JASO introduced the MA and MB oil specification to distinguish between friction modified and non friction modified engine oils. Most four-stroke motorcycles with wet clutches need a JASO MA oil. 1)
The JASO MA - MB range:
JASO MA
JASO MB
Dynamic Friction Characteristic Index (DFI)
≥1.45 and <2.5
≥0.5 and <1.45
Static Friction Characteristic Index (SFI)
≥1.15 and <2.5
Stop Time Index (STI)
≥1.55 and <2.5
≥0.5 and <1.55
The JASO MA range is further divided into 2 distinct ranges - JASO MA1 and JASO MA2:
HD doesn't divulge the highly classified weight of their fork oil. Some say type E is equivalent to 10W, some say it's equivalent to 15W oil or more from other manufacturers. Just keep in mind when changing fork oil, you don't want to mix different used oils together with new oil. Drain and clean all previous oil before installing new oil especially if previous oil is not known.
HD has, however, confirmed that type B (0-10W) fork oil is lighter than Type E (5-20). 98) That being said, if you want to stay with HD oils, you can mix B and E for an “X” weight of your choice to tune your forks. All HD fork oils are petroleum based, non-synthetic oils.
If you want to use aftermarket fork oil besides the HD brand, it's best to start with an oil weight that has been proven to work in most general situations. The general preferred weight of fork oil is 15(W) on the XLFORUM in whatever flavor you like. So, start by using 15(W) oil as noted and test it yourself. Depending on your weight, the bike's weight including add-ons and baggage, shocks and etc., you might swap to a lower weight fork oil for softer or a heavier weight fork oil for stiffer fork action.
A lubricant's viscosity varies with temperature. In some areas, the fork oil is already heated up past 100°F by the sun before you start to ride which lowers viscosity and softens the fork action. Likewise, in the winter months, your forks may never reach up to the low end of the viscosity chart below which keeps the viscosity high thus stiffening fork action.
Below is a sample list of alternative fork oils and their published viscosities. Some aftermarket brands include the words “Type E” or “Type B” on their label. Some may say that's to make you feel like your getting the same quality or “Spec” as HD fork oil (especially since there are 26 letters in the alphabet and they chose the same two as HD). After reading through their TDS sheets, it's obvious that different fork oil manufacturers have a different idea of “exactly” what viscosity that HD “B” or “E” actually is. Most brands have their own special additives to condition seals, control foaming, oxidation, rust, corrosion and etc. These additives play their own role in viscosity at certain temperature levels.
Most of the data came from SDS or TDS as noted but that can be misleading also. SDS says one viscosity, TDS says something different, SDS viscosity weights obviously reversed (typo), some TDS sheets look to be a cross or makeshift average between a brand's petro and synth weights, incomplete or missing viscosity SDS data….it's enough to make you realize just how tough the oil business' competition is. It is the intent of this article to fill in all the blanks on the fork oil chart, but what is missing was never written by the company(s) that made the product(s).
Somewhere in some of the oil SDS data you'll find phrases like “The data presented herein is based upon tests and information, which we believe to be reliable.”, 99) “No warranty or representation, express or implied is made as to the accuracy or completeness of the data and information in this data sheet.” 100)
So viscosity really is a 'buyer beware' subject and it's a trial and error to fine tune to your specific needs/ wants/ riding style. The figures on the chart below are subject to change by the respective manufacturers and they are meant as a learning tool of what you are actually buying as opposed to what you are being told you are getting. Check the labels and current SDS/ TDS data before relying on the fact that “this works for the other guy”. Rely on what works best for you regardless of what the data sheets say.
PJ1 Fork Oil (petrol)119) (Highly refined mineral oil (C15-C50) is 70-99% weight) Synthetic anti-seal swell additive added.
Says they are all of High Viscosity Index and Light Red in color. No viscosity weights are published however even in SDS. As a matter of fact PJ1 has the same SDS data sheet (for and that includes) 6 different weights although they publish that they have 8 different weights. Meets or exceeds OEM is published
Brake System
Brake caliper mounting bolt O-rings- Dow Corning 44 grease (“Pin Lube” in parts kit) 120)
O.D. of brake caliper piston (including chamfer), caliper piston bore and I.D. of the installed piston seal - Novaguard silicon grease.
I.D. of upper caliper (threaded) bushing bore, O.D. of threaded bushing, I.D. of upper and lower caliper mounting pin bores - Dow Corning 44 grease (“Pin Lube” in parts kit) 121)
The presence or absence of color is not a safe criteria to distinguish between the different types of brake fluids. The color is added in brake fluid to detect leaks and color does not effect the quality of brake fluid. Since blue and purple sometimes can seem the same color depending on lighting, you could be mixing Dot 5 and DOT (5.1).
