Topic: R6 Fork Swap information gathering

[FunJimmy]

Agree with Cal. In the end, will +-10 lbs really make a difference? I'd wager you would not be able to tell the difference. Do it for the braking, I wouldn't worry about the weight.

If the weight is unsprung weight it makes a significant difference. Lester mags would be cool but alloy hoops will offer wider rim options. Then you can get better rubber and really take advantage of the suspension upgrade. Why bother if you don't plan on using it?

[calj737]

If the weight is unsprung weight it makes a significant difference. Lester mags would be cool but alloy hoops will offer wider rim options. Then you can get better rubber and really take advantage of the suspension upgrade. Why bother if you don't plan on using it?

So what is the stock weight versus the "upgraded" weight? Wider rims mean wider tires, which weigh more. Aren't you canceling out the weight savings? I still think the modern upgrades are exactly that; upgrades in braking and handling, but not so much in the weight category.

[SOHC4 Cafe Racer Fan]

I think the conventional-style R6 forks are a good upgrade for handling and braking.  They weigh approximately the same as the stockers but are more rigid and the binders are definitely better.  I suppose you could get away with 1 and have a real weight savings, but the 2 floating rotors and calipers are still MUCH lighter than a single solid cast iron rotor and stock caliper.  The stock rotors are SO heavy.  Cal has a valid point with tires and wheels. It all depends on how wide you go. My Lester was lighter than my spoked wheels.  Aluminum rims are lighter than steel, but rubber is rubber.  If you go big, you pick up weight.

[Scott S]

 And all this depends on whether or not the Lester can even be modified since the hub is an integral part of the wheel.

[FunJimmy]

So what is the stock weight versus the "upgraded" weight? Wider rims mean wider tires, which weigh more. Aren't you canceling out the weight savings? I still think the modern upgrades are exactly that; upgrades in braking and handling, but not so much in the weight category.

Clearly the primary motivation for a modern suspension upgrade isn't the weigh savings although I believe it's more significant than you suggest. Especially if you use only one rotor and caliper which provides significantly more braking performance that a 550 needs. Scott has an R6 front end so maybe he'll post some weight comparisons.

[FunJimmy]

And all this depends on whether or not the Lester can even be modified since the hub is an integral part of the wheel.

Those spacers are specific to a modified stock front hub and may not be ideal for your Lesters. Special spacers specific to the Lesters with a focus on preserving the wheel may be possible. Post a couple of closeup pics of the Lester hub. Both sides.

[Scott S]

 OK, this isn't the exact set of Lester's but I already had these pics uploaded. I'd have to go out and remove the disc, speedo drive, etc., to get close ups I can do that, though.
 Here's what I already have in Photobucket:







 What I CAN tell you is that all the stock stuff bolts right up; speedo drive, rotor, spacers, etc.

[slikwilli420]

I would definitely be interested in seeing the weight difference between different sets of conventional forks. There are a ton of 38-41mm options out there for a very fair price. The real magic happens on the inside, where all of these forks can benefit from new springs, emulators, and careful setup. The majority of riders here would be very hard pressed to find the limits of conventional forks, properly setup, let alone finding those limits on a USD conversion, which looks completely out of place on these bikes.

As to braking, pick up any number of calipers, stock or aftermarket, and you will get something much better than the stock Honda items. Aftermarket Brembo units look period, are inexpensive, and offer excellent stopping power. Regarding rotors, I can confirm that a stock 750 rotor is about 3lbs heavier than a 300mm modern disc. Times that by 2 and you essentially have a 2 for 1 weight advantage.

I say make the Lester work. They are great wheels, period correct and I rarely see one adapted to anything other than stock forks.

[FunJimmy]

Another option, although not one I'm a fan of is to machine a special axle assembly to fit the hearings. You loose some of the benefits that a large diameter axle provides. Have you got the bearing part number or an OD measurement for the bearings?

[FunJimmy]

I say make the Lester work. They are great wheels, period correct and I rarely see one adapted to anything other than stock forks.

Lester mags would also resolve the spoke/caliper clearance issues.

[Scott S]

Another option, although not one I'm a fan of is to machine a special axle assembly to fit the hearings. You loose some of the benefits that a large diameter axle provides. Have you got the bearing part number or an OD measurement for the bearings?

 For the bearings the Lester's use? They use all stock parts on a stock front end, bearings included.

[FunJimmy]

Another option, although not one I'm a fan of is to machine a special axle assembly to fit the hearings. You loose some of the benefits that a large diameter axle provides. Have you got the bearing part number or an OD measurement for the bearings?

 For the bearings the Lester's use? They use all stock parts on a stock front end, bearings included.

You might want to consult a bearing supplier for options.
If you can find bearings that fit the hole and have a larger ID that might be a start

[slikwilli420]

The front wheel on my race bike had stock OD but has been upgraded to 20mm for a larger axle. I'm using a CBR rear on the front since they are cheap and hollow.

[SOHC4 Cafe Racer Fan]

Does the stock R6 steering stem need to be modified or swapped to mate to a CB500/550?

[Camrector]

No negative Don. Stock stem length is perfect.

