flipflop

Since you guys are the best I know... here's a question I've been pondering!

With the increasing gas prices I'm seriously considering a moped for longer range transportation. A tomos targa LX to be exact. They weigh in around 80lbs stock, and will be modifyed as much as possible in pursuit of high speeds and "weight weenie-dom."

I'm wondering what you guys think about running bike tires at 35-50 mph for extended periods of time. They work fine on road bikes on the down hills... but the majority of the time they are going less than 20mph. Will they roll of the rims if turns are taken at motorcycle speeds? Will the suspension fork/swing arm prevent a taco at speed if it finds a pot hole?

I'm thinking that the lower rolling resistance and lighter rim would require less horsepower than the normal steel wheel. Deep V rims for strength, high spoke count, laced to disc brake hubs. I'm pondering running a bike chain instead of a moped type chain to save some rotating weight, but it may not be able to take the horsepower. (I don't want to machine a custom sproket... )

Thanks guys..

Michigander

Keeping in mind that high speeds are often obtained for 8 miles down a mountain road, I'd say the tires should be fine, but as with all bike tires check them for wear every now and then.

About the chain, don't use a bike chain. Motors have far more torque output than your legs, and you would quickly snap it.

ZachS

how to make your moped as light and efficient as possible:

take out the motor.

EvilV

Higher speed increases exponentially the stress on a tyre and the chances of losing grip on the road. Engineers carefully calculate the traction capabilities and strength required for particular applications and design accordingly. I think it would be a recipe for failure or even disaster to use a bike tyre on a motorised cycle like you are proposing. Travelling at 50 mph on a bike tyre driven by an engine, when the tyre was designed for human propulsion strikes me as ridiculous. The comparison made above with a cyclist running downhill neglects the fact that the moped is not being dragged to 50 mph by gravity, but by a petrol engine passing stresses through the thin cover they were never designed for. A strong cyclist might put a hundred watts opf power through a tyre, while a moped probably puts out seven to ten times that effort. Take a look at the sidewalls and tread on a moped tyre and then look at the paper thin walls of your cycle tyre. There's a hell of a difference, and that difference is designed in to meet the stresses and not just an example of lazy over design.

Michigander

I'll put it this way. I have an 80cc Kings motor which currently resides on a Nishiki touring bike with MTB handlebars. It does 40 MPH or so, and I have no tire blow outs or even have an accident to speak of. Think of it this way; wear a helmet, and if **** happens, you'll know better next time.

EvilV

I wonder how many miles you've ridden with this arrangement. Designers of road vehicles and bicycles plan for failures and consider numbers of vehicles being used in various circumstances for high mileages. Yes, keep wearing that helmet; you may need it someday.

Eatadonut

So what's the difference between him riding at 50mph under motor power and me riding at 48mph under gravity power? A strong cyclist puts more than 100 watts down.

Moped tires are thicker because if you told moped riders that 2000 miles was an acceptable life expectancy for tires, they'd freak.

flipflop

Thats what I was figuring. Bikes don't have the extra power to spare to push the extra rolling resistance of a tire that goes 20k...

DigitalQuirk

One issue that immediately springs to mind is brakes. A moped, with an engine and tank of gas, is a lot more mass to stop. Your side-pull calipers probably aren't going to cut it. Another issue is traction. Chances are good that a bicycle tire will be very apt to spin while accelerating. Then there's stability. A bump or pothole with the force of the weight of a bike behind it going 30 MPH can be hairy enough; at 50 MPH, with the weight of the moped, it will probably get destroyed. Then there's the fact that the tire wasn't designed to handle all that weight in the first place, so it will probably warp in very short time.

Personally, I'd go with a harder rubber compound with a smooth tread for maximum fuel economy on a moped; you'd be a lot further ahead.

AverageCommuter

You don't need to go with bicycle tires to get more speed out of your moped. Check out https://www.project76puch.com/index.html

EvilV

Rubbish!

The moped engine will put out at least seven times the power a human can muster, and will do it for hour after hour while the person will soon tire, even at a hundred watts. How often do you ride at 48 miles an hour, and for how long? Then there's the fact that driving a moped at the speed you mention means putting down over a kilowatt of power through a thin walled bike tyre, when it was designed for less than a tenth of that. While under your gravity example, the thing is simply rolling down hill until you apply the brakes when torque will be applied to the sidewalls.

Anyway - go ahead. Natural selection is a fine thing. It's very good for the species.

