NME Tarmac specification suspension information

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campbellju

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Introduction
==========

Below are the specifications obtained from a fellow member for the NME Group A specification Pulsar used for Tarmac stages.

This is a work in progress. I will try to add some comments for explanation and a few blanks for further information.
 

campbellju

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Wheels & Tyres
============

8.5" x 16" Wheel

225/625/16 Semi slick tyre - Brand to be confirmed


Comment:
This is a large tyre to fit on the GtiR without rubbing issues.

As a reference the nearest road tyre size equivalent would be a 225/50/16

The standard wheel tyre combination (195/50/15) has a diameter of 576mm. If you were to fit the NME spec tyres on a standard car and solve the rubbing issues you'd find they added 24mm to the ride height.
 
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campbellju

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Geometry
========

Camber front: -4.25 deg
Camber rear : -2.2 deg
Camber adjusted using slotted hole on strut

Toe front: 2mm in (roughly 0.18 deg in)
Toe rear: 2mm in (roughly 0.18 deg in)

caster front: 2 deg
caster rear: 5 deg

Comment:
Given the locations of the suspension components are quite close to standard, I expect the high level of camber on the front is a result of running sticky tyres in the dry and the GtiR's poor camber compensation under compression.

The rear camber of around 50% the front makes sense and is a reasonable rule of thumb for our cars. The toe in at the rear I can also understand as nowadays I prefer the stability it brings when deliberately unsettling the car. The toe in at the front appears strange at first. Given the relatively high amount of negative camber on the front, I assume this is to help with stability under acceleration and braking. The Springs and roll bars are relatively soft so turning may not have been a problem.

I also wonder if it was set higher than normal to compensate for bumpsteer at the front? There is some information on the car's bumpsteer compensation but given the travel on the suspension this might have been insufficient?
 
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campbellju

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Anti Roll Bars
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Front: 24mm solid, un adjustable
Rear: 19mm solid, adjustable

Comment:

For those who don't realise a hollow bar is less stiff than a solid bar.

The standard bars are
Front: 28mm solid, non-adjustable
Rear: 15mm solid, non-adjustable

I was initially surprised the bars aren't adjustable but on reflection I expect this is because for NME it was just as easy to change the entire bar.

As the NME car uses roughly the same mounting points as the standard car then we can be pretty certain the NME car uses a softer front and a stiffer rear ARB than standard.
 
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campbellju

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Ride Height
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The wheel to fender gap is specified as 50mm all round.

Comment:
We know the tyre size is 625mm diameter

On their own, the wheels will RAISE the ride height of the body by +24mm all round! We can calculate the NME car equates to 362mm axle to arch all round.

The standard ride height from the axle to the arch is F365mm, R375mm.

So the location of the suspension geometry, prior to the other small changes are the front is effectively the same as standard and the rear has been lowered -10mm.

When you factor in the wheels again, the overall ride height of the car compared to standard is Front +24mm, rear +14mm
 
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campbellju

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Control arms
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Front:
Aluminimum Front wishbone, appears similar in design to standard though likely stiffer and lighter
Front mounting point of wishbone 10mm lower
Rear mounting point of wishbone uses jointed setup to adjust position. (Similar to the whiteline anti dive kit)

Rear:
Standard position
Rose jointed track control arms


Comment:
 
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campbellju

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Springs and Dampers
===============
Proflex inverted coil over suspension with separate damping oil canisters running 10 bar nitrogen on gas bladder, compression and rebound adjustable, along with adjustable platform springs, these are also fully adjustable if striped for high and low speed damping too.


Bump stops 88mm neoprene down to 45mm depending on driver.

Eibach springs

The coilovers use a main and tender spring. Not to be confused with using a main and helper spring as seen on other cheaper coilovers. A helper spring effectively has zero rate and keeps your main spring in place under extension.

Use of a tender spring gives you a dual rate to manage.

Tender Spring
Front: 6kg/mm, 100mm length
Rear: 5kg/mm, 70mm length

Main spring
Front: 10kg/mm, 200mm length
Rear: 6kg/mm, 250mm length


Comment:
Long story short, if these are converted into CPM (Cycles Per Minute) and then given as a ratio front to back you get the relative stiffness of the springs in relation to the car. The following % are the front CPM rate compared to the rear. In the first example, the front Tender Spring CPM is 82% of the rear meaning in simple terms it's softer.

NME Tender Spring 82%
NME Main Spring 97%

OEM Standard Spring 92%

So the tender springs are not only improving the ride (High speed bump) but also aiding with turn in as an 82% ratio will help to throw weight over the front tyres. Once the tender springs are compressed and the main springs come into play, the car will have a more neutral spring bias.

The transition needs some further maths though I expect the free lengths are quite deliberate and the transition is smooth.

End result is a compliant ride that resists roll in corners, very clever
 
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campbellju

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Brakes
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Ap 6 pot calipers front, brembo 4 pot rear.
Discs Front 332mm
Discs Rear 278mm

pads

Carbon metallic f/r
 

campbellju

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Track
=====

5mm spacers all round

Comment:
Total track unconfirmed as wheel offset may be slightly different. Working assumption is the 5mm spacer was used when running in tarmac spec to increase overall track and help with rubbing issues.
 

The Doc

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Just a quick note to anyone copying this onto other forums, theft of intellectual property is actually illegal and if you want to persist in doing so then all the secrets in the world can also come out.
 
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