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Matco WHLB5 brakes

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yodaone

Joined: 09 May 2008
Posts: 10
Location: Pompano Beach,FL

Posted: Wed Sep 17, 2008 10:45 am Post subject: Matco WHLB5 brakes

I have the old Matco WHLB5 brakes which never worked very well on an 8 inch wheel that was made by kitfox. Brakes where leaking and Matco suggested changing the O-rings (2-222 O-ring), which solved the leak. 

They also suggested changing the brake line to 1/8 inch OD brake line for better braking. 



I replaced the brake line to 1/8 inch OD and have noticed a noticeable difference in braking. I would say a 30% increase.  

Below is from Matco: 



It is a matter of brake pressure. The brake is rated at 450 psi. If you are not getting 450 psi to the caliper, you are not getting the rated torque. The issue is usually one of pedal geometry. The early KitFox had two issues. The geometry was low (we recommend at least 2.5 to 1 mechanical advantage). The second is having the master cylinder connect above the pivot point of the toe brake. The result of this is that the mechanical advantage gets worse as the cylinder is stroked. This type of geometry can be made to work as long as the mechanical advantage starts out higher so that it is still at 2.5 to 1 when the cylinder is in the loaded position. The early Kitfox, Avid, and Lancair’s all had this type of geometry. 



There is a SKIDS Technical Comic on our website that talks about pedal geometry and has links to more detail including a discussion of mechanical advantage with drawings. The comic is at http://www.carttonic.com/files/file_download.php?fi_id=39363 



The best way to know for sure is to measure the pressure at the brake with a pressure gauge. You will likely find that you are not getting more than 300 psi or so. It is the equivalent of taking off at 60 percent throttle on the engine. The brake will give more torque above 450 psi but it is less linear above that value. The nylon lines should be fine as long as they have a 450 psi working pressure and at least a 1500 psi burst. Since you also have an issue with the amount of volume used (your pedal geometry worsens with stroke and you will have less stroke with less volume) you may find that smaller diameter lines are helpful. We have recently begun using 1/8 inch OD line for our hand master cylinders as they are low volume systems. It is beneficial for that case. We have also found it easier to bleed a 1/8 line free of air.

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_________________
1991 Kitfox IV 1050LB
Rotax 912UL

Guy Buchanan

Joined: 16 Jul 2006
Posts: 1204
Location: Ramona, CA

Posted: Thu Sep 18, 2008 9:49 am Post subject: Matco WHLB5 brakes

At 11:45 AM 9/17/2008, you wrote:

 	  Quote: 	
		  They also suggested changing the brake line to 1/8 inch OD brake 

line for better braking.



I replaced the brake line to 1/8 inch OD and have noticed a 

noticeable difference in braking. I would say a 30% increase.


	


Hi,

         Would you mind putting your full name in your signature. 

It's a lot more friendly than calling you "yodaone". It would also be 

helpful if you'd include your location.

         On a more technical side, I too have weak brakes, but 

Clevelands. What make/model/diameter tube did you start and end with. 

(I know you ended with 1/8" OD, but what kind of tube?)



Thanks,

Guy Buchanan, Kitfox List Moderator

San Diego, CA

K-IV 1200 / 582-C / Warp / 100% done, thanks mostly to Bob Ducar.

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_________________
Guy Buchanan
Deceased K-IV 1200
A glider pilot too.

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