We Don't Need No Stinking Cush Drive...

I'm trying to sort out the rear-end mods to my FP to match the NR rear wheel (or at least not embarrass it) and I've come to loathe the RC36 cush-drive monster hub-sprocket-carrier-thing, or whatever it's called. I've considered fitting an entire RC30 swing arm, which would be the dog's bollocks, with its exotic brake torque arm and sexy good looks, but they are about 35mm shorter than the RC36 swinger (not to mention kinda rare on the second-hand market). And there's no place to mount the torque arm to the RC36 frame, either...

RC30 Swing Arm1.jpg

[image: gallery_362_402_52929.jpg]

RC30braketorquearm2.jpg

And here's the OEM RC36 swing arm:

Hideous braced swingarm 2.jpg

(Okay, OEM doesn't look this bad, but I couldn't resist!)

But, I think I could simply replace the sprocket carrier with the one from the RC30. In fact, I may have to, as I'm using a modified RC30 axle/hub to fit the RC40 rear wheel. OEM RC30 rear sprocket is 40T, and RC36 is 43T, but it shouldn't be hard to find--or even have made--an RC30 rear sprocket with 43T, methinks.

The two-pot sliding brake caliper has to go as well. I've got an SP1 (RC51) rear caliper and m/c on the way, which is modern, gold and probably a lot lighter. I'd love to mount it below the swing arm (like on the RC30), but as the torque arm mount is on the top of the swing arm, that might be difficult...

RC36 cum RC30-04.jpg

I have collected a number of extra swing arms in the garage (I'm an aspiring BC Guy...) and yesterday I was pleasantly surprised to discover that the NC30 alloy torque arm uses the same mounting bolts as the OEM RC36 swiss-cheesed steel torque arm (though it is longer). You can see it peeking out from behind the rear brake disc on my 4-bolt-converted NC30:

PA250014x.jpg

I should be able to do something with that, the SP1 rear caliper, the RC30 sprocket carrier and some sort of peek-a-boo with the rear brake line...

Oh, back to the reason for my post: any reason I should try to keep the cush drive?

Cheers,

A cush drive is designed to save your transmission from the rigors of stop and go traffic. All those minute throttle adjustments would play hell on your transmission if you didn't have those little rubbers pieces in there to dampen those forces.

Race bikes don't have a cush drive but they are on the gas or not on the gas...and they rebuild the tranny every race.

You can leave it out but you will pay for it eventually.

I think I hear what you're saying, but i don't agree with why you're doing it. What are you trying to create, in the long run? An RC30 rep? Your bike's never going to be an rc30, and as close as you'll get to it, a cush drive isn't going to be the reason why it'll never be an rc30. things like magnesium cases, big bang motor etc will always be there to stop you actually 'making' an rc30, the cush drive is a tiny piece in the jigsaw, and from what some people say about the rc30 once they've stopped drooling, perhaps it needs a cush?

Anyway, tell me more about this sp1 caliper?

Why not use the NC30 axle /hub / brake disc / calipper / sprocket. Will fit with some tiny mods.

Lot easier than modifying an RC30 item and a lot cheaper (I bought a complete NC30 swiingarm for 90 pounds at ebay.co.uk)

Just a note, although it looks cool, the brake torque arm on the left side of the RC 30's swingarm has always seem to be the target for deletion by many modders/racers. If you look at many race RC 30s they are mostly gone, replaced by shorter subtitutions similar to what the street VFRs have.

I think the torque arm aytem on the 30 is just too needlesly complcated and adds to unsprung weight at the rear.

Beck

95 VFR

Thought it was obvious by now: this is all about the bling, man... I'm tired of having aesthetic pygmies inflicting their visions of VFR nirvana on me, and now its my turn! But, I don't want it to look "like" anything it isn't--I mean, it's a red RC36-I...not exactly the ideal canvas for rocking the motorcycle design world, but it's what I've got; it's what I know; and in the immortal words of Kevin McCloud, "it's got authenticity." (Somehow, I don't think Grand Designs has made it across the Pond--oh, well!)

