I've managed to track down a back-up of my rear wheel conversion how-to that I posted before the big VFRD crash of '06. This is the follow-up to (appropriately enough) part 1:
http://www.vfrdiscus...showtopic=38065
Enjoy....
Well, it seems I�ve stalled long enough and decided to tackle the rear end conversion on my �87 VFR. Some of you astute listers may recall the front-end conversion that I tackled a few months ago. I�m hoping this thread can serve as a bit of a guide for all those looking to fit radials to their first gen VFRs and also to get feedback, opinions and ideas from any who care to offer them.
First some details: My current set up is a YZF600 front end and the stock rear end. The bikes current set-up is a considerable improvement over stock in front-end compliance and feedback as well as in braking. To be honest, in the 3000 miles of moderate street riding I�ve done since the conversion, I�ve never had any issue with the stock rear end � I�m running a bias-ply Dunlop GT501 in the stock size (130/80/18) and my stock rear shock is in good health. Combined with the radial Metz M3 I�m running up front, I�ve never had an issue with available grip or experienced any sort of instability or odd handling that might be attributable to the mismatched tires� I�ve scrubbed the rear tire to the edges and dragged pegs with this combination. However, the possibility of an upcoming track day this fall has me wanting to outfit the bike in matching track-worthy rubber, so radials front and rear it is.
The most common rear end upgrade for the 1st gens is the CBR600 F2/F3 swap, which gives you a sleek 5 spoke 4.5/5 inch rim to run a 160/70-17 rear and to match the F2/F3 front end swap. I�ve decided to go a different route, since I�d like to try and match the rear to the 3 spoke YZF front rim. Considerably less has been written about fitting a wider 3 spoke rear to the VFR, so this stands to be more of a trial and error process than your standard F2 swap.
The rim I�ve chosen to adapt is one from a �90 Honda CBR1000F. It�s a 3 spoke, 5.5 inch wide rim, so it promises to press the limits of what can be made to fit in the relatively narrow VFR swingarm. It�s a close enough match for the YZF front, and while considerably rarer the F2/F3 rims (on e-bay anyhow) they tend to be in lesser demand as well. I�ve managed to contact and pick the brains of a couple of folks who�ve done versions of this conversion so have got an idea of what I�m in for, it�s just a matter of the specifics.
A couple of before pics:
http://www.vfrdiscussion.com/forum/uploads/1141596813/gallery_3111_1241_75053.jpg '90 CBR1000F rim w/180 tire
http://www.vfrdiscussion.com/forum/uploads/1156758399/gallery_3111_1241_27040.jpg Rear view before: Skinny bias-ply 130 Rear view before the upgrade: Stock 130/80/18 bias ply on 3.5 inch rim.
I�ve had a chance to make some measurements and do some preliminary test fitting. Dez Chand was kind enough to hook me up with the details of his CBR1KF swap, so I had his recommendations to work from. I�ve gone through the measurements numerous times and feel I have the start to a workable plan.
What I�m gonna need:
1) �90 CBR rim � found this on e-bay, but most year CBR1000F rims from �89 through �96(?) should work. The rear rotor sizes vary between the pre-LBS and LBS models but otherwise I believe they are comparable. I picked the �90 because it�s in great shape and it came in white � the colour I wanted.
2) CBR sprocket/hub assembly with cush drive � bought this with the wheel. Some machining of this hub is required. In stock form the hub/wheel assembly won�t fit between the swingarm so some mods are required. The sprocket carrier mounting faces have to be machined down 10 mm. This is to maintain proper sprocket alignment. You�ll also have to lose the dust seal on the outer sprocket carrier bearing, since the lip (against which the seal sits) needs to be machined down 5mm to allow the whole assembly to fit in the swingarm. (Pics to follow!) I�ll also likely have to ground off the tips of each sprocket mounting stud for the same clearance reasons. This part here looks to be the most complex part of the swap. A good friend with a giant lathe or well outfitted machine shop would be invaluable here. A machining shop can also handle this operation, but it won�t be cheap.
3) Custom spacers � The dimension for these were calculated keeping three things in mind: Wheel centerline � The aim is to keep the front and rear wheels properly aligned Sprocket alignment � Misaligned front and rear sprockets will make short work of the countershaft support bearings and your chain and sprockets themselves. I used the stock swingarm to sprocket distance as my target. Rear rotor/caliper alignment � The goal here is to keep the rotor in the same position as it was with the VFR wheel (so that it will still work with the stock carrier and caliper). Again, I used the stock swingarm to rotor-surface distance as the target.
