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Discussion Starter #1
So i got this Husqvarna SMR 510 and i am trying to build a handbrake setup.
DSC_0406.jpg DSC_0407.jpg DSC_0402.jpg

So the problem is that the braking is very bad. I have tried to pull the lever with both hands and it just barely lock up the tire. My master cylinder is from a Suzuki GSXR 750 and my caliper is the stock one piston brembo. So is my caliper the problem? Do I need a bigger rear caliper. I have bleed the system multiple times and there is no air in the system. There is also pressure when i pull the lever.


Soory for bad ENGLANd
 

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Pretty sure that master cylinder is WAAAAY too big.

It's almost too big for a 4 piston front caliper, let alone a rear.
 

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Discussion Starter #3
I tried using my brembo 13mm master and that caused the same problems. But would it help to upgrade to a 2 or 4 piston rear brake?
 

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Might be silly, but does the foot brake still work right?

Most of the time guys are running dual calipers on the rear?

If it's just as hard with the 13mm master, then it's probably something else is the issue.
 

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Could also be the brake pads. Rear pads are sometimes a less aggressive compound to avoid unintentional lock up of the rear wheel. Maybe see if you can find rear pads with an HH rating.
 

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Discussion Starter #6
The rear brake still works, atleast it can bring my front down when i wheelie. I can try buying some new brake pads. But could my brake line be a problem?
 

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Wair what? U have foot break and hand break to same caliper? If so you are just pumping breakfluid from reservoir to reservoir and thats why your break is weak

Lähetetty minun SM-G935F laitteesta Tapatalkilla
 

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Discussion Starter #8
Wair what? U have foot break and hand break to same caliper? If so you are just pumping breakfluid from reservoir to reservoir and thats why your break is weak

Lähetetty minun SM-G935F laitteesta Tapatalkilla

Sorry for bad picture but the black brake line from the footbrake isnt actually connected to the caliper. Only the blue line coming from the handbrake.
 

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Oki good :) then i think you have air in the system still. Its a pain in the ass to bleed a long system if possible try to force fluid from the caliper with a big suringe. Or take the caliper off ao you get it to be the highest point.

Lähetetty minun SM-G935F laitteesta Tapatalkilla
 

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I have a bleed point on my accosato 19mm. So its easy but i remeber when i uaed scooter master for handbreak

Lähetetty minun SM-G935F laitteesta Tapatalkilla
 

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Discussion Starter #11
Will be getting a syringe asap and if it dosnt work I will buy a new caliper:
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and i will mount it on this:
DSC_0408.jpg
 

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Is the lever "hard"?

That's what I'd expect, as I suspect, as others have said the piston ratio it wrong.

Do you understand the ratio? It's simply like gearing.

If you have a 13mm master, and a single piston caliper with a 13mm piston, it's 1:1 - each mm the MC piston moves, the caliper piston moves 1mm.

If you changed the caliper to one with a 26mm piston. Each mm the MC moved would only move the Claiper piston .5mm. It's "geared down" and the lever will be "softer", and move further for similar effect.

By using a MC designed for 8 pistons on a single piston, you are trying to "take off in 6th gear".
 

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Discussion Starter #13
Is the lever "hard"?

That's what I'd expect, as I suspect, as others have said the piston ratio it wrong.

Do you understand the ratio? It's simply like gearing.

If you have a 13mm master, and a single piston caliper with a 13mm piston, it's 1:1 - each mm the MC piston moves, the caliper piston moves 1mm.

If you changed the caliper to one with a 26mm piston. Each mm the MC moved would only move the Claiper piston .5mm. It's "geared down" and the lever will be "softer", and move further for similar effect.

By using a MC designed for 8 pistons on a single piston, you are trying to "take off in 6th gear".
Pretty much what i was thinking aswell, but would it still be really bad if I got a 3 piston caliper? I could also just use my 13mm master for a new 3 piston caliper and my gsxr master for my front brake. Btw the gsxr master works fine on my front brake.
 

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What diameter are the pistons on the proposed "3 piston" caliper? (I've never seen a 3 piston caliper. 6 piston calipers are common.)
It's all to do with the ratio of the surface area of the MC piston, and the combined surface area of the Caliper pistons.

There is a chart with formulas, and a suggested range. One end of the range for a firm lever, the other for a light, but longer pull. (Search this forum, or google it. Post a link?)

The formula is just the area of a circle. 3.14 x R squared (R is 1/2 the diameter) The "ratio range" would be interesting.

The other thing:
The small diameter rear brake, offers far less leverage. So even with the front caliper/s on the rear it would not be as effective.
(This is why 320mm discs with stock calipers, and an adaptor are much more powerful than the stock MX size discs.)
 

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Will be getting a syringe asap and if it dosnt work I will buy a new caliper:
View attachment 145129
and i will mount it on this:
View attachment 145137
I did mine with the syringe and it works really nice! No air at the first time, just make sure you cover the reservoir so you don't get spill around there. Do it slowly to avoid mess up there.


Sent from my iPhone using Tapatalk
 

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Discussion Starter #16
So I managed to get it working by putting on a bigger caliper. The lever is still really hard but now I can lock up the rear wheel.
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