180mm minimum?
Definitely, or you will almost certainly die...
183/160 same as on my 26" bikes. I weigh 16.5 stone and can't say I've had any issue.
Is my thinking flawed here? Is rotor size more to do with weight of rider/bike than size of wheel?
Yes.
Shame it's too late to edit!
Yes and no. To have exactly the same lever feel on a 29er as a 26" bike you do need larger rotors but since brakes now are plenty powerful it's not really an issue. Basically if you were running 160/140 on a 26" bike would power really be an issue?
Larger rotors are good for long dh runs where overheating may be a problem but in this there's no real difference between 29er and 26
Clubber - no. Think about it.
No, you think about it 😉
I have done thanks 😡
Ditto 😉
i see your point, the larger wheel size would increase the effective lever that you are using to covert your change forward momentum into a moment. Also larger disk=larger braking moment for the same leaver force so you should use a disk 1.11 times bigger to get the same braking for the same leaver pressure.
1.11=29/26=156/140=178/160=200/180
Make sense?
It's about energy, which is the same at the same speed (bar minor increase in wheel inertia)
The rotor on a 29er will be rotating slower than on a 26er (since the wheels are larger) for the same bike velocity.
Power = Force x Velocity
The force depends on the brake materials and how hard you are squeezing the brake pads onto the rotor.
The velocity at the pad comes down to the rotor diameter and how fast it's rotating.
So, if you want to get rid of excess kinetic energy at the same rate on your 29'er as on your 26'er, you want a bigger rotor.
you need to convert the energy in to a force diagram to work out effects of disk size. What equation are you using to go direct from momentum loss to pressure on a brake lever?
Absolutely which is what my comment about heat dissipation is about.
Of course, being bigger, a 29er wheel turns slower for the same ground speed compared to a 26" bike. Using the same size rotor and calliper means having to brake harder ( more force ). Energy being force x distance and distance being lower on the 29er for the reason above.
Still so sure, Al?
I thought you were right all along, thanks for doing the work for me 8)
One for the cynic-al FAIL thread? 😉
my fuel ex came with 185mm front and rear, my scandal had 160mm front and rear - swapped the rear 185mm onto the front of the scandal and shoved the 160mm on the trek to even things out - perfect 🙂
clubber - Member
One for the cynic-al FAIL thread?
Post it up if you like.
Only kidding Al, not one for that sort of pettiness.
Why not? It's a laugh.
160mm f&r and 17.5stn on a ridged on-one and using Hayes sole brakes 8)
Feel free to post it yourself Al...
It's not about self promotion.