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rebuilt caliper, installed stainless brake lines

Old 08-12-2005, 10:58 PM
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rebuilt caliper, installed stainless brake lines

My brakes were really mushy. Using full hand strength I could pull the lever back to the bar, although this is more force than I've ever applied while riding.

I noticed that the brakes were a little better immediatelly after I bled them, and that the bubbles came out right away, then no more. But the brakes would be really mushy again in about a week. Suspected that the problem was a leak in the caliper pistons.

Ordered a pair of caliper rebuild kits from local bike shop. $66 for 16 puny little seals, 2 per piston, 4 pistons per caliper (different sizes), 2 calipers per bike. Replaced with little drama, except for firing one of the sticky caliper pistons into my forehead using pressure from a bike pump (loosen the pistons with air pressure *before* cracking the caliper sides apart.)

Anyway, this fixed the air leak, they stayed the same for 3 weeks, but the brakes still didn't feel that great.

Against the advice of a vintage bmw riding from work "stainless lines was a scam!" I purchased Goodridge stainless brake lines and installed them, purchased from local shop for $84. I like the levers pointed downwards more than stock, and the start of the brake line is rigid. I had to rotate the lever/master cylinder upwards a bit to get the new lines to install. I've heard that other folks grind off the bit of metal that protrudes from the master cylinder?

Torqued everything back down. Ingested almost no brake fluid sucking the fluid down to the calipers. Result is very firm brake lever with immediate feedback. Still a little squish, but no way could I touch the bar with the lever, even with two hands I've still got about 1.5 inches of clearance. Can't wait to try them out tomorrow.
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Old 08-13-2005, 07:31 AM
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Re: rebuilt caliper, installed stainless brake lines

I don't know what your bmw friend has againts ss lines I think they're awesome. I put mine on the night before a track day without trying them and almost put myself over the bars using the same pressure I did with the original lines. great feel compared too.
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Old 08-15-2005, 11:58 AM
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Re: rebuilt caliper, installed stainless brake lines

I had to grind off that poky thing to get my ss lines to point down.

My SS lines kick butt as now I can easily stop with one or two fingers and they are as solid as a rock. We had a helluva time getting all the bubbles out though.
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Old 08-15-2005, 06:48 PM
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Re: rebuilt caliper, installed stainless brake lines

SS line ROCK!
A VAST improvement on the SH.
I got front and rear lines and all new pads from Cyclebrakes.com for about $225.
Money well spent!

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Old 08-15-2005, 07:32 PM
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Re: rebuilt caliper, installed stainless brake lines

Good people that's where I got mine great customer service and good prices.
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Old 08-15-2005, 11:42 PM
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Re: rebuilt caliper, installed stainless brake lines

Ok, definate improvement but they're still a little squishy. There must still be air in them. I'm sure glad I put in the speed bleeders.

The stainless lines really feel nice at higher speeds, very fine control. I would have never considered leaving two fingers behind on the throttle before, but the level won't go there now, so: good!

Well worth the $84. More progressive.

I'm wondering... I heard a story about how a friend once accidentally did a stoppie on his Speed Four when braking heard at an intersection, didn't realize it until the rear of his bike came crashing back down. I've been working hard on my braking, but the front wheel eventually locks up with a dramatic screech, the rear suspension unloads but the rear tire doesn't leave the pavement. I'm having a hard time finding the happy place between silence and lockup, and lockup is scary. Pretty amazing how quicky these bikes can stop, though I'm sure I've got lots of room for improvement.

So, new question: should this bike "stoppie" when sincerly trying to brake quickly? Am I applying the force too quickly and diving the forks?
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Old 08-16-2005, 12:59 AM
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if your front wheel is locking you need to move your weight back a bit while you brake..
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Old 08-16-2005, 07:56 AM
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Re: rebuilt caliper, installed stainless brake lines

Thats counter-intuitive. I'd have thought I needed more weight on the front. If I shift weight back onto the rear tire, thats less to the front, so less friction force available.
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Old 08-17-2005, 06:43 AM
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Re: rebuilt caliper, installed stainless brake lines

Maybe I'm just simple minded, NOT trying to be a [email protected]@, if your front tire is locking up, you are braking too hard.
I have been in some "uncomfortable" situations in the past and have never locked up my front tire.
Hmm... I just don't have any advice - other than practice developing your own, human controled, "ABS" system.

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Old 08-17-2005, 09:03 PM
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Re: rebuilt caliper, installed stainless brake lines

Hey, no offense here! I should have been more clear. I'm stopping what to me appears to be "Insanely Fast". Holy cow. So fast that its hard to appreciate while youre doing it.

I'm a total n00b. I've read a bunch of books about "how to" ride a motorbike, and am trying to teach my body to know what my head now understands.

