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This article was first published in 2004.
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Buying aftermarket alloys – it’s probably the single most common vehicle
modification. But if you’ve never done it before you’re sure to be shell-shocked
by the money it’s possible to spend on a set of new alloy wheels – especially if
new tyres are also needed. How much, then? Well, in many cases, try 10-20 per
cent or more of the cost of the entire car! You could be forgiven for thinking:
is this really worth it? And despite all the protestations about visuals, lower
unsprung weight, better brake cooling and a more appropriate wheel size for
bigger tyres, oftentimes it isn’t worth it at all.
But we have a solution at hand - try secondhand alloys! Someone else’s
discards or misfortune can become your benefit.
It’s possible to save up to 75 per cent of the new price by buying secondhand
– a cost benefit that simply cannot be ignored. But it’s not a complete panacea
– if you’re not buying new, you’ll be forced to consider technicalities like
stud pattern, offset, diameter and width... not to mention, wheel construction,
scrub radius and brake clearances.
So let’s take a look into the secondhand wheel market... something that we
recently needed to do when selecting wheels for one of our own cars.
The Guinea Pig
The car for which the new wheels were required was my ’98 Lexus LS400.
Control over the traction (and soon) the stability control electronics is going
to be dovetailed into a mechanical suspension makeover. But with a standard tyre
that has a 60-series profile (they’re 225/60 16), it was always going to be
pushing sh@% up hill to get a great handling improvement without going lower in
profile. (Profile? It’s the percentage of width that the sidewall height is – a
60 per cent profile tyre has a sidewall height 60 per cent of the tyre width.)
Think through the maths and you’ll realise that if you want to keep the
rolling circumference of the tyre near to standard (so keeping your speedo
reading right), going lower in profile means either going much wider in width,
or increasing wheel diameter. I didn’t see a need for immensely wider tyres on
the Lexus so that meant using a larger diameter wheel – say a 17 x 8 or 17 x 9
to replace the current 16 x 8.
However, just going to your local supplier of used alloy wheels (or looking
on the web) for 17 x 8 or 17 x 9 wheels is likely to lead you into all sorts of
problems. So what are they, then?
Stud Pattern
If I was feeling wittier I’m sure I could think up a joke about the phrase
‘stud pattern’. But as I am not, I’ll keep it straight.
Stud pattern refers to the spacing and number of bolts that hold the wheel
onto the hub – or, more precisely, the number and pattern of the studs that
stick out from the wheel hub. There are two specifications – what’s called the
Pitch Circle Diameter (PCD), and the number of studs. The latter is the easier –
it’s just the number of studs/nuts that hold the wheel on. With very few
exceptions it’ll be four, five or six – (The exception? A three-stud wheel isn’t
unheard of in some older Renaults).
The PCD refers to the diameter of an imaginary circle that’s drawn so that it
passes through the middle of all the studs. It’s measured in inches or
millimetres. For example, 4 x 100 refers to a four stud wheel with a PCD of
100mm. A 5 x 114.3 refers to a wheel that has 5 studs and a PCD of 114.3mm.
(114.3mm? That’s a pretty odd size, isn’t it? – although it is less so when you
work out that 114.3mm = 4.5 inches.)
If you don’t get the PCD and stud number correct, the wheel won’t bolt up to
the hub. Period. Without going to enormous expense and difficulty, and dubious
legality (eg welding and re-drilling, or adaptor rings), you cannot use a wheel
that has a PCD and stud number that doesn’t match your car.
So how do you find out what stud pattern your car has? Most tyre and wheel
dealers will know, or be able to easily look it up. A web search under “[your
car name]
stud pattern” or “[your car name]
pitch circle diameter” will often
also find it.
Offset
This probably the hardest to get right in the used alloys market – and is
also the hardest to visualise. Say you’re selecting a wheel that is 8 inches in
width – that’s 203mm wide. Where across that width is the mounting face of the
hub located? Is it half way across the width, or is the hub face located towards
the outer edge of the wheel or the inner edge of the wheel? If the hub face is
half way across, the distance that the hub face is in from the back of the wheel
will be 101.5mm (203 / 2 = 101.5). In this case, the wheel will be said to have
zero offset – the hub mounting face is half way across its width.
