Bad DOMS right now, makes no sense?

Last big endurance ride 135 miles end February no issues, training program with endurance sessions, one interval session and one very hard 60 mile group ride every week. No issues.

Go riding real easy with an old friend Saturday, 65 miles has me in zone 1, for most of the ride, finished with an average heart rate of 102, about 4 hours on the bike and Sunday my legs hurt like hell, and still hurt today?

Makes no sense???

Anyways, I will stay off the bike until Wednesday, then do a few loosen up rides, doing Natural bridge GranFondo in VA coming Sunday, close to 100 miles.

Wish I understood this, but perhaps a sign of bad over-training?

This is normally the case with me, DOMS comes up for no apparent reason.

Thoughts, anyone?

Recovery, recovery, recovery.

Recovery.

Seriously. Be vigilant about rehydration and refueling. Take advantage of the glycogen window and replenish with a 3:1 carb/protein drink as soon as you can, find one that contains glutamine and BCAA's or add them to what you are drinking. Eat something later. Keep off your feet after a long ride. Stretch and roll every night if possible. Don't assume that you can skip this just because you feel good now, or the ride was "easy".

Sometimes "easy" long rides are harder on our muscles because we get lazy about cadence and do more grinding, and we shift positions less often. A faster ride will rely more on our aerobic system, we give the muscles a break by shifting hand positions (hip angle) or getting out of the saddle.

Thanks Racer Ex, we think we read our bodies right and then boom, we get the surprise. Forgot to mention, I am also trying to get weight down, about 6lbs in three weeks so far. Part of the problem.
You are right about the LSD (Long slow distance) one rides socially, drop cadence to the mid 70's and the muscles do a bit of stuff they are not used to.

carb / fuel depletion + dehydration, yep definite DOMS bait

I am no elite rider (in fact, I suck), but no matter how badly I abuse myself on the bike, I never get DOMS, just some aching that night and the expected degree of fatigue. However, a few extra lunges at the gym will stiffen me up like 12 hr road kill. I always figured this was related to the degree of micro-trauma, which I figured was low on the bike for mechanical reasons. Not true?

Agreed never DOMS from the bike, just fatigue. The gym will put me in a world of hurt for days with squats and lunges. Last week, I was toast for 3 days after 3 x 20 lunges and squats. Granted it was my first gym session in a month for my legs. My immune system literally ramps up to where I feel sick for day 2 and 3 when my legs get that sore. If I want to be intense on the bike in a training block leading up to a race, my body can not handle any proper lifting without having to skip some bike training.

I get toxic-feeling and irresistibly drowsy after multi-hour efforts on the road, but maybe I've never beat on myself bad enough in the gym to experience it. It is said that the immune mediators released during prolonged, hard, exercise have considerable overlap with the ones circulating in systemic illness, like flu. Somehow, they feel a lot better when you do it to yourself, instead of getting mauled by a virus. It's also interesting that that those same mediators are considered markers for badness in people with obesity, diabetes, heart failure, etc., but they just make us Übermenschen stronger.

For you guys who cannot get DOMS on the bike, go to the track and do a sprint tournament that includes one flying 200 meter and three match sprints against competition and you will have a problem riding your bike the next day due to quad muscle soreness.

In fact, in the 2012 masters track nationals in Trexlertown, I did the 500 meters, pursuit and team pursuit. The 500 was the first event and everything came together and I managed to podium. The next day my legs were sore and I sucked in the pursuit. It is always a matter of how hard one goes compared to a baseline that may generate muscle soreness.