Mixing Brake Fluids
Mixing different colors of the same type typically won't hurt the system as long as what you are adding to has not been compromised previously if your just topping off your existing fluid.
You can typically mix DOT 3,4 and 5.1 fluids without damaging your braking system or compromising your existing braking performance. But as nearly every brake fluid manufacturer will state: doing so is not recommended. Why? Mixing good new fluid and old bad fluid means you will retain the bad fluid's performance and change the temperature ratings of your residual fluid. You can't mix any others with Dot 5 fluids. Mixing the others into Dot 5 would cause a meltdown of the rubber parts and/ or a break down of the silicone and possibly clog up the brake lines causing brake failure. Dot 5 into the others may release clogs into the brake lines also leading to brake failure.
If silicone is introduced into an older brake system, the silicone will latch onto the sludge generated by gradual component deterioration and create a gelatin like goop which will attract more crud and eventually plug up metering orifices or cause pistons to stick. If you have already changed to DOT 5, don't compound the problem and change back. You will never get all of the silicone out of your system. Just change the fluid regularly. For those who race using silicone fluid, crack the bleed screws before each racing session to insure that there is no water in the calipers. 132)
DOT 3, DOT 4, DOT 5.1
DOT 3 brake fluids are mixtures of glycols and glycol ethers. DOT 4 contains borate esters in addition to what is in DOT 3. These brake fluids are somewhat similar to automotive anti-freeze (ethylene glycol) and are not a petroleum fluid. Both DOT 3-4 and DOT 5 fluids are compatible with most brake system materials except in the case of some silicone rubber external components such as caliper piston boots 133)
The problem with DOT 3-4 fluids is water absorption. DOT 3-4 glycol based fluids, just like ethylene glycol antifreezes, are readily miscible with water. Long term brake system water content tends to reach a maximum of about 3%, which is readily handled by the corrosion inhibitors in the brake fluid formulation. Since the inhibitors are gradually depleted as they do their job, glycol brake fluid, just like anti-freeze, needs to be changed periodically. 134)
Fluid boiling point DOT 4 glycol based fluid has a higher boiling point (446F) than DOT 3 (401F), and both fluids will exhibit a reduced boiling point as water content increases.135)
DOT 5.1 is also glycol-based and it's major difference to Dot 3 and 4 is it's dry boiling point (minimum 518F).
DOT 5
Dot 5 is of silicone chemistry and not being water miscible, it must rely on the silicone (with some corrosion inhibitors) as a barrier film to control corrosion. Water is not absorbed by silicone as in the case of DOT 3-4-5.1 fluids, and will remain as a separate globule sinking to the lowest point in the brake system, since it is more dense. 136)
Dot 5 in its pure state offers a higher boiling point (500F) however if water got into the system, and a big globule found its way into a caliper, the water would start to boil at 212F causing a vapor lock condition (possible brake failure). DOT 3 fluid with 3% water content would still exhibit a boiling point of 300F. Silicone fluids also exhibit a 3 times greater propensity to dissolve air and other gasses which can lead to a “spongy pedal” and reduced braking at high altitudes. 137)
Brake Fluid Boiling Points
Dry Boiling Point: This is the temperature that your brake fluid will boil when its straight out of the sealed bottle. When there has been effectively no time for it to absorb any moisture. If you are racing on a track, you are most concerned with this value, since the fluid in your lines is likely to be freshly added. 138)
Wet Boiling Point: This is the temperature that your brake fluid will boil when its been inside your braking system for a reasonably long time. How long it takes to get to this saturation point will vary by fluid type, but a good rule of thumb is the higher the dry boiling point, the faster the fluid will saturate (an informal sort of standard is…not always - used by fluid manufacturers: the wet boiling point is the reading taken after fluid has been sitting for one year in your brake lines). If you are riding mainly on the street the wet boiling point is going to be the one you want to pay attention to since the fluid will typically stay in your brake lines for an extended period of time. 139)
SAE Testing Brake Fluid Lubricity
SAE is currently working on modernizing testing and standards for automotive brake fluids. Below are the standards that relate to brake fluid and their corresponding standard number.
J1703- Motor Vehicle Brake Fluid Jul 20, 2015
J1704- Motor Vehicle Brake Fluid Based Upon Glycols, Glycol Ethers and the Corresponding Borates Jul 20, 2015
J1705- Low Water Tolerant Brake Fluids Apr 21, 2014
J1707- Service Maintenance of SAE J1703 and J1704 Brake Fluids in Motor Vehicle Brake Systems