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Renthal Sprockets

Discussion in 'General' started by SteveH, Dec 7, 2009.

  1. SteveH

    SteveH

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    Hi all,

    Gonna treat myself to some sprockety and chain goodness in the new year. Looking at the Renthal ultralight front and rear sprockets. Will also be running a posh D.I.D or Tsubaki chain, but does anyone run the Renthal ultralight gear on their bikes and if so has anyone noticed a difference in the performance of the bike, as they do claim to be lighter than OE which has gotta reduce unsprung mass right?? and I guess critically the front sprocket, being the main engine powered output has to be a pretty important place to lose it would it not??

    Thoughts anyone????

    Cheers

    Steve
     
  2. U gonna put on the same number of teeth or losing one at the front?
     
  3. SteveH

    SteveH

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    Same number, don't want to mess with the gearing, and need all the top end I can get, all the guys I ride with have litre class sportsbikes. Just wonadered if it would make a noticable difference being that much lighter.

    Steve
     
  4. Anonymous

    Anonymous Guest

    I'm running the renthal set up on mine and not noticed any difference at all! The front sprocket is solid not holed like I expected so no weight saving there and it wouldn't make a noticable difference if it was. I've got a choice of one tooth less front or one extra rear. I prefer the extra excaleration it gives with only a small top end loss. It's easier to keep up with the big boys if you have acceleration after all how much time do you ride above 140? Don't answer that for legal reasons. Loosing unsprung weight is always a good thing so go for it just think about what I said about number of teeth.
     
  5. Rowly

    Rowly

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    My opinion would be great piece of kit more robust lasts longer looks good and yes is lighter but this is only just one of many bits that the racing boys change to save weight and gain 10th's off a second on their lap times in order to be in with a chance of winning but fitting just this you would hardly notice any difference on the road unless of course you alter the sprocket ratio as Siw has, but as a general improvement over stock then I would go for it ;)
     
  6. SteveH

    SteveH

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    The Ultralight front sprocket has a different part number to the solid one, and is quoted as being considerably lighter. Being directly linked to the output shaft I imagine small differences in weight will make more difference to the unsprung mass. I'm guessing now, but would hope to see similar gains in acceleration to what you would see from dropping a tooth. Time will tell I guess ;)

    This is just going to be the start of my "reduce unsprung mass" regime on the bike though. I'll soon be whacking on a ProBolt unsprung mass kit as well, and if I can get it past the missus I'm after a set of carbon rims to. Also been looking at a race rear subframe and other lightweight part replacement.

    Basically I'm after a touch more poke but don't want to mess with the engine internals as I've found in the past a modified engine is like a finely tuned race horse. The best thing going when it works but, the slightest failure and it all goes horribly wrong.

    Keeping up in the bends isn't an issue, infact if anything I'm a bit quicker, but the straights are a different matter, and we're planning some possible longer euro trips next year so I may well need some extra grunt. Alternatively if I can't keep up I'll have to get another bike with a bigger engine but I'm hoping not lol.

    Cheers, and watch this space!

    Steve
     
  7. Changing the front sprocket will make zero difference to the unsprung mass, it is on part of the bike that is sat on the springs. Also the increase in acceleration by putting a slightly lighter front sprocket on will be minimal in comparison to dropping a tooth, or gaining one on the rear sprocket (which if u replaced with a lighter one would also reduce your unsprung mass, as its mass does not contribute to compressing your springs).
     
  8. SteveH

    SteveH

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    Stolen from another site

    "Unsprung weight includes the mass of components such as the wheel axles, wheel bearings, tires, and a portion of the weight of driveshafts, springs, shock absorbers, and suspension links. If the vehicle's brakes are mounted outboard (i.e., within the wheel), their weight is also part of the unsprung weight."

    I'd have thought as the front sprocket is directly connected to the output shaft of the gearbox (or in a car the driveshaft) then this would also be included in the unsprung mass. With it also being so close to the output source I would've thought that minimal differences here would have a greater effect than the same mass loss further along the drive chain. Of course I could just be talking a load of carp also as I'm not that clued up on this for bikes lol. I'll get the sprockets and let you all know.