I�m going to be using two spacers � one created from shortening a stock VFR spacer, one will be a custom jobbie. (Dimensions to follow).
4) VFR rotor and brake assembly � I�m pleased to report that the CBR rim has the same rotor bolt pattern as the VFR rim, allowing the (still large) VFR rotor to be used in place of the huge CBR unit. This is one advantage of this swap over the F2/F3 swap � you can use your stock VFR rotor, caliper and caliper carrier sans modifications.
5) Brake torque arm modification � This still needs to be modified. I�m hoping that moving the brake arm to the outboard side of the forward mount, and bending the arm into a slight �S� shape to realign it with the carrier mount will gain me enough clearance for the wider wheel and tire. I may have to resort to grinding the arm down slightly. In the event that I can�t get the stock arm to work, some more thought will be needed here. Thanks for the heim joint lead, Rob, those look like they might be the ticket if I have to go the completely custom route!
6) Tire selection � The rim came with a 180/55/17, but I�m going to be swapping to a 170/60/17 for a couple of reasons. Firstly, as Rob mentions, clearance will be awfully tight with the 180, not only with the swingarm, but with the chain. The by-product of the modifications in #2 above is to bring the sprocket and chain 10mm closer to the centerline of the tire, which means that with the 180 fitted, and proper chain alignment, there will be but a couple of millimeters between the chain and the edge of the tire. Dez Chand ran a 180 on his race bike for 3 seasons with this set-up and didn�t have any issues, but I�d sooner fit a slightly narrower 170 to free up a bit more breathing room. The 170 will also be a slightly taller tire than the 180, which will be a help to minimizing the ride height that I�m losing going to a 17 inch wheel. The 170 promises to still be more than enough tire for the 80 rwhp VFR and it�s spindly swingarm. Those who race the old VFRs tend to prefer the quicker handling of a 160 tire to the 170, and I expect a 180 would slow the handling even further.
7) Ride height � I�m going to need a way of restoring the rear ride height back to stock (or ideally a bit higher, to offset that wide, slow turning rear). This will be accomplished by a shock swap. I have a couple of options here � depending on how much lift I need at the back. A while ago I picked up a cheap CBR1KF shock as well as a Fox TC ride height adjustable shock off of e-bay. I�m still in the process of getting a proper spring and clevis mount arranged for the Fox shock, but I�ll be looking to get that sorted out soon.
For now though, I�ve dropped the hub and spacers off at my machinist�s to have them work their magic. Hope to hear back in the next few days
With spacers in hand and a freshly machined hub (nice work!) it was time for a test fit! Oops, no wait�..first we have to shorten each of the sprocket mount studs by about 5mm so that they don�t contact the swingarm. One angle grinder, lots of sparks and much metal dust later, we have our completed studs. Install short studs in hub, bolt up sprocket, and and the new hub is complete. Install rear wheel with new spacers, and Voila! B)
http://www.vfrdiscussion.com/forum/uploads/1158547428/gallery_3111_1241_59391.jpg 180 rear.jpg
But it's not all cake. A few issues of note, in no particular order:
1) Brake carrier and rotor clearance. I was surprised to find that once the axle-nut was cinched down to spec that outer edge of the rotor was lightly rubbing against part of the caliper carrier bracket. I can only guess that the spacer that I calculated to fill the wheel/caliper carrier gap (26.5mm) is perhaps a mm too narrow(?). The spacers otherwise seem to work great � when cinched down the spec the wheel spins freely (aside from this, and it�s only a very gentle grazing so they can�t be too far off of ideal. Rather than test this theory with another custom spacer, I took the patented time-honoured approach of many a backyard hack � I took an angle grinder to�er. With the bracket relieved of about 1/8� of an inch of material, there is now plenty of space, still plenty of strength and the rear brake looks to be sorted. :music:
http://www.vfrdiscussion.com/forum/uploads/1158547428/gallery_3111_1241_67204.jpg brakecarrier.jpg
2) The machining of the hub has meant that the chain alignment looks great. However, when the rear wheel is properly aligned (according the marks on the swingarm) the 180 Bridgestone BT020 just grazes the chain. I had been hoping that there might at least a mm or two clearance with the wide 180, but it looks to not be the case, at least with this BT020. I have heard of folks �shaving� the tire edge for clearance, but I�m personally a little bit leery of filing down my tire. I�m intending to go to a 170 tire with my next tire change, but had hoped to run the 180 for the shakedown runs until I get the bugs with the conversion worked out.
http://www.vfrdiscussion.com/forum/uploads/1158547428/gallery_3111_1241_1343.jpg chainalign.jpg
3) Ride height. As predicted, I see about a �� drop at the rear of the bike with the 17 inch rim sorted. On paper it doesn�t sound like much, but when I sat on the bike I was really surprised. It felt really low at the back � like a dog with worms dragging its arse, or one of them blinged-out street drag Suzuki Hay-Bus�s or somesuch thing.
