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Old 03-07-2011, 02:05 PM   #1
Ddouble OP
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Big brakes on a KLR- DD goes overboard

The front brake is well known deficiency on 1st model KLR 650s. When I bought my KLR it was equipped with the 320mm oversize front rotor that is available from several sources. It also had the recommended braided SS brake lines. The brakes were OK, but not as powerful as I prefer for an aggressively ridden street bike.

I have upgraded the brakes on a number of my other bikes, mostly vintage stuff. I took a look at the stock caliper and master cylinder. The stock caliper is a 38mm single piston sliding pin design. I dug out my box of calipers that I have accumulated over the years from parts bikes and eBay. My first inclination was to use a 4 piston Tokico that was used on many Japanese street bikes in the 90s. The housing for the rear pistons interfered with the spokes, so I grabbed a 2 piston sliding pin Brembo from the rear of a Guzzi California. Hmmm, it has a 32mm & 30mm piston. That will be about a 33% increase in mechanical advantage over the stocker. No interference with the spokes either. As it turns out, this caliper is also used on the front of KTM Adventures, BMW F650s, and Guzzi Quotas. I think we have a winner.

The stock master cylinder is a 1/2" bore. That is already pretty small. About the smallest MCs I have seen readily available are 11mm. I found a 11mm bore Nissin from a Honda CRF150. You could also buy a new one from http://www.mikesxs.net part #08-4003 for $76.00. The 11mm master cylinder provides an increase of 22% in mechanical advantage - about the same as the larger rotor.

I fabricated a bracket to adapt the caliper on Sunday. Normally, I have done this from aluminum. In this case though, I used steel since I was working away from home and didn't have much in the way of machine tools. Working with steel plate allowed me to weld it up from 3 pieces.

I put everything together and took it for a test drive. WHOAA! I didn't know if it was really possible for me, but I think I may have created a front brake that is stronger than I want or need. The CRF MC has a shorty 2 finger lever on it, and I can lock the front wheel without much effort. I rode it to work today, and I am liking it better, but only gentle pressure is needed on the brake lever. I'm going to change the pads out first, but I think I might go back to the stock MC.

Anyways, I think a KLR owner looking to upgrade his brakes has some options. Especially, if he has metal fabrication capabilities. The master cylinder upgrade is cheap and easy. The caliper upgrade is also fairly cheap if you can find a suitable caliper used. The bracket fabrication is not terribly difficult. The rotor upgrade can be a simple bolt-on, has bling, but it is the most expensive option.

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From KLR brake upgrades
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From KLR brake upgrades
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From KLR brake upgrades
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From KLR brake upgrades
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Old 03-07-2011, 02:25 PM   #2
ABHooligan
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Originally Posted by Ddouble View Post

The stock master cylinder is a 1/2" bore. That is already pretty small. About the smallest MCs I have seen readily available are 11mm. I found a 11mm bore Nissin from a Honda CRF150. You could also buy a new one from http://www.mikesxs.net part #08-4003 for $76.00. The 11mm master cylinder provides an increase of 22% in mechanical advantage - about the same as the larger rotor.
I've never been able to get good brakes on the KLR, so I'm confused here. You went from a 1/2" bore M/C (which is 13mm) down to an 11mm bore. Smaller. How does this promote better brakes? Seems this wouldn't displace enough fluid for the two-piston caliper. I went the opposite direction, from a 1/2" up to a 5/8". I got a firm lever, but pretty wooden.
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Old 03-07-2011, 02:38 PM   #3
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With an identical master cylinder design except for piston bore, a smaller piston gives higher pressure in the brake system at the same amount of force on the brake lever. Same pounds on the lever with smaller square inches equals more pounds per square inch.

Some more info: http://www.vintagebrake.com/mastercylinder.htm

A larger bore cylinder will do exactly what your results were. Less PSI equals less braking force and a firmer feel at the lever.
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Old 03-07-2011, 02:45 PM   #4
Ceemack
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Thanks for the explanation of the smaller vs. larger issue. I was kind of thrown by the 11mm bore myself.

