YZF/THUNDERACE SWINGARM CONVERSION

[cycloneranger]

I have just been cleaning up a YZF swinging arm used on a TRX and there is a clear sign that the chain has been nibbling the arm bracing. The sprocket on the rear wheel was not dished? I can see the need for the offset front sprocket though.

[andyaber]

Hi

The term dished sprocket may be a bit misleading. Most sprockets are flat on the face that is supposed to bolt against the wheel but undercut or stepped on the outer face so it is thinner in the centre section than at the sprocket teeth.

The common practice of turning the rear sprocket around then moves the chain slightly more in line with std front sprocket but closer to the swing arm.

By adjusting the position of the front sprocket, the chain should run straight and line up with guide on swing arm, have plenty of clearence with the swing arm and revert to correctly fitted rear sprocket. Happy days i think.

Cheers, Andy.

[Trixed]

With all these YZF conversions that people have, can we definitely say the wheel alignment lines up. Sprockets are sorted on mine, but do the wheels line up perfectly? I mean alignment.

[cobbadiggabuddyblooo]

No they don't align as Conrod placed up on his thread on this subject with his yzf swingarm conversion.
I had all this confirmed myself through Dave Kellett engineering who specialises in frame straightening and modifications.
Your still around 10mm out from memory even before machining to get you wheels centre then you need to accommodate for the relay arm/dogbone alignment to the swingarm .
So after machining the swingarm pivot point on one side and spacing the other side and the same for dogbone alignment on the swingarm points, you finally get your wheels centred and sprocket alignment with no offset sprocket needed and dogbones aligned to the relay arm.
Compare the swingarm dot com dot au. ...Sergei..... Bubbles

[dixonj]

No they don't align as Conrod placed up on his thread on this subject with his yzf swingarm conversion.
I had all this confirmed myself through Dave Kellett engineering who specialises in frame straightening and modifications.
Your still around 10mm out from memory even before machining to get you wheels centre then you need to accommodate for the relay arm/dogbone alignment to the swingarm .
So after machining the swingarm pivot point on one side and spacing the other side and the same for dogbone alignment on the swingarm points, you finally get your wheels centred and sprocket alignment with no offset sprocket needed and dogbones aligned to the relay arm.
Compare the swingarm dot com dot au. ...Sergei..... Bubbles

Funny how our wheels line up perfectly when using the yfz/thunderace swing arm (see post by andyaber group buy) our chains line perfectly with the chain slider using a 6 mm off set sprocket. we have also had our finding checked by a very well respected motorcycle engineer who builds and races bikes and sidecars.

[cobbadiggabuddyblooo]

Each to their own..

[andyaber]

With all these YZF conversions that people have, can we definitely say the wheel alignment lines up. Sprockets are sorted on mine, but do the wheels line up perfectly? I mean alignment.

I did try and rally the troops who have done the yzf swing arm conversion to measure their wheel alignment and report back their results to give some sort of consensus of opinion.

The only people who posted were myself and DixonJ/tzx660.

I can only suggest that if you do such a conversion that you measure the alignment yourself and follow your own results and act accordingly.

Cheers, Andy.

[tzx660]

I have used a yzf swing arm ,wheel , spindle and spacers. I have double checked my wheel alignment and found it to be ok ( please have a look at pictures on this post ). I personally believe this is the easiest solution to the wider yzf wheel. There may be many ways to solve this problem, in my opinion this is the easier solution. Please back up your replies with pictures as I think I am missing something. Thanks Paul.

[andyaber]

I'm in agreement with Paul.

I have no photos but measured my alignment as best i could then went back and did it all again, learning as i went.

I THINK my wheels are in line but my sprockets are obviously not.

These are my results and i don't claim them to be exclusively correct or better than anyone else's measurements in their situation.

Measure your own set up and act accordingly.

Cheers, Andy.

[Con Rod]

as per previous thread on this. In my case I have a YZF750 rear end. Not a Thunderace one, I dont know the measurements for the thunderace

If you have gone with a complete front and rear conversion to the YZF forks, swingarm and wheels you will have a 120 front and a 180 rear, so you have a difference of 60mm (or 30mm either side) between the front tyre against the rear.

Therefore you are aiming for an alignment measurement of 30mm on either side of the front tyre. That is, a straight line from the rear wheel tyre wall, exactly parallel to the bike will be 30mm from the tyre wall on the front.

If you just put the complete YZF rear end on, (swing arm and rear wheel) and measure the alignment you will get a gap of 39mm on the left and 21mm on the right

By removing the 4mm spacer from the right of the swingarm pivot and adding it to the left I have moved the swing arm 4mm to the right.

You will now have a gap of 35mm on the left and 25mm on the right (from 39 / 21 previously).

But the front and rear wheel will still be 5mm out of alignment.

To address this you can now move the wheel 5mm to the right.

This can be done, as I did by shaving 5mm off of the rear calliper bracket and adding a 5mm spacer on the left.

This is good as it will bring the wheels into alignment without causing any clearance issues with the shock linkages, pipes and hangers.

It will mean the chain wont sit right on the guide again. This can be addressed by adjusting the guide or sprockets.

But more important than having the chain alignment spot on is having the wheel alignment correct.

I have done the above and in the interest of addressing queries here I have posted some pictures below.

the method I used to measure my alignment is here

http://www.framestraightsystem.com/Moto ... 0Check.htm


Right side










Left Side










string is about 1.2mm

[Trixed]

Some great info there Conrod. I will be doing this check myself so I can come to my own conclusion. I have a 2005/6 R6 front end and yzf rear end. I have a suspicion that the rear wheel is misaligned toward the right. Be interesting to find out.
Thanks for the info all.

[cobbadiggabuddyblooo]

Thanks for your excellent ,detailed findings with photos Paul and other option to move the wheel the final 5 mm to centre the 10mm difference.
Either way will give you a true wheel alignment after machining and again each to their own on what to machine and how to centre..
Good photo guide on how you came to your conclusion also top marks mate for the effort..
Taking 5mm from the the swingarm pivot and dogbone pivot from the swingarm and spacing the opposite side just keeps the wheel centred in the swingarm itself and aids in alignment of the chain guard and chain guide as Dave Kellett engineering had made me aware so that's why I finally approached this by by the third option and just machining the yzf750 wheel and bearing swap to fit into the std TRX swingarm...

Then after all that trouble I settled with a 5.25" dymag 5 spoke magnesium to suit a trx in the std swingarm so I have multiple tyre size choices from 160-180 on the 5.25 rim and the bonus of shedding 5kg front n rear with the added gains in acceleration/braking and handling characteristics of lighter weight wheels

So no disrespect to anyone

[NWS870R]

Magnesium wheels on a road bike Cobba?

[Trixed]

Paul
Would u be able to post a pic of the whole rear end assembled?

[Con Rod]

there are a few more pictures of it in this thread.

viewtopic.php?f=6&t=7414&p=94800#p94800

If you need any specific shots, close ups etc let me know and I can post them up