djpfine

How much durability am I sacrificing by going from 725 to Spirit?

I'm looking for my first steel frame, and of course would like something light and stiff. However, I've read a lot about Spirit being too thin and fragile - I already have a CF frame to take care of that . The two bikes I'm looking at have the same geometry and about a ~1.3lb weight difference between them.

Are there any other pros/cons I should be considering?

Andrew R Stewart 

1.3 pounds... Do you poop before you ride? Carry a full wallet? Andy

GrayJay

Assuming two steel bikes with equal tube diameters and that the weight difference is just due to tube thickness, the heavier frame would be stiffer. Too light of a steel bike and/or with too small diameter of tubes will be a flexible noodle.

reddog3

If the bike has been designed properly with regard to the materials used, rider weight and intended usage- probably no sacrifice in durability.

You didn't provide quite enough info though. 1.3# is a huge difference in frame weight in a good quality steel frame which should come in at 3 to 3 1/2, maybe 4 pounds. There is some obvious difference- like maybe one is lugged and the other isn't? Check wall thickness too. I can tell you this... compare frame weights with main tubes of .7mm-.5mm, with ones of .9mm-.8mm, and there ain't 1.3 pounds difference unless the frame is "really" huge. LOL

You probably need to do a little homework. Weight? 1.3# is significant in the frame alone. A full third heavier (assuming the lighter one is 3#). At the end of the day? Nothing. You could take either frame and depending on your component choice and build a bike that weighs in at 15-16 pounds if you're a weight weenie. If your not and don't want to spend the buck on light weight components then the difference is even less meaningful.


Like Andy says... take a dump before you leave home.

djpfine

Interesting...I thought that the thinner walls alone would have made the Spirit tubing much easier to dent. The other frame in 725 also had lugs, which is likely why there's a ~1.3lbs difference. That's also just a ballpark figure. My main concern was durability and how much I really sacrifice between the two different tubings.

unterhausen

I assume you are talking about the shaped Spirit, which is about as light as anyone would consider for making a steel frame. I've considered, but never talked myself into using that tubing. My Spirit for Lugs bike has taken a very severe shot without bending and has no dents. I know people have brazed the shaped spirit, but it's probably more suitable for TIG.

MassiveD

If you move from .6mm to .5mm I think the heavier material is 44% more dent resistant, but dents are not the only measure of durability. With high end gear probably not the main one. If you change the tubing section it gets more complicated to calculate, but I would think the dentability factor gets worse on larger tubes. Maybe like 10%.

on 24 inches of 1.25 tubing that reduction would save you about 1.7 ounces of frame weight. You are basically saving a foil like piece the thickness of a sheet of paper.

mudboy

The last frame I built was from Spirit for Lugs. It's pretty tough stuff. I wouldn't play the drums on the top tube with a pedal wrench, but so long as you're not abusing your bike, it will be fine.