Okay, rant over. Thanks for the views. NC30 is an option--I know the RC30 uses the same sprockets. I don't have a spare NC30 sprocket carrier (though I do have a spare NC30), but I do have a spare NC35 sprocket carrier, and they appear to be similar, apart from the colour. The NC35's is gold, rather than RC30-black. That could be just the trick. I was actually hoping you might have used the RC30 part on your bike--why not? And, aren't you the same guy who told me the RC30 hub/axle would fit!?!

Here's the sprocket carrier on what used to be Rick Oliver's fine trackday VFR400R:

rick-7.jpg

(Note RC30 torque arm...)

And here's the NC35 version:

brochureswingarm.jpg

Joe, yes I know why most large bikes have cush drives, but the RC30 doesn't, nor do the 400s, so it's probably within the realm of compromise. I'm making a STATEMENT, here, dammit! But I hadn't heard of anyone complaining about the RC30's lack of cush drive, either. Nor have I seen any RC30 owners rushing to modify that aspect of their bikes. If RC30 trannys were dropping parts all over the place, something would have been done about it, methinks.

I agree about the torque arm, Beck. Of the four different brake caliper location techniques employed on the RC30, RC36, NC30 and NC35, the RC30's definitely seems to be the most complicated--and heavy. (But it is still the sexiest!) If I were going to use the RC30 swing arm, I'd weld a boss onto the frame in order to use it, but it's just not an option with the RC36 arm.

I actually spoke too soon about the SP1 caliper being "on the way", having mixed it up with the front calipers and discs I had already won on German eBay, but I actually did win the rear caliper today:

SP1 rear caliper.jpg

IIRC, the RC36 disc brake carrier is a fairly simple affair that could easily be modified for a different caliper, provided the offsets worked out okay. Another bit o' gold, too...

Thanks for the input, lads. :thumbsup: Once I've sorted out some more of the details, and I'm ready to begin zee modifications, I'll start a new "Frankenviffer" thread to document the work.

Ciao,

Re: the cush drive: PM Crazy Larry. He modded an RC36 rear drive unit to eliminate the cush drive.

But instead of using adapted Honda parts, he machined his own (naturally).

LOL. Larry doesn't return my calls...

Ciao,

IMHO, the NC30/NC35 hub is much kewler looking than the RC36/46 one (why are they so FUGLY!?!?), and reason enough for doing this mod.

And after having to replace cush-rubbers on several bikes (including VF500, VFR750 and VFR800), I reckon the reduction in driveline slop caused by not having them would be a GoodThing as well.

So, I say Go For It! :thumbsup:

JZHOkay, rant over. Thanks for the views. NC30 is an option--I know the RC30 uses the same sprockets. I don't have a spare NC30 sprocket carrier (though I do have a spare NC30), but I do have a spare NC35 sprocket carrier, and they appear to be similar, apart from the colour. The NC35's is gold, rather than RC30-black. That could be just the trick. I was actually hoping you might have used the RC30 part on your bike--why not? And, aren't you the same guy who told me the RC30 hub/axle would fit!?!

Yes,the RC30 hub/axle will fit. On the time I did the mod I had no RC30 hub as a spare part (do/did not want sell the RC30's in parts...)

NC30 hub/axle/brakedisc/calipper on the VFR750F:

[image: gallery_668_420_61256.jpg]

achterzijde..02Aklein.JPG

[image: gallery_668_420_6929.jpg]

achterzijde..02klein.JPG

in the immortal words of Kevin McCloud, "it's got authenticity." (Somehow, I don't think Grand Designs has made it across the Pond--oh, well!)

We get it in Oz; it's one of my favourite shows.

In my view the cush drive is there because Honda knows a fair percentage of buyers are going to be a bit ham-fisted with their shifting, and it allows a bit of 'give'. A bit like the built-in straight-ahead steering freeplay in cars known as 'sneeze factor' - a performance driver would prefer that it was not there...

Got a Factory shift kit John? That combined with elimination of the cush drive would have to make for a tight tranny (oo err).

