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Discussion Starter · #1 ·
I finally got all the pieces together for my ZRX swap. I want to give a shout out to MickMaguire and others before me who really pioneered this swap; the old threads were a great resource. I thought I would share my experience as well as a ride report for anyone interested in the swap.

All in all it was very straight forward, here is the breakdown of the approximate costs that I found on eBay.

  • '02 ZRX1200 Forks (in need of fork seal replacement) - $125
  • ZZR wheel with tires and rotors - $115
  • 04' R1 brake calipers - $90
  • Brake caliper adapter plates - $130
  • ZRX Axle - $25
  • ZRX speedo gear - $20
  • ZRX brake calipers with lines and master cylinder - $60

This definitely took some hunting to find the forks and wheel for these prices however it can be done.

Everything went in smooth and it was quite simple until I got to the brakes and more specifically the rotors. A ZZR wheel will work with the ZRX fork however the ZRX brake setup expects a 310mm rotor where the ZZR comes with a 320mm. I spent a lot of time on the zrxoa.org forum trying to figure out what would be the best solution and I ended up going with the adapter and R1 calipers because it expects a 320mm rotor, which is cheaper to replace, as well as it was a little bit cheaper than going out and purchasing new rotors.

The other tricky bit was the brake lines. I went through quite a few iterations but I ended up using the stock line with a line from a Trophy and did a double banjo bolt up at the master cylinder. This end up with the cleanest lines and kept everything out of the way.

Also keep in mind that with this setup you are going to have to get new rear wheel spacers made up as there is some offset in the stock setup. I already had done the ZRX rear wheel setup so I ended up having to move the wheel more towards the right hand side of the bike. I ended up machining a slight bit of the brake caliper mount to get the rear wheel over enough.

--Ride Report

The first thing I noticed was walking the bike and at slow speeds it felt a bit tippy however I guess this is understandable due to the increase head tube angle. The most noticeable improvement surprisingly was not the brakes, however they are awesome, but it was the small bump compliance was out of this world. The roads around here are horrible and that is putting it nicely, but the forks made it buttery smooth. I didn't notice that significant of a difference in the riding position however after 30 minutes of riding I noticed my back was getting a bit sore so there obviously some difference. Other than that it is going to take a bit of getting used to with the new geometry but over all I am very happy with the swap and for the cost versus how much I think I can get from selling the stock parts I will be in a good place. I have some before and after pictures but if anyone has any questions about any aspect of the swap I can do my best to answer them.
 

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questions

I love the way the ZrX forks level the bike out. It really improves the aesthetic lines of the bike. I am curious. What are the size differences in the two forks (zrx and stock tbird) I know they are both 43mm but is the length (height, I don’t know which is the correct term) smaller than a tbird’s? Did you need to change the wheel? I like the spoke wheels. They add to the retro look. I’ll stop with those questions for now.
 

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Discussion Starter · #3 ·
The ZRX forks are shorter than the stock Thunderbird forks. This causes the head tube angle to be greater which adds to the sharper handling and the aesthetic change. As far as the wheels I don't know if the axles are the same diameter but the main problem is that the ZRX calipers are setup for a floating rotor. I know the stock is a solid rotor so you need to get a new rotor if you could even find one with the right dimensions. One of the big advantages of this swap is the significant increased performance of the front brakes, so I would speculate that you would need to get a thunderbird sport wheel or have a custom front wheel made that has provisions for dual front rotors and that sounds expensive. I will upload a picture with the bike fully setup this evening with the brake routing and calipers I used.
 

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so I ended up having to move the wheel more towards the right hand side of the bike.
That worries me, on mine (and every other ZRX conversion I know of) the rear wheel has to be aligned to the extreme left of the swing arm in order to align its centerline with that of the front wheel. Have you checked your centerlines are in alignment?
 

