front brake adjustment 94A Wombat

[944turbo]

Need a little help, I am trying to adjust the front brake on my soon to be finished 94A Wombat. I am finding that there is not much braking power after I adjust the front brake lever to 1/4", if I continue to tighten adjustment screws then the front wheel drags as the brake shoes are engaging. in all cases the amount of braking seems inadequate. Not sure what I'm doing wrong or if the cable needs to be replaced. I've moved the front brake cam lever also but it doesn't seem to make any difference. Thx for any advice

[hodakamax]

If you are not starting with new shoes I would try cleaning the old ones with brake cleaner and and lightly rough them up with sandpaper. Also clean and lube the cam.
They weren't great brakes to begin with. They will probably get better with running and stopping a few times. After they reseat you can probably adjust them with a little less slack. A new cable never hurts a thing. You might even need new shoes. Hope this helps!

Maxie

PS --I have the same model.

[Dale]

Refer to this post for information regarding centering your shoes with the hub...
viewtopic.php?t=438&p=1336

[944turbo]

I'll give cleaning the shoes another try, I rubbed them with some steel wool but maybe I'll use some sand paper instead, the drums looked pretty clean, the real issue seems to be when I clamp down on the hand lever I end up touching the hand grip with out enough pressure to fully engage the pads or at least without enough pressure to make the brakes work well, when I do adjust the cable enough to get the pads to really bite then the wheel no longer turns easily as the pads are engaged.

Maybe the old cable is stretched?

[socalhodaka]

Look up the back issues of the Resonator, Better Front Brake #1 Issue 1 Vol 12
#2 Issue 1 Vol 13
#3 Issue 2 Vol 1

Ed explains all the workings of the front brake parts and how to make the brakes works better.
Kelly

[944turbo]

Thanks, I looked at the first article already and I see how unbelievably wrong I put the front wheel on. LOL I'll look through all of the articles and get it right. My Wombat is till not ready for primetime but I'm getting close, maybe this weekend.

[dcooke007]

If you are using the original used brake shoes you need to make sure they are installed in their original location. Original used shoes will have a wear pattern that will not mate properly out of their original position. If you are not sure if you installed them in their original location you can swap positions and see if braking improves.

Danny

[Darrell]

I'll give cleaning the shoes another try, I rubbed them with some steel wool but maybe I'll use some sand paper instead, the drums looked pretty clean, the real issue seems to be when I clamp down on the hand lever I end up touching the hand grip with out enough pressure to fully engage the pads or at least without enough pressure to make the brakes work well, when I do adjust the cable enough to get the pads to really bite then the wheel no longer turns easily as the pads are engaged.

Maybe the old cable is stretched?

What may be happening is that the outer cable/sheathing is compressing while increasing the tension on the inner cable (brake application). I think modern quality cables have stronger and less compressive outer cables which minimize that issue of spongy brakes.

If you're using an old cable also check for kinks and knicks in the sheath.

[Zyx]

The symptoms described sound like shoes worn to the point that serious pressure isn't being generated. Not likely to be the cable. We recently discussed modifying the cam pads to give more throw. With adjustment of the cable made to allow only a quarter inch of slack max, there should be solid contact well before the lever bottoms. New shoes will help, but I have found that shoes worn to the point the cam won't make hard pressure between shoe and drum still leaves half the brake material unused. Wrap the cam pad in sheet metal. You will be surprised what this will do for effectiveness.

While the front brake was never the equal of a modern disc, I can still lock the front tire at speed with the old drum brake, so it can be made to work.

[944turbo]

Thanks again, I looked at the set up again last night, I really feel the issue is the cable which I will replace, the shoes are old but not much wear on them so there is a lot of material still there. That being the case the I should at least not be bottoming out the lever with the proper adjustments. Learnings as I go, the old resonator articles are great. Thx

[Zyx]

Thanks again, I looked at the set up again last night, I really feel the issue is the cable which I will replace, the shoes are old but not much wear on them so there is a lot of material still there. That being the case the I should at least not be bottoming out the lever with the proper adjustments. Learnings as I go, the old resonator articles are great. Thx

This is the exact symptom caused by brake wear. The original design intended that the shoes not be in contact with the drum when retracted, unlike most automotive drum brakes which are adjusted to light drag. Plus, the contour of the shoe was never a real match for the contour of the drum, so that only a part of the shoe makes contact when extended. It doesn't take long before the shoes don't make hard contact even with full lever deflection. No matter how spongy the cable, it should only take a half or three quarters inch cable travel to fully deflect the brakes. If you can adjust to no slack and still not have brakes at full pull, it doesn't sound like the cable. You would have to have pulled the outer housing really hard to stretch the wire coil of the outer housing to induce that much play.


