Zongshen RX3: Larger Rear Wheel Considerations

[SpudRider]

For a lot of riders, the stock, 15-inch rear wheel of the Zongshen RX3 will work great, especially if CSC imports knobby tires for the rear wheel.

http://www.chinariders.net/showthread.php?t=14096

However, one will have a much greater selection of readily available tires if the rear wheel is increased in size by lacing either a 17-inch, or 18-inch rim to the hub. Once the rear wheel is enlarged, one also has the option to increase the size of the front tire to 21-inches. Of course, several factors need to be considered before increasing the size of the rear wheel, or both wheels.

Lacing a larger rim onto the stock rear hub is not a difficult task. I have built several custom, 18-inch rear wheels for current owners of the Zongshen 200GY-2 (Sierra). However, the Zongshen RX3 has two different, rear hubs, and we must consider the options for both of them.

The original rear hub is available for sale, and it probably employs KTM sprockets.



These sprockets are available in a wide range of sizes, from 38-52 teeth. This variety is good, because a larger rear wheel will require a larger rear sprocket, if we wish to maintain the final drive ratio to the rear wheel.

The updated, cush hub on the RX3 bikes sold by CSC is a very nice improvement. However, the new hub employs a sprocket similar to one used by the Zongshen 200GY-2. This sprocket is much less popular, and quite possibly is not available with such a wide variety of total teeth. If larger rear sprockets are not available, one cannot increase the size of the rear wheel without also raising the final drive ratio of the transmission.

If one reverts to the original hub, I don't see any problems with lacing a larger rim. However, I truly value a cush hub on the rear wheel, so we will have to wait and see which sprockets fit the cush hub.

If we could get some measurements of the rear sprocket from CSC, we could begin to research the matter more thoroughly. Lacking those measurements, I can only speculate. Right now it seems the cush hub probably employs something like a JTR1826 rear spocket.



Unfortunately, the largest JTR1826 sprocket only has 44 teeth, and that might not be large enough.

The Russian Minsk TRX 300i employs the older hub, and has a 17-inch rear wheel. If the Russians aren't having any problems with the wheel bearings, it might be better to switch to the older hub, if one wants a larger rear wheel.

If one prefers the updated, cush hub, it might be best to stick with the 15-inch rear wheel, and accept the smaller variety of available tires. After I receive my RX3 motorcycle, we will definitely know more about our options.

[Weldangrind]

A cush hub is nice, but only if you can swap the bushings with higher quality parts, like OEM Honda. If not, I'd stick with the solid drive and all of the sprocket options that go with it.

I'm looking forward to your report, once you've had a chance to remove the sprocket and measure it and the bushings.

[SpudRider]

Originally Posted by Weldangrind

A cush hub is nice, but only if you can swap the bushings with higher quality parts, like OEM Honda. If not, I'd stick with the solid drive and all of the sprocket options that go with it.

I'm looking forward to your report, once you've had a chance to remove the sprocket and measure it and the bushings.

I suspect this is the same cush hub which is stock on the ZS200GY-2, Sierra motorcycle. If so, it has a very nice, very substantial rubber insert.

Here is a link to the hub, with the rubber cushion insert.

http://item.taobao.com/item.htm?spm=...74&ns=1#detail

Here is the sprocket holder assembly which fits into the cush hub.

http://item.taobao.com/item.htm?spm=...36&ns=1#detail

Here are two links to the replacement, rubber cushion.

http://item.taobao.com/item.htm?spm=...26&ns=1#detail

http://item.taobao.com/item.htm?spm=...70&ns=1#detail

This cushion hub is very high quality, equal to anything produced anywhere in the world.

This cush hub greatly extends the life of the wheel bearings, both sprockets, and the drive chain. In addition, it greatly smooths the power transfer to the rear wheel under all riding conditions.

[Weldangrind]

Ah. I visualized the typical old Honda round bushing style. This is much better.

[SpudRider]

Yes, it is well manufactured cush hub of high quality. Honda XR650L owners who want to install an aftermarket cush hub of this quality are paying over $500 for the hub alone.

http://www.radmfg.com/Cush-Series-RE...radh-eq-1r.htm

Of course, the 4-inch piston in the XR650L produces a lot of torque, which punishes the entire drive train, and frequently strips the splines from the counter shaft. Although it is a very nice feature, I doubt the cush hub is necessary for the RX3 engine.