OEM, thanks for the pics. The NC30 sprocket is an MR7 part, as is the 38mm conical washer, so I suppose there is a good chance that the NC30 sprocket carrier will fit onto the RC30 axle/hub splines. What worries me is that the 38mm nut is a different part... Rick Oliver's got my RC30 hub/axle, so I can't really test anything. It looks like the worst case scenario is that the NC30 carrier won't fit on the RC30 hub/axle, and I'd have to use one from an RC.

Murray, I see your point about the shifting (of course I have a Factory shift kit!), but I'm willing to see how it goes. If I'm crashing gears all the time, I'll have to reconsider, but this time, I think I've got to choose form over function...

(I love that line from Pulp Fiction in your sig. I think I'll steal it from you some day--like I stole the one currently in my sig--thanks Barry!)

Ciao,

(Oops! I see that my sig line isn't included on VFRD! Well, it matches the avatar: "What is a motorcycle for, if it isn't action?" --The Mouse and the Motorcycle, by Beverly Cleary.)

New kinda snag I thought of recently...sprockets! The RC30/NC30/NC35 line of rear sprockets are available only in 525 (OEM) and 520 chain pitches, but the RC36's OEM chain pitch is 530--a much stronger chain. It looks like I can fairly easily get 43T rears in 525 or 520, but steel is harder to find than alloy. I can also get a 16T 520 countershaft sprocket for the RC36 engine--not so sure about 525. So, really, the only obvious commonality is 520 chain and sprockets, which I >might< be able to get in all-steel, but more likely steel front and alloy rear.

The difference between the tensile strngth of a 520 and a 530 chain is significant--greater than the difference between a 525 and a 520, anyway. There is no issue with "race weight" on my bike, but I am concerned that a 520 would not be able to handle a torquey 837cc engine. Or am I being paranoid? Plenty of high-powered bikes use 520 chains and don't snap them left and right, do they? :unsure:

Ideally, I would just have someone MAKE me an RC30 43T 530 rear sprocket in steel (or alloy), but I don't know of anyone who could do that, much less for an affordable price...

Alternatively, I could take an OEM (or aftermarket) RC36 (or other bike) 43T 530 rear sprocket in steel (or alloy) and machine it to fit the RC30 sprocket carrier OD and bolt pattern...

Thoughts, commiserations?

Cheers,

yer being paranoid. the 520 conversion is fairly common for the VFR's... the 520's can handle most anything you'll be able to throw at them out of the VFR lump...

I'd agree with ss burns. A 520 is plenty enough, but it'll last a bit less time, that's all. Keep it clean and oiled and you'll have a chain that lasts for about a year and a half at least, I'd say. The alternative is to speak to renthal themsleves, rather than looking in catalogues, they're based a mile or two from me, it's not like the stuff comes form the other side of the world or anything. All bike engineering may be worth a shout too. Anyway, what's the problem with an alloy sprocket anyway? Get a renthal hardened one and it'll last almost as long as steel but it's about a quarter of the weight, plus you'll get a pair of big flourescent stickers to go on your belly pan too!

JZHIdeally, I would just have someone MAKE me an RC30 43T 530 rear sprocket in steel (or alloy), but I don't know of anyone who could do that, much less for an affordable price...

Alternatively, I could take an OEM (or aftermarket) RC36 (or other bike) 43T 530 rear sprocket in steel (or alloy) and machine it to fit the RC30 sprocket carrier OD and bolt pattern...

Thoughts, commiserations?

Cheers,

Chain Gang out of Australia should be able to help you out with a steel sprocket:

http://www.chaingang.com.au/index.php

Or maybe these guys in aluminum:

http://www.rebelgears.com/

JZH... but I am concerned that a 520 would not be able to handle a torquey 837cc engine. Or am I being paranoid? Plenty of high-powered bikes use 520 chains and don't snap them left and right, do they? :unsure:

No problem ! smile.gif

My VFR837F has a 520: RC30 steel front and RC30 "Wieres" alu rear sprocket.

Looks like I can get an AFAM 520 set "off the shelf"...

HONDA 520 CONVERSION RACE SPROCKETS

VFR 750F 90-97 16/43 PART #

16T 520 FRONT SPROCKET 20608-16

VFR 750R

43T 520 REAR SPROCKET 11601-43

...in the OEM ratio. That's a hard anodised alloy rear and a steel front. Couldn't find a Renthal 520 front, and I have AFAMs on my other bikes, anyway, so I may as well go with AFAM.

