Are tyres responsible for FireBlades's juddering?

Published: 07 October 2010

Q. I have a problem with my 1995 Fireblade. When I brake heavily I get violent front end judder. I do track days and it is making it unrideable.

The discs and pads are new, discs run true and are parallel. There is no play in the headstock, wheel bearings or forks. The damping is set up for me.

The only thing I have changed are the tyres and I have had this problem since they were fitted.
Jeff, email
 
A. If you think it is the tyres, you need to check both of them for the following:
Are the correct road pressures being used? 36psi front, 42psi rear.

For track day pressures try cold inflation pressures of 31psi front and rear on a 16inch front-wheeled Blade. But as with all track day pressures you may need to tweak them to your preferences from this base setting.

Are the tyres fitted in the correct direction? i.e. following the direction arrows on the sidewalls.

Are the tyres seated on the rims correctly? Use the concentric rings that are on the tyres' sidewall at the top of the bead area as a guide. They must be perfectly concentric with the wheel with no dips behind the wheel's rim edge at all.

Have the tyres been balanced correctly? And we mean both tyres. For some reason some riders think that balancing the rear isn't necessary.

Have the tyres been fitted with the yellow dots placed adjacent to the valves? The yellow dots indicated the lightest point of the tyre and in order to reduce the amount of balance weights needed should be positioned by the heaviest point of the wheel, which is the valve.

Is there any lateral or vertical run-out in the tyres? You really need to get the wheels out and place them on a static wheel balancer and use a simple fixed pointer or a dial gauge to check for this.

With the manufacturing quality of tyres these days this is highly unlikely but it's always worth checking for.

While you are checking for all of those things you should inspect your wheels for damage and dents. Use the pointer/dial gauge to check for wheel run-out as well.

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