Advice needed re Carbon Fiber vs Shocks

Question

I am an occasional rider who bought my last bike 15 years ago (an all-aluminium Saracen with shocks). I've put about 400-500 miles this year and am thinking of taking up one of the Cycle to Work schemes to get a new bike.

So I remember when I went from my steel, fully-rigid Diamond Back, to my Saracen. "Wow!" is the only way I remember the luxury of getting shocks. I plan to do 20 miles a day (90% road / 10% off-road) for commuting, and have been advised to get a carbon fibre cyclocross bike. But no cross bikes seem to have shocks, and, despite what I've been told, I just cannot believe that carbon frame & forks can offer the same amount of shock absorbtion as shocks.

There's much BS floating around about the wonders of carbon fibre, and while I would like a light bike, by the time I've added lights, mudguards, and a trip computer for road use, saving a few ounces here and there seems a bit silly.

The gearing of the bike I am thinking of (Planet X XLS Shimano 105 Cyclocross) seems perfect, with a top gear of 46/11t on 700c wheels. My biggest complaint about my Saracen is the lack of a really long gear for the roads, but the lack of shocks on the Planet X really does worry me. As an aside, I am most definitely not Mr. Super-fit, being 5 1/2 decades young, and with the weight problems (85-90Kg) that go with being such a spring chicken.

So does anybody have some real empiric evidence that CF forks are as good as Shocks for the use I have in mind or is there just too much marketing BS out there to form a firm opinion ?

Any sound advice would be appreciated !

Answer 1

There's no frame material in the world that will absorb bumps like a bike with a suspension fork/frame.

However, the original "suspension" invention that made bicycles practical was the pneumatic tire. If you have a rigid frame and fork, that's all the real suspension you have.

Skinny road tires at high psi have about 2-3mm of "travel", a fat commuter tire at 60 psi will have close to 25mm of travel. A suspension fork generally has about 100mm of travel.

A CX bike is a good choice to build a commuter around since they generally take fatter tires ( usually up to 32mm ), but there's absolutely no reason to get a carbon CX bike for commuting. Especially one that does not take a rack or have fender mounts.

With fat tires at the correct PSI, I think you would have a very hard time distinguishing between different frame materials in a blind test. Geometry and tire size make so much more of a difference than what the frame is made of.

To enjoy your commute, I'd recommend finding a balance in the middle. A bike with suspension is going to be heavy and slow and overkill 99% of the time. A "racy" carbon CX bike is going to be fast, but rough and the handling will be a bit twitchy. A good commuter should take fat tires(32mm at least), have a relatively long wheelbase and slacker angles.

But you can commute on anything. You might just try putting slicks on the bike you already have and see how that works for you. If you are going to get a new bike, I'd really suggest looking at CX/commuter bikes with disk brakes.

Answer 2

I think it is a matter of personal preference.

I had an aluminium race bike with carbon forks (CELL - Australian) which I used as a commuter, and for the occasional race or climb at home in Colorado.

I was curious about the carbon forks and was told that they are not as stiff as normal forks and on long IronMan rides, this makes a massive difference to how tired your body gets (again this is dependent on the quality of the riding surface). However for this to be a factor you need to be riding 160km+

My other bike was given to me about 10+ years ago, it is a stiff GIANT Boulder. The original front suspension fork was replaced by a stiff fork by the guy who gave it to me. I used the bike for commuting with slick tyres, while I was in Sydney and changed to off-road tyres when I did a mountain bike ride, however without a fork my hands invariably were bleeding after any offroad ride.

When we moved to Colorado, the bleeding hands became more prevalent and people were laughing at me during long mountain descents - saying I was crazy. I bought a cheap $100 suspension fork, fitted it, and I love it.

Because the tyres are off road tyres and it has a fork on it I almost never use the GIANT as a commuter while the CELL gets a good work out.

I think for commuting a stiff or CF fork will always be superior.

