Tony
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Posts posted by Tony
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When bigger alloy's are fitted should the tyre pressures be altered. I would have thought so but I've had varied oppinions on this.
The Missis FTO has 18" alloys with 225/35/18 tyres IIRC which are huge compaired to the std 16" wheels and scrubbs both inner and outer edges on both front tyres which screems under pressure to me. So how do I work out what it shoud be as they have been set on the factory pressures AFAIK
Good question..... first remember tyre pressures displayed by the manufacturer should be viewed as suggestions... within reason! move away from stock then you become the judge and jury. In answer to your question, there is a need to understand first so i question you this....
All cars display different pressures according to speed and load, do you know why?
Note: this method of reply is not an attempt to belittle you, it's designed to make you think!
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I've been building a 200SX S13 for track use. The chassis should be fairly well sorted. I've got Apex coilovers with 32way adjustable dampening, adjustable preload and adjustable ride height, front adjustable top mounts and rear adjustable upper arms. I also have 17" wheels with 215/45/17 Toyo Proxes TS-1
But where to start with setting it up? I know that it's probably best to fine tune on the track but I'm not sure how dampening, tyre pressures and geometry affect the handling.
Any advice behind the theory and on a good starting point?
Hello Mad Russ.
I personally have to take a back seat on the suspension set-up but many here are well educated on the topic.
The Theoretical is born from the missing elements like wheel/KPI off-set and other areas like sway bars/braces etc....then there is the need to understand what the driver requires the car to do..... in addition i would need to know exactly how adjustable the car is.... seemingly the camber and toe front and rear is catered for but is there any castor adjustment available? Also never be ashamed to image another persons provan positions and re-construct them to suit.
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licence plate caused me greif with the MOT,, was easerly sorted by sticking on the proper ones on top...
de cats can be a problem with emmissions but just takes a good old warm up to sort..
Any probs with the law....concerning the suspect plates
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The most common complaint after front wheel alignment is the end position of the steering wheel this is a visual indication that
1: The workmanship was poor
2: The equipment is inadequate
3: Alignment was never the real problem
4: The manufactured cars axle is miss-aligned
Nearly every alignment test in the World is sold to the customer by the shop based on visual wear on the tyres at the end of there life, inevitable history of past alignment problems would still exist on the face of the tyre, born from this visible wear and potential loss of the new replacements a customer could assume a problem still exists and is easily sold.
Taking 1 to 4 here are my thoughts)-
1: No legal responsibility is required to ascertain the understanding of the technician who sets the direction of your £50.000 (theoretical) car with the new £500 front tyres, most common is a 'drive by' smattering of knowledge that involves undoing of nuts and about ten minutes additional time whilst you pay the bill, (so knowledge maybe why)
2: There are many machines on the market that promise different levels of alignment, most common is 'front wheel alignment' this form is the most damaging and by today's standard only suitable for the horse and cart, can i remind you that the car has 'Four Wheels', (so the equipment maybe why)
3: With the magnitude of problems expressed though the tyres during their life span it would be easy to assume alignment is to blame. Current issues with the Geometry or the cars health in general will cause untold affects toward the tyres and handling, this does not dismiss the fact that 'at the time' the alignment may be incorrect, (so maybe the car is why)
4: There are occasional manufacturing reasons that deceives the operator, this is unusual and depends on equipment, this is most times geometrically undetectable (so maybe the construction is why)
Taking all possibilities into consideration the common denominator is the Thrust Angle the cars true centre that most angles depend on as reference......simple as that!
(click to re-size)Any method that attempts to imagine the front wheels forward position relative the the fixed rear thrust angle will result in the need for the driver to compensate and manufacture a new centre line at the steering wheel, if any adjustments made do not respect the true 'Thrust Angle' then the resulting drive will mean the steering wheel is off-line.
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We all like to take our modifications to the limit but how far 'legally' can you go!
Areas like number plates, tinted glass and exhausts are common modifications, what problems have these caused you with the law or any other areas like MOT.
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......erm .... .........mmmmm........ ........ok you lost me somewhat
This is not deliberate i assure you!
In a forum promoting Geometry a request involving the topic will receive this sort of reply.
Often there will be a need to 'refine' the question since the response could become 'distant' in understanding and of little value!
The Nemesis of Geometry are the variables, the wim forum will dismantle the variables at all levels 'over time', gradual explanation from experts will enforce desire....but again this will take time.