That might be easy to understand – but it pretty well never occurs. Instead,
the hub mounting face is either closer to the outer face of the wheel (positive
offset) or closer to the inner edge of the wheel (negative offset). In most
cases, it is closer to the front face of the wheel.
Offset is important because if it is wrong for the application, it can change
the clearances between the tyre/wheel and the suspension members, or the
clearances to the external bodywork – both of which could cause rubbing.
Furthermore, it can also alter the steering geometry (specifically, scrub
radius), which can cause unwanted steering effects.
Finding out the standard offset of your car’s wheels is more difficult than
finding the stud pattern, but again tyre and wheel dealers should know it.
However, you can also measure it yourself. Lay a flat edge across the back of
the wheel (note: the wheel, not the tyre) and then measure the distance between
the straight edge and the hub mounting face. This measurement is called the
backspace. If you also measure the width of the wheel, the formula is: offset =
backspace minus (width/2). So if the wheel is 203mm wide and the backspace is
151mm, from the formula: 151mm – 101 = 50mm offset.
Now it’s easy to come over all knowledgeable and say that if the offset of
your car’s factory wheel is 50mm positive, that’s what your new alloys should
also be. But there are a few practical problems with that.
Firstly, if you’re going for a wheel much wider than standard, the offset
will also have to change, or else you’ll usually end up with the wheel hitting
the suspension. Secondly, more offset can often be better in that you’re
increasing track (the centreline of the wheels are further apart) and that has
positives for stability and handling. And even in the murky worlds of steering
geometry, in some cars increased offset will improve steering feel. Trouble is,
in other cars it will give bad steering and in all cars, increased offset causes
a greater load on the wheel bearings.
Unfortunately, many people selling used wheels won’t have a clue as to what
you’re talking about when you start mentioning offset – let alone changes in
scrub radius and track. The only real fail-safe way of seeing what effect
different offset wheels will have on your car is to drive it. That means a
test-and-try-before-you-buy or at least a refund if the wheels don’t work like
you want.
That can be a struggle to achieve – especially if the wheels don’t have tyres
on them – but take it from us, it’s worth it.
Centre Hole Size
Factory wheels come with a centre hole in the rim that’s a nice snug fit over
the central spigot. This locates the wheel concentrically (ie the centre of the
wheel matches the centre of rotation) and means that the wheel nuts just hold
the wheel on, rather than supporting the complete weight of the car. However,
very many aftermarket (especially secondhand) alloys have a hole that is larger
than the hub. This means that the wheel will fit on – but it also means that the
studs are bearing the car’s corner weight, rather than just holding the wheel
against the hub. It also means that it’s much harder to locate the wheel
centrally, giving rise to vibration at speed. In this situation the best thing
to do is to have spacer rings machined up out of aluminium. These fit over the
hub and within the wheel opening, locating the wheel.
Other Things
As with buying any secondhand goods, you should inspect the wheels very
closely to make sure that they’re in pristine condition. You don’t want to see
dents or nicks; the wheels need to be round (duh – but some aren’t!) and there
shouldn’t be any corrosion present. The mounting holes should also be undamaged
– eg the tapered faces where the nuts bolt-up.
Back to the Guinea Pig
This is sounding like one of those ‘here’s what you do’ type of stories. But
when it’s your own money, it all takes on a different kinda view...
My first move had been to look at what was available from the Lexus factory
for my LS400. Factory alloy wheels have some indisputably huge advantages.
Firstly, they’ll fit. Stud pattern, offset, centre hole size – they’re all
right. Secondly, they’re well made. Factory allows are of very high quality,
something that definitely cannot be said of all the secondhand (and new, for
that matter) alloys that you’ll find at the local shop and advertised on the
web. (How do you know that the wheels that you’re buying were x-rayed for
casting voids before delivery?)
Finally, and it’s a plus for me and perhaps a downer for some of you,
factory wheels are relatively conservative. That means that they probably won’t
visually blow away your mates of today – but it also means that they’ll still
look fine in five years’ time.
So my first move was to price the 18-inch alloys available on the current
model Lexus LS430. They look good and they’d suit my earlier model Lexus fine.
