I've been away from the list for a year.
Now I'm back, and I need to feel grease in my fingers get my nails turned black.
Just purchased a front caliper from a '98 GS500 (Tokico with both pistons the same size)
The one in my '91 has a big and a little piston, and has been developing problems due to its mileage (40.000Mi).
I'm rebuilding the '98 caliper. I've found that it lacks the plastic spacers the older one has. They are between the pads and the pistons.
Is this correct?
I've seen in the photos that Kerry has one of these calipers.
Any issue when the pads became hot?
Welcome back Marc! :thumb:
I have never dealt with a pre-'96 caliper, but here is a "comparison" that I wrangled out of my Haynes manual a couple years ago.
LEFT: 1989 thru 1995
RIGHT: 1996 thru 2003
(http://www.bbburma.net/Scans/Haynes_BrakeCalipers_Front_89-95_vs_96-00.jpg)
I'm not sure what issue you are referring to when the pads get hot. Perhaps "brake fade" on long downhills? I haven't noticed anything myself, although I do try to take it easy on the brakes in those situations.
Quote from: Kerry on July 04, 2006, 10:04:25 AM
RIGHT: 1996 thru 2000 (and possibly all the way to 2006 :dunno_white:)
In 2004 the GS got a 4 piston front caliper. :thumb: :)
Thanks. :bowdown: I edited the post for future readers.
Thanks Kerry!
I have the same drawings in my Clymer manual.
Now I'm sure they are not wrong.
I've had some heat problems in my front brake:
One day we were having a big time with other folks in a curvvy road, then I felt that my front brake was very spongy.
I managed to stop and could see the disk and the caliper smoking. Pads were cooking and caliper dust seals came out of its place.
I think that heat generated in the pads went through the plastic spacers (parts #4 in the left schematic) and heated the pistons (part #5).
Then the liquid boiled and the brake stop operating.
My old disk faded and could not be machined due to thickness and some bending.
I installed a new Nissin disk (ouch very expensive), rebuilt the caliper (new dust-seals, seals and a new steek braided hose), purchased
new brake pads (HH), but it never worked fine.
Now I replaced the caliper with a newer one. It came from a crashed bike that had very few mileage.
But it has no plastic spacers! When pads became hot, pistons will do, too.
Not wanting my brake liquid to boil again.
Thanks.
Marc.
Quote from: marc on July 05, 2006, 02:13:54 AM
I have the same drawings in my Clymer manual.
Now I'm sure they are not wrong.
I just wish they would have oriented both drawings the same way - it's hard to flip those "brain somersaults" back and forth between the two.
I have wondered about the reason(s) for changing the caliper design. Perhaps the plastic "piston insulators" did more insulating than dissipating, and the empty '96+ pistons allow heat to dissipate more efficiently?
Quote from: marc on July 05, 2006, 02:13:54 AMThen the liquid boiled and the brake stop operating.
Thanks for bringing this up. For those who don't know, this is the reason that we (except for Srinath ;) ) use DOT 4 brake fluid rather than DOT3; the DOT 4 spec calls for a higher boiling point.
When the brake fluid gets so hot that it boils, the system contains some amount of easily compressible vapor. When you apply the brake, your effort goes toward compressing the vapor rather than moving the pistons, so the
hydraulic system no longer works as it should.
I have noticed that not all brands of DOT 4 brake fluid are created equal. Some have higher boiling points than others. I suppose that heavy use like
marc describes could overtax the "best" of them (unless the change in caliper design really does make enough of a difference).
Regardless of the brake fluid boiling point, getting the rotor too hot is a definite problem. I remember
gsJack talking about riding twisties with his son and others until his rotor got so hot that it changed color :o (red? blue? I can't remember). This whole "heat thing" is another good reason ... independent of stopping power ... for going with a dual-rotor, dual-caliper setup.
Having said that, the vast majority of us will never get unto "brake-fluid-boiling territory" because of where & how we ride. But it's something to be aware of!
PS - Is this always a "group ride" phenomenon? :dunno_white:
Quote from: Kerry on July 05, 2006, 09:16:04 AM
PS - Is this always a "group ride" phenomenon? :dunno_white:
Yes, I ride as fast as a snail when I drive alone 8).
But guys in my group ride like hell :icon_twisted:. (circuit motorheads :cookoo: )
As for the boiling brake fluid, get some racing brake fluid as it will have a far higher boiling point than anything else you get on the shelves. I used to have problems with vapor lock in my car after some fairly spirited driving (my rotors were glowing blue at this point), but I switched to AP Racing brake fluid and have not had any other problems. Also stay on top of changing the brake fluid regularly, brake fluid is very hydroscopic (attracts water like crazy) and that water build up will lower the boiling point and significantly increase the risk of vapor lock.
I agree with Kerry that the new design may very well to help dissipate the heat, which is far better than trying to insulate it. The rotors are cross-drilled for this very reason: to dissipate heat by providing more surface area to the open air. You may want to look into having your rotors slotted or getting slotted rotors (I don't really know if this is even an option, but if so it would help) Otherwise, if this is a regular issue, you should look into rigging up dual calipers.
Quote from: LimaXray on July 07, 2006, 06:45:22 AMget some racing brake fluid as it will have a far higher boiling point than anything else you get on the shelves. [...] I switched to AP Racing brake fluid and have not had any other problems.
Sources?
I dunno if you can get it in your average Pepboys, maybe a good speed shop can get it. I got it here (http://www.awe-tuning.com/pages/shared/part_detail.cfm?PMaI=1&PMoI=1&PEI=2&PP=a4_18t_brakes.cfm&PPT=Brakes&IL=AP551)
I just took a quick look and it seems they have some better stuff on eBay (http://cgi.ebay.com/ebaymotors/AP-600-Super-600-Race-Brake-Fluid-AP-600-Racing-NEW_W0QQcmdZViewItemQQcategoryZ107067QQihZ002QQitemZ4611165407QQrdZ1QQsspagenameZWD1V) now