Why did my last trip give me a bum blister? I don't do a lot of MTB tracks, but there's a team event coming up soon and I'm doing some flat single-track to prepare.

After two 15 km laps I have a blister on my left butt-cheek, right at the top of the leg.  

I normally wear tight cycling pants with a pad made from coolmax (the orange stuff) with normal pants over the top. That is normally okay for road.  

Questions: Is there a difference between padded pants for MTB vs road cycling?   Why else would I be getting blisters when the same clothes on the road are fine for 80+ KM trips?


I'm using look road clips and road shoes, mostly because I already have them.
Its a 21" hard frame - no front or rear suspension.  I suppose you'd call it a hybrid or commuter frame.
Saddle is a relatively thinly-padded Giant brand that is mounted flat.


No, I'll not post a picture of my injury.
I worked it out - its the cleats and riding a MTB trail that caused my blister.

Hows that?  I noticed today that when there's a mound or little crest, I've been locking up my legs and the rear wheel gets lifted up by the cleats.  When I'm off the saddle, sitting back down drives the chamois pad downwards.

The fix was to wear a belt with my bike pants to hold them up, or to take them in a bit next time the sewing machine is set up.   Or buy a smaller size.  Or wear normal pants over the top of the padded biking pants.