My f2 wheel conversion done! Finally!

Discussion in '1st & 2nd Generation 1983-1989' started by 577nitroexpress, Mar 19, 2013.

  1. 577nitroexpress

    577nitroexpress New Member

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    Yup, helps to keep new rubber on. I still had the shake with a new BT45, my bike just didn't like those tires.
     
  2. 577nitroexpress

    577nitroexpress New Member

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    I would be cautious about making too many radical changes to geometry on these old bikes, they seem to like being as close to stock as possible. Thats why I did as little modification as necessary to do the wheel swap. IMHO.

    I know there have been really neat custom mods done to these, but I've not heard how those changes affected handing. Maybe somebody could report on that?

    My ride report so far is that the bike handles similar to a later model gen 4 or gen 5. I've not ridden a gen 3, so I can't tell on that one. I defiantly feel like I can push deeper and harder into corners now, it feels less squirrely.
     
  3. stryker

    stryker New Member

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    I'm about to do the same swap as you did. My question is, did you adjust the rear ride height or did you
    Just lower the front? Will it work or do i have to modify the rear shock as well?
     
  4. 577nitroexpress

    577nitroexpress New Member

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    So basically, when you do the wheel swap the rear drops .5 inch, the front drops ~2mm, the geometry is about .00056 degrees off. By dropping the front 4.5 mm to 5 mm the rake is returned to the stock configuration. I chose to lower the front because I have a stock length Ohlins rear shock and wanted to use it. The overall seat high reduction is .5" as well as the CG. I have experienced ZERO ill effects from doing this, and in fact the bike handles fantastically now.

    Realistically, if you look at the exact numbers, .00056 degree change, is imperceivable to the average road rider. Bearing wear would cause a greater change in rake than this.

    My advice, for what its worth, is, if your rear shock is stock and worn, then chuck it and get a Fox or Ohlins and rise the rear, but only 5 to 6 mm and drop the front 2 mm. If your shock is good, drop the front 4.5 mm and call it good.

    To calculate degree change use the sin(a) = opp/hyp make sure to calculate in degrees and not radians.
     
  5. stryker

    stryker New Member

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    Ok, thank you. I'll just lower the forks then. I have a almost brand new emc shock. An 87 shock would have been perfect.
     
  6. JasonWW

    JasonWW New Member

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    The stock 130/80/18 rear tire is 26.5" tall. A modern 17" rear tire tends to run 24.5"-25". So the difference in diameter is between 1.5" and 2". So actual ride height drop in the rear should be between .75" and 1".
     
  7. stryker

    stryker New Member

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    So lowering the front forks is not enough then?
     
  8. JasonWW

    JasonWW New Member

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    It might be enough. What rear tire sizes are you coming from and going to?

    If you have the stock shock or another one that is not adjustable you can remove the shock and extend the 2 fork prongs that attach to the linkage. It's a matter of cutting, fabricating longer pieces and welding them on. Then re-adjusting the chain, of course. I think 10mm longer on the shock is about 25mm in ride height.
     
  9. stryker

    stryker New Member

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    I'm running stock size at the moment, after the swap i'll be running 160/60/17
     
  10. JasonWW

    JasonWW New Member

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    Okay, that size should be 24.62" diameter.
    If your measuring your stock tire diameter, make sure to measure from side to side, not up and down. The sidewall on the bottom tends to flatten due to the bikes weight. Also compensate for wear. Tires shrink in diameter as they wear down. It's also possible the tire isn't exactly the size it's supposed to be. If you take a 130/80/18 from all the companies making them you'll notice their true width can vary quite a bit. Overall diameter can vary some as well. Your current tire might have been made slightly smaller in diameter than a 130/80/18 should be.

    80% of 130 is 104mm. That should be the sidewall height. Double it, convert to inches and it's 8.12. Now add the rim diameter and you get 26.12". Ah, seems I miscalculated a little when I did this the last time.

    So 26.12-24.62=1.5" difference which puts the rear axle .75" closer to the ground. That's actually good as I've seen 160/70/17 tires which are 25.7" tall. If you ran that size you'd be really close to stock diameter and not have to alter the rear ride height.
     