Answer 3

You generally don't see bikes sold with drops and suspension (but people do build them). Cross bikes are rigid (though in amateur cross, some people will bring in mountain bikes). Suspension forks are only useful on the road for people who have back problems or are old or something which necessitates the need for a light use front suspension fork to iron out some more bumps. Most people are best served by putting on bigger tires and a less aggressive setup on a rigid bike. Depending on the quality of your rigid diamondback and if you still have it, you may want to try fitting it with some fat, smooth tires or tires like the Geax Evolution (marketed as slight dirt use but primarily road use) and try taking it out again. 400-500 miles isn't a lot either (20-25 days of commuting), so I'm guessing theres also the getting used to riding around thing - a bike isn't like lying in bed. You can also play with saddles and grips and get a bike fit for comfort - that will probably matter more than your fork type.

According to their website, Planet X markets the XLS as a "Stiff, responsive race-ready cyclocross machine" and its listed as non-mudflap and non pannier rack compatible. Those aren't characteristics of a good commuter. A carbon fiber fork helps on some bikes in killing buzzing sensations, but its not going to change the purpose of a bike. Some cyclocross bikes do make good commuters, but they aren't typically cyclocross bikes marketed as race machines -- moreso things like the Trek Crossrip (some race-ish bikes do work as commuters though, like Kona's Jake the Snake). Its usually clear from the component spec, geometry and what not if its intended to race or to commute on. I was looking at the Planet X Kaffenback 2 for a while personally which looked to be a better commuter (but they weren't responsive to my questions and it would have been an international order).

Unless you have back problems or something which necessitates the use of shocks, I think a bike which takes non-skinny tires and has a more relaxed geometry is a good place to go with or without a carbon fork (this should only serve as relatively minor differentiation). If you want drops, look at something like the old Kona Dew Drop, but for 10 miles each way, a flat bar hybrid would work for most people as well, like the Trek 7.3 FX. Take them out for a spin on similar terrain to the commute and see what you like. People can, should and still do commute on rigid bikes. If you really feel like you need front suspension after trying out some hybrids (like the Trek 7.3fx, which does fine on light offroad stuff like fire roads) or drop bar commuters (Kona Dew Drop or Trek Crossrip (even though its marketed as a cross bike, its really not a race machine)) or even some touring bikes like the Trek 520 (which has a very nice geometry), go for a hybrid with front suspension, like the Trek 8.3 ds, though I'm not sure how much bounce there will be for someone whose 90kg. Good old rigid mountain bikes are also fine for 10 miles with good tires (like an old Specialized Rockhopper/Hardrock), and they're cheap and discrete (so they make ideal commuters) which can do a bit of fun.

Answer 4

Carbon fibre frames and forks don't have the same amount of travel (shock absorbing capability) as shocks. I had to dig up to get some evidence and from an old Trek Madone brochure I found some vertical compliance numbers, which were based on 2007 models:

• Scott Addict, ~0.3 inch
• Orbea Orca, ~0.4 inch
• Specialized Roubaix SL, ~0.5 inch
• Specialized Tarmac SL and Trek Madone ~0.6 inch

Furthermore, on Trek website, they say their Trek Domane has at least twice the compliance of other bikes, on the generous side that would be 1.3 inch using their own data. That's only 33 mm of travel.

That said, maybe watching Paris-Roubaix video can convince you either way, either you think they're crazy or that road bikes are not too bad in that kind of awful condition.

Btw, carbon bikes are not only lighter, they also look good ;)

Answer 5

I don't know about where everyone lives but where I live roads have a lot of potholes and debris, especially along the edges of a certain four lane state route. I have a Schwinn GTX 2.0 700c with aluminum frame, 32mm tires, front suspension, and seatpost suspension. I switched to the 32mm tires from the original 37 mm for a faster ride and added a suspension seatpost form my Schwinn Network 3.0 for comfort. The first bike I had was a steel rigid fork which seemed to absorb jolts better than later aluminum frame bikes without front fork suspension I had. So it is nice to have the front fork suspension and suspension seatpost when you run over some unexpected piece of gravel, twig, etc. I try to maintain about 15 mph and totally rigid frame gives a lot of jarring in the hands and buttocks areas!

Answer 6

For 90% road carbon

Shocks plus:
- More travel
Shocks minus:
- Heavy
- Absorb pedal energy
- Wear out

Carbon fork plus:
- Light
- Comfortable
Carbon fork minus:
- Small travel

I ride carbon frame and carbon fork mountain bike with low pressure tubeless.