    Cheers

    Steve
     
  9. Everything that appears on a wiki site is not necessarily true. Unsprung weight is weight that is not supported by the suspension of the vehicle, car or bike. Eg the front sprocket is not unsprung weight, it is supported by the suspension. the rear sprocket is not supported by the suspension therefore is unsprung weight.

    Unsprung weights typically consists of the weight of the wheels, tires, brakes (if within the wheels), spindles, bearings, and a portion of weight of the springs, and suspension links.
     
  10. how about filling the tyres with helium :D
     
  11. hehe Nige, u can get them filled with nitrogen at quite a few places now lol
     
  12. D41

    D41

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    Going with the 520 conversion is an awesome mod IMO. - As "Godzilla" just mentioned, this mod has nothing to do with reducing unsprung weight...but it does reduce rotating mass - you WILL notice a slight increase in performance, even with stock gear ratios....if you REALLY feel the need to keep up with your litre-bike friends, Steve - then go down 1 on the front sprocket & up 1 or 2 teeth on the rear - you'll smoke 'em!! :twisted:

    ....Downside is that you'll be running a few thousand revs higher at motorway speeds & you'll need to have your speedo recalibrated...your call!
     
  13. Rowly

    Rowly

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    I see you've got a fixation on Jamie Lee Curtis Nige, and looking through the mirror there's no helium pumping them up but she may need some support since making that film :)
     
  14. Anonymous

    Anonymous Guest

    Now Nige you're being silly lol
     
  15. SteveH

    SteveH

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    You got anymore info on the 520 conversion mate? Is it just a thinner set of sprockets and chain? Road legal?

    Cheers

    Steve
     
  16. D41

    D41

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    Basically...yes - the 520 chain & sprockets are just thinner & lighter than the stock versions of each. There's plenty of debate as to which last the longer but the 520 conversion will defo allow you more gearing options - dropping 1 tooth on the front & going up 2 teeth on the rear will make your bike a frickin' screamer on acceleration - but you will lose some top-end...but let's face it - how often do you need to go over 150 mph??

    Don't know about the legality of it, but I'm guessing that unless you get pulled over by a plod who is also a part-time MotoGP mechanic, then it won't be an issue.
     
  17. Hi there,
    Sorry for dumb question, but what does 520 refer to, is it a brand or who makes them.
    Looking at some pimping of the bike over the winter.
    Cheers Richard
     
  18. D41

    D41

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    520 refers to the chain's gauge or 'pitch' - can't think right now what the term is...most sportbikes come with standard 530 or 525 pitch...675 comes with 525. 520 is an upgrade aimed mainly for the track, but is perfectly acceptable for the street. I'm currently running a stock 520 conversion with 15/45 gearing on my D650...I noticed a very slight increase in performance over the stock 525 set-up..but only VERY slight. I have a new set of 14/46 sprockets which I'm about to install - will let you know my impressions, but I recently rode a D600 with the 14/47 gearing & it was WAAAY quicker than my 650!!
     
  19. SteveH

    SteveH

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    Ahaaaaaaaaaaaaaaaaa, just realised my confusion! I'm confusing rotating mass with unsprung weight! IDIOT!! :doh:

    So is it just a case of swapping cogs and chain then or is there more to it than that?

    If it's just cogs and chain would the following do the job then?

    Front Sprocket
    http://www.bandcexpress.co.uk/sprockets ... pg-96.html

    Rear Sprocket
    http://www.bandcexpress.co.uk/sprockets ... g-575.html

    Chain
    http://www.bandcexpress.co.uk/520apx-11 ... -gold.html


    Does anyone know where you stand on MOT's for this???

    Cheers

    Steve
     
  20. D41

    D41

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    Yep, - It's just a case of swapping out the parts - piece of cake!!
    Dunno about that chain...? Looks a bit cheap IMO
    I went with an RK XSO chain: http://www.rkexcelamerica.com/street_rk_chain.html

    Take a look around the web & you should be able to find a cheap chain breaker & rivet tool. And make sure you use a rivet-type connecting link - the universal C-clip links are a bit crap in my experience.

    MOT is gonna be fine...they're only interested in whether the chain is in good condition, adjusted correctly, etc.

    On reflection, -1 front/+1 rear might be a better compromise for you, Steve - search around a bit & find out what gearing others are using before you buy.
     

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