Aluminum Frame VS. Steel Frame Questions

C

Catfisher

Member
Hi All,

I have read that steel frames are definately recommended for the gas engine kits because the forks are much stronger than aluminum forks. Does this also hold true for a rear wheel electric hub motor build?

If I end up building an electric that I plan to pedal a lot to assist, it seems that an aluminum bike will be easier to manually pedal. Also, the only steel frames I see are like entry level Schwinn, Murray, ect. at Wally World. I hear these bikes don't hold up well with heavy use, say 5 or 6 days a week. I've seen some better built steel bikes, but they all seem to be beach cruisers or 3 speed hub shifters. I have some steep hills to negotiate, and I would like a wider range of gears.

I weigh about 200 lbs, plus the hub motor and batteries.

Any and all recommendations are appreciated.

.flg.
 
I think the aluminum bikes are much like the steel ones in that they're no better or worse strength wise, provided care is taken when picking one out - it's really the same problems you'd encounter with any inexpensive bike and that's quality of components & welds. I've an all aluminum Schwinn with an in frame 2 stroke that has about 5000 miles on it with absolutely no signs of fatigue (commuter) - the main difference with aluminum is care must be taken - don't drill holes in key structural areas and be wary of chafe.

TBH - if I were to build an electric, I'd defo go aluminum as "every ounce counts" with any build, it's even more true with the limitations of electrics. My 66cc aluminum Schwinn demonstrates this quite well as it's competitive against my 66cc vintage steel cruiser even though the old cruiser has a shiftkit and the Schwinn does not.

While the Schwinn isn't top quality (it's only a $200 bike) I think it's only the bargain aluminum bikes going for about $100 or so that'd be cause for concern - and honestly I don't think the steel ones in that price range would be much better, both share similar weaknesses - namely welds and low quality rims.

Most aluminum bikes make up for potential weak points with added gusseting & larger diameter tubing, a nightmare for an in-frame engine (like mine was lol) but no problem for a hub drive electric :D
 

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i just scored a 97 canondale m1 i think. its aluminum and cant wait to set it up and do some cool videos at my friends dirt track serious competitive racin goin on there every friday footage to come
 
I would base my decision on the overall quality of the bike, not the frame material. If your buy a Huffy, schwinn (unless its an old one), Magna, Road Master, Murray etc. it will not hold up regardless of frame material. Buy a better quality bike, even if you have to buy used. Usually, you cant go wrong with any brand that sold in a real bike shop. Ive been a bike mechanic for six years and I cant tell you how many of those walmart bikes ive seen break. Frames, wheels, components, you name it, they are all crap! (In my opinion anyway, sorry if I offended anybody)
 
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I have 2 Free Spirits (make of bike is unsure) and they have lasted 5 years and 6 years and ride them at least 3 times a week each at 45 MPH and have not had any problems with them at all with durability. One was $ 20 and the other was 25 (used of coarse) I work 6 days a week and alternate between these two bikes. the other 3 that I own I hardly ride and they are high quality bikes, 2 TREX's and a Specialized, I love my bikes.r.ly.
 
Either material is great if used right in a somewhat quality built bike. My preference in general would be aluminum as 9 outta the last 10 bikes I've owned were aluminum framed. Front forks, unless they are suspension type are normally made of steel. You won't find very many rigid forks (if any) these days made out of aluminum....it's not a good application for them.

Out of the last 9 aluminum framed bikes I've used and raced, only one of them has cracked and in a usual place on the downtube, near the head tube. As a kid, that's where all my frames would break....steel or aluminum, I just loved to catch air....big air back then!

Aluminum is light and gives a resilient ride when done right, a feel all it's own.
 
The roads here are so bad I would NOT trust an aluminium frame bike .
They are usually very cheap here.
Every one here wants a multispeed steel mens bike , just like ME
 
i've ridden 3 aluminum bikes with 2strokes on them (none of them mine) and they all vibrated a lot.

my steel bikes hardly vibrate at all.

i can't be certain if it's because of the aluminum or not, since i didn't build them, but it makes me think they vibrate more.
 
bairdco said:
i've ridden 3 aluminum bikes with 2strokes on them (none of them mine) and they all vibrated a lot.

my steel bikes hardly vibrate at all.

i can't be certain if it's because of the aluminum or not, since i didn't build them, but it makes me think they vibrate more.
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Aluminum doesn't transmit or cause anymore vibration than steel.....if anything, it would dampen vibration more being a softer material in most cases. Lead is a good example of a soft dampening metal and a heavy one at that.