.......for the 1/4...... give me a kick from the above topics (one area) so we can expand....
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the system is bleed by turning from lock to lock untill the required level is shown on the pot
fluid change is done by draining the system, the pump shouldn't be used to empty the system as power steering pumps overheat very quickly if not lubricated by oil
In research i was warned not to have the engine running or turn the steering since the pressure from the pump would overwhelm the passive return feed? and result in everyone covered in oil..
I agree with you and feel the pump should 'purge' the steering under pressure.. any thoughts on this 'don't do it' warning?
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i see your point
ok for starters 1/4 mile races at santa pod
i guess:
low front tyre pressures
hard damping at rear
now would the front damping be better soft or hard
and would camber be worth considering
1/4 mile is a good example for the complexities within Geometry.... and healthy for debate.
Some history first? some...'nay'....many years ago i was asked to consider the Geometrical positions of a 'Funny car' running at the Pod..... 'no worries' i thought
' point forward and 'nail it'.... how wrong i was!Launch delivers lateral and centrifugal forces to the rear tyres and means a Positive/ Negative reply toward the engines rotational inertia... (Mechanical Engineers) would understand this better than me, but the consequence means the rear will definitely 'kick out'... problem #1
Assuming the 'kick can be controlled' then the front obviously needs to be steered during shift, but with the consideration of accelerated down force, and the impact ratio on the front, which is descending in impact but increasing in down force during the 1/4 mile....problem # 2
Front camber/toe needed to be realised from the point the wheels left the ground to all the descending consequences during compression and down force....problem # 3
By # 4 i had a nose bleed.... but i did set the car for a few seasons
Back to the initial question... fwd.... pod....launch.... for debate i would lean toward rear dampers % and front Toe.... 'Traction and Application'
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I'll get me coat
No... but in principle the ABC is a valuable addition for all members that use it! failure to recognise the alternative suggestions will always filter through..... 'that's life'.
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your = you`re
I left my self open for you Bazza .......
Tired.... so is google
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Well done Scarface..... i hope this addition helps make members time here easyer to enjoy.... i for one welcome this because when tired my brain and fingers to not communicate.
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tony
what sort of set up would be best for say :
a front wheel drive car
for maximum traction off the line
ie: tyre pressure
hard /soft damper settings
and again how would this differ from a track setting
its all very well having adjustable dampers, but knowing how to set them would be handy
Very broad question and terribly difficult to answer without being misleading... can we refine things a little.
Launch and actual race serve different purposes.... the Damper settings are dependent on the track as is the Geometry and tyre pressures, for a track day i would need parameters for the type of track and number of bends involved including direction ratio (left-right).... if the car is for used for domestic driving and occasional race days then i would assume there is need to preserve tyre wear since race set-up is hostile to tyre wear through the Geometry positions.
1/4 mile at Santa pod or track day at Silverstone both have very different needs.
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Thanks guys.
Do they set up coilovers there too?
Yes they do... please keep us apprised with events.
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I'm not happy.... this space, is it between the base of the lower coil cup, or the main body of the shaft.
It's the gap between the base of the lower end of the spring and the top part of the inner tyre wall.
I'd get a picture but it's impossible without getting right underneath the car
Found these:
They tell me that a pair of 15mm hubcentric spacers will cure the problem!
You do realise this will change the 'scrub radius' so your new geometry will be void.
Yes - but better than suffering a high speed blowout!
Mike i need a picture (image) of the problem is this posible?
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some places have alignment machines that fit of the rim rather than over the tyre, also i know of a company in hemel hempstead
that has the standard wheel alignment gauges with arm that fit lower down the wheel so more lowered cars can be checkedIndeed you do!..... mind you Clive was concerned when the five Honda S2000 turn up to be set for their race day
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The simple answer is that there is no such thing!
Seeking the perfect set-up is dependent on variables that exceed even the most experienced in the industry, F1 with millions invested each season still cannot deliver 'matter of fact' positions, so what do you do? how can anyone establish the perfect set-up.
First lets look at the manufacture
Geometry within new models tends to be an extension of previous established positions, minor tweaks to accommodate suspension travel, wider tyres and so on is often visible and do fall into the 'safe zone', but attempt to manufacture a completely new Geometry then things can go very wrong, as it did for the Nissan 350Z and the new Peugeot 1002.
