brakes

[stargazer30]

Hey Guys,

How good are your standard brakes?

I'm getting paranoid as I read that standard brakes are really good but mine don't seem too hot.  I'm comparing them to the focus ST I used to have and the 1.6L petrol Qashqai we have.  Both of them stop in maybe just more than half the distance my MR2 does.  My brakes don't squeel or anything so I think they are okay.

I'm thinking of replacing the disks/pad with something better in the future.

David

[enid_b]

im sure they are fine. with your other two motors, its most likely they feel better as they will be 'over servoed'  meaning that the ford and nissan boffins will have turned up the assistance to help people with lesser driving skills.

more likely to feel like they are on or off as opposed to the nice feel you get with the 2.

if you're not happy, then i would suggest nipping into kwik fit or similar for a free brake test.

however, there is not often such a thing as 'free' as they will find a reason to change them, or miraculously find something else on the car that needs changing.

i would find a big empty space, and try a couple of emergency stops, and get the pedal down as far as you can, dont slam on, just progressively press further and further on the pedal.

oh, and a big point here START AT A NORMAL SPEED AND THEN INCREASE SLOWLY BY 10MPH EACH TIME AND DO A FEW ATTEMPTS. DO NOT, REPEAT DO NOT JUST DO THE FIRST TEST FROM 70MPH!!!!!!!

  s:D s:D

[Goeman]

On mine there's a fair amount of travel on the brake pedel but they always stop the car quickly when you lean on them. Do as advised above. You should be able to trigger your ABS with these emergency stops.

If you still think they're not working properly then check the disks and pads. The back of disks sometimes have heavy pitting and you can't see it due to the splash shield. Stick you finger in if you can't see. Next thing will be checking for a seized calliper. There's probably a better way to do this but i'd jack one end of the car up, get someone to press on the brake pedel (with the engine off) and then see if i could turn the wheels by hand.

If they all seem alright then it's time for a fluid change. Bleed the whole system and put DOT 5.1 in. IF you want to go further then get braided hoses and yellowstuff pads.

(Yellow stuff part numbers are DP41295 for the front and DP41107 for the rear. Most places don't list them for the MR2 but they're cheapest on ebay)

[ChrisGB]

Hey Guys,

How good are your standard brakes?

I'm getting paranoid as I read that standard brakes are really good but mine don't seem too hot.  I'm comparing them to the focus ST I used to have and the 1.6L petrol Qashqai we have.  Both of them stop in maybe just more than half the distance my MR2 does.  My brakes don't squeel or anything so I think they are okay.

I'm thinking of replacing the disks/pad with something better in the future.

David

I have done a brake comparison with a mate in a Focus ST and the MR2 stopped quite a bit quicker (on stock suspension and Bridegestone RE040). With the R888 and modded chassis, it loses speed at an almost unpleasant rate. I would rate them as exceptional in road car terms. As stated above, the MR2 has less servo assistance than some cars, so it may just be you need to press the pedal harder. A good set of stainless braided brake hoses makes a positive difference to on limit feel.

If you are pressing it very hard and not getting the ABS to come on, then you may well have a problem.

Chris

[OlberJ]

If your discs and pads are in good nick then i reckon you need to bleed the system.

It's amazing the difference a good bleed can make.

Also, to point out, don't mix dot x.1 with dot x fluid, it congeals and turns horrible and is a pain in the arse to flush out the system.

[Goeman]

...Also, to point out, don't mix dot x.1 with dot x fluid, it congeals and turns horrible and is a pain in the arse to flush out the system.

You can't mix DOT 4 with DOT 5 because DOT 4 is Poly-glycol based and DOT 5 is silicon based. DOT 5.1 is Poly-glycol based and therefore CAN be mixed with DOT 4. It'll even say that on the bottle.

You should bleed the entire system though because it'll only be as good as the lesser fluid.

[OlberJ]

Aha, sorry bout that. You're quite right.

Dot 3, 4 and 5.1 are poly glycol.

Dot 5 is the silicon based one.

[ChrisGB]

Also, to point out, don't mix dot x.1 with dot x fluid, it congeals and turns horrible and is a pain in the arse to flush out the system.

  s:!: :!: s:!: Ooooh no  s:shock: :shock: s:shock:  

DOT 3, DOT 4 and DOT 5.1 may all be used in the same system and are compatible. You should not mix them because temperature performance will be reduced to the spec of the lowest one in the system, but they are OK to use in the same system mixed (if you need to top up in an emergency) or consecutively. DOT 4 and Super 4 (or 4+) are often very high boiling point fluids with temperature ranges close to 600 F and these are probably best in a car that will see the track.

DOT 5.1 Fluids can also be very high temperature rated, but not quite as high as the DOT 4+ fluids generally. DOT 5.1 Fluid is thinner than DOT 3 and DOT 4 fluid and is optimised for ABS systems as it will recirculate in the ABS valve system quickly.

DOT 3, DOT 4 and DOT 5.1 fluids are all hygroscopic (they absorb water) and contain chemicals to soak up the water and inhibit corrosion. They should be changed at least every 2 years or after track use to prevent corrosion. With time, these brake fluids absorb water and this reduces the temperature at which the fluid (or specifically the water in it) will boil. A 2 year old fill of DOT 4+ may boil at a lower temperature than a fresh fill of DOT 3.

DOT 5 is not compatible with the other fluids. Adding DOT 5 to a system that has previously run or contains  DOT 3, DOT 4 or DOT 5.1 fluid may cause problems. Generally, the DOT 5 fluid will attach itself to products of wear or corrosion in the system and can form a jelly like residue that can cause problems in the system. Further DOT 5 fluids are hydrophobic, (they repel water), so any water that gets into the system will tend to agglomerate (good word for a Sunday eh?) and pool in droplets. If one of these is in your calliper, you have a boiling point of 212 F. Lastly, DOT 5 fluids are Silicone based and as such are highly unlikely to be able to provide the ABS pump and valve system with a suitable level of lubricity (silicone fluids are not generally rated for metal to metal lubrication).

So in short, DOT 3 is what Toyota recommend for the MR2. DOT 4 may be a little more viscous than DOT 3 fluid but plenty on here have run Motul RBF600 without problems. DOT 5.1 is not commented on by Toyota and I see no advantage to running it when stuff like RBF600 is available. DOT 5 is not suitable for use in the MR2.

Hope this helps.

EDIT: Pah! Late to the party  s:oops: :oops: s:oops:  

Chris

[Goeman]

I though that the higher the DOT then the more water had been refined out of the fluid. Therefore less compressable and a higher dry boiling point. Car's will run happily on DOT 3 but as far as i'm concerned the higher the DOT the better.

By the way David. Always use brake fluid from a sealed container. A previously opened cantainer will have absorbed water and be no better than what you have now.

[ChrisGB]

I though that the higher the DOT then the more water had been refined out of the fluid. Therefore less compressable and a higher dry boiling point. Car's will run happily on DOT 3 but as far as i'm concerned the higher the DOT the better.

By the way David. Always use brake fluid from a sealed container. A previously opened cantainer will have absorbed water and be no better than what you have now.

All fluids start dry, but non silicone ones absorb water. I don't think that 5.1 may is more water tolerant, but something like RBF600 has a higher dry and wet boiling point than most 5.1 fluids anyway. If the car is going to get serious use and maintenance, brake fluid will be changed regularly. 5.1 is a lower viscosity fluid for use in newer anti lock systems AFAIK.

Chris

[Goeman]

I've had it in my head that Motul RBF600 was DOT 5.1 for some reason and not DOT 4. Silly me.

Yeah, RBF600 is more than good enough.