Ciao,

Hard anodised or not, it's still going to go through that sprocket pretty quickly.

You'll get a performance benefit to trade it off against, of course.

ChainGang in Oz will make you a 520 flame-hardened steel sprocket that will give you enormous mileage with good maintenance (ScottOiler is best) but they are not cheap. Let me know if you want more info.

The PhantomHard anodised or not, it's still going to go through that sprocket pretty quickly.

You'll get a performance benefit to trade it off against, of course.

ChainGang in Oz will make you a 520 flame-hardened steel sprocket that will give you enormous mileage with good maintenance (ScottOiler is best) but they are not cheap. Let me know if you want more info.

Thanks, I've been in touch with Chris Haggarty over at Chain Gang, and not only will they do a 520, they will do a 530, which means that I can simply use a (new) OEM front sprocket with a 530 DID X-ring chain and I'm done (though slightly lighter of pocket!). Might want to check the offsets before I order, though...

Btw, he quoted me AUS 125--do you guys charge VAT on exports? I assume that price includes VAT, or sales tax, or whatever, but at least here in the EU, exports outside of the EU do not attract VAT... As I'll probably have to pay UK VAT + customs duty on import into Blighty, I'd rather not pay Australian tax, too!

All in all, I'd still prefer to have a 530, and this now seems practical to achieve.

Cheers,

John

John, AB is the man for the VAT questions, he is gainfully employed in a related field. But from memory I don't think you'll be paying our GST.

$125AUD is about the usual price. They discounted for one of our group buys, but the discount was mainly in the free freight, not small change either with 10 sets of chains/sprockets going interstate.

When you next talk to Chris, if it hasn't already been discussed, ask him about the CNC lightened sprocket, they did ours for no extra charge (they just came up with a CAD design to make a one-off sprocket for their VFR750 shop bike). It looks good:

[image: gallery_5581_740_52436.jpg]

They left two panels in and drilled two holes in each of them, I suppose this was their solution to being able to screenprint their company name onto the sprocket. I've turned it in for now as it's neon pink! WTF. Ask them to cut out ALL the panels!

Will the stock sprocket from the RC-36 not fit? In the very first/top picture, it almost looks like it could. I have been quite curious as to this. Especially as I just put a new chain and sprockets on my VFR. If I were to find these parts on eBay I would be willing to do these mods. If you get a definitive answer on the sprockets, as well as your other issues, please let me know. Thanks!!!

The RC30/NC30/NC35 sprocket carrier is a smaller diameter (by a significant amount) than the RC36's cushy carrier. So, no, they are not interchangeable. I've still got to figure out the offsets...and how to remove my spare NC35 sprocket carrier from where it's mounted--on a spare NC35 swing arm, not attached to a bike (and still torqued up tight indeedy...)

Oh, and I might be going to Dubai for 2 months. Can you say, "projects on hold"?!? :blink:

Ciao,

JZHOh, and I might be going to Dubai for 2 months. Can you say, "projects on hold"?!? :pissed:

BTDT.

Quick follow-up to a mystery mentioned above: The 38mm axle nuts are different because the RC30 doesn't use a staked nut, like the NC30 and RC36; it uses a safety wire-drilled nut. I discovered this upon my purchase of a polished RC30 swing arm, naturally...

[image: gallery_362_402_10230.jpg]

VFR750Rpolishedswingarm1.jpg

And yes, I got an RC30 torque arm to go with it... :P

The swing arm clearly has a "history", but I'm not a party to it. Some of the brake parts are carefully marked "swing arm #2", suggesting it was once part of someone's race kit, and the arm itself is marked "SJ" on the top of the eccentric. It is also set up for running the rear brake line internally, so I may do that. I'm also thinking of powder coating it, rather than leaving it polished, but I'll see how it looks on the bike before making a decision.

Ciao,

Good stuff JZH, so you are considering running the RC30 arm despite its shorter length? Or can you slip the eccentric and related goodies straight into the VFR arm?

