# Frame material for heavy riders?



## Wormburner (Feb 11, 2005)

I've also posted this in the Niner forum, but thought it might be better served here. Anyway, here's hoping for some help on a question that I am having a hard time wrapping my head around:

I am 6'2" and ~240 lbs. I am currently on a Fisher 29er, and have been considering making the switch to a sir9. It seems reasonable (to me, at least) that a steel frame would be stronger and thus better suited for a heavier rider. However, when I was discussing this with a local wrench, they suggested sticking with aluminum because the steel frame would have too much flex and that the aluminum would be a smoother ride for someone of my size. 

Is this is sound logic? Is it just a psychological thing for me, envisioning an aluminum frame as a thin-walled beer can vs. a steel frame being strong simply because steel sounds toughter? 

I know the best thing to do would be to try both and see for myself, but that seems unlikely in the near future. Any thoughts?


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## Ken in KC (Jan 12, 2004)

*Frame Materials 101*



Wormburner said:


> I've also posted this in the Niner forum, but thought it might be better served here. Anyway, here's hoping for some help on a question that I am having a hard time wrapping my head around:
> 
> I am 6'2" and ~240 lbs. I am currently on a Fisher 29er, and have been considering making the switch to a sir9. It seems reasonable (to me, at least) that a steel frame would be stronger and thus better suited for a heavier rider. However, when I was discussing this with a local wrench, they suggested sticking with aluminum because the steel frame would have too much flex and that the aluminum would be a smoother ride for someone of my size.
> 
> ...


First, what your LBS told you makes no sense at all.

Frame materials and which is "better" is relative. Any frame material can exhibit any type of characteristic based on frame design and the expertise of the person building the frame.

In general terms, an Aluminium frame is stiff and light. But anyone who's ever ridden a pre-Trek Klien knows that they're stiff, buttery smooth and last a lifetime. On the other hand, anyone who's ever ridden a cheap Al bike knows that they're harsh and will tear you up until they eventually fail.

In general terms a steel frame is heavy and compliant. But anyone who's ever ridden a Badger 29er knows that they're super light weight, compliant but stiff in all the right places. On the other hand, anyone who's ever ridden a cheap steel bike knows they're clunky, heavy and flex all over the place.

In general terms, a Ti frame is light and flexy and generally not meant for Clydes. But anyone who's ever ridden a Matt Chester Ti bike knows they're light, stiff compliant all at the same time. On the other hand, a cheap Ti bike is like riding a soggy noodle down the trail.

Frame materials and which one is "better" is really based on where you get the bike. With all that said, I don't understand how a LBS can suggest that Al in general would be smoother than steel.

Ken


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## Wormburner (Feb 11, 2005)

Thanks for the reply. I guess that's more in line with what I thought. 

Certainly frame design can be a huge factor in how a bike "feels," but for sake of argument let's say that I'm considering the difference between a sir9 and an emd9, which I think have very similar designs (I didn't look to confirm this, just using it as an example).

What I had not considered before is the possibility that the "feel" of a steel frame is designed for a lighter rider, so a bigger rider having more weight on the bike could induce more flex than intended. Now take a similarly-designed aluminum frame that feels stiff to the same lighter rider: would a heavier rider cause slightly more flex on the aluminum and experience a ride more similar to what the lighter rider had on the steel frame?

I know that there are too many variables unaccounted for, but this is something I hadn't thought about before. I'm not saying I believe it, but it got me thinking about if I had had it all wrong in my head.


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## Jefe74 (Mar 1, 2006)

The reason Al frames are stiff is because Al has crappy fatigue properties. If you let it flex, it will break. Steel has better a fatigue life, and Ti is the best (for fatigue), which is why a Ti frame can be built nice and compliant and still hold up. Theoreticaly, carbon can be made to be stiffer in some directions, and compliant in others, but don't take that as a recommendation for carbon for a clyde.

Also, any good frame builder will adjust the stiffness of the frame with the size. So an XL should weigh more than a L by more that just the extra few inches of tubing used. Since you are 6'2", likely you would be looking at a big frame anyway.

I would recommend writing the companies you are interested in and asking them what weight rider and flex characteristics that their frames are designed for.

- J


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## Wormburner (Feb 11, 2005)

Thanks for the advce. I'll give that a try.


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## socallush (Dec 3, 2005)

*steel flex*

I have both, and your shop mechanic is right. The BB will flex on pedal strokes. I have a steel SS and road bike. The movement annoys me on the road bike, but is less on a larger tubed MTB frame. The steel frame rides nicer through the bumps than my Al hard tail.


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## Soupboy (Jan 13, 2004)

6'3", 260# SSer's bike. Stiff yet compliant. It's all in the hands of the builder. All steel (mostly, if not all, Zona). Right around 24lbs with 100% clyde-authorized bits.


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## jgsatl (Sep 16, 2006)

man i keep eyeballing those cane creek seat posts. but i'm always afraid i'll just bob up and down when pedaling (i'm 255 nekkid).

yours working out ok?


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## Oaken (Apr 18, 2004)

Steel is so much better. The only way I would go Alum is if it was a Ventana.


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