Have not, but looks dangerous because it's narrow. I saw one biker one time, he was fine, but doesn't look happy (going eastbound). I was worried for him.
I recommend you taking it West only as that seems to be mainly down hill, plus you're away from the mountain side most of the time, which blocks drivers from seeing you. On your return route (going East) take, Brea Cyn Rd North - Diamond Bar Blvd North- Grand East. -Watch out for Grand its one killer hill! I love it!
I've done it a few times. Not as bad as you think. It is tight in some spots. I live in Brea and do a 40+ mile loop using Brea Cyn to Diamond Bar Blvd. to Grand Av. to Chino Hills Pkwy. to the 142(Carbon Cyn.). I think that Brea Cyn. is worse than Carbon Cyn. IMO. I also have a hammer ride I can't seem to get very many people to with on. Using Fullerton Rd., Hacienda Rd. with the 40+ mile loop added. It tends to hammer the legs pretty well. Total distance is around 60 miles!
What part of Brea Cyn are you talking about? The only section I consider a little "iffy" is the stretch below Diamond Bar Bl, going past Tonner Cyn. I did a ride connecting San Bernardino and Fullerton, going through Claremont and Pomona, then up Diamond Bar to Pathfinder, jogging west to Brea Cyn, and then down through Brea and into Fullerton. I'm just glad I did Diamond Bar Bl. rather than taking Brea Cyn south from Golden Springs, because that would have finished me right there.
We've done that route as one of our shop rides out from Diamond Bar Cyclery on the corner of Diamond Bar Blvd and Grand. I haven't been on the bike as much since I took over the shop but we do have a Sat ride at 0730 that I'm trying to get going and we'll ride that loop.
I did this ride a few weeks ago looking for some miles with some hills and it was perfect for that. There were 5 climbs total (see link, I started in claremont)...
I loved the workout but I won't ride this route again:
as you see in the link by the folks who described the ride route, traffic is listed as heavy... I didn't find the traffic too bad except that the drivers are just plain idiots, completely oblivious of a cyclist on these roads... I've ridden in areas with much heavier traffic in the east coast, even in other places I lived in souther california. Since this is just ONE of many amazing rides in the region, I'm opting to stay away from carbon canyon.
I drove Carbon Canyon Rd many times when I lived in Chino Hills but never rode it. The shoulder is small in many spots and with all of the curves there are too many places that cars could clip you. I would only ride it with a large group.
If you ride during traffic time, it seems safer to ride from chino to brea side, since you are riding away from the sunrise and that drivers are not blinded by the sun. Plus it is also safer because you ride up the "curvy" part uphill where speeds are slower and you aren't riding downhill at the same speeds as the cars if you went from brea to carbon canyon (if this makes any sense).
I've done it both ways, but the guy who told me that the chino to brea was safer, i tend to agree.
The first time I rode Carbon Canyon was in 1973 on a Schwinn Continental. Not much traffic then, and most roads in Berdoo county were rough and narrow, washouts and detours were commonplace. On riding this stretch today I would tend to agree that westbound on CC would be a fun downhill blast and going east uphill in traffic would invite real danger. Area from here to SA River burned in 2009 or so and is mainly known for mountain biking, centered on the trails in Chino Hills State Park.
Since my first ride there, the area has developed into suburbs and the area has lots of main arterial roads which are wide & in good condition. Many streets have dedicated bike lanes so there is no shortage of roadie routes. I don't live there but sometimes travel to the Jenson USA store in Corona. I like to get there from LA by Metrolink to Montclair, south on Central to the tangle of old dairy farm roads that eventually cross the Santa Ana River and a glimpse of almost wild riparian land. Then over a short ways to the West Corona Metrolink and the Jenson shop nearby at the 91 freeway (this leg is nearly all downhill). I then return either via train or down the S.A. canyon bike trail to Yorba Linda, then haul west on Imperial Hwy. to the Norwalk station of the Green Line. Ordinarily I only do this ride during the IE breathing season of Oct. thru May. Have fun.
Footnote: I notice there are group rides in Marin county which advertise a CHP escort on the narrow roads going to the coast. This is all done as an organized ride, at extra cost and by appointment etc., but soCal road riders are mostly left to the luck of the draw with regard to safety, as any review of PCH and related coastal area bike vs. car accidents will show.
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