missing data'. He assures me the cameras 'scale' the wheels diameter automatically in this mode or it can be set manually. Nevertheless when you go back for the tyres the car will be re-measured to give you peace of mind.
Typical friendly conversation with Paul and he understood why you felt unhappy with printout.
Let us know how things go
Thanks Tony,
Its much appreciated that you spoke to Paul, I am sure everything will be fine. The service at Dury lane was excellent and I would be happy to recommend them, my last alignment done at the local tyre fitters was a mess so I am sure you appreciate my concerns
Thanks on some excellent advice and congratulations on an excellent website that has given me a good insight into the black art of car alignment!
Will let you know how it goes
You are welcome....... team work and technical support is all it takes.
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I still worry about my exhausts as they're rather loud .
Had the police behind me a couple of times, so I have to take it really steady with the gas... would/could they pull me?
Excluding actual DB measurements, the exhaust should sound 'similar' to the original factory fitment. Other than that a loud exhaust could just make you a target for the law.... to be fair some owners do abuse the noise to the max.
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Hi,
I have just had an alignment done using a Pro-Align SPACE 800, I gave the mechanic the required specs for the vehicle (350z) as the machine did not have the car in its database.
After getting my printout i have noticed that the Rim Diam is down as 14" where as my car has 18" wheels
Will this make a difference to the measurements taken? all readings on the sheet are in degrees and minutes, apart from the toe which is in mm.
Thanks
MrRoper
I spoke to Paul, the 14' diameter is 'default' if the car is measured as 'missing data'. He assures me the cameras 'scale' the wheels diameter automatically in this mode or it can be set manually. Nevertheless when you go back for the tyres the car will be re-measured to give you peace of mind.
Typical friendly conversation with Paul and he understood why you felt unhappy with printout.
Let us know how things go
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I just did a training in business english.. so please Tony forgive me but I have to ask again.
This is what you told me a few days befor:
The rearCamber: 1*20'- +- 10'
Toe : 10' per side+ +- 2'
The front
Camber: 25'- +0 -10' and even over the axle to 10'
Castor: I cannot answer since the position is dependent on the Cambers result, if possible the position should be high and even over the axle to 20'
Toe: 8'+ per side +- 2'
For the others... my car is a 99 Lexus IS200 droped abour 50mm by Eibach ProKit and Koni yellow sport shocks.
What I do understand:
Rear:
Camber 1*20' +/- 10' (means positiv between 1deg 10min TO 1deg 30min)
Toe: 10' per side +/- 2' (means positive between 8min and 12min)
Front Toe: Between 6' to 10' per side
What I don't understand:
Front:
Camber: 25'- +0-10' or even over axle to 10' (means between 25'min to 35'? What does even over the axle mean? I should go for 35'?)
For the castor: I will let them adjust it but have to talk back to you later with the Camber settings they have done
BTW: Fitted summerwheels last Friday. 18x8OS38 with 225/40R18 (used from last summer). Now it comes clear: The steering wheel is offcenter to the left and the car drifts slightly to the right!
The front left tire is worn on the inside.Your initial request was the Euro LOC members wanted an idea for safe positions on the IS200, to preserve tyre wear, these positions do deliver that.
In explanation the front camber positions (ideal) should be 25' neg... the + means no more... the - means the position could be 15' neg but no less.
Over the axle @ 10' is the nsf/osf disparity, the means that whatever figure is achieved i don't want more than 10' difference between the front wheels.
The Castor position is born indirectly from adjusting the camber and toe, so the end figure is dependent on the amount of adjustment required, i don't want more than 20' disparity between the nsf/osf.
As you can see the geometry will need to be worked for, blind turning of adjusters is not good enough for the IS.
Handling confessions
in General Problems / Discussions
Posted
Even more so when you have a 330 to burn