[RAFster122s]

If the offset is the same you can use the FZ6 top triple tree for the R6 bottom and then have the handlebar clamps built in.  I have a spare FZ6 top triple but it is missing the pastic bolt caps for the handlebar..  Scottly has one of them I sent him with a few other items.  Provided he didn't unload it. 
 I ended up buying 3 as the forks didn't have everything on top triple and third had the plastic caps...was cheaper to pick up another than buy the caps new.

Do you have dimensions from your top triple?  The FZ6 has the ignition loop surrounding lock on front of triple...can be shaved off when repainting or powder coating the triple.


David

[Bankerdanny]

And all this depends on whether or not the Lester can even be modified since the hub is an integral part of the wheel.

As I was reading this I was gearing up to ask if Lesters would work for this as I have them on my 550F and have been toying with moving them to my stalled 550 sport tourer project, which I am now thinking of perhaps revising to include a 650 swap and a modern fork update.  So I WAS thrilled to see this pop up in this thread.

[Scott S]

 I'm still collecting parts and trying to wrap up another project before digging into this, but it's my plan (hope?) to use the Lester's. I'll talk to my machinist about all this and report back when I get to it.

[RAFster122s]

Not sure if it is needed but a titanium axle or a hollow high strength alloy axle of larger diameter could help in the goal of lighter...  The modern forks come with usually axles in the 22-25 mm diameter. When compared to our puny 16-17 mm axle it is multiple factors more rigid.   Ideally if the Lester's could be fitted with bearings to accommodate the axle without increasing the outer diameter would be best.  Just realize this is a trade-off sometimes in bearing life...not that we expect long life, 50K miles but more like 20-25k miles. A good quality bearing will of course perform better than a cheaply made bearing if maintained.  If that can be accomplished without increasing the bearing outside diameter it could easily go back to the stock use with internal spacers to support the bearing tube between bearings.  Just a thought.
Are the Lester's threaded on both sides for disk attachment in stock form?

[Bankerdanny]

Yes, the Lesters come ready for twin disks

[calj737]

Not sure if it is needed but a titanium axle or a hollow high strength alloy axle of larger diameter could help in the goal of lighter... 

CroMo is all you need. Save the Ti for the track.

[RAFster122s]

Thanks Cal, a street machine is not as demanding and I don't know materials best suited for the job.  It certainly doesn't need anything more than the stock axle for the replacement fork. Our bikes will not stress the axle as much as a modern rigid chassis and we cannot make our chassis strong enough to approach that level.

[Scott S]

 There's a pretty good chance I'll be able to get the bike, wheels and front end stuff to the machine shop this week.
 I'll disassemble the front wheel to keep from paying them to do it. For clarity: the inner hub stays empty.....No spacer, bearings, etc., right? Just knock out all the old, stock stuff.

 And I asked somewhere but can't find the answer now; how long are the bolts used to hold on the new spacers and rotors?

[fantino]

I wonder what true weight savings occur with modern front end swaps. The inverted forks seem to be much heavier that stockers to me. Sure, the rims are lighter, and depending upon whose hug you use, it can be lighter (the Cognito hub is definitely heavier than stock) and then you add 2 smaller calipers (weight push or perhaps a touch more) and 2 rotors (got to be a bit of savings there). So in the end, is it truly a weight savings? Defintely better braking and suspension, but I am dubious over weight gain.

If the R6 are conventional, then perhaps they are a light package?

Cal, I know this is an older post, but just to add reference for this thread, the weight of the R6 forks, axle and triples is about 3kg less than the same stock 500/550 components.

I haven't weighed the calipers or discs yet, but the floating disc is noticeably lighter than the stock disc, it feels like at least .75-1kg. The 4 pot caliper compared to the single pot and it's mounting bracket feels like a wash, with a slight lead to the R6 caliper.

The hub with all aluminum adapters and spacers is barely 100g more than the stock hub. I shaved a little extra off the far side spacer because I was using flange bolts so I didn't countersink.

There's a pretty good chance I'll be able to get the bike, wheels and front end stuff to the machine shop this week.
 I'll disassemble the front wheel to keep from paying them to do it. For clarity: the inner hub stays empty.....No spacer, bearings, etc., right? Just knock out all the old, stock stuff.

 And I asked somewhere but can't find the answer now; how long are the bolts used to hold on the new spacers and rotors?

I used 100mm M8 flange bolts for the spacers and 16mm M6 bolts for the disc.

The inner hub requires an axle spacer to press on the inner bearing race so you don't preload the bearings when you tighten the axle down. But yeah, all the stock bits inside get knocked out and tossed.

Also for more fun reference:

http://litetek.co/Guide_USD_ForkDatabase.html

this is a compendium of modern front ends with lengths, disk offsets, fork offsets, etc. It's mostly USD setups, but a few conventional setups have snuck in.

[Scott S]

I used 100mm M8 flange bolts for the spacers and 16mm M6 bolts for the disc.

The inner hub requires an axle spacer to press on the inner bearing race so you don't preload the bearings when you tighten the axle down. But yeah, all the stock bits inside get knocked out and tossed.

 Thanks for the bolt length!

I thought the shelf on the one aluminum spacer sort of served that purpose? To prevent the bearing from getting pushed in.

 EDIT: Nevermind, I have the dimensions for the spacer.