Rear wheel skidding out

jon1981

Hey,

I've had a couple of scary fish tailing moments on the road bike when braking at 50kph or so coming into corners. I'm applying both brakes evenly but i'm losing the back wheel. The bike was recently serviced, wheels perfectly true and the tyres are gp4000s with about 600km on them running them at 105PSI on Zondas. I weigh about 73KG.

I'm ruling out the bike and assuming my technique is the issue, any advice people can give me here?

J

lennymc

brake less with the rear brake and put your weight over the rear wheel.

smacl

From my limited experience a skid on the back wheel is due to it locking or braking on surface without much grip. This could be technique, but could also be due to the brakes being badly balanced, i.e. the same amount of pressure on each brake lever is producing more braking on the back than front wheel. I found this was the case on my disc brakes until I spent a fair amount of time getting them setup as I like them, no real issues since. On rim brakes it could happen if you've more wear on your front pads than rear ones, or slightly lower cable tension. I'll leave it to those more knowledgeable than me on proper braking technique, I just go with brake before you get into the corner and don't brake when you're actually in the corner.

nordicb

Are you sure it skids? It's so abrupt it's nearly impossible to stay upright when this happens.

General rule is to shift your weight to the back, move rearwards (how much is by feel really), go on drops, outer pedal down, foot pressure on outer pedal. Brake before corners, not in the corners...

07Lapierre

Buzwaldo

When you brake, your weight is thrown forwards on the bike, leaving very little weight going down through the rear end. This unloading of the rear wheel makes it very easy to skid. As said, brake mostly with the front and shift weight backwards.
Had a similar scary moment at speed in a sportive a few years back. Rear end fishtailed and looked like I was heading over a low wall. Releasing brakes sorted it out. Got a fright alright, but not nearly as much as the guys right behind me who thought I was going to be the start of a pile-up.

Beasty

My suggestion - slow down. You should be at your cornering speed before you start turning. If you don't have issues coming up to a "stop/yield" junction there's no reason to have them approaching a bend/corner

jon1981

Thanks for all the replies, alot to consider there. I guess a better way of described is the wheel will whip left and right (fish tailing I guess), complete loss of traction. Perhaps my weight is too far forward as someone noted, I'll definitely look into that.

Is there a way of checking the brake is applying too much pressure on one side of the rim vs the other?

07Lapierre

A long shot, but check your wheel rim. if the rim is damaged, it could be catching under heavy braking. I'm not talking about a buckled wheel. i'm talking about one side of the rim being very slightly bent (possibly from an impact with a pothole/cats eye). Under light braking, you might feel a slight "tug".

ford2600

http://road.cc/content/feature/180830-how-choose-your-tyre-pressure-%E2%80%94-balancing-speed-comfort-and-grip

Your weight including bike is about 80kg, with a 55:45 split you will get away with lower pressure on rear and certainly on front.

If you have 2017 Zonda's they have a wider rim allowing even lower pressure.

My combined weight is about 95kg and with wide 19mm internal rims and 28mm tyres I'm getting away with 65psi on front and 75psi on year, and sometimes a lot less. In 13k km I've had no pinch flats or puncture.

Unless you are like Tommy here and ride a lot of good surfaces, no real downside to it for a leisure rider
https://www.youtube.com/watch?v=0ocWVgmkUSk

All My Stars Aligned

My cornering improved dramatically after been told as well as shifting my weight slightly back also press into the outer pedal (the one at 6 o'clock). This really improved rear traction. Also you have far greater control of the break leavers when in the drops. Ultimately though it's about getting your speed right before you enter the turn.