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Post by scootnwinn on May 6, 2013 13:27:05 GMT -5
The tire's max pressure rating has nothing to do with the recommended pressure by the scooter manufacturer. PSI should vary at different loads, not to exceed the max pressure rating. Running the maximum pressure for all loads is similar to running your scooter at redline constantly because its rated for that... Ride on prodigit, I am sure you know more about your riding conditions than I do. Everyone else don't run max pressure unless you want to wonder why the steering feels vague and the scooter tends to perform poorly especially in turns.
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Post by prodigit on May 6, 2013 15:58:44 GMT -5
Well, my experience with those 3.5x10 tires, is the lower the pressure, the more wobbly the bike feels. Those tires NEED to be pumped hard!
40PSI max, 35PSI man. recommended. 38PSI is not that much higher. Usually when I pump it 35PSI, after 2 weeks they're at 29PSI, and the scoot barely reaches 40MPH; with wind against me it barely passes 35MPH.
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Post by floz on Jul 21, 2015 15:36:52 GMT -5
Laika, my ATM50 rat-rod project has the same tiny tires, and I can concur on pressure. If her tires are slack, she's not as much fun or as stable.
When I first bought Laika, I set at 35psig on both at first. After about 7 miles on the hot concrete, I rechecked and found 37 front, 38 rear. It rode like a dream. Gross weight is a factor too, I'm kind of big for a stock 50cc, at 240'ish lbs without gear. Add a toolkit, fuel, and my backpack, and we're probably close to overloaded from the start. Downhill on Spring Creek Parkway in Plano, Texas, I was doing every bit of 50mph, keeping pace with the crazy Plano car traffic, grinning like a loon.
Me, I'm a "how does it feel" kinda guy. Laika feels pretty good at 35psig cold front and rear. I did work on a fair number of these Chinese 50 and 150cc bikes when I was professionally turning wrenches. For average or larger-than-average adults, I wouldn't recommend less than 33psig front/rear on a ATM50 or similar 50cc Chinese bike.
Have you checked the twin nuts on the top of the upright behind your front fairing? They wiggled loose on mine shortly after I brought it home, and made it feel very unstable when cornering and when braking on the way to buy a stator the following day. One of my coworkers has told me his ATM50 did the same thing, and it startled him quite a bit before he figured out what was up, because everything looked fine until you go for a ride and push it a little, then it "feels" wrong.
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Post by jtron on Jul 22, 2015 13:55:07 GMT -5
My bike uses 130  10s and they are great on the upper end of their rating. My bike is stable at 60plus even on the little 10s |
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Post by pgs on Jul 22, 2015 15:16:27 GMT -5
i am more impressed that it was doing 60+mph never mind the tire pressure, i have never owned a 50 that has gone that fast, i am surprised the cvt or crank didn't explode had to be pushing close to 10,000 to 12,000 rpm's
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Post by bandito2 on Jul 22, 2015 15:21:56 GMT -5
something else that could cause the wobble feeling is the rubber mounts on the motor and shocks they are not that well made to start with That would have been my assessment as well along with tire pressure that was probably just a little too low. Spongy front shocks will contribute to the problem as well. I have a 10" scooter wheel and tire on my little single wheel trailer. One time coming back home from a camping trip, a guy was pointing to the rear of my scoot and signaled me to pull over. So I did. He said "The tire on your trailer is rubbing on something." When I looked, there was a very shiny stripe right down the center of the tire. What the ....?!!! I couldn't see where it was even touching anything. I was scratchin my head about that for a few seconds then it finally dawned on me. That little tire was spinning so fast that it was being slung out and rubbing on the aluminum diamond plate fender. I slowed to below 70 after that and no more rubbing. (though I'm sure it was still being slung out somewhat) |
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Post by ghcoe on Jul 22, 2015 21:16:01 GMT -5
The BWS 125, Zuma here, seems to be quite stable in fast corners. The step through is pretty short tight though so that may make a difference.
