brakes for emergency driving

[RedRobin]

You should always use the same DOT level of fluid that the manufacturer specifies. However the DOT specification is quite low which means there are many brake fluids that are listed as DOT4 but would pass DOT5.1 specifications.

I also don't see why DOT5.1 fluid would be less "efficient" in the brake lines of a Mk5 GTi. ESP and ABS have nothing to do with it either.

....I'm not saying he's right but the guy who wrote this usually knows what he's talking about : -

"Lets take the specific AP Racing 5.1 - it has a wet boiling point of 187°C, whereas the genuine VW brake fluid has a wet boiling point of 172°C - so not much difference. Furthermore, the VW fluid is a specific "low viscosity" brake fluid, for use in ABS and ESP systems. The AP 5.1 is not, therefore will make the ABS/ESP slower reacting. Both the AP 5.1 and the genuine VW fluids have a normal service life of two years, but the real killer is the cost. AP 5.1 costs about £40 per litre, whereas the VW stuff retails for £7 per litre, with 10-15% discount just for asking."

"AP are undoubtedly experts with brake calipers, and will no doubt state that any "DOT" fluid will be fine, in their calipers. But the real concern is how the fluid behaves in the really tiny passages in ABS/ESP modulators - and I personally doubt AP have any real concrete expertise. So looking purely at the behaviour of the ABS/ESP, I would be inclined, in this specific instance to listen to the actual car manufacturers.

Again, I could use one of my "longstanding" questions/comments - is 5.1 needed in the massive RS6, or the Veyron? No, the genuine VW fluid is perfectly acceptable."

....I've underlined the part about ESP/ABS.

[shark_90]

I'm not sure who wrote that, but reading it I have a feeling they may have got mixed up a little. DOT5 fluid is silicone based and is more viscous than DOT 4 fluid. DOT5.1 fluid is glycol based (what we would call "normal" brake fluid - like DOT3 and DOT4) but it has the same dry/wet boiling point standards of DOT5 (which are higher than DOT4).

One comment which worried me a fair amount and takes all credit away from this individual's comments is:

"AP are undoubtedly experts with brake calipers, and will no doubt state that any "DOT" fluid will be fine, in their calipers.

As I have just explained, DOT5 fluid is very different to DOT3, DOT4 and DOT5.1 and you can not put DOT5 fluid into a system designed for DOT3, DOT4 or DOT5.1.

As for the final comment:

"Again, I could use one of my "longstanding" questions/comments - is 5.1 needed in the massive RS6, or the Veyron? No, the genuine VW fluid is perfectly acceptable."

In normal driving, that is correct. However put an RS6 on the track and drive it like you stole it, and it wouldn't be long before you're boiling your fluid, especially being automatic. In any case of a car being used outside "normal" parameters then generally an upgrade or modification is required because the standard equipment can't cut it. Brake fluid falls in the same category as remaps, brake changes etc etc, if the fluid isn't up to the task, go for something that meets a higher specification

[shark_90]

And just to clarify - DOT5.1 fluid has a lower cold viscosity requirement (by quite a lot) than DOT4, which means it is actually going to be better and move quicker in brake lines than DOT4.

See here:

[RedRobin]

....Thanks for that info Ben - Much appreciated, buddy!

Yes, I'm inclined to take AP Racing's advice and continue using the DOT 5.1 they supply with and recommend for their big brake kit. Afterall, their Senior Race Engineer with over 30 years experience advised me and fitted the AP's himself - I'm inclined to think he knows his stuff and I'd be stupid to ignore such expertise.

See ya at Castle Combe on the Audi day

[poobarr]

"Am I understanding this correctly?

You use your own car for driving with blues/siren and it's not maintained by the emergency services?

That sounds scary. The police use soft pads but that's fine as their serving regime is top of the line.

Maybe I've misunderstood but currently I'm quite scared that there's people out there with remit to drive on emergency reponse in vehicles possibly not 100% up to the job.

How thorough was the driver training? Was it an hour's talk, a two week pratical or somewhere in between? "

You do understand it correctly. Do you think that emergency service vehicles are somehow different from the ones we drive? Do you think that servicing the majority of these vehicles is over and above manufacturers recommended suggestions? If so you are mistaken.

You know how the Gti handles and I can tell you its far better than almost all other response vehicles. Sure the traffic police have 'performance' cars but regular police have standard cars. Have you driven an astra? Have you driven an ambulance? A fire engine?? Without being patronising the Gti is a far safer car for this kind of work than the majority. I have appropriate insurance and car maintenence regimes.

We undertook a weeks full course of response driving, including exposure to a skid pan. We were under continuous assesment and were required to pass two written exams as well as demonstrate appropriate car control technique, to the standard of roadcraft the police requirement.

In short you shouldn't be scared, I have the same desire as you (and probably more given what I do and see) to stay safe and be safe, but reassured that there are people out there who will give their time and skills to help others.

Speaking for myself I would rather you attended in any old **** heap than not attend at all which I think is the only other option in Scottys point.

For my part I offer my thanks (and just a word of warning make sure the pads dont need to be hot before they work properly, like they did on my Lotus!)

[garcon magnifique]

(and just a word of warning make sure the pads dont need to be hot before they work properly, like they did on my Lotus!)

That's one reason why I'd be wary of fitting performance pads - they often need to be up to temperature to give improved performance and are actually worse when cold. That's not something that fits ideally with response driving.

[shark_90]

I can recommend Ferodo DS2500's. Pretty good when cold (i.e. no worse than OEM) and absolutely stonking when hot.

[RedRobin]

I can recommend Ferodo DS2500's. Pretty good when cold (i.e. no worse than OEM) and absolutely stonking when hot.

....That's been exactly my experience of DS2500's too (road use, not track).