Sprockets 36T sprocket and heavy riders

FWIW - most of the custom sprockets that get ordered through us are 34T, 35T or 36Tor....I have sold a few 27T to flatlanders (they are going to give me some feedback on what they thing of them....they want to cruise at 30+ without screaming the engine)....As I recall MI is mostly flat so a slightly taller gear should be OK (I have family in Clinton TWP MI) ...

Andrew
 
Norm said:
I have been riding the same kit for a little over a month. I'm loving it! I'm about the same size as you. I think if you build the bike right you could approach 35mph. The sprocket is 56t. It's my understanding that the Grubee gearbox is designed for high-end speed and thus I think it matches pretty well with the 56T to give you well rounded performance.
Here's what I get out of it: when the clutch is dry it prefers to go into gear at about 7mph. Pick-up is great on a flat. It doesn't take long to break 30mph. I get a high frequency vibration at about 27mph. The vibe makes me a little uncomfortable but I feel like the engine tolerates it okay. On a slight down-grade I do reach 35mph when wide-open. On a steep downhill run it will rev pretty fast so I give it a lot of throttle at the top of the hill then I idle the motor at 25 or 30mph coasting to the bottom. Hill climbing is not as good as I expect from a 56T. I usually help a little (very little) if I have to climb a steep hill from a stop at the bottom. Again I attribute the lack of low end torque to the high gearing of the Grubee box.

I have debated getting a smaller sprocket so I could get to higher speed without that vibration but have decided the 56T suits the terrain I ride (lots of stop and go) just about perfect. If I were doing rural roads and long stop free runs I would want a smaller sprocket.

Hope this helps,

norm
Click to expand...

Firstly I'm talking only about frame mounted grubees with Huangshengs.
Well I found the 56 T sprocket useless on the flat and not that great on steep hills. 25 mph at full revs and full revs shortens the engine's life. 48T is bad on hills and some I have to avoid and others I have to work really hard on the pedals - I mean so hard it hurts. The top speed with 48T is 30 mph with no headwind. The 44T was a laugh on the flat - it hit 65 km\hr on a sheltered stretch of flat straight road but a day of that was enough to convince me to change it. It couldn't handle any hill at all and the cluch was really struggling.
Clutches will protest at higher speed the smaller the sprocket. 44T is a waste of time. On a hill you would have to pedal faster than 100 revolutions per minute just to stop the clutch chattering and that is not only imposible but the whole arrangement just doesn't work unless you live on the flat and engage the engine only at 28 mph or higher.
I tried the 56T for 3 days and preferred the 48T. The best sprocket would probably be 52T but I don't have that and after reading Norm's account above I will put the 56T back on and only take it off if the top speed really is too slow. 28 mph is fine for me if the bike will pull better on the uphill.
I get te opinion that the Honda\Grubee frame mounts definitely have a bit more oomph and I also get the opinion that the rack mount guys get more pulling power than the frame mount guys for reasons I can't understand. It seems pointless to discuss sprocket sizes for frame mounts and rack mounts on the same page. Also pointess if we are talking different wheel sizes. One other thing I forgot to mention is that the 56T was a real pain on a 26" wheel because the chain clearances are a nightmare both against the tyre and particularly against the chain stay.
That's on a Schwinn cruiser. I'll try it out again cos the wheel is all built ready with a 56T with a special long chain to fit it but I think I'll have to take it off again because of the clearance problems. Time will tell but thanks Norm I'll report back at the week-end.
 
Last edited by a moderator:
andyinchville1 said:
FWIW - most of the custom sprockets that get ordered through us are 34T, 35T or 36Tor....I have sold a few 27T to flatlanders (they are going to give me some feedback on what they thing of them....they want to cruise at 30+ without screaming the engine)....As I recall MI is mostly flat so a slightly taller gear should be OK (I have family in Clinton TWP MI) ...

Andrew
Click to expand...

I've built too many HT rigs to believe that a 70cc with a 27T would go anywhere except downhill. You could drill your baffles out and tweak the carb and install the boost bottle and put benzine in your fuel mix but the motor will not last more than 1000 kms and your ear drums slightly less. The best HT rig I ever built was a 70cc on a Giant 21" Cypress with thin 700C wheels. I drilled the baffles out a little bit and it cruised nicely at 37 km\hr for sustained distances and could get up steep hills as well. Sure it could go a good bit faster but the motor breaks. I really don't miss those motors and hate having to service the ones I built for people and feel obliged to help them with. The 4 stroke grubee is, for me, a much cheaper bike - better fuel consumption and much much cheaper to keep running. Bikes are my only transport and I no longer need 3 HTs to ensure one runs at any given time. Done 2000 kms now on the 4-stroke and never needed to get back on the HT except I use it to haul the shopping home on Saturdays cos it can pull hard up the steep hill home from the supermarket. They feel so slow after getting used to the 4-stroke and if the motors were reliable I would still love them. HTs to me were like having a violent spouse who beats you intermittently - after a couple of years you can't take anymore and you finally realise the love affair is well and truly dead!
 
Irish John said:
Firstly I'm talking only about frame mounted grubees with Huangshengs.
I'll report back at the week-end.
Click to expand...

Yup, you and me are on identical rigs. I am also using the schwinn cruiser (single speed). The chain clearance is the only thing that bothers me. I resorted to skewing the wheel slightly to the right to avoid the chain contacting with the tire. The tire contact is only superficial but it's still disconcerting. The best solution I think is a flat sprocket and or a more narrow tire (like 1.95 or so).

It sounds like you are having vastly different experience with the exact same configuration as me. I don't remember if you said how many miles you have on her. My performance was dissapointing as well until I put 200-300 miles on it then it seemed the power increased significantly. If you don't have that many miles I think you should stick with it a while longer. If you do have 200-300 miles I have to wonder if you have a deffective kit. Again I easily clear 30mph on a flat. And I climb steep hills with minimal assistance.

I changed my 18T chainring for a 22T which gave me much easier peddling. I recomend you do the same.

I just finished calculating my gas milage. I got 120mpg. And that's with jackrabbit starts and stops, lots of hills and throttle open full. I'm currently testing how it does under more conservative conditions.

I look forward to your next report.

norm
 

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