Originally the car had the 6″x 15″ Teledial Wheels and 195/65/15 Tyres on all 4 corners
These work very well but my goal was to modify and uprate the suspension and handling
so I wanted to try and change the wheel width and possibly the diameter size to see what
the effects were between comfort and compliance and handling……….
I did initially choose a set of wider (7″) Lattice style 924 Turbo 15″ wheels (5×130 PCD)
and also had the front faces machined flat (Previously convex) to lose a little more weight !
These did turn out lighter , and the extra width to (7″) gave the car’s handling a little
more stability, but the tyre profile whilst great for comfort and very good for roadholding
could of been a little better so I wanted to try a lower profile for less camber changes and
better for cornering when pushed hard.
I tried a 16″ Size Wheel, so that the sidewall height went lower from 65% to 55%.
I did try and road test 2 front 16″ Teledial wheels from the early 944 Turbo but they were
3kg heavier each at 19kg each and the car struggled to turn as crisp and sharp as before,
it even began to understeer when pushed, so they drove and handled much worst than
the 15″ wheels, so this was a No Go!
I then found one of the lightest 16″ Wheels Porsche ever had made….. the Cup Wheel
found on the 944 Cabriolet and 968.
These were 2kg lighter than each teledial wheel at (17Kg) but I decided to lighten these wheels
further having seen what a significant effect the weight had on driving and the handling…
If I could match the same weight as a 15″ Wheel, then the best of both worlds was achieved……….
Same weight but with a lower 55% sidewall ratio and a wider rim (7″) all for higher cornering
Step 1 & 2: Machine the centre flat, it looked like it had plenty of meat there and besides this
car would be 23% Lighter so I figured the strength would still be good ! Drill 10 holes for
semi aesthetic reasons / tiny weight loss!
Then Powdercoated in a Primer………Flat all surfaces down to a smooth Billard finish,
then apply high Temp Solvent Wet Paint (A Special TWR Dark Grey / blueish Colour).
Then a trip to a CNC Lathe shop who machine polished (Diamond Cut) the centre and also
a Pin Stripe around the outer Perimeter Rim… Back to the workshops at TWR to Pre-Heat
all 4 Rims to 200 Degrees………… Then a gloss Clear Powder Lacquer was applied and
a final bake. Michelin Pilot Sport 3 Tyres fitted only Approx 10mm wider than standard ..
(205/55/16) all the same size front & rear and Digitally Balanced……….
Each wheel & Tyre only weighs 16Kg !! For example in comparison to the 17″ Cup wheel
which is a popular fitment and “look”on the 944’s and 968 cars they are a staggering
25kg more a set ! The difference in performance is nothing short of astounding……
acceleration, cornering / handling and braking are all massively better with these lightweight wheels
Hill climb / Sprint / Track day – 16″ cups wheels
All 4 Rims are 8″ Wide & the Tyres R888 Toyo 205/55/16 front / 215/50/16 rears
Powdercoated satin / matt grey
8×16 Cups Repaint in a Dark Bronze gloss all 4 fitted with Toyo R888 215/50/16
Further Testing (July 2017)
And with the Intrax Suspension revealed narrower Rim widths and tyres being so much lighter
than the heaviest set of wheels (As above the 8×16’s and R888 track set) made the car
accelerate so much faster on the road from a standstill at from 75mph! The disadvantages
were very small and if anything the advantages outweigh them. The car not only moves faster
on the lighter set (62kg compared to 78kg) but the car’s steering and agility is also quicker
and the cornering has only slightly less stability but no less grip.
I sourced (2) rare 6Jx16 Cup wheels (ET52) which with 195/55/16 Michelin Energy
tyres weigh 15.5kg each inc. paint, air and weights.
(The centre’s have been machined flat like the 7J wheel set)
Sure they don’t “look” like they Fill the arch but this car is about performance improvements
Not All show and no go like some!
I need to find another (2) 6×16″ Cups , as they are hard to find hence for the testing as below
I’ve used (2) D90 6×16″ et52 which are not quite as light (Wheel& Tyre 16kg)
The only slight note was on the 195/55/16 Tyre size the ride comfort and compliance was
more harsh as you expect compared to the 205/55/16, because the sidewall height is smaller.
55% of 195mm is 107.25mm
55% of 205mm is 112.75mm
5.5mm less, so with this I also tested the set of four 6×16″ Rims with the 205/55/16 Tyres.
A 6″ Rim width is 152.4mm and the tyre is 205mm, a difference of 52.6mm or
26.3mm either side. This can sometimes make the handling a bit bouncy and cause more roll
as the relatively narrow Rim moves inside a tyre which is 2″ wider.
But as I expected it restored the ride and compliance quality and give, but also the handling
and cornering was actually better for road use. The extra sidewall height assisted and absorbed
more lumps and bumps in the road, traction was better and braking also great stability.
The contrast from the 8×16 set (All round) with R888 Toyo 215/50/16 to this Set is very
dramatic not a case of it feels a little different, but the car feels substantially quicker to
manoeuvre and accelerate, and cornering, braking and acceleration on the road is also as good.
No doubt on a track the extra grip and stability from wider tyres and wheel rim widths when
pushing far harder would outweigh the loss in performance from the extra weight.
But this proves that Big / heavier or both wheels and wide fat tyres as per the general Hype
are not all they are cracked up to be!
17″ Wheels & Tyres
From a Boxster 986
BBS Sport Classic 7×17 ET55 + 8.5×17 ET50
Michelin Pilot SPort 4 Tyres 215/45/17 & 235/45/17
These were tested (Novemeber 2016) but did not drive as well as the lightweight 16″ Set,
due to their higher resistance from the wider rim and tyre widths but mostly because of
the extra 10Kg of Unsprung and rolling weight…
The car accelerated slower from a standstill and from 80+mph in 5th gear! ,
The cornering was harder to turn the front wheels, the car was not as nimble and the balance had too
much rear grip and more understeer..
The original spare was a 15″ Steel rim and 195/65/15 tyre approx. 19kg
The lightest solution for a usable “get you home” wheel was this Boxster 16″ 6J aluminium wheel with a skinny space saver tyre fitted total around 12Kg.