The CBR1000F rear shock will NOT work. I finally got around to having a good hard look (and a measure) to see if this shock is a real option. As it stands, the shock length is in the ballpark and it has a bottom clevis mount, which would hopefully be fairly easy to adapt, but alas, it�s not. The CBR shock has its preload adjuster mounted at the top of the shock (the stock VFR shock has a remote preload adjuster), and there�s very little room around the upper shock mount (the VFR�s battery box is in the way). My hopes for a cheap solution are dashed. Ah well, back up on Ebay with that one then.
On to getting the Fox shock sorted out then. Until this is done, I�ll try adding more preload to the stock rear shock to see what I can gain and likely drop the front forks a bit as well to try and level it out. All though, at 6�2�, I�m not too keen on making the bike any lower. The 170/60 tire should help here slightly too.
4) Brake torque arm � it looks like I�d have to grind an AWFUL lot of metal off of the arm to get it to clear the fat 180, so I�ll likely try and go the bending route. Here�s a pic where I�ve swapped the front mount to the outside of the bracket. I�ll have to bend the arm (benchtop vice and elbow grease?) into a gentle S shape to get it to realign with the rear arm mount.
http://www.vfrdiscussion.com/forum/uploads/1158547428/gallery_3111_1241_55016.jpg brake arm.jpg
5) Gearing - I was running 15/45 gearing (one down on the front from stock) and have been liking it. I currently have the following sprockets to choose from to get my gearing sorted: 15T, 16T, 42T and 45T. I had originally planned on going 15/42, which (by my calcs, anyhow) would leave me slightly lower than stock, but not as low as the 15/45 I had been running. But�.turns out I�ll have to take a link or two out of my stock 110 link chain to get the chain tensioned properly with this set-up. Not sure yet I want to do this, since this will limit future gearing options. Considering going 15/45, and honing my mad icy-hot stuntin� skillz. Or possibly going back to 16/45�but I come to like the extra SNAP from the 15/45�.Thought required here. As always input welcome. Updates to follow soon�..
Not a whole lot of progress, but did manage to get a couple of things sorted. I've managed to suitably modify the brake arm for clearance using nothing more than a bench mounted vice and a few less-than-gentle blows from a rubber mallet. The arm was actually more malleable than I thought it would be. A bit primitive perhaps, but I'm pleased with the results :thumbsup:
http://www.vfrdiscussion.com/forum/uploads/1161372053/gallery_3111_1241_126786.jpg brakeside2.jpg
And another view (sorry, for some reason the gallery post tool wasn't cooperating):
http://www.vfrdiscussion.com/forum/index.p...i&img=17156
I also took a pic of the spacers used for this conversion. I've included the dimensions I used, but as always, YMMV.
http://www.vfrdiscussion.com/forum/uploads/1159021414/gallery_3111_1241_122964.jpg Stock VFR left, modded VFR center, custom spacer right The stock VFR sprocket side spacer on the left. In the center is a stock spacer thats been machined down to 7 mm. On the right is the custom brake rotor side spacer (20mm ID x 30mm OD x 26.5mm length)
And a couple of closeups of the spacers installed:
[image: View Post]keny, on Apr 4 2008, 04:18 AM, said:
Would you mind post here the length of the FOX shock you use. You PM:d the mesurment to me sometime, but that PM has for some reason dissaperd.
I ended up using a height adjustable Fox twin-clicker originally intended for a CBR600F3. For a CBR, it comes configured with an eyelet lower mount. When I added a clevis lower mount to the shock, and made the shock as short as possible (via the ride height adjustment), the length of the shock from top mount eyelet to lower clevis eye was 11 5/8". This is an increase in shock length of about 5/8" over stock, and makes up for the loss of height from the 17 inch rear wheel and also adds some additional height in the back over stock as well (I've dropped the front slightly to complement this).
