do shift kits make you go faster?

Discussion in 'Performance Mods' started by happyjourney, Jun 26, 2011.

  1. happyjourney

    happyjourney Member

    I know they deal with hills better but due to the fact that there are so few teeth on the smallest rear sprocket does that equate to faster top speeds?

  2. MikeJ

    MikeJ Member

    Top speed is the Holy Grail among a lot of people. Top speed is limited by incline of the road, how much wind resistance you encounter, altitude, and the displacement of the engine. When the torque out of the engine equals the resistance of these four factors, your speed goes no faster, regardless of the number of teeth utilized in the rear sprocket.

    Like a four-wheel vehicle, with a downhill, strong tail wind, or big engine, you can go faster in higher gears. In lower gears, the engine becomes the resistance. You have seen big trucks go down long inclines (well, maybe not in Florida). In Colorado, engine braking is mandatory to avoid runaway trucks. (Lets see.... a 9,000 gallon gasoline tanker with no engine brake nor friction brakes doing 120 mph equals.... a lot of excitement.)

    There are all kinds of fun comments from some writers how fast their bicycle went, like one who claimed 65mph (while it was strapped to the back of his pickup truck on the interstate.)
  3. Skyliner70cc

    Skyliner70cc Active Member

    They can make you go faster but my shifter kit allows me to climb any hill that Colorado Springs has to offer and I am geared to max out at 25mph in 7th gear.
  4. mbatl

    mbatl Member

    In my experience with my ht shift kit bike, yes top speed is much higher. I have yet to go wot in 6th gear until it stops accelerating. It just feels toooo fast for an old huffy style bike. I think a Hawaii member does 50mph on his!

    The biggest advantage is hill climbing and a lower cruising rpm that draws less attention and vibrations on the unbalanced ht.

    What speed do you feel is ideal for you?
  5. 5-7HEAVEN

    5-7HEAVEN Active Member

    The smallest sprocket is like overdrive. Mine is 12:1, which is like a 29-tooth rear sprocket for Happy Time engines.

    My first gear is 37.09:1, akin to an 89-tooth rear sprocket for HT.

    Second gear is 28.36:1, like a 68-tooth sprocket.

    Acceleration is very quick, which gets you to the same top speed as a single 29-tooth sprocket, only faster.

    JMO, there are very few engines with 76mm clutches or Happy Time engines which can produce enough torque to make use of 12:1 gearing.
  6. Ivan H

    Ivan H New Member

    Hi guys, my expeariance with a shift kit is that they do give a little more speed, but not heaps. These motors just aint got enough torque. I have 66cc mild port widening/ramping, rocksolid head, sbp chamber, vm 16 mikuni, homemade cdi (thankyou Jaguar), sbp jackshaft & shimano hyperglide 32(?) thru to 11 & I use 11 tooth of the jackshaft for less angle of the chain. The motor has 4 & 1/2 tanks of fuel thru it since I put all new bearings except big end & piston & rings so it'll loosen up more yet, but I can get 67kph max at the moment, til I hit a headwind or incline. And that aint maintained speed. I use 6th of 8 gears as top. Cheers
  7. Pablo

    Pablo Motored Bikes Sponsor

    The others have answered quite well and it's a question we get all the time.

    Just throwing a shifter kit on does not mean your top speed will automatically increase. For example, if your engine is running poorly before, it certainly won't improve with a shifter kit. If your engine is running well and you have a small bolt on sprocket with gears higher than than your bike sprockets, then you PROBABLY* won't have a higher top speed, but you will certainly accelerate much faster.

    It bears repeating - there is a LOT more to speed than just a small rear gear!

    *even here it depends - if a lower gears gets your engine into the power band, then you could go faster!
  8. Skyliner70cc

    Skyliner70cc Active Member

    A shift kit makes my bike MUCH faster going uphill! As for straightaways, I'm a little slower then folks who run small single speed sprockets in the rear.

    My riding is mostly on dirt trails with some hills so a shift kit is a lifesaver.
  9. jaguar

    jaguar Well-Known Member

    question- Why doesn't any of the successful motorized bicycle racers have it on their bikes? Are they just dumb? NO. More sprockets/bearings/chain means more resistance to forward motion. They select the gearing they need for the track they will race at and just go with it.
    The advantage for us non-racers is being able to climb hills better and achieve a good top speed. I myself don't need it because my motor is maximized in every way and it achieves a good power range without the crutch of a shift kit. But if you need it then buy it!
  10. Skyliner70cc

    Skyliner70cc Active Member

    A shifter kit is not a crutch and while you probably didn't mean to be insulting, it can be taken that way.