My bikes don't vibrate at all and they're aluminum.....with 4-stroke engines. A good combination if ya ask melaff
 
The issues with vibration are moot when it comes to electric bikes. Having ridden an overpowered electric bike (wilderness Energy bl36 running 48volts, approx 28-30 mph on flat) for the last 2 years I'm unconvinced either material makes much difference. The most important thing is that the wheel drop outs are strong enough. So as long as thats the case you should be good to go. Rear drop outs on most bikes should be strong enough in either aluminum or steel. But to make yourself safe its best to get a good solid torque arm.

Remember the axle on an electric hub motor is essentially an oversized threaded shaft thats been ground flat on 2 sides. These flat sides are what lock the motor in the drop out and believe me they cause a lot of torque. I'm on my third fork (front hub motor) and have been on it for a year and a half. Thats not to say the previous two forks were worse but I had no torque arm. Once you hit the throttle an immense amount of torque is created and it can and does spread the drop outs out. On a fork thats nothing but a replacement but on a frame, its get a new bike time. Once I added a torque arm its been bullet proof.

Some people make their own from a wrench and a hose clamp, others custom machine them. I used a torque arm from ampedbikes.com great design. Thick steel and adjustable insert. And at $25 bucks to save your frame its worth every penny.

Hub motors are an ingenius design but they can be troublesome if the proper precautions aren't taken. I learned the hard way.

Any other questions let me know.
 
My beach cruiser frame is aluminum, but the forks are rigid and steel. The top tube is almost 2 1/2" and the down tube is 1 1/2" so I don't feel like it's weak.

This being my first MB I can only speculate about why, but vibration levels on my 48cc are very low up to 7000 rpm. My guess is that my front hocky puck motor mount helps a lot with vibration, and being 48cc is probably a plus too.

If I have a choice between light weight and strong, or heavy and strong, I'll take light everytime (except for my fat ass).
 
biknut said:
My beach cruiser frame is aluminum, but the forks are rigid and steel. The top tube is almost 2 1/2" and the down tube is 1 1/2" so I don't feel like it's weak.

This being my first MB I can only speculate about why, but vibration levels on my 48cc are very low up to 7000 rpm. My guess is that my front hocky puck motor mount helps a lot with vibration, and being 48cc is probably a plus too.

If I have a choice between light weight and strong, or heavy and strong, I'll take light everytime (except for my fat ass).
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My Schwinn Point Beach Cruiser did good for a year..then came the hi-po mods..It does 48MPH---50 + downhill,,lol. ..Then one day I just happen to look and seen three rear frame cracks in the aluminum frame. I welded them up and added some extra weld..So far so good..P.S. always use a double bracket front fender..Crashing sucks .duh.
 
motorhead419 said:
My Schwinn Point Beach Cruiser did good for a year..then came the hi-po mods..It does 48MPH---50 + downhill,,lol. ..Then one day I just happen to look and seen three rear frame cracks in the aluminum frame. I welded them up and added some extra weld..So far so good..P.S. always use a double bracket front fender..Crashing sucks .duh.
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I'm pretty sure any bicycle is going to have a short lifespan at those speeds lol.
 
I've been using the aluminum GT frames for years now building gasoline bikes I never had any problem I have been building electric bikes with the same frame and a 5000 watt motor and a 72 volt 35 amp hour battery this bike will do 70 miles an hour aluminum frame hi power motor without spinning out in the Dropout and no cracks no problems whatsoever if you're worried about any kind of strength in your Dropout all you got to do is notch some quarter inch plate steel screw that on the outside of your dropouts and you will never have a motor spin out or any problem and with using these aluminum gas bike frames for electric bikes you get too poor gin and juice out of your gas tank LOL
 

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Norman H said:
I've been using the aluminum GT frames for years now building gasoline bikes I never had any problem I have been building electric bikes with the same frame and a 5000 watt motor and a 72 volt 35 amp hour battery this bike will do 70 miles an hour aluminum frame hi power motor without spinning out in the Dropout and no cracks no problems whatsoever if you're worried about any kind of strength in your Dropout all you got to do is notch some quarter inch plate steel screw that on the outside of your dropouts and you will never have a motor spin out or any problem and with using these aluminum gas bike frames for electric bikes you get too poor gin and juice out of your gas tank LOL
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Many will argue aluminum can be just as sturdy as steel; I do agree for the most part with this. However my preference is for steel but not for how sturdy it is. The reason I prefer steel is because it is so much easier and economical to weld on. One can buy a mig or arc welder fairly cheap; less than $150. A tig welder on the other hand isn't cheap.
 
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