The manual recommends using Motul 660, but when comparing technical data sheets of the two products, seem almost identical with same wet boiling point, but almost double price. Can someone explain the difference and why they specify 660?
I found this on the web, interesting comparisons of properties. Personally, I am not sure why people bother with dry results, when wet results are most important considering the brake fluid is quite hydroscopic.
Thanks for the link. After reading it, I don't know why anybody would use anything other than Castrol SRF. It's expensive, I suppose, but its wet boiling point is nearly the same as most other's dry boiling point. I use SRF and change my brake fluid annually now, rather than after every event.
Does anyone have any idea of the total volume of the car's brake system? I had previously converted my Porsche race car from Motul to SRF, but supposedly requires complete flush as they are not compatible fluids. I had been considering SRF also, but with this being my first Radical, I am unclear if the brake fluid system is really stressed like a heavy GT car. SRF is clearly the best, but maybe Motul is more than acceptable with routine changes because calipers may not really overheat the fluid. Guess I will hold on to my SRF for a while longer until I decide.
Dan,
Which car do you have? I run a 1500 SR3 and they are really easy on brakes. While I haven't actually checked temps, I get the feeling that the brakes aren't stressed very much. The SR3's are known to go a long time on brakes. Temps and requirements for brake fluid should be relatively low.
John runs an SR8 if I remember correctly and they may be a little harder on brakes and require better fluid. I'll let him or someone else speak to the SR8 issue.
I'm sticking with the Motul for a couple of reasons. Mainly because it's proven. I normally carry a couple of extra pints with me but if I ever need to borrow fluid and there are other Radicals around the chances are good I'll be able to buy or get some from someone else. I also have things serviced by one of the dealers from time to time and if they top off fluids while going over the car, I know they won't add something other than what I'm using.
Brakes and brake fluid are always one of those items people are usually very opinionated on. Hope my .02 cents helps.
For what it's worth I think the largest brake issue we need help on is a better or alternate source for the bolts that hold the rotor hat to the spindle. They're expensive and made of butter. I can feel them stretch when torqued. We really shouldn't need to replace something like that every time we pull the disk.
@raider89 - Hi Dan, I just completely changed the brake/clutch fluids in my SR3 RSX and used just under 1.5 litres (< 3 x 500ml) for the job including the clutch circuit. Probably could have done it with 1 litre, but there was no point doing it unless I made sure all the old stuff was out. Hope that helps.
Interesting discussion! The SR8s are a bit heavier, and Radical does have an option for 300mm rotors for SR8s (same basic caliper, just a different mount offset). I'd like to think I arrive at a corner with a bit more speed than an SR3, but I doubt that's always true.
Anyway, I use SRF and carry my own spare supply (which I have needed!) from time to time. Last time out my clutch bleeder broke, spilling clutch fluid all over my diffuser and the track. I fixed the bleeder, and was putting in SRF, when I noticed my crew chief (aka my wife) was busy getting the "extra spare" bottle ready for me by opening it and removing the foil seal.
We had a "learning" experience about clutch fluid volumes and the shelf life of brake fluid after opening that day. 🙂
I have a new SR3 XX enroute as we speak, been delayed at UK port a couple times. I suspected Motul would be fine. My Porsche race car would cook Motul at a heavy braking track like COTA, and found that it truly needed SRF. I am planning on sticking with Motul: but still curious of opinions and/or technical argument for 660 versus 600. IMO -the 600 is the same fluid for all practical purposes.
I used to be a hardcore SRF fan, using that exclusively in my Cayman for track use. The high wet boiling point allowed me to flush only once a year with total reliability. However, a while back Castrol had some strange supply issue and SRF was nowhere to be found so I had to switch. I ended up using Brembo HTC 64t and I love it. Subjectively, the pedal feel is better than SRF. I wasn’t sure what to think of the hype, and as noted everyone is very opinionated on this subject but I tried it with an open mind and felt a difference. I’m using it now in the Radical and plan to continue with it.
Yes -- I had the same problem with SRF. I had to use Motul 660 for two events last year. I bought a little extra when SRF came available again.
One more try, understanding the superiority of SRF, does anyone have reason or understanding why Radical wants Motul 660 versus 600? Thanks
@raider89, I don’t know. It might be worth contacting a Radical dealer to see what they say.