But now I wonder what effect each piece would have by itself--the smaller-bore master cylinder with the stock caliper, or the replacement caliper with the stock master cylinder.

Nice job, though. I've wondered why oversized rotors were the only solution for less-than-ideal braking on the KLR.
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Old 03-07-2011, 03:08 PM   #5
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Originally Posted by Ceemack View Post
I've wondered why oversized rotors were the only solution for less-than-ideal braking on the KLR.
"Only" is an absolute, to be used carefully!

Actually, dual-piston calipers and corresponding aftermarket master cyclinders have been available for pre-'08 KLR650's.

Post # 29 on this thread: http://www.klr650.net/forums/showthr...t=42440&page=2 has some words-and-pictures involving a dual-piston caliper on an earlier KLR650, but . . . I find no contemporary source for these products.

XDragRacer screwed with this post 03-07-2011 at 03:29 PM
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Old 03-07-2011, 03:19 PM   #6
Ddouble OP
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Originally Posted by Ceemack View Post
Thanks for the explanation of the smaller vs. larger issue. I was kind of thrown by the 11mm bore myself.

But now I wonder what effect each piece would have by itself--the smaller-bore master cylinder with the stock caliper, or the replacement caliper with the stock master cylinder.

Nice job, though. I've wondered why oversized rotors were the only solution for less-than-ideal braking on the KLR.
I had tried it with the 11mm MC and the stock caliper. It had very good power. It felt a little "flexy" though. I suspected that the flex might be coming from the caliper, hence my desire to upgrade the caliper.

I think that the 2 piston caliper with the stock 1/2" MC might be ideal. I'll probably go back to that at some time. However, for a quick and cheap upgrade, it would be hard to beat an 11mm master cylinder on the stock caliper.
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Old 03-07-2011, 03:45 PM   #7
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A bit off-topic, but . . . I'm intrigued by the fact, EVERY specification sheet for '08 and later KLR650's, including Kawasaki's, incorrectly describes the rear brake caliper as, "Single-Piston," when in fact it's a two-piston system . . .

True in '08; still true in '11.

Google "KLR650 Specifications," or go to the factory website http;//www.kawasaki.com , and . . . you'll see!
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Old 03-09-2011, 01:02 PM   #8
ABHooligan
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I initially installed a two-piston caliper w/stock m/c, and there was a lot of travel before I got brakes, but when they came, they were quite strong, but just before the lever hit the bar. So, I thought the stocker lacked volume, since it was having to move two pistons vs one, thus the 5/8 m/c.

How could I remedy the problem of the long travel before brake actuation (and have a working brake light switch)?

PS: I'm not trying to debate here. I'm a fair mechanic, but honestly I lack a bit in the theory area, and am seeking a bit of guidance.
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Old 03-09-2011, 01:30 PM   #9
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You are correct that there will be more lever travel with the smaller MC. However, it sounds like maybe there was something else going on as well.

The adapter bracket for the 2 piston caliper may be a little bit "off". If the pads are not parallel to the brake disk, they will have to travel extra distance to clamp down tightly. This will improve as the pads wear and bed into the disk surface. You could check for this by loosening the caliper mounting bolts so that the caliper is free to float and then check the lever travel after several pumps. If this is the case you may have to shim the mounts a little.

Of course, also make sure that the system is well bled.

With my 11mm MC and the Brembo 2 piston caliper (that I believe probably has bigger pistons) I have plenty of "lever". This should be a more extreme condition than your set-up.
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Old 07-21-2011, 08:26 AM   #10
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Thanks for the wealth of information on braking systems! I've spent some time looking at the chart you mentioned and at aftermarket master cylinders. I am curious about your CRF150 master cylinder. Did you rig up a brake light switch somehow? That would seem to be the biggest drawback to using that particular master cylinder.