EvilV

Very good advice. All sound points there. I actually had a motorcyle front tyre blow out on me once when I hit a bad pothole at only thrity miles an hour. It was a very unfunny experience having no control at all. The damned thing changed lanes and threw me off into the road. I don't take liberties with tyres now.

flipflop

Thanks guys.

Been doing some thinking... I don't think I want to be digging into a corner on skinny road tires. The contact patch is so limited by the width. Lose any pressure and you are on the rim.

Been doing some reading about the chains... Looks like 415 and 420 are the sizes they run. Essentially just track chain!

But, the most interesting thing I've come across is a discussion that talks about installing a Shimano Nexus hub on a moped. Get two transmissions, one of which you can control. Set the final drive ratio for what ever you are trying to do! Essentially an Overdrive/underdrive on a moped...

Eatadonut

I'm not arguing that the combustion engine will win in a race. I'm arguing because you're quoting 100 watts as some incredible number. Tires were not designed for 100 watts, or racers would be destroying them left and right. Tires are designed for at LEAST 400 watts, since they can be expected to see that regularly in a good race. And that's if we're just counting sustained effort. How much power do your brakes put down?

ElJamoquio

Mopeds have much less torque than my legs do. That's not why the chain breaks.

ElJamoquio

Although I agree with your overall point, I don't do so as emphatically.

Today I averaged 250 watts on my ride. And I'm not a strong cyclist. But that's only 1/3 of a horsepower. I imagine these mopeds put out somewhere in the neighborhood of three-five horsepower to go down the road.

ElJamoquio

NOOOOOOOOOOOO!!!!!! Don't do it. The nexus hub isn't the most durable under human power. Although I've already mentioned the humans put out more torque than mopeds; after the gear reduction of the chain, the torque on the hub will be much more.

lz4005

There is no way you are going to make a Tomos moped perform any better by cobbling bike parts onto it. They aren't well made to begin with. That is why they are so inexpensive.

Talk to a wrench at your LSS (local scooter shop), chances are they'll know all the tricks for making the various models they sell go faster and/or more efficiently. With aftermarket parts designed to do just that.

A few years ago I had a Kymco People 50. After taking off some factory restrictions and replacing the exhaust and transmission belt it would go 53 mph. Not bad for a 49.5cc engine. The guy at the shop had one with every possible aftermarket part (minus the nitrous kit) and could get close to 80.

flipflop

I'm definetly aware that when it comes to mopeds you are just taking a slow piece of junk and making it a slightly faster piece of junk...

Thanks for the comments guys.

Would a sturmey archer be a better choice for the hub? I think its a neat idea!

Andreasaway

The Tomos has a major drawback im my opinion. I have worked on scooters for many years and know the tomos quite well, they are horrible. Let me explain, the tomos has a two speed transmission so unlike most scooters it has a hard time staying in the powerband. To make matters worse the two speed tranny is flawed, once it has upshifted it will not downshift again till you are nearly stopped. This major flaw makes the bike unsuited to use in hilly areas. If you are infact planning on using a scooter to save money on fuel, first consider a bike, then a four stroke scooter. I have found that a Honda aircooled 50cc is the best. They ones to look for are cubs on as they were known later passports. They can be tuned to high heaven and come in a 70cc and a 90cc for a little more go, also the motors will last longer and you won't have the on going expense of two stroke oil on top of at least 50% higher fuel consumtion. Just my two bits
P.S. I ran a conti 26" slick on the front of a scooter for awhile it worked ok, but not as well as before.

geebee

If you want play around to get max. performance min. weight etc. why not put a small four stroke on a bike and then you can tweak till your hearts content, I would think you would get amazing fuel economy on a well tweaked setup much better than a mopeds as the bike will be much lighter and more efficient in basic design, but I would stick to a top speed of probaly 35 mph continuos and don't use a friction drive.
Re: the bike tyres on a moped most of the replies forgot to take into account the mass of the moped if you do the maths the stress increase at speed due to the extra weight would be frightening.

kemmer

You'd probably be ok with a bike tire/rim on the front. What the other guy said about brakes is true though. The stock drum probably has more stopping power than a bike disc. Just tune it, the factory set ups are not the fastest/most efficient.

Knudsen

j/k

flipflop

True enough!

Mos6502

I wouldn't use bike wheels at all. I've been riding mopeds for years, and the tires are already too small for the weight they're carrying - switch to bicycle wheels and tires - and good luck going around any corner or stopping when it's wet out. If you want to make the moped faster, ditch the moped and get a real motorcycle.