    There is no way even your maxmized machine would be able to climb steep hills up to 12,000 feet and cruise comfortably 25 mph on flat terrain at 6600 feet. Yes, I road my MB climbing from 8000 feet (Almont, CO) feet to 12,000 onto the top of Cottonwood pass. I fell just shy of the summit of the pass when my freewheel failed. It was my fault, my standard freewheel was acting up for a while and I didn't have the desire to replace it with my HD once just yet.

    For racing, i agree...a single speed in its simplicity is probably best.
  11. Pablo

    Pablo Motored Bikes Sponsor

    Not sure "crutch" is a good word choice. Heck just buy a Ferrari with a single speed if you don't need a crutch :whistling:. I do agree that, of course, turning a jackshaft does rob power. No doubt about that - but as far as why the few races so far not many riders even use shifter kits is because they don't really need them. Relatively flat course, ability to keep it WFO, and a single start. Given a rider who can properly select gears, some hills and really deep curves, it might be a different story.

    Besides the electric motors leave the gas engines in such an arena. I wonder why? :grin5:
  12. Ivan H

    Ivan H New Member

    Well said Pablo. It stands to reason a jackshaft adds resistance but the ability to select ratios to better suit variations in riding conditions I wouldnt call a crutch. Its something thats incorporated into most all forms of automotive vehicless. Cheers
  13. LR Jerry

    LR Jerry Well-Known Member

    I use the Staton Inc crank kit on my Land Rider auto shift bike. On the crank 28, 34 and 42. I use a twist shift to change the crank gears. The wheel gears are 28-14, 7 speed which shift automatically. This is my setup: 28 uphill 7+ mph, 34 level ground 30 mph and 42 downhill 45+ mph. Robin Subaru EHO 35, 18.75:1 gearbox. Gearbox to crank 17:44.
    Last edited: Apr 23, 2012
  14. KCvale

    KCvale Motorized Bicycle Vendor


    Do shift kits make you go faster?
    They do if you have the motor for it.

    Do shift kits make your overall riding experience better?
    Absolutely, and in every case, even with a bone stock 48cc.

    I've built and test rode a dozen, been riding a high performance 66cc with one for over a year, have another High Performance 66cc build in the shop and parts for my new 49cc 4-stroke 3-speed shifter personal ride on their way.

    In fact Paul (aka Pablo) and Jim over at Sick Bike Parts asked me last week if they could refer their callers wanting assembled shift kit bikes to me.
    That was friendly of them ;-}

    Here are some things to keep in mind if go shifter:

    It won't make you faster than the power you motor can make.

    If your motor can make 3HP you'll love gears and yes you can go faster if you have the bike for it.
    That means a GOOD bike, NOT a wally world Huffy.

    This was my personal ride for over a year before I sold it last week for $950 to try 4-stroke shifters next.


    It looks humble enough but that is a solid $500 3-speed Giant bike and 66cc Skyhawk with some performance enhancements.

    It always started easy on the 1st pedal, 0-25MPH in ~3 seconds, to 40MPH in 6 seconds and comfortable to ride at that speed.
    I tucked in and bent over and hit 45MPH but that was too fast for me, for the most part I rode around without the motor breaking a sweat at 35MPH.

    There are some cons however...

    If you don't have the tools, skills and patience to mate the kit to your motor and then to your bike perfectly you will have nothing but problems.
    These are hard core power transfer parts, there is no fudging precise alignment and zero room for loose things.

    They also add an extra chain and neither of the JS chains are easy to adjust, but a fix for that is actually in the works as I type.

    If you are mechanically inclined however the difference is night and day from a direct drive.

    The first thing you'll notice after you discover you don't have bike momentum to help you bump start it (it's all pedals to start the motor), is when you let off the gas your motor drops to idle but you continue to coast along with no drag because of your pedal sides hub freewheels.

    That also means you better make sure you have good brakes.