Racking my brains trying to put 'SJ' to a racer, no luck yet smile.gif

You either run the '30 arm, or you don't, as the torque arm requires a different casting. Form over function, I'm afraid. I'm just a slave to goddess of bling...

Ciao,

From the "waited a wee bit too long" department, I just got a reply to my email earlier this week from Chris Haggerty at Chain Gang on Oz, who informed me that they have had to cease trading. Oops. sad.gif

In the meantime, I'd found another company that may do "custom" work, this time in the 'States, Sidewinder Sprockets. We'll see...

Ciao,

Just a note:

I had a friend once that had custom wheels on his early CBR900RR, PM's I think. He let me ride it once. No cush drive. It was difficult to be smooth on it, and I did not like the feel at all. That's a really torquey bike though, and probably amplified the issues, but, if you like to be smooth....

On the 520 chain, like everyone has said, buy a good one and you'll never have a problem... I've had them on all my track bikes, including the torque ripping YZF1000R, never had a problem. Started running the xring versions on the street too... one in my Tuono now works great, and I'm hoping to get what I expect as a full life out of it... which ain't that much, unfortunately. Without an oiler, I realistically expect 10k to 15k miles. Or seven rear tires... whichever comes first! :fing02:

Has anyone tried to "pantograph" the heavy/humungous looking cush drive hubs. Seems like the thing is over-built anyway. A few interesting lightening holes(?) and machining here and there might helps it's weight and looks problem. but you do have to ba careful not to get carried away lest it blows apart on you the next time you wring the throttle hard "in anger"!

One of the pics posted on this thread seems to show the VFR hub looking better when stripped of paint, showing some shiney machined surfaces, just like when you strip the VFR wheels. Am I correct? If this is so, it looks like a quick mod that can be done with the hub on the bike and some careful masking and stripping.

Beck

95 VFR

Wanna really look "kewl"? Ditch the rear brake all together. 95%+ of the braking is done with the front wheel. Heck, Nicky and those guys don't even have the rear tire on the ground when they're braking hard anyhow.

When I use to road race, one of my fellow racers on a TZ250 decided to do an experiment. He totally removed his rear brake - caliper, disk, etc. His lap times only slowed by 0.1 sec/lap.

Holy dusty thread alert Batman! :fing02:

BeckHas anyone tried to "pantograph" the heavy/humungous looking cush drive hubs. Seems like the thing is over-built anyway. A few interesting lightening holes(?) and machining here and there might helps it's weight and looks problem. but you do have to ba careful not to get carried away lest it blows apart on you the next time you wring the throttle hard "in anger"!

Haven't seen it, I'm sure it could be done without ill effect to the overall strength of the component, but it would introduce a whole lot of crud into the bearing housing.

BeckOne of the pics posted on this thread seems to show the VFR hub looking better when stripped of paint, showing some shiney machined surfaces, just like when you strip the VFR wheels. Am I correct? If this is so, it looks like a quick mod that can be done with the hub on the bike and some careful masking and stripping.

Yeah I stripped mine, it's nice and bright and hasn't tarnished at all despite sitting around in garages (some not as dry as I'd like!) for a few years...

JZHThe swing arm clearly has a "history", but I'm not a party to it. Some of the brake parts are carefully marked "swing arm #2", suggesting it was once part of someone's race kit, and the arm itself is marked "SJ" on the top of the eccentric.

The PhantomRacking my brains trying to put 'SJ' to a racer, no luck yet smile.gif

[image: gallery_4773_2719_43402.jpg]

thx1139

JZHThe swing arm clearly has a "history", but I'm not a party to it. Some of the brake parts are carefully marked "swing arm #2", suggesting it was once part of someone's race kit, and the arm itself is marked "SJ" on the top of the eccentric.

The PhantomRacking my brains trying to put 'SJ' to a racer, no luck yet smile.gif

Smokin' Joe?

[image: gallery_4773_2719_43402.jpg]

Nice one, that is probably it!

Nothing like reviving a seven year old thread...

And, no, I haven't actually done anything.