  11. stryker

    stryker New Member

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    What rear sprocket size do i use with the F2 rear rim to keep as close to original as possible?
    Remember i read in the forums somewhere, but can't seem to find it, going blind i think ;)

    And does the CB900 Hornet rear brake disc fit the CBR f2 rear rim? As it has a larger diameter than the CBR disc(no need to move the caliper)
     
  12. JasonWW

    JasonWW New Member

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    Hey, a little update. If you recall my bike has always had a frontend shake while decelerating with no hands on the bars. Plus it always felt kinda twitchy. The other day I decided to raise the front of the bike about 1/2" by lowering the forks. The bike feels more stable now and I can actually take my hands off the bars and no shake! Awesome!

    The clipons have about 7mm less fork tube to grip to and this is about all I dare raise the front, but hey, it feels much better now. I'm still swapping frontends, though. :cool:
     
  13. 577nitroexpress

    577nitroexpress New Member

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    I used the 43 tooth that came with the rims. It is very close to the same ratio as the stock 45 and 18" rim. At 6000rpm I indicate ~78mph now.
     
  14. 577nitroexpress

    577nitroexpress New Member

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    still planning on this, have a new job that is up my "free" time now.
     
  15. 577nitroexpress

    577nitroexpress New Member

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    Just a quick update on the mod. I have about two months of riding on it now, in the mountains, and commuting, and all is well. I replaced the chain and sprockets as they had about 20k on them.

    Riding report:
    My impression, the bike feels 100% more controlled in high speed turns. I can get a knee down with ease and feel totally planted. Transitions time is about the same but with less effort, which I think is due to lower CG (lowering the front 6mm).

    I also installed the RaceTech Emulators, up front and have an Ohlins rear shock, these have of course significantly improved the handling on their own, and with the radial tires and fork brace have transformed the bike into a real sweet heart. On our back roads here in CO, she really performs now. I can chuck it into a series of switch backs and keep up with anybody with out the "holy crap" moments on those old crap tires.

    Best I can describe the transformation, is that it really handles like my old 4th and 5th gen Viffers now(which is what I wanted). Same kind of confidence and neutral turn in feel. With the old rims and tires, to me, it felt like the front wanted to turn in too fast and tuck, then slip, and the rear would step out. Straight line is very stable, and the deceleration wobbles are gone.

    Right now I'm happy to leave the geometry where it is, but, I am still going to play with raising the rear to see what effect it has on real world handling.

    577nitro-Jason
     
  16. 577nitroexpress

    577nitroexpress New Member

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    Yup I agree here, I dropped the front 6mm from 5 and real world measured at 27 degrees, but we're talking FCH measurements. I think this horse is dead though. Either method will work fine, IMHO. I love the way my bike both looks and handles now, we'll worth the agro to do it.

    I would like to look into improving the front brakes.

    577nitro
     
  17. rosok

    rosok New Member

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    577nitro[/QUOTE]

    Good day,
    I've been searching through the forum for anything I can find on the F2 wheel conversions. I'm new to the forum, so Hello!

    I bought a couple F2 wheels years ago in hopes of upgrading my '86VFR750F. Nitroman (577Nitroexpress), you sound like you have it all sorted out, excellent! I see a couple guys have asked you about a step by step procedure of how you went about your mod, that would be extremely helpful (now that you've done all the hard work :smile: )

    I've already had my front machined for the discs, and the speedo drive has been machined, but not enough. I was afraid to go any further as the speedo drive lug is getting very thin, so I need to figure that out still.

    the rear wheel I have is a 5in I believe, with the cush drive and stock F2 sprocket. I think possibly the drive unit will need machining to line up the chain correctly. I'll need to mount it and take some measurements. did you switch to a 525 chain from the stock 530?

    for the rear disc I bought an F2 caliper and holder that I am hoping to retrofit, I remember reading something about this a few years back. I'll try and attach some info that I have gathered regarding this mod......if I can just figure out the attachement feature.....which isn't working for me right now.

    cheers,

    Richard
     
  18. WayneC

    WayneC New Member

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    Hi
    Would you please send me a sketch with diamensions of the origonal rear wheel spacers. Mine were stolen while my bike in a tow truckers
    yard, very long story but did manage to get my vfr back.

    Cheers,
    Wayne
     
  19. fatso1277

    fatso1277 New Member

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    If anyone is interested i still have the F2 forks with progressive springs and gold valve emulators installed as well as the rear f2 wheel. trying to get rid of them.
     
  20. 577nitroexpress

    577nitroexpress New Member

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    Sorry I milled the originals to make part of my conversion so I don't have the specs, but I'll see if somebody does.

    You can buy used ones on eBay for cheap though.
     
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