jos
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| posted on 24/1/06 at 10:21 AM |
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Wheel geometry
I'm having fun and games with scrub on my front tyres and it got me thinking
How have other people set up their wheel geometry - camber, (castor I'm leaving alone) & toe.
At the moment its setup by eye. Id be interested to hear before I go to a garage with a geometry rig.
.: Motorsport / motor racing circuit / track wall art Apex Traxs :.
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rusty nuts
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| posted on 24/1/06 at 10:27 AM |
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I have a Dunlop camber/caster gauge that I picked up years ago cheap
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emsfactory
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| posted on 24/1/06 at 10:40 AM |
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I found that my eyes aren't that accurate.
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jos
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| posted on 24/1/06 at 10:55 AM |
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Yeah mine are starting to fail judging by the ammount of scrub the front tyres are getting
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Bob C
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| posted on 24/1/06 at 11:04 AM |
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for starters I've just used a spirit level to set camber (set to zero at full droop) - chassis level & wheel flange vertical. I used a laser
pointer to track it to zero toe (point at lines drawn on a far wall the right distance apart). Mind you the mx5 front has zero scrub so zero toe is
possibly appropriate: cortina uprights have 3/4 mile of scrub so will need a fair amount of toe in - but it's all easy & accurate to do to a
baseline as described above.
Once it's going tweak settings to taste....
cheers
Bob
PS note chassis on stands - susp will be at full droop. At ride height this will give a modicum of negative camber
[Edited on 24/1/06 by Bob C]
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britishtrident
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| posted on 24/1/06 at 11:30 AM |
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Think we need to clarify what you mean by scrub --- you mean the tyres are wearing on the edges or the inside wheel is scrubbing side ways on full
lock.
Also if you could post a couple of pictures of your car -- one taken "square on" from the front the other from above without the nose
cone off.
Castor is easy all you need is a level floor and a spirit level -- ideally a digital one.
Toe-in is more complex without special tools either bough or home made. --- The string method works to a fair degree espeicially with "laser
string".
[Edited on 24/1/06 by britishtrident]
[Edited on 24/1/06 by britishtrident]
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jos
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| posted on 24/1/06 at 11:41 AM |
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I wear the centre section of both front tyres down very quickly
I started with pressures at 20psi and have dropped to 18 & 16 but this hasnt rectified it. I would tkae photos but you wont see any more detail
than by eye - so no help really.
I dont want to change castor at the moment. Ive set them as the factory reccomends and will leave castor at that. I will check the camber is
vertical on full drop but would very much like to know more about the "string method" or "laser strig method"
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britishtrident
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| posted on 24/1/06 at 11:50 AM |
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Yes wearing in the centre generally indicates over inflation ---
What size tyres are you running on the front ? and rim width ?
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jos
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| posted on 24/1/06 at 12:01 PM |
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185 60 13 on 13x6 minilites
Ive got some dodgy brand tyres on the rear and yoko a021's on the front
.: Motorsport / motor racing circuit / track wall art Apex Traxs :.
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britishtrident
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| posted on 24/1/06 at 12:09 PM |
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Don't know the Yokos intimately they are soft but it could be a tyre construction issue --- some tyres have higher crowns than others. You
made need a trye in which the tread has a slightly concave shape when deflated.
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jos
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| posted on 24/1/06 at 02:27 PM |
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Yeah I was thinking along those lines too as the dodgy manufacturer ones on the rear seem quite happy at 20psi
.: Motorsport / motor racing circuit / track wall art Apex Traxs :.
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Hellfire
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| posted on 24/1/06 at 03:53 PM |
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To set front tracking we used two long lengths of angle iron (approx 3m long) bolted to the front hubs and projecting forwards. The tracking was then
adjusted, until the measurements between the two lengths of angle iron, at the nearest and furthermost points, were the same. 
When set up correctly, it transforms the cars handling. Initially, we had set it up 'by eye' (just for SVA - cos we knew we'd have
to adjust the toe to get self-centring) and it handled terribly.
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britishtrident
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| posted on 24/1/06 at 05:17 PM |
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Nowt wrong with that Hellfire done it a few times using a couple of ladders -- not super accurate but a whole lot better than doing it by eye.
Trouble with getting tracking done by tyre fitters and the like is it only as good as the guy doing it.
The laser tracking tool I was toying with building is now in prototype stage -- would have finished before Xmas but life got in the way. Good news is
it seems to work pretty well even when just cobbld together I should have pdf drawings made of it by the end of next week.
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DarrenW
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| posted on 24/1/06 at 05:37 PM |
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quote:
Originally posted by Hellfire
To set front tracking we used two long lengths of angle iron (approx 3m long) bolted to the front hubs and projecting forwards. The tracking was then
adjusted, until the measurements between the two lengths of angle iron, at the nearest and furthermost points, were the same.
When set up correctly, it transforms the cars handling. Initially, we had set it up 'by eye' (just for SVA - cos we knew we'd have
to adjust the toe to get self-centring) and it handled terribly.
