Kelgate Brakes

wally wallen · Posted: Wed Sep 15, 2010 4:57 pm Post subject: Kelgate Brakes

I'm posting this question on the 250 site since the Kelgate brake system is most popular on the superkarts.
I have Kelgate brakes on a F125 laydown. They are great for a few laps, then they get hot and start to fade so bad that the pedal needs to be pumped to get any brakes at all. After the brakes cool down in the pits, the pedal is full and hard again.
I've installed 2 baby NACA ducts on each side in the nose and have two 1 1/4" hoses directing the air at each rotor and caliper, but my driver still lost brakes after 3 or 4 hard laps on a roadrace track, (Lake Afton). It's so bad that my son doesn't want to drive this kart anymore. We have not finished a race this year because of this problem. Lost brakes at HPT leading the Unlimited class at the Nationals too. Mad

Any suggestions from the guys who use this brake system?

Wally

Frank Dawley · Posted: Wed Sep 15, 2010 5:08 pm Post subject:

Wally, What type brake fluid is in the master? Also which Brand brake pads?
_________________
2-G.P. Karts / 2-GFK TM K9B

wally wallen · Posted: Wed Sep 15, 2010 6:29 pm Post subject:

I've been using the Enginetics DOT 5 silicone fluid and several different brands of pads. Using the yellow (hard) pads most of the time.
Should I be using something else?
After we have talked to others using Kelgate, I find that our problem is not unusual, but there must be a way to fix it without changing the complete brake system. I just haven't figured it out, so I'm looking for some help.
Wally

shaun everard · Joined: 28 Feb 2009 Posts: 111

Have you checked all seals in master and the seal in between each half?
Checked for disc run out ie bent? Is fresh fluid???

wally wallen · Posted: Thu Sep 16, 2010 7:55 am Post subject: Re: kelgate brakes

shaun everard · Joined: 28 Feb 2009 Posts: 111

Log shot hear but wheels out of balance/bent causing excessive vibration causing disc to wobble/move pushing the pads back slightly more than required.

Ian Harrison · Posted: Thu Sep 16, 2010 9:35 am Post subject:

Hi Walley, you old fox!!

Just sounds like you are boiling the fluid to me.

Kelgate do recommend Dot 5 Silicone.

Dot 4 Racing brake fluid (we have Putoline here, but I'm sure there is a good US manufacturer) has a boiling point in excess of 300 deg C, but I'm not sure how this affects the Kelgate (nitrile rubber?) 'O'-ring seals. As long as it's synthetic it should be OK (I think Wink

). You would certainly need a full flush out before changing as I know it dosen't mix with the silicone.

We do suffer a little from this towards the end of long hot races and it gets much worse as the pads wear down (more heat transfer) and especially when they have worn at an angle (as they do).

Otherwise, just get some big vents in there and tell your boy to stop braking so much for those corners Wink

We use the soft (green) pads as well and our discs are 162 x 12mm vented fronts and 200 x 20 vented rear.

Of course if it's a laydown you have much less wind resistance to help you slow down from high speed. Shocked

Good Luck

Ian Very Happy

_________________
Ian Harrison
Viper Racing UK
www.viper-racinguk.co.uk
sales@viper-racinguk.co.uk
+44 7984 225 564
+44 161 343 2009
Championship winning Superkart race team 1997-2012

shaun everard · Joined: 28 Feb 2009 Posts: 111

I did have the same problem when by accident I picked up 5.1 fluid and bled all the brakes through after I realised I changed all the seals and refilled with and rebled with EBC dot 5 no more problems.
When you do find out please let us no would be interested to no what you find just in case I have same thing in future.

wally wallen · Posted: Thu Sep 16, 2010 10:42 am Post subject:

Hi Ian,
Yeah, I'm certain we are boiling the fluid. As soon as the brakes cool, they are fine. The DOT 5 fluid I'm using is supposed to have a boiling point of 800+ degrees F, so it SHOULD be good, but does not seem to be. Braking from 140 MPH to a 20 MPH corner does put heat in them, but other brands don't seem to have this problem, at least to this extent.
I had this same problem with Riley's BRC 250 laydown when I had it, so this time I paid Johnny over $500.00 to rebuild the dual master cylinder and all 3 calipers. I'm confident he knows what he is doing since he has been using Kelgate for years and imports and sells Kelgate in the U.S.
Since the brakes are enclosed in the body work on this type of kart and are not really in the air flow, I put a lot of air to them this time with NACA ducts, but they still went away.
It's a lot of work and expense, but if I can't find a answer, I'll just have to change to another brake system.
Wally

alan speyrer · Joined: 22 Apr 2008 Posts: 1329

try some Wilwood brake fluid, EXP 600 plus.

Johnny West · Joined: 03 May 2002 Posts: 1181

Wally,
I don't know why you can not get the heat out of the brake system. As other have mention the fulid must be boiling. Also, your rear calipler is not a kelgate. It is a V-Dot. A good calipler no doubt. Another thing you could look at. See if any of the axles are shifting left to right. If the rear is it will push the pads back in the calipler. Same with the front.

I am sure with all your years of building you checked alinement, nothing is draging.

Softer pads will help. Just go thru them faster.
_________________
Johnny West/West Racing

wally wallen · Posted: Thu Sep 16, 2010 3:08 pm Post subject:

I've checked all that, Johnny. Buddy says that the rear, V Dot brake is working fine and don't seem to be a problem except when he gets on the brakes hard and the fronts are not working.
I have 2 lock collars on each side of the rear axle, so I know it is not moving. I put a lock collar on the front axles next to the hub to keep the axle from going in and out, I pretty sure they are not moving.
I talked to Felton Stroud who bought this kart new and he said he always had to pump the brake one time when he was about to need them and then the brakes were there when he pushed on the pedal.
But, none of this explains the heat problem.
Is there a better DOT 5 silicone brake fluid with a higher boiling point than the Enginetics fluid I've been using??
Wally

shaun everard · Joined: 28 Feb 2009 Posts: 111

Stupid question but does the pedal go down excessively when just pushed at home say when on stand? Is it possible that there is a leak say at the pipe unions?? Or possible long shot but are the front wheels/hubs our of balance causing the pads to vibrate excessively pushing the pistons back into the calipers? Have you tried a different set of front wheels/ tyres??

wally wallen · Posted: Thu Sep 16, 2010 6:40 pm Post subject: Re: kelgate brakes

Allan Litten · Joined: 29 Nov 2006 Posts: 53

Hi Wally,
There seems no doubt that the brakes are generating a high amount of heat and that is causing your problems. The questions that need answering now are:
1. is this amount of heat normal for your situation or it is excessive?
2. Is the pedal pressure excessive for the amount of braking generated or is it normal?
The reasons that I asked these questions are;
If it is right amount of heat generated for the braking requested; if so then getting additional cool air into the brakes is the solution or, isolating the heat from the fluid could be the solution if the amount of air can not be increased easily at this time.
If it is excessive, if so then the pad/discs combination might not be compatible - the co-efficient of friction is too low with this combination - or the situation has change over time; discs have work-harden and reduced the co-efficient of friction.
The answers to these questions will give you the different paths you have to take to find the solution.
Regards
Allan Litten