But if I do, I will be using this thread to do it!  I still have the RC36-I (the "Effenviffer"), the RC30 swing arm, various axle, sprocket and bearing carrier parts and the NR rear wheel.  Project-wise, I'm waiting for my RC46-I front end conversion parts to come back from various specialists, which finds my RC36-I on the lift in my garage and looking a bit lonely.  I'd been using it to play around with rear caliper options (in this thread: http://www.vfrdiscussion.com/index.php?/topic/83310-cbr919-rear-brake-caliper-and-master-cylinder/ )

Known issues list:

Torque arm: For the moment I can use the "race" version of the brake torque arm that came with my RC30 swing arm.  I would like to use the overly complicated OEM version, but that will require the welding of a lug onto the frame (although I might be able to attach it to the back of a rearset/heel guard or something), which is not something I want to do right now.

Axle: From my fiddling around with my RC36 and RC30 axles, it appears that there are not too many options, because I am effectively stuck using an RC30 axle.  I am stuck with that because that's the axle I had modified to fit the NR rear wheel's one-off PCD (I think Honda must have done that on purpose!)  That's my modified axle mounted in my RC30 swing arm in the pic below:

[image: 20160502_151016x.jpg]

I'm also stuck with the RC30 (non-cushioned) sprocket carrier, which, all things considered, I think I'd rather swap for the RC36 sprocket carrier (big and ugly as it may be).  But, I can use the NC35 (RVF400R) gold one, so at least it will look good!

[image: 20160502_151048x.jpg]

Sprockets:  Speaking of sprockets, the sprocket mis-match may be the most challenging issue I face.  The OEM RC36 front sprocket is a 16T 530 pitch cushioned one, and the OEM RC30 front sprocket is a 16T 525 pitch cushioned one as well.  Unfortunately, I don't know for sure if the RC30 sprocket will even fit on the RC36's output shaft--that's if I can find one (many Honda parts sources show it as being discontinued).  If it did fit, I could use a standard RC30 rear sprocket--if I can find one with 43T.

The only off-the-shelf rear sprockets available for the RC30 sprocket carrier are either alloy or steel, both in relatively few sizes and pitches.  I want a steel rear sprocket, but could use alloy if absolutely necessary.  The NC30/35 and the RC30/45 use the same rear sprockets, all with 525 pitch chains.  I could use 520 conversion sprockets, but there isn't any better selection of off-the-shelf sprockets in 520.  Ideally, I would like to use the OEM 16T 530 front sprocket with a custom steel 43T 530 rear sprocket.  So, how about buying a blank sprocket and having a bunch of holes drilled into it?  It's a machine shop job, but not a spectacularly difficult one.  The centre hole is 120mm ID, and the four bolts are on a 14mm PCD.  I could see adding a bunch of lightening holes as well.

Blank rear sprockets come with a pilot hole, but nothing else.  I would have to check the OEM RC30 offset and compare that with the 530 pitch blanks (which appear to be made from flat 3/8" thick steel plate).  This is a file photo of some "Chiaravalli" blank sprockets (which, strangely, are made by an Italian firm, but I can only find them for sale in New Zealand!):

[image: 22.1686-large.jpg]

Shock linkage:  The RC30 dogbone is slightly longer than the RC36 dogbone (5mm longer, IIRC), which generally results in a lower rear ride height, but the triangular "Cushion Arm Assy." has slightly different measurements as well.  (In fact, the RC30 dogbone is also slightly narrower than the RC36 dogbone, but that shouldn't be a problem.)  But, the RC30 shock is also significantly shorter than the RC36 shock: 307.5mm (vs 345mm), and let's not forget that the RC30 used an 18" rear wheel... 

I think the best solution may be to use the RC36 dogbone, cushion arm and shock on the RC30 swing arm.  That should keep all of the dimensions the same as they are now--apart from the shorter RC30 swing arm.  I have a spare RC36-I swing arm I will dig out, as it is much easier doing measurements off the bike.

Parts list:

Hugger/chain guard (need one for RC30, Thorsten Durbahn here I come)

Toe guard (I like my toes where they are)

Sprockets (OEM RC36: 530 16/43, OEM RC30: 525 16/40, something's gotta give)

Brake disc bolts & nuts (RC30 OEM size is M6?  Are you kidding me?  Well, I'm going to use titanium, then...)

