Engine oil & Smart tyres

[Jose M Oliva]

Hello.

We have just come back from 8 hours racing at Paul Ricard and I have a couple of questions/comments to share. It has been the first time we have tried the high compression ratio and Club cam engine.

Question:
We have found the oil to be extremely (and worryingly) thin when hot.  It was a good quality and completely new 20W50. Outside temperature was around 20ºC, so quite decent. Have you experienced this and have any oil suggestion to improve?

Comment:
Due to the unavailability of 145 R 15 Firestones, we decided to fit 145/65 R 15 Vredesteins Quatrac (Smart Fortwo size) instead. We have found the car to be much more predictable when cornering and healthy at limits. Moreover, we noticed that our car was fitted with a fourth gear! If you face supply shortness with 145 R 15, this is an option I would recommend.

Thanks and regards,

José M. Oliva
Madrid (Spain)

[Trevor Williams]

Good to see you finally on the track!!

Engine oil, most here use 15w40

Tyres - never seen of heard of them, but worth looking into considering the price of Firestones or Michelins!!

Trevor

[Chris Yates]

http://ssl.delti.com/cgi-bin/rshop.pl?dsco=110&Cookie=froogle&details=Ordern&typ=R-105427&ranzahl=4&nichtweiter=1

£49 each from mytres.co.uk - look good!

[Trevor Williams]

And they are approved for motorsports!!!! Along with Pirelli P6, Continentals, bridgestones

I have asked Phil to look into some back to back testing, because they are cheaper than what we have available at the moment

[Paul Robertson]

Good to see you finally on the track!!

Engine oil, most here use 15w40 semi synthetic(EFA)

Tyres - never seen of heard of them, but worth looking into considering the price of Firestones or Michelins!!

Trevor

We looked at the tyres but they have a much smaller aspect ratio than the 145/15 and we predicted over 7000rpm at the end of the back straight at snetterton,however if everyone wants to use then we only have to ALL agree is my understanding.

[mark turner Whitwell Motorsport]

 We tested the smart car tyres at croft two years ago, NOT recommended if you want to keep your engine
in one peice! :(

[Chris Yates]

Were they the same manufacturer as these ones at the time?

Perhaps at some point in the future, the regs could be relaxed to allow any 145 65 15 tyre to be used, as long as it's been approved for motorsport..?

[Jose M Oliva]

Difference in development between 145 R 15 and 145/65 R 15 is 7%, so I do not see it as big issue.

[Andrew Bull]

The problem is not the manufacturer, but the tyre aspect ratio.  The firestone F560 are a 145/80/15.  and the michelin is the about the same.  This gives an overall diameter (and final gearing) that suits our engines.  If we utilised a 145/65/15 then we would have a smaller diameter wheel because the aspect ratio is lower.  Firestone is 80% of the 145 mm tyre width.  These smart tyres are only 65% of the 145mm tyre width, thus giving a smaller diameter, and as such would mean that the final gearing will generate higher rpm on the engine.  Acceleration may well be improved, but you will also achieve higher rpm on the longer straights, and as such higher risks of engine destruction.  This is why Mark is saying that Smart car tyres will not be good for your engine. 

They may be better for tight twisty circuits but certainly not good at some of the others with longer straight or where high revs in fourth gear are achieved now.

If we wanted to use tyres that are a lower aspect ratio (or 'profile' as it is also known), but maintain the final gearing, then we would have to look at a 16'' or maybe even 17'' rim.  Although this would mean allowing the use of alternative rims, and the subsequent issues that that may generate would need to be investigated.

I believe there is a working group already looking in to the tyre situation on behalf of the club, and also that the club have placed a large order for Michelins, so watch this space.

Hope this clears up any confusions. 

[Bart van Wijngaarden]

If we wanted to use tyres that are a lower aspect ratio (or 'profile' as it is also known), but maintain the final gearing, then we would have to look at a 16'' or maybe even 17'' rim.  Although this would mean allowing the use of alternative rims, and the subsequent issues that that may generate would need to be investigated.

The club could also relax the gearbox ratio regulations and allow dyane boxes, possibly with 2cv6 diffs, to allow correction of final gearing when using lower profile tyres.

[Derek Coghill]

We're allowed to use lower profile tyres at the moment; it's just that they're narrower as well.

[mark turner Whitwell Motorsport]

Thank's bully for your perfect explanation, here is a little more info! At croft before the braking point at
tower corner engine rev's were just short of 7400, after the back chicane heading down to sunny's in
we had to lift off before the engine expired. We tested the uniroyal 165/65x15 which has the same
diameter as the michelin. All the circuits we drive have at least one section which is too long for those
tyres.