track attack info and question?!

Guest · Jul 20, 2004

Just finished a track day a brands hatch, a good day's entertainment. tyres blistered up reasonably though !! I had front tyres at 28psi and rears at 30psi hot (42 and 52 degs respectively).

One problem i encountered thought was the brake fluid tank overflow kept spitting fluid out. I presume this is because of either:-

a) fluid getting to hot or
b) high corner speeds forcing it out - its on the left side of the resevoir and mainly right hand corners at brands

any hints on keeping fluid in the system? or has anyone else had the same problem?

mark

Guest · Jul 20, 2004

Re Tyres: Limit yourself to shorter sessions or give the tyres a break in the middle of the session with cool down lap. You should feel the tyres heating up, "going off" and reducing grip levels before they blister. Its an exercise in self restraint [

] or try running tyres with less tread or bigger tread blocks. Two reasons, first heat is caused (to a large extent but not exclusively) by the twisting and bending of the tread blocks - less tread depth reduces this. Secondly, less tread will dissipate heat more effectively. Alternatively get a set of r-compounds which despite softer tread, last much better for track work and are acceptable for summer driving if you are careful in the rain.

BTW, what tyres were they? Got any pictures? Any other relevant info? Like, maybe you let Tiff Needell drive your car for an hour [

] I am surprised with those relatively low hot temps you had blistering.

Re brake fluid: I think your reservoir is over filled. Use a syringe to take a few cc's out.

Otherwise, how was it? Its always good to here about others' success stories.

HTH
Richard

Guest · Jul 20, 2004

tyres were mitchlin pilot sx, and to be quite honest i did push them quite hard for the 10 laps I was getting before the low fluid light on the brake res was coming on.

The fluid was definitely coming out for a reason other than over filling , otherwise the low light would not have come on . bare in mind that it would still drip out of the overflow whilst in the pit garage after the session. expansion perhaps???? too hot ???

I don't know . is it worth upgrading my dot 4 fluid. I already have a set of '89 turbo 4 pot calipers to put on , not sure what disks will fit to my current 'standard' hubs though. would the brake change and upgrade of fluid stop the overflow problem??

m

911sse · Jul 21, 2004

Upgrade to a fully synthetic brake fluid!

Castrol or Shell. Makes the difference!

Guest · Jul 21, 2004

ORIGINAL: markrnorton

tyres were mitchlin pilot sx, and to be quite honest i did push them quite hard for the 10 laps I was getting before the low fluid light on the brake res was coming on.

The fluid was definitely coming out for a reason other than over filling , otherwise the low light would not have come on . bare in mind that it would still drip out of the overflow whilst in the pit garage after the session. expansion perhaps???? too hot ???

I don't know . is it worth upgrading my dot 4 fluid. I already have a set of '89 turbo 4 pot calipers to put on , not sure what disks will fit to my current 'standard' hubs though. would the brake change and upgrade of fluid stop the overflow problem??

m

Fascinating, I would ask a specialist about the fluid, as its not a problem I have heard of.

The Turbo calipers need to be used with Turbo discs. The rear turbo discs will bolt right on over existing handbrake hardware but the front discs have the wrong offsets. You need a zero offset mounting bell and Coleman, Brembo etc discs. Its expensive. I think 9M have this kit on their website or try VCI in the US (who definitely have all the info you need on their site). Turbo calipers cannot be used on 3.2 discs as they are designed for 28/32mm thick discs not Carrera 24mm thick discs.

Richard

Guest · Jul 21, 2004

does that mean i could use the turbo front brake discs and buy a suitable mounting bell elsewhere or would you recommend just buying bell and disk from a particular specialist??

m

Guest · Jul 22, 2004

no, you cannot use Turbo front discs (other than the NLA 78/79 discs that had a separate mounting bell). You have to get a two-piece disc and mounting bell with zero offset. See below (although it has a 993(?) caliper).

Search for "VCI + brakes" on google and you will get to the VCI site and all will be clear.

RB

Guest · Jul 22, 2004

thanks richard, I think that makes things clearer !

I did , i'm sure, read somewhere that 928 gt disks would fit. have you or anybody else reading this heard this one, or am i going nuts!!

M

zwhitea · Jul 22, 2004

While we are on the subject of breaking, has anyone ever been on contact with Hi Spec Motorsport..

http://www.hispecmotorsport.co.uk

I know the stuff they produce for other cars is quality... and they are always looking for new projects..

Guest · Jul 25, 2004

ORIGINAL: zwhitea

While we are on the subject of breaking, has anyone ever been on contact with Hi Spec Motorsport..

http://www.hispecmotorsport.co.uk

I know the stuff they produce for other cars is quality... and they are always looking for new projects..

The thing is, that Porsche produces such great brakes on the later cars that you can mix and match various Porsche components together with relative bolt on ease, so its not worth reinventing the wheel and building a big brake kit from scratch. You also have to fit it under a 16 inch Fuchs wheel unless you want new wheels as well.

If anyone wants to do a cheap(ish) upgrade, I will be posting all the info in the next couple of weeks. If 944T/964 size brakes sound about right then just hold your breath and I will share all the info. The hard part about upgrading brakes is working out what fits. If you are not an engineer you have to dig deep to find someone who has actually done it and can help you out otherwise you pay someone else to do all the R&D time. Ask me how I know....

Richard

Guest · Jul 26, 2004

Richard,

i have 17" wheels on the car at present, so caliper clearance isn't really an issue. And strangely enough I am a mechanical engineer by trade!!.

I could put in the time and effort sourcing disk/bell configurations but I thought I'd try the forum first to see if somebody out there has done it before!!!

however, 9m do a disk/bell kit for £595. But then again, if someone has a suggestion on a suitable disk, i could investigate machining of the items to fit.

thanks for help so far to all

Mark

Guest · Jul 27, 2004

The 9M kit is exactly what you want. Use this with Turbo calipers and standard 930 rear discs and you are good to go. You will also need the bigger 930 master cylinder. Given you have the calipers, you may be able to do the rest of it for not much more than £1,000.

930 brakes are ample for a 3.2 - I know 600hp Turbos and 350hp NA cars racing with Turbo brakes without issue - and they also have the benefit of fitting under all applicable 15 or 16 inch Porsche wheels. Later 993 front calipers and 965 rears are a nicer option (differential piston sizing and they are stiffer and lighter with bigger pads) but there is no need to look beyond the Turbo calipers if you already have them.

Richard

Guest · Jul 27, 2004

richard

do i definitely need the new master cylinder?, does this just shorten the pedal travel? or do you need it because the 4 pot calipers give to much pedal travel with the standard master cylinder?

mark

Guest · Jul 28, 2004

You have to displace more fluid because the total piston bore is much larger. So, yes the pedal travel is longer if you do not. Conventional wisdom says you *must* change but I know of at least one car that did not.