Rebuilt brake caliper (Powerhouse in the UK can do this for about £70 all-in, in gold if I wish--and I do wish)

90-degree banjo fitting for brake line-through-the-swing arm (the holes are already drilled)

New bearings and seals for bearing carrier and swing arm pivot

Master cylinder (RC36 OEM: 12.7mm, RC30 OEM: 14mm)

[image: 20160502_190136x.jpg]

Ciao,

The good news is that the RC36 dogbone fits into the RC30 swing arm:

[image: 20160502_201251x.jpg]

I'm still measuring the RC30 and RC36 swing arms (which isn't easy!).  I'm going with 40mm difference in length, but it could be more or less than that.  Given the eccentric adjustment, I don't think I need the exact measurement.

The RC30 swing arm casting is 5mm narrower than the RC36 swing arm casting.  Narrower is better than wider!

The mounts on the swing arm for the cushion arm appear to be the same distance from the swing arm pivot bolts and in the same and lateral position (although given the 5mm narrower swing arm, I suppose they could be 2.5mm or 5mm one way or the other).  That is good news. 

However, the distances the cushion arm mounts sit below the imaginary centre line running between the pivot bolt centre and the centre of the opening for the bearing carrier are about 20mm different, due to the RC30's thicker swing arm, which will change the linkage proportions (in some way I have not yet worked out).  This could explain the RC30's slightly different linkage dimensions--but I could still use the RC30 parts if necessary. 

As I don't have an RC30 frame to measure, I'm probably going to just have to hope the swing arm pivots and dogbone mounts are in the same general positions and see what the bike looks like when it's all bolted up... [insert "eek!" emoticon here]

Ciao,

...and the bad news is that the shock doesn't fit onto the RC30 cushion arm!

I had not noticed before, but the shock-end of the RC30 cushion arm contains a spherical bearing, two bushing collars and two dust seals--unlike the RC36, which simply utilises a collar and two oil seals--and as a result the RC30 part is approximately 2mm wider than the RC36 part.  I wanted to use the RC30 cushion arm because the 20mm height difference mentioned in the post above apparently has the effect of reducing the rear ride height by (at a guess) 50-60mm.  I'm not into the motorboat/hardtail look...

The RC30 cushion arm (on left in photo below) is 10mm narrower, but that difference can easily be addressed with a pair of 5mm bushings.

[image: 20160504_163322x.jpg]

You can see that the RC30 cushion arm is ~10mm taller than the RC36 cusion arm; it is also ~5mm longer.  But recall that the RC30 shock is quite a bit shorter than the RC36 shock...so I am not at all sure where the wheel will end up if I use the RC30 cushion and keep all of the other suspension parts RC36...

Anyway, for test-fitting I will just remove one of the bushing collars and re-install the cushion arm.  The outer lips of the bushing collars are 2.3mm wide, so turning them down 1mm on each would get me the width I need (or I could have a new, slightly wider foot installed on the Ohlins shock).

[image: 20160504_174549x.jpg]

TBC...

Ciao,

Okay, so a day's worth of measuring and getting familiar with Tony Foale's Motorcycle Setup Analysis program, and I think I have my answer.  I measured the bike several times, as getting the data in the format required for the program to work was quite difficult for the first time.  Figuring out how to measure the various dimensions took a bit of noodling as well.  The program requires that the bike be measured from the ground up, with the suspension fully extended and the tyres just touching the ground.  I ended up sitting the bike on a flat scissors jack (for motocross bikes, I believe) and then lifting the front end using a floor jack and part of a front-end lift that bears upon the underside of the steering stem.  This only worked because the 3rd gen has a huge, flat iron centre stand mount the bike can be lifted from (and not fall over!)  I'm not sure how I will measure my 5th gen...

I also measured the available cushion arms and dogbones I had: RC36, RC30, NC35 and SP1.

