Rear Wheel Buzz

I’ve recently bought a new bike and constantly get buzzed on the butt by the rear tyre. This has never been an issue until now.

The bike I’m coming from had 130r/140f travel and 29” wheels, with a reach of 445 and a stack on 616 and I never experienced the issue once.

The bike I’m riding now is 160r/160f as a 29” with 443 reach and 620 stack so very similar numbers.

I appreciate that most people will immediately assume poor form and I won’t deny that my form could be better but having never had this before to now getting it all the time there must be something I’m not understanding.

I’ll admit that I don’t think I’ve got my suspension fully dialled in yet so I’ll work that first though it’s not a million miles from where it needs to be as it is.

I also suspect that running a large 2.6” tyre up front might not be helping so I’ll get that changed to see if it makes any difference.

Are there any other practical things I can do to alleviate the issue beyond waiting for my neanderthal brain to catch up with me.

Buzzed on the what now?
Depends if you’re pert or hanging. Ahem.

What are the axle paths of the two bikes? Even if the same… the rear wheel is now moving further…

@kelvin hm ok I mean they are definitely different, I don’t know anything about the subject to say which is which though. I’m coming from a YT Izzo (Blaze in size Medium) to a Cotic RocketMax (Gen 3 in size small)

oh I see what you mean, the rear wheel moves more given the greater travel, makes sense!

How low does your dropper go? On this bike and the last?

I keep finishing steep sections with skid marks inside and out. The seatpost insertion depth on my frame doesn’t allow me to fully insert the seatpost. If I could, I could run at least another 50mm of drop.

Having the saddle those 2 inches higher and the general shape of the frame means that to avoid the saddle hitting me in the arse, I have to get further back than I’d like. This means the wheel hits me in the arse rather than the saddle. I’m not sure which is worse…

@bens that’s actually a really good point and not something I’d thought of. I might see if I can lower the post and see if makes any difference

Different chainstay length and BB height plays a factor, lower bar height and longer stem could be a fix to put you more over the front

To anybody reading this that may be interested, I’ve managed to solve this with shorter cranks. At 5ft8 I’ve gone from 170mm to 155mm and my riding position feels so much better and never had this problem again since though it’s still early days.

Interesting. Did you raise your bar to maintain your forward lean angle?

I don’t understand how shorter cranks helps. Surely you have level pedals when in a position where you could get buzzed so you’re no higher or lower your feet are just a bit closer together? What am I missing?

@reeksy I stumbled in to this solution of shortening my cranks to try and resolve some mild knee pain so this surprised me too. I definitely feel more upright on the bike now and so far not a single instance of the buzz. I suppose if you think about the fact that with my pedals level my feet are 30cm closer together I must be standing taller.

I did wonder if that is what happened. I’m surprised it makes such a difference but glad it worked out.