For whatever reasons, Minsk ditched the cush hub on the TRX 300i when it specified the 17-inch rear wheel. I'm betting the 17-inch rear wheel offered by CSC will also not have the stock cush hub.

The easiest, and least expensive option might turn out to be a reasonably priced, 17-inch rear wheel offered by CSC. Such a wheel might cost the same, or even less than the combined cost of custom spokes, and a new rim for the stock cush hub.

[SpudRider]

The original rear wheel, sans cush hub, is undoubtedly lighter than the newer cush hub. This will result in a lower unsprung weight on the suspension, and slightly quicker acceleration. Here is a link to the original rear wheel.

http://item.taobao.com/item.htm?spm=...id=38663884322

Perhaps I am wrong, but looking at the photograph, it appears the original rear wheel is equipped with a 17-inch rim.

[SpudRider]

Originally Posted by Weldangrind

If that's the case, then the 17" wheels are surely available directly from China, which certainly takes work out of the equation.

It appears you are correct once again, Mr. Weldangrind.

[Weldangrind]

Originally Posted by SpudRider

The easiest, and least expensive option might turn out to be a reasonably priced, 17-inch rear wheel offered by CSC. Such a wheel might cost the same, or even less than the combined cost of custom spokes, and a new rim for the stock cush hub.

As long as it's an alloy rim. I'd be choked to receive a steel rim if I paid for an upgrade.

[Weldangrind]

Originally Posted by SpudRider

The original rear wheel, sans cush hub, is undoubtedly lighter than the newer cush hub. This will result in a lower unsprung weight on the suspension, and slightly quicker acceleration. Here is a link to the original rear wheel.

http://item.taobao.com/item.htm?spm=...id=38663884322

Perhaps I am wrong, but looking at the photograph, it appears the original rear wheel is equipped with a 17-inch rim.

It looks like a 15" to me, especially when compared to the 18" front wheel.

[SpudRider]

It's tough to discern a 15-inch rim from a 17-inch rim by looking at a photograph. You are probably correct. The writing on the tire looks more like '130/90-15' than '130/70-17'.

[Weldangrind]

I tried to expand the image as well, but it's too hard to see on my laptop monitor.

[Wolftrax]

Originally Posted by SpudRider

The easiest, and least expensive option might turn out to be a reasonably priced, 17-inch rear wheel offered by CSC. Such a wheel might cost the same, or even less than the combined cost of custom spokes, and a new rim for the stock cush hub.

I can't remeber where I heard it or maybe I imagined it, but I think I heard $250 USD for th 17" option from CSC. If this is the case I think I'll be the proud owner of 2 sets of rear wheels.

[SpudRider]

Originally Posted by Wolftrax

I can't remeber where I heard it or maybe I imagined it, but I think I heard $250 USD for th 17" option from CSC. If this is the case I think I'll be the proud owner of 2 sets of rear wheels.

I would like to see a super-special, ultra-low price for early-adopter, 17-inch rear wheels from CSC.



At the right price point, I think two pairs of wheels would be great. One could install the 15-inch wheel with the cush hub for extended riding on pavement, and swap in the 17-inch rear wheel when planning to do more off road riding.

[SpudRider]

The Chinese prefer to copy, rather than re-invent a wheel. For example, the rear wheel for the ZS200GY-2 is from a Kawasaki BN125 Eliminator. I hope the Chinese copied either a KTM, or Honda rear wheel. If so, one can purchase a very nice, anodized, alloy rear hub from Rocky Mountain ATV/MC for $100.

https://www.rockymountainatvmc.com/p...b-Rear?v=11296



Purchase a Tusk Impact Rear Rim and Spoke Kit, and you can lace up a beautiful, 18-inch rear wheel for about $213 in parts.

https://www.rockymountainatvmc.com/p...ke-Kit?v=11296



Then you can install a Primary Drive, rear sprocket for $20. These sprockets are available in sizes 48T-53T, which is perfect.

https://www.rockymountainatvmc.com/p...rocket?v=11296

[Weldangrind]

Originally Posted by SpudRider

I would like to see a super-special, ultra-low price for early-adopter, 17-inch rear wheels from CSC.



At the right price point, I think two pairs of wheels would be great. One could install the 15-inch wheel with the cush hub for extended riding on pavement, and swap in the 17-inch rear wheel when planning to do more off road riding.

That's an excellent idea. The street-oriented patterns that are commonly available for 15" rims make that a good choice.