I am practicing emergency stops, and was under the impression that these sportbike thingys would lift their rear tire under heavy braking on a good surface.

So its a hot afternoon, the dunlop d207 of dubious vintage is warm, and I'm practicing quick stops in the parking lot from around 70mph. I'm conscious and gradual about about applying the brakes, I'm learning how the new lines feel at different rates of deceleration (and they feel really, really good). I'm seeing how applying a little rear brake before the front really does settle the bike. I was sort of expecting the rear end to start rising at some point, but the front makes a gentle huffing, then a loud rude huffing, and then screeches and locks up, and the rear never rises off the ground. I've gone back a few times and the forks aren't bottoming, they are still sucking up bumps nicely while braking hard, which is terrific!

I immediatelly relax the brake when the wheel locks, the bike is pretty squirrelly when the front locks! Is a stoppie something I don't need to worry about with this bike?

I don't want to do a stoppie, but I'm wondering why I haven't. Is it because I'm tall and sitting far back on the seat? Is it the weight distribution of the superhawk? How did my friend on the Triumph Speed Four accidentally raise his rear tire?

As far as braking improvement goes, the stainless lines are really good compared to the spongy grabby feeling I had before, it was much harder to modulate through all that mush.
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Old 08-18-2005, 06:48 AM
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"dont even touch the rear brake for panic."

That's not always true luiggispeed and one of the reasons I don't like the linked brake systems. I don't know how many times I've had to lock the rear brake while panic stopping,(not locking the front just hard braking), to avoid hte a##hole that just pulled his nose out in my lane. Sometimes you have to use the rear brake to make the bike have a controlled slide, to get around what you wouldn't be able to stop before hitting.
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Old 08-18-2005, 06:52 AM
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Sorry typing too fast meant, "the", obviously. Years of practicing this method on dirt bikes has really helped avoid some life threatining accidents.
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Old 08-18-2005, 06:53 AM
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Don't use the back brake if you want to increase the chances you'll hit whatever you are trying to miss. Or if you want to extend your braking distance.

Even a skidding tire stops quicker than a rolling tire. Everyone needs to learn how to use both brakes, even in a quick stop.

Proper use includes modulation and transferring the rider's weight to the rear. You want to stop as quickly as you can, sit up and use both brakes.
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Old 08-18-2005, 07:05 AM
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Re: rebuilt caliper, installed stainless brake lines

jschmidt: good advice!

Regarding the stoppie. I don't do them, but it is all a matter of physics.
You are applying a torque (rotational force) that is centered around the front axle.
if you had a vector diagram, you could see that when sufficient force to overcome the pull of gravity is exerted in the direction opposite of the force of gravity (that is straight up) the back end will start to rise. Since this is a 2 dimensional model, there are also forces applied parallel to the force of gravity (straight forward in this case).
Ah heck, it gets long and complicated.
In a 2 dimensional model, ALL forces can be broken down with trig. (using sine and cosine) into forces up and down, and forces left and right (or front and back).
When the forces reach a certain point the back tire will rise and start to "pivot" around the front axle. The front axle becomes the center of rotaion for the bike as it does a "stoppie".

The higher your center of gravity (and accordingly that of the total mass - you and bike) the quicker a stoppie will occur.
The more forward that same center of gravity, (less weight on rear tire so less force require to raise it off the ground) the quicker a stoppie will occur.


Thanks,
Brian
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Old 08-18-2005, 08:00 AM
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Re: rebuilt caliper, installed stainless brake lines

Look at this now we're learning trig, I love this forum!
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Old 08-18-2005, 09:05 AM
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Re: rebuilt caliper, installed stainless brake lines

Originally Posted by luiggispeed";p=&quot View Post
Mate,you have it backwards.
To be able to apply maximum braking you have to lean your weight as far back as you can,including getting your butt of the seat and bringing it over the pillion seat,specially if you are tall,you must try to lower your CG as low as possible.
And the reason to shift the weight back and keep it low is to prevent the rear wheel from rising?

What I'm hearing is that the superhawk won't stoppie if I keep my weight down and back where it belongs. And I guess this is what I've been trying to ask.

Thanks Brian for the bold attempt to explain this with words! I can see how the weight gets distributed between the two wheels by the force applied to the center of mass.
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Old 08-18-2005, 10:22 AM
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Re: rebuilt caliper, installed stainless brake lines

Oh, I'd imagine most any SH would do a stoppie with most any rider on board.
A stoppie is just a modulated front flip - that is to say a front flip that is constantly being prevented from completing just before it completes.
Make sense ????
Some folks have successfully turned a stoppie into a rather unexpected, but a none-the-less, quite costly, front flip.

So, imagine riding along at 50 mph and NAILING the front brakes. I'd expect the *** end of the bike would go right over the handle bars. That would be a stoppie that was just poorly modulated.
Said another way .... A crash!!



Brian
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