Aside from re-arching the brake shoes, you can adjust the movement of the shoes in two ways. First, you can increase the diameter of the standing post on which the brakes shoes pivot. This will put the heel of the brake shoe closer to the drum which will then require less movement of the cam to make adequate contact. Second, and easier to do, you can wrap a strip of sheet metal around the cam flats to make the cam fatter. This will cause the cam to deflect farther physically than it does otherwise, and will bring the other end of the shoes into closer approach at rest, requiring less deflection to make contact.

It appears a common issue with stock Hodaka brakes that they don't work well for very long, and I have yet to see a Hodaka brake shoe that was worn all the way through the friction material. I have seen them either worn in the center only, or on one end only, which means the shoe was not in full contact with the drum along the length of the shoe. Look at your brake shoes to see if whatever wear there is is uniform along the length of the material. It probably isn't, and if not, the lever will never make enough pull to overcome the problem.

I wrapped my brake cams with sheet metal strips back in the late 70's because I couldn't afford new shoes. The brakes worked very well afterword, and we're still working nicely when I rebuilt them last winter. Not a bad fix for free, and I would try this before buying a new cable. However, if your cable has a cracked and broken plastic sleeve and is clearly stretched, it needs replacement as well. If you simply can not take enough slack out of the cable using the adjusters, dismount the brake arm and rotate it one spline, and try again. Only if you can feel the brake bind hard, and then you can still pull the lever from point of contact all the way to the bar would I suspect the cable, and even then it is a matter of degree. All cables have squish in them because they are small diameter, but the amount of compression should be small, not more than an eighth inch or so.

[Bullfrog]

the common problem with old cables (hmmm, any cable) is housing compression. None of us have enough strength (even with the extra leverage provided by the brake lever) to actually stretch the inner cable.
Ed

[944turbo]

Excellent info, I'll look at the shoes to see the wear pattern, I presume they are original shoes as the bike only shows 910 miles on the clock. I'll give the sheet metal on the cam a try, I moved the brake cam lever already to no avail.

You guys are great thx for your advice it is really appreciated.

[viclioce]

I'd also avoid using steel wool on your brake pads. They can smooth your pads and leave a more slippery surface to brake against. I'd ruff them up again with sand paper before using again no matter what else you do. ; D Victor

[Zyx]

the common problem with old cables (hmmm, any cable) is housing compression. None of us have enough strength (even with the extra leverage provided by the brake lever) to actually stretch the inner cable.
Ed

Ed, if I wasn't clear, I was referring to the outer housing, that if pulled hard, say, in a crash or snagged on a tree, it is possible to stretch the coils in the outer housing. Even new ones are not compression free.

[Zyx]

I'd also avoid using steel wool on your brake pads. They can smooth your pads and leave a more slippery surface to brake against. I'd ruff them up again with sand paper before using again no matter what else you do. ; D Victor

The funny thing about brake friction pads is that if rough and fluffy, they don't work until polished smooth. The more surface area in contact with the drum, the better. So while I also sand the pads to remove glaze, going over them with steel wool hurts nothing and speeds breakin. The drum I usually finish with 220 W/D paper.

[taber hodaka]

Its the old bald tire on ice theory. Wet brakes become polished, smooth and glazed but they just don't work, I scuff them up on the wire wheel on the bench grinder. -----------Clarence

[Zyx]

Clarence, sometimes I have trouble following your thoughts. The discussion was a general one regarding whether to use steel wool on brake pads, not whether wet pads are a problem. A bald tire of the correct rubber construction will in fact work on ice, as long as the ice is dry. It depends entirely on whether brake force on ice is predicated on affinity at the molecular level, or on physical interference caused by edges.

Brake pads work by generating heat. Friction is created at the face of the pad against the drum. The energy of the moving parts is dissipated through friction creating heat, so quite literally, the kinetic energy of the machine in motion is converted to heat.

The ability of the friction material to create heat is predicated on surface contact between pad and drum. Rough pad surfaces offer far less contact, generate less friction, and can't stop the machine as effectively as a good pad in full contact. All pads new or otherwise will break in from use. Once broken in, and working at their peak, the pad surface will be polished smooth because the break in will have essentially sanded off any surface fluffiness. This is not very hard to demonstrate. Take any brake working well. Remove the shoes and rough them up with a wire wheel or whatever pleases you. Reinstall and try them out. You will immediately notice that the brakes are now spongy and less effective. Continue using them repetitively for a few minutes, and the spongy feel will go away, and you will get your brakes back. Once they are working again, take them apart and look at the friction surface. It will be smooth and hard. This is the surface you are looking for.

