Thundercat rear wheel

davesax36 · Sep 6, 2015

Ok. Here are the videos of my rear wheel I made before it got too dark.

My bike currently turns left if I let go of the bars. Any ideas are welcome.

Also, the wheel came with a machined brake caliper arm. It's probably half the thickness at the axle as a stock one. I don't know if that offset is the problem or if it's something in the wheel. My u-joint seemed noisy when I started it up today, and the final drive seemed loud, too. I don't know if that's normal or not.

https://youtu.be/m1ssmVD5isE

https://youtu.be/Hw2Lgp1R4Sg

https://youtu.be/jzVAhKSIceY

https://youtu.be/_u4csHuqZgw

Traumahawk · Sep 6, 2015

davesax36 said:
Ok. Here's the video of my rear wheel I made before it got too dark.

My bike currently turns left if I let go of the bars. Any ideas are welcome.

https://youtu.be/m1ssmVD5isE

hey Dave....the video is marked private.

davesax36 · Sep 6, 2015

Try it now.

Traumahawk · Sep 6, 2015

It looks like there is a wobble. Either the run out of the wheel isnt what it should be....a bad bearing? Maybe its me.....but there sounds like there is a sound coming from there wheel as it is spinning....do you hear anything there?

davesax36 · Sep 6, 2015

It sounds like rocks...Maybe I just need new bearings?

Sounds weird in the u-joint area, too, though.

Traumahawk · Sep 6, 2015

I would try the bearings and seals first......then u joint if you had to. The swing arm is hollow and noises will travel.

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Dorney · Sep 6, 2015

The wheel doesn't seem to have much side to side. But it does look like it has a flat spot up & down.

Dave

davesax36 · Sep 6, 2015

Dorney said:
The wheel doesn't seem to have much side to side. But it does look like it has a flat spot up & down.

Dave

Yeah. I only notice a vertical issue at 35mph steady cruising. I really don't see an unacceptable lateral runout issue, but I don't know how old this wheel is anyway. I'll look up some bearing numbers and see if I can get that all done. I'll update either way.

Thanks, guys.

MaxMidnight · Sep 7, 2015

Do you mean Thundercat as I seem to think they were chain drive?
If it was the former then I would check the wheel alignment front to back and see if there is excessive off-set to one side.
Note that small amount of off-set is normal. That said provided the radial axis of the wheels are in line I guess it would need to be a lonf way out before causing an issue such as you describe. I would, however, expect to feel a different turning characteristics left to right.

As others have noted there is run-out on the wheel/tyre which needs to be sorted otherwise you will start to see strange wear patterns on the tyre.

1967vmax · Sep 7, 2015

so you have an aftermarket rear wheel and it tracks to the left my rc wheel did the same thing it is due to the offset in the wheel the only fix i found was Morleys swingarm he added the offset in the swingarm so the bike tracks straight.

davesax36 · Sep 7, 2015

MaxMidnight said:
Do you mean Thundercat as I seem to think they were chain drive?

If it was the former then I would check the wheel alignment front to back and see if there is excessive off-set to one side.

Note that small amount of off-set is normal. That said provided the radial axis of the wheels are in line I guess it would need to be a lonf way out before causing an issue such as you describe. I would, however, expect to feel a different turning characteristics left to right.

As others have noted there is run-out on the wheel/tyre which needs to be sorted otherwise you will start to see strange wear patterns on the tyre.

It's the one on the chat.co.uk site. I see lots of pics that match when I search Thundercat vmax pictures on google. I'll take a few pics later when I'm out that shows the offset and all that.

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Fire-medic · Sep 7, 2015

I doubt many riders could sense any amount of offset. Running at anything but racetrack use, a modest offset should not interfere w/the use of a bike. As long as the vertical plane of the two wheels is consistently parallel, handling should be relatively unaffected. Some stock bikes come w/offset, I'm sure contacting someone like Computrack for some additional info on the subject would leave you amazed at how many run f-r (front-rear) offset. I think the vintage British bikes often ran offset.

Of course, the angulation of either wheel to the right or the left, and in 'worst-case-scenarios,' one angling right and the other the opposite direction, should cause weird wear patterns, scary handling, and hopefully, be the exception rather than the rule. A good reason for setting your chain-drive bike measured from the swingarm pivot on each side to the rear axle center, so the measurements are the same. A string looped around the f-r tires, a few inches off the pavement, and getting the wheels to touch on their leading and tralining edges, for each, is one method of also doing the same thing.

davesax36 · Sep 7, 2015

I'm hoping that bearing replacement solves it. It sounds crunchy back there.

I also don't think any offset that allowed my wheel to be as centered as it is could cause an alignment issue bad enough to change lanes two or three seconds after letting go of the bars.

Traumahawk · Sep 7, 2015

davesax36 said:
I'm hoping that bearing replacement solves it. It sounds crunchy back there.

I also don't think any offset that allowed my wheel to be as centered as it is could cause an alignment issue bad enough to change lanes two or three seconds after letting go of the bars.

Yep.....like you and I discussed....I think you have other issues than just offset. My rc wheel has a noticeable offset to the right and still tracks true.

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Miles Long · Sep 7, 2015

davesax36 said:

I'm hoping that bearing replacement solves it. It sounds crunchy back there.

I also don't think any offset that allowed my wheel to be as centered as it is could cause an alignment issue bad enough to change lanes two or three seconds after letting go of the bars.

Click to expand...

Maybe not caused by the back wheel at all, Dave?
Aren't you running a single disc arrangement on the front wheel?
If so, does it tract towards the disc side when you let go of the bars? Maybe the brake pads are grabbing a tad?
If not, I'm with Medic with doing the string alignment testing - not so much to detect offset, but to be sure the wheels and tires are tracking parallel. Perhaps your forks/triple trees have to be aligned.
Cheers!

davesax36 · Sep 7, 2015

Disc is on the right, bike turns left. I'm not sure if that's even a reason, but I'm sure it's possible. I'm also wondering if it's the way that windshield mounts. It could be just a bit tweaked and pulling when not stabilized by hand/bars. I'm going to try the string thing when I go over to the bike at dinner time. I hope I can figure this all out and get some benefit for other guys instead of just me.

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mabdcmb@yahoo.com · Sep 7, 2015

How would a slightly dragging disc make the bike turn? The disc would be stopping the whole wheel. Not just one side of it.

davesax36 · Sep 7, 2015

[email protected] said:
How would a slightly dragging disc make the bike turn? The disc would be stopping the whole wheel. Not just one side of it.

Yeah. It's gonna be a while before it gets worked on.

davesax36 · Sep 13, 2015

Ok, so maybe I don't have a thundercat wheel... or even possibly a Divvy wheel. Here are some pics of the pieces. You can see how much the brake caliper arm has been cut down. I can't get the wheel to move laterally, but there may be a bit of play when I try to rotate it like a spinning coin. Just a bit, but that may be the sign that one or both bearings are going/gone. Offset is also pretty plain to see, but doesn't look like more than many I've seen. Anyway. Thanks for looking, guys.

one2dmax · Sep 13, 2015

Looks like a lot of side to side runout (and a lot in the tire too). BUT, the offset looks like it's WAY to the right which will make it turn left very easy and harder to the right. Almost like you have to lift the bike up and then lean it over.

The 5.5" width would normally have the rim much closer to the swingarm on the left side.

You can mark the center of the tire with the 17" wheel somewhere on the bike (use a plum-bob) and then do it again with the stock wheel/tire. I suspect you're around 1/2" off center to the right.

Thundercat rear wheel

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