Getting ready to throw down some dollars for a Felt. Common sense says that the steel frame is by far the more durable, however I see alot of you guys using aluminum frames. Why is that? Being a super noobie, I want to buy the most durable frame, engine, etc. Seeing as how I'm aiming for max power (considering a 9HP Morini), low maintenance. So, aluminum or steel?
Frame: Steel vs. Aluminum?
- Thread starter youknouno
- Start date
wheelbender6
Well-Known Member
A name brand aluminum frame is OK. I would still prefer a name brand steel bike for a 9hp engine.
bigbutterbean
Active Member
here is the deal with a morini. they dont just bolt on like a kit engine. they require fabrication, welding, and very good mechanical skills to install on a bicycle. If you dont have all of those, I dont recommend a morini for your first motorbike. a mountain bike with an ht engine (2 stroke) or a 4 stroke with a shift kit should give you a fair amount of performance. however, if you do have the skills and equipment necessary for a morini build, go for it. I just wouldnt recommend aluminum for a morini build. people have cracked steel frames with morini engines.
Good points. While I want to get to know an engine all together, I do plan on outsourcing the welds and so forth to a reputable place. Alas, I have decided to buy my frame (Felt MP), order a cheap china girl, learn it and later upgrade. I'll transfer the china to my g/f's huffy. (She won't know the difference
.) 
Also, a steel frame is in order. Unfortunately, my fellow Felt-zers have noted that those provide less space for an in tank frame. Totally bummed about that but hey.. anything for a Felt.
Thanks bender. I'm a little dismayed w/ the fact that an intank frame is a difficult to-do with the steel body but I've seen a pretty awesome behind the seat tank application. I think I'm going to run with that.
bigbutterbean
Active Member
I got a two gallon plastic yamaha tank from a parts guy for $15 a couple years ago. looks a little big on the bicycle, but holds 2 gallons if I want to fill it up. usually only put a gallon in at a time. plastic is good because it wont rust and develop leaks like a metal tank. some Felt frames have a hollow top tube that I believe a few forum members have adapted for an in frame tank, so you could look into that. the behind the seat tanks are quite expensive unless you want to build your own. If you want to find a used plastic tank, check ebay and craigslist for those.
bigbutterbean
Active Member
I would also like to give you a little more advice, but please dont get offended. I see a few people come to the forum that are new to the hobby, and they say I want to do this with my bike, and I want to do that. My advice is this: start simple. looking for a bigger or more stylish gas tank is fine, just dont get caught up in trying to take your kit right out of the box and doing a million different things. Get the kit, put it together, see how it runs and how the parts in the kit hold up, and go from there. Break the engine in, make adjustments as needed, and learn the ins and outs and quirks of your bike. the quality of some of the parts in the china kits is not always the best, and sometimes the parts seem fine at first and break in a month or two. some of it also depends on how well it is put together and how well it is maintained. I say this as one who started out in this hobby with very little mechanical knowledge and no experience, and one who went through a lot of trial and error with my first bike. again as a reminder, this is just some friendly advice. in the end, its up to you to decide how you want to approach building your first motorized bike. However you decide to approach it, I say good luck.
POPS
Member
BBB
Not to contradict you, as your advice is solid but
I remember somewhere in the way back machine,
there was sort of a preflight check list to make a HT
more solid per say.
Skid all the screws in the kit for good ones, The plug and
wire, The acorn nuts on the head and torque the nuts,
The carb seal etc. etc.
Anyone remember.
POP'S
Not to contradict you, as your advice is solid but
I remember somewhere in the way back machine,
there was sort of a preflight check list to make a HT
more solid per say.
Skid all the screws in the kit for good ones, The plug and
wire, The acorn nuts on the head and torque the nuts,
The carb seal etc. etc.
Anyone remember.
POP'S
bigbutterbean
Active Member
Sometimes, the hardware does need upgraded, I have never needed to upgrade mine, except for the bolt that holds my carb onto my intake. I just cut the acorn part off the headbolts. I havent replaced any other hardware in 3 years. I buy ngk plugs, but dont upgrade my wiring. I do check the headbolts every so often, but only with a socket wrench. I just keep going in an x pattern, tightening a little more each time.
bigbutterbean
Active Member
quality control is no better today than it was in '08, or probably any time before that. Personally, I prefer to only replace what I have to. If I find a part to be weak, faulty, or otherwise inadequate, I replace it. Other than that, I run 'em pretty much the way they come. reason being, some of the kits/engines actually do come with decent hardware. My current engine is a year old, and I havent upgraded any of the hardware. Some engines/kits do come with weak/faulty/inadequate hardware, and in that case, it will need to be replaced. in my case, it wasnt necessary.
POPS
Member
You'll be glad you went with the MP. Steel is obviously a lot easier to fab with, you can fix/strengthen it, it rides better, and is cooler IMO
. It also withstands vibrations better:I did a quick google search and here is some interesting thought on the two materials (not sure how accurate it is): http://lists.contesting.com/_towertalk/2001-03/msg00652.html
"...With aluminum, the yield strength gradually declines as the
material cycles, with no limit to the degradation. If
a piece of aluminum is vibrating, that represents hundreds of cycles per
second. It doesn't take very long to accumulate millions
of cycles... and eventually the material will fail with a load that it would
have withstood when new.
Steel, on the other hand, cycles differently. Its yield strength does
degrade, but asymptotically to a limited value."
