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Discussion Starter · #1 ·
I had a high side at a track day and ground down the top of the master cylinder. Can anyone tell me if this is fixable? I'm worried about the hole that's opened up left of the circlip.
575335
 

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Dreaming of buttsecks for years...
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It's more than fade. It's fatigue and arm pump too. It's a world of difference. Look at it this way. You can get a Brembo for $80 off now.
 

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I think that you may have the same crappy brakes that my K6 1000 came with. One issue is the caliper to MC area ratio, which is 22.7. It's considered to be too stiff, the accepted standards being 20:Wooden, 23:Firm, 27:Sweet Spot, and 30:Soft Feel. You can increase yours to 27 by switching to a K9-L1 1000 MC. It has a smaller 17.5 mm bore versus your current 19.1 mm. This is the MC that was used with the Tokico monoblocs and is probably available for a similar price to yours. You'll have to do some checking but it was probably also used on 600/750.
 

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I think that you may have the same crappy brakes that my K6 1000 came with. One issue is the caliper to MC area ratio, which is 22.7. It's considered to be too stiff, the accepted standards being 20:Wooden, 23:Firm, 27:Sweet Spot, and 30:Soft Feel. You can increase yours to 27 by switching to a K9-L1 1000 MC. It has a smaller 17.5 mm bore versus your current 19.1 mm. This is the MC that was used with the Tokico monoblocs and is probably available for a similar price to yours. You'll have to do some checking but it was probably also used on 600/750.
This is what I need too! I have the K9 Mono's
 

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Discussion Starter · #13 ·
I think that you may have the same crappy brakes that my K6 1000 came with. One issue is the caliper to MC area ratio, which is 22.7. It's considered to be too stiff, the accepted standards being 20:Wooden, 23:Firm, 27:Sweet Spot, and 30:Soft Feel. You can increase yours to 27 by switching to a K9-L1 1000 MC. It has a smaller 17.5 mm bore versus your current 19.1 mm. This is the MC that was used with the Tokico monoblocs and is probably available for a similar price to yours. You'll have to do some checking but it was probably also used on 600/750.
Thanks for those numbers, they're helping me think through this. Y'all don't know how tempting it is to justify the brembo... maybe I can compromise with an accossato?

But I think your numbers are for the newer calipers that have 32mm pistons. Which give a ratio of 26.7 using a 17.5mm MC piston.

My calipers are the 34mm piston diameter Tokicos which is 8*pi*(34/2)^2=7263mm^2. The 19.1mm piston has an area of 287mm^2. If these numbers are right then the ratio was ~25. I would have preferred just a tad stiffer, but overall felt really good and at no point have I ever felt like the brakes couldn't give more. A 17.5mm MC piston would be a ratio of over 30.
 

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My numbers came from the K6 600 service manual (with an obvious error corrected). The leading front is 30.175 mm and the trailing is 33.909 mm for a total area of 6472.78 sq mm. The MC bore is 19.0715 mm or 285.67 sq mm. They're the same as a K5-K8 1000 so I assume that they also apply to the K6 750.

Those calipers have a poor reputation. If you're limited on money, I'd suggest first upgrading to the Tokico monoblocs and the associated MC. I think you can get all that for significantly less than an RCS.

I haven't looked recently but my impression is that Brembo and Accossato are priced about the same. Accossato offers a neat-o electronic adjuster but it's mucho dinero.
 

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Discussion Starter · #15 ·
My numbers came from the K6 600 service manual (with an obvious error corrected). The leading front is 30.175 mm and the trailing is 33.909 mm for a total area of 6472.78 sq mm. The MC bore is 19.0715 mm or 285.67 sq mm. They're the same as a K5-K8 1000 so I assume that they also apply to the K6 750.

Those calipers have a poor reputation. If you're limited on money, I'd suggest first upgrading to the Tokico monoblocs and the associated MC. I think you can get all that for significantly less than an RCS.

I haven't looked recently but my impression is that Brembo and Accossato are priced about the same. Accossato offers a neat-o electronic adjuster but it's mucho dinero.
Thank you again, looks like my information was incorrect. Probably the best thing for money is to just get the k9 1000 MC like you suggested. For maybe $115 more I could do the r6 MC and calipers. For $180 more I could get a brembo 19mm.

I think the r6 upgrade gives me the best value. Thoughts?
 

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The issue is that the MC needs to match the calipers. If you get a new MC for your current calipers it forces you to replace both if you later change calipers. I did just that. I originally changed to a 19RCS. Later I switched to the monoblocs and the feeling, already firm, got worse. I bought a 17RCS to fix the feeling and was lucky enough to sell the 19RCS for a decent price.

People tend to pooh-pooh the K9 MC. It's not a Brembo but it's fine, particularly since your current MC is very similar.

The R6 calipers were once popular but you don't hear much about them any more. I think they use an even smaller 16 mm MC.

Finally, this is distant recollection but on the RCS you just turn an adjustment to switch ratios. On the Accossato you have to change levers.
 

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Discussion Starter · #18 ·
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