But at over AUD$7000 for a set of four... I don’t think so.... And not even at the
$5000 ‘trade’ price that the friendly Lexus dealership was prepared to offer
them to me at...
Hmmm, what next? I read the classifieds on line, looked at eBay (but who
wants to buy alloy wheels sight unseen?) and then went along to a secondhand
alloy wheel shop. And here’s a really important point. On that day I was only
looking – and that’s just as well! I picked out some alloys (18 x 8, right stud
pattern, didn’t worry about the offset at that stage) and then went home to
think about it. That night I played around with Paint Shop Pro, “fitting” my
chosen style of wheels to my car.
And they looked terrible.
The wheels that had looked so good on the shelf were much too delicate for
the Lexus – it’s a big and heavy looking car. They might’ve looked good in
isolation, but on the car they were wrong, wrong, wrong. What were needed were
much chunkier wheels, visually much heavier than the ones I had been thinking
about.
I thought some more then went back a few days later to the same shop. Armed
with a tape measure. I wanted to measure offsets, tyre circumferences (many of
the wheels had tyres already on them) and diameters. The Lexus is a 5 x 114.3mm
stud pattern, a configuration shared by many cars including the Nissan Skyline
and (as you’d expect) the Toyota Soarer. Also, the Australian Falcon uses the
same stud pattern – interesting, as the alloys fitted to late model Falcons
fulfilled my criteria of visual conservative strength, Original Equipment
quality, and relatively low price.
And there they were – four brand new (well, they looked new) 17 x 8 BA Falcon
XR6/XR8 alloys and their accompanying 235/45 tyres. Take out the Ford oval
centre cap badge and they’d also suit the Lexus LS400. In fact, investigation
proved that the combo had only 1200km on them.
But now was the time to settle...to settle... to think conservatively. First
step: with their 36.5mm offset (cast on the back, as is the case with many
wheels), would they even fit? Sure, the stud pattern was the same, but what
about that offset: 36.5mm versus the Lexus’s 50mm? The store proprietor was
happy to let me fit a pair to the front (the front is always more critical for
clearances - unless you have a four-wheel steer car, I guess) and check how they
worked. Despite the greater offset, they still fitted well within the guards,
and as you’d expect with the changed offset, even with the 10mm greater tyre width (235 versus 225),
there were no inner clearance issues.
But what about the altered scrub radius? The fact that the centre of the
tyre’s contact patch no longer matched the factory geometry? I cajoled the store
proprietor into letting me drive around the block with the new wheels and tyres
on the front. I was looking for undue tramlining (the following by the tyres of
longitudinal ridges in the road), undue self-centring (the steering wheel
unwinding forcefully when driving with some lock applied), and audible scrubbing
(the tyres dragging across the road in very tight cornering – eg a full-lock
U-turn). And, I was also wondering how the drop in profile from 60 to 45 would
affect the ride and harshness.
But all seemed fine. The impact harshness was fractionally higher but in this
short drive, that was all I could detect.
And I also made a phone call. Whiteline Suspension in Sydney will be getting the Lexus
when I have full electronic user-adjustment over the power steering weight,
traction control and stability control – and through the use of the
wrong offset wheels, I didn’t want to be offering a dice loaded against a good
suspension modification outcome. But Jim Gurieff, in the context of a heap of
unanswerable questions (What’s the Lexus LS400 kingpin angle? What the exact
measured scrub radius? – and other stuff like that which I didn’t know),
suggested the wheels and tyres sounded fine. Especially if the car had driven
well with them in place.
So I paid the AUD$1600 (negotiated down from the AUD$1650 asking price) and
took the wheels home. (And new nuts too – that’s another point, as with many
alloys, these wheels needed new nuts if they were to fit on the Lexus.)
The new tyres are a little smaller in diameter than the originals – meaning
that the speedo has changed by about 5 per cent – and I will need to get rings
made up to match the Lexus hubs to the Falcon wheels’ centre holes. In addition,
I’ll also be getting new centre badges made. But in terms of grip (vastly better
than previously) and looks (ditto), at this price for the new wheels and tyres, I
am way ahead...
Conclusion
While there’s certainly plenty of traps to fall into when sourcing secondhand
alloys, the cost benefits that are available make the extra effort well
worthwhile.
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