.Hello, I am going to convert to a Thundercat rim and I cannot find some photos where the parts that had to be modified looked very good.
If someone can help me I will appreciate it very much
As long asyou got the Thundercat wheels spacers etc, there is only one part that has to be modified, the brake caliper mounting arm - I'm pretty sure from memory (it's a few years now since I did my conversion), the brake side spacer from the FJ is 8mm thinner than the chain side spacer, so it can just go in the chain side and no need to cut down the original.
If you put the wheel spindle through the swinging arm and slide the caliper mount (with the caliper attached) into place and put the torque arm onto it, it will hold the caliper mount in the right place. You can markthe caliper arm where the top of the swinging arm lines up with itand the that's the line to start your radius out from the 8mm reduction at the spindle.
Unfortunately I don't have photograph of the finished item on its own, only where it's in place on the bike.
You need to get the Thundercat chain side Spacer and take 8 mm of it that should bring it down to 11 mm wide ,You must use the Thundercat Brake side spacer as well ,,as it is ,, But you all so must have use the Thundercat Caliper Mount which you have to take 8 mm off on the swingarm side of the Caliper mount ,, So all up you need to loose 8 mm off both sides of the Wheel to make it mount into a FJ Swing Arm ,,hope that helps
I think it's worth checking Phil that the FJ brake side spacer is already the correct dimension to go on the chain side of the T/Cat wheel set-up, so no machining is necessary.
I just can't remember exactly, but when I did mine, I measured all the spacers I had from both wheel sets and found I didn't need to get any machined.
The way I've done it, if I ever decide to revert my bike back to stock, I have all the parts ready, on the shelf (front end as well) to just do it.
I don't ever envisage doing that, but if FJ's ever enter the "original is worth a fortune" stage, I can swap back easily
Thundercat? .......is that the YZF600?
If so, here you go: http://www.fjowners.com/index.php?topic=1567.0 (http://www.fjowners.com/index.php?topic=1567.0)
The only differences I had to the method John detailed is that you don't need to machine the sprocket carrier if you mount the sprocket with the shoulder to the inside of the wheel (instead of the outside) - that gives you the 3mm you need. I also found one of the spacers from the combined set from the T/Cat and FJ wheels was the correct size to use on the sprocket side, without needing to do any machining (I always try to follow the KISS method :sarcastic:).
I was measuring each part using my digital vernier calipers, but wasn't concerned about less than 1mm variance overall. When my wheel alignment was checked for its first MOT test, it was spot-on.
Quote from: Juanlamola on February 08, 2021, 03:14:33 AM
.Hello, I am going to convert to a Thundercat rim and I cannot find some photos where the parts that had to be modified looked very good.
If someone can help me I will appreciate it very much
Don't know who wrote this, but I have this excerpt from a file saved in my FJ files on my computer. I thought I got it from somewhere on here. The photo shows both the original T/Cat caliper bracket and the modified one. The text also explains the sprocket reversal theory too.
(http://fjowners.com/gallery/12/6213_09_02_21_12_48_39.jpeg)
That swap was pioneered by Jon Cain.
I have done this swap using the instructions mentioned above.
I have found that the FJ caliper is offset around 2.5mm towards the wheel/ away from the swing arm.
How have other people found the caliper position?
I have sourced a Thundercat caliper to see if the offset is different from the FJ's.
I've not found any issue with the FJ caliper mounted on a correctly modified Thundercat mounting arm, and of all the people who have done this conversion, I'm also not aware of anyone who has had the same alignment issue. Everything lined up perfectly (as preliminary measurements indicated) when I did the dry build on mine.
I haven't checked the calipersagainst each other to see if they are the same (dimension or part number), or different, dimension wise, but everything I've found says that the issue you have hasn't been experienced by anyone else.
Are you sure everything else is correctly aligned and in place on the whole wheel arrangement ?
I have pulled the chain side spacer and caliper mount out of the bike and confirmed they have been machined correctly as per the instructions.
Tomorrow I'll pull the wheel out and have a careful look at things.
As I got the parts from a wrecker there is the chance something has been included from another model or I've F'ed something up.
I have 2 spacers for in between the wheel and caliper bracket, 1 original FJ and 1 Thundercat. The FJ spacer measures 13mm x 30mm with a larger "shoulder" of 40mm and the Thundercat spacer measures 14mm x 28mm with a "shoulder" of 33mm.
As you mentioned Dean you could use the FJ brake side spacer on the sprocket side but it would be 2mm wider than the measurement in the instructions if my measurements etc are correct.
If only I had my own lathe/mill this would be long sorted :dash1:
Yeah, that's weird, mine seemed to measure up pretty much spot on.
It does seem co-incidental though that we're 2 mm different on the chain side and you're 2.5 mm out on the brake side. Thankfully I didn't need a lathe, although a friend with a milling machine did my caliper mount arm for me (it took him about 10 minutes all told to sort it).
It might be worth checking your wheel alignment with the existing set-up just to make sure everything is in line before you start making any "adjustments".
I believe I have found the problem.
The so called "professional" machinist I got to mill down my caliper bracket milled the face out of parallel so when you do up the axle it pulls the bracket out of alignment and hence pulls the caliper out of alignment.
It is 0.4mm out of parallel at the "pad" that contacts the swingarm. This adds up by the time you get to the caliper. And yes, I have relieved the bracket past the pad that is meant to touch the swingarm so that is not coming into play.
I went to see him this morning but of course he wasn't there on a Saturday morning. I could probably fix it myself with a file but would prefer to go back to the machinist on principal.
The phrase "fast, cheap, or good - you can choose two" DOES NOT apply to getting machine work done! You can only choose ONE! And sometimes that is a stretch it seems.
I hate when I have to find a new machine shop - you never know what you are going to get.
I've had my best luck when the machinist was actually interested in the project and wanted to see the finished project in the end.
Good luck! It sucks to pay a professional for less-than amateur results. :mad:
Yes. I paid good money to get the machining done on both the LH spacer and the bracket. $120. Paid him cash and no receipt so it probably went straight into his pocket.
I thought I'd give this guy a go as he is just around the corner from work which would be handy. Never again.
I do know a great machinist not much farther away. He has done a fair bit of work for me in the past on my Moto Guzzi including dual plugging the heads, lightening the flywheel, making up brackets to adapt 4 piston calipers, making up disk carriers etc. All without an issue. And he is cheap as he is into bikes and is a good bloke. I suppose the moral of that story is if you are onto a good thing, stick to it.
Luckily it's a lesson learned on a part you can replace easily if needed.
There ain't no way I'd try another machinist if you've got a good one!
I finally got my Thundercat rear wheel conversion sorted.
I went back to the machinist and he milled the caliper mount parallel this time, still the same dimensions as in the instructions, 8mm off to make the caliper mount 19mm.
When I installed the newly machined caliper mount and the left hand spacer that was turned down from 19mm to 11mm I noticed there was about 2mm of axial clearance before the axle was tightened. I measured the original FJ right hand spacer (as it was previously mentioned by others) and it measured 13mm, perfect for taking up the clearance.
I installed the FJ spacer and along with the reversed sprocket the chain alignment seems good. The caliper now also lines up with the rotor.
One other thing. I originally used new Ferodo rear pads but these measure 9.7mm depth, including the backing plate. While these fitted they were too thick to allow the caliper pistons to retract properly. I have ended up using DP brake pads. These measure 8.3mm depth and now there is no drag.