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Robert_Adams

01 426 brake prob

13 posts in this topic

My friends son races MX and we have been having a reoccuring broblem with the front brake. FYI It has the larger front disk kit on it.

The caliper slider bolts bend fairly often and part of the problem is that only one is available from the dealer. We take the pin out chuck it in the lathe and hit it with a hammer and block of wood until it is straight.

Are we the only ones having this problem if not what is the fix.

It has been a great bike so far. The only problems we have had is the front brake dragging and the throttle sticking.

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Interesting post I must say.

Well, let's see.

My first recommendation would be to stop riding this bike. If your brakes don't work and the throttle sticks, the rider is risking their life and the safety of others. And I'm not joking.

The throttle may be sticking due to dirt or build up under the throttle tube, especially if the bike has been crashed on the right side and the grip was torn, allowing dirt to get in.

Or, the throttle is sticking because there is not enough slack between the two pull cables. Grab the manual and set the cables to spec and clean out any dirt under the tube.

As for those brakes - a dragging front brake means heat, and plenty of it. Most likely you have done more damage than you can imagine by allowing this to occur. The bit about the bolt bending makes me very suspicious that the oversize kit was never installed correctly, or that someone has attempted to modify the brakes and never got the thing back to together as designed.

That bolt, by the way, does not take a load from the pads (the caliper does that). If it's bending, and you keep bending it back, it's going to snap. If it’s the only thing holding those pads in place for whatever reason, you could have total brake failure. See opening recommendation.

I don't think you'll find your brake answer here unless someone has installed a brake kit incorrectly and could share similar experiences.

You may want to visit the dealer.

Please be careful.

DaveJ

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The problem with the throttle sticking was a problem at the carb itself and has been fixed.

The kit was installed correctly and everything worked fine for a good while. When it was dragging the first time everything looked just fine and he even took it to the dealer and had them take a look at it and they couldn't find anything either. Let me specify what I mean by dragging I don't mean as in you can't turn the wheel it is a light drag that is only noticed when spinning the wheel in the air.

I know what dragging brakes do cause I am also an ASE master tech.

So we disassembled everything and looked it over again. We then took the two slider pins out and chucked them in the lathe and found that the long one was bent about .015. The only solution short of buying a new caliper is to bend it back or to make a new pin (which we did).

I'd like to see someone install the kit incorrectly cause I don't know how they could. Everything only goes on only one way.

Yes I understand that the caliper takes the load from the pads but then it is transferred to the two bolts/pins that the caliper slides on. It puts more pressure on the long one because the short one has a rubber insulator in the caliper.

To answer Ric j yes it comes with a caliper relocation bracket.

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You relocated the caliper, and are using a different rotor.

I'm going to put 2 and 2 together and blame your braking kit.

Have you tried the stock rotor and caliper

location?

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Robert,

I thought you were talking about the bolt that holds the pads in. Thanks for clarifying that.

So if the slider bolts are bent, then most likely the caliper is not in the proper position. Meaning that it is being forced to slide out on the bolt edge and the resulting torque is bending them.

When assembled, the caliper should be nearly all the way onto the bolts.

Take a look at the positioning of this and let me know what you find.

Perhaps the adapter was made incorrectly, is backwards, or there's a dish on the rotor.

Then we can begin to discuss dragging brakes.

DaveJ

BTW - how were you able to order just those slider bolts? I thought the fiche shows only the complete caliper assembly?

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I'm thinking the kit also. Try this for an idea.

Since there is more leverage on the caliper because of the larger rotor I wonder if it is just enough to put more force than the caliper and parts were designed for resulting in a bent slider bolt.

I got the dial indicator out and checked the rotor for flatness in several spots and on both sides and it passed with flying colors.

As for all the parts lining up there is nothing wrong there either. The caliper is seated where it should be on the bracket.

We were able to find the short pin that has the rubber seal that it slides in but not the other one.

I may just make up a few on the lathe to keep as spares or have a friend at a machine shop make a few up cause the lathe i'm using can't take big cuts.

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If it were me, I'd put the stock brake kit back on and try it. You seem to be doing an end-around, know what I mean? To get better braking , you could replace the front line with a "CR" style steel piece, use EBC greens, and then try a different O.S system. I'm in total agreement with what someone else posted about the safety aspect. Messing around with such a critical component, is not worth the possible ramifications. $.02 (mine)

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FastKevin has a very good point. With a proper line, (such as Fastline) race pads (such as DP MX-PRO), and a well-maintained caliper and disc, it's really hard to do one better than the factory setup.

However, the extra diameter should not bend those pins. Perplexing.

Let us know if you find any other clues.

DaveJ

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Im wondering if the caliper is properly floating on the pins? If its binding...? Is it possible to put the disc on the wheel backward? Just a thought Im not familiar enough with the disc itself to know, not having to change or fix the part yet.

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Robert I had the same problem with mine. Talon Engineering the pepole who make Talon hubs are the importer in the UK for Braking. I told them of my problems and they tested a few of the same and found them to drag also. So they machined me a billet one to there specs, sent it to me free of charge and it is superb. They then sent all of there stock of crappy brakets back to Braking in Italy. Maybe this will help you.

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I doubt if this is your problem, but....

The last time I put my front wheel on (with stock brakes) the front brake was dragging and the disk was forcing the floating caliper toward the wheel.

I couldn't see how I could mess up a simple thing like putting a wheel on, but I did.

It turns out that the left axle bushing is a bit shorter than the right (it even looks different), but I had them switched, causing the disk to drag on the caliper. :)

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