I was out in the mud yesterday and stopped because the bike felt like it had a rear wheel flat, it didn’t. Carried on riding and the back end was all over the place, I’m no stranger to riding in the mud, it was very odd feeling that made me stop several times, I was convinced I’d snapped a seat or chainstay as it was even happening when riding in a straight line.
I’ve checked over the bike and can’t find anything wrong, anyone got any ideas on what it may be? The only significant change I’ve made was adding around 20PSI to the shock before the ride all the bolts and so on seem OK.

Bike’s a Santa cruz Blur LT.

Sorry to state the obvious but axle tight? Rear wheel bearings ok?

checked your spoke tension?
hub bearings free of play?
axle/skewer done up tight and properly?

QR was tight
Haven’t checked hub bearings so that’s a start, will check tensions too, any other ideas? Could too much shock pressure change the handling to this extent do you think?

Last times for me it was a broken rear axle, a loose crank and a buckled wheel (mostly vertical rather than side to side). Not all at once obvs

Could be the QR, Shimano may well be best, but they do eventually fail and when they do they still feel fine and tight, but the axle is barely held in (the QR binds on itself).

My money is on a snapped axle or even a cracked hub.

Well I didn’t have anything on tonight so out with the tools!

Cracked frame?

Stand to side of bike. One hand on top tube, other hand on top of back tyre. Try to move the wheel side to side, any play will be evident.

Let 20psi out and see if it goes back to feeling ok again?

That’s on the list wwas!

I’m going with spoke tension.

I’m going with a frame crack you haven’t seen.

Have had this, crack was not at a weld, so I didn’t see it when I looked.

It is doing it on harder surfaces too, I assume?

You are sure it’s not a puncture?

Tyre pressure? Too much in the back / not enough in the front?

I had this on a ride once, was just a slippery type of mud, loose layer on the surface over a harder layer, I was convinced I had a flat and kept stopping to check.

Nothing at all wrong with the bike.

I vote for loose spokes too

Another vote for wrong type of mud 😀

The nut between the seat and the bars.

Had this round Llandegla once, was continuously checking the rear wheel but all was fine.

AS ABOVE SNAPPED REAR AXLE

Snapped axle gets my vote too, the through axle held it together but random rear wheel steering was unpleasant.

I’m going with a front wheel problem. No really, had similar riding home and was convinced I had a rear flat as bike was all over the place. Stopped, checked rear pressure – absolutely fine. Carried on . . . looked down . . . front tyre flat as a pancake 😳 😆

None of the above I’m afraid, will try dropping pressure next. Maybe it was the wrong mud!

😀

I’m baffled 😐

Well I didn’t have anything on tonight so out with the tools!

That sounds an unsafe system of work to me. At least put on an apron?

Just to rule it out, it’s not got an old fashioned 26 wheel has it? 😉

Drunk?

Worn bearings where the swing arm attaches to the frame.

I had a similar feeling on my Covert for day or two till I found it by checking everything else very carefully. (several times)

Felt wobbly when riding, but the bearings had only a tiny bit of play, but its exaggerated by the time it gets to the wheel.