Do you have to adjust equal each side, ie measure in relation to the centreline of the chassis?
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Hellfire
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| posted on 24/1/06 at 06:57 PM |
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As long as both measurements are equal between the angle irons, the tracking will be square.
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britishtrident
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| posted on 24/1/06 at 07:56 PM |
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Usual method is to start by centring the steering rack and checking each track rod is the same length.
Then just set the toe-of one wheel relative to the other adjusting both track rods by the same ammount each time.
From the tyre wear perspective the over all toe setting across the axle is the most critical.
If you try setting the toe on each wheel individually one of the problems you run into is establishing exactly where the vehicle centre line lies ---
on production cars this can be very diificult which is one of the reasons I am very sceptical about so called "4 wheel alignment". On
Locost build it is quite easy to make provision for finding the centre line of the chassis at a later date by providing centre line marks front and
rear.
One of the simplest alignment checks you can do is simple find a very straight stretch of quiet road (best if it has a kerb) and find the steering
wheel position where the car run exactly straight then stop the car with wheel in this position (mark the wheel position with a white marker so you
can use it durring alignment checks) get and see if the car look like its sitting exactly parrallel to the kerb.
When you get it back home put the steering wheel back in this position and check if the sterring rack is in its central position and if the track rods
are equal length. If they are you can make use of this mark to centre the sterring next time you set the toe-in.
[Edited on 24/1/06 by britishtrident]
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rusty nuts
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| posted on 24/1/06 at 09:52 PM |
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Having used various tracking equipment over nearly 40 years my personal favorite is the SuperTracker 4 wheel alignment kit.The steering wheel is
centralised, "flags " are placed on rear wheels (scale), laser units are hung on front wheels and turned on . 4 laser beam are used to
check alignment taking readings from front mounted scales and rear flags . Adjustments are then made accordingly . Rear wheel alignment is done by
putting laser units on rear and flags on front , with adjustable rear alignment this is done first. All measurements automatically align all wheels.
Haven't used any more sophisticated systems so cannot comment but suspect variations of this system.
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02GF74
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| posted on 25/1/06 at 09:10 AM |
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quote:
Originally posted by Bob C
for starters I've just used a spirit level to set camber (set to zero at full droop) -
PS note chassis on stands - susp will be at full droop. At ride height this will give a modicum of negative camber
[Edited on 24/1/06 by Bob C]
negative camber - wheels closer together at the top?
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andyharding
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| posted on 25/1/06 at 10:18 AM |
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Jos I have a crude but very effective way of setting toe. My dad invented it. I'll help you do it some time if you want.
For camber just use a set square on the ground...
Are you a Mac user or a retard?
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DarrenW
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| posted on 25/1/06 at 10:57 AM |
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quote:
Originally posted by Hellfire
As long as both measurements are equal between the angle irons, the tracking will be square.
I agree that both measurements being equal will give a combined toe of zero degs but that in itself doesnt guarantee the wheels are pointing dead
ahead. I now understand that if you follow BT's suggestion and find the TDC point of steering wheel where wheels are dead ahead first, check
distance from centre of chassis to TRE is equal on both sides first and then adjust with 3m beams on hubs you can set the toe quite accurately and
equally without specialist gear. Quite simple really.
Q. Does having the car on axle stands affect the toe adjustment (ie will it be different when back on wheels as it is when you set camber at full
droop?)?
Thanks all for the explanations. Sounds quite easy now (even if my explanation doesnt make it sound so!)
Sorry for hijack Jos. Ive just checked my camber, set by eye but measures -1deg on one side and -2.25deg on the other!!! Oops!. Dead easy to adjust
though.
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jos
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| posted on 25/1/06 at 11:35 AM |
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Yes please andy
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britishtrident
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| posted on 25/1/06 at 11:52 AM |
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quote:
Originally posted by DarrenW
snip snip snip
Sorry for hijack Jos. Ive just checked my camber, set by eye but measures -1deg on one side and -2.25deg on the other!!! Oops!. Dead easy to adjust
though.
Important to check the camber in the normally laden state ---- for a Locost this with the driver onboard unless most of your miles are covered 2 up.
Also check the chassis is level transersly in this load condition. If you can get the camber set with 0.5 of a degree of the target figure all will be
well
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Hellfire
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| posted on 25/1/06 at 12:36 PM |
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Apologies Darren, I'd assumed you'd have found the centre of the rack and equalled your track rod ends before attempting to align the
wheels.
Phil
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jos
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| posted on 25/1/06 at 01:47 PM |
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Should I find dead centre of the rack (equal protrusions either end) or steering wheel dead centre (possibly unequal protrusions)
[Edited on 25/1/06 by jos]
.: Motorsport / motor racing circuit / track wall art Apex Traxs :.
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andyharding
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| posted on 25/1/06 at 02:03 PM |
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Wheel centre
Are you a Mac user or a retard?
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