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Post by oldchopperguy on Jul 23, 2015 11:04:51 GMT -5
Whew, everything IS relative...
In my younger days, I rode a Go-Kart brand "Big Bear Scrambler" mini-bike on the highways. Approx. a 30" wheelbase, total weight of 45 pounds... and running on 5" alloy rims. I regularly took the little beast over 100 mph, pushed by an "animal" McCulloch kart motor. Through a lucky "fluke" I got it street-licensed and ran with the pre-55 mph speed limit traffic at 70 to mph.
Oh, Lord, we DID have MARVELOUS toys a half-century ago that would excite even the wildest crotch-rocket jockey today... And give liability attorneys cardiac arrest!!!
Here's an old ad for the original. It's powered by a West Bend motor...
upload image online
"Unstable" doesn't even BEGIN to describe the ride... It was "twitchy" beyond anything I could relate, but I did ride the freeways on it. Not SMART, but definitely FUN!
As for our "today" real scooters, regardless of displacement, I've found they not only differ in stability and pleasant "grooving" at speed but the tires do make a major difference.
My old Kymco 250 has 12" wheels (140/70/12 rear tire, and 120/70/12 front). It had new Kenda "J" rated (62 mph) tires when I got it. Those tires were NOT good at any speed on the heavy scooter. I replaced them with "P" rated tires (92 mph) and it was like riding a whole new scoot! The old Kymco will actually exceed 80 mph on a good day, on a flat road, and I often cruise a steady 70 mph on any day.
Now, gone are the "wonky" feelings associated with the old "J" rated tires. They not only felt shaky at their rated 62 mph, but exhibited a strange "shimmy" when decelerating even at 20-30 mph.
The new "P" rated tires (well-balanced) are totally smooth, stable and "sure-footed" from start up to  mph, and all the way back down again. In fact, the old 250 cruises slightly better at 70 mph than my old Harley bagger of the seventies.
My "P" rated tires are a mix of a Shinko up front, and a Michelin Power Pure in the rear. Done to have a factory whitewall up front, and a rear with a sidewall that could be painted, since NOBODY makes a 140/70/12 whitewall... But that's another story... The mix of tire types perform flawlessly.
Frame-flex, steering-geometry and such have major influence on high-speed stability, but tires also make a big difference. Many riders have installed tweaked 150's into their 50cc scoots with good results at highway speeds. Lots of factors are involved, but tires DO deserve a good "look-see" when exceeding 50cc speeds.
Whatever the speed, ride safe!
Leo in Texas
PS: Thinking back 50 years, I truly cannot recommend 100 mph on a mini-bike... LOL! |
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Post by rockynv on Jul 23, 2015 22:32:30 GMT -5
The pressure and top speed should be kept per the bike manufacturers specifications regardless of what the capacity or apparent capacity of any one component is estimated or hoped to be by the rider.
Thankfully the original poster did not encounter a destabilizing event that would have resulted in a crash however the law of averages will eventually catch up with you if exceed the design specs of the bike as a whole assembly with the potential for morbidity much higher the more you push things.
Note that recommended tire pressures are for the design speed and weight bearing capacity of the bikes suspension to ensure the tires don't start chattering on a rough road so you end up skipping off and to prevent over stressing the suspension with hard impacts transmitted more severely due to over inflated tires. How long before metal fatigue sets in or the swing arm bushings get over stressed and you have a failure is an unknown however it is greatly increased when you over inflate the tires past the bikes loading specifications.
Face it, most 50cc bikes are designed for a single 170 lb rider so inflating the tire for a larger person is only gong to give you a false sense of security and you really have not made the bike suitable for a rider who weighs more.
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10s and they are great on the upper end of their rating. My bike is stable at 60plus even on the little 10s
mph, and all the way back down again. In fact, the old 250 cruises slightly better at 70 mph than my old Harley bagger of the seventies.