    I hope that helps.
  15. jeffuehrer

    jeffuehrer Member

    For me personally, less is more. I have everything stock with the exception of a chrome muffler, B6H spark plug, and pineapple sprocket mount. I am perfectly content at cruising the speed limit of 20mph. I have a 44 tooth sprocket so I can get going uphill pretty good too (26mph). Since my frame is cracked I won't push anything over 30mph. I have 878 miles on my 66cc of which 366 miles are with the crack in the frame. I was going to toss the frame out at the behest of concerned mbers but sure am glad I didn't.
  16. KCvale

    KCvale Motorized Bicycle Vendor

    Well, armor up when you ride because it's going to break the rest of the way and send you for an uncomfortable nap with Mr. Pavement, and no matter how fast you are going it won't be a pleasant nap.

    But hey, if you built it yourself with an Ebay BGF motor kit on a wally world Huffy for $300 power on, ride it 'till it finishes breaking and as you lay there on the road you can still think about how smart you were saving money.

    'Nuff said?
    I think so.
  17. jeffuehrer

    jeffuehrer Member

    Mr. Pavement and I are old pals. As far as the crack goes it is done cracking because I "sewed it up", permanently. The bike is a Raleigh, the motor came from BikeBerry, and as I'm riding it I think about what a great job I did saving it instead of throwing it away. You thought of me laying in the road, ouch. I live in love, not in fear. :tt1:
  18. KCvale

    KCvale Motorized Bicycle Vendor

    Well silly me, that's what I get for assuming.
    I haven't built on a Raleigh but my local bike store carries them, pricey but they look like really sturdy bikes, how the heck did you crack the frame?
    More specifically, where did it crack?

    I certainly do agree about repairing a bike like that, nice job ;-}

    I actually got a spiffy new (to me) repair/customize tool in recently, a buddy dropped of his 115V Mig welder with a couple of spools of rod and a full Argon gas bottle as he was out of storage room 'just in case' I could use it. AKA store it for him ;-}

    I don't know how to use it well yet but there is no such thing as too many good tools right?

    As for Mr. Pavement and I, we are blood brothers, literally.
    I address him as Mr. out of respect, and tread lightly on him.

    Don't get me wrong, I'm no scaredy pants riding, my normal cruising speed is 35-40MPH, I just do it on a high dollar solid bike and never without my new best friend, a 1200 lumen Lithium powered CREE flashing front light ESPECIALLY during daylight riding.

    If I have to visit Mr. P up close and personal again it won't because someone didn't see me coming unless they drive with a white cane out the drivers side window hehehe ;-}
  19. jeffuehrer

    jeffuehrer Member

    The frame is cracked on the down tube where the water bottle cage bottom hole is. I am guessing it cracked from having four engines mounted on it. (2 48cc, 2 66cc) Also it is an aluminum frame. I don't think you'll be saying nice job once you see what a mess I made of the frame. I had to come up with a frankenmount job to sustain the life of my old friend. No welding. With the bikes you build I probably wouldn't be afraid to push 50-60mph (fully geared up), they look pretty solid. For visibility I use a bright orange mesh and yellow tape reflective vest. My night light is 900 lumens and I also have a 120 decibel horn.

    Attached Files:

  20. KCvale

    KCvale Motorized Bicycle Vendor

    Bummer Jeff, but at least you are still mobile.

    I spoil myself on my personal ride until I'm ready for something else to try then move it on, used, but used and maintained by me.
    I am still having post pardom(sp?) depression from selling my last ride so I know what you mean about your bike Jeff hehehehe ;-}

    As for customer builds I have a set price to make a good bike, DD or shifter, without the bike. Then I encourage them to go to real bike store and avoid Big Box store bikes in the Toy section.
    I like Macargi bikes, they seem to be solid bikes for a reasonable price, especially the touch for ~$170 retail in the bike shop around the corner though I may have found a local source for 'just off the boat' boxes for much less, but not if you are under about 5'8" otherwise you feel cramped.

    The 'big boy' models like the Pantera are better, that frame isn't going to even bend let alone break, the SBP front Z mount helps as it gives you almost 360 degree round coverage. In the case of this build it's a shifter so it has a pair of rear mounts the same way.

    Just a thought for if and when your Frankinfix gives out ;-}

    As for the topic title I will repeat myself, yes, a variable gear range will let you go faster if you have the motor to push against the wind and a bike that can take it.