Originally Posted by
GlennR
Not really true.
They use different carbon fiber, a different layup and different curing. So while the geometry is the same the frames are very different.
Most of the weight savings is that higher cost frames use a aerospace carbon fiber that's stronger so you can use less of it.There are places my bike that if you press your thumb it can see it flex. On the lower lever it's hard like a rock. If you tap on the frames the higher sound thinner.
Frames that use higher modulus CF have it strategically in places to maximize stiffness while minimizing weight. All frames using high modulus CF also use a mix of lower modulus CF, otherwise the frame would crack immediately on the first bump encountered. When Specialized says their S-Works frame uses FACT 12r, they're just saying some of the frame contains that material. They don't reveal the mix of CF they use, which is why there is no definitive proof that the lower-priced 10r-advertised frames aren't using the same layup and just end up heavier after the curing process. When people have been weighing their Tarmac SL7 frames and noticing that the non-S-Works are within striking distance or sometimes even lighter with a lighter paint job, the difference has naturally been questioned. Both S-Works and second-tier frames contain FACT 10r, after all.
In any case, if a more expensive and lighter frame indeed contains more higher modulus CF, it's likely to be stiffer but less compliant than it's lower-tier equivalent given that there's less material used to absorb road vibration. Whether that trade-off is meaningful depends on the rider, just like whether the 10s or 100ish grams difference and added stiffness are.