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Discussion Starter · #5 ·
I followed the procedure in the Haynes Manual of placing a piece of string on back of the rear tire so that it is just touching the front of the rear tire then ran it all the way up to the front tire. From there I measured the front and back of the front tire to make sure the wheel was straight and then took a measurement to calculate the offset. I ended up having to take 4-5 mm off of the rear caliper mount to get it aligned. In the end I am getting the correct 60 mm difference between the front and rear tire(front is a 120 and rear is a 180). That is very odd that most people have it setup all the way to the left, perhaps I will recheck again to make triple sure.
 

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question

I have a 98 TBS. I really like the Kawasaki forks for aesthetic reasons and I was wandering it is not possible to use the spoke wheels with the Kawi forks? The TBS had the duel front disks. I am sure size differences are an issue.
 

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I have a 98 TBS. I really like the Kawasaki forks for aesthetic reasons and I was wandering it is not possible to use the spoke wheels with the Kawi forks? The TBS had the duel front disks. I am sure size differences are an issue.
Which aesthetic reasons are you talking about? If its just the black lowers you could have your forks powdercoated.
 

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The first thing I noticed was walking the bike and at slow speeds it felt a bit tippy however I guess this is understandable due to the increase head tube angle.
I fitted a steering dampner for just that reason.
 

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No, it's not just the black lowers, although, I do like the black lowers. I also like the way it levels the bike out. It sounds like a good modification for handling too. I was just hoping I could keep spoke wheels. Is the wheel change necessary if I have a TBS? It has the dual front brakes.

I bought a sprint damper in anticipation of this modification when riding season is over. The people a Sprint are great.
 

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I fitted a steering dampner for just that reason.
Although I have one fitted, I didn't find it felt like it needed one, and the geometry numbers werent such that I expected it needed one. However, if you have seen Northern Vermont roads you will see why a steering damper might be a good idea - if there is any place you could get a tank slapper its up here due to the frost heaves and potholes.

What originally lead me to buy one was the above coupled with the fact that when I first did the conversion I had more radical geometry from the Trophy trees plus I had clip-ons. After I got used to the latter and the change in geometry I rode without the damper and it didn't feel at all bad. However, even now I have the TBird Trees back and regular bars, I have kept the damper because of the roads (though its on a fairly low setting)
 

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Spokes, close, but looks like it will work.

I have a 98 TBS. I really like the Kawasaki forks for aesthetic reasons and I was wandering it is not possible to use the spoke wheels with the Kawi forks? The TBS had the duel front disks. I am sure size differences are an issue.
My Project bike has 2000 ZRX forks. I have Tokico 4 pot calipers from a '98 GSXR 600. I just test fitted a TBS front Wheel.

The calipers line up with the rotors, just fine. The calipers clear the spokes, but it is very close. My intention for this bike is to use either a 18" or 19" front wheel on the twin disc hub. I am not sure how that will effect the spoke/caliper clearance yet. I will put the 18 and 19 on there tomorrow, but those are only on single disc hubs so that will not tell me very much. I believe it will work. With that fork and caliper combination the 310 mm rotors fit. The guys on the ZRX forum like the 4 pot Tokico's and I was able to find a good deal on those. It's not a race bike, but the extra brakes will be very helpful for the sidecar.
 

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Having just got my 1200 front and rear end stuff together.... I was wondering......

Is the measurement for the rear wheel spacers standard across all of the Tbirds that have been modified, or is every one different?. I presume that you have to line up the front and rear sprockets, and then make the spacers accordingly?..............does it matter if the rear wheel is offset from the front, and if so, what's the cure.

Thanks

Rob
 

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does it matter if the rear wheel is offset from the front, and if so, what's the cure.
yes - very much so!

The rear wheel centerline must be the same a s the front wheel - it does not need to be aligned with the C/L of the bike (just its center of gravity - but don't worry about this aspect) .

Machine the rear spacers and shim sprocket and rotor to make the above so, otherwise you may end up with a bike that is dangerous to ride.
 

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Thanks Mick. I have a mate who's an engineer who will be helping me with the spacers. He's generally quite clever, so I might not look stupid twice :).

Rob
 
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