I have a '90 KLR that has SS lines already, but could definitely use some more help in the braking department. A rotor upgrade is not in the budget, but a master cylinder is possible.
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Old 07-21-2011, 09:12 AM   #11
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Originally Posted by jdwxly View Post
Thanks for the wealth of information on braking systems! I've spent some time looking at the chart you mentioned and at aftermarket master cylinders. I am curious about your CRF150 master cylinder. Did you rig up a brake light switch somehow? That would seem to be the biggest drawback to using that particular master cylinder.

I have a '90 KLR that has SS lines already, but could definitely use some more help in the braking department. A rotor upgrade is not in the budget, but a master cylinder is possible.
Yeah, I've got a brake light switch. I used a banjo bolt hydraulic switch. You can find one here http://www.mikesxs.net/products-73.html#products for $11. Mike's XS also has a generic 11mm master cylinder for $76 with a brake light switch.

I installed the banjo bolt switch right at the master cylinder and wired into the stock brake light switch wiring connectors.

As an update, I've put a few thousand miles on my brake set-up and it really is pretty impressive. I think I have similar braking power to my Ducati 900SS - that ain't bad!
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Old 07-22-2011, 12:08 AM   #12
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Yeah, I've got a brake light switch. I used a banjo bolt hydraulic switch. You can find one here http://www.mikesxs.net/products-73.html#products for $11. Mike's XS also has a generic 11mm master cylinder for $76 with a brake light switch.

I installed the banjo bolt switch right at the master cylinder and wired into the stock brake light switch wiring connectors.

As an update, I've put a few thousand miles on my brake set-up and it really is pretty impressive. I think I have similar braking power to my Ducati 900SS - that ain't bad!

so can we get a break down on the calipers you used i.e where they came from like make model ect. eather you already did and im blind or ya didnt lol
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Old 07-22-2011, 04:02 AM   #13
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so can we get a break down on the calipers you used i.e where they came from like make model ect. eather you already did and im blind or ya didnt lol
I did mention it earlier! But, it was a Brembo 2 piston sliding pin caliper that I had laying around. It came off the rear of a '98 Guzzi California. They used them on a lot of Italian bikes of that era as well as on the front of KTM Adventures, BMW F650s, and Guzzi Quotas. It has onee 32mm piston and one 30mm piston.

This works well for me. But, I doubt if there is anything particularly magical about this caliper. There are probably others that will also fit the bill (that might even be easier to adapt). We are looking for something with more piston area than stock. This caliper has 33% more area

I was hoping to use a 4 piston caliper with opposing pistons. But, the ones I tried had interference issue with the spokes on the back side. It may be best to concentrate on sliding pin designs.
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Old 08-25-2011, 12:57 PM   #14
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CRF150F or CRF150R?

I finally have my '90 KLR on the road (took a while to get a replacement title out of California) and I am watching eBay for a CRF150 master cylinder. I noticed some folks listing CRF150F parts and others listing CRF150R parts (which they call "Expert" or some such thing). Looking on BikeBandit I see that these are two different part numbers for the MC assembly and also for the piston assembly alone. Does anyone know whether they are both 11mm piston bore? Any reason to choose one over the other for my KLR?

Thanks for providing all the information about this upgrade!
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Old 08-30-2011, 08:31 AM   #15
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Originally Posted by jdwxly View Post
I finally have my '90 KLR on the road (took a while to get a replacement title out of California) and I am watching eBay for a CRF150 master cylinder. I noticed some folks listing CRF150F parts and others listing CRF150R parts (which they call "Expert" or some such thing). Looking on BikeBandit I see that these are two different part numbers for the MC assembly and also for the piston assembly alone. Does anyone know whether they are both 11mm piston bore? Any reason to choose one over the other for my KLR?

Thanks for providing all the information about this upgrade!
Sorry, I don't really know much about CRF master cylinders. I bought mine on eBay because the price was right and I could clearly see "11" cast into the cylinder in the pictures. Now, my gut feeling is that a F and a R would probably have the same bore master cylinder. But, no guarantees.
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