Sizing a new master cylinder for CBR400RR track bike
Sizing a new master cylinder for CBR400RR track bike
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Discussion

AceOfHearts

Original Poster:

5,957 posts

221 months

Wednesday 22nd September 2021
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I'm sure other people on here have done similar, but I am looking at replacing the front brake master cylinder on my CBR400 track bike with something from Brembo or HEL

Common bore sizes seem to be 19mm and 16mm, however my bike has 2 x twin piston floating calipers (25.5mm pistons) and as standard uses a 1/2" or 13mm master cylinder.

I have found a few ancient threads on the old 400 forum where people have said they have used a Brembo 19mm master cylinder to good effect, but it seems like a very large change and I would rather do my own research and calculations before ordering anything up.

Any tips or advice?

rodericb

8,903 posts

156 months

Wednesday 22nd September 2021
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Why do you want to change it? Can't overhaul the OE one? Want more leverage/power over the pads? Are you looking at axial or radial? At a guess you'd probably go for a 16mm if that's what you've seen available. There are some master cylinder sizing guides on the internet, such as this one: http://www.acv.co.jp/galespeed_en/01_master_ratio_...

It starts to get complicated once you start factoring in pad compound. Have you thought about changing the sliding calipers to opposing piston?

moanthebairns

19,150 posts

228 months

Thursday 23rd September 2021
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I have two Brembos on bikes and one HEL.

Personally, I think the Brembo is the better master cylinder. It gives more feel, the HEL feels almost wooden in comparison. It's better than the m/c that was fked on my Daytona but I wouldn't be in a rush to change it over a standard m/c in good nick, especially for the road, track ok.

The Brembo on the other hand is just delicious feeling.


Merch131

996 posts

179 months

Thursday 23rd September 2021
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HEL master cylinders have variable piston size, just bought a pair, finish is just as good as Brembo RCS imo.

NITO

1,336 posts

236 months

Thursday 23rd September 2021
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Here's a calculator to work out the ratios

http://www.acv.co.jp/galespeed_en/01_master_ratio_...

AceOfHearts

Original Poster:

5,957 posts

221 months

Thursday 23rd September 2021
quotequote all
Thankyou guys, I will do some calcs then get ordering. It is for my track bike, and seems a waste rebuilding the horrible old one when I could use the opportunity to upgrade it thumbup

Steve Bass

10,751 posts

263 months

Friday 24th September 2021
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Have a look at Accusato as well.

I have one on my RS250 and it has lovely fell, good quality and decent pricing.....

lukeyman

1,100 posts

165 months

Friday 24th September 2021
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Steve Bass said:
Have a look at Accusato as well.

I have one on my RS250 and it has lovely fell, good quality and decent pricing.....
I got the fixed lever/integrated reservoir version from these guys:

https://www.drbikes.co.uk/brand/accossato/