REVIEWS DEALS BIKESHOPS TRAILS

Franken brakes?

1804 Views 11 Replies 6 Participants Last post by mtbfree, Nov 29, 2021

keen

Discussion Starter · Nov 25, 2021

My buddy has Hope Tech 3 V4 brakes. In the process of his bleed he managed to damage the reservoir top seal (Has one ordered) He has a SRAM Guide lever / hose that he wants to use w/ the Hope caliper. Externally, looking @ the caliper connection, it looks possible assuming the banjo bolts are the same size. I googled the 4 piston sizes and they are equally sized. Any reason this wouldn't work? Thanks.

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the-one1

· #2 · Nov 25, 2021

They both use the same fluid type. If the fittings fit, give it a try.

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keen

Discussion Starter · #3 · Nov 26, 2021

the-one1 said:
They both use the same fluid type. If the fittings fit, give it a try.

My buddy was going to go for it but I thought I’d appeal to the masses as I might end up involved with the transplant.

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mtbfree

· #4 · Nov 26, 2021

keen said:
My buddy was going to go for it but I thought I’d appeal to the masses as I might end up involved with the transplant.

There are few point on bike where you don't take ANY risks:

torque of stem bolts
crack on rims
brakes

Any of these will probably fail not on car park test but when going some gnarly terrain at speed. Not worth few 10s of $ for me. And waiting line for transplants are quite long these days....

He should just buy another Hope lever and sell SRAM one to minize the costs...

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uzurpator

· #5 · Nov 26, 2021

I heard from a reputable source ( the internet ) that coupling brake parts from different manufacturers causes a spontaneous boom with a yield between 0.5 and 1 kiloton. For the safety reasons I suggest to vacate the place you live, if it is within 1 mile radius from your friend.

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Jokes aside. I have a frankenbrake made of hope lever caressing a formula caliper. It works just fine. Shigura brakes ( shimano levers, magura calipers ) also seem to be pretty popular.

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rete

· #6 · Nov 27, 2021

The Guides have a smaller master cylinder in the lever than the Hope V4, the Hope V4 has larger slave pistons in the caliper than Guide. The combination of Guide lever and Hope V4 caliper won't feel like either brake and the lever will probably like to throw all the way to the bar and require an "over-bleed".

Hope Tech 3 V4 brakes has:
Caliper - 18mm and 16mm pistons; 911.06 sq.mm slave area in caliper
Lever - 10mm piston; 78.54 sq.mm master area in lever
=> Hydraulic leverage = 5.80

SRAM Guide (R, RS, RSC, Ultimate) has:
Caliper - 16mm and 14mm pistons; 710.00 sq.mm slave area in caliper
Lever - 9.5mm piston; 70.88 sq.mm master area in lever
=> Hydraulic leverage = 5.01

The combination Guide lever with Hope caliper will have:
Caliper - 18mm and 16mm pistons; 911.06 sq.mm slave area in caliper
Lever - 9.5mm piston; 70.88 sq.mm master area in lever
=> Hydraulic leverage = 6.43

Generally, increasing hydraulic leverage equates to more powerful brakes - but the additional 28% hydraulic leverage with the Hope caliper connected to a Guide lever will also manifest itself as 28% additional Guide lever throw (compared to using a Guide caliper).

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AdamR83

· #7 · Nov 27, 2021

^^ Nearly... you have to factor in the leverage ratio of the blade itself too.

I love theory, don't get me wrong, but reality is king and it works just fine. Have used X2 calipers with Guide levers in the past, and of course Hope fit the same lever to their X2 and V4 brakes...

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keen

Discussion Starter · #8 · Nov 27, 2021

rete said:
The Guides have a smaller master cylinder in the lever than the Hope V4, the Hope V4 has larger slave pistons in the caliper than Guide. The combination of Guide lever and Hope V4 caliper won't feel like either brake and the lever will probably like to throw all the way to the bar and require an "over-bleed".

Hope Tech 3 V4 brakes has:
Caliper - 18mm and 16mm pistons; 911.06 sq.mm slave area in caliper
Lever - 10mm piston; 78.54 sq.mm master area in lever
=> Hydraulic leverage = 5.80

SRAM Guide (R, RS, RSC, Ultimate) has:
Caliper - 16mm and 14mm pistons; 710.00 sq.mm slave area in caliper
Lever - 9.5mm piston; 70.88 sq.mm master area in lever
=> Hydraulic leverage = 5.01

The combination Guide lever with Hope caliper will have:
Caliper - 18mm and 16mm pistons; 911.06 sq.mm slave area in caliper
Lever - 9.5mm piston; 70.88 sq.mm master area in lever
=> Hydraulic leverage = 6.43

Generally, increasing hydraulic leverage equates to more powerful brakes - but the additional 28% hydraulic leverage with the Hope caliper connected to a Guide lever will also manifest itself as 28% additional Guide lever throw (compared to using a Guide caliper).

Are you sure about Hope Tech 3 V4's having 18/16mm pistons? I read a review they use a 16/14mm arrangement and the E4's are 14/14mm pistons. I went to Hopes website and the V4 & E4 both have the same part number for the smaller piston. Have not found any info on the large V4 piston.

https://www.mbr.co.uk/reviews/disc-brakes-products/hope-tech-3-v4-disc#:~:text=The%20Hope%20Tech%203%20V4,when%20we're%20talking%20power.&text=The%20extra%20bite%20is%20achieved,E4%20uses%2014mm%20all%20round

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AdamR83

· #9 · Nov 27, 2021 (Edited)

V4s are 18/16mm, E4s are 16mm. X2 is 22mm piston for reference. Do the maths and you can see the E4 is basically the same power as an X2, V4 slightly more power and about the same as the old V2.

Hope E4 Caliper Seal Kit

Buy Hope E4 Caliper Seal Kit as well as a wide range of Disc Brake Spares and other trials bike products from the world's leading trials bike shop, TartyBikes.

www.tartybikes.co.uk

Hope V4 Caliper Seal Kit

Buy Hope V4 Caliper Seal Kit as well as a wide range of Disc Brake Spares and other trials bike products from the world's leading trials bike shop, TartyBikes.

www.tartybikes.co.uk

It works. End of thread.

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rete

· #10 · Nov 27, 2021 (Edited)

AdamR83 said:
^^ Nearly... you have to factor in the leverage ratio of the blade itself too.

I love theory, don't get me wrong, but reality is king and it works just fine. Have used X2 calipers with Guide levers in the past, and of course Hope fit the same lever to their X2 and V4 brakes...

Of course, mechanical leverage multiplies hydraulic leverage. And Hope V4 lever's average mechanical ratio (not the more complicated mechanical leverage curve) of 6.136 is the same as SRAM Code and Guide levers at 6.136. The SRAM Swing Link vs Direct Link levers have the same ultimate average mechanical leverage ratio, but different curves through the lever throw. Guide and Code levers (Swing Link and Direct Link respectively) are internally identical and have identical mechanical leverage characteristics.

In the case of OP's combo the hydraulic leverage ratio increase seen by the lever is the major (theoretical) variable.

Having done these types of experiments myself, some work and some don't. As you say, reality is king.

A nice database of brake leverage ratios maintained by a ridemonkey forum user, including the more common franken mix'n'match combinations can be found here.

This site presents some visualization of the same data. I added a custom Code lever + Hope V4 caliper brake - screenshot below.