All Things Mk5 > Performance Modifications

Ways of reducing the weight of our cars

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fuscobal:
Ok guys, here's the situation I'm in now :

1) 17'' OEM denvers + Kumho V70 R compound on 225/45/17 + R32 front brakes (Carbotech RP2 pads). The weights are 23Kg for the wheel + 21.5Kg for the brakes wich leads to a total of 44.5Kg of unsprung mass

This is the setup I will go to soon :

2) 18" TD pro race 1.2 + Kumho V70 R compound on 225/40/18 + Ap Racing 6pot 362x32 (Carbotech RP2 pads). The weights are 19.5Kg for the wheel + 12Kg for the brakes wich leads to a total of 31.5Kg of unsprung mass

PS1 : The weight saving would be around 13Kg/wheel wich I consider to be huge. From this respect I'm quite sure I will ease my coilover's job of following the track more efficiently and faster. I will also have far better brakes but...I'm not sure the 225/40/18 tires will be as good as 225/45/17

PS2 : I've also changed the arms (TT alloy with adjustable camber) and Hubs (S3 alloy). I've gained 1.2Kg from the arms and 1.5Kg from the hubs + a lot more negative camber (-2.3 as compared to -1 until now). These 2.7Kgs from the arms and hubs brought me more comfort while keeping the fast coilover response ?!?! Since the hub is just a solid piece of metal, I can't see how it can contribute to increasing the comfort other than by it's own reduced mass wich helps the coilover moving more efficiently !

Now, the question comes : Do you estimate the benefits of 13Kgs weight reduction and better brakes will outcome the possible loss of grip from the 18'' as compared to 17'' ? Does anyone know a track test between 17'' and 18'' with the same tire, on the same car ?

the bruce:
I don't know any test comparing 17" and 18" except http://www.kumhomotorsport.pl/prasa/AutoBild_0205.pdf.
But I have discussed this issue to Raeder Motorsport and some
other mates doing motorsports.
So I'm sure there is no loss of grip with the 18". Raeder prefers
225/40 R18 on Golf and A3.
Most of the professional teams currently also use 18".

fuscobal:
Yes, Bruce but it depends what tire they use on 18''. I'm afraid that 225/40/18 hasn't got enough sidewall. Racing cars may use 275/35/18 for ex wich has more sidewall !

the bruce:
No, I have spoken about Golf class touring cars including Scirocco and BMW 1- and 3 series.
Most of them use 240-18 or similar.

I now have found one more review for you:



'White'' ist stock Ambition 17" and ''blue'' is 225/40 R18 Hankook S1 on 8x18,
both with stock suspension.

I currently run 17" on Denvers. I will defintely go for 18" Direzzas when the
Federals are worn.

_Nathan_:
Slicks use a different system of measurement altogether, a 250/640/18 has an identical diameter to a 220/640/18 and a 320/640/18 - the diameter is a measurement rather than a percentage of the width.

I believe the BMW BTCC cars use 235/610/17 and the WTCC cars run 240/610/17.

What do the Seat supacopas run?

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