So if you are rejuvenating old brakes, you can use what you want to remove glaze, which is caused by high heat and contaminants. But whether to leave the shoes rough or to smooth them down is up to you. If you do not also redress the drum surface, leaving the shoe rough only prolongs the break in period.

An analogy between brake shoes and tires doesn't work, regardless of the weather, because they perform two disparate functions. Brakes work by slipping surfaces against each other to create a binding force, converting energy from one form to another. Tires create a tractive relationship with the road surface, and work best when not slipping. So references to bald tires and ice may sound attractive to the ear, but misrepresent the dynamic.

[Bullfrog]

Brake force is a function of "normal force" (forces holding the surfaces in contact which are right angles to the surfaces) and coefficient of friction of the material(s) . . . water adds a complication to the coefficient of friction part.

Ed

[Zyx]

Of course water adds a complication, but the question is not how to dress a shoe to best shed water, and there are ways to do this, but rather how best to prepare a shoe for installation. The comment was made to scuff with steel wool, and the response was that doing this would make the shoe working surface too smooth or slick, and that a rougher surface was better. I took exception to that response, in that the proper degree of dress on a shoe actually will look smooth to the eye. There are naturally many other aspects involved. My only point is that it is not only not a crime to use steel wool, but it's use may result in a shoe that is more ready for use, with a shorter break-in period. I routinely use 220 W/D to dress the steel drum, AND to dress the friction pad. A wire wheel, in my opinion, is far too aggressive to use as it will quickly eat the friction material, and will result in an irregular surface, not to mention a surface that is far too fluffed up to be usable as is.

All anyone needs to do here is look at new brake shoes or new disc pads. They are almost uniformly finely sanded rather than fluffy or rough. There is a reason for this.

All of this is only tangential to the original post. Cleaning and dressing drums and shoes is a routine part of any brake service, and should be part of the hunt for our original post in finding good working brakes.

[junker2k]

postby socalhodaka » Tue Jul 28, 2015 10:30 am

Look up the back issues of the Resonator, Better Front Brake #1 Issue 1 Vol 12
#2 Issue 1 Vol 13
#3 Issue 2 Vol 1

If you take a look at these, Ed shows how to make the brakes work about as good as get without some major changes. I do know on my trials Hodaka I sand the brake shoes and drum before every event. If I go more than 2 events the shoes glaze over and don't work that well. I have never done anything to the brake cam in the backing plate but I have shimmed pivot post to make better contact. I start with a Coors can to make the shim stock. Also
if you adjust the brake lever on the hub so when you make full contact with the handlebar brake lever the hub lever is not quit 90 degrees to the cable. This is so you get the most leverage. They were never very good brakes but they can be made to stand you on your head if not careful. I hope this makes cents
Jack K

[Bullfrog]

Achieving truly useful braking power on the "old" style Hodaka front hub (pre-conical) will take more than cleaning/sanding off glaze/etc. - those things DO help - but the front brake will still be weak if you haven't:
- properley centered the brake backing plate on assembly (failure to do so results in component flex which reduces "normal" force between friction material and hub
- installed a newer, more robust cable than factory stock (newer, more robust cable will reduce cable housing compression which absorbs the power you apply by hand and results in reduced "normal" force between the friction material and the hub)
- installed the brake lever at the hub in an orientation which maximizes leverage when the brake shoes contact the hub (ideally, you want the cable and the lever to define a near right angle at the point when shoe/hub contact is made, to maximize applied leverage and "normal" force with the existing front brakke geometry)

. . . an additional opinion of mine (<-- note, carefully labeled "opinion") is that a longer front brake lever at the hub pointed forward is probably the best, most effective way to improve the front brake if all other factors have been handled in a craftsmanlike manner (additional leverage and improved internal cam actuation geometry on the leading shoe increases "normal" force at the friction material/hub interface). However, this is not an easy modification since a new cable housing end socket must also be designed/built . . . but it can result in a front brake nearly capable of providing "stoppie" power (front wheel wheelies).

(my more than 2 cents worth) Ed
PS: Going fishing - see you again in a few days.

[Bullfrog]

DOH! I should have included the following:
- proper arcing/fitting of shoes to hub (reduces flex and results in increased "normal" force between the friction material and the hub - when the shoes are dressed to make full contact, the shoes aren't forced to flex to allow the contact -- and flex is bad)

Ed
PS: Still going fishing - see you in a few days.

[hodakamax]

Ed, any fish stories?

Max

[Bullfrog]

I got to put a check mark on one of my bucket list items. Caught several good size trout on a mouse fly!

Ed