It appears that the best solution for getting the correct rear suspension geometry with the RC30 swing arm will involve using the RC36 shock, the RC36 cushion arm and a shortened RC36 dogbone (93.75mm vs 115mm stock).  However, I have not yet accounted for the SP1 front end this bike will eventually have, so this is just a learning exercise resulting in an interim conclusion.  (Also, I should point out that my RC36 has VTR1000F forks with lengthened stanchions, so these measurements probably won't be relevant to anyone else.) 

Now to sort out the front end measurements and see what happens when I put them together with the RC30 swing arm...

Ciao,

John,

Great thread - I just found it today and find it fascinating. Lacking mechanical skills and decent garage/shed to do any complicated wrenching I am content to read about the efforts of others.

You mentioned using an RC36 rear shock - 3rd or 4th gen? My understanding is that 3rd gen options are rare as hen's teeth.

Another cool aspect of the RC30 was its front fork - the qd axle clamps really look the business, and despite being a conventional unit I seem to recall it was rated quite highly.

The 3rd and 4th gen rear shocks are not interchangeable, but I think the entire 4th gen rear suspension (swing arm, linkage and shock) could probably fit on a 3rd gen bike.  This bike already has one of those rare Ohlins shocks, so I want to keep it!  I agree, RC30 forks are sweet, indeed.  A bit lacking in the bling department, though!

I have now done a bit more modeling and I think an 86.5mm dogbone link and reducing the front ride height 20mm may solve the problems...I have created by insisting on fitting an RC30 swing arm and SP1 forks to my RC36.  I have not yet attempted to determine if anything would bind or clash, or if I could touch my toes, or if the side and centre stands would be long enough.  A lot of unknowns!  And what I could really use is an adjustable dogbone.  I might be able to make something using M10 rod ends?

Ciao,

Couple of things:

I could use the RC36 swing arm with the RC30 bearing carrier and axle, but would have to figure out a brake caliper mount and torque arm.  This is complicated by the fact that the RC30 bearing carrier uses a threaded nut rather than a snap ring to secure the caliper bracket.  And, all of the other caliper brackets I have measured have a slightly smaller ID, so would have to be bored out in order to fit onto the RC30 bearing carrier.  More machining, but do-able.

The RC30 swing arm is problematic due to its significantly shorter length, but it would allow me to fit a carbon fibre hugger (with the flipped eccentric on my RC36, huggers designed for the RC36 sit too far from the tyre).  I will have to play around some more with the suspension software...

Thanks to a tip-off from Y282 in this thread about fitting a ZX14R shock to a 3rd gen, I dug out my NC24 shock and linkage and measured the dogbone: 97.5mm and RC30-width, so 10mm narrower than the RC36 dogbone.  Its arms are wider, too: about 22mm.  Might be a good candidate for drilling, but the RC36 cushion arm wouldn't fit!  The RC24 dogbone also appears to be about 93mm in length.  Another option...

Ciao,

Always great to see that I'm not the only one complicating the shit out of my build : )

Well, it's progress... <g>

However, my current thinking is that the 30mm offset of the SP1/929/954 yokes is just not going to work with the shorter RC30 swing arm on this bike.  I can only get back to "normal" trail figures by jacking the back even higher than it is now (with the flipped eccentric) AND dropping the front end 20-30mm.  I have no idea how it would handle with numbers like that.  So, I'm probably going to go with VFR1200F yokes and SP1 forks to get a 35mm offset.  Five mm makes a huge difference...

I could definitely make the RC36 swing arm work with the RC30 axle I need to use with the NR rear wheel, but all things considered, I would miss the RC30's bling factor--I mean, it's polished!

I've had a closer look at the sprocket alignment issue (mentioned upthread) and if I can get a "blank" 530 steel sprocket machined to fit an RC30/NC30 sprocket carrier (shouldn't be too difficult for a friendly machinist), I'd need to fit 3mm spacers, but that would give me front and rear steel 530 sprockets in perfect alignment.  I would be fine with using 525 chain, too, but wouldn't know if the RC30 front sprocket would even fit/align before buying one.  And I'd still need a custom rear sprocket as I cannot find any off-the-shelf steel 43T NC30/RC30 sprockets.

Two steps forward, one step back...

Ciao,