Replacing master cylinder
HDF Community Team
Joined: Nov 2012
Posts: 6,189
Likes: 2,419
From: USA
What that Wilwood caliper is, as well the pads and rotor, matters a whole lot. Until the op tells us, were all more or less shooting from the hip.
A well designed kit will keep comparable caliper piston area in order to work properly with the oem master cylinder.
Perhaps its a home made bodge. Perhaps its a poorly designed kit. Perhaps a caliper piston is sticking. Could even be an internally failed hose.
Dunno, and the op isnt telling us anything we need to know.
Thread Starter
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Road Warrior
Joined: Aug 2020
Posts: 1,284
Likes: 2,089
From: NC
The Wilwood is designed for this bike (I proposed them a question last night if a 9/16 will work with this caliper), however the original set up is dual disc, so the Wilwood is comparable to the stock caliper (also replace line with a braided stainless unit) , the caliper works better than the stock unit that was on the bike, hell the Fintstone method would be better than that, and I know that a single disc will not have the performance that dual have, that is not the question, and I have ridden bikes for 40+ years and never had a lever that was as hard to pull and almost 0 travel, may try a "reduced" reach lever.
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Road Warrior
Joined: Aug 2020
Posts: 1,284
Likes: 2,089
From: NC
Pretty much, other than it is red. link to caliper https://www.wilwood.com/calipers/Cal...%20%20&appid=0
HDF Community Team
Joined: Nov 2012
Posts: 6,189
Likes: 2,419
From: USA
Ok, that helps.
So your bike originally had those two little calipers, and now it has one bigger Wilwood four piston caliper, right?
Going with my magically calibrated eyeballs, that should work about equally with regards to fluid flow and clamping force.
So something doesnt seem to be physically working right.
Have you pulled the caliper off the fork, squeezed the lever, and watched the pistons move? Making sure all four pistons are indeed moving freely?
Your description sounds a lot like a partially frozen caliper, not a hydraulic mismatch, to me.
So your bike originally had those two little calipers, and now it has one bigger Wilwood four piston caliper, right?
Going with my magically calibrated eyeballs, that should work about equally with regards to fluid flow and clamping force.
So something doesnt seem to be physically working right.
Have you pulled the caliper off the fork, squeezed the lever, and watched the pistons move? Making sure all four pistons are indeed moving freely?
Your description sounds a lot like a partially frozen caliper, not a hydraulic mismatch, to me.
Seasoned HDF Member
Joined: Dec 2005
Posts: 19,894
Likes: 8,002
From: poway
I can't find the piston size for stock FLHT caliper but suspect that they are between 1 1/2 to 1 3/4 pistons. Anybody got one they can measure? The effective area of that is in the range of 1.76 to 2.41 square inches. My bet is that it's on the short side to the middle.
https://www.wilwood.com/calipers/Cal...%20%20&appid=0
The Wilwood has an effective area of 2.46 sq in.. They only make one caliper size. So the effective area for FLH will be 3.52 to 4.81 inches for 2 calipers. Comparing the total pad pressure between 1 Wilwood and 2 Stock calipers is reduced to 70% to 51% depending on the FLH caliper piston diameter. Kind means you are going to have to squeeze the lever 30 to 49% harder to get the same force on the pad. The smaller slave to master ratio is only going to make the lever pressure harder. Also OP added a SS braided line. While they look cool the main reason why they are prefered is that the hold size under pressure. This means less movement of the lever. Lever feels blocky.
Single caliper systems typically use 9/16 - 5/8 on a single HD caliper (pre Brembo). Doubles 11/16 to 3/4. In both cases, the smaller master cylinder works better. The OP has a master that is way too large for a single caliper. I've had to mess with different brake system on different custom and stock bikes. The bobber I own has had 3 master cylinder configurations on the front and 2 on the rear. I know it when I see it.
Add:
I'm sure Dan does too.
https://www.wilwood.com/calipers/Cal...%20%20&appid=0
The Wilwood has an effective area of 2.46 sq in.. They only make one caliper size. So the effective area for FLH will be 3.52 to 4.81 inches for 2 calipers. Comparing the total pad pressure between 1 Wilwood and 2 Stock calipers is reduced to 70% to 51% depending on the FLH caliper piston diameter. Kind means you are going to have to squeeze the lever 30 to 49% harder to get the same force on the pad. The smaller slave to master ratio is only going to make the lever pressure harder. Also OP added a SS braided line. While they look cool the main reason why they are prefered is that the hold size under pressure. This means less movement of the lever. Lever feels blocky.
Single caliper systems typically use 9/16 - 5/8 on a single HD caliper (pre Brembo). Doubles 11/16 to 3/4. In both cases, the smaller master cylinder works better. The OP has a master that is way too large for a single caliper. I've had to mess with different brake system on different custom and stock bikes. The bobber I own has had 3 master cylinder configurations on the front and 2 on the rear. I know it when I see it.
Add:
I'm sure Dan does too.
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Thread Starter
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Road Warrior
Joined: Aug 2020
Posts: 1,284
Likes: 2,089
From: NC
just to follow up wilwood contacted me back and said that the caliper would work with either 9/16 or 5/8, their words:Thank you for the inquiry with Wilwood Disc Brakes.
You can potentially use either a 9/16 or 5/8 bore master cylinder on your Harley depending on your preference.The 9/16 will be easier to pull on / use, but may feel a little spongy.
The 5/8 will make it easier to modulate the brakes, but will take more effort on the lever.
Regards,
Wilwood Disc Brakes
You can potentially use either a 9/16 or 5/8 bore master cylinder on your Harley depending on your preference.The 9/16 will be easier to pull on / use, but may feel a little spongy.
The 5/8 will make it easier to modulate the brakes, but will take more effort on the lever.
Regards,
Wilwood Disc Brakes