artpongs Posted February 11, 2017 Share Posted February 11, 2017 I've located on eBay a picture of the 8th gen master cylinder and it is 14mm, which matches the F4i master cylinder I currently have installed on my 5th gen with delinked brakes with stock modified rear caliper. So in theory, the 8th gen rear caliper that is smaller, and lighter which uses 2 pistons can be adapted to fit the 5th gen as long as a custom brake carrier can be fabricated. This is provided obviously if you already or are planning to get rid of the linked brake system on the stock bike. Will be researching more and reaching out to fabricators that are able to make this happen if everything lines up. Art Link to comment Share on other sites More sharing options...
Member Contributer sfdownhill Posted February 11, 2017 Member Contributer Share Posted February 11, 2017 If you measure the pistons in an 8 gen rear caliper, you can use this to find out what combo will give you the braking power you choose: http://vfrworld.com/forums/attachment.php?attachmentid=40184 Link to comment Share on other sites More sharing options...
artpongs Posted February 11, 2017 Author Share Posted February 11, 2017 @sfdownhill thank you for the chart, it would be helpful if any 8th gen owners chimed in on my threads. However, it looks like the 14mm rear master cylinder is stock to the 8th gen rear caliper already. So using the 14mm F4i I currently have installed on my 5th gen, to use the 8th gen caliper if it was able to be adapted to fit with a custom carrier, would be "stock" specs. Is my initial post confusing? Art Link to comment Share on other sites More sharing options...
artpongs Posted February 11, 2017 Author Share Posted February 11, 2017 Well after a bit more research, here is some more info that could be added to that sticky/chart if possible. 8th gen rear caliper uses 2 25.4mm diameter pistons with a 14mm master cylinder. RC30 and RC45 also uses 2 25.4mm piston rear caliper fyi but not sure of their master cylinder size. The rebuild kit I found lists these bikes as compatible for the rear calipers. Art Link to comment Share on other sites More sharing options...
artpongs Posted February 11, 2017 Author Share Posted February 11, 2017 I see that Brembo makes 32mm and 34mm single piston rear calipers as well. Whats the calculation for surface area? And how do you calculate the ratios with each master cylinder size? Art Link to comment Share on other sites More sharing options...
Member Contributer JZH Posted February 11, 2017 Member Contributer Share Posted February 11, 2017 Area is "pi x radius^2", so a 32mm OD piston area would be 804.25mm^2. A 14mm master cylinder has an area of 153.9mm^2. The ratio is total piston area divided by master cylinder area, so 5.23 for the above combo. Thanks for the RC79 info; I have updated the chart. Rear Brake Ratios-20170211.bmp Ciao, Link to comment Share on other sites More sharing options...
artpongs Posted February 12, 2017 Author Share Posted February 12, 2017 JZH, Out of curiosity, you have the 5th gen and you are going to mount the 6th gen rear caliper up? They line up correctly with no modifications? Also, the rear brake carrier for the 6th and 5th gen, are they able to be swapped with one another or different design? Art Link to comment Share on other sites More sharing options...
Member Contributer JZH Posted February 12, 2017 Member Contributer Share Posted February 12, 2017 They appear to be identical, IIRC. Both caliper and bracket. I'm using the 6th gen caliper just because the ratio works out slightly closer to a "normal" rear brake than the 5th gen caliper (both with a 14mm rear master). Ciao, Link to comment Share on other sites More sharing options...
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