Yamaha TRX850 Enthusiasts Forum

Here's the measurements etc I worked out when I did this...

1. If the wheel is straight out a YZF, you'll need to change the bearings for TRX ones as the diameter of the TRX rear spindle is less than the YZF's. Outside diameter of both bearings is the same.

2. You can use the TRX wheel spacers, but they need turning down as the YZF hub is wider. Turn the 'tophat' (right in the photo) one down to 13mm and the 'donut' (left in the photo) one down to 10mm



3. The TRX sprocket carrier, cush drive rubbers and axle can all be used on the YZF wheel. The sprocket (providing you've got a standard one with the 2mm indent running round it) needs to be removed and 'flipped over' so the indent is on the inside: this moves the sprocket inwards by 2mm so the chain run is straight. If you've got an aftermarket flat sprocket like renthal, you may need to get into machining down either the wheel or the sprocket carrier. I didn't.



4. Standard YZF disc is the same so can be used, but I needed to put a 1mm washer on the caliper bolts, between the caliper and the caliper carrier to move the caliper over to stop the back brake binding. This might be because I fitted new rear brake pads at the same time.

Here it is all fitted. This setup gives a straight chain run, and plenty of clearance of the bigger 180 rear tyre on both sides of the swingarm and of the standard chain guard, although it does position the rear wheel slightly off-centre by a few mm, but that doesn't matter.



Only other thing to note is that you can't use a standard TRX hugger with this bigger tyre and wheel.

Also, the 180 rear tyre has a bigger diameter than the standard 160, so to compensate, I worked out you need to fit a 16 tooth front sprocket instead of the standard 17 tooth one, just to get the bike back to a gearing ratio close to how it is as standard.

Lots of debate as to whether this mod is worth it: is handling better, is it just 'bling', does it give better tyre choice etc etc which I don't want to get into here, but I think it looks good, and the bike's done a few track days with this set-up and it seems to work well.

Cheers,

Dave.

weather its worth it or not its a credit to you, it does look a proper job and i like the yellow wheels (i can feel some spraying coming on ) well done

Agreed, it does look good

Great information 4 who is thinking of doing it 2

And it DOES look FAB

Greetz
Gerben

As an YZF ánd TRX owner I'm espcially interested in this kind of topics.
First of all, well done!

But... what do you mean with the wheel being a couple of mm's off-center?
It surprises me that the sprocket only needs to move 2 mm, because the wheel should be ~10 mm wider on each side (180 - 160 / 2, right?)

Tarwetijger wrote:As an YZF ánd TRX owner I'm espcially interested in this kind of topics.
First of all, well done!

But... what do you mean with the wheel being a couple of mm's off-center?
It surprises me that the sprocket only needs to move 2 mm, because the wheel should be ~10 mm wider on each side (180 - 160 / 2, right?)

No. 180 and 160 are the tyre widths. The rim itself is half inch (approx 12mm) wider. The difference in the hubs is less.

I'll leave Dave to explain the detail

Wheel at rim is about 12mm wider as phuk sez. From memory, the HUB on the YZF was about 7 or 8 mm wider than the TRX. If the two spacers are turned down the the measurements above, this allows for the wider hub but also offsets the wheel by about 2 mm to the right, and with the sprocket 'flipped' to gain another 2mm this lines up the chain exactly. I was trying to avoid any machining of the wheel itself at all.

excellent and complete guide.. well done !

Its a winter project, along with a couple of other things.

Dave E

Hasn't it been a winter project for teh last 3 years

Yep, but I've been busy moving house and bashing that about, (new kitchen and utility floor before xmas). Finished all the big jobs now.

Dave E

Nice work dave, i like threads like this.

I notice you kept the trx arm and wondered if you ever dabbled with the yzf arm??
I ask as im hopefully going to get started on fitting my yzf arm this weekend work permitting but id like to retain the trx wheel. This may sound daft but i had the trx wheel polished and painted and has a spanking new bt020 on it, i bought a yzf wheel but it would need all that doing to it to be in a useable position. I was after opinions on whats going to be my best option (not one to take the easier option), i know the trx wheel will require spacers as its narrower than the yzf arm.
My biggest concern is what to do with the spindle as the trx one is too short for the yzf arm and the yzf one cant be turned down to fit inside the trx wheel as its hollow!!! Didnt know if anyone knew of a spindle that has the trx internal dimensions but the length of the yzf spindle.
Any suggestions??

Obvious solution would be YZF spindle, new bearing for TRX wheel to fit YZF spindle and some spacers.

I'd agree with Phuk: retain the YZF spindle, and use the bearings out the YZF wheel to put into the TRX wheel. These have the same outside diameter as the TRX ones I believe, so will fit in the TRX wheel, but have a larger centre hole for the larger YZF spindle.

As you say, you'll need longer spacers either side, as the hub on the trx is narrower than on the yzf.

Chain should be ok, but what you doing about lining up the rear disc with the caliper? Presumably spacers between the caliper and caliper mount, to move the caliper over a bit?

The only difference in the arms is that the YZF one is braced, but the TRX arm is not really prone to flex: you sure you want to do this swap if you're not also gonna get the "benefit" of the wider rear wheel/tyre too?

Dave.

PS, if you're not using the YZF rear wheel and you want to sell it, let me know: I'd be interested!

.......further thought:

You'll will need to get a new internal spacer for the TRX wheel too: the tube that fits between the bearings inside the wheel hub to prevent lateral compression of the bearings by the wheel spacers when you tighten the axle nut up.

The TRX one will be too small internal diameter to take the thicker YZF spindle, and the one out the YZF wheel will be too long for the narrower TRX hub.

This may be where the project falls down: is there enough width inside the TRX wheel hub internally to take the larger diameter spacer between the bearings that the larger diameter YZF axle will need?

Dunno!

Dave.