Mount Dual Piston Caliper Behind Fork

mrtwowheel

Honda Etched On Brain
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This is what I wanted to do on my '74 TX650A. I wanted to swap the forks side to side, put the axle in backwards, change the hardware around so that the caliper can be mounted behind the right fork.
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I saw no problems with doing this. A banjo bolt would even work to replace the steel line and fittings.

I swapped the forks and put the wheel on with the axle and all backwards. After doing this the wheel was about 1/4" offset between the forks and the caliper was not aligned with the rotor. Something was definitely different when swapped side to side. I checked the rim to hub difference side to side, no difference there, the rim was centered to the hub. Then I thought about the right spacer and the speedometer drive that actually is a spacer too. Straight edge across speedometer drive and measuring to the hub flange, HEY, the speedometer drive was 3mm lower than the other spacer. Thinking 3mm plus 3mm is damn close to 1/4", that must mean something.
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I put 3mm of bushings between the left fork and the speedometer drive. I had about 3mm gap between the other fork and spacer before, so, I mounted the wheel with NO gap. This 3mm change put my wheel exactly in the center of the forks, the rotor is centered in the caliper, and the castle nut and cotter pin are just right too.
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Above, no gap now, or I could take 2-3mm off of that spacer, but I think it's just right now.

Comments please, pelt me with rocks and garbage.

Scott
 
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Good work! Watch that the speedo drive doesn't spin, it shouldn't but..........
 
Have you ridden the bike like this yet? I think there's going to be an issue with the speedo drive. It's spinning in the opposite direction now.
 
Have you ridden the bike like this yet? I think there's going to be an issue with the speedo drive. It's spinning in the opposite direction now.

No, speedometer drive is still on the left side going in the same direction. I've had more than a few Honda's with no positioning dogs on the forks for the speedometer drive, the angle of the cable drive is positioned when assembling, most of those Honda's still had the positioning dogs on the speedometer drive from yesteryears but no matching dogs on the forks.

Scott
 
Easy.....One (maybe both) fork tube has a slight bend. As a test, Loosen the triple clamps and axle clamp on the tube that has the lower that CLAMPS to the axle (NOT axle nut side) and rotate the tube. Watch to see if the gap changes. The same test can be done on the other side with the axle nut loose and the clamp side tightened.

If you have a pair of VEE blocks and a dial indicator, you can also dis assemble and check that way. But if you have those tools, I'm sure you would know how to use them for this.
This was done with a wheel that was trued and forks that had already been disassembled, cleaned and checked for straightness. To offset the wheel and hub or tweek/bend any other part would have been the WRONG thing to do.

Scott
 
Kinda thinking out loud; is the speedometer drive still CLAMPED into position by the axle nut, or is it it now just filling the space. between wheel and fork? I think it's now the former, if so you WILL need a positive locator for it.
 
I've had bikes in the past (don't remember which ones) where the speedo drive housing was free floating. You could grab the cable and rotate it easily. Often wondered what kind of damage the cable would do if it ever locked up....:yikes:.... but, never had one fail.
 
I don't believe I offered ANY fix, so how can anything I mentioned be "the WRONG thing to do"?

This really is VERY simple. If you are mounting a caliper on the slider that clamps to the axle and the caliper doesn't align, then the fork tube is bent to a small degree.

What I offered was a simple TEST to check that.
I'm not asking the question that you think I'm asking, please read the whole thread.
 
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Above, this part of the speedometer drive housing bears against the fork leg in my configuration, or against the shoulder on the axle in stock form.
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Above, this part which is also part of the speedometer drive housing bears against the inner race of the wheel bearing. A free floating speedometer drive on my bike would be a loose axle, whichever way the axle was inserted.

Scott
 
I could disassemble everything and mock up the axle and spacers to show the 3mm difference when the axle is inserted both ways, but I'd rather not. I'm very certain that this is a change that was done right and will work and be safe. I'm a happy guy.

Scott
 
On a 36 spoke hub......
I measured from the outside of the spaces to the flanges..........then from the face where the rotor sits to the flanges............and from the outside of the spacers to the Hub rotor face

Rather than post a whole series of pics showing all the differences in the first 2 above.....................This is where the 3mm difference is...............
IMG_0436 copy.jpg IMG_0438 copy.jpg
Set up to show how i measured...........couldn't take pics of the actual act
IMG_0436 copy.jpg
IMG_0438 copy.jpg
 
Kinda thinking out loud; is the speedometer drive still CLAMPED into position by the axle nut, or is it it now just filling the space. between wheel and fork? I think it's now the former, if so you WILL need a positive locator for it.
My bad! Finished thinking this through; and of course, the axle nut still pulls everything from spacer to speedo drive together into a non-turning unit.
front axle wheel reversed.jpg
 
Take a look the speedo drive is much thicker than the spacer there's a lot going on on left to right spacing. need to set up some gauges but there appears to be a difference in fork tube centerline to inner axle flat 'tween left and right 34mm forks. The lawnmower re-engine parts fabrication project is taking precedence this morning..
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I'm headed out to the shop. Today is a day to deal with parts and tools, not a good day to deal with peeps. Should have read my horoscope.

Scott
 
OK, in an effort to take that 3mm difference out of the abstract and put some real eyes and virtual hands on the subject, here goes. Forget the other fork for now, this demonstration will only involve the fork with the axle threads and nut. Yes, this is all in a perfect world with good triples, straight forks and other good unmolested parts.


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Above is all of the parts in line as they would be in stock configuration. Most importantly notice the spacer tightened against the fork leg with the axle.
DSCN4672.JPG

Above is all of the parts in line with the forks swapped side to side. Notice that the speedometer drive is now tightened to the fork leg with the axle.

There is a 3mm placement difference of the parts in the first picture compared to the parts in the second picture. That is because there is a 3mm difference between the spacer and the speedometer drive.

The wheel is 3mm different in pic 1 compared to pic 2

The rotor is 3mm different in pic 1 compared to pic 2

My 3mm spacer/bushing puts the wheel and rotor back into the right positions.

Scott
 
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