Chossing Brakes for My Beloved STI
 

As you may be aware from a earlier thread I'm looking to get me breaks done, just the fronts at the moment anyways.

I'm most likely going to buy Mintex pads and go for standard discs. But have you guys brought any grooved discs of Ebay or should I say Fleabay.

What are your opinions on the matter. I use the car as a daily runabout to work from Brid to Driffield. I don't thrash the car I havve my occasional fun with the car.

So there for I think I wouldn't get the full potential from using expensive really good discs and pads. I know I need a decent set up to stop my car.

Also While I'm at it what does 4 pot and 2 pots mean.

I've a import MY99 STI V5 I think these should be 4 pot fronts and two pot rear not sure.

Thanks guys

'Pots' refers to the number of pistons squeezing the pad against the disk. Id consider talking to Ian Godney @ Godspeed, but I wouldnt consider eBay. Also, theyre brakes, not breaks.

Simon

Why does your STI need a break - are you not getting on?

I've got Mintex 1144s on mine. IMHO they're better for day-to-day use than the 1155s. Much better bite from cold. Had grooved disks when I bought the car, so can't comment there.

Braided hoses are worth it if you're changing the fluid and get the free play in the pedal adjusted to a minimum. This won't give you more stopping power, but will help feel and your confidence.

You could set up some wind breaks in front of it to slow it down some, but that's not as effective as a set of brakes attached to the actual car itself.

I think that it will give you more stopping power, beyond the knee-point. You have to fit them all round of course.....

Go for a decent setup from Godspeed, good prices and great products!

Just to help ....

4 pot subaru caliper
http://i246.photobucket.com/albums/g...autoadjust.jpg


2 pot subaru (rear) caliper
http://i246.photobucket.com/albums/g...LCADJNVCIC.jpg

1 pot sliding (rear) caliper
http://i246.photobucket.com/albums/g...c/untitled.jpg


id recommend ian godney too for brakes ... even if you're not going for the full set up with new calipers he can help with and recommend pads, brake lines, fluid and replacement discs

Im sure that he realises his spelling failure by now.....

As stated, standard disks are fine for road use with some new uprated pads, braided hoses and new 5.1 fluid. I used to have Pagid on my classic, very good.

Yup I've realised my spelling error. I must of been imagineing what breaks are like at work.

Well so far I'm going to try Pagids with standard discs. Will buy some braided hose lines to. But my garage said there's no point in me buying 5.1 fluid as I don't use it for track. Not sure if they are right.

What you lot think.

Get the Godspeed 335 MM conversion kit: look here

:lol1: kit kat

Have a chat with alyn :)

AS Performance - Rally Motorsport Specialists

Performance friction stuff not bad :)

Shaun

Performance Friction are superb; but theyre expensive. Pagid are excellent too, and a little less expensive.

If you are going to do the lines then you might aswell spend another £20/£30 or so and uprate the fluid to 5.1. Just my opinion and im sure i read it it years ago somewhere but the standard 4 pot setup on classic imprezas generates alot of heat so better fluid is only a good thing ... and with time brake fluid absorbs moisture so boiling temps drop quite alot so better to start with 5.1 as over time it will naturally deteriorate

Althouth a good quality dot4 typically has less compressability than a dot 5.1

Wet boiling temps are combatted by frequent fluid changes, max 2 years. Although I do it yearly (I have a pressurised auto-bleeder, so its a doddle).

agree with that ... either a good dot 4 or a 5.1 should be more than enough and in an ideal world annual brake fluid changes are best but realistically its a bit longer

Can you expand on this: bearing in mind that a liquid can not be compressed?

Simon

Simon

Liquids can be compressed :D

Compressibility of Liquids

if temps increase then the fluid can boil or disolved gases can be released and the resultant gas is easy to compress. However at normal temps I would guess the expansion of the pipes and flexible linkages would be the biggest problem LOL


Shaun

Shaun

Mmmmmm; youve taken me a little too literally there (or maybe I was too lazy :D).....

I realise that brake fluid can be compressed due to its being hygrospopic and the water boiling. What I was trying to find out about was DOT5 fluids being more 'compressable' than DOT4 types; becasue I was under the impression that it wasnt as susceptible to water contamination?

I can't imagine there is much difference in compressability between the two. I thought the Dot5 had a higher boiling / vapourisation temp so the brakes / lines / fluids could stand higher temps..............like track work :)

Shaun

Me too: thats why I was confused by Ali's assertion that DOT4 was superior.

my understanding is that depending on manufacturer and quality some dot 4 can out perform some dot 5.1 and vice versa. The difference between them is in the chemical structure of the fluid. Dot 5 is silicone based and totally different and you can not change from dot3,4,5.1 to dot 5 or vice versa.

Thats just what i've learnt from the net etc but im no pro so cant explain the ins and outs of it

Thats pretty much along my findings too :thumb:

I'd like to post a link to specific info, but my googling results have been somewhat disappointing. Which kind of makes it difficult. :(

Anyway, Glycol fluids even being vastly superior in "pedal feel" to silicone fluids, do still have have a degree of compressibility. DOT standards do not strictly specify any exact specification to the compressibility of a brake fluid. However, they are compressible; partly due to its composition (with exception to DOT5, they are all poly-glycol based, that contain different hydrocarbons and alkanes; which include oxides and ethylenes of glycol), and partly due to air dissolved and in suspension (note this is different to air which can be bled out).

Now, there is a tendency that a glycol fluid to be slightly more compressible due to its composistion and dissolved air. However, brands differ, and thats the problem (like oils). Air dissolved in situ (this is not air in system which can be bled), is a factor that affects its compressibility. Again of which DOT standards do not specify. So, with that in mind its quite valid to have one brand of DOT4 that has a composition and less dissolved air, which give it less compressibility than another brand's DOT5.1 fluid.

The point being DOT standards mainly focus on boiling points, viscosity and the compatibility with the vehicle's braking system. The wet boiling points of BOTH DOT 5.1 AND DOT4 being ALOT less than their respective dry boiling points. If one wants optimum brake performance, they should not be relying on wet boiling points of either fluid standard, as the boiling points of both fluids degrades significantly over time.

Generally speaking, the wet boiling point is achieved after 2 years. And the dry boiling points of both Dot 5.1 and Dot 4 aren't that different. Hence the advice to not focus on the DOT standard alone (except for DOT5 silicone; which you should NOT use in a performance car), as the onus is to change it more often, be it DOT 4 or Dot 5.1, as this will maintain its dry boiling point.

So, given both DOT 5.1 and DOT 4 have significantly degraded wet boiling points. You have to ask yourself: What makes a DOT5.1 fluid better than a branded DOT4? Equally as such, what makes Motul branded race DOT4 fluid any superior to a humdrum Halfords branded DOT4? They both conform to the same DOT standard. But both sell for vastly different prices. Whats the difference? (barring the price and the label). ;)

Point being: DOT standard isn't the end all standard to dictate if one brake fluid is better than another. Whilst one DOT5.1 has better boiling points, a good quality DOT 4 could give better pedal feel; Simply because the DOT standard is does not strictly cover those factors.

Put it this way: A fresh DOT3 fluid has a better boiling point than a 2 year old DOT5.1 fluid. So whats best? Answer: Replace the fluid before it degrades! :thumb:

Glycol....as in spitfire coolant :)

isn't it ethane-1,2-diol

ethylene glycol (chemical compound) -- Britannica Online Encyclopedia

Shaun