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K5 1000 Caliper Upgrade Question

11K views 29 replies 10 participants last post by  remusr 
#1 ·
Good day all.

I have been offered to replace the stock Tokico split calipers for a set of mono block calipers. Apparently this will improve my issues with brake fade when riding hard (my lever pulls all the way back to throttle after about 15 minutes of hard track riding).



Upgrades already done is new discs, braided hose lines, Motul RBF 660. Bike has had the M/C recall repair.

I can get this upgrade done for a nominal cost so I'm thinking of doing it anyway, leaving only the M/C replacement in future to be the only option remaining. Would love to hear some professional advise please.
 
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#5 ·
Just an fyi, the calipers are not the biggest factor in what causes brake fade.

Have you replaced your m/c?

Have you replaced your stock lines with braided ss lines?

Have you flushed and bled the entire system properly with high-quality DOT4 brake fluid?
 
#6 ·
This, 100%.

I know plenty of trackday riders and local racers who can brake hard enough to lift the rear wheel at speed and that's with the stock Tokico calipers, rotors and MC. You haven't mentioned what brake pads you're running either. It's a popular mod, no doubt, and not dissuading you from doing it. Just don't be disappointed if things don't turn out like you expected.

PS: Just so you know the Sumitomo monoblocks, while marginally lighter than the two-piece calipers, carry smaller pistons. This may affect your MC to caliper ratio and alter your leverage at the lever.
 

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#7 ·
I'm leery about swapping used brake components from different make and model bikes. A lot of people don't fully understand the effects of changing these components and just bolt them on because some guy on the internet said it was a good idea. The stock calipers (and/or rotors) are not the weak point in the stock braking system.

First thing I'd do is clean the caliper pistons thoroughly, then do a proper bleed/flush with a new bottle of high quality dot4. If the bottle has been opened for a while, get a fresh supply.

You already have new brake lines so no need to get into that.

Still fading? Get some new pads. There are a ton of good pad choices these days. Lots of people swear by Vesrah pads. I prefer Carbone Loraine, I use their SBK5 street pads on my 600 track bike and they work well. I use the C60 race pads on my ZX10 but I wouldn't use race pads if you ride on the street.

If you're still having brake issues, it could be a bad master cylinder. My opinion, if you're going to change the master cylinder, go with a Brembo. I like the 19x18 forged. They cost around $240 and make a huge improvement in feel at the lever. I'd spend money on a new master cylinder (not an eBay used part from some other bike) before I spent money on calipers or rotors unless the rotors are worn out.

Moto Joe has a very good write-up for brake bleeding on here. It's now my preferred method, but I do still use the mighty vac to get started if I've completely drained the system (replacing hoses, rebuild the calipers, etc)

Hope that helps. I don't know how you use your bike or your skill level and I don't want to make assumptions. In my case, I've had no problems with stock rotors and calipers. I don't race, I'm just a "track day hero" riding in the advanced group. I don't do much street riding anymore but I have never had brake fade on the street, even when riding like a complete goon.
 
#10 ·
I'm leery about swapping used brake components from different make and model bikes. A lot of people don't fully understand the effects of changing these components and just bolt them on because some guy on the internet said it was a good idea. The stock calipers (and/or rotors) are not the weak point in the stock braking system.
IIRC swapping out the stock GSXR calipers for the smaller R1/R6 monoblocks was the hot ticket for the 16.5" wheels that race teams were running back then. Trying to squeeze the original calipers past the rim was a PITA and made for frustrating tire changes. The Sumitomo calipers gave mechanics a wee bit more wiggle room. :cheers
 
#8 ·
As best I know, the Yamaha calipers have smaller pistons leading to about 20% less area and a corresponding stiffer lever. This lowers the caliper-to-MC area ratio and moves it even further away from the optimum. I think the Yamaha MC has a significantly smaller bore to go with the smaller caliper pistons. Do you know what your calipers came off and what the bore sizes are?

The stock ratio is 22.7 vs 27 ideal. No guarantees but I think the Yamaha calipers lower it to around 18. It's around 26 with the 16 mm Yamaha MC.
 
#13 ·
Hi guys. Thanks for all the comments.

Since I bought the bike I've struggled with the brakes. I ride predominantly on track in the fast group. My problem was initially brake fade and warped discs so I replaced the discs which got rid of the warping. At the same time I replaced whatever pads were installed with Ferodo XRAC pads. I also replaced the brake hoses with braided hoses. I bled the system completely and as per the post mentioned on the forum with an entire bottle of Motul RBF660 brake fluid. This all improved my brake fade by about 5-10 minutes extra time on track but I'm still not satisfied.

In the end I got the calipers for even less when I went to have a look at them. I'm going to give it a go and see what happens but will probably also look for a new M/C.

In summary for normal road riding I have no issues with my brakes and one emergency stop almost had my back end come over my head the one day. On track, however, the quality of braking radically reduces which sometimes forces me to come off track before my session expires.
 
#14 ·
All those upgrades to the brakes and I don't see anything about the m/c...

:scratch
 
#16 ·
I cured all my fading lever issues with one of these
With a clutch m/c???

:lmao

I know what you meant, just funny that you posted a clutch m/c and not a brake m/c.

Edit: I see you changed the picture...
 
#22 ·
^A really important issue is its piston diameter. If it's 16 mm, as mentioned here, it will make a major difference. However note the criticisms of OEM versions.

With regard to the Brembo RCS, the listed version for our bikes is the 19RCS. However I'm suspicious that the newer 17RCS is a better match. Accossato is of similar high quality and has a greater range of offset adjustment - by changing the lever rather than turning a screw. But I don't think that it has an integral mechanical brake light switch.
 
#23 · (Edited)
Hi Bill. Thanks for the info. I got a Brembo MC 16mm from Big Bang I believe for a steal including levers. So all in all I got the calipers and M/C and levers and spacers for US$ 72.

Edit: After reading the entire link, how does one reverse bleed the system?
 
#24 ·
^Do a Google search for reverse bleeding. IMO it's better suited to dirt bikes etc. where the bleeders sit out from the wheels. You tend to leak fluid when reverse bleeding. It falls to the floor on a dirt bike but gets all over things on ours. A bleeder with sealant on the threads will help.
 
#27 ·
If you loop the wheelie very carefully, when the bike lands upside down you can reverse bleed them easily.

:thumbup

:lmao
 
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#29 ·
It might, that is why I suggest wearing a suit of armor, like knights used to wear, you know?

:biggrin
 
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