Mushy brakes or what?

**Premature Accelerato** · 22nd April 2012, 18:53

I have a 97 gsxr 750 used for thrashing around the race track. By the end of a track day the front brake lever is coming in almost to the bars. What do I need to do to fix it. So far I have fitted and beded in new disc's and EBC race pads, fitted braided lines, new calipers seals, a new mastercylinder kit and new dot 5 brake fluid. Have bled it at every point till the cows come home but still by the end of the day it is skin of the teeth braking. Any ideas would be appreciated.

**mossy1200** · 22nd April 2012, 18:57

Originally Posted by Premature Accelerato

I have a 97 gsxr 750 used for thrashing around the race track. By the end of a track day the front brake lever is coming in almost to the bars. What do I need to do to fix it. So far I have fitted and beded in new disc's and EBC race pads, fitted braided lines, new calipers seals, a new mastercylinder kit and new dot 5 brake fluid. Have bled it at every point till the cows come home but still by the end of the day it is skin of the teeth braking. Any ideas would be appreciated.

Go round corners faster.

Check the fluid lid breather way on diaphram isnt blocked.

**98tls** · 22nd April 2012, 19:03

What about looking at different calipers mate ie Hayabusa calipers bolted straight on to my 98TLS though to be honest they were rubbish.There must be aftermarket calipers for a GSXR,that or swap out the front end if possible for later model GSXR with radial calipers as i have done.

**FJRider** · 22nd April 2012, 19:12

How much is the amount of wear on the front brake PADS at the end of the day ??? I'm thinking the fluid level in the resovoir will drop as the pads wear down. What pads are you using ???

**DEATH_INC.** · 22nd April 2012, 19:18

The stock setup is ok if it's working properly, I even ran a 14mm master instead of the 16mm on my 99 (better leverage...) and it stayed firm for a full trackday no worries.

**tigertim20** · 22nd April 2012, 20:04

maybe heat fade? what quality pads are you using? do you maybe need to rely on the brakes a bit less?
can only really offer arbitrary resolutions without seeing/testing the bike ourselves!

**Premature Accelerato** · 23rd April 2012, 07:48

The brake pads are EBC race pads, sintered type from memory. Brake fluid level is not dropping and I dont think it is heat fade as surely the lever position would return to normal in between sessions; or is that not the case with heat fade??

**nzspokes** · 23rd April 2012, 08:06

Either your m/cyl is failing or your hoses are ballooning under pressure. I call hoses.

**sinfull** · 23rd April 2012, 08:39

Originally Posted by nzspokes

Either your m/cyl is failing or your hoses are ballooning under pressure. I call hoses.

Not with braided lines, that dot 5 is a pig to get air out of ! Try pulling in your lever and taping it up firmly pulled in over night !

**Premature Accelerato** · 23rd April 2012, 19:35

Braided lines are brand new so doubt its them. Im curious as to why dot 5 is a bitch to get air out of though. Is there a fluid that is better suited to higher temps?. Will try leaving the lever pulled in overnight.

**spanner spinner** · 23rd April 2012, 20:34

Could be a problem with the master cylinder, are both of the feed holes in the master cylinder clear. There is a large hole closest to the lever and a small hole usall 0.5 to 0.7 mm in size closest to the fluid output banjo on the master cylinder. If the small hole is blocked or becoming blocked when the fluid gets hot the brakes can do strange things. If you are interested in a better master cylinder have a look at my listing http://www.trademe.co.nz/motors/moto...-469059293.htm
I have put kits through master cylinders and they still don't work right due to wear in the bore, they are usall ok in normal use but play up when used hard much like yours.

**DEATH_INC.** · 23rd April 2012, 20:58

Originally Posted by sinfull

Not with braided lines, that dot 5 is a pig to get air out of ! Try pulling in your lever and taping it up firmly pulled in over night !

I've seen this recommended a few times....what is it supposed to accomplish? When the lever is in, there is no way for the air to get out....
Did you do all new washers with the lines?
Do you get air out of the system every time you bleed it after the brakes go mushy?

**sinfull** · 23rd April 2012, 21:07

Originally Posted by DEATH_INC.

I've seen this recommended a few times....what is it supposed to accomplish? When the lever is in, there is no way for the air to get out....
Did you do all new washers with the lines?
Do you get air out of the system every time you bleed it after the brakes go mushy?

Haha aparently it lets the air rise upwards back to the res. (sp) Worked for me after putting new braided lines (not me a shop), they couldn't get it to firm up and recomended this ! And by crikey it worked !

**DEATH_INC.** · 23rd April 2012, 21:10

Originally Posted by sinfull

Haha aparently it lets the air rise upwards back to the res. (sp) Worked for me after putting new braided lines (not me a shop), they couldn't get it to firm up and recomended this ! And by crikey it worked !

Yeh, but.... there is nothing in the calipers or brakelines or banjo bolts to stop this anyhow, and with the master compressed, it closes the filler and bleed holes and the fluid/bubbles cannot get out the top.....
I've found that just leaving them sitting overnight after fitting new stuff will often work too.....