So now your modified
Taken from the above the car had recognized Geometric positions and is now modified... suspension, tyres, turbo but now things just don't feel right, well maybe understanding the 'forces' involved within Geometry not just the name of the angles could help.
Toe: exerts no force unless violated to the maximum since the chosen position 'Dynamically' is 0
Camber: exerts a 'conical' force and will want to roll into the lowest point of the imaginary cone, the force adds security to straight line travel and compensates for body roll.... excessive camber will make the steering heavy and lazy (turn out) due to the 'compressive' force generated from the angular position of the imaginary cone.
Castor: exerts a non-reactive longitudinal force assuming the positions over the axle are within manufactured tolerances, on cornering the Castor contributes toward displacement of the steering axis and the position of the 'scrub radius' this force is very important.
KPI/SJI: exerts a very high force toward directional stability, this force is immediately detectable if any attempt is made to deviate from straight line travel... the force is generated by 'inclining' the pin during any steering action, this inclination lifts the vehicle and adds weight on the pin, in reply the equilibrium through the rack will return the steering so the KPI can relax.
How to develop your own positions
First consider your reasons, what do you expect from the car and to what end, is tyre wear an issue, are the modifications cosmetic or deliberate? The four examples shown reflect the most common consequences of modifying a car, in particular lowering, the forces displayed need to be examined in your own example and explored.
It could be easy to assume now that all things 'Geometrical have been covered?
Further reading:-
Scrub radius
Ackermann theory
Delta curve
Bump steer
Thrust angle
Camber curve
Over/under steer
Tyre slip angle/resistance/trail
Lock angles
Cradle symmetry
Memory steer
Castor trail
Cars have never been so complex.........
To be continued:-
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Welcome fella
Probably the closest to you are Drury Lane just up the M62 in Manchester. Look in the main forum index for details.
I have to aggree Drury Lane rate very high on my list..... and it is a very short list!.... Oh and welcome Gee
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Insurance costs the Earth anyway, but if you modify the car, wheels/ sat nav/ suspension and so on have you confessed this to the insurance company? if yes then how much has each additional modification cost you to cover?
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From what I have read most drift cars seem to run with toe in
Indeed at the front this makes sense, but the rear should desire 'over steer' so during weight transfer and drift 'toe out' seems wise... maybe?
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I'm not happy.... this space, is it between the base of the lower coil cup, or the main body of the shaft.
It's the gap between the base of the lower end of the spring and the top part of the inner tyre wall.
I'd get a picture but it's impossible without getting right underneath the car
Found these:
They tell me that a pair of 15mm hubcentric spacers will cure the problem!
You do realise this will change the 'scrub radius' so your new geometry will be void.
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Recently i was made aware of adjustable drop links.... are they any good? and if fitted does this mean there is no need to up-rate the sway bar?
I'm not sure about adjustable drop links.....
When we fitted the coilovers to the MR2 the standard front DL's were way too long. Peter Gidden of sBits made me a set of custom DL's which although are not adjustable they fit perfectly. It's only when the car is lowered that the requirement for shorter DL's is necessary, just uprating to a thicker ARB uses the standard parts.
Interesting.... on the sites main the DL looks as if it is adjustable at the top end, hence the hexagonal locking nut?..... if anyone would know you would.... are there any real benefits from an adjustable drop link in your honest opinion.... could this belay the need to replace the sway bar?
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Much argument has evolved from this topic.. should the wheels be toe'd in or out for the best drift response?
Not front............ rear.
Debate is this....
1: If the rear toe is set negative (out) then during drift three wheels will own the desired direction.
2: If the rear toe is set positive (in) then during weight transfer the outer rear wheel could steer and compliment the drift.
What do you think?
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I'm not happy.... this space, is it between the base of the lower coil cup, or the main body of the shaft.
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Recently i was made aware of adjustable drop links.... are they any good? and if fitted does this mean there is no need to up-rate the sway bar?
Geometry theory
in Geometry
Posted
Taking the Geom by the horns: The camber rear after lowering probably rests between 1 degree 30' to 2 degree's, assuming they are even then i would commit to that position.... personally i desire slight toe out at the rear in the area of 8' per side.
The front is another issue.... Camber i feel needs to be respected at near to stock.... say 1 degree neg, this will lower the Castor slightly by about 30' and reduce the turning radius, but retain the toot... also i would add to the front toe resulting at 10' per side...then test it!