To me this means that in the long run, steel is going to fatigue less than aluminum due to vibration... but I'm definitely no metal expert. Almost all motocross bikes sold today come with an aluminum frame, but they are designed for motorized use from the factory (duh!). Since bicycles are not designed for motorized use and any extra degree of safety is welcomed, I like steel. That being said, design/quality is more important than material used.
I came here to say just that, BE-tech. That's exactly why I will never own an aluminum bike. Had one for 3 years, and after riding a few times a week, it developed cracks at several points along the frame. Had to abandon it after that. My next roadie was steel... a ~40 year old steel Schwinn. =) Just get steel and don't worry about your frame =)
Also, referring to BBB's post as a newcomer to motorized bikes, it was really good to go through the first assembly really simply. Helped me understand a lot about these motors, and I have lots of ideas about the "perfect" build now, but it's all money and what I have is great for what I need right now. =) I have HD hubs, street tires, front disc brakes... but that's all I changed. Cheers!
Also, referring to BBB's post as a newcomer to motorized bikes, it was really good to go through the first assembly really simply. Helped me understand a lot about these motors, and I have lots of ideas about the "perfect" build now, but it's all money and what I have is great for what I need right now. =) I have HD hubs, street tires, front disc brakes... but that's all I changed. Cheers!
BarelyAWake
New Member
In this age old debate, I'd like to suggest that for our application that the following;
...has a lot more bearing on the subject than out of context "vibration cycle" studies (which also overlooks steel's higher flex rate) - and what suffices for quality & design, what's suitable for the long term effects varies from material to material and ofc application.
Just because it's aluminum doesn't mean it's "bad" just as just because it's steel doesn't mean it's "good" - this is a far too oversimplified view of a somewhat complex subject, one that's often compounded by builder inexperience.
Even "quality" is comparative when both design and application are included - for example even a premium road bike is not necessarily the best choice for the rigors of motorization as it's primary design goal is to be as ultra light weight as possible, many choppers and some cruisers compromise structural integrity for aesthetics and not even all "vintage" bikes can be relied on simply because they're vintage.
All too often folks judge a bicycle to motorize based only on two factors - price and style, thinking the catchphrase "steel is real" will suffice, which overlooks the fact that even steel comes in various grades and types. For example chromoly tends to be brittle and is very challenging to weld properly (more so than even aluminum tubing) so while it's "quality" it may not be the best choice for additional modification & fabrication. It should go without saying a budget mild steel bicycle with sloppy, undercut welds is far more a deathtrap than even a inexpensive but quality aluminum bicycle designed for abuse, one with the heavier beads and additional gusseting such as a mountain bike... and TBH welding/modifying aluminum isn't really all that difficult - it takes slightly more experience than mild steel to weld it well, but not much w/today's MIGs.
It's all about choosing the right tool for the job - and that choice needs to include more than simply budget, style & material bias.
I've both steel and aluminum motorized bicycles and TBH I've not really any greater preference for either material as they both have their advantages & disadvantages.... but after well over 15,000 miles riding both I can say aluminum is more subject to chafe damage (panniers/cables etc) while steel is corrosion prone and flexy, but as long as you've chosen a stout frame design with quality welds and you've built it properly I can assure you vibration rate is not a serious consideration in our application... but if you cut corners w/a sloppy, cheap build - even steel isn't going to be enough to save you
...has a lot more bearing on the subject than out of context "vibration cycle" studies (which also overlooks steel's higher flex rate) - and what suffices for quality & design, what's suitable for the long term effects varies from material to material and ofc application.
Just because it's aluminum doesn't mean it's "bad" just as just because it's steel doesn't mean it's "good" - this is a far too oversimplified view of a somewhat complex subject, one that's often compounded by builder inexperience.
Even "quality" is comparative when both design and application are included - for example even a premium road bike is not necessarily the best choice for the rigors of motorization as it's primary design goal is to be as ultra light weight as possible, many choppers and some cruisers compromise structural integrity for aesthetics and not even all "vintage" bikes can be relied on simply because they're vintage.
All too often folks judge a bicycle to motorize based only on two factors - price and style, thinking the catchphrase "steel is real" will suffice, which overlooks the fact that even steel comes in various grades and types. For example chromoly tends to be brittle and is very challenging to weld properly (more so than even aluminum tubing) so while it's "quality" it may not be the best choice for additional modification & fabrication. It should go without saying a budget mild steel bicycle with sloppy, undercut welds is far more a deathtrap than even a inexpensive but quality aluminum bicycle designed for abuse, one with the heavier beads and additional gusseting such as a mountain bike... and TBH welding/modifying aluminum isn't really all that difficult - it takes slightly more experience than mild steel to weld it well, but not much w/today's MIGs.
It's all about choosing the right tool for the job - and that choice needs to include more than simply budget, style & material bias.
I've both steel and aluminum motorized bicycles and TBH I've not really any greater preference for either material as they both have their advantages & disadvantages.... but after well over 15,000 miles riding both I can say aluminum is more subject to chafe damage (panniers/cables etc) while steel is corrosion prone and flexy, but as long as you've chosen a stout frame design with quality welds and you've built it properly I can assure you vibration rate is not a serious consideration in our application... but if you cut corners w/a sloppy, cheap build - even steel isn't going to be enough to save you
Last edited:
