ASK MBACTION – Is Aluminum Stronger than Carbon?


Q: I ride a 2012 Stumpy hardtail and love it, but I’m starting to look at new bikes. I’m 260 pounds. Are carbon frames able to stand up to that weight, or are newer aluminum frames a better choice? Also, can rear suspension support me or is that pushing the limits?

—Rob, who wants to mash some pedals on a new bike

A: We’ve actually seen fewer cracks and failures with carbon bikes than with aluminum ones. A carbon frame should have no problem with your weight so long as you don’t go for a super-light XC bike that has a specified weight limit. As for the suspension, you should be careful which design you go with. Look for one that has a low-leverage ratio to start with. Leverage ratio is the amount of travel divided by the amount of stroke the shock uses. The lower the leverage ratio, the better it will support your weight, because you will be putting less force into the shock. Foes prides itself on low-leverage bikes. As an example, its Mixer has 150 millimeters of travel with a 64-millimeter stroke shock, therefore the leverage ratio is 2.34 to 1. Anything under a 2.5-to-1 ratio should work well for you.


Q: I am considering upgrading the wheelset on my 2014 Norco Sight. I am 48 years old, weigh 220 pounds and ride a mix of technical XC and steep trail/all-mountain almost exclusively on Vancouver Island, British Columbia. I am considering a set of Heist 27.5-inch wheels. I am thinking about getting a 27 millimeter rim in back and a 30 millimeter up front. My questions are: Does it make sense to have a slightly narrower rear rim than in the front? Will this combo work? Is there any advantage to it? Will 30 millimeters be too slow on the lower-gradient XC?

—Kevin, who needs some new hoops

A: There absolutely are advantages to running a wider rim in the front. It exploits the wider-tire footprint that bigger rims offer and saves weight in the rear. Actually, several pro enduro riders use this setup on their race bikes. Since you have the oppor- tunity to try it, go for it. The wider front wheel will add a few grams, but it will likely be so minimal you won’t really notice, and the traction will certainly be better.

Our only advice would be not to go too crazy with the differential, like with a 40-millimeter front and 19-millimeter rear. That will give the bike an unbalanced feel. As long as the differential is only 5 or 10 millimeters, you will probably love the improvement in ride quality.


Q: It seems that cross-country bikes are getting heavier each year. Why is that? Is there something wrong with the wrecking crew’s scale?

—Michael, who wants a lighter bike already

A: It’s not really true that all XC bikes are getting heavier. In fact, we’d probably argue that you can build a lighter bike now than at any other time in mountain bike history. For example, Specialized just released the lightest frame it has ever made, and it’s not a road bike; it’s an XC hardtail. But, riders seem to want more trail-riding capabilities, even from their XC bikes. Things like higher-volume tires, wider rims, dropper posts, etc. really add up when you’re dealing with a bike that’s supposed to be light.

Have a question for the MBA crew? You can send your brain busters to [email protected].

“Ask MBA” peeve of the month:

Tire sealants that simply don’t work. There are several great choices out there, but recently we’ve discovered some others that don’t seal very well at all.


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