11 5/8" is about the max that you can go without running into clearance issues with some aftermarket exhaust crossover pipes contacting the swingarm. Interestingly, I think the stock pipes have lots of clearance in this dept. I can't go any longer on my conversion, because my Yosh gets in the way (and I think you have reported your Motad did the same?), but to be honest, I don't think there'd be any benefit (and possibly some instability issues) in going much longer/higher at the rear. From what I've gathered, 1/2" to 5/8" in added length seems to be about right. While the Fox works great, in this application it's still not a perfect conversion for the VFR because it has to be run at it's absolute shortest to work, which means you can't really use it's ride-height functionality. Still lots cheaper than a full custom built shock though, ofcourse :warranty:
[image: View Post]vfrcapn, on Apr 10 2008, 02:43 PM, said:
Looks great. Did you swap the clevis from the VFR shock on to the Fox, or source the lower clevis from somewhere else?
Thanks! I couldn't see how to remove the lower clevis from the VFR shock without completely destroying the shock, so I tried to source one from Fox and other suspension suppliers. They do exist, but I had no luck finding one. While I could have had one made, I went the cheaper route and made one myself out of a chunk of 2" box section steel (and a high grade threaded bolt). It's pretty crude and took a lot of test fitting and grinding to make, but if you have a drill press, it's doable.
Hey Pegasus, any chance you could have stuck a washer or two on the inboard side of the countershaft sprocket, to space it out by .040"-.080" , and also taken that much less off the hub, to retain the 180 tire and still clear the chain?
Or would that much space have caused the chain to hit the frame?
On one hand I hope you sold the bike already, but on the other hand I hope you still have the old girl so I can ask more questions in the near future...
[image: View Post]SEBSPEED, on Sep 8 2008, 12:14 PM, said:
Hey Pegasus, any chance you could have stuck a washer or two on the inboard side of the countershaft sprocket, to space it out by .040"-.080" , and also taken that much less off the hub, to retain the 180 tire and still clear the chain?
Or would that much space have caused the chain to hit the frame?
On one hand I hope you sold the bike already, but on the other hand I hope you still have the old girl so I can ask more questions in the near future...
Thanks!
While I have had weak moments, I've decided to not sell it since I don't think I could really stand to part with the bike. As such, I've just checked and there does look to be enough room to space out the sprocket mounting faces to give the extra clearance for a 180 - there is no risk of interference from the frame. There's actually loads of room at the front sprocket, the pinch point is the narrow swingarm opening- if I was to shim the rear sprocket outwards more than a few additional millimeters I'd likely run out of thread for the sprocket retaining nuts - the studs are already shaved down to clear the swingarm. In the event I decide to run 180 rear tire, I was thinking a 520 chain conversion (with offset front sprocket and shimmed rear) might free up a few extra millimeters. As it stands now, I'm not too bothered, since I like the way the 170 handles as is.
[image: View Post]Pegasus, on Sep 10 2008, 09:30 PM, said:
[image: View Post]SEBSPEED, on Sep 8 2008, 12:14 PM, said:
Hey Pegasus, any chance you could have stuck a washer or two on the inboard side of the countershaft sprocket, to space it out by .040"-.080" , and also taken that much less off the hub, to retain the 180 tire and still clear the chain?
Or would that much space have caused the chain to hit the frame?
On one hand I hope you sold the bike already, but on the other hand I hope you still have the old girl so I can ask more questions in the near future...
Thanks!
While I have had weak moments, I've decided to not sell it since I don't think I could really stand to part with the bike. As such, I've just checked and there does look to be enough room to space out the sprocket mounting faces to give the extra clearance for a 180 - there is no risk of interference from the frame. There's actually loads of room at the front sprocket, the pinch point is the narrow swingarm opening- if I was to shim the rear sprocket outwards more than a few additional millimeters I'd likely run out of thread for the sprocket retaining nuts - the studs are already shaved down to clear the swingarm. In the event I decide to run 180 rear tire, I was thinking a 520 chain conversion (with offset front sprocket and shimmed rear) might free up a few extra millimeters. As it stands now, I'm not too bothered, since I like the way the 170 handles as is.
Could always machine a little off the sprocket, to give the nuts more room. Jamie does the opposite and threads the hub so a low-profile bolt head can go on the outside - and the heads could be ground down a bit too.
Wonder if the rubber chain guide needs to have the "guide rib" sanded off for this...
End of thread · 11 posts recoveredWayback Machine snapshot 28 Jul 2010