33 replies to this topic

[Spider]

 dot 5.1 fluid

 

DOT 5.1 is generally used for racing cars, it has a high boiling point but is VERY hygroscopic. It's still a Glycol based fluid. You'd really need to change this out about one a month if used in a street car. We changed it out before and after every meeting on the race cars.

 

DOT 5 on the other hand is a Silicon Based Fluid and is NON hygroscopic. It is also generally around 4 to 5 times the price of DOT 4 and DOT 5.1 Fluids.

[nicklouse]

Ok, so whats the difference between dot 4 and dot 5.1 fluid, they are both a similar price. Thanks Martin.

Not much. And some DOT4 fluid exceeds the doc for DOT5.1 but IIRC the 5.1 spec was written for cars with ABS in mind as it has a lower viscosity.

The link earlier covers most of it.

[bikenutmart]

Now im really unsure of what to do!!! Mart.

[Alpenflitzer]

In any case I prefer the DOT 4. This is an acknowledged brake fluid for the Mini. With Dot 4 you can be sure that no corrosion works on your fluid pipe and cylinders.

Edited by Alpenflitzer, 24 December 2015 - 12:43 PM.

[tiger99]

Completely wrong. The pipes and wheel cylinders WILL corrode if DOT4 or DOT 5.1 is used, and as Moke Spider has already explained, DOT 5.1 is UNSAFE for road use unless changed very frequently.

[Spider]

Now im really unsure of what to do!!! Mart.

 

As I've mentioned earlier, I have the silicon based fluid in some of my cars, great stuff, you just need to take different precautions and approach with it, but given it's cost, these days while I agonise over it at the final stages of the builds, I tend to go for the DOT 4 and get my lazy arse in to gear once a year to change it out.

 

My only 'issues' with DOT 5 is it's cost (I'm no tight wad, but it seems over the top in this country) and it's not available everywhere (at least out here). I think Harley Davidson put it in their new Bikes and have been doing this for a very long time. The nearest place where I can get is in fact the Harley shop.

[bikenutmart]

Been offered 2 1 litre bottles,(2 litres) unopened for £30 posted, guessing  1 litre more than enough for a mini brake/clutch system, so will have a spare bottle!!. Thanks for all the pros and cons, never realised it would create so many threads!! Mart.

[carthorse]

I was in the same position with the last car I totally restored years back. (Triumph Spitfire) Since every bit of the brake system was new and I couldn't bear the thought of spilling dot4 on my brand new paint I went with Automec Silicone fuild and had absolutely no problems with it. The car was used for the odd hill climb and sprint and I never had any problems with spongy feeling brakes or indeed any other issue.

I've never used it since simply because I've never put a completely new system on a car and as others have said you can't mix the differing types.

If everything in your system is new you have the luxury of choice, but remember once you've chosen and commissioned the system it's not easy to change your mind without a lot of hassle.

[bikenutmart]

Cheers Carthorse!! Mart.

[Alpenflitzer]

All classic Mini drivers should read the findings and test of Keit Calver on his page:

 

http://www.calverst.com/articlefm.htm

 

 

Happy New Year

[bikenutmart]

Excellent reading!! Mart.

[Joe555]

I am not qualified to comment on whether automec is good or bad but I did read the box while waiting in the shop and it says (both glycol and automec dot5 will work safely together)

[dklawson]

I am not qualified to comment on whether automec is good or bad but I did read the box while waiting in the shop and it says (both glycol and automec dot5 will work safely together)

 

Interestingly, all the information I found on the web says that Automec is made in the USA... but it is NOT sold here.  I searched further online and could NOT find readable pictures of the package.  I did find the link below that talks about Automec.

http://shop.grahamgo...004-64231-p.asp

(By the way... 32 GBP per liter sounds very expensive to me.  Over here I buy Cartel brand DOT-5 for about 2/3 that price).

 

The link posted above (and others) say you can mix DOT-5 with glycol based brake fluids.  That is NOT entirely true.  You can pour DOT-5 in a system that has had DOT-3 or -4 in it.  It will work... for a while... but the fluids do not "mix".  Seals and rubber that have been exposed to DOT-3 or -4 WILL fail prematurely.  Also, the residual glycol fluid in the system will pool in the lines.  In short, mixing the two fluid types is a very bad idea.  

 

Additionally, the link above says that Automec fluid "NEVER" needs to be changed.  That is a highly irresponsible statement.  No fluid is good forever.  The life of DOT-5 fluid might be about 5 to 7 years but it is not infinite.

 

As I mentioned earlier, DOT-5 is great stuff for a collector car.  It is not something I would bother with on a daily driver.  

[Spider]

I'm pretty sure with most of these fluids you can mix them, as they all comply with the same standards, however, if that is done, the benefits of the fluids, in particular, the silicon based one, will have gone.

 

I'd only do that in an emergency type situation.

[bikenutmart]

Anyone tried a silicone fluid called OKO, that's a bit cheaper at £26 a litre. Mart.